48 results on '"Paul J. Reckwerdt"'
Search Results
2. A feasible method for clinical delivery verification and dose reconstruction in tomotherapy
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J. Smilowitz, Gustavo H. Olivera, Paul J. Reckwerdt, J M Kapatoes, Thomas Rockwell Mackie, and Kenneth J. Ruchala
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Male ,medicine.medical_specialty ,Databases, Factual ,Computer science ,medicine.medical_treatment ,Computed tomography ,Iterative reconstruction ,Imaging phantom ,Tomotherapy ,Dogs ,Prostate ,Nasopharynx ,Medical imaging ,medicine ,Animals ,Humans ,Dosimetry ,Medical physics ,Computer vision ,Image sensor ,Radiometry ,Models, Statistical ,medicine.diagnostic_test ,Phantoms, Imaging ,business.industry ,Detector ,General Medicine ,Radiation therapy ,medicine.anatomical_structure ,Drug delivery ,Artificial intelligence ,Radiotherapy, Conformal ,Tomography, X-Ray Computed ,business - Abstract
Delivery verification is the process in which the energy fluence delivered during a treatment is verified. This verified energy fluence can be used in conjunction with an image in the treatment position to reconstruct the full three-dimensional dose deposited. A method for delivery verification that utilizes a measured database of detector signal is described in this work. This database is a function of two parameters, radiological path-length and detector-to-phantom distance, both of which are computed from a CT image taken at the time of delivery. Such a database was generated and used to perform delivery verification and dose reconstruction. Two experiments were conducted: a simulated prostate delivery on an inhomogeneous abdominal phantom, and a nasopharyngeal delivery on a dog cadaver. For both cases, it was found that the verified fluence and dose results using the database approach agreed very well with those using previously developed and proven techniques. Delivery verification with a measured database and CT image at the time of treatment is an accurate procedure for tomotherapy. The database eliminates the need for any patient-specific, pre- or post-treatment measurements. Moreover, such an approach creates an opportunity for accurate, real-time delivery verification and dose reconstruction given fast image reconstruction and dose computation tools.
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- 2001
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3. Megavoltage CT image reconstruction during tomotherapy treatments
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Paul J. Reckwerdt, E A Schloesser, K.J. Ruchala, Gustavo H. Olivera, Thomas R. Mackie, and J M Kapatoes
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Models, Statistical ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Image quality ,Megavoltage ct ,business.industry ,medicine.medical_treatment ,Normalization (image processing) ,Dose-Response Relationship, Radiation ,Iterative reconstruction ,Tomotherapy ,Visualization ,Radiation therapy ,Dogs ,Image Processing, Computer-Assisted ,medicine ,Animals ,Humans ,Radiology, Nuclear Medicine and imaging ,In patient ,Tomography, X-Ray Computed ,Nuclear medicine ,business - Abstract
An integrated tomotherapy system allows for improved radiotherapy verification by enabling the collection of megavoltage computed tomography (MVCT) images before or after treatment delivery. In this investigation, the possibility of collecting MV tomographic data and reconstructing images during a tomotherapy treatment is examined. By overcoming difficulties with the normalization of modulated treatment data and with the incompleteness of treatment data, it is possible to use data collected during tomotherapeutic treatments for MVCT reconstruction. The benefits of these techniques include potential increases in patient throughput, reductions in imaging dose, visualization of the patient in the treatment position and improvements in image contrast.
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- 2000
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4. Iterative approaches to dose optimization in tomotherapy
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Paul J. Reckwerdt, Gustavo H. Olivera, Thomas R. Mackie, and David M. Shepard
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Mathematical optimization ,Radiotherapy ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Iterative method ,medicine.medical_treatment ,Stability (learning theory) ,Radiotherapy Dosage ,Inverse problem ,Tomotherapy ,Weighting ,Histogram ,medicine ,Computer Simulation ,Radiology, Nuclear Medicine and imaging ,Minification ,Sensitivity (control systems) ,Tomography ,Algorithm ,Algorithms ,Mathematics - Abstract
This paper will present the results of an investigation into three iterative approaches to inverse treatment planning. These techniques have been examined in the hope of developing an optimization algorithm suitable for the large-scale problems that are encountered in tomotherapy. The three iterative techniques are referred to as the ratio method, iterative least-squares minimization and the maximum-likelihood estimator. Our results indicate that each of these techniques can serve as a useful tool in tomotherapy optimization. As compared with other mathematical programming techniques, the iterative approaches can reduce both memory demands and time requirements. In this paper, the results from small- and large-scale optimizations will be analysed. It will also be demonstrated that the flexibility of the iterative techniques can be greatly enhanced through the use of dose-volume histogram based penalty functions and/or through the use of weighting factors assigned to each region of the patient. Finally, results will be presented from an investigation into the stability of the iterative techniques.
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- 1999
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5. A simple model for examining issues in radiotherapy optimization
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Lisa Angelos, David M. Shepard, Otto Sauer, Gustavo H. Olivera, Paul J. Reckwerdt, and T. Rockwell Mackie
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Computation ,Physics::Medical Physics ,law.invention ,Matrix (mathematics) ,Superposition principle ,Optics ,law ,Dosimetry ,Computer Simulation ,Radiation treatment planning ,Mathematics ,Photons ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Reproducibility of Results ,Radiotherapy Dosage ,Collimator ,General Medicine ,Models, Theoretical ,Pencil (optics) ,Physics::Accelerator Physics ,business ,Algorithm ,Software ,Beam (structure) - Abstract
Convolution/superposition software has been used to produce a library of photon pencil beam dose matrices. This library of pencil beams is designed to serve as a tool for both education and investigation in the field of radiotherapy optimization. The elegance of this pencil beam model stems from its cylindrical symmetry. Because of the symmetry, the dose distribution for a pencil beam from any arbitrary angle can be determined through a simple rotation of a pre-computed dose matrix. Rapid dose calculations can thus be performed while maintaining the accuracy of a convolution/superposition based dose computation. The pencil beam data sets have been made publicly available. It is hoped that the data sets will facilitate a comparison of a variety of optimization and delivery approaches. This paper will present a number of studies designed to demonstrate the usefulness of the pencil beam data sets. These studies include an examination of the extent to which a treatment plan can be improved through either an increase in the number of beam angles and/or a decrease in the collimator size. A few insights into the significance of heterogeneity corrections for treatment planning for intensity modulated radiotherapy will also be presented.
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- 1999
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6. Six parameter patient registration directly from projection data
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E E Fitchard, Alex Iosevich, Thomas R. Mackie, J S Aldridge, Paul J. Reckwerdt, and Gustavo H. Olivera
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Physics ,Nuclear and High Energy Physics ,medicine.medical_specialty ,Physics::Medical Physics ,chemistry.chemical_element ,Experimental data ,Radon ,Iterative reconstruction ,Patient registration ,Shift theorem ,symbols.namesake ,Fourier transform ,chemistry ,Projection-slice theorem ,symbols ,medicine ,Medical physics ,Projection (set theory) ,Instrumentation ,Algorithm - Abstract
Patient registration, a technique to ensure dose conformity, is an essential part of tomographic radiotherapy. A new six parameter (three translational and three angular) algorithm to implement this technique has been developed. The method is stable, accurate, and most importantly uses sinogram data as input, obviating image reconstruction. A sinogram, an array of Radon transforms, is derived directly from the raw data, which are photon transmission fluences from either a diagnostic or a megavoltage X-ray source. The algorithm uses properties of the Radon and Fourier transforms, such as the central slice theorem and Fourier shift theorem, to decouple translational and angular offsets. The theoretical underpinnings of this algorithm are presented here, whereas numerical verification using synthetic and experimental data is presented elsewhere.
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- 1999
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7. Modeling dose distributions from portal dose images using the convolution/superposition method
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Paul J. Reckwerdt, Bhudatt R. Paliwal, T. Rock Mackie, and Todd McNutt
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Photons ,Radiotherapy ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Dose profile ,Radiotherapy Dosage ,General Medicine ,Iterative reconstruction ,Image plane ,Imaging phantom ,Kernel (image processing) ,Medical imaging ,Humans ,Dosimetry ,Tomography, X-Ray Computed ,Nuclear medicine ,business ,Monte Carlo Method ,Algorithms ,Monitoring, Physiologic ,Mathematics ,Biomedical engineering ,Image-guided radiation therapy - Abstract
Post-treatment dose verification refers to the process of reconstructing delivered dose distributions internal to a patient from information obtained during the treatment. The exit dose is commonly used to describe the dose beyond the exit surface of the patient from a megavoltage photon beam. Portal imaging provides a method of determining the dose in a plane distal to a patient from a megavoltage therapeutic beam. This exit dose enables reconstruction of the dose distribution from external beam radiation throughout the patient utilizing the convolution/superposition method and an extended phantom. An iterative convolution/superposition algorithm has been created to reconstruct dose distributions in patients from exit dose measurements during a radiotherapy treatment. The method is based on an extended phantom that includes the patient CT representation and an electronic portal imaging device (EPID). The convolution/superposition method computes the dose throughout the extended phantom, which allows the portal dose image to be predicted in the EPID. The process is then reversed to take the portal dose measurement and infer what the dose distribution must have been to produce the measured portal dose. The dose distribution is modeled without knowledge of the incident intensity distribution, and includes the effects of scatter in the computation. The iterative method begins by assuming that the primary energy fluence (PEF) at the portal image plane is equal to the portal dose image, the PEF is then back-projected through the extended phantom and convolved with the dose deposition kernel to determine a new prediction of the portal dose image. The image of the ratio of the computed PEF to the computed portal dose is then multiplied by the measured portal dose image to produce a better representation of the PEF. Successive iterations of this process then converge to the exiting PEF image that would produce the measured portal dose image. Once convergence is established, the dose distribution is determined by back-projecting the PEF and convolving with the dose deposition kernel. The method is accurate, provided the patient representation during treatment is known. The method was used on three phantoms with a photon energy of 6 MV to verify convergence and accuracy of the algorithm. The reconstructed dose volumes agree to within 3% of the forward computation dose volumes. Furthermore, this technique assumes no prior knowledge of the incident fluence and therefore may better represent the dose actually delivered.
