PURPOSE:Brain arteriovenous malformations (AVMs) are high-risk vascular anomalies associated with hemorrhage, neurological morbidity, and mortality. Stereotactic radiosurgery (SRS) is a well-established, noninvasive treatment that achieves durable obliteration while preserving neurological function. This case-based guideline summarizes contemporary SRS-based AVM management and outcomes. METHODS AND MATERIALS:Three illustrative cases were selected: a small, unruptured Spetzler-Martin grade (SMG) I AVM treated with single-fraction SRS, a large SMG V AVM managed with volume-staged SRS, and a ruptured SMG II AVM treated with embolization followed by definitive SRS. RESULTS:Single-fraction SRS achieves durable obliteration for small AVMs, whereas staged approaches allow safe treatment of large or complex lesions and complement microsurgery and embolization. Treatment planning emphasizes integration of advanced imaging, precise nidus delineation, and dose-volume optimization. Long-term surveillance remains essential to confirm obliteration and detect delayed complications. CONCLUSIONS:This case-based guideline highlights practical principles of SRS for brain AVM management, emphasizing individualized selection, multidisciplinary collaboration, and meticulous planning to optimize safety and efficacy.

Brain metastases are significant sources of morbidity and mortality in patients with cancer. Potential minimally invasive treatment modalities include stereotactic radiosurgery (SRS) and laser interstitial thermal therapy (LITT), but comprehensive understanding of response profiles to such treatments is lacking. Our objective is to generate characteristic response curves quantifying post-contrast lesion enhancement leading up to and following SRS/LITT. Towards this end, we have established a computational pipeline that performs multi-modal registration of CT-simulation and longitudinal MRI studies, allowing long-term tracking of lesion responses pre- and post-treatment. As proof-of-concept, this pipeline was applied to three exemplar patients to generate characteristic response curves for treatment scenarios of varying complexity. Patient 1 received SRS to a single lesion that exhibited a complete response but recurred locally. Patient 2 received SRS to a single lesion that exhibited a partial response before rapidly progressing. Subsequent LITT re-established partial control with continued lesion involution at last follow-up. Patient 3 received SRS to six lesions that exhibited a mixture of complete and partial responses, two of which show signs of local recurrence in long-term follow-up. These proof-of-concept studies yielded characteristic response curves that model clinical course and response. With further optimization, we are applying this framework to 1500+ patients with 5000+ lesions to establish a comprehensive portfolio of characteristic response curves. This portfolio of lesion behavior will be integrated to construct a 4D brain map summarizing responses in both space and time following SRS and LITT. We envision construction of this atlas will enable evidence-based selection of optimal treatment modalities as well as provide accurate predictions of response and recurrence as a function of treatment type and lesion site.

Background: Tremor, either in patients with Essential Tremor (ET) or Parkinson's disease (PD), constitutes the most common movement disorder. Stereotactic radiosurgery using Gamma Knife (GK) and linear accelerator (LINAC) systems, is an effective, incisionless treatment modality for ET and PD. Although these technologies have been used clinically since the 1990 ' s, most studies have focused on GK, and efficacy, safety and time to treatment effect (latency) of GK and LINAC have not been compared. Objective: We therefore aimed to conduct a systematic review with network meta-analysis examining efficacy, adverse events (AEs) and latency of GK and LINAC for treating tremor in ET and PD. Methods: We conducted a systematic review with network meta-analysis in accordance with PRISMA guidelines, using the Embase and PubMed databases. We included all primary GK/LINAC thalamotomy studies in ET/PD patients with at least 6 months of follow-up, reporting unilateral Fahn-Tolosa-Marin Tremor Scale (FTM-TRS) or Unified Parkinson's disease rating scale (UPDRS) scores pre-treatment/post-treatment and/or AEs and/or latency. The primary efficacy outcome was FTM-TRS Scale A or UPDRS Item 16 score reduction. AEs were presented as an estimated incidence, and latency as average time to first recorded clinical improvement in tremor. Results: Six studies of 311 patients and 2 studies of 60 patients met inclusion criteria for GK/LINAC efficacy comparison, respectively. Network meta-analysis showed similar tremor reduction between modalities (standardized mean difference between preand post-treatment scores: GK:-2.18 (95 % CI:-2.79,-1.57); LINAC:-2.13 (95 % CI:-5.13, 0.87). GK also had a higher absolute AE rate, while LINAC was associated with a greater latency period. There was no correlation between GK efficacy and AE rate. Conclusions: Despite the relatively small sample sizes, these results demonstrate similar efficacy between GK and LINAC for ET and PD, with a trend toward higher efficacy but greater AE incidence and slower onset of tremor improvement in GK compared to LINAC.

