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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.

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.

The purpose of this paper is to summarize treatment guidelines for the performance of single isocenter LINAC radiosurgery of multiple brain metastases developed and used by 3 experienced centers. This article is not meant to provide consensus guidelines. Rather, this is a practical, "how we do it" reference without substantial discussion. To serve as a treatment reference, the great majority of the information is presented in topic-specific tables.

PURPOSE The thermoluminescence dosimeter (TLD) has desirable features including low cost, reusability, small size, and relatively low energy dependence. However, the commonly available poly-crystal TLDs (e.g., TLD-100) exhibit high interdetector variability that requires individual calibration for high detection accuracy. To improve individual TLD tracking robustness, we developed an optical fingerprinting method to identify the TLD-100 chips. METHODS Seven hundred and fifty-two images were initially captured using a digital microscope camera to build a feature library for both facets of 376 TLD-100 chips. A median intensity thresholding method was used to segment images into foreground and background. The affine transformation was used to register the segmented images to the same position. The fingerprint of each image was calculated from its registered image. All fingerprints were then recorded in an Elasticsearch® search database. The TLD fingerprint match was tested three times when the library was established and repeated once 20 months later. All chips were irradiated at 0, 1, 4, and 8 Gy on a calibrated clinical MV linac to establish the individual calibration curve. RESULTS The true positive rate of identifying TLDs based on their optical fingerprints was 100% at initialization of the inventory. After 20 months and multiple deployments for characterization, calibration, and dose measurement, the true positive match rate dropped to 99% with zero false-positive matches. The TLDs exhibited high self-consistency in the dose-response test with R2 between 0.988 and 1 with linear regression. CONCLUSIONS The TLD-100 chips surface textures are unique and sufficient to support accurate identification based on the optical fingerprinting. This method provides inexpensive and robust management of the TLDs for individual calibration and dosimetry.

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. 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. 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. 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.

This study evaluates the potential for tumor dose escalation in recurrent head and neck cancer (rHNC) patients with automated non-coplanar volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) planning (HyperArc). Twenty rHNC patients are planned with conventional VMAT SBRT to 40 Gy while minimizing organ-at-risk (OAR) doses. They are then re-planned with the HyperArc technique to match these minimal OAR doses while escalating the target dose as high as possible. Then, we compare the dosimetry, tumor control probability (TCP), and normal tissue complication probability (NTCP) for the two plan types. Our results show that the HyperArc technique significantly increases the mean planning target volume (PTV) and gross tumor volume (GTV) doses by 10.8 ± 4.4 Gy (25%) and 11.5 ± 5.1 Gy (26%) on average, respectively. There are no clinically significant differences in OAR doses, with maximum dose differences of &lt, 2 Gy on average. The average TCP is 23% (± 21%) higher for HyperArc than conventional plans, with no significant differences in NTCP for the brainstem, cord, mandible, or larynx. HyperArc can achieve significant tumor dose escalation while maintaining minimal OAR doses in the head and neck—potentially enabling improved local control for rHNC SBRT patients without increased risk of treatment-related toxicities.

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.

INTRODUCTION 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. METHODS 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. RESULTS 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. CONCLUSIONS 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) historically has been used to treat multiple brain lesions using a multiple-isocenter technique-frequently associated with significant complexity in treatment planning and long treatment times. Recently, given innovations in planning algorithms, patients with multiple brain lesions may now be treated with a single-isocenter technique using fewer total arcs and less time spent during image guidance (though with stricter image guided radiation therapy tolerances). This study used time-driven activity-based costing to determine the difference in cost to a provider for delivering SRS to multiple brain lesions using single-isocenter versus multiple-isocenter techniques. METHODS AND MATERIALS Process maps, consisting of discrete steps, were created for each phase of the SRS care cycle and were based on interviews with department personnel. Actual treatment times (including image guidance) were extracted from treatment record and verify software. Additional sources of data to determine costs included salary/benefit data of personnel and average list price/maintenance costs for equipment. RESULTS Data were collected for 22 patients who underwent single-isocenter SRS (mean lesions treated, 5.2; mean treatment time, 30.2 minutes) and 51 patients who underwent multiple-isocenter SRS (mean lesions treated, 4.4; mean treatment time, 75.2 minutes). Treatment time for multiple-isocenter SRS varied substantially with increasing number of lesions (11.8 minutes/lesion; P < .001), but to a much lesser degree in single-isocenter SRS (1.8 minutes/lesion; P = .029). The resulting cost savings from single-isocenter SRS based on number of lesions treated ranged from $296 to $3878 for 2 to 10 lesions treated. The 2-mm planning treatment volume margin used with single-isocenter SRS resulted in a mean 43% increase of total volume treated compared with a 1-mm planning treatment volume expansion. CONCLUSIONS In a comparison of time-driven activity-based costing assessment of single-isocenter versus multiple-isocenter SRS for multiple brain lesions, single-isocenter SRS appears to save time and resources for as few as 2 lesions, with incremental benefits for additional lesions treated.

Stereotactic accuracy and target engagement largely rely on rigid immobilization of the skull. However, advanced imaging, image reconstructions, and adaptive treatment algorithms have made frameless image guidance without rigid immobilization a mainstay of stereotactic radiosurgery and radiotherapy deliveries. While these methods for achieving stereotactic precision require some immobilization, these obviate the need for an invasive head ring fixation. Because these approaches allow the target to still move to some degree and this movement must be compensated for, frameless image guidance requires intra-treatment imaging and target tracking and, critically, requires verification of accuracy. In this chapter, the different approaches are described, including key technological features of various frameless image-guided approaches. The anticipation is that these methods, which are primarily used for stereotactic radiosurgery, will continue to evolve to incorporate other imaging modalities, such as MRI, and eventually be generalized to other stereotactic procedures.

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.

