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Security personnel who operate X-ray units for the control of hand luggage and personal items at airports are generally not under dosimetric surveillance. A significant increase in the number of inspected items per passenger, due to rigorous air traffic security measures, raises a question of extended exposure of these workers to scattered X-ray radiation. A new approach to investigating directions of breaches of scattered X-ray radiation in the area near to an X-ray cabinet system, which is based on using active electronic dosemeters is presented. Influence of the increase in the number of inspected items in time on the dose rate is described. Time-dependent dose rates have showed a very good correlation with passengers undergoing security control prior to boarding an airplane. Measurements confirmed that an increase in the dose rate, coinciding with rush hours, was caused by scattered radiation passing through incompletely closed lead curtains. It is found that the doses at the entrance to the inspection tunnel are 50% higher than those at the exit, which is a consequence of inherent operational characteristics of X-ray cabinet systems.

Objective: This article will provide an assessment of the application of x-rays in the early days of radiology, which is an excellent way to come to value the convenience and safety of modern x-ray systems., Conclusion: The gas tubes that were originally applied for x-ray production were very unstable because of variations in the tube's vacuum. In an effort to understand some of the problems of these tubes and the high occupational exposure that was indirectly caused by the tubes' erratic behavior, we measured x-ray output rates as a function of the gas pressure inside the tube. The pressure range for the optimal production of x-rays, using an original Ruhmkorff inductor as a high-voltage generator, was found to be narrow. With the vacuum changing over time, this might explain the many photographs from the first years of radiology with operators watching their unshielded tube, either with bare eyes or with a fluoroscope, and their own hand as a test object. This practice often led to severe damage of the hands and to many early deaths due to cancer. Today, after a century of technologic development of x-ray tubes and associated equipment, the total average effective dose of workers in radiology can be close to natural background levels.

Scoliotic patients underwent many radiological examinations during their control and treatment periods. Nowadays, few studies have calculated effective dose which is the primary indicator of radiation risk. In this study, the PCXMC program is used to calculate the effective doses associated with scoliosis radiography. Five age groups of patients, proposed by the National Radiological Protection Board, have been chosen: <1, 1-4, 5-9, 10-15 and ≥16 y (adult patients). Patient and radiographic data were collected from 99 patient examinations for both anteroposterior and lateral full spine X-ray projections. Results showed the effective dose ranged from 118 to 1596 μSv for the frontal projection and from 97 to 1370 μSv for the lateral projection, with patient age varying from 3 months to 22 y. This study presents the effective dose against patient age and demonstrates the necessity to optimise patient protection for this type of examination.

In diagnostic radiology, the tube voltage [peak kilovoltage (kV(p))] is one of the most important parameter affecting both radiation exposure and image contrast. So, an accurate kV(p) meter is necessary to control kV(p) in the medical radiography practice with the overall uncertainty less than ± 5 % according to IEC 61676. Therefore, both invasive and non-invasive calibration methods of kV(p) meter were established and applied to different kinds of commercial quality control instruments for diagnostic radiology. Calibration of kV(p) meter by the invasive method is the most accurate (with uncertainty of 1.67 %, k=2); however, the non-invasive method also provides good results (with uncertainty of 3.12 %, k=2). Due to their detailed design, the commercial kV(p) meters have various responses with X-ray beam, so the working regime of a particular device type must be appropriately selected with a specific X-ray machine used for calibration of kV(p) meter.

X-rays were discovered by Wilhelm Röntgen in 1895. Within one year, benefits of x-rays, such as visualization of fractures, and detriments, such as x-ray dermatitis, were recognized. Nobel Laureates Pierre and Marie Sklodowska Curie discovered the radioactive element radium in 1898, and a year later the application of radiation to cure cancer was reported. A significant price was paid for this: Marie Curie died of aplastic anemia related to her radiation exposure, and her daughter Irene Joliot Curie, Nobelist for radiochemical research, died of radiation-induced leukemia. Internationally developed radiation protection recommendations were formalized starting in the late 1920s. The increasing use of ionizing radiation in medical diagnosis and radiation therapy has brought significant societal benefits. Known risks of therapeutic radiation include coronary artery disease and secondary malignancy. However, recently concerns have been raised of possible very small but incremental increases in malignancies due to diagnostic medical radiation. Patients are largely unaware of, and referring physicians and even radiologists often underestimate, the carcinogenic effects of radiation. There is a need to determine the appropriateness of imaging tests that use ionizing radiation prior to performance; optimize imaging protocols to reduce unnecessary radiation; include patients in the decision process and encourage and enable them to track their radiation exposure; and promote education about medical radiation to patients, referring physicians, radiologists, and members of the public. The basic radiation protection principles of justification, optimization, and application of dose limits still pertain.

In this paper, a seriesly connected three phase bipolar symmetrical voltage multiplier (VM) is proposed, which is a novel VM for X-ray power supply. It consists of three single phase bipolar symmetrical VM, which are connected in series at their smoothing columns. The charging and discharging process occurs six times in a cycle and the frequency of the output voltage ripple is six times as large as the drive signal frequency. The proposed VM has three times larger output voltage and three times smaller ripple factor as compared to single phase bipolar symmetrical VM, and smaller voltage drop and faster dynamic response than those of the series connected three phase symmetrical VM. The simulation is provided to show the feasibility of proposed VM.