BACKGROUND AND PURPOSE:Re-irradiation for recurrent head and neck cancer is associated with poor local control and significant treatment-related toxicity. We hypothesized that automated non-coplanar volumetric modulated arc therapy (VMAT) can deliver more conformal, dose-escalated stereotactic body radiotherapy (SBRT) plans than conventional VMAT, which may improve local control without increasing toxicity. MATERIALS AND METHODS:This was a single-arm, phase II trial that enrolled patients with histologically-confirmed, recurrent head and neck cancer (diameter < 5 cm) with prior head and neck radiotherapy. Patients were planned for treatment using both conventional VMAT (≤40 Gy) and automated non-coplanar VMAT (≤55 Gy) in 5 every-other-day fractions. Non-coplanar VMAT plans were selected if they could deliver higher planning target volume doses without higher organ-at-risk doses. The primary endpoints were one-year local control (compared to the historical rate of 60 % with SBRT using conventional VMAT) and one-year grade ≥ 3 treatment-related toxicity (compared to the historical rate of 20 %). Local control was estimated via Kaplan-Meier method. Toxicities were graded using Common Terminology Criteria for Adverse Events, v5.0. RESULTS:Twenty-nine patients were enrolled between February 2020-November 2023. Median follow-up was 18.1 months (interquartile range, 10.9-36.3). Non-coplanar VMAT plans were selected over conventional VMAT for all patients. One-year local control was 83.8 % (95 % confidence interval [CI], 62.4-93.6 %). One-year grade ≥ 3 toxicity was 17.4 %. CONCLUSION:Automated non-coplanar VMAT achieved superior one-year local control compared to the historical local control rate without higher grade ≥ 3 toxicity. This represents one of the highest local control rates reported in a prospective trial of head and neck re-irradiation and a new approach to head and neck SBRT.

Abstract BACKGROUND Accurate differentiation between radiation necrosis and tumor progression or recurrence in patients treated with stereotactic radiosurgery for brain metastases is critical for guiding clinical management. This study leverages the advanced natural language processing capabilities of Meta Llama3, an artificial intelligence (AI) large language model (LLM), combined with prompt engineering, to rapidly categorize brain magnetic resonance imaging (MRI) radiology reports. Our objective was to develop an automated scoring system to classify concern for radiation necrosis, tumor progression, equivocal findings, or stable exams. METHODS Using a comprehensive dataset of reports annotated by expert radiologists, we ran inference on a 70-billion parameter Llama3 model (temperature 0.2, top_p 0.9) with specific prompts designed to capture the nuanced language and diagnostic criteria related to radiation necrosis or tumor progression. RESULTS The first pass was performed on a training dataset of 107 reports and did not predefine the clinical conditions. This demonstrated 43.4% accuracy in scoring when compared to a human user’s classification of each report. Agreement between the human reader and Llama3 was assessed using the Gwet agreement coefficient, AC1=0.411 (99%CI 0.396-0.426). Multiple iterations of targeted prompt engineering were then employed to narrow the definition of radiation necrosis and tumor progression, with specific examples and nuanced language used to achieve a higher degree of accuracy at 72.0%, AC1=0.719 (99%CI 0.717-0.722). DISCUSSION/FUTURE DIRECTIONS This surpasses recent demonstration of lower human-LLM agreement in radiographic score assignment, with further room for calibration on a dataset of several thousand reports. Next, we will correlate automated interpretations with actual clinical management decisions for radiation necrosis (e.g., initiation of steroids, bevacizumab, Laser Interstitial Thermal Therapy, and/or repeat imaging). This automated scoring system holds significant potential for LLMs in clinical applications. Future work will focus on integrating this model into clinical workflows and expanding its capabilities to include longitudinal monitoring of patient outcomes.