Vestibular schwannomas (VS) are benign tumors stemming from the eighth cranial nerve. Treatment options for VS include conservative management, microsurgery, stereotactic radiosurgery, and fractionated radiotherapy. Though microsurgery has been the standard of care for larger lesions, hypo-fractionated stereotactic radiotherapy (hypo-FSRT) is an emerging modality. However, its clinical efficacy and safety have yet to be established. We conducted a systematic review and meta-analysis of manuscripts indexed in PubMed, Scopus, Web of Science, Embase, and Cochrane databases reporting outcomes of VS cases treated with hypo-FSRT. Five studies representing a total of 228 patients were identified. Across studies, the pooled rates of tumor control, hearing, facial nerve, and trigeminal nerve preservation were 95%, 37%, 97%, and 98%. No instances of malignant induction were observed at median follow-up of 34.8 months. Complications included trigeminal neuropathy (n = 3), maxillary paresthesia (n = 1), neuralgia (n = 1), vestibular dysfunction (n = 1), radionecrosis (n = 1), and hydrocephalus (n = 1). Hypo-FSRT may be another useful approach to manage VS, but studies with extended follow-up times are required to establish long-term safety.

Objective Neurofibromatosis type 2 (NF2) is an autosomal dominant disease characterized by bilateral vestibular schwannomas (VSs). NF2-associated VSs (NF2-VSs) are routinely treated with microsurgery; however, stereotactic radiosurgery (SRS) has emerged as an effective alternative in recent decades. To elucidate the role of SRS in NF2-VSs, a systematic review of the literature was conducted to compare outcomes of SRS versus surgery. Methods PubMed, Web of Science, Scopus, Embase, and Cochrane databases were queried using relevant search terms. Retrospective studies investigating outcomes of NF2-VS patients treated with either SRS or surgery were included. Single-patient case reports were excluded. Outcome measures between the SRS and surgery groups were compared using χ 2 2-sample tests for equality of proportions on the pooled patient data. Results A total of 974 patients (485 SRS, 489 surgery) were identified. The mean 5-year local control rate for SRS was 75.1%, and the mean recurrence rate for surgery was 8.1%. The mean hearing and facial nerve preservation rates were 40.1% and 92.3%, respectively, for SRS and 52.0% and 75.7%, respectively, for surgery. Rates of hearing preservation were higher after surgery than after SRS ( P = 0.006), whereas rates of facial nerve preservation were higher after SRS than after surgery ( P Conclusions SRS appears to be a safe and effective alternative to surgery for NF2-VS. Although rates of hearing preservation were higher in the surgery cohorts, SRS demonstrated high rates of local control and significantly lower facial nerve complications. Certain patients may therefore benefit more from SRS than surgery.

Objective The objective of this study was to examine the effect of cochlear dose on hearing preservation in stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) for vestibular schwannoma (VS). Design This is a retrospective case–control study. Setting This study was completed at the Ronald Reagan UCLA Medical Center, a university-affiliated tertiary care center. Participants Patients who underwent SRS (marginal dose of 12 Gy) or fSRT (marginal dose of 50.4 Gy) procedures for VS were included in the study. Main Outcome Measures The main outcome measure was hearing preservation. Audiometric data, when available, were used to determine the level of hearing according to the Gardner Robertson scale. Results A total of 38 patients (14 SRS and 24 fSRT) were analyzed. SRS patients with decreased hearing received a significantly higher minimum cochlear dose (7.41 vs. 4.24 Gy, p = 0.02) as compared with those with stable hearing. In fSRT patients, there were no significant differences in cochlear dose for patients with decreased hearing as compared with those with stable hearing. For SRS patients, who received a minimum cochlear dose above 6 Gy, there was a significant risk of decreased hearing preservation (odds ratio: 32, p = 0.02). Conclusion Higher minimum cochlear dose was predictive of decreased hearing preservation following SRS. Though the study is low powered, the radiation dose to the cochlea should be a parameter that is considered when planning SRS or fSRT therapies for patients with VS.

Purpose Stereotactic radiosurgery (SRS) provides a noninvasive treatment modality for patients with medically refractory trigeminal neuralgia. The root entry zone (REZ) has been proposed to be an ideal stereotactic target because it is partially composed of centrally produced myelin, conferring a theoretical increased sensitivity to irradiation as well as increased susceptibility to neurovascular conflict, making it the site in which nociceptive signals likely arise. The aim of this study is to determine if there is a statistically and clinically significant difference in pain relief or facial hypesthesia following SRS based on distance of the stereotactic isocenter from REZ. Methods and materials Patients undergoing Novalis radiosurgery for the treatment of trigeminal neuralgia with at least 3 months' follow-up were included in this study. Postoperative outcomes were stratified by Barrow Neurological Institute (BNI) score for pain relief and BNI facial numbness score for facial hypesthesia. Results Sixty-seven patients met inclusion criteria and were included in this study. BNI score of I-IIIa was attained in 82% of patients at 3 months and 65% at 1 year following SRS. Distance from isocenter to REZ varied from 0 to 8.6 mm, with a mean of 1.94 ± 1.62 mm. Logistic regression of target-REZ distance against pain relief outcome (patients with score I-IIIa and IIIb-V) was insignificant at 3 months ( P = .988), 6 months ( P = .925), 9 months ( P = .845), and 12 months ( P = .547) postoperatively. Furthermore, no significant correlation was found with logistic regression of target-REZ distance with pain relief outcome (patients with score I and score II-IV) ( P = .544). Conclusions The current analysis suggests that distance from REZ does not correlate with degree of postoperative pain relief or facial hypesthesia; thus, targeting specific regions within the trigeminal nerve in relation to these anatomical characteristics may not afford any advantage from this perspective.

