Papers by Cassandra Stambaugh
Journal of Applied Clinical Medical Physics, 2021
Abstract This work of fiction re‐enacts a scenario in which a medical physics resident was not ab... more Abstract This work of fiction re‐enacts a scenario in which a medical physics resident was not able to address a physics call during patient simulation and was criticized by the supervising faculty physicist in front of the team and the patient. The resident and the faculty agreed to meet afterwards to debrief the situation, in the hope of establishing a better working relationship. The intended use of this case, through group discussion, self‐study, or role‐play, is to encourage readers to discuss the situation at hand, inspire professionalism and leadership thinking, and allow the practice of conflict management. Facilitator's notes are available upon request to the MPLA Cases Subcommittee. This case study falls under the scope of and is supported by the Medical Physics Leadership Academy (MPLA), a committee in the American Association of Physicists in Medicine (AAPM).
Journal of Applied Clinical Medical Physics, 2021
This fictional case describes a managerial situation of implementing cone‐beam computed tomograph... more This fictional case describes a managerial situation of implementing cone‐beam computed tomography faced by a solo medical physicist in a rural community hospital. The intended use of the case study, in either a facilitated learning session or self‐study, is to inspire the readers to discuss the situation, analyze the institutional and personal factors, apply relevant leadership skills, and propose action plans. This case study falls under the scope of, and is supported by, the Medical Physics Leadership Academy (MPLA). A sample facilitator’s guide or self‐study guide is included in the manuscript for reference by users of this case study.
Journal of Applied Clinical Medical Physics, 2021
This guide provides a framework and general steps for writing a case study for the Medical Physic... more This guide provides a framework and general steps for writing a case study for the Medical Physics Leadership Academy (MPLA). 1,2 This guide may be used as part of the Request for Proposal (RFP) for case studies in AAPM leadership-themed sessions. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
International Journal of Radiation Oncology*Biology*Physics, 2021
PURPOSE/OBJECTIVE(S) To examine current practice patterns in non-English speaking breast cancer p... more PURPOSE/OBJECTIVE(S) To examine current practice patterns in non-English speaking breast cancer patients undergoing Deep Inspiratory Breath Hold (DIBH). We hypothesize that disparities in DIBH utilization exist between English and non-English speaking patients. MATERIALS/METHODS An anonymous, voluntary online survey was distributed to residency program coordinators of U.S. radiation oncology departments to survey their faculty and recent graduates. Eligibility was limited to board-certified radiation oncologists who have treated breast cancer within the prior 6 months. RESULTS There were 66 respondents, 50 of whom were eligible. 70% (n = 35) of eligible respondents were from academic sites. Slightly over half (52%) of respondents reported that at least 10% of their patients were non-English speaking. Most offered DIBH at their institution (92%) and of those, 82% of responding radiation oncologists used DIBH for at least a quarter or more of their breast cancer patients. Nearly all of those who use DIBH (98%) used coaching at the time of simulation, with about a third (37%) answering they would be "less likely" to utilize DIBH for non-English speaking patients. If DIBH is used for non-English speaking patients, 86% would take into consideration potential language barriers for proper execution of DIBH. However, slightly over one-half of respondents had an interpreter present 76-100% of the time at CT simulation. At the first DIBH treatment, 31% used an interpreter 76-100% of the time. And at each subsequent treatment, 11% used an interpreter 76-100% of the time. CONCLUSION Disparities in the application of DIBH exist despite its established utility in reducing cardiac dose. This study provides evidence that language barriers may impact physician treatment practices from initial consideration of DIBH to subsequent delivery. Even within a limited sampling of self-reported responses, this data suggests that breast cancer treatment considerations and subsequent execution are negatively affected in non-English speaking patients.
