476
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Jin L, Eldib A, Li J, Fan J, Wang L, Ma C. MO-G-213AB-05: Beam Simulation and Measurement for Energy-Intensity Modulated Electron Radiotherapy (MERT) with a Computer-Controlled Electron Multileaf Collimator Device. Med Phys 2012. [DOI: 10.1118/1.4735842] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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477
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Ma C, Yin Y. SU-E-J-188: Lung CT Density Changes during the Conformal Radiotherapy: A Prediction for Lung Radiation Pneumonitis. Med Phys 2012; 39:3696. [PMID: 28519051 DOI: 10.1118/1.4735029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Radiologic lung density changes are observed durng radiotherapy for lung cancer. We studied the relationship between dose and computed tomography (CT) density changes during the treatment, a prediction for lung radiation pneumonitis. METHODS 30 Stage â…¢ lung cancer patients with CRT were thirty fractions of 2.0 Gy, prescribed at the 90% isodose. Follow-up CT scans performed at less than 3 weeks (n=15) and between 3 and 6 weeks (n=15) after CRT radiotherapy were reviewed. New CT scans were coregistered with baseline scans using CT-CT normalized mutual information registration algorithm. Voxel-Hounsfield unit histograms were created for doses between 0.5 and 50 Gy. Linear mixed effects models were used to assess the effects of CRT dose on CT density, and the influence of possible confounders was tested. RESULTS Increased mean CT density was associated with higher dose, increasing planning target volume size, and increasing time after CRT (all p <0.05). Density increases were apparent in areas receiving 20 Gy, but seemed to plateau above 40 Gy. In regions receiving >30 Gy, the reduction in air-filled fraction of lung during treatment was up to 20%. No increase in CT density was observed in the contralateral lung receiving less than 5 Gy. CONCLUSIONS A dose-response relationship seems to exist for quantitative CT density changes during CRT radiotherapy. The density between old and new CT during the treatment could be a prediction for lung injury.
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478
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Lin M, Li J, Koren S, Fan J, Wang L, Yin G, Ma C. TU-E-BRB-06: Best in Physics (Therapy) - Development and Experimental Validation of EPID-Based 4D Dose Reconstruction. Med Phys 2012; 39:3909. [PMID: 28518692 DOI: 10.1118/1.4735955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To develop and validate an EPID-based 4D patient dose reconstruction framework accounting for linac delivery uncertainties, interfractional and intrafractional motions, and interplay effect. METHODS Patients with fiducial markers were scanned with 4D-CT for SBRT planning. Before treatment, in-room 4D-CT was performed. Both the MLC and the tumor movements were tracked by continuously acquiring EPID images during treatment. Instead of directly using the heterogeneous transit photon fluence measured by the EPID, this method reconstructed the incident beam fluence based on the MLC apertures measured by the EPID and the delivered MU recorded by the linac. To account for the time-dependent-geometry, the incident fluence distributions were sorted into their corresponding phases based on the tumor motion pattern detected by the EPID and accumulated as the incident fluence map for each phase. Together with 4D-CT, it was then used for Monte Carlo dose calculation. Deformable registration was performed to sum up the phase doses for treatment assessment. The feasibility of using the transit EPID images for incident fluence reconstruction was evaluated against EPID in-air measurements. The accuracy of 3D- and 4D-dose reconstruction was validated by a motordriven cylindrical diode array for six clinical SBRT plans. RESULTS The average difference between the measured and reconstructed fluence maps is within 0.16%. The reconstructed 3D-dose shows 1.4% agreement in the CAX-dose and >98.5% gamma-passing-rate (2%/2mm) in the peripheral-dose. A distorted dose distribution is observed in the measurement for the moving ArcCheck-phantom. The comparison between the measured and the reconstructed 4D-dose without considering interplay fails the gammaevaluation (59%-88.9% gamma-passing-rate). In contrast, when the interplay is considered, the dose distortion phenomena is successfully represented in the reconstructed dose (>97.6% gamma-passing-rate). CONCLUSIONS The experimental validation demonstrates that the proposed method provides a practical way to reconstruct the fractional 4D-doses received by the patient and enables adaptive SBRT strategy.
