CT Simulation Research Articles

A feasibility study of adaptive radiation therapy for postprostatectomy prostate cancer

Postoperative prostate radiotherapy requires large planning target volume (PTV) margins to account for motion and deformation of the prostate bed. Adaptive radiation therapy (ART) can incorporate image-guidance data to personalize PTVs that maintain coverage while reducing toxicity. We present feasibility and dosimetry results of a prospective study of postprostatectomy ART. Twenty-one patients were treated with single-adaptation ART. Conventional treatments were delivered for fractions 1 to 6 and adapted plans for the remaining 27 fractions. Clinical target volumes (CTVs) and small bowel delineated on fraction 1 to 4 CBCT were used to generate adapted PTVs and planning organ-at-risk (OAR) volumes for adapted plans. PTV volume and OAR dose were compared between ART and conventional using Wilcoxon signed-rank tests. Weekly CBCT were used to assess the fraction of CTV covered by PTV, CTV D99, and small bowel D1cc. Clinical metrics were compared using a Student's t-test (p < 0.05 significant). Offline adaptive planning required 1.9 ± 0.4 days (mean ± SD). ART decreased mean adapted PTV volume 61 ± 37 cc and bladder wall D50 compared with conventional treatment (p < 0.01). The CTV was fully covered for 96% (97%) of fractions with ART (conventional). Reconstructing dose on weekly CBCT, a nonsignificant reduction in CTV D99 was observed with ART (94%) compared to conventional (96%). Reduced CTV D99 with ART was significantly correlated with large anterior-posterior rectal diameter on simulation CT. ART reduced the number of fractions exceeding our institution's small bowel D1c limit from 14% to 7%. This study has demonstrated the feasibility of offline ART for post-prostatectomy cancer. ART facilitates PTV volume reduction while maintaining reasonable CTV coverage and can reduce the dose to adjacent normal tissues.

Use of focal radiotherapy boost for prostate cancer: radiation oncologists’ perspectives and perceived barriers to implementation

BackgroundIn a recent phase III randomized control trial, delivering a focal radiotherapy (RT) boost to tumors visible on MRI was shown to improve disease-free survival and regional/distant metastasis-free survival for patients with prostate cancer—without increasing toxicity. The aim of this study was to assess how widely this technique is being applied in current practice, as well as physicians’ perceived barriers toward its implementation.MethodsWe invited radiation oncologists to complete an online questionnaire assessing their use of intraprostatic focal boost in December 2022 and February 2023. To include perspectives from a broad range of practice settings, the invitation was distributed to radiation oncologists worldwide via email list, group text platform, and social media.Results263 radiation oncologist participants responded. The highest-represented countries were the United States (42%), Mexico (13%), and the United Kingdom (8%). The majority of participants worked at an academic medical center (52%) and considered their practice to be at least partially genitourinary (GU)-subspecialized (74%). Overall, 43% of participants reported routinely using intraprostatic focal boost. Complete GU-subspecialists were more likely to implement focal boost, with 61% reporting routine use. In both high-income and low-to-middle-income countries, less than half of participants routinely use focal boost. The most cited barriers were concerns about registration accuracy between MRI and CT (37%), concerns about risk of additional toxicity (35%), and challenges to accessing high-quality MRI (29%).ConclusionsTwo years following publication of a randomized trial of patient benefit without increased toxicity, almost half of the radiation oncologists surveyed are now routinely offering focal RT boost. Further adoption of this technique might be aided by increased access to high-quality MRI, better registration algorithms of MRI to CT simulation images, physician education on benefit-to-harm ratio, and training on contouring prostate lesions on MRI.

Endoscopic Ultrasound-Guided Fiducial Placement for Stereotactic Body Radiation Therapy in Patients with Pancreatic Cancer.

