Purpose: An integrated magnetic resonance scanner and linear accelerator (MR-linac) was implemented with daily online adaptive radiation therapy (ART). This study evaluated patient-reported experiences with their overall hospital care as well as treatment in the MR-linac environment. Methods: Patients pre-screened for MR eligibility and claustrophobia were referred to simulation on a 1.5 T MRlinac. Patient-reported experience measures were captured using two validated surveys. The 15-item MR-anxiety questionnaire (MR-AQ) was administered immediately after the first treatment to rate MR-related anxiety and relaxation. The 40-item satisfaction with cancer care questionnaire rating doctors, radiation therapists, the services and care organization and their outpatient experience was administered immediately after the last treatment using five-point Likert responses. Results were analyzed using descriptive statistics. Results: 205 patients were included in this analysis. Multiple sites were treated across the pelvis and abdomen with a median treatment time per fraction of 46 and 66 min respectively. Patients rated MR-related anxiety as "not at all" (87%), "somewhat" (11%), "moderately" (1%) and "very much so" (1%). Positive satisfaction responses ranged from 78 to 100% (median 93%) across all items. All radiation therapist-specific items were rated positively as 96-100%. The five lowest rated items (range 78-85%) were related to general provision of information, coordination, and communication. Overall hospital care was rated positively at 99%. Conclusion: In this large, single-institution prospective cohort, all patients had low MR-related anxiety and completed treatment as planned despite lengthy ART treatments with the MR-linac. Patients overall were highly satisfied with their cancer care involving ART using an MR-linac.

PURPOSE:The capacity for machine learning (ML) to facilitate radiation therapy (RT) planning for primary brain tumors has not been described. We evaluated ML-assisted RT planning with regard to clinical acceptability, dosimetric outcomes, and planning efficiency for adults and children with primary brain tumors. METHODS AND MATERIALS:In this prospective study, children and adults receiving 54 Gy fractionated RT for a primary brain tumor were enrolled. For each patient, one ML-assisted RT plan was created and compared with 1 or 2 plans created using standard ("manual") planning procedures. Plans were evaluated by the treating oncologist, who was blinded to the method of plan creation. The primary endpoint was the proportion of ML plans that were clinically acceptable for treatment. Secondary endpoints included the frequency with which ML plans were selected as preferable for treatment, and dosimetric differences between ML and manual plans. RESULTS:A total of 116 manual plans and 61 ML plans were evaluated across 61 patients. Ninety-four percent of ML plans and 93% of manual plans were judged to be clinically acceptable (P = 1.0). Overall, the quality of ML plans was similar to manual plans. ML plans comprised 34.5% of all plans evaluated and were selected for treatment in 36.1% of cases (P = .82). Similar tumor target coverage was achieved between both planning methods. Normal brain (brain minus planning target volume) received an average of 1 Gy less mean dose with ML plans (compared with manual plans, P < .001). ML plans required an average of 45.8 minutes less time to create, compared with manual plans (P < .001). CONCLUSIONS:ML-assisted automated planning creates high-quality plans for patients with brain tumors, including children. Plans created with ML assistance delivered slightly less dose to normal brain tissues and can be designed in less time.

In a universal health care system, SES (residential instability and material deprivation) were associated with the increased risk of ED within 90 days of RT. Proactive care and virtual monitoring during the 90-day period after RT in high-risk patients may reduce ED visits. ED visits beyond our tertiary institution are being gathered to address this study limitation.