Purpose: To develop a dynamic lesion phantom that is capable of producing physiological kinetic curves representative of those seen in human dynamic contrast-enhanced MRI (DCE-MRI) data. The objective of this phantom is to provide a platform for the quantitative comparison of DCE-MRI protocols to aid in the standardization and optimization of breast DCE-MRI., Methods: The dynamic lesion consists of a hollow, plastic mold with inlet and outlet tubes to allow flow of a contrast agent solution through the lesion over time. Border shape of the lesion can be controlled using the lesion mold production method. The configuration of the inlet and outlet tubes was determined using fluid transfer simulations. The total fluid flow rate was determined using x-ray images of the lesion for four different flow rates (0.25, 0.5, 1.0, and 1.5 ml/s) to evaluate the resultant kinetic curve shape and homogeneity of the contrast agent distribution in the dynamic lesion. High spatial and temporal resolution x-ray measurements were used to estimate the true kinetic curve behavior in the dynamic lesion for benign and malignant example curves. DCE-MRI example data were acquired of the dynamic phantom using a clinical protocol., Results: The optimal inlet and outlet tube configuration for the lesion molds was two inlet molds separated by 30° and a single outlet tube directly between the two inlet tubes. X-ray measurements indicated that 1.0 ml/s was an appropriate total fluid flow rate and provided truth for comparison with MRI data of kinetic curves representative of benign and malignant lesions. DCE-MRI data demonstrated the ability of the phantom to produce realistic kinetic curves., Conclusions: The authors have constructed a dynamic lesion phantom, demonstrated its ability to produce physiological kinetic curves, and provided estimations of its true kinetic curve behavior. This lesion phantom provides a tool for the quantitative evaluation of DCE-MRI protocols, which may lead to improved discrimination of breast cancer lesions.

The collective effective doses to the population from X-ray and nuclear medicine (NM) examinations in Finland in 2008 and 2009, respectively, were estimated. The estimated collective effective dose per inhabitant was 0.45 mSv from X-ray examinations and 0.03 mSv from NM examinations. The collective effective doses per inhabitant have not changed substantially during the last 10 y. However, proportional dose due to CT examinations has increased from 50 % in 2005 to 58 % in 2009 of the total collective effective dose from all X-ray examinations and proportional dose of PET examinations from 7 to 13 % of the total collective effective dose from NM examinations. The collective effective dose from conventional plain radiography was over 20 % higher when estimated using the new (ICRP 103) tissue weighting factors than that obtained using the old (ICRP 60) tissue weighting factors.

To identify the level of compliance with the new radiation protection regulation among Norwegian health care enterprises (HCEs). Totally, 41 HCEs were authorised to use advanced X-ray equipment for medical purposes during 2005-07. Follow-up inspections with 14 HCEs were carried out during 2007-09. Main topics for the inspections were those requirements identified as most challenging to implement in the authorisation process. Totally, 192 non-conformities with the regulation were revealed during the authorisation process. The inspections revealed that 93 % of the inspected HCEs had non-conformities with the regulation. Most common non-conformities dealt with skills in radiation protection, establishment of local diagnostic reference levels, access to medical physicists and performance of quality control of X-ray equipment. Inspections are an effective tool for implementation of regulation the requirements at the HCEs, thus improving radiation protection awareness.

The modified truncated singular value decomposition (MTSVD) unfolding method is applied to obtain primary spectra for X-ray tubes in radiodiagnostic. Three parameters - voltage, anode angle and filter thickness - of the tube are tested. Unfolded spectra are compared with theoretical extracted from IPEM-78 catalogue. A 2σ error criterion is applied to assess the minimum variations in tested parameters that permits distinguishing between close spectra., (2010 Elsevier Ltd. All rights reserved.)

Objective: Little is known about the long-term effects of exposure to diagnostic ionizing radiation in childhood. Current estimates are made with models derived mainly from studies of atomic bomb survivors, a population that differs from today's patients in many respects., Materials and Methods: We analyzed the cancer incidence among children who underwent diagnostic x-ray exposures between 1976 and 2003 in a large German university hospital. We reconstructed individual radiation doses for each examination and sorted results by groups of referral criteria for all cancers combined, solid tumors, and leukemia and lymphoma combined., Results: A total of 68 incidence cancer cases between 1980 and 2006 were identified in a 78,527-patient cohort in the German childhood cancer registry: 28 leukemia, nine lymphoma, six tumors of the CNS, and 25 other tumors. The standardized incidence ratio for all cancers was 0.97 (95% CI, 0.75-1.23). Dose-response relations were analyzed by multivariable Poisson regression. Although the cancer incidence risk differed by initial referral criterion for radiographic examination, a positive dose-response relation was observed in five patients with endocrine or metabolic disease., Conclusion: Overall, we observed no increase in cancer risk among children and youths with very low radiation doses from diagnostic radiation, which is compatible with model calculations. The growing use of CT warrants further studies to assess associated cancer risk. Our work is an early contribution of epidemiologic data for quantifying these risks among young patients.