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479
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Faddegon B, Ma C, Chetty I. WE-B-213AB-03: AAPM TG-1S7: Commercial Implementation of Source Modeling and Beam Commissioning for Clinical Monte Carlo Dose Calculation. Med Phys 2012. [DOI: 10.1118/1.4736083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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480
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Jin L, Eldib A, Fan J, Li J, Wang L, Ma C. MO-G-213AB-04: Investigation of Photon MLC to Deliver Energy and Intensity Modulated Electron Beams for Advanced Radiotherapy. Med Phys 2012. [DOI: 10.1118/1.4735841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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481
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Ma C, Shan G, Hu W, Xu Q, Mohamed I, Fan J, Chen L. SU-E-J-07: Image Guided Radiotherapy for Prostate Cancer: To Shift Or to Re-Plan? Med Phys 2012; 39:3653. [DOI: 10.1118/1.4734839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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482
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Chetty IJ, Faddegon B, Ma C. WE-B-213AB-02: AAPM TG-157 Recommendations on Beam Commissioning for Clinical Monte Carlo Dose Calculation. Med Phys 2012. [DOI: 10.1118/1.4736082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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483
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Fan J, Chen X, Koren S, Jin L, Chen L, Price R, Wang L, Hayes S, Tam T, Ma C. SU-E-T-638: Treatment Margins Expansion for CyberKnife Treatment Plans. Med Phys 2012; 39:3852-3853. [DOI: 10.1118/1.4735727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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484
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Fourkal E, Veltchev I, Koren S, Lin M, Ma C, Meyer J, Doss M, Yu M. WE-A-BRB-06: 3D In-Patient Dose Reconstruction from the PET-CT Imaging of Y-90 Microspheres for Metastatic Cancer to the Liver. Med Phys 2012. [DOI: 10.1118/1.4736047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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485
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Hossain M, Richardson T, Buyyounouski MK, Schirmer T, Noeske R, Chen L, Ma C. SU-E-I-65: Magnetic Resonance Spectroscopy of the Prostate: A Phantom Study of Metabolite Concentrations. Med Phys 2012; 39:3639-3640. [DOI: 10.1118/1.4734781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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486
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Tong X, Chen X, Li J, Lin M, Chen L, Xu Q, Ma C. SU-D-BRA-06: Investigation of Prostate Intrafractional Motion during External Beam Radiotherapy for a Large Patient Population. Med Phys 2012; 39:3617. [DOI: 10.1118/1.4734684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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487
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Wang L, Turaka A, Meyer J, Spoka D, Jin L, Fan J, Ma C. SU-E-J-24: Image-Guidance Using Cone-Beam CT for Stereotactic Body Radiotherapy (SBRT) of Lung Cancer Patients: Bony Alignment or Soft Tissue Alignment? Med Phys 2012; 39:3657. [DOI: 10.1118/1.4734857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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488
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Xu Q, Lin M, Chen X, Tong X, Fan J, Dong Z, Chen L, Ma C. SU-E-J-139: Feasibility of Using EPID for Real-Time Target Localization during Treatment. Med Phys 2012; 39:3684. [PMID: 28518940 DOI: 10.1118/1.4734975] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This study aims to investigate the feasibility of using the images of the treatment fields acquired by an electronic portal imaging device (EPID) for real-time target localization. METHODS Forty one patients treated with IMRT and RapidArc were recruited in this study including 37 prostate patients and 4 lung patients. These patients were grouped as: prostate IMRT with lymph node (n=14), prostate IMRT without lymph node (n=17), prostate RapidArc (n=6), and lung IMRT (n=4). For each patient, two to four fiducial markers were implanted inside the tumor. The DRR, which projects the patient anatomy and the fiducial marker at the EPID location, was reconstructed for each field. The MLC aperture of each control point was overlay on its corresponding DRR to evaluate the fractional time when the fiducial marker was seen on the EPID image. The probability of seeing at least one, two, three, and four fiducial markers during the treatment was recorded. RESULTS For the prostate IMRT patients without lymph nodes included in the target volume, the average probability of seeing at least one, two, three, and four fiducial markers during the treatment was 50% (35%-59%), 39% (23%-51%), 24% (7%-38%), and 12% (4%-29%), respectively. For the prostate IMRT patients with lymph nodes, the probability was 41% (24%-51%), 29% (12%-42%), 15% (3%-24%), and 7% (4%-15%), respectively. For prostate RapidArc treatments using two arcs, the average probability of seeing at least one fiducial marker was 81% (58%-90%) for the full arc and 74% (53%-94%) for the partial arc. For the lung IMRT treatment, the average probability of seeing at least one fiducial marker was 34% (20%-52%). CONCLUSIONS The continuous image acquisition from the EPID during the treatment provides sufficient target movement information for real-time target localization and intrafractional target motion correction for advanced radiotherapy treatments.