Extramedullary hematopoiesis (EMH) is an uncommon phenomenon that arises following inadequate blood cell production from the bone marrow. Bone marrow dysfunction can be caused by several etiologies including various hereditary genetic hematologic abnormalities (e.g. thalassemia), hemolytic anemias, certain infectious diseases, autoimmune disorders (e.g. ITP), primary myelofibrosis, and myeloproliferative neoplasms (e.g. polycythemia vera, essential thrombocytopenia, chronic myeloid leukemia, and primary myelofibrosis).

OBJECTIVE:Although seizures are a relatively common phenomenon in the setting of brain metastases (BMs), there are no discrete recommendations regarding the use of antiepileptic drugs (AEDs) in this population, either in general or in the context of treatment. The authors' aim was to better understand the underlying pathological factors as well as the therapeutic techniques that may lead to seizures following the radiosurgical treatment of BMs with the goal of guiding appropriate AED prophylaxis.METHODS:Adult patients with BMs diagnosed from 2013 to 2020 at a single academic institution and treated with radiation therapy were included in this study. The authors evaluated factors associated with the incidence of seizures throughout the disease course, with a focus on seizures in the 90-day period following stereotactic radiosurgery (SRS).RESULTS:Four hundred forty-four patients with newly diagnosed BMs were identified, 10% of whom had seizures at the time of presentation and 28% of whom had a seizure at any point during the study period. Tumor histology was significantly associated with initial seizure risk. AED use was highly variable. In the 90-day post-SRS period, the summed total planning target volume (PTV) was independently predictive of post-SRS seizures, regardless of the fractionation scheme (single fraction vs hypofractionated) and other clinical factors. The number of supratentorial BMs was not predictive of post-SRS seizures.CONCLUSIONS:PTV is a superior predictor of post-SRS seizures relative to the number of supratentorial BMs, as it serves as a volumetric proxy for intracranial disease burden. A larger PTV, alongside tumor histology and prior seizure history, should be considered in the decision-making process for AED use following radiosurgery.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide. 1 Centers for Disease Control and Prevention. An update on cancer deaths in the United States. Available at: https://www.cdc.gov/cancer/dcpc/research/update-on-cancer-deaths/index.htm. Accessed October 27, 2022. Google Scholar Around 16% of patients present with localized disease, of whom around 25% will not be surgical candidates. 2 National Cancer Institute. SEER cancer statistics review 1975-2015. Available at: https://seer.cancer.gov/archive/csr/1975_2015/results_merged/sect_15_lung_bronchus.pdf. Accessed February 18, 2023. Google Scholar ,3 Choi JI. Medically inoperable stage I non-small cell lung cancer: Best practices and long-term outcomes. Transl Lung Cancer Res. 2019; 8: 32-47 Crossref PubMed Scopus (13) Google Scholar In 2003, lung SABR for medically inoperable patients was first studied in the United States by Timmerman and colleagues with excellent safety and efficacy. 4 Timmerman R Papiez L McGarry R et al. Extracranial stereotactic radioablation: Results of a phase I study in medically inoperable stage I non-small cell lung cancer. Chest. 2003; 124: 1946-1955 Abstract Full Text Full Text PDF PubMed Scopus (616) Google Scholar Despite durable local control (LC), longer follow-up revealed metachronous locoregional and distant failure rates up to 30% to 40%. 5 Timmerman RD Hu C Michalski J et al. Long-term results of RTOG 0236: A phase II trial of stereotactic body radiation therapy (SBRT) in the treatment of patients with medically inoperable stage I non-small cell lung cancer. Int J Radiat Oncol Biol Phys. 2014; 90: S30 Abstract Full Text Full Text PDF Google Scholar ,6 Videtic GM Paulus R Singh AK et al. Long-term follow-up on NRG Oncology RTOG 0915 (NCCTG N0927): A randomized phase 2 study comparing 2 stereotactic body radiation therapy schedules for medically inoperable patients with stage I peripheral non-small cell lung cancer. Int J Radiat Oncol Biol Phys. 2019; 103: 1077-1084 Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar