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- 1996
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8. Calculation of portal dose using the convolution/superposition method
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Paul J. Reckwerdt, Todd McNutt, T. Rock Mackie, Nikos Papanikolaou, and Bhudatt R. Paliwal
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Physics ,Phantoms, Imaging ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Biophysics ,Water ,Image registration ,Image processing ,General Medicine ,Image plane ,Biophysical Phenomena ,Imaging phantom ,Convolution ,Radiotherapy, High-Energy ,Medical imaging ,Humans ,Scattering, Radiation ,Tomography ,Radiometry ,Tomography, X-Ray Computed ,Nuclear medicine ,business ,Monte Carlo Method ,Biomedical engineering ,Image-guided radiation therapy - Abstract
The convolution/superposition method was used to predict the dose throughout an extended volume, which includes a phantom and a portal imaging device. From the calculated dose volume, the dose delivered in the portal image plane was extracted and compared to a portal dose image. This comparison aids in verifying the beam configuration or patient setup after delivery of the radiation. The phantoms used to test the accuracy of this method include a solid water cube, a Nuclear Associates CT phantom, and an Alderson Rando thorax phantom. The dose distribution in the image plane was measured with film and an electronic portal imaging device in each case. The calculated portal dose images were within 4% of the measured images for most voxels in the central portion of the field for all of the extended volumes. The convolution/superposition method also enables the determination of the scatter and primary dose contributions using the particular dose deposition kernels for each contribution. The ratio of primary dose to total dose was used to extract the primary dose from the detected portal image, which enhances the megavoltage portal images by removing scatter blurring. By also predicting the primary energy fluence, we can find the ratio of computed primary energy fluence to total dose. Multiplying this ratio by the measured dose image estimates the relative primary energy fluence at the portal imager. The image of primary energy fluence possesses higher contrast and may be used for further quantitative image processing and dose modeling.
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- 1996
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9. An iterative filtered backprojection inverse treatment planning algorithm for tomotherapy
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Paul J. Reckwerdt, T. Rock Mackie, and Timothy Holmes
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Male ,Cancer Research ,Radiation ,Iterative method ,business.industry ,Radiotherapy Planning, Computer-Assisted ,medicine.medical_treatment ,Physics::Medical Physics ,Prostatic Neoplasms ,Inverse transform sampling ,Breast Neoplasms ,Iterative reconstruction ,Inverse problem ,Residual ,Tomotherapy ,Multileaf collimator ,Adaptive filter ,Oncology ,Image Processing, Computer-Assisted ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,business ,Algorithm ,Algorithms - Abstract
Purpose : An inverse treatment planning algorithm for tomotherapy is described. Methods and Materials : The algorithm iteratively computes a set of nonnegative beam intensity profiles that minimizes the least-squares residual dose defined in the target and selected normal tissue regions of interest. At each iteration the residual dose distribution is transformed into a set of residual beam profiles using an inversion method derived from filtered backprojection image reconstruction theory. These residual profiles are used to correct the current beam profile estimates resulting in new profile estimates. Adaptive filtering is incorporated into the inversion model so that the gross structure of the dose distribution is optimized during initial iterations of the algorithm, and the fine structure corresponding to edges is obtained at later iterations. A three dimensional, kernel based, convolution/superposition dose model is used to compute dose during each iteration. Results : Two clinically relevant treatment planning examples are presented illustrating the use of the algorithm for planning conformal radiotherapy of the breast and the prostate. Solutions are generally achieved in 10-20 iterations requiring about 20 h of CPU time using a midrange workstation. The majority of the calculation time is spent on the three-dimensional dose calculation. Conclusions : The inverse treatment planning algorithm is a useful research tool for exploring the potential of tomotherapy for conformal radiotherapy. Further work is needed to (a) achieve clinically acceptable computation times ; (b) verify the algorithm using multileaf collimator technology ; and (c) extend the method to biological objectives.
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- 1995
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10. Tomotherapy: Optimized planning and delivery of radiation therapy
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James N. Yang, Timothy Holmes, T. Rockwell Mackie, and Paul J. Reckwerdt
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medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Physics::Medical Physics ,Monte Carlo method ,Dose profile ,Collimator ,Iterative reconstruction ,Tomotherapy ,Imaging phantom ,Electronic, Optical and Magnetic Materials ,law.invention ,Optics ,law ,medicine ,Medical physics ,Computer Vision and Pattern Recognition ,Electrical and Electronic Engineering ,business ,Radiation treatment planning ,Software ,Beam (structure) - Abstract
In contemporary radiotherapy dose optimization, radiation beams and beam modifiers are iteratively selected until the dose distribution is acceptable. Another approach, referred to as the “inverse problem,” is: Given the dose prescription, compute the optimal set of photon beams while preventing unphysical solutions such as negative beam weights, and iterate to achieve the prescription as closely as possible. This solution to this inverse problem, which uses image reconstruction mathematics, entails the delivery of large numbers of nonuniform beam intensities to produce uniform dose distributions. These dose distributions can be arranged to conform very closely to even complex target volumes, yet spare surrounding sensitive tissue. Alternatively, the dose distributions can be arranged to generously treat a regional field and “conformally avoid” overtreating sensitive volumes within the field. Multiple dose prescriptions can be delivered without additional effort. We propose that a practical way of delivering optimized dose distributions would be to intensity modulate a photon beam, using collimator leaves intersecting a slit field of radiation. Modulation is achieved by varying the time that the leaves are blocking the field. A practical geometry to deliver such a beam is a computed tomography-like gantry configuration, which also lends itself to tomographic setup verification of dose delivered to the patient. We refer to such a delivery method as “tomotherapy.” Several types of tomotherapy simulations have been conducted. A fully three dimensional optimized treatment planning system using iterative filtered back-projection have been developed. We will present examples of conformal plans for breast and prostate radiotherapy. We have constructed an experimental apparatus for simulating helical tomotherapy delivery by simultaneously rotating and longitudinally translating a phantom past an intensity-modulated fan beam. A comparison between a computation and and experimentally realized plan is presented. A Monte Carlo simulation of the angular distribution and energy fluence spectrum of 10-MV photons produced by a tungsten target have been used to estimate the optimized shape and mass of a primary shielding required to meet regulatory standards.
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- 1995
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11. Measurements of the electron dose distribution near inhomogeneities using a plastic scintillation detector
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Alex F. Bielajew, Daniel G. Schmidt, David W. O. Rogers, Mark A. Holmes, Nikos Papanikolaou, Carol M. Meger Wells, T. Rockwell Mackie, Joanna E. Cygler, Joseph K. Muehlenkamp, Paul J. Reckwerdt, and Matthew B. Podgorsak
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Cancer Research ,Physics::Instrumentation and Detectors ,Electrons ,Electron ,Scintillator ,Stopping power ,Models, Biological ,Radiotherapy, High-Energy ,Optics ,Neoplasms ,Humans ,Dosimetry ,Medicine ,Radiology, Nuclear Medicine and imaging ,Electrodes ,Radiation ,Dosimeter ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Detector ,Reproducibility of Results ,Radiotherapy Dosage ,Field electron emission ,Oncology ,Scintillation counter ,Scintillation Counting ,Nuclear medicine ,business ,Monte Carlo Method - Abstract
Purpose: Accurate measurement of the electron dose distribution near an inhomogeneity is difficult with traditional dosimeters which themselves perturb the electron field. We tested the performance of a new high resolution, water-equivalent plastic scintillation detector which has ideal properties for this application. Methods and Materials: A plastic scintillation detector with a 1 mm diameter, 3 mm long cylindrical sensitive volume was used to measure the dose distributions behind standard benchmark inhomogeneities in water phantoms. The plastic scintillator material is more water equivalent than polystyrene in terms of its mass collision stopping power and mass scattering power. Measurements were performed for beams of electrons having initial energies of 6 and 18 MeV at depths from 0.2–4.2 cm behind the inhomogeneities. Results: The detector reveals hot and cold spots behind heterogeneities at resolutions equivalent to typical film digitizer spot sizes. Plots of the dose distributions behind air, aluminum, lead, and formulations for cortical and inner bone-equivalent materials are presented. Conclusion: The plastic scintillation detector is suited for measuring the electron dose distribution near an inhomogeneity.