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489
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Koren S, Price R, Veltchev I, Lin M, Fan J, Ma C. SU-E-T-53: 3D Dose Measurements Using the Planned Dose Perturbation Technique (PDP) for the Evaluation of Head and Neck VMAT Treatment. Med Phys 2012. [DOI: 10.1118/1.4735109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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490
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Veltchev I, Price R, Ma C. WE-G-BRB-01: Per-Frame Analysis of MatriXX Data. Med Phys 2012; 39:3966-3967. [PMID: 28519601 DOI: 10.1118/1.4736187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE One of the most widely used IMRT QA devices (MatriXX) is an array of ionization chambers which are periodically read during plan delivery. Although the ionization chambers are not expected to exhibit strong angular dependence, the measured dose distribution is often found to significantly differ from the planned dose distribution. We identify the origin of all factors that affect the measurement accuracy of the MatriXX and develop a per-frame post-processing strategy that reduces their impact on the passing rate of IMRT and VMAT plans. METHODS We developed software that reads the dose frame sequence recorded by the MatriXX and applies a number of correction factors to each frame. Angular correction factors are computed as ratios of measured dose at the isocenter of the phantom and planned dose at the same location for all clinically used photon energies. For every clinical case, the recorded movie file is read and the dose for every frame is corrected according to the angle of the beam. In addition, the background evolution is tracked in the 'beam-off' frames which are subsequently subtracted from the 'beam-on' frames according to a predictive model. Machine output correction is also implemented, which significantly improves the absolute dose measurements. The IMRT effective plane of measurement of the MatriXX was identified and found not to coincide with the isocentric plane. RESULTS The clinical passing rates are significantly improved when the per-frame analysis software was introduced in our IMRT QA procedure. For a group of 800 patients with no corrections the average passing rate was 93.6%, while for the first 300 cases with per frame corrections the average passing rate was 97.3%. CONCLUSIONS We identify all factors that impact the measurement accuracy of the MatriXX (angular effects, background evolution, machine output, plane of measurement) and propose a strategy for their elimination.
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491
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Veltchev I, Fourkal E, Price R, Ma C. SU-E-T-590: Procedure for Verification and Inter-Comparison of IMRT Beam Models. Med Phys 2012; 39:3841. [DOI: 10.1118/1.4735679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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492
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Yin G, Koren S, Lin M, Chen L, Ma C. SU-E-T-594: Dosimetric Evaluation of Different Treatment Techniques for Prostate Cancer. Med Phys 2012; 39:3842. [DOI: 10.1118/1.4735683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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493
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Eldib A, Li J, Jin L, Ma C. SU-E-T-441: A Feasibility Study to Replace Electron Cutouts with a Motorized Electron Multileaf Collimator. Med Phys 2012; 39:3806. [PMID: 28517433 DOI: 10.1118/1.4735530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Fabrication of electron beam cutouts not only is a time consuming process but also involves the handling of cerrobend which is a toxic material. Hospital workers involved in cutout construction can actually be exposed to toxic fumes that are usually generated during the process. The aim of this work is to study the feasibility of replacing electron cutouts with our prototype motorized electron multileaf collimator (eMLC). METHODS Electron beams collimated by an eMLC have very similar penumbra to those collimated by applicators and cutouts as we already demonstrated in a previous study. However undulation of the isodose curves is expected due to the finite size of the eMLC. This may be a problem when the field edge is close to critical structure. Thus ten different breast cases that were previously treated with an electron boost were selected from our database. An inhouse Monte Carlo based treatment planning system were used for dose calculation using the patients CTs. For each patient two plans were generated one with electron beams collimated using the applicator/cutout combination and the other plan with beams collimated only by the eMLC. Treatment plan quality was compared for each patient based on dose distribution and dose volume histogram. In order to determine the optimal position of the leaves, the impact of the different leaf positioning strategies were investigated. RESULTS Results have shown that target coverage and critical structure sparing can be effectively achieved by electron beams collimated by eMLC. Preliminary results have shown that the out-of-field strategy is most conservative and would be the recommended method to define the actual leaf position for the eMLC defined field. CONCLUSION The eMLC represents an effective time saving and pollution free device that can completely eliminate the need for patient specific cutouts. This work has been supported by a UICC American Cancer Society Beginning Investigators Fellowship funded by the American Cancer Society.
