Muhammad Shumail

All Publications

• Shielding Analysis of a Preclinical Bremsstrahlung X-ray FLASH Radiotherapy System within a Clinical Radiation Therapy Vault. Health physics Rosenstrom, A., Santana-Leitner, M., Rokni, S., Shumail, M., Tantawi, S., Kwofie, J., Dewji, S., Loo, B. W. 2023

  Abstract

  A preclinical radiotherapy system producing FLASH dose rates with 12 MV bremsstrahlung x rays is being developed at Stanford University and SLAC National Accelerator Laboratory. Because of the high expected workload of 6,800 Gy w-1 at the isocenter, an efficient shielding methodology is needed to protect operators and the public while the preclinical system is operated in a radiation therapy vault designed for 6 MV x rays. In this study, an analysis is performed to assess the shielding of the local treatment head and radiation vault using the Monte Carlo code FLUKA and the empirical methodology given in the National Council on Radiation Protection and Measurements Report 151. Two different treatment head shielding designs were created to compare single-layer and multilayer shielding methodologies using high-Z and low-Z materials. The multilayered shielding methodology produced designs with a 17% reduction in neutron fluence leaking from the treatment head compared to the single layered design of the same size, resulting in a decreased effective dose to operators and the public. The conservative assumptions used in the empirical methods can lead to over-shielding when treatment heads use polyethylene or multilayered shielding. High-Z/Low-Z multilayered shielding optimized via Monte Carlo is shown to be effective in the case of treatment head shielding and provide more effective shielding design for external beam radiotherapy systems that use 12 MV bremsstrahlung photons. Modifications to empirical methods used in the assessment of MV radiotherapy systems may be warranted to capture the effects of polyethylene in treatment head shielding.

  View details for DOI 10.1097/HP.0000000000001718

  View details for PubMedID 37459481

• Frontiers in the Application of RF Vacuum Electronics. IEEE transactions on electron devices Armstrong, C. M., Snively, E. C., Shumail, M., Nantista, C., Li, Z., Tantawi, S., Loo, B. W., Temkin, R. J., Griffin, R. G., Feng, J., Dionisio, R., Mentgen, F., Ayllon, N., Henderson, M. A., Goodman, T. P. 2023; 70 (6): 2643-2655

  Abstract

  The application of radio frequency (RF) vacuum electronics for the betterment of the human condition began soon after the invention of the first vacuum tubes in the 1920s and has not stopped since. Today, microwave vacuum devices are powering important applications in health treatment, material and biological science, wireless communication-terrestrial and space, Earth environment remote sensing, and the promise of safe, reliable, and inexhaustible energy. This article highlights some of the exciting application frontiers of vacuum electronics.

  View details for DOI 10.1109/ted.2023.3239841

  View details for PubMedID 37250956

  View details for PubMedCentralID PMC10216895

• Frontiers in the Application of RF Vacuum Electronics IEEE TRANSACTIONS ON ELECTRON DEVICES Armstrong, C. M., Snively, E. C., Shumail, M., Nantista, C., Li, Z., Tantawi, S., Loo, B. W., Temkin, R. J., Griffin, R. G., Feng, J., Dionisio, R., Mentgen, F., Ayllon, N., Henderson, M. A., Goodman, T. P. 2023

  View details for DOI 10.1109/TED.2023.3239841

  View details for Web of Science ID 000947833100001

• Monte Carlo simulation of shielding designs for a cabinet form factor preclinical MV-energy photon FLASH radiotherapy system. Medical physics Rosenstrom, A., Leitner, M. S., Rokni, S. H., Shumail, M., Tantawi, S., Dewji, S., Jr, B. W. 2023