For multicenter clinical studies, characterizing the robustness of image-derived radiomics features is essential. Features calculated on PET images have been shown to be very sensitive to image noise. The purpose of this work was to investigate the efficacy of a relatively simple harmonization strategy on feature robustness and agreement. A purpose-built texture pattern phantom was scanned on 10 different PET scanners in 7 institutions with various different image acquisition and reconstruction protocols. An image harmonization technique based on equalizing a contrast-to-noise ratio was employed to generate a "harmonized" alongside a "standard" dataset for a reproducibility study. In addition, a repeatability study was performed with images from a single PET scanner of variable image noise, varying the binning time of the reconstruction. Feature agreement was measured using the intraclass correlation coefficient (ICC). In the repeatability study, 81/93 features had a lower ICC on the images with the highest image noise as compared to the images with the lowest image noise. Using the harmonized dataset significantly improved the feature agreement for five of the six investigated feature classes over the standard dataset. For three feature classes, high feature agreement corresponded with higher sensitivity to the different patterns, suggesting a way to select suitable features for predictive models.

Purpose: To report final results of a clinical trial of APBI using intensity modulated radiotherapy (IMRT) to deliver 27 Gy in 5 daily fractions following breast conserving surgery (BCS) prospectively designed to assess the efficacy and cosmetic outcomes of a oneweek, APBI regimen among women with early breast cancer. Materials and Methods:Women ≥ 50 years, with lymph nodenegative, ER positive, HER-2 negative breast cancer or ductal carcinoma in situ (DCIS), ≤ 3cm diameter, following BCS with margins ≥ 2mm, and excellent or good baseline cosmesis received 27 Gy in 5 daily fractions to the seroma plus 1 cm CTV and 0.7 cm PTV margins.Clinical photographs, patient and provider cosmetic scores, breast fibrosis, telangiectasia and pain were collected prospectively, prior to RT and at 6 weeks, 1 and 2 years after RT.The primary endpoint was the proportion of women who retained Excellent or Good cosmesis at 2 years using the EORTC Cosmetic Rating System.Cosmetic failure was deterioration from Excellent or Good to Fair or Poor.A panel of 5 radiation oncologists independently assessed the cosmetic photographs.Secondary endpoints were rates and grades of breast fibrosis, telangiectasia, breast pain, ipsilateral breast tumour recurrence (IBRT), overall (OS), breast cancer-specific survival (BCSS) and subsequent mastectomy.Efficacy outcomes were assessed at clinic visits and by review of charts.ClinicalTrials.govregistration: NCT02681107.

Purpose: During the COVID-19 pandemic, many radiation oncology departments worldwide adopted the use of shorter and more intense hypofractionated regimens. Hospital foot traffic was reduced through virtual care. This study's primary objective was to assess the collective environmental effect of these strategic changes by identifying sources of carbon dioxide equivalents (CO2e). The rate of radiation-related adverse events from the increased use of hypofractionated treatments was assessed.Methods and Materials: All patients treated with external beam radiation therapy from April 1, 2019, to March 31, 2021, at our single institution were identified (n = 10,175) along with their radiation therapy visits (176,423 fractions) and unplanned visits to the radiation nursing clinic or emergency department. Out-patient hospital and virtual visits (n = 75,853) during this same period were also analyzed. Environmental effect measures, including linear accelerator power usage, patient travel distances, and personal protection equipment consumption were all converted into CO2e. Results: The use of curative hypofractionated regimens increased from 17% to 27% during the pandemic year. Carbon footprint was reduced by 39% during the pandemic year (1,332,388 kg CO2e) compared with the prepandemic year (2,024,823 kg CO2e). Comparing patients in the prepandemic versus pandemic year, there was a significant reduction in the proportion of hypofractionated patients who needed a visit to either the radiation nursing clinic (39% vs 25%; P < .001) or emergency departConclusions: This is the first study to demonstrate the environmental benefits of increased use of hypofractionated regimens and virtual care, while assuring that there was no added acute radiation-related adverse event. Our findings support their continued use as one of many long-term strategies to reduce the environmental footprint of health care delivery.& COPY; 2022 Elsevier Inc. All rights reserved.