Journal of Applied Clinical Medical Physics, 2018
Implementing tighter intensity modulated radiation therapy (IMRT) quality assurance (QA) toleranc... more Implementing tighter intensity modulated radiation therapy (IMRT) quality assurance (QA) tolerances initially resulted in high numbers of marginal or failing QA results and motivated a number of improvements to our calculational processes. This work details those improvements and their effect on results. One hundred eighty IMRT plans analyzed previously were collected and new gamma criteria were applied and compared to the original results. The results were used to obtain an estimate for the number of plans that would require additional dose volume histogram (DVH)-based analysis and therefore predicted workload increase. For 2 months and 133 plans, the established criteria were continued while the new criteria were applied and tracked in parallel. Because the number of marginal or failing plans far exceeded the predicted levels, a number of calculational elements were investigated: IMRT modeling parameters, calculation grid size, and couch top modeling. After improvements to these elements, the new criteria were clinically implemented and the frequency of passing, questionable, and failing plans measured for the subsequent 15 months and 674 plans. The retrospective analysis of selected IMRT QA results demonstrated that 75% of plans should pass, while 19% of IMRT QA plans would need DVH-based analysis and an additional 6% would fail. However, after applying the tighter criteria for 2 months, the distribution of plans was significantly different from prediction with questionable or failing plans reaching 47%. After investigating and improving several elements of the IMRT calculation processes, the frequency of questionable plans was reduced to 11% and that of failing plans to less than 1%. Tighter IMRT QA tolerances revealed the need to improve several elements of our plan calculations. As a consequence, the accuracy of our plans have improved, and the frequency of finding marginal or failing IMRT QA results, remains within our practical ability to respond.
Medical Physics, 2018
Purpose: To determine clinically relevant pass/question/fail criteria for gamma analysis of inten... more Purpose: To determine clinically relevant pass/question/fail criteria for gamma analysis of intensity modulated radiation therapy quality assurance (IMRT QA) plans, identify which plans should be further analyzed with dose-volume histogram (DVH) metrics, and create a workflow for performing that DVH-based analysis. Methods: Eleven plans, five prostate and six head/neck, were selected to represent known good plans based on their high passing rate using conventional IMRT QA criteria. These were modified by moving the programmed MLC positions to underdose the target or overdose important structures by varying amounts. Commercially available hardware/software was used to measure and analyze all plans (76 total) using 4%/3mm, 3%/3mm, 3%/2mm and 2%/2mm gamma criteria. Two receiver operator characteristic (ROC) curves per criterion were created to assess effective passing rates. One ROC curve was to find a higher threshold that determined a clear pass and the second to find a lower threshold to determine a clear failure. Plans between these two thresholds need DVH-based analysis to assess the clinical consequence of the dose difference. The modified plans were analyzed in the planning system and reconstructed in commercially available DVH-based analysis software to access the accuracy and usefulness of the software. Results: Analysis of the ROC curves showed optimal pass and fail thresholds for plan error detection per criterion to achieve clinically relevant sensitivity and specificity. Based on measurement Accepted Article This article is protected by copyright. All rights reserved. uncertainty and pass/fail ranges, 3%/2mm gamma criteria with a pass threshold of 95% and a fail threshold of 90% were most optimal. DVH analysis showed good agreement with all reconstructed plans except where the changes to the MLC patterns caused the periphery of the target to be underdosed. For questionable plans, comparing the organ-specific DVHs to the physician-provided planning constraints proved to be an efficient and effective workflow since plans for which the target dose was slightly high or where organs at risk was underdosed could be released for treatment without consulting the physician for a clinical decision. Conclusion: This work indicates the potential for appreciable improvement in error detection for IMRT QA. Using effective pass/fail thresholds to determine plans that need DVH-based analysis minimizes the need for excessive, time-consuming, analysis, and making use of the dosimetric constraints of the plan minimizes the burden on physicians. Overall, DVH-based analysis is a powerful tool that can provide substantial insight over the traditional approach that does not provide structure-specific data.