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- 1994
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12. Tomotherapy: A new concept for the delivery of dynamic conformal radiotherapy
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Bhudatt R. Paliwal, Stuart Swerdloff, Joseph O. Deasy, James N. Yang, Timothy Holmes, T. Rock Mackie, Timothy J. Kinsella, and Paul J. Reckwerdt
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medicine.medical_specialty ,Computer science ,medicine.medical_treatment ,Computed tomography ,Conformal radiotherapy ,Radiation ,Collimated light ,Linear particle accelerator ,Tomotherapy ,Optics ,medicine ,Humans ,Medical physics ,Image sensor ,Computed radiography ,Radiation treatment planning ,Radiotherapy ,medicine.diagnostic_test ,business.industry ,General Medicine ,Models, Theoretical ,Radiation therapy ,Megavoltage Computed Tomography ,Tomography, X-Ray Computed ,business ,Mathematics - Abstract
Tomotherapy, literally "slice therapy," is a proposal for the delivery of radiation therapy with intensity-modulated strips of radiation. The proposed method employs a linear accelerator, or another radiation-emitting device, which would be mounted on a ring gantry like a CT scanner. The patient would move through the bore of the gantry simultaneously with gantry rotation. The intensity modulation would be performed by temporally modulated multiple independent leaves that open and close across the slit opening. At any given time, any leaf would be (1) closed, covering a portion of the slit, (2) open, allowing radiation through, or (3) changing between these states. This method would result in the delivery of highly conformal radiation. Overall treatment times should be comparable with contemporary treatment delivery times. The ring gantry would make it convenient to mount a narrow multisegmented megavoltage detector system for beam verification and a CT scanner on the treatment unit. Such a treatment unit could become a powerful tool for treatment planning, conformal treatment, and verification using tomographic images. The physical properties of this treatment delivery are evaluated and the fundamental design specifications are justified.
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- 1993
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13. Investigation of the convolution method for polyenergetic spectra
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Nikos Papanikolaou, Paul J. Reckwerdt, Carol Meger-Wells, Mark A. Gehring, and T. Rockwell Mackie
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Photons ,Photon ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Physics::Medical Physics ,Monte Carlo method ,Biophysics ,Radiotherapy Dosage ,General Medicine ,Models, Theoretical ,Radiation Dosage ,Fluence ,Biophysical Phenomena ,Imaging phantom ,Spectral line ,Convolution ,Models, Structural ,Radiotherapy, High-Energy ,Optics ,Kernel (image processing) ,Humans ,Dosimetry ,business ,Monte Carlo Method ,Mathematics - Abstract
The distribution of absolute dose per unit fluence from polyenergetic photon beams impinging upon a water phantom was calculated using two convolution approaches that properly account for beam hardening effects. Dose deposition kernels calculated previously using the EGS4 Monte Carlo code are convolved with the primary terma to give the dose for monoenergetic photon beams of energies ranging from 100 kev to 50 MeV. A polyenergetic dose distribution is composed of separately calculated monoenergetic components, which are appropriately weighted with the fluence spectrum to yield the polyenergetic dose distribution. Alternatively, a single convolution for the polyenergetic beam is considered, where a composite polyenergetic kernel is convolved with the respective polyenergetic terma. The effects of the polyenergetic kernel variance due to beam hardening as well as the effect of tilting the kernels for a diverging beam geometry were also examined. The depth dose data produced using the two proposed methods were compared with measured data and Monte Carlo simulations and showed good agreement.
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- 1993
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14. A unified approach to the optimization of brachytherapy and external beam dosimetry
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Paul J. Reckwerdt, Douglas Simpkin, T. Rock Mackie, and Timothy Holmes
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Models, Anatomic ,Cancer Research ,Quantitative Biology::Tissues and Organs ,medicine.medical_treatment ,Brachytherapy ,Physics::Medical Physics ,Residual ,Fluence ,Computer Graphics ,medicine ,Humans ,Dosimetry ,Radiology, Nuclear Medicine and imaging ,Radiation ,Fourier Analysis ,Radiotherapy ,Radon transform ,business.industry ,Radiotherapy Dosage ,Computational physics ,Weighting ,Distribution (mathematics) ,Oncology ,Radon ,Nuclear medicine ,business ,Mathematics ,Beam (structure) - Abstract
Semi-automated optimization of dose distributions is possible using techniques borrowed from imaging science. The ideal distribution of dose is first deconvolved by a convolution kernel yielding an ideal weighting distribution in the patient. The weighting distribution describes the total energy released per unit mass of the irradiated medium. For internal and external radiation sources, this is directly related to the amount and distribution of radioactivity and energy fluence in the medium, respectively. For external sources, the exponential Radon transform is used to obtain ideal fluence projections incident on the patient. In both instances negative values are produced, which when set to zero result in perturbed dose distributions. This may necessitate iterative techniques to reduce the 'residual dose' produced by the zeroing process. Application of the approach is presented for the optimization of 2-dimensional dose distributions in external beam therapy, radioimmunotherapy, and brachytherapy sources.
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- 1991
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15. A compact linac for intensity modulated proton therapy based on a dielectric wall accelerator
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Y.-J. Chen, D. Sanders, J. Sullivan, D. Blackfield, A.C. Paul, J. Watson, Brian R. Poole, R. Schmidt, Paul J. Reckwerdt, John R. Harris, James A. Purdy, S.E. Sampayan, L. Wang, Dennis L Matthews, George J Caporaso, Thomas R. Mackie, C. Holmes, M. Rhodes, D. W. Pearson, Scott D. Nelson, R. W. Flynn, and S.A. Hawkins
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Engineering ,Biophysics ,General Physics and Astronomy ,Dielectric ,Linear particle accelerator ,Biophysical Phenomena ,Acceleration ,Optics ,Electric field ,Neoplasms ,Proton Therapy ,Humans ,Radiology, Nuclear Medicine and imaging ,Electrical conductor ,Proton therapy ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Electrical engineering ,General Medicine ,Equipment Design ,Dielectric wall accelerator ,Radiotherapy, Intensity-Modulated ,Particle Accelerators ,business ,Tomography, X-Ray Computed ,Intensity (heat transfer) - Abstract
A novel compact CT-guided intensity modulated proton radiotherapy (IMPT) system is described. The system is being designed to deliver fast IMPT so that larger target volumes and motion management can be accomplished. The system will be ideal for large and complex target volumes in young patients. The basis of the design is the dielectric wall accelerator (DWA) system being developed at the Lawrence Livermore National Laboratory (LLNL). The DWA uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The system will produce individual pulses that can be varied in intensity, energy and spot width. The IMPT planning system will optimize delivery characteristics. The system will be capable of being sited in a conventional linac vault and provide intensity modulated rotational therapy. Feasibility tests of an optimization system for selecting the position, energy, intensity and spot size for a collection of spots comprising the treatment are underway. A prototype is being designed and concept designs of the envelope and environmental needs of the unit are beginning. The status of the developmental new technologies that make the compact system possible will be reviewed. These include, high gradient vacuum insulators, solid dielectric materials, SiC photoconductive switches and compact proton sources.
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- 2007
16. Accurate convolution/superposition for multi-resolution dose calculation using cumulative tabulated kernels
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Gustavo H. Olivera, Mingli Chen, Paul J. Reckwerdt, Weiguo Lu, and Thomas R. Mackie
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Computation ,medicine.medical_treatment ,Geometry ,computer.software_genre ,Models, Biological ,Sensitivity and Specificity ,Imaging phantom ,Tomotherapy ,Superposition principle ,Voxel ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Computer Simulation ,Radiometry ,Mathematics ,Radiological and Ultrasound Technology ,Radiotherapy Planning, Computer-Assisted ,Mathematical analysis ,Reproducibility of Results ,Radiotherapy Dosage ,Kernel (image processing) ,Radiographic Image Interpretation, Computer-Assisted ,Tomography ,Radiotherapy, Conformal ,computer ,Tomography, Spiral Computed ,Beam (structure) ,Algorithms - Abstract
Convolution/superposition (C/S) is regarded as the standard dose calculation method in most modern radiotherapy treatment planning systems. Different implementations of C/S could result in significantly different dose distributions. This paper addresses two major implementation issues associated with collapsed cone C/S: one is how to utilize the tabulated kernels instead of analytical parametrizations and the other is how to deal with voxel size effects. Three methods that utilize the tabulated kernels are presented in this paper. These methods differ in the effective kernels used: the differential kernel (DK), the cumulative kernel (CK) or the cumulative-cumulative kernel (CCK). They result in slightly different computation times but significantly different voxel size effects. Both simulated and real multi-resolution dose calculations are presented. For simulation tests, we use arbitrary kernels and various voxel sizes with a homogeneous phantom, and assume forward energy transportation only. Simulations with voxel size up to 1 cm show that the CCK algorithm has errors within 0.1% of the maximum gold standard dose. Real dose calculations use a heterogeneous slab phantom, both the 'broad' (5 x 5 cm2) and the 'narrow' (1.2 x 1.2 cm2) tomotherapy beams. Various voxel sizes (0.5 mm, 1 mm, 2 mm, 4 mm and 8 mm) are used for dose calculations. The results show that all three algorithms have negligible difference (0.1%) for the dose calculation in the fine resolution (0.5 mm voxels). But differences become significant when the voxel size increases. As for the DK or CK algorithm in the broad (narrow) beam dose calculation, the dose differences between the 0.5 mm voxels and the voxels up to 8 mm (4 mm) are around 10% (7%) of the maximum dose. As for the broad (narrow) beam dose calculation using the CCK algorithm, the dose differences between the 0.5 mm voxels and the voxels up to 8 mm (4 mm) are around 1% of the maximum dose. Among all three methods, the CCK algorithm is demonstrated to be the most accurate one for multi-resolution dose calculations.