3021 Objectives: In late 2019 the American Association of Physicists in Medicine (AAPM) Task Group 126 published a report, Acceptance Testing and Quality Assurance. The goal was provide a standardized set of acceptance and periodic tests that can be easily implemented in a QA program rather than following the full National Electrical Manufacturers Association (NEMA) NU 2 acceptance standards which can be challenging requiring specialized phantoms. The purpose of this study was assess the practical implications for nuclear medicine technologists (NMT) performing annual quality control (QC) tests. Methods: The five QC tests are: Spatial Resolution & PET/CT Registration (RR), Sensitivity (S), Count Rate Performance (CRP), Image Contrast & Scatter/Attenuation Correction (CSAC), and Image Uniformity (U). RR was tested by scanning capillary tubes filled with both F-18 and CT contrast determine PET resolution and PET/CT registration accuracy according the recent NEMA-2018 standards. Three tests (S, CRP, and U) were all performed by scanning a standard water phantom. The S test was performed using AAPM option 2, only monitor the vendor-specific calibration factor, a simpler alternative option 1 which requires a NEMA phantom. For the CRP test, a baseline was obtained by scanning the water once each hour for 11 hours. Then three 15 minute follow-up scans were acquired as per AAPM guidelines. The U test was also performed by scanning the water as per protocol to approximate a standard patient dose. Lastly, CSAC was tested by scanning the American College of Radiology (ACR) PET according the protocol. Each test was assessed for ease-of-performance and ease-of-data analysis as well as the times required for both performance and analysis. Both ease-of-performance and data analysis were classified as either routine, moderate, or complex according specific criteria. The classification of routine for ease-of-performance was whether the NMT had previous experience scanning the specific phantom. A classification of routine for data analysis meant the analysis was totally automated. For both performance and data analyses, a moderate classification was given if the test was new the NMT and/or manually performed. A complex classification was assigned if the performance and analysis were both new, involved tedious steps, and/or required assistance from a physicist. Each test was performed twice and the results were averaged. Results: Three of five tests were classified as routine for ease-of-performance (see table). The CSAC test (using the ACR phantom) was moderate. Although the RR test was complex, it was performed by a NMT using the manufacturer’s NEMA acquisition protocol. Ease-of-data analyses for two tests (ACR and U) were classified as routine since the SNMMI’s fully automated phantom analysis toolkit was used. Both the S and CRP data analyses were classified as moderate, as the NMT had manually create spreadsheets calculate results. As expected, the RR analysis was complex with PET resolution determined by a NMT using the manufacturer’s software; however, PET/CT registration analysis required the assistance of a physicist using a different imaging display system. The summed total times for both performance and data analyses by a NMT took longer than the estimated times of AAPM by factors of 1.89, 1.09, 1.25, 1.33, and 2.92, for the RR, S, CRP, CSAC and U tests, respectively. Conclusions: Although all times took longer than AAPM estimates, they could decrease with more experience. All tests were performed by a NMT except for the PET/CT registration analysis. Nonetheless, if software was available for this registration analysis, then NMTs could perform it. In summary, it is feasible that all five QC scans and four of the five data analyses methods recommended by the AAPM can commonly be performed by a nuclear medicine technologist.

PURPOSE:In this article we report on the results of a survey of physics plan review practices conducted by the Cancer Care Ontario Communities of Practice and the variations in practice between and within centers.METHODS:The medical physicists at each center worked together to complete the survey and submit a single response for that center. A 4-point Likert scale, used to report the variation in practice at each center, was quantified into two parameters: "Intra-center variation", the distribution of responses within the center, and "Variation between centers", the difference between the center's response and the provincial mean. These metrics were correlated with center characteristics to identify factors that impacted on variations in practice.RESULTS:Bolus and heterogeneity correction were the only two items checked by all physicists in all centers. In more than half of the centers, image registration and DVH binning are not likely checked by physics. A significant difference in the variation between centers is observed for centers that used a single vendor's products. Centers that used an official checklist indicated higher levels and a wider range of Intra-center variation. Higher workload did not affect the variation in checking patterns between physicists in the same center.CONCLUSIONS:The effect of a center's resources on their checking practice suggest that local environment and workflow be accounted for when implementing TG275 guidelines. The observation that standardized checklists did not reduce checking variability point to the importance of following the checklist development guidelines in MPPG4 to avoid ineffective checklists.