Medical Physics, 2015
Previous studies show that dose to a moving target can be estimated using 4D measurementguided do... more Previous studies show that dose to a moving target can be estimated using 4D measurementguided dose reconstruction based on a process called virtual motion simulation, or VMS. A potential extension of VMS is to estimate dose during dynamic multileaf collimator (MLC)-tracking treatments. The authors introduce a modified VMS method and quantify its performance as proof-ofconcept for tracking applications. Methods: Direct measurements with a moving biplanar diode array were used to verify accuracy of the VMS dose estimates. A tracking environment for variably sized circular MLC apertures was simulated by sending preprogrammed control points to the MLC while simultaneously moving the accelerator treatment table. Sensitivity of the method to simulated tracking latency (0-700 ms) was also studied. Potential applicability of VMS to fast changing beam apertures was evaluated by modeling, based on the demonstrated dependence of the cumulative dose on the temporal dose gradient. Results: When physical and virtual latencies were matched, the agreement rates (2% global/2 mm gamma) between the VMS and the biplanar dosimeter were above 96%. When compared to their own reference dose (0 induced latency), the agreement rates for VMS and biplanar array track closely up to 200 ms of induced latency with 10% low-dose cutoff threshold and 300 ms with 50% cutoff. Time-resolved measurements suggest that even in the modulated beams, the error in the cumulative dose introduced by the 200 ms VMS time resolution is not likely to exceed 0.5%. Conclusions: Based on current results and prior benchmarks of VMS accuracy, the authors postulate that this approach should be applicable to any MLC-tracking treatments where leaf speeds do not exceed those of the current Varian accelerators.
Medical Physics, 2015
The authors designed data, methods, and metrics that can serve as a standard, independent of any ... more The authors designed data, methods, and metrics that can serve as a standard, independent of any software package, to evaluate dose-volume histogram (DVH) calculation accuracy and detect limitations. The authors use simple geometrical objects at different orientations combined with dose grids of varying spatial resolution with linear 1D dose gradients; when combined, ground truth DVH curves can be calculated analytically in closed form to serve as the absolute standards. Methods: RT structure sets containing a small sphere, cylinder, and cone were created programmatically with axial plane spacing varying from 0.2 to 3 mm. Cylinders and cones were modeled in two different orientations with respect to the IEC 1217 Y axis. The contours were designed to stringently but methodically test voxelation methods required for DVH. Synthetic RT dose files were generated with 1D linear dose gradient and with grid resolution varying from 0.4 to 3 mm. Two commercial DVH algorithms- (Philips Radiation Oncology Systems) and PlanIQ (Sun Nuclear Corp.)-were tested against analytical values using custom, noncommercial analysis software. In Test 1, axial contour spacing was constant at 0.2 mm while dose grid resolution varied. In Tests 2 and 3, the dose grid resolution was matched to varying subsampled axial contours with spacing of 1, 2, and 3 mm, and difference analysis and metrics were employed: (1) histograms of the accuracy of various DVH parameters (total volume, D max , D min , and doses to % volume: D99, D95, D5, D1, D0.03 cm 3) and (2) volume errors extracted along the DVH curves were generated and summarized in tabular and graphical forms. Results: In Test 1, produced 52 deviations (15%) while PlanIQ produced 5 (1.5%). In Test 2, and PlanIQ differed from analytical by >3% in 93 (36%) and 18 (7%) times, respectively. Excluding D min and D max as least clinically relevant would result in 32 (15%) vs 5 (2%) scored deviations for vs PlanIQ in Test 1, while Test 2 would yield 53 (25%) vs 17 (8%). In Test 3, statistical analyses of volume errors extracted continuously along the curves show to have more errors and higher variability (relative to PlanIQ), primarily due to 's lack of sufficient 3D grid supersampling. Another major driver for errors is an inconsistency in implementation of the "end-capping"; the additional volume resulting from expanding superior and inferior contours halfway to the next slice is included in the total volume calculation, but dose voxels in this expanded volume are excluded from the DVH. PlanIQ had fewer deviations, and most were associated with a rotated cylinder modeled by rectangular axial contours; for coarser axial spacing, the limited number of cross-sectional rectangles hinders the ability to render the true structure volume. Conclusions: The method is applicable to any DVH-calculating software capable of importing RT structure set and dose objects (the authors' examples are available for download). It includes a collection of tests that probe the design of the DVH algorithm, measure its accuracy, and identify failure modes. Merits and applicability of each test are discussed.