This study reports the initial results for the first 15 patients on a prospective phase II clinical trial exploring the safety, feasibility, and efficacy of the HyperArc technique for recurrent head and neck cancer treatment. Eligible patients were simulated and planned with both conventional VMAT and HyperArc techniques and the plan with superior dosimetry was selected for treatment. Dosimetry, delivery feasibility and safety, treatment-related toxicity, and patient-reported quality of life (QOL) were all evaluated. HyperArc was chosen over conventional VMAT for all 15 patients and enabled statistically significant increases in dose conformity (R50% reduced by 1.2 ± 2.1, p < 0.05) and mean PTV and GTV doses (by 15.7 ± 4.9 Gy, p < 0.01 and 17.1 ± 6.0 Gy, p < 0.01, respectively). The average HyperArc delivery was 2.8 min longer than conventional VMAT (p < 0.01), and the mean intrafraction motion was ≤ 0.5 ± 0.4 mm and ≤0.3 ± 0.1°. With a median follow-up of 12 months, treatment-related toxicity was minimal (only one grade 3 acute toxicity above baseline) and patient-reported QOL metrics were favorable. HyperArc enabled superior dosimetry and significant target dose escalation compared to conventional VMAT planning, and treatment delivery was feasible, safe, and well-tolerated by patients.

Radiation oncology practices use a suite of dedicated software and hardware that are not common to other medical subspecialties, making radiation treatment history inaccessible to colleagues. A radiation dose distribution map is generated for each patient internally that allows for visualization of the dose given to each anatomic structure volumetrically; however, this crucial information is not shared systematically to multidisciplinary medical, surgery, and radiology colleagues. A framework was developed in which dose distribution volumes are uploaded onto the medical center's picture archiving and communication system (PACS) to rapidly retrieve and review exactly where, when, and to what dose a lesion or structure was treated. The ability to easily visualize radiation therapy information allows radiology clinics to incorporate radiation dose into image interpretation without direct access to radiation oncology planning software and data. Tumor board discussions are simplified by incorporating radiation therapy information collectively in real time, and daily onboard imaging can also be uploaded while a patient is still undergoing radiation therapy. Placing dose distribution information into PACS facilitates central access into the electronic medical record and provides a succinct visual summary of a patient's radiation history for all medical providers. More broadly, the radiation dose map provides greater visibility and facilitates incorporation of a patient's radiation history to improve oncologic decision making and patient outcomes. Keywords: Brain/Brain Stem, CNS, MRI, Neuro-Oncology, Radiation Effects, Radiation Therapy, Radiation Therapy/Oncology, Radiosurgery, Skull Base, Spine, Technology Assessment Supplemental material is available for this article. © RSNA, 2021 See also commentary by Khandelwal and Scarboro in this issue.