Accurate delivery of stereotactic body radiotherapy (SBRT) to pancreatic tumors relies on successful EUS-guided placement of fiducial markers. The aim of this study is to report the technical feasibility and safety of EUS-guided fiducial placement and to evaluate the characteristics and technical benefit of SBRT in a cohort of patients with pancreatic cancer (PC). A retrospective chart review was performed for all (n = 82) PC patients referred for EUS-guided fiducial placement by a single endosonographer at a tertiary cancer center. Data regarding EUS-related technical details, SBRT characteristics, adverse events, and continuous visibility of fiducials were recorded and analyzed. Most patients included in the study had either locally advanced disease (32 patients, 39%) or borderline resectable disease (29 patients, 35%). Eighty-two PC patients underwent the placement of 230 fiducial markers under EUS guidance. The technical success rate of the fiducial placement was 98%. No immediate EUS-related adverse events were reported. The average time to the simulation CT after fiducial placement was 3.1 days. Of the 216 fiducial markers used for the SBRT delivery, 202 fiducial markers were visible on both the simulation CT and the cone beam CT scan. A median dose of 40cGY was given to all the patients in five fractions. Of these, 41% of the patients reported no SBRT-related toxicities during the follow-up. Fatigue and nausea were the most reported SBRT-related toxicities, which were seen in 35% of the patients post-SBRT. Our results demonstrate that EUS-guided fiducial placement is safe and effective in target volume delineation, facilitating SBRT delivery in PC patients. Further clinical trials are needed to determine the SBRT-related survival benefits in patients with pancreatic cancer.

Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for Pancreatic and Other Intra-Abdominal Cancers.

A 1.5T MRI combined with a linear accelerator (Unity®, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer's pre-set MRI sequences (i.e., T2 Weighted (T2W)), which limited the visualization of pancreatic and intra-abdominal tumors and organs at risk (OAR). Here, a T1 Weighted (T1W) sequence was utilized to improve the visualization of tumors and OAR for online adapted-to-position (ATP) and adapted-to-shape (ATS) during MRI-guided SBRT. Twenty-six patients, 19 with pancreatic and 7 with intra-abdominal cancers, underwent CT and MRI simulations for SBRT planning before being treated with multi-fractionated MRI-guided SBRT. The boundary of tumors and OAR was more clearly seen on T1W image sets, resulting in fast and accurate contouring during online ATP/ATS planning. Plan quality in 26 patients was dependent on OAR proximity to the target tumor and achieved 96 ± 5% and 92 ± 9% in gross tumor volume D90% and planning target volume D90%. We utilized T1W imaging (about 120 s) to shorten imaging time by 67% compared to T2W imaging (about 360 s) and improve tumor visualization, minimizing target/OAR delineation uncertainty and the treatment margin for sparing OAR. The average time-consumption of MRI-guided SBRT for the first 21 patients was 55 ± 15 min for ATP and 79 ± 20 min for ATS.

Integrated experimental and computational analysis of porous media combustion by combining gas-phase synchrotron [formula omitted]CT, IR-imaging, and pore-resolved simulations

Porous media combustion is a promising combustion technology that enables operation over an extended range of conditions, with a variety of fuels and low pollutant emissions. However, the lack of understanding of the interstitial combustion processes remains a major obstacle towards the application of this technology and the development of predictive models. To understand these processes, this study presents an integrated experimental and computational effort to examine porous media combustion. Specifically, a new experimental diagnostic method is employed that simultaneously combines synchrotron X-ray micro-computed tomography (μCT) and short-wavelength infrared thermometry. With this approach, the surface temperature and the 3D gas-phase temperature field are simultaneously measured inside a porous burner with micrometer spatial resolution. These measurements are then integrated into 3D pore-resolved simulations. This integrated approach enables a direct evaluation of current modeling capabilities, and a unique analysis of interstitial combustion in porous foams under realistic heating conditions. In light of these results, we discover that about 80% of the fuel consumption inside the matrix pores occurs far enough from the porous surface to be characteristic of a decoupled regime of preheated, but adiabatic flamelets. The remaining fuel consumption near the pore surface occurs in a non-adiabatic combustion mode. This insight and the proposed approach contribute to our fundamental understanding of porous media combustion, and suggest that multi-regime models could more accurately describe porous burners.

Can we skip the simulation step for radiation treatment planning in patients with symptomatic bone metastases?