- Published
- 2005
17. Radiation characteristics of helical tomotherapy
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D. W. Pearson, Robert Jeraj, Gustavo H. Olivera, Paul J. Reckwerdt, Kenneth J. Ruchala, Thomas R. Mackie, J M Kapatoes, and John Balog
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Photon ,Materials science ,medicine.medical_treatment ,Electrons ,Electron ,Radiation ,Sensitivity and Specificity ,Tomotherapy ,Optics ,Nuclear magnetic resonance ,medicine ,Humans ,Tomography ,Photons ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,General Medicine ,Electromagnetic shielding ,Radiation protection ,Particle Accelerators ,Radiotherapy, Conformal ,business ,Intensity modulation ,Monte Carlo Method ,Beam (structure) ,Software - Abstract
Helical tomotherapy is a dedicated intensity modulated radiation therapy (IMRT) system with on-board imaging capability (MVCT) and therefore differs from conventional treatment units. Different design goals resulted in some distinctive radiation field characteristics. The most significant differences in the design are the lack of flattening filter, increased shielding of the collimators, treatment and imaging operation modes and narrow fan beam delivery. Radiation characteristics of the helical tomotherapy system, sensitivity studies of various incident electron beam parameters and radiation safety analyses are presented here. It was determined that the photon beam energy spectrum of helical tomotherapy is similar to that of more conventional radiation treatment units. The two operational modes of the system result in different nominal energies of the incident electron beam with approximately 6 MeV and 3.5 MeV in the treatment and imaging modes, respectively. The off-axis mean energy dependence is much lower than in conventional radiotherapy units with less than 5% variation across the field, which is the consequence of the absent flattening filter. For the same reason the transverse profile exhibits the characteristic conical shape resulting in a 2-fold increase of the beam intensity in the center. The radiation leakage outside the field was found to be negligible at less than 0.05% because of the increased shielding of the collimators. At this level the in-field scattering is a dominant source of the radiation outside the field and thus a narrow field treatment does not result in the increased leakage. The sensitivity studies showed increased sensitivity on the incident electron position because of the narrow fan beam delivery and high sensitivity on the incident electron energy, as common to other treatment systems. All in all, it was determined that helical tomotherapy is a system with some unique radiation characteristics, which have been to a large extent optimized for intensity modulated delivery.
- Published
- 2004
18. Image guidance for precise conformal radiotherapy
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Robert Jeraj, J M Kapatoes, Minesh P. Mehta, Bhudatt R. Paliwal, Wolfgang A. Tomé, Lisa J. Forrest, Paul M. Harari, Gustavo H. Olivera, Jim Welsh, Paul J. Reckwerdt, Weiguo Lu, H. Keller, Thomas R. Mackie, K. J. Ruchala, Mark A. Ritter, Jack F. Fowler, and Chuan Wu
- Subjects
Cancer Research ,medicine.medical_specialty ,medicine.medical_treatment ,Automated segmentation ,Normal tissue ,Conformal radiotherapy ,Tomotherapy ,Radiotherapy, High-Energy ,Motion ,Conventional radiotherapy ,Dogs ,Neoplasms ,medicine ,Animals ,Humans ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Image guidance ,Radiation Injuries ,Ultrasonography ,Radiation ,business.industry ,Radiotherapy Planning, Computer-Assisted ,Equipment Design ,Radiotherapy, Computer-Assisted ,Radiation therapy ,Oncology ,Tomography ,Particle Accelerators ,Radiotherapy, Conformal ,business ,Tomography, X-Ray Computed - Abstract
Purpose To review the state of the art in image-guided precision conformal radiotherapy and to describe how helical tomotherapy compares with the image-guided practices being developed for conventional radiotherapy. Methods and materials Image guidance is beginning to be the fundamental basis for radiotherapy planning, delivery, and verification. Radiotherapy planning requires more precision in the extension and localization of disease. When greater precision is not possible, conformal avoidance methodology may be indicated whereby the margin of disease extension is generous, except where sensitive normal tissues exist. Radiotherapy delivery requires better precision in the definition of treatment volume, on a daily basis if necessary. Helical tomotherapy has been designed to use CT imaging technology to plan, deliver, and verify that the delivery has been carried out as planned. The image-guided processes of helical tomotherapy that enable this goal are described. Results Examples of the results of helical tomotherapy processes for image-guided intensity-modulated radiotherapy are presented. These processes include megavoltage CT acquisition, automated segmentation of CT images, dose reconstruction using the CT image set, deformable registration of CT images, and reoptimization. Conclusion Image-guided precision conformal radiotherapy can be used as a tool to treat the tumor yet spare critical structures. Helical tomotherapy has been designed from the ground up as an integrated image-guided intensity-modulated radiotherapy system and allows new verification processes based on megavoltage CT images to be implemented.
- Published
- 2003
19. Methods for improving limited field-of-view radiotherapy reconstructions using imperfect a priori images
- Author
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Kenneth J. Ruchala, Paul J. Reckwerdt, Thomas Rockwell Mackie, Gustavo H. Olivera, and J M Kapatoes
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Male ,Quality Control ,Computer science ,medicine.medical_treatment ,Field of view ,Computed tomography ,Iterative reconstruction ,computer.software_genre ,Sensitivity and Specificity ,Monitoring, Intraoperative ,Medical imaging ,medicine ,Dosimetry ,Humans ,Computer vision ,Computed radiography ,Radiometry ,Retrospective Studies ,medicine.diagnostic_test ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Prostatic Neoplasms ,Reproducibility of Results ,Radiotherapy Dosage ,General Medicine ,Sensor fusion ,Radiotherapy, Computer-Assisted ,Radiation therapy ,Radiographic Image Enhancement ,Tomography x ray computed ,Subtraction Technique ,A priori and a posteriori ,Artificial intelligence ,Data mining ,Tomography ,business ,Tomography, X-Ray Computed ,computer ,Algorithms - Abstract
There are many benefits to having an online CT imaging system for radiotherapy, as it helps identify changes in the patient's position and anatomy between the time of planning and treatment. However, many current online CT systems suffer from a limited field-of-view (LFOV) in that collected data do not encompass the patient's complete cross section. Reconstruction of these data sets can quantitatively distort the image values and introduce artifacts. This work explores the use of planning CT data as a priori information for improving these reconstructions. Methods are presented to incorporate this data by aligning the LFOV with the planning images and then merging the data sets in sinogram space. One alignment option is explicit fusion, producing fusion-aligned reprojection (FAR) images. For cases where explicit fusion is not viable, FAR can be implemented using the implicit fusion of normal setup error, referred to as normal-error-aligned reprojection (NEAR). These methods are evaluated for multiday patient images showing both internal and skin-surface anatomical variation. The iterative use of NEAR and FAR is also investigated, as are applications of NEAR and FAR to dose calculations and the compensation of LFOV online MVCT images with kVCT planning images. Results indicate that NEAR and FAR can utilize planning CT data as imperfect a priori information to reduce artifacts and quantitatively improve images. These benefits can also increase the accuracy of dose calculations and be used for augmenting CT images (e.g., MVCT) acquired at different energies than the planning CT.