Purpose: To compare the antiquated x-ray system of Hoffmans and van Kleef (circa 1896) with modern x-ray equipment in terms of radiation dose, x-ray beam properties, image quality, and electrical parameters., Materials and Methods: The antiquated x-ray system consisted of a Ruhmkorff inductor, battery, and Crookes tube. The radiation dose rate, x-ray beam properties, and electrical characteristics of this system were determined. A modern computed radiography plate was used to compare images of a hand specimen obtained by using the antiquated system with images obtained by using the modern system., Results: A peak voltage of 73 kV was obtained with an 8-V battery. With Crookes tube number 9, the half-value layer of the generated x-rays was 0.56 mm Al. Pinhole images showed that the x-rays originated from an extended area of the glass wall, causing image blurring. When measured on the skin of a hand specimen, the radiation dose of the antiquated system was about 10 times greater than that of the modern system for the same detector signal. The estimated skin dose was about 74 mGy for the antiquated system and 0.05 mGy for the modern system. The corresponding exposure times were 90 minutes and 21 msec., Conclusion: Radiation dose and exposure time of the antiquated system were greater than those of the modern system by about three and five orders of magnitude, respectively. Images of the hand specimen obtained with the antiquated system were severely blurred but were still awe inspiring, considering the simplicity of the system., Supplemental Material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101899/-/DC1., (RSNA, 2011)

Purpose: This paper describes a noniterative estimator for the energy dependent information from photon counting detectors with multibin pulse height analysis (PHA). The estimator uses the two function decomposition of the attenuation coefficient [R. E. Alvarez and A. Macovski, Phys. Med. Biol. 21, 733-744 (1976)] and its output is the line integrals of the basis set coefficients. The output noise variance and bias is compared to other noniterative estimators and to the Cramèr-Rao lower bound (CRLB)., Methods: The estimator first computes an initial estimate from a linearized maximum likelihood estimator. The errors in the initial estimates are determined at a set of points from measurements on a calibration phantom. The errors at these known points are interpolated to create two-dimensional look up tables of corrections to the initial estimates. During image acquisition, the linearized maximum likelihood estimate for each data point is used as an input to the correction look up tables, and the final output is the sum of the estimate and the correction. The performance of the estimator is compared to generalizations of the polynomial and rational polynomial estimators for multibin data. The estimators are compared by the mean square error (MSE) and its components, the bias, and the variance of the output. The variance is also compared to the CRLB. The performance is simulated with two to five bins PHA data. The CRLB at a fixed object thickness is also computed as a function of the number of bins., Results: For two bin data, all the estimators' variances are equal to the CRLB. With three or more bins, only the proposed estimator achieves the CRLB while the others, which were not optimized for noise performance, have much larger output variance. The bias of the proposed estimator is equal to the polynomial estimator for calibration phantoms with 40 or more steps, that is, 1600 combinations of basis materials, but is larger than the rational polynomial bias. In all cases at the photon counts tested, the MSE is essentially equal to the variance, indicating that the bias errors are negligible compared to the variance., Conclusions: The estimator provides a noniterative method to compute the energy dependent information from multibin PHA data that achieves the CRLB over a wide range of operating conditions and has low output bias. The estimator can be calibrated based on the measurements of a calibration phantom; so, it does not require measurements of the x-ray energy spectrum or the detector response functions.

The imaging sensitivity of proton radiography has been studied and compared with kV and MV x-ray imaging using Monte Carlo simulations. A phantom was specifically modeled using 21 different material inserts with densities ranging from 0.001 to 1.92 g cm(-3). These simulations were run using the MGH double scattered proton beam, scanned pencil proton beams from 200 to 490 MeV, as well as pure 50 keV, 100 keV, 1 MeV and 2 MeV gamma x-ray beams. In order to compare the physics implied in both proton and photon radiography without being biased by the current state of the art in detector technology, the detectors were considered perfect. Along with spatial resolution, the contrast-to-noise ratio was evaluated and compared for each material. These analyses were performed using radiographic images that took into account the following: only primary protons, both primary and secondary protons, and both contributions while performing angular and energetic cuts. Additionally, tissue-to-tissue contrasts in an actual lung cancer patient case were studied for simulated proton radiographs and compared against the original kV x-ray image which corresponds to the current patient set-up image in the proton clinic. This study highlights the poorer spatial resolution of protons versus x-rays for radiographic imaging purposes, and the excellent density resolution of proton radiography. Contrasts around the tumor are higher using protons in a lung cancer patient case. The high-density resolution of proton radiography is of great importance for specific tumor diagnostics, such as in lung cancer, where x-ray radiography operates poorly. Furthermore, the use of daily proton radiography prior to proton therapy would ameliorate patient set-up while reducing the absorbed dose delivered through imaging.

A joint project between the Paul Scherrer Institut (PSI) and the Institute of Radiation Physics was initiated to characterise the PSI whole body counter in detail through measurements and Monte Carlo simulation. Accurate knowledge of the detector geometry is essential for reliable simulations of human body phantoms filled with known activity concentrations. Unfortunately, the technical drawings provided by the manufacturer are often not detailed enough and sometimes the specifications do not agree with the actual set-up. Therefore, the exact detector geometry and the position of the detector crystal inside the housing were determined through radiographic images. X-rays were used to analyse the structure of the detector, and (60)Co radiography was employed to measure the core of the germanium crystal. Moreover, the precise axial alignment of the detector within its housing was determined through a series of radiographic images with different incident angles. The hence obtained information enables us to optimise the Monte Carlo geometry model and to perform much more accurate and reliable simulations.

Orthopedic and especially trauma surgeons' use of x-rays during operations vary extensively, especially in minimally invasive osteosynthesis procedures. Radiation hazards often are neglected. In this paper, a short overview of physical and biological effects of radiation are given. In addition, practical information about how to lower radiation exposure in the daily work in the operating room (OR) is given. The operating team is exposed mainly to scattered radiation. The radiation exposure is 10 times higher on the tube side than on the amplifier side. The distance between tube and surgeon must be as great as possible. The tube should be positioned under the OR table, and the distance between tube and patient should be as short as possible. The positioning of the C-arm device without radiation is important. The use of patient landmarks is used to position the C-arm over the region of interest, but the preoperative training of surgeons and team with virtual learning tools, e.g., virtX, is very effective in reducing radiation hazards.