255 Background: Patients with bone metastases may require urgent radiation treatment (RT) due to severe pain, neurologic or other symptoms. Conventional approaches typically involve a 3-step process: initial consultation, followed several days later by a planning CT (pCT) simulation and dosimetric planning, and finally RT delivery. The time frame from consultation to RT can be up to 2 weeks, overly lengthy for severely symptomatic patients. We explored the viability of using diagnostic CT (dCT) imaging, usually available to radiation oncologists at the time of consultation, for RT planning - with the ultimate goal of removing the simulation step to reduce the interval from consultation to RT. In this initial phase of the project, we set out to compare differences in key dosimetric parameters from dCT- and pCT- generated RT plans. Methods: We retrospectively reviewed patients (n=28) treated for bone metastases at a single academic institution from 2020-2023. We utilized rigid image registration to transfer physician contours from pCT images to dCT images to account for changes in patient positioning. Beam arrangements, energies, and administered monitor units were also transferred from the pCT to the dCT for accurate dose calculation. We calculated RT dose coverage of each target metastasis using “V100”, or the percentage of the target lesion receiving 100% of the RT prescription dose. Correspondingly, the “V95” and the maximum point dose (“hotspot”) in patients were also calculated. Results: Out of 28 patients, 24 were treated to single and 4 to multiple (2-4) bone metastases. We excluded patients who had no dCT (n=7) or whose body positioning on the dCT (e.g. arms) created obstructions for beam arrangements (n=2). Eventually, 24 clinical plans made from 19 patients’ pCTs were migrated to their dCTs to generate comparable dosimetric plans. For all 24 dCT-based plans (12 spines and 12 extremities), the mean full dose coverage V100 decreased by 7.14% ± 15.89%. Overall, the plans had 91.14% ± 18.6% for V95 to PTV. Hotspots rose by 2.75% ± 3.61%. Two cases were observed to have full-dose-coverage drop over 40%: one was caused by patient’s outline change induced by different couches used for diagnosis and simulation, and the other one had an initial coverage of 57.6% for V100 in the original clinical plan. The remaining plans had a drop of 3.14% ± 8.37% on V100, and 96.1% ± 8.2% for V95. Conclusions: It was feasible to generate radiation treatment plans for bone metastases with good tumor coverage using dCT imaging. Patient selection plays a crucial role in dCT-based treatment planning, as the dose distribution is highly sensitive to anatomical variations resulting from patient positioning. This treatment planning approach circumvents the simulation step and would reduce patients' wait time for RT, thereby enabling more rapid access to RT for patients suffering with symptoms from bone metastases.

Feasibility of Coronary Access Following Redo-TAVR for Evolut Failure: A Computed Tomography Simulation Study.

Coronary accessibility following redo-transcatheter aortic valve replacement (redo-TAVR) is increasingly important, particularly in younger low-risk patients. This study aimed to predict coronary accessibility after simulated Sapien-3 balloon-expandable valve implantation within an Evolut supra-annular, self-expanding valve using pre-TAVR computed tomography (CT) imaging. A total of 219 pre-TAVR CT scans from the Evolut Low-Risk CT substudy were analyzed. Virtual Evolut and Sapien-3 valves were sized using CT-based diameters. Two initial Evolut implant depths were analyzed, 3 and 5 mm. Coronary accessibility was evaluated for 2 Sapien-3 in Evolut implant positions: Sapien-3 outflow at Evolut node 4 and Evolut node 5. With a 3-mm initial Evolut implant depth, suitable coronary access was predicted in 84% of patients with the Sapien-3 outflow at Evolut node 4, and in 31% of cases with the Sapien-3 outflow at Evolut node 5 (P<0.001). Coronary accessibility improved with a 5-mm Evolut implant depth: 97% at node 4 and 65% at node 5 (P<0.001). When comparing 3- to 5-mm Evolut implant depth, sinus sequestration was the lowest with Sapien-3 outflow at Evolut node 4 (13% versus 2%; P<0.001), and the highest at Evolut node 5 (61% versus 32%; P<0.001). Coronary accessibility after Sapien-3 in Evolut redo-TAVR relates to the initial Evolut implant depth, the Sapien-3 outflow position within the Evolut, and the native annular anatomy. This CT-based quantitative analysis may provide useful information to inform and refine individualized preprocedural CT planning of the initial TAVR and guide lifetime management for future coronary access after redo-TAVR. URL: https://www.clinicaltrials.gov; Unique identifier: NCT02701283.