INTRODUCTION:Studies suggest there is utility in computed tomography (CT) radiomics for pancreatic disease; however, the precise biological interpretation of its features is unclear. In this manuscript, we present a novel approach towards this interpretation by investigating sub-micron tissue structure using digital pathology.METHODS:A classification-to attenuation (CAT) function was developed and applied to digital pathology images to create sub-micron linear attenuation maps. From these maps, grey level co-occurrence matrix (GLCM) features were extracted and compared to pathology features. To simulate the spatial frequency loss in a CT scanner, the attenuation maps were convolved with a point spread function (PSF) and subsequently down-sampled. GLCM features were extracted from these down-sampled maps to assess feature stability as a function of spatial frequency loss.RESULTS:Two GLCM features were shown to be strongly and positively correlated (r = 0.8) with underlying characteristics of the tumor microenvironment, namely percent pimonidazole staining in the tumor. All features underwent marked change as a function of spatial frequency loss; progressively larger spatial frequency losses resulted in progressively larger inter-tumor standard deviations; two GLCM features exhibited stability up to a 100 µm pixel size.CONCLUSION:This work represents a necessary step towards understanding the biological significance of radiomics. Our preliminary results suggest that cellular metrics of pimonidazole-detectable hypoxia correlate with sub-micron attenuation coefficient texture; however, the consistency of these textures in face of spatial frequency loss is detrimental for robust radiomics. Further study in larger data sets may elucidate additional, potentially more robust features of biologic and clinical relevance.

PURPOSE:Practical considerations dictated a change in the craniospinal irradiation (CSI) technique. We report our experience in developing and refining CSI planning and treatment parameters, using a 3-isocenter image-guided intensity-modulated radiation therapy (IG-IMRT) technique.METHODS AND MATERIALS:Two institutional values guided development: multidisciplinary decision-making and coordinated considerations throughout simulation, planning, and delivery. Patient immobilization and simulation parameters were selected based on treatment delivery system limitations. Commissioning fluence verification maps were acquired to verify dose in regions of overlapping fields. Robustness analysis was performed to assess impact of potential setup errors measured through IGRT verification. Treatment considerations included order of isocenter imaging and treatment and respective IGRT frequency, modality, and image registration thresholds.RESULTS:Overall film measurements were within 3% of planned dose, confirmed by phantom composite measurements showing all points were within 97% of planned dose. Setup sensitivity analysis suggested a 3-mm setup tolerance was sufficient to ensure confidence in the delivered plan. As the most critical organs at risk were in the superior isocenter, the daily isocenter treatment order was confirmed as superior, middle, and inferior. Daily cone beam computed tomography guidance was chosen for all isocenters (3° rotational threshold). Except for the superior/inferior direction of the middle and inferior isocenters, which were adjusted to 3 mm based on sensitivity analysis, a 1-mm translational threshold was used.CONCLUSIONS:An IG-IMRT CSI technique has been developed and implemented in our institution through a multidisciplinary approach. This process highlights the collaborative, iterative approach used to successfully integrate a new treatment technique in an image-guidance era.