Purpose To investigate the accuracy of 4D dose accumulation using projection of dose calculated on the end-exhalation, mid-ventilation, or average intensity breathing phase CT scan, versus dose accumulation performed using full Monte Carlo dose recalculation on every breathing phase. Methods Radiotherapy plans for 10 patients with stage I-II lung cancer were analyzed. All patients had respiratory-correlated computed tomography (4D-CT) performed as part of an IRB-approved research protocol. Stereotactic body radiotherapy (SBRT) plans were optimized using the dose calculated by a commercially-available Monte Carlo algorithm on the end-exhalation 4D-CT phase. 4D dose accumulations using deformable registration were performed with a commercially available tool that projected the planned dose onto every breathing phase without recalculation, as well as with a Monte Carlo recalculation of the dose on all breathing phases. The 3D planned dose (3D-EX), the 3D dose calculated on the average intensity image (3D-AVE), and the 4D accumulations of the dose calculated on the end-exhalation phase CT (4D-PR-EX), the mid-ventilation phase CT (4D-PR-MID), and the average intensity image (4D-PR-AVE), respectively, were compared against the accumulation of the Monte Carlo dose recalculated on every phase. Plan evaluation metrics relating to target volumes and critical structures relevant for lung SBRT were analyzed. Results Plan evaluation metrics tabulated using 4D-PR-EX, 4D-PR-MID, and 4D-PR-AVE differed from those tabulated using Monte Carlo recalculation on every phase by an average of 0.14±0.70 Gy, -0.11±0.51 Gy, and 0.00±0.62 Gy, respectively. Plan evaluation metrics calculated from 3D-EX and 3D-AVE were acceptably accurate for target volumes and most critical structures, however deviations of between 8 and 13 Gy were observed for the proximal bronchial trees of 3 patients. Conclusions The accuracy of 4D dose accumulated by projecting the dose calculated on the end-exhale, mid-ventilation, and average intensity images has been presented for 10 lung cancer SRBT plans. These methods involving projection without re-calculation may be sufficiently accurate compared to 4D dose accumulated from Monte Carlo recalculation on every phase, depending on institutional protocols. Projection of the dose calculated on the mid-ventilation scan was found to be statistically significantly more accurate than projection of the dose calculated on end-exhalation when considering target volume dose metrics. Use of 4D dose accumulation should be considered when evaluating normal tissue complication probabilities as well as in clinical situations where target volumes are directly inferior to mobile critical structures. This article is protected by copyright. All rights reserved.

Neurosurgery has undergone a technological revolution over the past several decades, from trephination to image-guided navigation. Advancements in virtual reality (VR) and augmented reality (AR) represent some of the newest modalities being integrated into neurosurgical practice and resident education. In this review, we present a historical perspective of the development of VR and AR technologies, analyze its current uses, and discuss its emerging applications in the field of neurosurgery.

Objective Stereotactic body radiotherapy (SBRT) is an effective treatment of spinal metastases in the vertebral body. However, variation has existed between practitioners regarding the appropriate target delineation. As such, we compared the tumor control, rates of compression fractures, and pain control for patients who had undergone SBRT for spinal metastases to either the lesion only (LO) or the full vertebral body (FVB). Methods A total of 126 spinal metastases in 84 patients had received single-fraction SBRT from January 2009 to February 2015. Of the 126 lesions, 36 (29%) were in the FVB group and 90 were in the LO group. The SBRT plans were reviewed to determine the treatment volume. Odds ratios were used to compare the rates of compression fracture and local failure. Regression analysis was performed to identify the predictors of outcome. Results A total of 5 failures had occurred in the FVB group and 14 in the LO group; however, the difference was not statistically significant (P = 0.5). No difference was found in pain reduction between the 2 groups (P = 0.9). Seven post-treatment compression fractures occurred in the LO group and four in the FVB group; however, the difference was not statistically significant (P = 0.6). The minimum dose to the planning target volume, patient age, and planning target volume size were the only significant factors predicting for local failure, vertebral body fracture, and pain control, respectively. Conclusions Given that we found no difference in tumor control, pain reduction, or fracture rate between patients treated to the FVB versus the. LO, it might be reasonable to consider SBRT to the LO for select patients.

Background Vestibular schwannomas (VS) are benign intracranial neoplasms arising from the eighth cranial nerve for which targeted radiation therapy (RT) has proved increasingly successful. However, long-term hearing and related cranial nerve outcomes have been disputed for the 3 current RT modalities. Objective To determine differences in hearing preservation for patients treated with stereotactic radiosurgery (SRS), fractionated stereotactic radiotherapy (FSRT), or hypofractionated stereotactic radiotherapy (hypoFSRT) for VS. Methods A retrospective electronic chart review was conducted for all patients with unilateral VS treated with primary RT at a single academic medical center between 2000 and 2017. The primary outcome measure was preservation of serviceable hearing status in the affected ear at last follow-up. Secondary outcomes included tinnitus, vertigo, and imbalance. Results A total of 33 FSRT cases, 21 SRS cases, and 6 hypoFSRT cases were identified. Postoperative deterioration in serviceable hearing and tinnitus showed significant differences across cohorts. The SRS cohort had a higher baseline incidence of nonserviceable hearing and disequilibrium compared with other cohorts before RT (P = 0.001 and 0.022, respectively); no differences in baseline morbidity were observed for vertigo and tinnitus. The 5-year tumor control rate was 95.2%, 93.9%, and 100% with SRS, FSRT, and hypoFSRT, respectively. Conclusions Our series indicated an excellent tumor control rate in all the modalities. Our SRS cohort showed increased incidence and shorter time to hearing deterioration compared with the FSRT and hypoFSRT cohorts. The FSRT and hypoFSRT cohorts have shown comparable overall outcomes. Onset of post-RT tinnitus was observed only with FSRT.

Breast cancer is the second most common cancer to metastasize in the brain. Little is known about how receptor subtype, including luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) enriched, and triple negative (TN) affect response to radiation and distant intracranial recurrence (ICR) following radiation therapy. We conducted a single-institution retrospective analysis of 38 breast cancer brain metastasis (BCBM) patients who underwent 93 treatment courses of stereotactic radiosurgery, stereotactic radiotherapy, post-operative radiation, or whole brain radiation therapy. Endpoints included overall survival (OS), treatment response (partial/complete response, PR/CR, or progression), ICR after treatment, and time from breast cancer diagnosis to the first BCBM (time to metastasis, TTM). Subset analyses were performed for triple receptor subtype as well as estrogen receptor (ER) positive versus negative, HER2+ versus HER2-, and age ≤ 50 versus >50 years old. Median OS for the population was 22.5 months, with median follow-up after treatment of 20.5 months. TTM was shortest for HER2 enriched, TN, ER−, and younger patients. TN, HER2-, and younger patients showed the poorest OS. ICR was also greatest in TN and HER2− patients. Radiation failure at the treated BCBM was seen most prominently in HER2+ and ER− patients. Receptor subtypes that demonstrated poorer OS tended to demonstrate higher intracranial recurrence. A positive response to radiation was not associated with better OS or lower ICR. Identifying patterns based on receptor subtype may guide clinicians in management and surveillance for BCBM.