  Abstract

  A preclinical MV-energy photon FLASH radiotherapy system is being designed at Stanford and SLAC National Accelerator Laboratory. Because of the higher energy and dose rate compared to conventional kV-energy photon laboratory-scale irradiators, adequate shielding in a stand-alone cabinet form factor is more challenging to achieve. We present a Monte Carlo simulation of multilayered shielding for a compact self-shielding system without the need for a radiation therapy vault.A multilayered shielding approach using multiple alternating layers of high-Z and low-Z materials is applied to the self-shielded cabinet to effectively mitigate the secondary radiation produced and to allow the device to be housed in a Controlled Radiation Area outside of a radiation vault. The multilayered shielding approach takes advantage of the properties of high-Z and low-Z radiation shielding materials such as density, cross-section, atomic number of the shielding elements, and products of radiation interactions within each layer. The Monte Carlo radiation transport code, FLUKA, is used to simulate the total effective dose produced by the operation.The multilayered shielding designs proposed and simulated produced effective dose rates significantly lower than monolayer designs with the same total material thickness at the regulatory boundary; this is accomplished through the manipulation of the locations where secondary radiation is produced and reactions due to material properties such as neutron back reflection in hydrogen. Borated polyethylene at five weight percent significantly increased the shielding performance as compared to regular polyethylene, with the magnitude of the reduction depending upon the order of the shielding material.The multilayered shielding provides a path for shielding preclinical FLASH systems that deliver MV-energy bremsstrahlung photons. This approach promises to be more efficient with respect to the shielding material mass and space claim as compared to shielded vaults typically required for clinical radiation therapy with MV photons. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/mp.16290

  View details for PubMedID 36780153

• Bayesian optimisation to design a novel X-ray shaping device. Medical physics Whelan, B., Trovati, S., Wang, J., Fahrig, R., Maxim, P. G., Hanuka, A., Shumail, M., Tantawi, S., Merrick, J., Perl, J., Keall, P., Jr, B. W. 2022

  Abstract

  PURPOSE: In radiation therapy, X-ray dose must be precisely sculpted to the tumor, whilst simultaneously avoiding surrounding organs at risk. This requires modulation of X-ray intensity in space and/or time. Typically, this is achieved using a Multi Leaf Collimator (MLC) - a complex mechatronic device comprising over one hundred individually powered tungsten 'leaves' that move in or out of the radiation field as required. Here, an all-electronic X-ray collimation concept with no moving parts is presented, termed "SPHINX": Scanning Pencil-beam High-speed Intensity-modulated X-ray source. SPHINX utilizes a spatially distributed bremsstrahlung target and collimator array in conjunction with magnetic scanning of a high energy electron beam to generate a plurality of small X-ray "beamlets".METHODS: A simulation framework was developed in Topas Monte Carlo incorporating a phase space electron source, transport through user defined magnetic fields, bremsstrahlung X-ray production, transport through a SPHINX collimator, and dose in water. This framework was completely parametric, meaning a simulation could be built and run for any supplied geometric parameters. This functionality was coupled with Bayesian optimization to find the best parameter set based on an objective function which included terms to maximize dose rate for a user defined beamlet width while constraining inter-channel cross talk and electron contamination. Designs for beamlet widths of 5, 7, and 10 mm2 were generated. Each optimization was run for 300 iterations and took approximately 40 hours on a 24 core computer. For the optimized seven-mm model, a simulation of all beamlets in water was carried out including a linear scanning magnet calibration simulation. Finally, a back-of-envelope dose rate formalism was developed and used to estimate dose rate under various conditions.RESULTS: The optimized five-mm, seven-mm, and ten-mm models had beamlet widths of 5.1 mm, 7.2 mm, and 10.1 mm2 and dose rates of 3574 Gy/C, 6351 Gy/C and 10015 Gy/C respectively. The reduction in dose rate for smaller beamlet widths is a result of both increased collimation and source occlusion. For the simulation of all beamlets in water, the scanning magnet calibration reduced the offset between the collimator channels and beam centroids from 2.9+-1.9 mm to 0.01 +- 0.03mm. A slight reduction in dose rate of approximately 2% per degree of scanning angle was observed. Based on a back-of-envelope dose rate formalism, SPHINX in conjunction with next-generation linear accelerators has the potential to achieve substantially higher dose rates than conventional MLC based delivery, with delivery of an intensity modulated 100*100 mm2 field achievable in 0.9 to 10.6 s depending on the beamlet widths used.CONCLUSIONS: Bayesian optimization was coupled with Monte Carlo modelling to generate SPHINX geometries for various beamlet widths. A complete Monte Carlo simulation for one of these designs was developed, including electron beam transport of all beamlets through scanning magnets, X-ray production and collimation, and dose in water. These results demonstrate that SPHINX is a promising candidate for sculpting radiation dose with no moving parts, and has the potential to vastly improve both the speed and robustness of radiotherapy delivery. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/mp.15887