2000 Objectives: Prostate-specific membrane antigen (PSMA)-targeted radiotracers used in PET-CT imaging such as 18F-DCFPyL, have shown higher sensitivity compared to conventional imaging for unveiling disease foci in patients with prostate cancer. The purpose of this study was to evaluate the effects of decreasing PET scan times on image quality by using three metrics: contrast-to-noise ratio (CNR) in the foci, signal-to-noise ratio (SNR) in the liver, and coefficients of variation (CV) of image noise. Additionally, we evaluated the clinical impact of decreased scan time on the Prostate Cancer Molecular Imaging Standardized Evaluation (PROMISE) PSMA score for foci with the lowest and highest uptake values. Methods: Patients were imaged first with PET-MR at 2 hr and then PET-CT approximately 3.5 hr after 18F-DCFPyL injection. Because of the longer uptake time for the PET-CT, whole body PET scans were acquired for 5 min/bed in list mode. List mode data were then rebinned into scan times of 4, 3, 2.5, and 2 min. Patients with two or more reportedly-positive sites were included in this study (n=11). SUV values (max, mean, and peak) were measured for liver, left ventricular cavity for blood pool (BP), and parotids. Liver and BP SUV values were determined within fixed spherical volume-of-interest (VOI) templates (30 and 20 mm diameter) manually placed on PET images using the CT for guidance. Similarly, VOIs were placed on each parotid gland and averaged to derive the parotids SUVmax. Additionally, in each patient the two PSMA-positive foci with low and high uptake were quantified. For each of these, a bounding box (BB) VOI was placed and SUVmean was measured using a 42% threshold of the max value within the BB. To measure SUVpeak, the same BB was used and a 1 cc sphere was centered over the max value. All VOI placements were performed on the 5 min scan and using an independent third-party workstation, the other scan times were coregistered so the same VOIs were applied to all scans. CNR was calculated as (SUVmax,foci - SUVmean,BP)/SUVsd,BP for the foci with lowest SUVmax only. SNR was calculated as SUVmean/sd. CV was calculated as (SUVsd/SUVmean) x 100% for liver, BP, and both foci. PSMA scores were determined for both low and high foci at all scan times by comparing the SUVmean to BP, liver, and parotid as per the PROMISE PSMA scoring system (Eiber et al. J Nucl Med 2018). Results: All SUV values for the low foci (see table) and high foci varied only minimally across the 5 scan times for all patients. In liver, SUVmax varied the most, increasing with decreasing scan times. As expected, CNR low foci data indicate worsening image quality with shorter scan times. SNR for liver shows the same trend: as scan time decreases, the SUVsd in the image increases, thus reducing the SNR. The overall averages of CV for liver, BP, high and low foci (max, mean and peak) ranged from 0.7 to 8.1% with only 4 out of 132 individual values greater than 10%, thus indicating low image noise. PSMA scores changed only in one patient for the high SUV foci from a score of 2 (PSMA expression equal to or above liver and lower than parotid) at both the 2 and 2.5 min scan times, to scores of 1 (equal to or above blood pool and lower than liver) for the 3, 4, and 5 min scan times. Conclusions: Although CNR decreases with shorter scan time, even at 2 min the average CNRmax for all patients was 16 and the lowest individual value was 6, indicating good image quality. SNR in liver was 10 at 3 min, which meets the criteria of good image quality according to recommendations of Fukukita et al. (Ann Nucl Med 2014). Image noise as measured by CV was below the suggested limit of 10% of Akamatsu et al. (J Nucl Med Technol 2015). The PSMA score decreased in only one patient on the two shortest scan times (2 and 2.5 min), warranting further studies to determine the incidence and clinical implications of this observation. In summary, based on these results, our current scan time of 4 min/bed could be safely reduced to 3 min, thereby reducing the total scan time by 8 min from 32 to 24 min.