Active Breathing Coordinator reduces radiation dose to the stomach in patients with left breast cancer

Background/Purpose Gastric dose parameters comparison for deep inspiration breath-hold (DIBH) or free breathing (FB) mode during radiotherapy (RT) for left-sided breast cancer patients (LSBCPs) has not been investigated before. This study aimed to analyze the impact of Active Breath Coordinator (ABC)-DIBH technique on the dose received by the stomach during RT for LSBCPs and to provide organ-specific dosimetric parameters. Materials and methods The study included 73 LSBCPs. The dosimetric parameters of the stomach were compared between FB and DIBH mode. The correlation between the stomach volume and dosimetric parameters was analyzed. Results Compared to FB mode, statistically significant reductions were observed in gastric dose parameters in ABC-DIBH mode, including Dmax (46.60 vs 17.25, p < 0.001), D1cc (38.42 vs 9.60, p < 0.001), Dmean (4.10 vs 0.80, p < 0.001), V40Gy (0.50 vs 0.00, p < 0.001), V30Gy (6.30 vs 0.00, p < 0.001), V20Gy (20.80 vs 0.00, p < 0.001), V10Gy (51.10 vs 0.77, p < 0.001), and V5Gy (93.20 vs 9.60, p < 0.001). ABC-DIBH increased the distance between the stomach and the breast PTV when compared to FB, from 1.3 cm to 2.8 cm (p < 0.001). Physiologic decrease in stomach volume was not found from FB to ABC-DIBH (415.54 cm3 vs 411.61 cm3, p = 0.260). The stomach volume showed a positive correlation with V40Gy (r2 = 0.289; p < 0.05), V30Gy (r2 = 0.287; p < 0.05), V20Gy (r2 = 0.343; p < 0.05), V10Gy (r2 = 0.039; p < 0.001), V5Gy (r2 = 0.439; p < 0.001), Dmax (r2 = 0.269; p < 0.05) and D1cc (r2 = 0.278; p < 0.05) in FB mode. While in ABC-DIBH mode, most stomach dosimetric parameters were not correlated with gastric volume. Conclusions The implementation of ABC-DIBH in LSBCPs radiotherapy resulted in lower irradiation of the stomach. Larger stomach volume was associated with statistically significantly higher dose irradiation in FB mode. To reduce radiotherapy related side effects in FB mode, patients should be fast for at least 2 hours before the CT simulation and treatment.

Prosedur Teknik Penyinaran Metode Intensity Modulated Radiation Therapy(IMRT) Kelenjar Getah Bening Pada Kasus Limfoma Hodgkin (LH) Di Rumah Sakit Umum Pusat DR.Hasan Sadikin

Latar Belakang: Lymph node cancer in the case of Hodkin's Lymphoma is a type of cancer. Lymphoma is a solid tumor of the immune system. Hodgkin lymphoma (HL) accounts for about 10% of all lymphomas. The Intensity Modulated Radiation Therapy (IMRT) technique is one of the cancer treatment techniques in Hodgkin's Lymphoma cases. The aim of this research is to determine the procedure and reasons for using the IMRT technique in lymph node cancer in Hodkin's Lymphoma cases.Metode: This research is qualitative research with a case study approach using retrospective data. The research time is from 24 to 30 May 2023 and the research location is in the Department of Radiation Oncology, RSUP Dr. Hasan Sadikin Bandung. The research subjects consisted of Radiation Oncologists, Medical Physics, Radiotherapists. Researchers collected data from patient medical records, made interview transcripts and carried out data reduction and processed it using open coding, and provided it in the form of quotations and then drew conclusions.Hasil: The procedure for irradiating Hodgkin's Lymphoma using the IMRT technique at the RSHS Department of Radiation Oncology begins with positioning the patient on the examination table with a fixation device and arranging the patient according to the reference point of the CT Simulator and making a thermoplastic mask then carrying out verification and irradiation. The IMRT technique has the advantage of using MLC so that the radiation is modulated according to the contour of the target and the disadvantage of precise dose distribution in limiting the radiation dose to organs at risk.Kesimpulan: In the case of the Department of Radiation Oncology, Dr. Hasan Sadikin Hospital, Bandung, the IMRT technique was used with consideration, namely that the IMRT technique already uses MLC which creates individual blocks automatically according to the projections depicted on the TPS.&#x0D;

Treatment Volume Determination in Small Cell Lung Cancer Patients

Objective: In this study, we evaluated treatment volume determination with PET-CT fusion for small cell lung cancer. Materials and methods: Primary goal of this study has been to evaluate treatment volume determination for fused PET-CT in patients with small cell lung cancer. We have carried out a comparative analysis of treatment volume determination by CT simulation images only or by integration of PET. While we primarily focused on evaluation of incorporated multimodality imaging for treatment volume determination, we also assessed critical organ contouring along with interobserver and intraobserver variations. Ground truth target volume has been utilized for comparative analysis, and it was determined by board certified radiation oncologists after detailed evaluation of all imaging and relevant data with thorough colleague peer review and consensus.