- Published
- 2002
20. Registration of tomotherapy animal study data
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E E Fitchard, J M Kapatoes, R Mackie, K.J. Ruchala, Gustavo H. Olivera, and Paul J. Reckwerdt
- Subjects
Engineering ,Offset (computer science) ,business.industry ,medicine.medical_treatment ,Experimental data ,Data structure ,Tomotherapy ,Standard deviation ,medicine ,Animal study ,Degree (angle) ,business ,Algorithm ,Simulation - Abstract
Until recently, post optimization concepts underlying tomotherapy have been tested experimentally only on inanimate phantoms. New experimental data, from a canine head, has provided data structures similar to humane. Here, the authors report the initial test results from registration of 11 sinograms. This data has experimental offsets in (x,y,z) and roll. Since it is known from earlier studies that simultaneous offsets in z and roll present one of the greatest challenges to the algorithm, these offsets were emphasized. Although, only four parameters were varied the algorithm computes results for all six possible offsets-(x,y,z), (pitch,yaw,roll). Standard deviations of the differences between experimental and algorithmic values were computed for each offset. The largest a's were 0.3 mm and 0.1 degree that are small in comparison with the specifications of /spl plusmn/2 mm and /spl plusmn/2 degrees. The algorithm is now in the prototyping stage. Several enhancements are under study prior to release of version one. This data will provide a realistic test for these enhancements.
- Published
- 2002
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21. Large-scale helical tomotherapy optimization: four clinical case studies
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Paul J. Reckwerdt, Gustavo H. Olivera, David M. Shepard, and Thomas R. Mackie
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Flexibility (engineering) ,Engineering ,medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,Conformal map ,computer.software_genre ,Tomotherapy ,Voxel ,Histogram ,medicine ,Dosimetry ,Medical physics ,business ,Computer-aided software engineering ,computer ,Algorithm ,Intensity modulation - Abstract
Helical tomotherapy is an integrated therapeutic technique that includes planning, delivery and verification capabilities. Helical tomotherapy allows for irradiation of a large number of targets and region at risk (RAR) over broad regions of the body; a large-scale optimization technique is necessary. Usually a tomotherapy treatment will have tens to hundreds of thousands of pencils beams for which intensity needs to be optimized. Moreover the number of voxels where the dose needs to be computed is on the order of 1,000,000. The complexity and size of the optimization is the price paid in tomotherapy in order to obtain coplanar deliveries that are neither limited by the number of beam directions nor the degree of modulation used during delivery. It is important to note, however, that because of the simplicity and capabilities of the tomotherapy concept, a complex optimization plan will not lead to a complex delivery. The complexity of delivery is almost independent of the complexity on the optimization. In this work 4 clinical conformal and conformal avoidance optimization cases are be shown. Breast, prostate, mesothelioma and nasopharyengeal cases are presented and compared with some of the standard techniques used currently distributions and DVH's are shown to illustrate examples of the deliveries that can be achieved. The flexibility obtained to optimize both conformal and conformal avoidance treatments is also discussed.
- Published
- 2002
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22. The limitations of dose reconstruction without treatment imaging
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Paul J. Reckwerdt, J. Smilowitz, Thomas R. Mackie, K.J. Ruchala, J M Kapatoes, and Gustavo H. Olivera
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Radiation therapy ,medicine.medical_specialty ,business.industry ,medicine.medical_treatment ,medicine ,Dosimetry ,Radiology ,Energy fluence ,Adaptive radiotherapy ,business ,Nuclear medicine ,Imaging phantom - Abstract
Dose reconstruction (DR) is a radiotherapy process in which the full three-dimensional dose actually delivered to a patient is computed. The calculation is performed on a CT of the patient in the actual treatment position using the actual energy fluence obtained from delivery verification (DV). This provides valuable information regarding the efficacy of a treatment. Specifically, this is the basis for fraction-by-fraction adaptive radiotherapy. However, dose reconstruction is only as accurate as the inputs to the computation, namely the verified fluence and the CT. Studies were conducted regarding the effects of positional errors and internal anatomy changes for a canine nasopharyngeal treatment and a prostate treatment on an abdominal phantom, respectively. It was found that energy fluence errors may or may not be detected in DV. However, even if an error was detected, the authors show that the potential effects on outcome could not possibly be addressed without a CT at the time of delivery.
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- 2002
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23. On the accuracy and effectiveness of dose reconstruction for tomotherapy
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Thomas R. Mackie, H. Keller, Gustavo H. Olivera, John Balog, Paul J. Reckwerdt, and J M Kapatoes
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Materials science ,Time Factors ,medicine.medical_treatment ,Monte Carlo method ,Breast Neoplasms ,computer.software_genre ,Fluence ,Imaging phantom ,Tomotherapy ,Voxel ,medicine ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiometry ,Radiological and Ultrasound Technology ,business.industry ,Phantoms, Imaging ,Detector ,Reproducibility of Results ,Thorax ,Multileaf collimator ,Nuclear medicine ,business ,Tomography, X-Ray Computed ,computer ,Monte Carlo Method ,Algorithms ,Biomedical engineering - Abstract
Dose reconstruction is a process that re-creates the treatment-time dose deposited in a patient provided there is knowledge of the delivered energy fluence and the patient's anatomy at the time of treatment. A method for reconstructing dose is presented. The process starts with delivery verification, in which the incident energy fluence from a treatment is computed using the exit detector signal and a transfer matrix to convert the detector signal to energy fluence. With the verified energy fluence and a CT image of the patient in the treatment position, the treatment-time dose distribution is computed using any model-based algorithm such as convolution/superposition or Monte Carlo. The accuracy of dose reconstruction and the ability of the process to reveal delivery errors are presented. Regarding accuracy, a reconstructed dose distribution was compared with a measured film distribution for a simulated breast treatment carried out on a thorax phantom. It was found that the reconstructed dose distribution agreed well with the dose distribution measured using film: the majority of the voxels were within the low and high dose-gradient tolerances of 3% and 3 mm respectively. Concerning delivery errors, it was found that errors associated with the accelerator, the multileaf collimator and patient positioning might be detected in the verified energy fluence and are readily apparent in the reconstructed dose. For the cases in which errors appear in the reconstructed dose, the possibility for adaptive radiotherapy is discussed.
- Published
- 2001
24. Megavoltage CT imaging as a by-product of multileaf collimator leakage
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Gustavo H. Olivera, Thomas R. Mackie, J M Kapatoes, K.J. Ruchala, E A Schloesser, and Paul J. Reckwerdt
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Image quality ,Megavoltage ct ,medicine.medical_treatment ,Conformal radiation therapy ,Iterative reconstruction ,law.invention ,Radiotherapy, High-Energy ,law ,Neoplasms ,Image Processing, Computer-Assisted ,Medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Leakage (electronics) ,Likelihood Functions ,Photons ,Radiological and Ultrasound Technology ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Collimator ,Radiation therapy ,Multileaf collimator ,business ,Nuclear medicine ,Tomography, X-Ray Computed ,Tomography, Emission-Computed - Abstract
In addition to their potential for the delivery of highly conformal radiation therapy treatments, tomotherapeutic treatments also feature increased potential for verification. For example, megavoltage CT allows one to use the megavoltage linac to generate tomographic images of the patient in the treatment position. This is typically done before or after radiation therapy treatments. However, it is also possible to collect MVCT images entirely during the treatment itself. This process utilizes the leakage radiation through the closed leaves of the Nomos MIMiC MLC, along with slight inefficiencies in treatment delivery, to generate MVCT images during treatment that require neither additional time nor dose. The image quality is limited, yet sufficient to see a patient's external boundary, density differences over 8% for 25.0 mm objects and resolutions of 3.0 mm for high-contrast objects. Such images can potentially be viewed during treatment, used to flag additional CT immediately after the treatment and provide a representation of the patient's exact position during treatment for use with dose reconstruction.
- Published
- 2000
25. Experimental study of six parameter patient registration from helical MV fan-beam data
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Edward E. Fitchard, R. Hinderer, Paul J. Reckwerdt, Kenneth J. Ruchala, Rock Mackie, Gustavo H. Olivera, and J M Kapatoes
- Subjects
Computer science ,medicine.medical_treatment ,medicine ,Patient positioning ,Angular error ,Patient registration ,Gantry angle ,Beam (structure) ,Tomotherapy ,Biomedical engineering ,Cancer treatment - Abstract
Tornotherapy, a cancer treatment method capable of delivering dose to difficult tumor geometries, require precise patient positioning or registration. The initial objective for the tomotherapy registration problem was to obtain distance errors less than ±2 mm and angular errors less than ±2°.
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- 2000
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26. Tomotherapy: Optimal coplanar radiotherapy
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Gustavo H. Olivera, T. Rockwell Mackie, Paul J. Reckwerdt, and Harald Keller
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Radiation therapy ,business.industry ,Computer science ,medicine.medical_treatment ,medicine ,Multi leaf collimator ,Nuclear medicine ,business ,Rotational therapy ,Tomotherapy ,Helical ct - Abstract
Tomotherapy, literally “slice therapy”, is intensity-modulated fan-beam rotational therapy. The NOMOS Peacock™ system is a serial (or sequential slice) tomotherapy system [1]. It is installed in more than 50 U.S. centers and has been used in the treatments of thousands of patients. Helical tomotherapy, like helical CT, has the fan beam continuously rotating around the patient as the couch is transporting the patient longitudinally through a ring gantry [2–7]. The Tomotherapy Research Group at the University of Wisconsin is assembling the first helical tomotherapy unit at the UW’s Physical Sciences Laboratory at the Kegonsa Research Campus. Figure 1 is a photograph of the gantry for this unit while under construction.