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.

Objective To retrospectively compare ideal radiosurgical target volumes defined by a manual method (surgeon) to those determined by Adaptive Hybrid Surgery (AHS) operative planning software in 7 patients with vestibular schwannoma (VS). Methods Four attending surgeons (3 neurosurgeons and 1 ear, nose, and throat surgeon) manually contoured planned residual tumors volumes for 7 consecutive patients with VS. Next, the AHS software determined the ideal radiosurgical target volumes based on a specified radiotherapy plan. Our primary measure was the difference between the average planned residual tumor volumes and the ideal radiosurgical target volumes defined by AHS (dRVAHS-planned). Results We included 7 consecutive patients with VS in this study. The planned residual tumor volumes were smaller than the ideal radiosurgical target volumes defined by AHS (1.6 vs. 4.5 cm3, P = 0.004). On average, the actual post-operative residual tumor volumes were smaller than the ideal radiosurgical target volumes defined by AHS (2.2 cm3 vs. 4.5 cm3; P = 0.02). The average difference between the ideal radiosurgical target volume defined by AHS and the planned residual tumor volume (dRVAHS-planned) was 2.9 ± 1.7 cm3, and we observed a trend toward larger dRVAHS-planned in patients who lost serviceable facial nerve function compared with patients who maintained serviceable facial nerve function (4.7 cm3 vs. 1.9 cm3; P = 0.06). Conclusions Planned subtotal resection of VS diverges from the ideal radiosurgical target defined by AHS, but whether that influences clinical outcomes is unclear.

Purpose: Radiation therapy simulations solely based on MRI have advantages compared to CT-based approaches. One feature readily available from computed tomography (CT) that would need to be reproduced with MR is the ability to compute digitally reconstructed radiographs (DRRs) for comparison against on-board radiographs commonly used for patient positioning. In this study, the authors generate MR-based bone images using a single ultrashort echo time (UTE) pulse sequence and quantify their 3D and 2D image registration accuracy to CT and radiographic images for treatments in the cranium. Methods: Seven brain cancer patients were scanned at 1.5 T using a radial UTE sequence. The sequence acquired two images at two different echo times. The two images were processed using an in-house software to generate the UTE bone images. The resultant bone images were rigidly registered to simulation CT data and the registration error was determined using manually annotated landmarks as references. DRRs were created based on UTE-MRI and registered to simulated on-board images (OBIs) and actual clinical 2D oblique images from ExacTrac™. Results: UTE-MRI resulted in well visualized cranial, facial, and vertebral bones that quantitatively matched the bones in the CT images with geometric measurement errors of less than 1 mm. The registration error between DRRs generated from 3D UTE-MRI and the simulated 2D OBIs or the clinical oblique x-ray images was also less than 1 mm for all patients. Conclusions: UTE-MRI-based DRRs appear to be promising for daily patient setup of brain cancer radiotherapy with kV on-board imaging.

Purpose The purpose of this study was to investigate the dosimetric feasibility of liver stereotactic body radiation therapy (SBRT) using a teletherapy system equipped with 3 rotating 60 Co sources (tri- 60 Co system) and a built-in magnetic resonance imager (MRI). We hypothesized tumor size and location would be predictive of favorable dosimetry with tri- 60 Co SBRT. Methods and materials The primary study population consisted of 11 patients treated with SBRT for malignant hepatic lesions whose linear accelerator (LINAC)–based SBRT plans met all mandatory Radiation Therapy Oncology Group (RTOG) 1112 organ-at-risk (OAR) constraints. The secondary study population included 5 additional patients whose plans did not meet the mandatory constraints. Patients received 36 to 60 Gy in 3 to 5 fractions. Tri- 60 Co system SBRT plans were planned with ViewRay system software. Results All patients in the primary study population had tri- 60 Co SBRT plans that passed all RTOG constraints, with similar planning target volume coverage and OAR doses to LINAC plans. Mean liver doses and V 10Gy to the liver, although easily meeting RTOG 1112 guidelines, were significantly higher with tri- 60 Co plans. When the 5 additional patients were included in a univariate analysis, the tri- 60 Co SBRT plans were still equally able to pass RTOG constraints, although they did have inferior ability to pass more stringent liver and kidney constraints ( P 60 Co SBRT plan to meet these constraints depended on lesion location and size. Patients with smaller or more peripheral lesions (as defined by distance from the aorta, chest wall, liver dome, and relative lesion volume) were significantly more likely to have tri- 60 Co plans that spared the liver and kidney as well as LINAC plans did ( P Conclusions It is dosimetrically feasible to perform liver SBRT with a tri- 60 Co system with a built-in MRI. Patients with smaller or more peripheral lesions are more likely to have optimal liver and kidney sparing, with the added benefit of MRI guidance, when receiving tri- 60 Co–based SBRT.

The current standard treatment for glioblastoma multiforme (GBM) is surgery followed by chemotherapy and external radiation. Even with the standard treatment, the 2 year survival rate for GBM is less than 20%, making research for alternative treatments necessary. Transferrin receptor 1 (TfR1) controls the rate of cellular iron uptake by tuning the amount of iron delivered to the cells to meet metabolic needs. Kawabata et al. (J Biol Chem 1999;274:20826–32) cloned a second TfR molecule known as transferrin receptor 2 (TfR2) in 1999. Multiple experimental studies have documented increased expression of TfR1 on both proliferating cells and cells that have undergone malignant transformation. Calzolari et al. concluded that TfR2 is frequently expressed in human cell lines in 2007 (Blood Cells Mol Dis 2007;39:82–91) and in GBM in particular in 2010 (Transl Oncol 2010;3:123–34). In GBM, a highly significant correlation (p < 0.0001) was found between the expression level of TfR2 and overall survival, showing that higher levels of TfR2 expression were associated with an overall longer survival. The data on which of the two transferrin receptors is the better target is also unclear and should be studied. The transferrin pathway may be a promising target, but more research should be completed on the antigenicity to discern the viability of it as an immunotherapy target.