Journal of applied clinical medical physics / American College of Medical Physics, Jan 8, 2015
It was previously demonstrated that dose delivered by a conventional linear accelerator using IMR... more It was previously demonstrated that dose delivered by a conventional linear accelerator using IMRT or VMAT can be reconstructed - on patient or phantom datasets - using helical diode array measurements and a technique called planned dose perturbation (PDP). This allows meaningful and intuitive analysis of the agreement between the planned and delivered dose, including direct comparison of the dose-volume histograms. While conceptually similar to modulated arc techniques, helical tomotherapy introduces significant challenges to the PDP formalism, arising primarily from TomoTherapy delivery dynamics. The temporal characteristics of the delivery are of the same order or shorter than the dosimeter's update interval (50 ms). Additionally, the prevalence of often small and complex segments, particularly with the 1 cm Y jaw setting, lead to challenges related to detector spacing. Here, we present and test a novel method of tomotherapy-PDP (TPDP) designed to meet these challenges. One o...
Journal of applied clinical medical physics / American College of Medical Physics, Jan 6, 2014
We report the results of a preclinical evaluation of recently introduced commercial tools for 3D ... more We report the results of a preclinical evaluation of recently introduced commercial tools for 3D patient IMRT/VMAT dose reconstruction, the Delta4 Anatomy calculation algorithm. Based on the same initial measurement, volumetric dose can be reconstructed in two ways. Three-dimensional dose on the Delta4 phantom can be obtained by renormalizing the planned dose distribution by the measurement values (D4 Interpolation). Alternatively, incident fluence can be approximated from the phantom measurement and used for volumetric dose calculation on an arbitrary (patient) dataset with a pencil beam algorithm (Delta4 PB). The primary basis for comparison was 3D dose obtained by previously validated measurement-guided planned dose perturbation method (ACPDP), based on the ArcCHECK dosimeter with 3DVH software. For five clinical VMAT plans, D4 Interpolation agreed well with ACPDP on a homogeneous cylindrical phantom according to gamma analysis with local dose-error normalization. The average agr...
Radiotherapy and Oncology, 2014
Delta(4) (ScandiDos AB, Uppsala, Sweden) and ArcCHECK with 3DVH software (Sun Nuclear Corp., Melb... more Delta(4) (ScandiDos AB, Uppsala, Sweden) and ArcCHECK with 3DVH software (Sun Nuclear Corp., Melbourne, FL, USA) are commercial quasi-three-dimensional diode dosimetry arrays capable of volumetric measurement-guided dose reconstruction. A method to reconstruct dose for non-coplanar VMAT beams with 3DVH is described. The Delta(4) 3D dose reconstruction on its own phantom for VMAT delivery has not been thoroughly evaluated previously, and we do so by comparison with 3DVH. Reconstructed volumetric doses for VMAT plans delivered with different table angles were compared between the Delta(4) and 3DVH using gamma analysis. The average γ (2% local dose-error normalization/2mm) passing rate comparing the directly measured Delta(4) diode dose with 3DVH was 98.2 ± 1.6% (1SD). The average passing rate for the full volumetric comparison of the reconstructed doses on a homogeneous cylindrical phantom was 95.6 ± 1.5%. No dependence on the table angle was observed. Modified 3DVH algorithm is capable of 3D VMAT dose reconstruction on an arbitrary volume for the full range of table angles. Our comparison results between different dosimeters make a compelling case for the use of electronic arrays with high-resolution 3D dose reconstruction as primary means of evaluating spatial dose distributions during IMRT/VMAT verification.