- Published
- 2000
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27. Tomographic Verification of Tomotherapy -- Before, During, and After Treatment
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John Balog, D. W. Pearson, T. R. Mackie, J. Smilowitz, E A Schloesser, Paul J. Reckwerdt, K. J. Ruchala, G. H. Olivera, and J M Kapatoes
- Subjects
medicine.medical_specialty ,Tomographic reconstruction ,Computer science ,Megavoltage ct ,medicine.medical_treatment ,Conformal radiation therapy ,Conformal radiotherapy ,Tomotherapy ,Feature (computer vision) ,Treatment delivery ,medicine ,Medical physics ,sense organs ,After treatment - Abstract
Many improvements in conformal radiotherapy have allowed for increased precision in treatment delivery, and the goal of tomotherapy is to carry these improvements further. However, the ability to deliver highly conformal radiation therapy treatments is only useful to the extent that the patient’s position and anatomy are known. Certainly, it is important to set-up the patient correctly, but ideally, one should also verify that a patient’s internal organs are correctly positioned and that they have not changed in size or shape. This verification can be achieved through the integration of tomographic imaging capabilities. Tomotherapy systems will feature such tomographic verification, initally through megavoltage CT (MVCT), and potentially with on-board kilovoltage CT (kVCT) in future implementations. In addition to being important to treatments, tomographic images are also necessary for dose reconstruction to verify the treatment delivery [1,2].
- Published
- 2000
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28. Delivery Modification as an Alternative to Patient Repositioning in Tomotherapy
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E E Fitchard, Gustavo H. Olivera, Paul J. Reckwerdt, K.J. Ruchala, and Thomas R. Mackie
- Subjects
Radiation therapy ,Intensity modulate radiotherapy ,business.industry ,medicine.medical_treatment ,medicine ,Energy fluence ,Intensity modulated radiotherapy ,Nuclear medicine ,business ,Closed loop ,Tomotherapy - Abstract
Tomotherapy is an Intensity Modulated Radiotherapy (IMRT) technique that has a set of processes completing a closed loop for planning, delivery and verification in radiotherapy[1].
- Published
- 2000
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29. Database Energy Fluence Verification and the Importance of On-Board CT Imaging in Dose Reconstruction
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J M Kapatoes, J. Smilowitz, Gustavo H. Olivera, Thomas R. Mackie, D. W. Pearson, K.J. Ruchala, John Balog, and Paul J. Reckwerdt
- Subjects
Physics ,Dose-volume histogram ,business.industry ,Quantitative Biology::Tissues and Organs ,medicine.medical_treatment ,Physics::Medical Physics ,Monte Carlo method ,Detector ,Collimator ,Radiation ,Tomotherapy ,law.invention ,Convolution ,Radiation therapy ,Optics ,law ,medicine ,Nuclear medicine ,business - Abstract
Helical tomotherapy is a radiation therapy technique that utilizes a rotating fan beam of intensity-modulated radiation to deliver dose. The integration of the accelerator, multi-leaf collimator (MLC), and a computed tomography (CT) detector on a single ring gantry allows for dose reconstruction, in which the full 3D dose delivered to the patient is reconstructed1. The incident energy fluence computed using the detected signal2 and a CT image in the treatment position are the inputs for any model-based dose computation algorithm such as convolution/superposition (C/S) or Monte Carlo (MC).
- Published
- 2000
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30. A proposal for a standard electronic anthropomorphic phantom for radiotherapy
- Author
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Thomas Rockwell Mackie, J S Aldridge, and Paul J. Reckwerdt
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Adult ,Male ,medicine.medical_specialty ,Databases, Factual ,medicine.medical_treatment ,Biophysics ,Computed tomography ,projects ,Biophysical Phenomena ,Medical imaging ,medicine ,Humans ,Medical physics ,Computed radiography ,medicine.diagnostic_test ,Anatomy, Cross-Sectional ,National Library of Medicine (U.S.) ,Radiotherapy ,Visible human project ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,General Medicine ,computer.file_format ,United States ,Radiation therapy ,projects.project ,Anthropomorphic phantom ,Female ,Image file formats ,Tomography ,business ,Tomography, X-Ray Computed ,computer - Abstract
To create a database of human male and female computed tomography (CT) slices, the National Library of Medicine organized the "Visible Human Project." Since the male and female data sets provided are approximately 269 MB and 915 MB, respectively, both the size and complexity have been reduced. While making the slices accessible to those with limited computing resources, the production of these reduced data sets also presents a unique opportunity to establish a standard human CT slice library for research in radiation therapy. A brief history of the original data sets is included, as well as details of the reduction process, applications to radiotherapy, and information on accessing these reduced image files.
- Published
- 1999
31. Delivery verification in sequential and helical tomotherapy
- Author
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Thomas R. Mackie, E E Fitchard, J M Kapatoes, Gustavo H. Olivera, Paul J. Reckwerdt, and E A Schloesser
- Subjects
Computer science ,medicine.medical_treatment ,Posture ,Conformal radiotherapy ,Radiation ,Signal ,Tomotherapy ,Imaging phantom ,medicine ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Polytetrafluoroethylene ,Radiological and Ultrasound Technology ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Detector ,Reproducibility of Results ,Water ,Radiotherapy Dosage ,Equipment Design ,Models, Theoretical ,Multileaf collimator ,Radiation therapy ,Acrylates ,Polystyrenes ,Particle Accelerators ,Polyethylenes ,Radiotherapy, Conformal ,Nuclear medicine ,business ,Tomography, X-Ray Computed ,Biomedical engineering - Abstract
Conformal and conformal avoidance radiation therapy are new therapeutic techniques that are generally characterized by high dose gradients. The success of this kind of treatment relies on quality assurance procedures in order to verify the delivery of the treatment. A delivery verification technique should consider quality assurance procedures for patient positioning and radiation delivery verification. A methodology for radiation delivery verification was developed and tested with our tomotherapy workbench. The procedure was investigated for two cases. The first treatment using a torus-shaped target was optimized for 72 beam directions and sequentially delivered as a single slice to a 33 cm diameter cylinder of homogeneous solid water. For the second treatment, a random pattern of energy fluence was helically delivered for two slices to a 9.0 cm diameter phantom containing inhomogeneities. The presented process provides the energy fluence (or a related quantity) delivered through the multileaf collimator (MLC) using the signal measured at the exit detector during the treatment delivery. As this information is created for every pulse of the accelerator, the energy fluence and state for each MLC leaf were verified on a pulse-by-pulse basis. The pulse-by-pulse results were averaged to obtain projection-by-projection information to allow for a comparison with the planned delivery. The errors between the planned and delivered energy fluences were concentrated between +/-2.0%, with none beyond +/-3.5%. In addition to accurately achieving radiation delivery verification, the process is fast, which could translate to radiation delivery verification in real time. This technique can also be extended to reconstruct the dose actually deposited in the patient or phantom (dose reconstruction).
- Published
- 1999
32. Characterization of the output for helical delivery of intensity modulated slit beams
- Author
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M. Glass, Paul J. Reckwerdt, Lisa Angelos, John Balog, and Thomas Rockwell Mackie
- Subjects
Physics ,Monitor unit ,business.industry ,medicine.medical_treatment ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,General Medicine ,Sensitivity and Specificity ,Linear particle accelerator ,Imaging phantom ,Tomotherapy ,Radiotherapy, Computer-Assisted ,Multileaf collimator ,Superposition principle ,Optics ,Energy Transfer ,medicine ,Dosimetry ,Humans ,Particle Accelerators ,business ,Beam (structure) ,Algorithms - Abstract
The UW tomotherapy workbench utilizes a convolution/superposition based dose calculation and optimization program. It specifies the energy fluence that must be delivered from each leaf for each phantom projection angle. This requires that the spectrum of the radiation emitted from the one-dimensional MLC(multileaf collimator) attached to the linear accelerator be determined. The steps involved in that process are described. The spectrum along the central axis of the slit beam was determined, as well as the softening with off-axis position. Moreover, the magnitude of the energy-fluence output had to be quantified on a per MU (monitor unit) basis. This was done for a single leaf along the central axis of the beam. Factors, which modify that energy-fluence output, were investigated. The output increases with off-axis position due to the horns of the beam. The output for a leaf of interest will also increase if additional leaves are open due to the absence of the tongue-and-groove effect and penumbra blurring. The energy-fluence increase per leaf increases by 4.9% if an adjacent leaf is open. No other factors related to the state of additional leaves were found to significantly increase the energy-fluence output for an individual leaf.