Stereotactic body radiation therapy (SBRT) and heat-based ablation (HBA) are both potentially safe and effective treatments for primary and metastatic lung tumors. Both are suboptimal for centrally located tumors, with SBRT having a higher risk of significant toxicity and HBA having lower efficacy. This study evaluates the safety and efficacy of combination SBRT-HBA to determine whether combined treatment can result in superior outcomes to each treatment alone.Patients with 1 or 2 primary or metastatic lung tumors ≤ 5 cm in size were enrolled in a prospective phase 2 trial and treated with SBRT in 3 fractions followed by HBA. Tumors1 cm from the central bronchial tree received a total of 36 Gy, and tumors 1 to 2 cm away received 42 Gy. HBA was delivered within 10 days after SBRT. The primary endpoints were local control, toxicity, and degree of decline in lung function. The secondary endpoints were progression-free survival and overall survival.We treated 16 patients with 17 tumors. The median follow-up time was 26 months. Fifteen tumors were evaluable for local control. The 1- and 2-year actuarial local control rates were 93% and 81%, respectively. Three patients had grade ≥ 3 toxicity: bronchial stenosis, pain, and pulmonary hemorrhage. The percent predicted forced expiratory volume in 1 second and functional vital capacity decreased by 8% and 8.5%, respectively, at 3 months after treatment (P .001 for both).Combining SBRT and HBA for centrally located lung tumors offers reasonable local control and toxicity despite the anatomic challenges of this location. HBA may be a reasonable supplement to SBRT when trachea and bronchus, large vessel, or esophageal constraints cannot be met with full-dose SBRT and a biologically effective dose100 Gy is delivered because of an ultra-central location or large tumor size.

Purpose To compare lung tumor motion measured with a model-based technique to commercial 4-dimensional computed tomography (4DCT) scans and describe a workflow for using model-based 4DCT as a clinical simulation protocol. Methods and materials Twenty patients were imaged using a model-based technique and commercial 4DCT. Tumor motion was measured on each commercial 4DCT dataset and was calculated on model-based datasets for 3 breathing amplitude percentile intervals: 5th to 85th, 5th to 95th, and 0th to 100th. Internal target volumes (ITVs) were defined on the 4DCT and 5th to 85th interval datasets and compared using Dice similarity. Images were evaluated for noise and rated by 2 radiation oncologists for artifacts. Results Mean differences in tumor motion magnitude between commercial and model-based images were 0.47 ± 3.0, 1.63 ± 3.17, and 5.16 ± 4.90 mm for the 5th to 85th, 5th to 95th, and 0th to 100th amplitude intervals, respectively. Dice coefficients between ITVs defined on commercial and 5th to 85th model-based images had a mean value of 0.77 ± 0.09. Single standard deviation image noise was 11.6 ± 9.6 HU in the liver and 6.8 ± 4.7 HU in the aorta for the model-based images compared with 57.7 ± 30 and 33.7 ± 15.4 for commercial 4DCT. Mean model error within the ITV regions was 1.71 ± 0.81 mm. Model-based images exhibited reduced presence of artifacts at the tumor compared with commercial images. Conclusion Tumor motion measured with the model-based technique using the 5th to 85th percentile breathing amplitude interval corresponded more closely to commercial 4DCT than the 5th to 95th or 0th to 100th intervals, which showed greater motion on average. The model-based technique tended to display increased tumor motion when breathing amplitude intervals wider than 5th to 85th were used because of the influence of unusually deep inhalations. These results suggest that care must be taken in selecting the appropriate interval during image generation when using model-based 4DCT methods.

Central neurocytoma (CN) typically presents as an intraventricular mass causing obstructive hydrocephalus. The first line of treatment is surgical resection with adjuvant conventional radiotherapy. Stereotactic radiosurgery (SRS) was proposed as an alternative therapy for CN because of its lower risk profile. The objective of this systematic analysis is to assess the efficacy of SRS for CN. A systematic analysis for CN treated with SRS was conducted in PubMed. Baseline patient characteristics and outcomes data were extracted. Heterogeneity and publication bias were also assessed. Univariate and multivariate linear regressions were used to test for correlations to the primary outcome: local control (LC). The estimated cumulative rate of LC was 92.2% (95% confidence interval: 86.5-95.7%, p

Essential tremor and Parkinson's disease–associated tremor are extremely prevalent within the field of movement disorders. The ventral intermediate (VIM) nucleus of the thalamus has been commonly used as both a neuromodulatory and neuroablative target for the treatment of these forms of tremor. With both deep brain stimulation and Gamma Knife radiosurgery, there is an abundance of literature regarding the surgical planning, targeting, and outcomes of these methodologies. To date, there have been no reports of frameless, linear accelerator (LINAC)–based thalomotomies for tremor.The authors report the case of a patient with tremor-dominant Parkinson's disease, with poor tremor improvement with medication, who was offered LINAC-based thalamotomy. High-resolution 0.9-mm isotropic MR images were obtained, and simulation was performed via CT with 1.5-mm contiguous slices. The VIM thalamic nucleus was determined using diffusion tensor imaging (DTI)–based segmentation on FSL using probabilistic tractography. The supplemental motor and premotor areas were the cortical target masks. The authors centered their isocenter within the region of the DTI-determined target and treated the patient with 140 Gy in a single fraction. The DTI-determined target had coordinates of 14.2 mm lateral and 8.36 mm anterior to the posterior commissure (PC), and 3 mm superior to the anterior commissure (AC)–PC line, which differed by 3.30 mm from the original target determined by anatomical considerations (15.5 mm lateral and 7 mm anterior to the PC, and 0 mm superior to the AC-PC line). There was faint radiographic evidence of lesioning at the 3-month follow-up within the target zone, which continued to consolidate on subsequent scans. The patient experienced continued right upper-extremity resting tremor improvement starting at 10 months until it was completely resolved at 22 months of follow-up.Frameless LINAC-based thalamotomy guided by DTI-based thalamic segmentation is a feasible method for achieving radiosurgical lesions of the VIM thalamus to treat tremor.