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494
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Koren S, Veltchev I, Fan J, Lin M, Tafo AG, Ma C. WE-G-BRB-09: CyberKnife Patient Specific QA Using a 4D Cylindrical Diode Array System. Med Phys 2012; 39:3968. [DOI: 10.1118/1.4736195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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495
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Ma C. WE-B-213AB-01: AAPM TG1S7: An Overview of Source Modeling and Beam Commissioning for Clinical Monte Carlo. Med Phys 2012. [DOI: 10.1118/1.4736081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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496
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Chen L, Rapoport N, Chen X, Cvetkovic D, Xue J, Xu Q, Tong X, Liu H, Gupta R, Ma C. TU-A-BRA-11: Targeted Drug Delivery Technique Employing Pulsed Focused Ultrasound for Treatment of Prostate. Med Phys 2012. [DOI: 10.1118/1.4735879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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497
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Lin T, Fan J, Hossain M, Ma C. SU-E-T-483: Delay Treatment or Switch to Different Machines? Dosimetric Effect and Tumor Control Probability. Med Phys 2012; 39:3816. [DOI: 10.1118/1.4735572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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498
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Fan J, Xu Q, Wang L, Jin L, Li J, Lin T, Hayes S, Tam T, Ma C. SU-E-T-448: Switch Patients between Collimation Systems for CyberKnife Treatment Feasibility Study. Med Phys 2012; 39:3808. [DOI: 10.1118/1.4735537] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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499
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Ma C. SU-E-T-457: Multi-Mode Model - A Consistent Approach for Conventionally Fractionated Radiotherapy and Stereotactic Body Radiotherapy. Med Phys 2012; 39:3810. [PMID: 28517486 DOI: 10.1118/1.4735546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The accuracy of dosimetric analysis and outcome comparison between conventionally fractionated radiation therapy(CFRT) and stereotactic body radiotherapy(SBRT) requires reliable radiobiological modeling. The aim of this work was to further improve the multi-mode model(MMM) for both CFRT and SBRT. METHODS MMM assumes the existence of different modes of cell killing as a Result of radiation damage to different parts of a cell, e.g., a single severe damage to the DNA or two or more small damages to the membrane or DNA. The cell survival probability can then be calculated by s=Product_(i=1,n){1-(1-ê(-d/Di))̂(i)}, where i represents the i-th mode of cell killing that requires i potentially unrepairable damages to the cell as a result of radiation dose d and Di is the dose that gives 63% probability to cause an unrepairable damage for the i-th mode. The dose rate effect is included in MMM assuming 1/D_i=(k_i- r_i/U), where k_i is the radiation damage rate, r_i the repair rate and U the dose rate. The low-dose hypersensitivity is also included in the new model. RESULTS A comparison of the goodness-of-fit of the LQ, multitarget, USC and MMM to the survival curve of the H460 non-small-cell lung cancer cell line showed the same agreement between USC and MMM with the survival data, which was significantly better than the fits to the LQ and multitarget models. The parameters used for the LQ, multitarget and USC models were alpha=0.33Gy, alpha/beta=10Gy, D_T =6.2Gy, D_0 =1.25Gy and D_q =1.8Gy. The parameters for MMM(n=4) were D_1=4.0Gy, D_2=4.01Gy, D_3=3.08Gy and D_4=41Gy. CONCLUSIONS MMM offers a superior description of the mammalian cell survival curve in both conventional and ablative dose ranges, which can be used for designing new fractionation schemes and predicting and understanding treatment outcomes for both CFRT and SBRT.
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500
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Price R, Koren S, Hossain M, Veltchev I, Galloway T, Flanagan P, Ma C. SU-E-T-554: PTV to Skin Proximity for Head and Neck IMRT Treatment Planning. Med Phys 2012; 39:3833. [DOI: 10.1118/1.4735643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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