Purpose The aim of this study is to evaluate the patient positioning and intra-fraction motion management performance of an image-guidance protocol established for radiosurgical treatments of trigeminal neuralgia patients. Specifically, it also aims to analyze patient motion data for the evaluation of current motion tolerance levels and imaging frequency utilized for repositioning patients. Methods A linear accelerator equipped with ExacTrac is used for patient positioning with stereoscopic imaging and treatments. Treatments are delivered with 4-mm conical collimators using seven equally spaced arcs. Arcs are 20 degrees apart and span 100 arc degrees each. Following initial ExacTrac positioning, cone beam computed tomography (CBCT) is obtained for independent confirmation of patient position. Patients are then stereoscopically imaged prior to the delivery of each arc and repositioned when 0.5-mm translational tolerance in any direction is exceeded. After the patient has been repositioned, verification stereoscopic images are obtained. Data from 48 patients with 607 image pairs were analyzed for this study. Results Over the course of 48 patient treatments, the mean magnitude of mean 3D deviations was 0.64 mm ± 0.12 mm (range: 0.07-2.74 mm). With the current 0.50-mm tolerance level for repositioning, patients exceeded the tolerance 51.4% of the time considering only images following an arc segment. For those instances, patients were repositioned with a mean magnitude of 0.85 mm ± 0.15 mm (1 SD). For a 0.25-mm tolerance level, 86.1% of arc segments would have required repositioning following the delivery of an arc segment, with a mean magnitude of 0.68 mm ± 0.12 mm. Conversely, for 0.75-mm and 1.00-mm tolerance levels, the tolerance would have been exceeded only 21.5% and 6.6% of instances following the delivery of an arc segment, with a mean magnitude of 1.08 mm ± 0.21 mm and 1.34 mm ± 0.24 mm, respectively. Each repositioning adds approximately 2 minutes to treatment time, which accounts for parts of the variability in patient treatment times. Following the initial ExacTrac and CBCT, the mean treatment time from first arc to treatment end was 57 minutes (range: 33-63 minutes). Discussions The current 0.50-mm tolerance level results in a clinically manageable but significant number of patient repositions during trigeminal neuralgia treatments. Frequent patient repositioning can result from actual patient motion convolved with the accuracy and precision limitations of the image analysis. Increasing the repositioning tolerance could more selectively correct for actual patient motion and shorten the treatment time at the expense of more variations in patient position. A more lenient tolerance level of 0.75 mm would decrease the repositioning rate by approximately a factor of 2; however, the permissible magnitude of motion will increase, leading to possible dosimetric consequences. Once treatment begins, there was no trend as to when patients exceeded the tolerance. Conclusions Current imaging protocol for patient positioning and intra-fraction motion management fits the clinical workflow with clinically acceptable residual patient motion. The next important step would be to assess how the number of repositions and magnitude of residual movements affect treatment outcomes.

C57BL/6 and DBA/2 were compared in the 5-choice serial reaction time task for differences in performance related to attention and impulsivity. The goal was to examine behavioural processes in mice that may relate to ADHD in humans. Groups of male mice were trained to nose-poke in response to a stimulus light presented randomly in one of five holes; correct responses were reinforced with food. During training the stimulus duration (SD) was reduced progressively from 60 to 0.5s. The C57BL/6 and DBA/2 mice did not differ during early stages of training when attentional demands were low (SD of 60, 10 or 5s). As task demands increased, strain differences emerged; C57BL/6 mice were more accurate than DBA/2 mice with stimuli of 2, 1 and 0.5s. DBA/2 mice also made more anticipatory (impulsive) responses during inter-trial intervals than C57BL/6 mice at SD of 5, 2, 1 and 0.5s. The ability to carry out the task was present in both strains of mice but they differed significantly in the levels of performance that were achieved. It is argued that the differences in accuracy and anticipatory responding were closely related and that the primary difference between the strains may be in impulsivity.