Radiographic changes occur in over half of patients treated with stereotactic body radiotherapy (SBRT) to the lung, correlating histopathologically with injury. We quantified radiographic density changes (ie, fibrosis) at 3, 6, and 12 months and investigated the relationship between these volumes and clinical and dosimetric parameters. The study population consisted of patients treated with SBRT to the lung for stage I primary lung cancers (n = 39) or oligometastatic lesions (n = 17). Fractionation schemes included 3 fractions of 12, 14, or 18 gray (Gy) and 4 fractions of 12 or 12.5 Gy prescribed to cover 95% of the planning target volume (PTV). Planning computed tomography (CT) scans were rigidly registered to follow-up CT scans obtained at intervals of 3, 6, and 12 months. Fibrotic volumes were contoured on the follow-up scans. Associations between the volume of fibrosis and clinical and dosimetric parameters were investigated using univariate linear regression. Scans were available for 65 and 47 lesions at 6 and 12 months, respectively. Age, years since quitting smoking, and GOLD Global Initiative for Chronic Obstructive Lung Disease score were significantly associated with increasing volume of fibrosis (P < .05). Total dose, dose per fraction, PTV, and volumetric parameters (V0-V55) were also significantly associated with increasing volumes of fibrosis (P < .01). For dosimetric parameters, the effect was largest for V55. Age, significant smoking history, and GOLD score were significantly associated with increasing volumes of fibrosis following SBRT. In a multivariate model adjusted for age and smoking history, V10 through V50 and PTV size remained significant predictors of fibrotic volume. Further, there is a strong dose-response relationship between the volume of lung exposed to a certain dose and the fibrotic volume. The predominant kinetic patterns of fibrosis demonstrate peaking fibrotic volumes at 6 and 12 months. These results provide insight for expectations of fibrosis after SBRT.

BACKGROUND: The current treatment of brain metastases from the lung involves surgical resection of symptomatic lesions followed by adjuvant radiation therapy (ART) with no evidence-based guideline describing the ideal time from surgery to ART in this patient population. Our objective was to evaluate optimal post-operative timing of adjuvant RT with respect to survival outcomes. METHODS: We retrospectively identified 28 patients with pathologically confirmed primary non-small cell lung cancer and intracranial metastases who underwent a single craniotomy for resection with adjuvant RT between 2001 and 2016. Patient demographics, treatment details, and clinical outcomes were noted. RESULTS: Median surgery-to-radiation interval (SRI) was 31 days. We categorized patients into expedited RT (defined as SRI < 6 weeks, n=20) or delayed RT (SRI (3) 6 weeks, n=8). Patients receiving Delayed RT did not differ from patients receiving Expedited RT in demographics, pre-operative metastatic burden, post-operative functional status, or adjuvant RT modality. Fifteen patients (54%) were living at last follow-up (median follow-up 8.2 months, mean 20.3 months). Across all patients, expected overall survival (OS) was 21.4 post-operative months and progression-free survival (PFS) was 13.2 months. OS was significantly shorter after Delayed RT compared to Expedited RT (7.0 vs. 28.3 months, P = 0.011). PFS was 15.0 months with Expedited RT and 3.2 months with Delayed RT (P = 0.39). CONCLUSION: Our results suggest that delayed adjuvant RT with SRI (3) 6 weeks is associated with a shorter expected survival of up to 21 post-operative months. However, our study is limited by its retrospective nature, limited sample size, and limited follow-up. Refined studies are needed to more conclusively delineate optimal timing of adjuvant RT after surgical resection of intracranial lung cancer metastases, ideally involving well-powered randomized trials.

Objective : To investigate if delay of adjuvant radiotherapy (ART) beyond 6 post-operative weeks affects survival outcomes in patients undergoing craniotomy or craniectomy for resection of non-small cell lung cancer (NSCLC) intracranial metastases. Patients and methods We performed a retrospective analysis of 28 patients undergoing resection of intracranial metastases and ART at our institution from 2001 to 2016. We assessed survival outcomes for patients who received delayed versus non-delayed ART, as well as associated risk factors. Results Among 28 patients, 8 (29%) had delayed ART beyond 6 post-operative weeks. Fifteen received stereotactic radiotherapy (SRT), 8 (29%) received whole brain radiotherapy (WBRT), and 5 (18%) received combination WBRT + SRT. There were no significant differences in ART modality or dosing, age, sex, number of intracranial metastases, primary metastasis volume, rates of chemotherapy, extracranial metastases, or post-operative functional scores between groups. Expected post-operative survival was shorter with delayed ART (7 months versus 28 months, P = 0.01). The most common reason for delayed ART was complicated post-operative course (n = 3.38%). Significant risk factors for delayed ART included non-routine discharge (P = 0.01) and additional invasive procedures between surgery and ART start date (P = 0.02). Conclusions Our results suggest delayed ART in patients undergoing surgical resection of intracranial NSCLC metastases is associated with shorter overall survival. However, risk factors for delayed ART, including non-routine discharge and the need for additional invasive procedures, may have in themselves reflected poorer clinical courses that may have also contributed to the observed survival differences.

Objective To evaluate the efficacy of postoperative fractionated stereotactic radiosurgery (FSRS) and hypofractionated stereotactic radiotherapy (SRT) to large surgical cavities after gross total resection of brain metastases. Methods A retrospective analysis of 41 patients who had received tumor-bed FSRS (5 fractions) or SRT (10 fractions) after resection of brain metastasis between 2005 and 2015 was performed. All resection cavities were treated with a frameless linear accelerator-based system. Patients who underwent subtotal resection, single-dose SRS to the resection cavity, or were treated with a fractionation schedule other than 5 or 10 fractions, were excluded. Results Twenty-six patients were treated with 5 fractions and 15 patients with 10 fractions. The median planning target volume was 19.78 cm 3 (12.3–28 cm 3 ) to the 5-fraction group and 29.79 cm 3 (26.3–47.6 cm 3 ) to the 10-fraction group ( P = 0.020). The 1-year and 2-year local control rates for all patients were 89.4% and 77.1%, respectively, and 89.6% and 78.6% were free from distant intracranial progression, respectively. No difference was observed in local control or freedom from distant intracranial progression between the 5-fraction or 10-fraction groups. The median overall survival was 28.27 months (95% confidence interval, 19.42–37.12) for all patients. No patient developed necrosis at the resection cavity. Conclusions Fractionation offers the potential to exploit the different biological responses between neoplastic and normal tissues to ionizing radiation. The use of 5 daily doses of 5–6 Gy or 10 daily doses of 3 Gy is a good strategy to have a reasonable local control and avoid neurotoxicity.