- Published
- 1999
33. Maximum likelihood as a common computational framework in tomotherapy
- Author
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J Zachman, Thomas R. Mackie, K.J. Ruchala, Gustavo H. Olivera, David M. Shepard, Paul J. Reckwerdt, and E E Fitchard
- Subjects
Computer science ,Maximum likelihood ,medicine.medical_treatment ,Biophysics ,Iterative reconstruction ,Tomotherapy ,Biophysical Phenomena ,Radiotherapy, High-Energy ,Neoplasms ,medicine ,Dosimetry ,Humans ,Radiology, Nuclear Medicine and imaging ,Radiation treatment planning ,Simulation ,Likelihood Functions ,Radiological and Ultrasound Technology ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Models, Theoretical ,Radiation therapy ,Radiographic Image Interpretation, Computer-Assisted ,Tomography ,Tomography, X-Ray Computed ,Algorithm ,Algorithms - Abstract
Tomotherapy is a dose delivery technique using helical or axial intensity modulated beams. One of the strengths of the tomotherapy concept is that it can incorporate a number of processes into a single piece of equipment. These processes include treatment optimization planning, dose reconstruction and kilovoltage/megavoltage image reconstruction. A common computational technique that could be used for all of these processes would be very appealing. The maximum likelihood estimator, originally developed for emission tomography, can serve as a useful tool in imaging and radiotherapy. We believe that this approach can play an important role in the processes of optimization planning, dose reconstruction and kilovoltage and/or megavoltage image reconstruction. These processes involve computations that require comparable physical methods. They are also based on equivalent assumptions, and they have similar mathematical solutions. As a result, the maximum likelihood approach is able to provide a common framework for all three of these computational problems. We will demonstrate how maximum likelihood methods can be applied to optimization planning, dose reconstruction and megavoltage image reconstruction in tomotherapy. Results for planning optimization, dose reconstruction and megavoltage image reconstruction will be presented. Strengths and weaknesses of the methodology are analysed. Future directions for this work are also suggested.
- Published
- 1998
34. Registration of synthetic tomographic projection data sets using cross-correlation
- Author
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J S Aldridge, Paul J. Reckwerdt, E E Fitchard, and Thomas R. Mackie
- Subjects
Biometry ,Biophysics ,Translation (geometry) ,Synthetic data ,Biophysical Phenomena ,Radiotherapy, High-Energy ,Neoplasms ,Projection method ,Humans ,Radiology, Nuclear Medicine and imaging ,Computer vision ,Projection (set theory) ,Technology, Radiologic ,Mathematics ,Radiological and Ultrasound Technology ,Pixel ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Patient registration ,Models, Theoretical ,Artificial intelligence ,Noise (video) ,Tomography ,business ,Tomography, X-Ray Computed ,Algorithms - Abstract
Tomographic registration, a method that makes possible accurate patient registration directly from projection data, consists of three processing steps: (i) manual coarse positioning, (ii) tomographic projection set acquisition, and (iii) computer mediated refined positioning. In the coarse positioning stage, the degree of patient alignment is comparable with that achieved with the standard radiotherapy set-up. However, the accuracy requirements are somewhat more relaxed in that meticulous alignment of the patient using external laser indicators is not necessary. Instead, tomographic projection sets are compared with planning CTs in order to achieve improved patient set-up. The projection sets are cross-correlated to obtain the best-fit translation and rotation offsets. The algorithm has been tested on synthetic data with the incorporation of varying amounts of Gaussian pseudo-random noise. These tests demonstrate the algorithm's stability and also confirm that alignment can be achieved with an accuracy of less than one projection pixel.
- Published
- 1998
35. An investigation of tomotherapy beam delivery
- Author
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Paul J. Reckwerdt, Bruce R. Thomadsen, James N. Yang, Joseph O. Deasy, and T. Rock Mackie
- Subjects
High energy ,medicine.medical_treatment ,Physics::Medical Physics ,Biophysics ,Cylindrical phantom ,Tomotherapy ,Imaging phantom ,Biophysical Phenomena ,Dose uniformity ,Radiotherapy, High-Energy ,Motion ,Optics ,Beam delivery ,medicine ,Dosimetry ,Humans ,Computer Simulation ,Technology, Radiologic ,Physics ,business.industry ,Phantoms, Imaging ,Radiotherapy Planning, Computer-Assisted ,Radiotherapy Dosage ,General Medicine ,Models, Theoretical ,Slit ,Evaluation Studies as Topic ,Physics::Accelerator Physics ,Nuclear medicine ,business - Abstract
Experimental simulations for tomotherapy beam delivery were performed using a computer-controlled phantom positioner, a cylindrical phantom, and a 6 MV x-ray slit beam. Both continuous helical beam and sequential segmented tomotherapy (SST) beam deliveries were evaluated. Beam junctioning problem due to couch indexing error or field width errors presented severe dose uniformity perturbations for SST, while the problem was minimized for helical beam delivery. Longitudinal breathing motions were experimentally simulated for helical and SST beam delivery. While motions reduced the dose uniformity perturbations for SST, small artifacts in dose uniformity can be introduced for helical beam delivery. With typical breath frequency and magnitude, for a slit beam of 2.0 cm width at 4 rpm, the dose uniformity perturbation was not significant. A running start/stop technique was implemented with helical beam delivery to sharpen the 20%-80% longitudinal dose fall-off from 1.5 to 0.5 cm. The latter was comparable to the corresponding dose penumbra of a conventional 6 MV 10 x 10 cm2 field. All together, helical beam delivery showed advantages over SST for tomotherapy beam delivery under similar delivery conditions.
- Published
- 1997
36. Evaluation of patient setup and plan optimization strategies based on deformable dose registration
- Author
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Gustavo H. Olivera, Robert Jeraj, R Mackie, Paul J. Reckwerdt, Jeffrey M. Kapatoes, Weiguo Lu, and K.J. Ruchala
- Subjects
Cancer Research ,medicine.medical_specialty ,Radiation ,Oncology ,business.industry ,Medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Plan (drawing) ,business - Published
- 2003
- Full Text
- View/download PDF
37. Defining the impact of beam parameters in breath-hold tomotherapy
- Author
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Robert Jeraj, Jeffrey M. Kapatoes, Thomas R. Mackie, Weiguo Lu, Paul J. Reckwerdt, Minesh P. Mehta, Kenneth J. Ruchala, and Gustavo H. Olivera
- Subjects
Cancer Research ,Radiation ,Optics ,Oncology ,business.industry ,medicine.medical_treatment ,medicine ,Radiology, Nuclear Medicine and imaging ,business ,Tomotherapy ,Beam (structure) - Published
- 2002
- Full Text
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38. The application of correlated sampling to the computation of electron beam dose distributions in heterogeneous phantoms using the Monte Carlo method
- Author
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Timothy J. Kinsella, Paul J. Reckwerdt, D W O Rogers, Thomas R. Mackie, Mark A. Holmes, W Sohn, and Alex F. Bielajew
- Subjects
Radiological and Ultrasound Technology ,Computation ,Monte Carlo method ,Sampling (statistics) ,Electrons ,Radiotherapy Dosage ,Sampling Studies ,Imaging phantom ,Computational physics ,Models, Structural ,Radiotherapy, High-Energy ,Position (vector) ,Slab ,Cathode ray ,Humans ,Radiology, Nuclear Medicine and imaging ,Monte Carlo Method ,Energy (signal processing) ,Simulation ,Mathematics - Abstract
Although the Monte Carlo method is capable of computing the dose distribution in heterogeneous phantoms directly, there are some advantages to computing a heterogeneity correction factor. If this approach is adopted there are savings in time using correlated sampling. This technique forces histories to have the same energy, position, direction and random number seed as incident on both the heterogeneous and homogeneous water phantom. This ensures that a history that has, by chance, travelled through only water in the heterogeneous phantom will have the same path as it would have through the homogeneous phantom, resulting in a reduced variance when a ratio of heterogeneous dose to homogeneous dose is formed. Metrics to describe the distributions of uncertainty, efficiency, and degree of correlation are defined. EGS4 Monte Carlo calculation of the dose distribution from a 20 MeV electron beam on water phantoms containing aluminum or air slab heterogeneities illustrate that this technique is the most efficient when the heterogeneity is deep within the phantom, but that improved efficiency can be realized even when the heterogeneity is at or near the surface. This is because some correlation between the two histories is retained despite passage through the heterogeneity.