Purpose/objective(s) To communicate our institutional experience with single isocenter radiosurgery treatments for multiple brain metastases, including challenges with determining planning target volume (PTV) margins and resulting consequences, image-guidance translational and rotational tolerances, intra-fraction patient motion, and prescription considerations with larger PTV margins. Materials/methods Eight patient treatments with 51 targets were planned with various margins using Elements Multiple Brain Mets SRS treatment planning software (Brainlab, Munich, Germany). Forty-eight plans with 0 mm, 1 mm and 2 mm margins were created, including plans with variable margins, where targets more than 6 cm away from the isocenter were planned with larger margins. The dosimetric impact of the margins were analyzed with V5Gy, V8Gy, V10Gy, V12Gy values. Additionally, 12 patient motion data were analyzed to determine both the impact of the repositioning threshold and the distributions of the patient translational and rotational movements. Results The V5Gy, V8Gy, V10Gy, V12Gy volumes approximately doubled when margins change from 0 to 1 mm and tripled when change from 0 to 2 mm. With variable margins, the aggregated results are similar to results from plans using the lower of two margins, since only 12.2% of the targets were more than 6 cm away from the isocenter. With 0.5 mm re-positioning threshold, 57.4% of the time the patients are repositioned. Reducing the threshold to 0.25 mm results in 91.7% repositioning rate, due to limitations of the fusion algorithm and actual patient motion. The 90th percentile of translational movements in all directions is 0.7 mm, while the 90th percentile of rotational movements in all directions is 0.6 degrees. Median translations and rotations are 0.2 mm and 0.2 degrees, respectively. Conclusions Based on the data presented, we have switched our modus operandi from 2 to 1 mm PTV margins, with an eventual goal of using 0.5 and 1.0 mm variable margins when an automated margin assignment method becomes available. The 0.5 mm and 0.5 degrees repositioning thresholds are clinically appropriate with small residual patient movements.

OBJECTIVE:Precise and accurate targeting is critical to optimize outcomes after stereotactic radiosurgery (SRS) for trigeminal neuralgia (TN). The aim of this study was to compare the outcomes after SRS for TN in which two different techniques were used: mask-based 4-mm cone versus frame-based 5-mm cone. METHODS:The authors performed a retrospective review of patients who underwent SRS for TN at their institution between 1996 and 2019. The Barrow Neurological Institute (BNI) pain score and facial hypesthesia scale were used to evaluate pain relief and facial numbness. RESULTS:A total of 234 patients were included in this study; the mean age was 67 years. In 97 patients (41.5%) radiation was collimated by a mask-based 4-mm cone, whereas a frame-based 5-mm cone was used in the remaining 137 patients (58.5%). The initial adequate pain control rate (BNI I-III) was 93.4% in the frame-based 5-mm group, compared to 87.6% in the mask-based 4-mm group. This difference between groups lasted, with an adequate pain control rate at ≥ 24 months of 89.9% and 77.8%, respectively. Pain relief was significantly different between groups from initial response until the last follow-up (≥ 24 months, p = 0.02). A new, permanent facial hypesthesia occurred in 30.3% of patients (33.6% in the frame-based 5-mm group vs 25.8% in the mask-based 4-mm group). However, no significant association between the BNI facial hypesthesia score and groups was found. Pain recurrence occurred earlier (median time to recurrence 12 months vs 29 months, p = 0.016) and more frequently (38.1% vs 20.4%, p = 0.003) in the mask-based 4-mm than in the frame-based 5-mm group. CONCLUSIONS:Frame-based 5-mm collimator SRS for TN resulted in a better long-term pain relief with similar toxicity profiles to that seen with mask-based 4-mm collimator SRS.

Acute seizure following radiotherapy (RT) for brain metastases is an infrequent but significant adverse event that has not been well-described. Prophylactic antiepileptic drug (AED) or steroid therapy is not recommended for asymptomatic lesions. However, there is minimal data incorporating individualized factors into acute seizure risk-assessment with respect to RT. We retrospectively examined patients treated for brain metastases with any RT modality from 2013-2020 who experienced acute post-treatment seizure, which we defined as within 4 weeks post-RT. Twenty patients experienced acute seizure at median 2 days post-treatment (range 0-27); 15 (75%) within 7 days and 7 (35%) on day 0 (radiosurgery date or during fractionated RT). Seizures occurred after radiosurgery (n=9, 45%), fractionated stereotactic RT (n=3, 15%), whole-brain RT (n=5, 25%), and post-operative RT (n=3, 15%). All RT encompassed at least one supratentorial lesion; 11 (55%) had >1 lesion treated. Median lesion size was 23mm (range 7-51mm). Moderate-to-severe perilesional edema was present in 12 (60%) and hemorrhage in 8 (40%) cases. Seizures occurred despite AED therapy in 8 (40%) overall; 5/8 (63%) were hemorrhagic and 7/8 (88%) had moderate-to-severe edema. Nine (45%) patients receiving steroids developed seizures. Primary pathologies were: melanoma (5), non-small cell lung (5), renal cell carcinoma (4), breast (3), colon (1), Merkel cell (1), and thyroid (1). Patients with melanoma who developed acute seizure had mainly non-hemorrhagic (80%), small lesions (median 9mm), not receiving AED (0%) or steroid (20%) therapy. In acute post-RT seizure, lesions were predominantly supratentorial, >23mm, and had moderate-to-severe edema. Breakthrough seizures were common in edematous and/or hemorrhagic lesions. However, acute seizure also occurred with smaller, non-hemorrhagic melanoma lesions not receiving AED therapy. A larger series is needed to further evaluate these identified characteristics in acute seizure, and whether prophylactic therapy may be appropriate.