Introduction: Radiation was discovered just slightly more than a century ago, with a profound effect on both industry and medicine. Several notable scientists were key in bringing radiation to the forefront., Methods: Historical review of scientists who played key roles in the discovery of radiation and its use in medicine are reviewed., Results: Wilhelm Roentgen, Henri Becquerel, and Marie and Pierre Curie's work is reviewed. The field of radiation safety was born to protect those handling radiation in addition to patients who received radiation for medical purposes., Conclusion: Radiation use in medicine continues to evolve after notable discoveries by Nobel Prize-winning scientists., (Copyright © 2011 Society for Vascular Surgery. Published by Mosby, Inc. All rights reserved.)

This paper presents a new approach for reconstructing a patient-specific shape model and internal relative intensity distribution of the proximal femur from a limited number (e.g., 2) of calibrated C-arm images or X-ray radiographs. Our approach uses independent shape and appearance models that are learned from a set of training data to encode the a priori information about the proximal femur. An intensity-based non-rigid 2D-3D registration algorithm is then proposed to deformably fit the learned models to the input images. The fitting is conducted iteratively by minimizing the dissimilarity between the input images and the associated digitally reconstructed radiographs of the learned models together with regularization terms encoding the strain energy of the forward deformation and the smoothness of the inverse deformation. Comprehensive experiments conducted on images of cadaveric femurs and on clinical datasets demonstrate the efficacy of the present approach.

As one type of basic physical data related to the calculation of the construction of X-ray examination room shielding, we investigated the air-kerma rate 1 m from the source of the useful beam focus per unit current time product. Compared to the X-ray energy penetration values obtained in prior research, we obtained higher values. We found three causes for this discrepancy: (1) the X-ray tube total filtration (increasing total filtration reduces air kerma), (2) the tube voltage ripple percentage (increased voltage ripple reduces air kerma, and (3) the target angle (increasing the target angle increases the air kerma). On standardizing (1)-(3), we confirmed that our values mostly matched those obtained in past research. Consequently, when one employs the air-kerma rate that results from the consideration of (1)-(3), without pursuing a path of excessive safety, calculation of shielding under clinical conditions is possible.

For physical foundation data used in the shielding calculation of structural facilities such as a radiation room, there are air kerma transmissions concerning the thickness of shielding objects, and half value layers and tenth value layers concerning a greatly attenuated wide X-ray beam. Accordingly, we evaluated the above-mentioned items with a lead-free board, which is mixed sulfuric acid calcium and barium sulfate with equiponderance for the amount of sulfuric acid calcium included in the usual plasterboard. Permeability in NCRP Report 147 is expressed by 3 parameters, α, β and γ, and shielding objects x. It showed that it corresponds to the measurement point and permeability curve with parameters, α, β and γ obtained by nonlinear regression analysis. Furthermore, we calculated the half value layer and tenth value layer concerning the greatly attenuated wide X-ray beam. The evaluated lead-free board, used in this examination, is useful as the shielding material for the diagnosis X-ray and, moreover, the partition wall materials are hard enough, with a board that is even heavier than the usual plaster board. Besides, the use of lead-free materials is friendly to the general environment.

Hydrogels have shown promise for a number of tissue engineering applications. However, their high water content results in little or no image contrast when using conventional X-ray imaging techniques. X-ray imaging techniques based on phase-contrast have shown promise for biomedical application due to their ability to provide information about the X-ray refraction properties of samples. Nonporous and porous poly(ethylene glycol) hydrogels were synthesized and imaged using a synchrotron light source employing a silicon analyzer crystal and an X-ray energy of 40-keV. Data were acquired at 21 angular analyzer positions spanning the range of -5 to 5 μrad. Images that depict the projected X-ray absorption, refraction, and ultra-small-angle scatter (USAXS) properties of the hydrogels were reconstructed from the measurement data. The poly(ethylene glycol) hydrogels could be discerned from surrounding water and soft tissue in the refraction image but not the absorption or USAXS images. In addition, the refraction images of the porous hydrogels have a speckle pattern resulting in increased image texture in comparison to nonporous hydrogels. To our knowledge, this is the first study to show that X-ray phase-contrast imaging techniques can identify and provide detail on hydrogel structure without the addition of contrast agents.