A preliminary study of dynamic interactive simulation and computational CT scan of the ideal alveolus model.

While the development of CT imaging technique has brought cognition of in vivo organs, the resolution of CT images and their static characteristics have gradually become barriers of microscopic tissue research. Previous research used the finite element method to study the airflow and gas exchange in the alveolus and acinar to show the fate of inhaled aerosols and studied the diffusive, convective, and sedimentation mechanisms. Our study combines these techniques with CT scan simulation to study the mechanisms of respiratory movement and its imaging appearance. We use 3D fluid-structure interaction simulation to study the movement of an ideal alveolus under regular and forced breathing situations and ill alveoli with different tissue elasticities. Additionally, we use the Monte Carlo algorithm within the OpenGATE platform to simulate the computational CT images of the dynamic process with different designated resolutions. The resolutions show the relationship between the kinematic model of the human alveolus and its imaging appearance. The results show that the alveolus and the wall thickness can be seen with an image resolution smaller than 15.6μm. With ordinary CT resolution, the alveolus is expressed with four voxels. This is a preliminary study concerning the imaging appearance of the dynamic alveolus model. This technique will be used to study the imaging appearance of the dynamic bronchial tree and the lung lobe models in the future.

A national survey on the medical physics workload of external beam radiotherapy in Japan†.

Several staffing models are used to determine the required medical physics staffing, including radiotherapy technologists, of radiation oncology departments. However, since Japanese facilities tend to be smaller in scale than foreign ones, those models might not apply to Japan. Therefore, in this study, we surveyed workloads in Japan to estimate the optimal medical physics staffing in external beam radiotherapy. A total of 837 facilities were surveyed to collect information regarding radiotherapy techniques and medical physics specialists (RTMPs). The survey covered facility information, staffing, patient volume, equipment volume, workload and quality assurance (QA) status. Full-time equivalent (FTE) factors were estimated from the workload and compared with several models. Responses were received from 579 facilities (69.2%). The median annual patient volume was 369 at designated cancer care hospitals (DCCHs) and 252 across all facilities. In addition, the median FTE of RTMPs was 4.6 at DCCHs and 3.0 at all sites, and the average QA implementation rate for radiotherapy equipment was 69.4%. Furthermore, advanced treatment technologies have increased workloads, particularly in computed tomography simulations and treatment planning tasks. Compared to published models, larger facilities (over 500 annual patients) had a shortage of medical physics staff. In very small facilities (about 140 annual patients), the medical physics staffing requirement was estimated to be 0.5 FTE, implying that employing a full-time medical physicist would be inefficient. However, ensuring the quality of radiotherapy is an important issue, given the limited number of RTMPs. Our study provides insights into optimizing staffing and resource allocation in radiotherapy departments.

A Comprehensive Primer on Radiation Oncology for Non-Radiation Oncologists.