- Published
- 1993
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39. Approaches to prostate patient setup including daily anatomy changes
- Author
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Gustavo H. Olivera, Paul J. Reckwerdt, Thomas Rockwell Mackie, K.J. Ruchala, Robert Jeraj, Jeffrey M. Kapatoes, Weiguo Lu, and John Balog
- Subjects
Gynecology ,Cancer Research ,medicine.medical_specialty ,Radiation ,medicine.anatomical_structure ,Oncology ,business.industry ,Prostate ,Medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,business - Published
- 2001
- Full Text
- View/download PDF
40. Overcoming limited field-of-view problems of on-board CT for improved radiotherapy patient positioning and dose accumulation
- Author
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Weiguo Lu, Paul J. Reckwerdt, Jeffrey M. Kapatoes, Thomas R. Mackie, Gustavo H. Olivera, and K.J. Ruchala
- Subjects
Cancer Research ,medicine.medical_specialty ,Radiation ,Dose accumulation ,business.industry ,medicine.medical_treatment ,Patient positioning ,Field of view ,On board ,Radiation therapy ,Oncology ,medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,business - Published
- 2001
- Full Text
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41. Dose gradients as a tool in the optimization and verification of intensity modulated radiation therapy (IMRT)
- Author
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H. Keller, Gustavo H. Olivera, Thomas R. Mackie, Weiguo Lu, Paul J. Reckwerdt, John Balog, and J M Kapatoes
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Cancer Research ,Radiation ,Oncology ,business.industry ,Medicine ,Radiology, Nuclear Medicine and imaging ,Intensity-modulated radiation therapy ,business ,Biomedical engineering - Published
- 2000
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42. TH-C-AUD-09: A Proposal for a Novel Compact Intensity Modulated Proton Therapy System Using a Dielectric Wall Accelerator
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James A. Purdy, R. Schmidt, D. Sanders, S.A. Hawkins, John R. Harris, J. Sullivan, A.C. Paul, J. Watson, Brian R. Poole, D. W. Pearson, D. Blackfield, C. Holmes, George J Caporaso, Y.-J. Chen, Scott D. Nelson, L. Wang, S.E. Sampayan, Paul J. Reckwerdt, M. Rhodes, Dennis L Matthews, Ryan T. Flynn, and Thomas Rockwell Mackie
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Materials science ,business.industry ,medicine.medical_treatment ,General Medicine ,Laser ,Optical switch ,Linear particle accelerator ,Tomotherapy ,Dielectric wall accelerator ,law.invention ,Acceleration ,Optics ,Nuclear magnetic resonance ,law ,Magnet ,medicine ,business ,Proton therapy - Abstract
Purpose: A novel compact CT‐guided intensity modulated protonradiotherapy (IMPT) system is introduced. The system is being designed to deliver motion‐managed IMPT to large target volumes. The system will be ideal for large and complex target volumes in young patients. Method and Materials: The basis of the design is the dielectric wall accelerator (DWA) system being developed at Lawrence Livermore National Laboratory (LLNL). The DWA will use fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved alternating insulators and conductors and short pulse times. The system will produce individual pulses that can be varied in intensity, energy and spot width, all of which will be optimized in the IMPT planning system. It is anticipated that no magnets will be required and the neutron contamination will be very low. The system will be capable of being sited in a conventional linac vault. Results: The design specifications have been met in some component tests. Gradients of 100 MV/m have been achieved in small HGI samples. Optical switches based on fast laser switched SiC has been achieved. Feasibility tests of an optimization system for selecting the position, energy, intensity and spot size for a collection of spots comprising the treatment are underway. A prototype is being designed and concept designs of the envelope and environmental needs of the unit has commenced. Conclusion: The DWA accelerator represents breakthrough technology for intensity modulated proton therapy. The system is being designed from the ground up to be capable of CT‐guided intensity modulated proton therapy and to be housed in a conventional linac vault. Conflict of Interest:Some of the authors have financial interest in TomoTherapy Inc., which has licensed the DWA technology from LLNL.
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- 2007
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43. Gating-by-rotation: a solution to the problem of intratreatment motion in helical tomotherapy
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R. Schmidt, Gustavo H. Olivera, D. W. Pearson, K.J. Ruchala, Thomas R. Mackie, Minesh P. Mehta, E A Schloesser, Paul J. Reckwerdt, Jeffrey M. Kapatoes, and John Balog
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Alternative methods ,Cancer Research ,Linear region ,Radiation ,Continuous rotation ,business.industry ,medicine.medical_treatment ,Conformal radiotherapy ,Gating ,Imaging phantom ,Collimated light ,Tomotherapy ,Oncology ,Medicine ,Radiology, Nuclear Medicine and imaging ,Nuclear medicine ,business ,Biomedical engineering - Abstract
Purpose: To assess the feasibility of addressing intratreatment motion issues in helical tomotherapy by gating the treatments by rotation. Intratreatment motion is a problem common to all IMRT techniques. Traditional methods of gating in conformal radiotherapy and some forms of IMRT are not applicable to helical tomotherapy due to the continuous rotation of the gantry. An alternative method is presented. Materials and Methods: Rotation-gating in helical tomotherapy is the process in which one rotation of treatment is immediately followed by a rotation of non-treatment. This on-off strategy is repeated for the full treatment volume. During the treatment rotations, the patient is required to hold their breath while the intensity-modulated fan beam deposits dose. For the non-treatment rotations, the patient is allowed to breathe freely as all leaves of the MLC will be closed, the accelerator disabled, or both. The couch indexes normally for treatment rotations and holds the patient stationary during non-treatment rotations. An investigation was conducted to assess the feasibility of rotation-gating. Film was placed between two hemispheres of a water phantom and a continuous helical delivery was carried out with all leaves opened. The film was replaced and another treatment was performed employing rotation-gating. The two films were compared to assess the process. The films were irradiated to dose levels within the linear region of the film response curve (maximum film dose ∼ 35 cGy). Films were also acquired with all leaves closed to quantify leakage dose through the collimation systems. Results: Central profiles for the inferior-superior direction (parallel to the direction of translation) for both films are displayed in Figure 1. The profiles agree very well, illustrating that a rotation-gated treatment closely mimics a continuous helical delivery. The only significant discrepancy lay in the tails of the profiles: a higher film dose is seen for the rotation-gated treatment as the leakage dose is higher for this delivery strategy. There are two possibilities for addressing this leakage dose: 1. it can be used to image the patient and thus provide information (albeit motion-blurred) regarding the patient position during the non-treatment rotations, 2. it can be completely removed by disabling the beam pulses during these rotations using the accelerator’s gridded-gun feature. Conclusion: Rotation-gating is a feasible solution for solving the problem of intratreatment motion in helical tomotherapy. Further studies are planned on the helical tomotherapy prototype at the University of Wisconsin. Download full-size image
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- 2001
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44. 188 Development of conformal avoidance tomotherapy in the treatment of head and neck cancer
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Thomas R. Mackie, Gustavo H. Olivera, Wolfgang A. Tomé, Paul M. Harari, M.B. Fink, J S Aldridge, and Paul J. Reckwerdt
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Cancer Research ,medicine.medical_specialty ,Radiation ,Oncology ,business.industry ,medicine.medical_treatment ,Head and neck cancer ,Medicine ,Radiology, Nuclear Medicine and imaging ,Radiology ,business ,medicine.disease ,Tomotherapy - Published
- 1999
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45. Accurate convolution/superposition for multi-resolution dose calculation using cumulative tabulated kernels.
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Weiguo Lu, Gustavo H Olivera, Ming-Li Chen, and Paul J Reckwerdt and Thomas R Mackie
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- 2005
46. Retrospective reconstruction of three dimensional radiotherapy treatment plans from two dimensional planning data
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Paul J. Reckwerdt, Timothy J. Kinsella, Timothy Holmes, Thomas R. Mackie, and S. Swerdloff
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Cancer Research ,medicine.medical_specialty ,Radiation ,Oncology ,business.industry ,medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,Conformal radiotherapy ,business ,Inverse treatment planning - Published
- 1993
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47. Tomotherapy: Inverse treatment planning for conformal radiotherapy
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Timothy Holmes, Timothy J. Kinsella, S. Swerdloff, Paul J. Reckwerdt, and Thomas R. Mackie
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Cancer Research ,medicine.medical_specialty ,Radiation ,business.industry ,medicine.medical_treatment ,Conformal radiotherapy ,Tomotherapy ,Oncology ,Medicine ,Radiology, Nuclear Medicine and imaging ,Medical physics ,business ,Radiation treatment planning ,Inverse treatment planning - Published
- 1993
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48. Gradients and intensity modulated radiotherapy
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J M Kapatoes, Thomas R. Mackie, Gustavo H. Olivera, Paul J. Reckwerdt, H. Keller, and J. Balog
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business.industry ,medicine.medical_treatment ,Planning target volume ,Intensity-modulated radiation therapy ,Tomotherapy ,Radiation therapy ,Large dose ,medicine ,Dosimetry ,Intensity modulated radiotherapy ,Nuclear medicine ,business ,Intensity modulation ,Biomedical engineering - Abstract
A consequence of the advent of intensity modulated radiation therapy (IMRT) is the presence of large dose gradients surrounding the tumor, and the regions at risk (RAR's) near the tumor. Unlike standard radiotherapy, these gradients are not the chance result of a few beam choices, but rather they are strategically placed by the optimization software. A first issue is the magnitude of these gradients. Optimal dose plans were simulated for four clinical cases using experimental helical tomotherapy optimization software. It was found that high gradients could be divided into two categories: avoidance gradients and incidental gradients. Avoidance gradients are associated with tumor/RAR boundaries and tend to be larger, on the order of 30% per cm or higher. Incidental gradients are a secondary consequence of the optimizer doing its job: placing a large amount of dose confined to the target volume. Incidental gradients tend to be on the order of 15%-20% per cm.
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