Purpose: Spectral and angular distribution of the x-ray beam generated by medical x-ray tubes as a function of anode surface roughness was analyzed., Methods: Different sets of profiles such as ideal flat, regular profiles, and measured profiles adopted from the literature were analyzed by means of MCNPX Monte Carlo simulator. The geometry used was simplified to separate different physical effects. A sphere centered on the origin of the coordinate system was divided into two hemispheres filled with tungsten and a vacuum, respectively. The studied anode surfaces were placed at the center of the plane of the hemisphere. The profiles were realized by means of the general lattice structure of the MCNPX. The energy and angular distributions of the excited photons were recorded with energy and angular resolutions of 0.5 keV and 1 degrees, respectively, by means of point detectors. The range of the studied anode surface roughness was 0-550 micro Ra. The emission angle dependencies of the following quantities were analyzed: Half value layer (HVL) value, intensity, and spectral photon flux., Results: The analysis of the HVL of the x-ray beam showed that around an emission angle of 5 degrees, the hardness of the beam was practically independent of the surface roughness. The value of this emission angle depends on the filtration. Below this critical angle, the HVL value decreases, while at a higher emission angle, the beam becomes harder with increasing surface roughness. The intensity degradation saturates with increasing roughness. The position of the maximum spectral photon flux shifts to higher emission angles as the anode surface roughness increases. The surface roughness (Ra) was found to be an inadequate quantity to describe the effect of anode surface roughness on x-ray spectra since no definite connection was found between the values of the intensity degradation and surface roughness. At 120 kVp tube voltage and at a 3.84 microm Ra roughness value, the effect of anode surface roughness introduces a 5% and 12% intensity degradation at a 5 degrees and 12 degrees emission angle, respectively. However, it has a higher impact at low tube voltages (<60 keV), e.g., in mammography systems where the intensity degradation could even be 25% at the "newly" polished anode surface., Conclusions: The effects of anode surface roughness on x-ray spectra were successfully simulated by a Monte Carlo method. It was proved that the effect of the anode surface roughness could not be modeled by simple filters made from the anode material. The surface roughness (Ra) was found to be an inadequate quantity to describe the effect of anode surface roughness on x-ray spectra.

Due to the fact that Röntgen never reported the details of the discovery of his "new rays", he left the door open for speculative interpretations. As a contribution to a serious analysis of the history of Röntgen's discovery, this paper presents a previously unnoticed letter relating to an order of a number of very thin crystalline absorbers. The addressee is unfortunately unknown. The letter is dated November 15, 1895. Therefore, this letter must be considered to be the first well documented remark made by Röntgen after seeing the earliest indications of the new rays only one week earlier. The order seems to emphasize the role of a particular type of cathode ray tube developed by Philipp Lenard, Nobel Prize winner of 1905, and manufactured by the glassblower Louis Müller-Unkel in the discovery of the new radiation. It partly contradicts an analysis based on Röntgen's order book from Würzburg made by the author et al. some years ago. Completed by the document presented here, Röntgen's order correspondence allows some insight into Röntgen's intentions during this productive period. The autograph was found at Staatsbibliothek Berlin, Sammlung Darmstaedter, by the author., (© Georg Thieme Verlag KG Stuttgart · New York.)

X-rays have long been a precious tool for the study of the structure of matter. While the short wavelength makes them ideal for investigating materials down to the atomic scale, their high penetration power allows for the exploration of opaque samples at a multitude of length scales. We give an overview of the x-ray techniques suited for the characterization of soft matter and of their application to systems of current interest. We describe the advantages and limitations of existing x-ray methods and outline the possible developments following the introduction of a new kind of coherent source: the x-ray free electron laser.

Purpose: Recently, novel CdTe photon counting x-ray detectors (PCXDs) with energy discrimination capabilities have been developed. When such detectors are operated under a high x-ray flux, however, coincident pulses distort the recorded energy spectrum. These distortions are called pulse pileup effects. It is essential to compensate for these effects on the recorded energy spectrum in order to take full advantage of spectral information PCXDs provide. Such compensation can be achieved by incorporating a pileup model into the image reconstruction process for computed tomography, that is, as a part of the forward imaging process, and iteratively estimating either the imaged object or the line integrals using, e.g., a maximum likelihood approach. The aim of this study was to develop a new analytical pulse pileup model for both peak and tail pileup effects for nonparalyzable detectors., Methods: The model takes into account the following factors: The bipolar shape of the pulse, the distribution function of time intervals between random events, and the input probability density function of photon energies. The authors used Monte Carlo simulations to evaluate the model., Results: The recorded spectra estimated by the model were in an excellent agreement with those obtained by Monte Carlo simulations for various levels of pulse pileup effects. The coefficients of variation (i.e., the root mean square difference divided by the mean of measurements) were 5.3%-10.0% for deadtime losses of 1%-50% with a polychromatic incident x-ray spectrum., Conclusions: The proposed pulse pileup model can predict recorded spectrum with relatively good accuracy.

Purpose: Monte Carlo simulation is a very useful tool for radiotherapy and diagnostic radiology. Yet even with the latest PCs, simulation of photon spectra emitted by an x-ray tube is a time-consuming task, potentially reducing the possibility to obtain relevant data such as dose evaluations, simulation of geometric settings, or monitor detector efficiency. This study developed and validated a method to generate random numbers for realistic beams in terms of photon spectrum and intensity to simulate x-ray tubes via Monte Carlo algorithms., Methods: Starting from literature data, the most common semiempirical models of bremsstrahlung are analyzed and implemented, adjusting their formulation to describe a large irradiation area (i.e., large field of view) and to take account of the heel effect as in common practice during patient examinations., Results: Simulation results show that Birch and Marshall's model is the fastest and most accurate for the aims of this work. Correction of the geometric size of the beam and validation of the intensity variation (heel effect) yielded excellent results with differences between experimental and simulated data of less than 6%., Conclusions: The results of validation and execution time showed that the tube simulator calculates the x-ray photons quickly and efficiently and is perfectly capable of considering all the phenomena occurring in a real beam (total filtration, focal spot size, and heel effect), so it can be used in a wide range of applications such as industry, medical physics, or quality assurance.