Background The mechanisms by which surgery and radiation elicit pain relief in trigeminal neuralgia (TN) secondary to mass lesions vary widely. We aimed to evaluate the outcomes of radiation to the nerve rather than to the lesion in the treatment of secondary TN. Methods We retrospectively reviewed all patients who underwent radiation at the University of California, Los Angeles for TN secondary to tumors. The Barrow Neurological Institute (BNI) pain score was used to evaluate pain outcomes. Results Twelve patients were identified; 4 were male and 8 were female. Their mean age at treatment was 59.8 years (range, 47.7–84.7 years). Tumor pathologies included meningioma (n = 8), squamous cell carcinoma (n = 2), vestibular schwannoma (n = 1), and hemangiopericytoma (n = 1). No patient suffered from multiple sclerosis. Ten patients underwent initial radiation targeting their tumors—radiosurgery in 3 and fractionated radiation therapy in 7 others. Only 6 among these 10 experienced at least partial relief, which lasted a mean 6 months. Radiosurgery targeting the trigeminal nerve was eventually performed. Overall, 10 of 12 (83.3%) patients experienced good initial pain relief, complete in 6 (50%) patients. Pain recurred in 6 (60%) patients, at a mean 41 months after radiosurgery to the trigeminal nerve. Three patients experienced facial sensory dysfunction postprocedurally at a mean follow-up duration of 57 months. Conclusion In contrast to tumor radiation, radiosurgery to the trigeminal nerve root resulted in reasonable and longer pain reduction, on par with the literature regarding surgical resection, with low risk of additional complications.

ObjectiveWe evaluated whether patients with early-stage non-small-cell lung cancers (NSCLCs) treated with stereotactic body radiation therapy (SBRT) without full prescription dose coverage of the planning target volume (PTV) had inferior outcomes.MethodsThe SBRT regimen was 54 Gy in three fractions. Dosimetric constraints were as per the Radiation Therapy Oncology Group 0236 guidelines. All patients underwent four-dimensional CT (4D-CT) simulation. The internal target volume (ITV) was defined using 4D-CT, and the PTV was defined as a 6-mm longitudinal and a 3-mm axial expansion from the ITV. If normal tissue constraints were beyond tolerance, ITV-based dosing was employed where priority was made for full ITV coverage at the expense of PTV coverage. Patients with and without full PTV dose coverage were compared, and control rates were estimated using Kaplan-Meier analysis.Results120 NSCLC cases were evaluated with 81% having adequate PTV dose coverage. ITV and PTV were significantly larger in the cohort with inadequate PTV dose coverage (p = 0.0085 and p = 0.0038, respectively), and the mean ITV and PTV doses were higher in patients with adequate PTV dose coverage (p = 0.002 and p

PURPOSE: Radiation therapy simulations solely based on MRI have advantages compared to CT‐based approaches. One feature readily available from computed tomography (CT) that would need to be reproduced with MR is the ability to compute digitally reconstructed radiographs (DRRs) for comparison against on‐board radiographs commonly used for patient positioning. In this study, the authors generate MR‐based bone images using a single ultrashort echo time (UTE) pulse sequence and quantify their 3D and 2D image registration accuracy to CT and radiographic images for treatments in the cranium. METHODS: Seven brain cancer patients were scanned at 1.5 T using a radial UTE sequence. The sequence acquired two images at two different echo times. The two images were processed using an in‐house software to generate the UTE bone images. The resultant bone images were rigidly registered to simulation CT data and the registration error was determined using manually annotated landmarks as references. DRRs were created based on UTE‐MRI and registered to simulated on‐board images (OBIs) and actual clinical 2D oblique images from ExacTrac™. RESULTS: UTE‐MRI resulted in well visualized cranial, facial, and vertebral bones that quantitatively matched the bones in the CT images with geometric measurement errors of less than 1 mm. The registration error between DRRs generated from 3D UTE‐MRI and the simulated 2D OBIs or the clinical oblique x‐ray images was also less than 1 mm for all patients. CONCLUSIONS: UTE‐MRI‐based DRRs appear to be promising for daily patient setup of brain cancer radiotherapy with kV on‐board imaging.

The ExacTrac X-Ray 6D image-guided radiotherapy (IGRT) system will be described and its performance evaluated. The system is mainly an integration of 2 subsystems: (1) an infrared (IR)-based optical positioning system (ExacTrac) and (2) a radiographic kV x-ray imaging system (X-Ray 6D). The infrared system consists of 2 IR cameras, which are used to monitor reflective body markers placed on the patient's skin to assist in patient initial setup, and an IR reflective reference star, which is attached to the treatment couch and can assist in couch movement with spatial resolution to better than 0.3 mm. The radiographic kV devices consist of 2 oblique x-ray imagers to obtain high-quality radiographs for patient position verification and adjustment. The position verification is made by fusing the radiographs with the simulation CT images using either 3 degree-of-freedom (3D) or 6 degree-of-freedom (6D) fusion algorithms. The position adjustment is performed using the infrared system according to the verification results. The reliability of the fusion algorithm will be described based on phantom and patient studies. The results indicated that the 6D fusion method is better compared to the 3D method if there are rotational deviations between the simulation and setup positions. Recently, the system has been augmented with the capabilities for image-guided positioning of targets in motion due to respiration and for gated treatment of those targets. The infrared markers provide a respiratory signal for tracking and gating of the treatment beam, with the x-ray system providing periodic confirmation of patient position relative to the gating window throughout the duration of the gated delivery.