Medical Physics, 2013
The effects of respiratory motion on the tumor dose can be divided into the gradient and interpla... more The effects of respiratory motion on the tumor dose can be divided into the gradient and interplay effects. While the interplay effect is likely to average out over a large number of fractions, it may play a role in hypofractionated [stereotactic body radiation therapy (SBRT)] treatments. This subject has been extensively studied for intensity modulated radiation therapy but less so for volumetric modulated arc therapy (VMAT), particularly in application to hypofractionated regimens. Also, no experimental study has provided full four-dimensional (4D) dose reconstruction in this scenario. The authors demonstrate how a recently described motion perturbation method, with full 4D dose reconstruction, is applied to describe the gradient and interplay effects during VMAT lung SBRT treatments. Methods: VMAT dose delivered to a moving target in a patient can be reconstructed by applying perturbations to the treatment planning system-calculated static 3D dose. Ten SBRT patients treated with 6 MV VMAT beams in five fractions were selected. The target motion (motion kernel) was approximated by 3D rigid body translation, with the tumor centroids defined on the ten phases of the 4DCT. The motion was assumed to be periodic, with the period T being an average from the empirical 4DCT respiratory trace. The real observed tumor motion (total displacement ≤8 mm) was evaluated first. Then, the motion range was artificially increased to 2 or 3 cm. Finally, T was increased to 60 s. While not realistic, making T comparable to the delivery time elucidates if the interplay effect can be observed. For a single fraction, the authors quantified the interplay effect as the maximum difference in the target dosimetric indices, most importantly the near-minimum dose (D 99%), between all possible starting phases. For the three-and five-fractions, statistical simulations were performed when substantial interplay was found. Results: For the motion amplitudes and periods obtained from the 4DCT, the interplay effect is negligible (<0.2%). It is also small (0.9% average, 2.2% maximum) when the target excursion increased to 2-3 cm. Only with large motion and increased period (60 s) was a significant interplay effect observed, with D 99% ranging from 16% low to 17% high. The interplay effect was statistically significantly lower for the three-and five-fraction statistical simulations. Overall, the gradient effect dominates the clinical situation. Conclusions: A novel method was used to reconstruct the volumetric dose to a moving tumor during lung SBRT VMAT deliveries. With the studied planning and treatment technique for realistic motion periods, regardless of the amplitude, the interplay has nearly no impact on the nearminimum dose. The interplay effect was observed, for study purposes only, with the period comparable to the VMAT delivery time.
Medical Physics, 2013
To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels f... more To present a framework for measurement-guided VMAT dose reconstruction to moving patient voxels from a known motion kernel and the static phantom data, and to validate this perturbation-based approach with the proof-of-principle experiments. As described previously, the VMAT 3D dose to a static patient can be estimated by applying a phantom measurement-guided perturbation to the treatment planning system (TPS)-calculated dose grid. The fraction dose to any voxel in the presence of motion, assuming the motion kernel is known, can be derived in a similar fashion by applying a measurement-guided motion perturbation. The dose to the diodes in a helical phantom is recorded at 50 ms intervals and is transformed into a series of time-resolved high-density volumetric dose grids. A moving voxel is propagated through this 4D dose space and the fraction dose to that voxel in the phantom is accumulated. The ratio of this motion-perturbed, reconstructed dose to the TPS dose in the phantom serves as a perturbation factor, applied to the TPS fraction dose to the similarly situated voxel in the patient. This approach was validated by the ion