We present a method for high-resolution magnetic imaging at linearly polarized partially coherent x-ray sources. The magnetic imaging was realized via Fourier transform holography. In order to achieve elliptical x-ray polarization, three different filters were designed based on the x-ray magnetic circular dichroism effect. We present proof-of-principle images of magnetic nanostructures and discuss the application of the method for future experiments at free-electron laser sources.

We introduce a novel x-ray imaging approach that yields information about the local texture of structures smaller than the image pixel resolution inside an object. The approach is based on a recently developed x-ray dark-field imaging technique, using scattering from sub-micron structures in the sample. We show that the method can be used to determine the local angle and degree of orientation of bone, and fibers in a leaf. As the method is based on the use of a conventional x-ray tube we believe that it can have a great impact on medical diagnostics and non-destructive testing applications.

Purpose: The aim of this article is to investigate the feasibility of using a statistical shape model (SSM)-based reconstruction technique to derive a scaled, patient-specific surface model of the pelvis from a single standard anteroposterior (AP) x-ray radiograph and the feasibility of estimating the scale of the reconstructed surface model by performing a surface-based 3D/3D matching., Methods: Data sets of 14 pelvises (one plastic bone, 12 cadavers, and one patient) were used to validate the single-image based reconstruction technique. This reconstruction technique is based on a hybrid 2D/3D deformable registration process combining a landmark-to-ray registration with a SSM-based 2D/3D reconstruction. The landmark-to-ray registration was used to find an initial scale and an initial rigid transformation between the x-ray image and the SSM. The estimated scale and rigid transformation were used to initialize the SSM-based 2D/3D reconstruction. The optimal reconstruction was then achieved in three stages by iteratively matching the projections of the apparent contours extracted from a 3D model derived from the SSM to the image contours extracted from the x-ray radiograph: Iterative affine registration, statistical instantiation, and iterative regularized shape deformation. The image contours are first detected by using a semiautomatic segmentation tool based on the Livewire algorithm and then approximated by a set of sparse dominant points that are adaptively sampled from the detected contours. The unknown scales of the reconstructed models were estimated by performing a surface-based 3D/3D matching between the reconstructed models and the associated ground truth models that were derived from a CT-based reconstruction method. Such a matching also allowed for computing the errors between the reconstructed models and the associated ground truth models., Results: The technique could reconstruct the surface models of all 14 pelvises directly from the landmark-based initialization. Depending on the surface-based matching techniques, the reconstruction errors were slightly different. When a surface-based iterative affine registration was used, an average reconstruction error of 1.6 mm was observed. This error was increased to 1.9 mm, when a surface-based iterative scaled rigid registration was used., Conclusions: It is feasible to reconstruct a scaled, patient-specific surface model of the pelvis from single standard AP x-ray radiograph using the present approach. The unknown scale of the reconstructed model can be estimated by performing a surface-based 3D/3D matching.

Skin entrance doses (SEDs) were estimated by carrying out measurements of air kerma from 101 X-ray machines installed in 45 major and selected hospitals in the country by using a silicon detector-based dose Test-O-Meter. 1209 number of air kerma measurements of diagnostic projections for adults have been analysed for seven types of common diagnostic examinations, viz. chest (AP, PA, LAT), lumbar spine (AP, LAT), thoracic spine (AP, LAT), abdomen (AP), pelvis (AP), hip joints (AP) and skull (PA, LAT) for different film-screen combinations. The values of estimated diagnostic reference levels (DRLs) (third quartile values of SEDs) were compared with guidance levels/DRLs of doses published by the IAEA-BSS-Safety Series No. 115, 1996; HPA (NRPB) (2000 and 2005), UK; CRCPD/CDRH (USA), European Commission and other national values. The values of DRLs obtained in this study are comparable with the values published by the IAEA-BSS-115 (1996); HPA (NRPB) (2000 and 2005) UK; EC and CRCPD/CDRH, USA including values obtained in previous studies in India.

The Imaging and Medical beamline at the Australian Synchrotron achieved ;first light' in December 2008. Here, the first experiments performed on the beamline are reported, which involved both X-ray imaging and tomography studies for a range of samples. The use of a plastic-edge phantom for quantitative measurements of contrast and resolution proved to be very instructive and helped to confirm certain parameter values such as the effective horizontal source size, detector resolution and average X-ray energy for the polychromatic beam.

Cardiovascular disease affects millions of Americans each year. Interventional guidance systems are being developed as treatment options for some of the more delicate procedures, including targeted stem cell therapy. As advanced systems for such types of interventional guidance are being developed, electromagnetic (EM) tracking is coming in demand to perform navigation. To use this EM tracking technology, a calibration is necessary to register the tracker to the imaging system. In this paper we investigate the calibration of an X-ray imaging system to EM tracking. Two specially designed calibration phantoms have been designed for this purpose, each having a rigidly attached EM sensor. From a clinical usability point-of-view, we propose to divide this calibration problem into two steps: i) in initial calibration of the EM sensor to the phantom design using an EM tracked needle to trace out grooves in the phantom surface and ii) segmentation from X-ray images and 3D reconstruction of beads embedded in the phantom in a known geometric pattern. Combining these two steps yields and X-ray-to-EM calibration accuracy of less than 1 mm when overlaying an EM tracked needle on X-ray images.