Background: Multidisciplinary management is crucial in cancer diagnosis and treatment. Multidisciplinary teams include specialists in surgery, medical therapies, and radiation therapy (RT), each playing unique roles in oncology care. One significant aspect is RT, guided by radiation oncologists (ROs). This paper serves as a detailed primer for non-oncologists, medical students, or non-clinical investigators, educating them on contemporary RT practices. Methods: This report follows the process of RT planning and execution. Starting from the decision-making in multidisciplinary teams to the completion of RT and subsequent patient follow-up, it aims to offer non-oncologists an understanding of the RO's work in a comprehensive manner. Results: The first step in RT is a planning session that includes obtaining a CT scan of the area to be treated, known as the CT simulation. The patients are imaged in the exact position in which they will receive treatment. The second step, which is the primary source of uncertainty, involves the delineation of treatment targets and organs at risk (OAR). The objective is to ensure precise irradiation of the target volume while sparing the OARs as much as possible. Various radiation modalities, such as external beam therapy with electrons, photons, or particles (including protons and carbon ions), as well as brachytherapy, are utilized. Within these modalities, several techniques, such as three-dimensional conformal RT, intensity-modulated RT, volumetric modulated arc therapy, scattering beam proton therapy, and intensity-modulated proton therapy, are employed to achieve optimal treatment outcomes. The RT plan development is an iterative process involving medical physicists, dosimetrists, and ROs. The complexity and time required vary, ranging from an hour to a week. Once approved, RT begins, with image-guided RT being standard practice for patient alignment. The RO manages acute toxicities during treatment and prepares a summary upon completion. There is a considerable variance in practices, with some ROs offering lifelong follow-up and managing potential late effects of treatment. Conclusions: Comprehension of RT clinical effects by non-oncologists providers significantly elevates long-term patient care quality. Hence, educating non-oncologists enhances care for RT patients, underlining this report's importance.

May we routinely spare hippocampal region in primary central nervous system lymphoma during whole brain radiotherapy?

PurposeOne of the main limiting factors of whole-brain radiation therapy (WBRT) for primary central nervous system lymphoma (PCNSL) is the impairment of neurocognitive functions (NCFs), which is mainly caused by radiation-induced injury to the hippocampus. With a view to preventing NCF impairment and personalizing treatment, we explored the feasibility of sparing the hippocampus during WBRT by correlating the sites of PCNSL lesions with the hippocampus.Methods and materialsPre-treatment MR images from patients who underwent WBRT between 2010 and January 2020—and post-radiotherapy images in cases of relapse—were imported into the Varian Eclipse treatment-planning system and registered with the simulation CT. We constructed three 3-dimensional envelopes around the hippocampus at distances of 5, 10 and 15 mm and also contoured primary lesions and recurrences.ResultsWe analyzed 43 patients with 66 primary lesions: 9/66 (13.6%) involved the hippocampus and 11/66 (16.7%) were located within 5 mm of it. Thirty-six lesions (54.5%) were situated more than 15 mm from the hippocampus, while 10/66 (15.2%) were between 5 and 15 mm from it. The most common location was in deep brain structures (31%). Thirty-five of the 66 lesions relapsed: in field in 14/35 (40%) and outfield in 21/35 (60%) in different sites. Globally, 16/35 recurrences (45.7%) were located in the hippocampus or within 5 mm of it.ConclusionThese data show that routinely sparing the hippocampus is not feasible. This approach could be considered in selected patients, when the lesion is more than 15 mm from the hippocampus.

Significance of Radiomics in Predicting Local Control for Patients with Malignant Liver Tumors Treated Using Stereotactic Body Radiotherapy.

We routinely deliver Stereotactic Body Radiotherapy (SBRT) in malignant liver tumors using planning computed tomography (CT) and Magnetic Resonance Images (MRI) to aid target definition. In this study, we extracted radiomic features from the MR images to predict local control (LC) post-SBRT. We retrospectively analyzed patients with either hepatocellular cancers (HCCs) or liver metastases (Mets) treated with SBRT between Aug 2014 and Aug 2020. All patients had CT simulation followed by 1.5 Tesla planning MRI in treatment position. Contrast enhanced T1 VIBE and T2 Haste MR sequences were registered with planning CT for target definition. Radiomic features were extracted from Gross Tumor Volumes (GTV) masked out of 60 seconds post contrast T1 VIBE MR images using the Radiomics calculator tool RaCaT. The output included 480 (408 textural, 50 intensity and 22 morphological) features for each target. Principal Component Analysis of the outputs obtained from all the targets yielded 20 radiomic feature clusters after computational prioritization. These clusters were correlated to LC outcomes at various time points post-SBRT. LC was defined as non-progressive disease. Accuracy of predictions was measured by area under (AUC) receiver operating characteristic curve. Cox regression analysis was done to find univariate and multivariate clinical [HCCs vs. Mets, single vs. multiple lesions, previous local therapy (yes vs. no), GTV volume (≤40 vs. >40 cc)], radiomic and dosimetric predictors (continuous) of LC. In total, 97 patients received SBRT to 122 lesions. The median dose prescribed was 45 Gy (range, 30-50 Gy). Median age was 69 years (interquartile range, IQR 61-73 yrs.). 59 patients had HCCs and 38 had Mets. 24 lesions had prior ablative therapy. 75 patients had one target, and 22 had multiple targets. Median GTV was 43.5 cc (IQR 23.4-78.6 cc). Median follow up was 16.6 months (IQR 9.7-27.2 mths). Median LC was 13.6 months (IQR 8.0-23.5 mths). On univariate analysis, histology (HCCs vs. Mets; Hazard ratio (HR) 2.9, 95% CI 1.4-6.4; p < 0.006), radiomic clusters (p < 0.006) and the max., mean, and min. doses to GTV and Planning Target Volumes correlated with improved LC (all p-values < 0.05). On multivariate analysis, histology (HCCs vs. Mets; HR 4.4, 95% CI 1.6-12.3; p = 0.004), radiomic clusters (p = 0.034) and prescription dose (p = 0.048) were significant covariates. Specifically, the 20 radiomic clusters were predictive of LC, and the accuracy of predictions showed promise with AUC values of 0.74, 0.80, and 0.81 at 12, 24, and 36 months post-SBRT, respectively. AUC values for LC in HCCs vs. Mets at 12, 24, and 36 months were 0.83, 0.77, and 0.70, and 0.66, 0.77, and 0.88, respectively. MR-based radiomics predict LC post-SBRT in patients with malignant liver tumors. Further research focused on independent validation of the model is required to explore its clinical use.