Purpose: To assess cervical tumor hypoxia using the hypoxia tracer F-18-fluoroazomycin arabinoside (F-18-FAZA) and compare different reference tissues and thresholds for quantifying tumor hypoxia. Methods and Materials: Twenty-seven patients with cervical cancer were studied prospectively by positron emission tomography (PET) imaging with F-18-FAZA before starting standard chemoradiation. The hypoxic volume was defined as all voxels within a tumor (T) with standardized uptake values (SUVs) greater than 3 standard deviations from the mean gluteus maximus muscle SUV value (M) or SUVs greater than 1 to 1.4 times the mean SUV value of the left ventricle, a blood (B) surrogate. The hypoxic fraction was defined as the ratio of the number of hypoxic voxels to the total number of tumor voxels. Results: A F-18-FAZA-PET hypoxic volume could be identified in the majority of cervical tumors (89% when using T/M or T/B > 1.2 as threshold) on the 2-hour static scan. The hypoxic fraction ranged from 0% to 99% (median 31%) when defined using the T/M threshold and from 0% to 78% (median 32%) with the T/B > 1.2 threshold. Hypoxic volumes derived from the different thresholds were highly correlated (Spearman's correlation coefficient rho between T/M and T/B > 1-1.4 were 0.82-0.91), as were hypoxic fractions (0.75-0.85). Compartmental analysis of the dynamic scans showed k(3), the FAZA accumulation constant, to be strongly correlated with hypoxic fraction defined using the T/M (Spearman's rho = 0.72) and T/B > 1.2 thresholds (0.76). Conclusions: Hypoxia was detected in the majority of cervical tumors on F-18-FAZA-PET imaging. The extent of hypoxia varied markedly between tumors but not significantly with different reference tissues/thresholds. (C) 2018 Elsevier Inc. All rights reserved.

PURPOSE:The delivery accuracy of highly conformal dose distributions generated using intensity modulation and collimator, gantry, and couch degrees of freedom is directly affected by the quality of the alignment between the radiation beam and the mechanical axes of a linear accelerator. For this purpose, quality control (QC) guidelines recommend a tolerance of ±1 mm for the coincidence of the radiation and mechanical isocenters. Traditional QC methods for assessment of radiation and mechanical axes alignment (based on pointer alignment) are time consuming and complex tasks that provide limited accuracy. In this work, an automated test suite based on an analytical model of the linear accelerator motions was developed to streamline the QC of radiation and mechanical axes alignment.METHODS:The proposed method used the automated analysis of megavoltage images of two simple task-specific phantoms acquired at different linear accelerator settings to determine the coincidence of the radiation and mechanical isocenters. The sensitivity and accuracy of the test suite were validated by introducing actual misalignments on a linear accelerator between the radiation axis and the mechanical axes using both beam steering and mechanical adjustments of the gantry and couch.RESULTS:The validation demonstrated that the new QC method can detect sub-millimeter misalignment between the radiation axis and the three mechanical axes of rotation. A displacement of the radiation source of 0.2 mm using beam steering parameters was easily detectable with the proposed collimator rotation axis test. Mechanical misalignments of the gantry and couch rotation axes of the same magnitude (0.2 mm) were also detectable using the new gantry and couch rotation axis tests. For the couch rotation axis, the phantom and test design allow detection of both translational and tilt misalignments with the radiation beam axis. For the collimator rotation axis, the test can isolate the misalignment between the beam radiation axis and the mechanical collimator rotation axis from the impact of field size asymmetry. The test suite can be performed in a reasonable time (30-35 min) due to simple phantom setup, prescription-based beam delivery, and automated image analysis. As well, it provides a clear description of the relationship between axes. After testing the sensitivity of the test suite to beam steering and mechanical errors, the results of the test suite were used to reduce the misalignment errors of the linac to less than 0.7-mm radius for all axes.CONCLUSIONS:The proposed test suite offers sub-millimeter assessment of the coincidence of the radiation and mechanical isocenters and the test automation reduces complexity with improved efficiency. The test suite results can be used to optimize the linear accelerator's radiation to mechanical isocenter alignment by beam steering and mechanical adjustment of gantry and couch.

For volumes up to 2 cm3 of the bladder and possibly up to 5 cm3 of the rectum, doses computed from the whole organ were good estimates of the doses in the wall in cervix brachytherapy, and there were no significant differences between patients treated with or without interstitial needles.