chamber and film measurements on four phantoms of different shape and structure: homogeneous and inhomogeneous cylinders, a homogeneous cube, and an anthropomorphic thoracic phantom. A 2D motion stage was used to simulate the motion. The stage position was synchronized with the beam start time with the respiratory gating simulator. The motion patterns were designed such that the motion speed was in the upper range of the expected tumor motion (1-1.4 cm∕s) and the range exceeded the normally observed limits (up to 5.7 cm). The conformal arc plans for X or Y motion (in the IEC 61217 coordinate system) consisted of manually created narrow (3 cm) rectangular strips moving in-phase (tracking) or phase-shifted by 90° (crossing) with respect to the phantom motion. The XY motion was tested with the computer-derived VMAT MLC sequences. For all phantoms and plans, time-resolved (10 Hz) ion chamber dose was collected. In addition, coronal (XY) films were exposed in the cube phantom to a VMAT beam with two different starting phases, and compared to the reconstructed motion-perturbed dose planes. For the X or Y motions with the moving strip and geometrical phantoms, the maximum difference between perturbation-reconstructed and ion chamber doses did not exceed 1.9%, and the average for any motion pattern∕starting phase did not exceed 1.3%. For the VMAT plans on the cubic and thoracic phantoms, one point exhibited a 3.5% error, while the remaining five were all within 1.1%. Across all the measurements (N = 22), the average disagreement was 0.5 ± 1.3% (1 SD). The films exhibited γ(3%∕3 mm) passing rates ≥90%. The dose to an arbitrary moving voxel in a patient can be estimated with acceptable accuracy for a VMAT delivery, by performing a single QA measurement with a cylindrical phantom and applying two consecutive perturbations to the TPS-calculated patient dose. The first one accounts for the differences between the planned and delivered static doses, while the second one corrects for the motion.
Medical Physics, 2010
Purpose: Image‐guidedradiation treatments routinely utilize radio‐opaque implantable devices, suc... more Purpose: Image‐guidedradiation treatments routinely utilize radio‐opaque implantable devices, such as fiducials or brachytherapy spacers, for improved spatial accuracy. We study the hypothesis that the therapeutic efficiency of IGRT can be enhanced through simultaneous in‐situ delivery of radiosensitizers, contained within nanoparticles and nanoporouspolymer matrices coatinggold fiducial markers or spacers implanted in the tumor (BIS‐IGRT, Biological In‐Situ Image‐Guided Radiation Therapy). Methods and Materials: Biocompatible polymers loaded with model molecules were coated as a thin film on gold fiducials. The nanoporous morphology of the polymercoatings allowed controlled release of molecules and nanoparticles. Two experimental approaches were studied: (i) a free drug release system, (Doxorubicin, a hydrophilic drug in Poly(methyl methacrylate (PMMA) coating) and (ii) Poly(D,L‐lactic‐co‐glycolic acid) (PLGA) nanoparticles loaded with Coumarin‐6, a fluorescent model for a hydrophobic drug, in a chitosan matrix applied as gold fiducial coating. Measurements of temporal release kinetics in buffer and spatial release profiles in agarose were carried out using fluorescence spectroscopy. Results: For gold fiducials coated with Doxorubicin in PMMA matrix an initial release of Dox within the first few hours was followed by a sustained release over the course of next 3 months. Release of Dox from within PMMA matrix is dependent on the concentration of Dox, ratio of PMMA/Dox, thickness of PMMA/Dox coating on gold surface. The release profile of coumarin‐6 loaded nanoparticles from chitosan film on gold fiducials showed that (63±10)% of NPs were released in twenty days, and after that, the release became slower and additional 37% of release was observed after additional twenty‐days. Spatial release profiles in an agarose phantom were also measured and compared with release kinetics models. Conclusions: The results show that dosage and rate of release of these radiosenstizers can be precisely tailored to achieve the desired release profile for BIS‐IGRT.