Purpose Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) are noninvasive therapies for vestibular schwannomas providing excellent tumor control. However, delayed hearing loss after radiation therapy remains an issue. One potential target to for improving hearing rates is limiting radiation exposure to the cochlea. Methods We retrospectively reviewed 100 patients undergoing either SRS with 12 Gy (n = 43) or fSRT with 50 Gy over 28 fractions (n = 57) for vestibular schwannoma. Univariate and multivariate analysis were carried out to identify predictors of hearing loss as measured by the Gardner Robertson scale after radiation therapy. Results Deterioration of hearing occurred in 30% of patients with SRS and 26% with fSRT. The overall long term (> 2 year) progression rates were 20% for SRS and 16% for fSRT. Patients with a decrease in their Gardner Robertson hearing score and those that loss serviceable hearing had significantly higher average minimal doses to the cochlea in both SRS and fSRT cohorts. ROC analysis showed that a cut off of 5 Gy and 35 Gy, for SRS and fSRT respectively, predicted hearing loss with high sensitivity/specificity. Conclusion Our data suggests the minimal dose of radiation that the cochlear volume is exposed to is a predictor of delayed hearing loss after either SRS or fSRT. A threshold of 5 Gy/35 Gy may lead to improved hearing preservation after radiotherapy. Further prospective multi center studies can further elucidate this mechanism.

PURPOSE:In-house software is commonly employed to implement new imaging and therapy techniques before commercial solutions are available. Risk analysis methods, as detailed in the TG-100 report of the American Association of Physicists in Medicine, provide a framework for quality management of processes but offer little guidance on software design. In this work, we examine a novel model-based four-dimensional computed tomography (4DCT) protocol using the TG-100 approach and describe two additional methods for promoting safety of the associated in-house software.METHODS:To implement a previously published model-based 4DCT protocol, in-house software was necessary for tasks such as synchronizing a respiratory signal to computed tomography images, deformable image registration (DIR), model parameter fitting, and interfacing with a treatment planning system. A process map was generated detailing the workflow. Failure modes and effects analysis (FMEA) was performed to identify critical steps and guide quality interventions. Software system safety was addressed through writing "use cases," narratives that characterize the behavior of the software, for all major operations to elicit safety requirements. Safety requirements were codified using the easy approach to requirements syntax (EARS) to ensure testability and eliminate ambiguity.RESULTS:Sixty-one failure modes were identified and assigned risk priority numbers using FMEA. Resultant quality management interventions include integration of a comprehensive reporting and logging system into the software, mandating daily and monthly equipment quality assurance procedures, and a checklist to be completed at image acquisition. Use cases and resulting safety requirements informed the design of needed in-house software as well as a suite of tests performed during the image generation process.CONCLUSIONS:TG-100 methods were used to construct a process-level quality management program for a 4DCT imaging protocol. Two supplemental tools from the field of requirements engineering facilitated elicitation and codification of safety requirements that informed the design and testing of in-house software necessary to implement the protocol. These general tools can be applied to promote safety when in-house software is needed to bring new techniques to the clinic.