  View details for PubMedID 35904020

• Initial Steps Towards a Clinical FLASH Radiotherapy System: Pediatric Whole Brain Irradiation with 40 MeV Electrons at FLASH Dose Rates. Radiation research Breitkreutz, D. Y., Shumail, M. n., Bush, K. K., Tantawi, S. G., Maxim, P. G., Loo, B. W. 2020

  Abstract

  In this work, we investigated the delivery of a clinically acceptable pediatric whole brain radiotherapy plan at FLASH dose rates using two lateral opposing 40-MeV electron beams produced by a practically realizable linear accelerator system. The EGSnrc Monte Carlo software modules, BEAMnrc and DOSXYZnrc, were used to generate whole brain radiotherapy plans for a pediatric patient using two lateral opposing 40-MeV electron beams. Electron beam phase space files were simulated using a model of a diverging beam with a diameter of 10 cm at 50 cm SAD (defined at brain midline). The electron beams were collimated using a 10-cm-thick block composed of 5 cm of aluminum oxide and 5 cm of tungsten. For comparison, a 6-MV photon plan was calculated with the Varian AAA algorithm. Electron beam parameters were based on a novel linear accelerator designed for the PHASER system and powered by a commercial 6-MW klystron. Calculations of the linear accelerator's performance indicated an average beam current of at least 6.25 μA, providing a dose rate of 115 Gy/s at isocenter, high enough for cognition-sparing FLASH effects. The electron plan was less homogenous with a homogeneity index of 0.133 compared to the photon plan's index of 0.087. Overall, the dosimetric characteristics of the 40-MeV electron plan were suitable for treatment. In conclusion, Monte Carlo simulations performed in this work indicate that two lateral opposing 40-MeV electron beams can be used for pediatric whole brain irradiation at FLASH dose rates of 115 Gy/s and serve as motivation for a practical clinical FLASH radiotherapy system, which can be implemented in the near future.

  View details for DOI 10.1667/RADE-20-00069.1

  View details for PubMedID 32991725

• Theory of electromagnetic insertion devices and the corresponding synchrotron radiation PHYSICAL REVIEW ACCELERATORS AND BEAMS Shumail, M., Tantawi, S. G. 2016; 19 (7)

  View details for DOI 10.1103/PhysRevAccelBeams.19.074001

  View details for Web of Science ID 000381500600001

• Experimental Demonstration of a Tunable Microwave Undulator PHYSICAL REVIEW LETTERS Tantawi, S., Shumail, M., Neilson, J., Bowden, G., Chang, C., Hemsing, E., Dunning, M. 2014; 112 (16)

  Abstract

  Static magnetic undulators used by x-ray light sources are fundamentally too limited to achieve shorter undulator periods and dynamic control. To overcome these limitations, we report experimental demonstration of a novel short-period microwave undulator, essentially a Thomson scattering device, that has yielded tunable spontaneous emission and seeded coherent radiation. Its equivalent undulator period (λu) is 13.9 mm while it has achieved an equivalent magnetic field of 0.65 T. For future-generation light sources, this device promises a shorter undulator period, a large aperture, and fast dynamic control.

  View details for DOI 10.1103/PhysRevLett.112.164802

  View details for Web of Science ID 000335325900006

  View details for PubMedID 24815654

• Electron dynamics and transverse-kick elimination in a high-field short-period helical microwave undulator APPLIED PHYSICS LETTERS Chang, C., Shumail, M., Tantawi, S., Neilson, J., Pellegrini, C. 2012; 101 (16)

  View details for DOI 10.1063/1.4759002

  View details for Web of Science ID 000310669300002