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213 results on '"Mawlawi O"'

1. The first probe of a FLASH proton beam by PET

Author

Abouzahr, F, primary, Cesar, J P, additional, Crespo, P, additional, Gajda, M, additional, Hu, Z, additional, Klein, K, additional, Kuo, A S, additional, Majewski, S, additional, Mawlawi, O, additional, Morozov, A, additional, Ojha, A, additional, Poenisch, F, additional, Proga, M, additional, Sahoo, N, additional, Seco, J, additional, Takaoka, T, additional, Tavernier, S, additional, Titt, U, additional, Wang, X, additional, Zhu, X R, additional, and Lang, K, additional

Published
2023
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3. The first PET glimpse of a proton FLASH beam.

Author

Abouzahr, F, Cesar, J P, Crespo, P, Gajda, M, Hu, Z, Kaye, W, Klein, K, Kuo, A S, Majewski, S, Mawlawi, O, Morozov, A, Ojha, A, Poenisch, F, Polf, J C, Proga, M, Sahoo, N, Seco, J, Takaoka, T, Tavernier, S, and Titt, U

Subjects
PROTON beams, PHOTOMULTIPLIERS, MONTE Carlo method, POSITRON emission tomography, MEDICAL dosimetry, PROTON therapy
Abstract

We demonstrate the first ever recorded positron-emission tomography (PET) imaging and dosimetry of a FLASH proton beam at the Proton Center of the MD Anderson Cancer Center. Two scintillating LYSO crystal arrays, read out by silicon photomultipliers, were configured with a partial field of view of a cylindrical poly-methyl methacrylate (PMMA) phantom irradiated by a FLASH proton beam. The proton beam had a kinetic energy of 75.8 MeV and an intensity of about 3.5 × 1010 protons that were extracted over 101.5 ms-long spills. The radiation environment was characterized by cadmium–zinc–telluride and plastic scintillator counters. Preliminary results indicate that the PET technology used in our tests can efficiently record FLASH beam events. The instrument yielded informative and quantitative imaging and dosimetry of beam-activated isotopes in a PMMA phantom, as supported by Monte Carlo simulations. These studies open a new PET modality that can lead to improved imaging and monitoring of FLASH proton therapy. [ABSTRACT FROM AUTHOR]

Published
2023
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9. Towards a standard for the evaluation of PET Auto-Segmentation methods: requirements and implementation

Author

Berthon, B, Spezi, E, Galavis, P, Shepherd, T, Apte, A, Hatt, M, Fayad, H, De Bernardi, E, Soffientini, C, Schmidtlein, C, El Naqa, I, Jeraj, R, Lu, W, Das, S, Zaidi, H, Mawlawi, O, Visvikis, D, Lee, J, Kirov, A, Berthon, B, Spezi, E, Galavis, P, Shepherd, T, Apte, A, Hatt, M, Fayad, H, De Bernardi, E, Soffientini, C, Schmidtlein, C, El Naqa, I, Jeraj, R, Lu, W, Das, S, Zaidi, H, Mawlawi, O, Visvikis, D, Lee, J, and Kirov, A

Subjects
segmentation, Positron Emission Tomography
Abstract

Purpose The aim of this paper is to define the requirements and describe the design and implementation of a standard benchmark tool for evaluation and validation of PET-auto-segmentation (PET-AS) algorithms. This work follows the recommendations of Task Group 211 (TG211) appointed by the American Association of Physicists in Medicine (AAPM). Methods The recommendations published in the AAPM TG211 report were used to derive a set of required features and to guide the design and structure of a benchmarking software tool. These items included the selection of appropriate representative data and reference contours obtained from established approaches and the description of available metrics. The benchmark was designed in a way that it could be extendable and open to the implementation of bespoke segmentation methods, while maintaining its main purpose of being a standard testing platform for newly developed PET-AS methods. An example of implementation of the proposed framework, named PETASset, was built. In this work, a selection of PET-AS methods representing common approaches to PET image segmentation were evaluated within PETASset for the purpose of testing and demonstrating the capabilities of the software as a benchmark platform. Results A selection of clinical, physical and simulated phantom data, including “best estimates” reference contours from macroscopic specimens, simulation template, and CT scans was built into the PETASset application database. Specific metrics such as Dice Similarity Coefficient (DSC), Positive Predictive Value (PPV), and Sensitivity (S), were included to allow the user to compare the results of any given PET-AS algorithm to the reference contours. In addition, a tool to generate structured reports on the evaluation of the performance of PET-AS algorithms against the reference contours was built. The variation of the metric agreement values with the reference contours across the PET-AS methods evaluated for demonstration were between 0.51 and 0.83, 0.44 and 0.86, and 0.61 and 1.00 for DSC, PPV, and the S metric, respectively. Examples of agreement limits were provided to show how the software could be used to evaluate a new algorithm against the existing state-of-the art. Conclusions PETASset provides a platform that allows standardizing the evaluation and comparison of different PET-AS methods on a wide range of PET datasets. The developed platform will be available to users willing to evaluate their PET-AS methods and contribute more evaluation datasets.