A thorough knowledge of the primary spectrum is very important for Quality Control (QC) of X-ray tubes. A methodology to assess primary spectrum using a Compton spectrometer has been simulated with the MCNP5 code based on the Monte Carlo (MC) method. The Pulse Height Distribution (PHD) recorded in the detector is related with the primary X-ray spectrum by means of a Response matrix. Tikhonov and Modified Truncated Singular Values Decomposition (MTSVD) unfolding methods have been applied to the Response matrix to assess the primary spectrum. Both methods are tested comparing unfolded results with theoretical spectra from IPEM-78 catalogue.

Purpose: The purpose of this work was to investigate the effect of characteristic x rays on the performance of photon counting detectors for multienergy x-ray imaging. X-ray and CT systems with photon counting detectors have compelling advantages compared to energy integrating detectors, and cadmium zinc telluride (CZT) detector is the detector of choice. However, current CZT detectors exhibit several limitations that hamper their practical applications. These limitations include hole trapping, high leakage current, and charge sharing between detector pixels. Charge sharing occurs due to the diffusion of charge when it drifts toward the pixel electrodes. It also occurs due to nonlocal reabsorption of characteristic and scattered x rays created in the detector volume. Hole trapping, leakage current, and charge diffusion may potentially have technical solutions. Characteristic x-ray escape and scatter, however, are fundamental in nature and cannot be easily addressed. The x-ray scatter in the CZT material is small at photon energies used in x-ray imaging. Therefore, the remaining major factor is characteristic x ray., Methods: Monte Carlo simulations were used for this study. An experimental photon counting multienergy x-ray imaging system was used to compare simulations to experimental results. An x-ray spectrum at 120 kVp tube voltage was used. The x-ray energy range was split into five subregions (energy bins) and Monte Carlo simulations were performed at average x-ray energies corresponding to these energy bins. The detector pixel size was changed within the 0.1-1 mm range, which covered all possible applications including radiography and CT imaging. The pixel shapes included square and strip pixels. For strip pixels, tilted angle irradiation of the CZT detector was also investigated., Results: The characteristic x rays escaped the pixels in approximately 70% of all x-ray interactions for the smallest pixel size of 0.1 mm. The escape fraction decreased to 20% for the largest pixel size of 1 mm. All escape fractions, for all pixel sizes, at five energies, for square and strip pixels, and at three tilt angles were calculated and presented in tables. Simulated and measured spectra at 120 kVp were compared., Conclusions: Characteristic x-ray escape deteriorates energy and spatial resolution, particularly for small pixel sizes. Correction methods should be developed based on the results of the simulations and experimental study.

The quality assurance (QA) of radiographic images based on the operating conditions of X-ray equipment is essential for good image quality, accurate medical diagnostics and for the prevention of health professionals and patients to unnecessary doses of ionizing radiation. This paper presents a historical analysis of 1,635 Quality Assurance Technical Reports of Health Institutions in the state of São Paulo, Brazil, over a seven-year period. Based on acceptable limits for variations between nominal and measured parameters as the variable to determine the quality of X-ray equipment operating conditions, a significant improvement was found in the percentage of acceptance of the overall parameters described in the QA technical reports over this period. As expected, we found a strong concentration in the categories of conventional and portable X-ray equipment, which represent 72% and 84%, respectively, of the total number of equipments. A mechanical parameter such as half-value layer (HVL), which is important not only for image quality but also for radiation protection, showed significant improvements. Again, only 58% of portable X-ray equipment showed HVL values recommended for 80 kVp (above 2.3 mm Al), a percentage that improved to 76% in 2006. With regard to mammographers, which are newer machines, all the analyzed systems presented acceptable HVL values. Conventional X-ray machines showed an increase of this conformity index from 89% in 2000 to 94% in 2006. All this improvement was attributed to the continuous and extensive enforcement of Regulation Act 453 in the state of São Paulo. The improvement in equipment quality control standards is expected to result in the improvement of diagnostic quality, as well as in the reduction of exam repetitions, and thereby reducing the patient's exposure to radiation.

Purpose: A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x rays emitted from thin targets, irradiated by electron beams circulating in the storage ring, is of primary interest for the design and the characterization of a beamline. This article, Part I, aims at optimizing some of the parameters which are critical for the design of medical applications based on the above compact light source. The goal was to evaluate the dependence of photon fluence and beam monochromaticity on electron-beam energy, target material, and thickness., Methods: The transport of 6 and 20 MeV electrons in a thin molybdenum, rhodium, and tungsten target is studied by means of Monte Carlo simulations using MCNPX. Configurations of the x-ray output port, different from the default forward-directed emission of the beam, are also investigated. A comparison with reference spectra for general diagnostic radiology and mammography is carried out., Results: It is shown that the emitted x-ray beams can be far more intense than those generated by conventional x-ray tubes for radiography applications. The profiles of the calculated polychromatic spectra resemble those generated by conventional x-ray tubes, with x-ray energies up to the energy of the incident-electron beam. An appreciable improvement in the monochromaticity of the beams can be obtained by viewing the x-ray emission from an output port antiparallel to the direction of the incident-electron beam., Conclusions: The optimum target thickness for tungsten target spectra is practically constrained by a trade-off between bremsstrahlung efficiency and focal-spot size requirements. A larger margin for optimization of target thickness is probably available for mammographic spectra. The constraint of a backward-directed (or, to a lesser extent, orthogonal) output port is to be considered mandatory for minimizing the high-energy tail of the spectral distribution and keeping the radiation dose to a reasonable level. It is also fundamental to evaluate the impact of the high-energy tail of the emitted spectra in x-ray imaging applications, since the energy range involved is significantly beyond the diagnostic range. This topic will be dealt with in Part II of the article.