BACKGROUND: Radiation therapy has emerged as an effective alternative treatment modality for vestibular schwannomas (VS) to achieve tumor control and hearing preservation. The purpose of this study is to evaluate the radiation delivered to the cochlea during stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) and to determine its effect on hearing preservation. METHODS: Patients receiving SRS or SRT treatment for VS at UCLA from 2009 to 2013 were analyzed for clinical and hearing outcomes. The dosimetric data to the cochlea volume was associated with the hearing outcome of patients. Patients treated with SRS received a marginal dose of 12 Gy, and patients treated with SRT received a marginal dose of 50.4 Gy delivered through 28 fractions. Statistical analysis was completed using 2-tailed, Mann-Whitney U test with a significance level of 0.05. RESULTS 40 patients underwent either SRS or SRT for vestibular schwannoma with a mean follow-up of 23.2 months. The mean total radiation dose delivered to the cochlea volume ranged from 4.0 to 11.9 Gy (median: 8.7 Gy) for SRS treatment and 30.2 to 51.4 Gy (median: 44.8 Gy) for SRT treatment. Hearing was preserved in 60% of SRS patients and in 63% of SRT patients. The cochlea received statistically significantly more radiation in patients with decreased hearing in SRS (p = 0.031), but not in SRT (p = 0.097). CONCLUSIONS: Our data suggests that increased cochlear radiation dose is significantly associated with decreased rates of hearing preservation following SRS treatment but not with SRT treatment. Irradiation of cochlear structures may be a critically important aspect of radiosurgery treatment that warrants careful evaluation in the radiation treatment of vestibular schwannomas. Future prospective studies with randomization may further validate this data.

Recently, a commercial system capable of x-ray image guided patient positioning and respiratory gated delivery has become available. Here we describe the operational principles of this system and investigate its geometric targeting accuracy under controlled conditions. The system tracks breathing via infrared (IR) detection of reflective markers located on the patient's abdomen. Localization kilovoltage (kV) x-rays are triggered from within the gated delivery window portion of the breathing trace and after positioning, the tumour will cross the linac isocentre during gated delivery. We tested geometric accuracy of this system by localizing and delivering gated fields to a moving phantom. Effects of phantom speed, gating window location, timing errors and phantom rotations on positioning and gating accuracy were investigated. The system delivered gated fields to both a moving and static phantom with equal accuracy. The position of the gating window affects accuracy only to the extent that an asymmetric breathing motion could affect dose distribution within its boundaries. Positioning errors were found to be less then 0.5 +/- 0.2 mm for phantom rotations up to 5 degrees. We found and corrected a synchronization error caused by a faulty x-ray duration setting and detected a 60 +/- 20 ms time delay in our linear accelerator.

Central neurocytomas (CNs) are rare central nervous system tumors that occur in the lateral ventricles. They are prevalent in young adults and are typically benign with excellent prognosis following surgical resection. Because of the rarity of the disease and its similar features with more common tumors, misdiagnosis becomes an issue. Optimal treatment is achieved only when the correct tumor types are distinguished. Typical clinical manifestations include symptoms of increased intracranial pressure, although no clinical feature is pathognomonic to CN. Radiologic imaging, histology, magnetic resonance spectroscopy, and immunohistochemistry must be used to elucidate tumor characteristics and properly diagnose CN.

Benign osteoblastoma is a rare, vascular, osteoid-forming bone tumor that occurs even less frequently in the cranial bones. Benign osteoblastoma of the cranium affects women slightly more often than men and typically presents in the first three decades of life. Although clinical presentation can vary depending on location, cranial osteoblastoma usually presents as a painful, non-mobile, subcutaneous mass or swelling. On CT scan, it generally presents as a well-demarcated, mixed lytic and sclerotic lesion, with enlarged diploe, thinning outer and/or inner tables, and varying degrees of calcification. It is hypo to isointense on T1-weighted MRI and has variable presentation on T2-weighted MRI. Gross total resection is the definitive treatment, while subtotal resection is utilized when it is necessary to preserve critical adjacent neurovascular structures.

Purpose To evaluate the potential benefit of 4π radiation therapy in recurrent, locally advanced, or metastatic head-and-neck cancer treated with stereotactic body radiation therapy (SBRT). Methods and Materials Twenty-seven patients with 29 tumors who were treated using SBRT were included. In recurrent disease (n=26), SBRT was delivered with a median 44 Gy (range, 35-44 Gy) in 5 fractions. Three patients with sinonasal mucosal melanoma, metastatic breast cancer, and primary undifferentiated carcinoma received 35 Gy, 22.5 Gy, and 40 Gy in 5 fractions, respectively. Novel 4π treatment plans were created for each patient to meet the objective that 95% of the planning target volume was covered by 100% of the prescription dose. Doses to organs at risk (OARs) and 50% dose spillage volumes were compared against the delivered clinical SBRT plans. Local control (LC), late toxicity, tumor control probability (TCP), and normal tissue complication probability were determined. Results Using 4π plans, mean/maximum doses to all OARs were reduced by 22% to 89%/10% to 86%. With 4π plans, the 50% dose spillage volume was decreased by 33%. Planning target volume prescription dose escalation by 10 Gy and 20 Gy were achieved while keeping doses to OARs significantly improved or unchanged from clinical plans, except for the carotid artery maximum dose at 20-Gy escalation. At a median follow-up of 10 months (range, 1-41 months), crude LC was 52%. The 2-year LC of 39.2% approximated the predicted mean TCP of 42.2%, which increased to 45.9% with 4π plans. For 10-Gy and 20-Gy dose escalation, 4π plans increased TCP from 80.1% and 88.1% to 85.5% and 91.4%, respectively. The 7.4% rate of grade ≥3 late toxicity was comparable to the predicted 5.6% mean normal tissue complication probability for OARs, which was significantly reduced by 4π planning at the prescribed and escalated doses. Conclusions 4π plans may allow dose escalation with significant and consistent improvements in critical organ sparing, tumor control, and coverage.

Purpose/objective(s): To evaluate the dosimetric feasibility of a hypofractionated radiotherapy schedule for Stage III non-small cell lung cancers (NSCLC). Materials/Methods: The study sample included 14 cases. The mean tumor burden (primary and nodal areas) was 111 cm 3 , range 10-424 cm 3 . Intended plans consist of an initial dose of 40 Gy in 10 fractions, followed by a 7 Gy x 5 boost. The clinical target volumes (CTV) consisted of PET avid areas only; the initial dose was delivered to the CTV+5 mm margin, and the boost to the CTV (no margin). At an alpha/beta ratio of 10, the tumor dose equivalent at 2 Gy per fraction of the proposed regimen is 94 Gy.