Published
2017

11. Systematic and random errors of PET‐based 90Y 3D dose quantification.

Author

Siman, W., Mawlawi, O. R., Mourtada, F., and Kappadath, S. C.

Subjects
*IMAGE reconstruction algorithms, *SPHERES
Abstract

Purpose: The objective was to characterize both systematic and random errors in Positron Emission Tomography (PET)‐based 90Y three‐dimensional (3D) dose quantification. Methods: A modified NEMA‐IEC phantom was used to emulate 90Y‐microsphere PET imaging conditions: sphere activity concentrations of 1.6 and 4.8 MBq/cc, sphere‐to‐background ratios of 4 and 13, and sphere diameters of 13, 17, and 37 mm. PET data were acquired using a GE D690 PET/CT scanner for 300 min on days 0–11. The data were downsampled to 60–5 min for multiple realizations to evaluate the count starvation effect. The image reconstruction algorithm was 3D‐OSEM with PSF + TOF modeling; the parameters were optimized for dose‐volume histogram (DVH), as a 90Y 3D dose quantification. 90Y‐PET images were converted to dose maps using the local deposition method, then the sphere DVHs were calculated. The ground truth for the DVH was calculated using convolution method. Dose linearity was evaluated in decaying 90Y activity (reduced count rate and total count) and decreasing acquisition durations (reduced total count only). Finally, the impacts of the low 32‐ppm positron yield on PET‐based 3D 90Y‐dose quantification were evaluated; the bias and variability of resulting DVHs were characterized. Results: We observed nonlinear errors that depended on the 90Y activity (count rate) and not on the total true prompt counts. These nonlinear errors in mean dose underestimated the measured mean dose by> 20% for a measured dose range of 40–230 Gy; although the shapes of the DVH were not altered. Compensation based on empirical models reduced the nonlinearity errors to be within 5% for measured dose range of 40–230 Gy. In contrast, the errors due to nonuniformity introduced by image noise dominated the systematic errors in the DVH and stretched the DVH on both tails. For the 37‐mm sphere, the magnitude of errors in D80 increased from −25% to −36% when acquisition duration was decreased from 300 to 10 min. The effect of image noise on DVH was more extensive in smaller spheres; for the 17‐mm sphere, the magnitude of errors in D80 increased from −29% to −45% acquisition duration was decreased from 300 to 10 min. For the 37‐mm sphere, the errors in D20 increased from +3.5% to only +10.5% when the acquisition duration was decreased from 300 to 10 min; in the 17‐mm sphere, the errors in D20 were 6.5% for both 300‐ and 10‐min sphere images. Conclusions: Count‐starved 90Y‐PET data introduce both systematic and random errors. The systematic error increases the apparent nonuniformity of the DVH, while the random error increases the uncertainty in the DVH. The systematic errors were larger than the random errors. Lower count rate of 90Y‐PET also introduces systematic bias, which is scanner specific. The errors of bias‐compensated mean tumor dose were <10% when 90Y‐PET scan time was >15 min/bed for tumors >37 mm. Dmedian and Dmean were the most stable dose metrics. An acquisition duration of 30 min is recommended to keep the random errors < 10% for a typical tumor with sphere equivalent diameter >17 mm and average tumor dose >40 Gy. [ABSTRACT FROM AUTHOR]