International Journal of Radiation Oncology*Biology*Physics, 2013
Physics in medicine and biology, Jan 21, 2010
Image-guided radiation treatments (IGRT) routinely utilize radio-opaque implantable devices, such... more Image-guided radiation treatments (IGRT) routinely utilize radio-opaque implantable devices, such as fiducials or brachytherapy spacers, for improved spatial accuracy. The therapeutic efficiency of IGRT can be further enhanced by biological in situ dose painting (BIS-IGRT) of radiosensitizers through localized delivery within the tumor using gold fiducial markers that have been coated with nanoporous polymer matrices loaded with nanoparticles (NPs). In this work, two approaches were studied: (i) a free drug release system consisting of Doxorubicin (Dox), a hydrophilic drug, loaded into a non-degradable polymer poly(methyl methacrylate) (PMMA) coating and (ii) poly(d,l-lactic-co-glycolic acid) (PLGA) NPs loaded with fluorescent Coumarin-6, serving as a model for a hydrophobic drug, in a biodegradable chitosan matrix. Temporal release kinetics measurements in buffer were carried out using fluorescence spectroscopy. In the first case of free Dox release, an initial release within the f...
Advances in Radiation Oncology, 2019
To characterize hippocampal dosimetry in Gamma Knife stereotactic radiosurgery (GK-SRS) for exten... more To characterize hippocampal dosimetry in Gamma Knife stereotactic radiosurgery (GK-SRS) for extensive brain metastases and evaluate the need for hippocampal-sparing in GK-SRS treatment planning. Methods and Materials: We reviewed 75 GK-SRS plans for the treatment of 4 to 30 brain metastases generated without consideration of the hippocampi. The mean dose, maximum dose to 100% of the volume (D 100), maximum dose to 40% of the volume (D 40), and maximum point dose (D max , 0.03 cm 3) were obtained for the unilateral and bilateral hippocampi and compared between plans with 4 to 9 and 10 lesions. The rate at which plans met hippocampal dose constraints (D 100 4.21 Gy, D 40 4.50 Gy, and D max 6.65 Gy) was compared between groups, and each was examined for risk factors associated with excessive hippocampal dosing. For plans that exceeded constraints, we attempted replanning to spare the hippocampi. Results: Compared with those for the treatment of 4 to 9 brain metastases, GK-SRS plans with 10 lesions were associated with significantly greater median bilateral mean dose (1.0 vs 2.0, P Z .001), D 100 (0.4 vs 0.8, P Z .003), D 40 (0.9 vs 1.9, P Z .001), and D max (2.0 vs 4.9, P Z .0005). These plans also less frequently met hippocampal constraints, with this difference trending toward significance (80% vs 93%; P Z .1382; odds ratio 0.29; 95% CI, 0.06-1.4). Risk factors for exceeding constraints included greater total disease volume and closer approach of the nearest metastasis to the hippocampi, both of which depended upon the number of metastases present. Seven plans failed to meet constraints and were successfully replanned to spare the hippocampi with minimal increases in treatment time and without compromise to target coverage or conformity. Conclusions: Patients with extensive brain metastases treated with GK-SRS are at increased risk for excessive hippocampal dosing when 10 lesions are present or when lesions are in close proximity to the hippocampi and may benefit from hippocampal-avoidant treatment planning.
Journal of Applied Clinical Medical Physics, 2021
This fictional case describes the challenging situation for a junior physicist, who joined her ho... more This fictional case describes the challenging situation for a junior physicist, who joined her hometown's cancer center as a solo physicist after graduating from residency. She is concerned about providing optimal patient care as well as improving her work/life balance. She wonders how to move forward. The intended use of the case study, in either a facilitated learning session or self‐study, is to inspire the readers to discuss the situation, analyze the institutional and personal factors, apply relevant leadership skills, and propose action plans. This case study falls under the scope of, and is supported by, the Medical Physics Leadership Academy (MPLA). A sample facilitator's guide or self‐study guide is available upon request to the MPLA Cases Subcommittee.
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Papers by Cassandra Stambaugh