Wilhelm Roentgen (1845-1923) created a surgical revolution with the discovery of the X-rays in late 1895 and the subsequent introduction of this technique for the management of surgical patients. No other physician or scientist had ever imagined such a powerful and worthwhile discovery. Other scientists paved the way for Roentgen to approach the use of these new X-rays for medical purposes. In this way, initially, and prior to Roentgen, Thompson, Hertz, and Lenard applied themselves to the early developments of this technology. They made good advances but never reached the clearly defined understanding brought about by Roentgen. The use of a Crookes tube, a barium platinocyanide screen, with fluorescent light and the generation of energy to propagate the cathode rays were the necessary elements for the conception of an X-ray picture. On November 8, 1895, Roentgen began his experiments on X-ray technology when he found that some kind of rays were being produced by the glass of the tube opposite to the cathode. The development of a photograph successfully completed this early imaging process. After six intense weeks of research, on December 22, he obtained a photograph of the hand of his wife, the first X-ray ever made. This would be a major contribution to the world of medicine and surgery.

Purpose: A new concept of indirect conversion flat-panel imager with avalanche gain and field emitter array (FEA) readout is being investigated. It is referred to as scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The present work investigates the temporal performance, i.e., lag, of SAPHIRE., Methods: Since the temporal performance of the x-ray detection materials, i.e., the structured scintillator and avalanche amorphous selenium (a-Se) photoconductor, has been studied previously, the investigation is focused on lag due to the FEA readout method. The principle of FEA readout is similar to that of scanning electron beam readout used in camera tubes, where the dominant source of lag is the energy spread of electrons. Since the principles of emission and beam focusing methods for FEA are different from thermionic emission used in camera tubes, its electron beam energy spread and hence lag is expected to be different. In the present work, the energy spread of the electrons emitted from a FEA was investigated theoretically by analyzing different contributing factors due to the FEA design and operations: The inherent energy spread of field emission, the FEA driving pulse delay, and the angular distribution of emitted electrons. The electron energy spread determined the beam acceptance characteristic curve of the photoconductive target, i.e., the accepted beam current (I(a)) as a function of target potential (V(t)), from which lag could be calculated numerically. Lag calculation was performed using FEA parameters of two prototype HARP-FEA image sensors, and the results were compared with experimental measurements. Strategies for reducing lag in SAPHIRE were proposed and analyzed., Results: The theoretical analysis shows that the dominant factor for lag is the angular distribution of electrons emitted from the FEA. The first frame lags for two prototype sensors with 4 and 25 microm HARP layer thicknesses were 62.1% and 9.1%, respectively. A lag clearance procedure can be implemented by turning on all the FEA pixels simultaneously between subsequent frames without negative impact of readout speed. For large-area SAPHIRE, the bias electrode for the HARP needs to be divided into strips to allow parallel readout. With typical cardiac detector parameters, SAPHIRE with 128 parallel strips can provide real-time readout (30 frames/s) with first frame lag of -4%., Conclusions: The investigation of lag in SAPHIRE shows that the angular distribution of emitted electrons from FEA can result in substantial lag if the readout was performed pixel by pixel. Effective strategies for reducing lag include dividing the bias electrode into multiple strips to allow parallel readout and the incorporation of rapid charge clearance procedure between subsequent frames or rows.

This study examined the feasibility of applying the bubble technique to evaluate effective dose for diagnostic X-rays. A BTI-GAMMA bubble detector from Bubble Technology Industries was used for gamma detection. A multi-slab acrylic (PMMA) phantom was fabricated to quantify the effective dose E based on an ICRP-60 report. Accordingly, the bubble detectors were evaluated through preliminary tests to ascertain both the reproducibility of specific X-ray doses and the linearity of multiple X-ray doses. Qualified bubble detectors were then inserted into a multi-slab acrylic phantom. The positions of the inserted bubbles closely corresponded with the position of represented organs or tissues. The effective dose E of X-ray was determined in 12 organ and tissue samples. The bubble detector was maintained at either 21.5 degrees C (for abdomen AP) or 22 degrees C (for chest PA) to optimize counting, and the assessed effective doses for males and females were 66.75 +/- 10.23 microSv and 66.47 +/- 9.89 microSv, respectively, for each chest PA X-ray exposure. The abdominal AP X-ray exposure doses were 1183.73 +/- 124.29 microSv and 976.70 +/- 120.13 microSv for males and females, respectively. Controlling and holding the bubble detector at an optimal ambient temperature during X-ray exposure was the most important issue in practical application, and the optimal temperature had to be adjusted slightly with incident X-ray to effectively suppress the largest bubbles to enable easy reading.

At present, only a correction factor for photon transmission, k(l), is systematically applied for the entrance diaphragm of free-air chamber standards for air kerma. In the present work, the Monte Carlo code PENELOPE is used to re-evaluate k(l) for the BIPM standards and new correction factors are calculated for photon scatter and for fluorescence production in the diaphragm. An additional effect arising from electrons emitted from the diaphragm is shown to be significant at the highest photon energies. The results for the radiation qualities used for international comparisons give a combined diaphragm correction factor k(dia) = 0.9980(3) for the BIPM medium-energy standard at 250 kV. This is significantly different from the factor k(l) = 0.9996(1) in use at present and it might be concluded that differences are likely to exist for all free-air chamber standards. The effect of using a conical taper at the downstream edge of the diaphragm is shown to be negligible for these radiation qualities.