Published
2020
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13. Classification and evaluation strategies of auto-segmentation approaches for PET: Report of AAPM task group No. 211

Author

Hatt, M, Lee, J, Schmidtlein, C, El Naqa, I, Caldwell, C, De Bernardi, E, Lu, W, Das, S, Geets, X, Gregoire, V, Jeraj, R, Macmanus, M, Mawlawi, O, Nestle, U, Pugachev, A, Schöder, H, Shepherd, T, Spezi, E, Visvikis, D, Zaidi, H, Kirov, A, Hatt, M, Lee, J, Schmidtlein, C, El Naqa, I, Caldwell, C, De Bernardi, E, Lu, W, Das, S, Geets, X, Gregoire, V, Jeraj, R, Macmanus, M, Mawlawi, O, Nestle, U, Pugachev, A, Schöder, H, Shepherd, T, Spezi, E, Visvikis, D, Zaidi, H, and Kirov, A

Abstract

Purpose The purpose of this educational report is to provide an overview of the present state-of-the-art PET auto-segmentation (PET-AS) algorithms and their respective validation, with an emphasis on providing the user with help in understanding the challenges and pitfalls associated with selecting and implementing a PET-AS algorithm for a particular application. Approach A brief description of the different types of PET-AS algorithms is provided using a classification based on method complexity and type. The advantages and the limitations of the current PET-AS algorithms are highlighted based on current publications and existing comparison studies. A review of the available image datasets and contour evaluation metrics in terms of their applicability for establishing a standardized evaluation of PET-AS algorithms is provided. The performance requirements for the algorithms and their dependence on the application, the radiotracer used and the evaluation criteria are described and discussed. Finally, a procedure for algorithm acceptance and implementation, as well as the complementary role of manual and auto-segmentation are addressed. Findings A large number of PET-AS algorithms have been developed within the last 20 years. Many of the proposed algorithms are based on either fixed or adaptively selected thresholds. More recently, numerous papers have proposed the use of more advanced image analysis paradigms to perform semi-automated delineation of the PET images. However, the level of algorithm validation is variable and for most published algorithms is either insufficient or inconsistent which prevents recommending a single algorithm. This is compounded by the fact that realistic image configurations with low signal-to-noise ratios (SNR) and heterogeneous tracer distributions have rarely been used. Large variations in the evaluation methods used in the literature point to the need for a standardized evaluation protocol. Conclusions Available comparison studies sug

Published
2017

22. Repetitive noninvasive monitoring of hsvl-tk-expressing t cells intravenously infused into nonhuman primates using positron emission tomography and computed tomography with 18F-FEAU

Author

Savoldo, B., Dotti, G., Alauddin, M., Kornblau, S., Gelovani, J.G., Borne, A., Gonzalez, C., Paolillo, V., Jackson, J., Shpall, E.J., Decker, W.K., Najjar, A., Steiner, D., Tian, M., Smith, A., Mawlawi, O., Marini, F., Uthamanthil, R., Bollard, C.M., Brammer, D., and Cooper, L.J.N.

Abstract

Adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTLs) has been successfully used to treat patients with different types of cancer. However, the long-term spatial-temporal dynamics of the distribution of systemically infused CTLs rlargely unknown. Noninvasive imaging of adoptively transferred CTLs using molecular-genetic reporter imaging with positron emission tomography and computed tomography (PET-CT) represents an innovative approach to understanding the long-term migratory patterns and therapeutic potential of adoptively transferred T cells. Here we report the application of repetitive PET-CT imaging with [18F]fluoro-5-ethyl-1-beta-D- arabinofuranosyluracil (18F-FEAU) in two nonhuman primates demonstrating that autologous polyclonal macaque T lymphocytes activated and transduced with a retroviral vector encoding for the sr39 mutant herpes simplex virus 1 thymidine kinase (sr39HSV1-tk) reporter gene can be detected after intravenous infusion in discrete lymphoid organs and in sites of inflammation. This study represents a proof of principle and supports the application of 18F-FEAU PET-CT imaging for monitoring the distribution of intravenously administered sr39HSV1-tk gene-transduced CTLs in humans.

Published
2009
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