Utility of the "All of Us" Database for Radiation Oncology Research.

We provide an overview the All of Us Research Program, a National Institutes of Health funded research database, and report on the utility of this database for Radiation Oncology research. The All of Us Research Program aims to create a large and diverse health database with participants from across the US. Patients consent to join the database and agree to share electronic health records, complete surveys, provide physical measurements, and donate at least one biospecimen. In this observational study, we used the public data browser feature of the All of Us Dataset to evaluate utility for future radiation oncology research. Within the database, we report on the number of cases of common cancers in the US, using ICD10 codes, and also the number of patients treated with common radiotherapy procedures, using CPT4 codes. We then qualitatively report on additional data of interest. Of note, public patient counts in All of Us is rounded to the nearest interval of 20. Additional tiers of data access exist, including individual level data, which were not used in this survey of public data. The database includes 372,380 participants, of which 46,380 patients have a diagnosis of cancer. Within the identified top 10 cancers according to ACS, there were a total of 26,540 primary malignant cancers. The most common type of cancers were breast cancer (ICD10 - c50 [n = 6,960]), Prostate (ICD10 - c61 [n = 4,500]), Non-Hodgkin lymphoma (ICD10 - c85 [n = 2860]), Lung & bronchus (ICD10 - c34 [n = 2000]), Colon (ICD10 - c18 [n = 1940]), Melanoma of the skin (ICD10 - c43 [n = 1740]), Thyroid(ICD10 - c73 [n = 1720]), Kidney (ICD10 - c64 [n = 1300]), Urinary bladder (ICD10 - c67 [n = 1140]). The most common radiation therapy procedures were Computerized Tomography simulation (CPT - 77290 [n = 4,040]), Intensity Modulated Radiation Therapy (CPT - 77386 [n = 780]), 3D conformal radiation therapy (CPT - 77412 [n = 1,720]), Stereotactic Body Radiation Therapy (CPT - 77373 [n = 400]), Brachytherapy (CPT - 77770- 77772 [n = 240]), and Proton Therapy (CPT - 77520-77525 [n = 140]). Qualitatively, other data within All of Us include labs values, drug exposures, comorbidities, other procedures, physical measurements, and wearable biometrics (Fitbit) data. Genomic data typically includes germline testing using whole genome sequencing or genotyping array. Patient surveys include data on personal medical history, family health history, lifestyle, social determinants of health, COVID19 experience, and overall health. Potential outcome variables of interest to oncology research in the database include survival, cause of death, additional procedures or diagnoses after cancer treatment, and quality of life metrics derived from the survey instruments. The All Of Us Research Database includes a large number of cancer cases, of which a substantial number received radiotherapy. Future work will focus on focused hypothesis-driven research questions.

Dosimetric Advantages of VMAT TBI Plans: A Direct Comparison to Conventional TBI Plans.

Total body irradiation (TBI) continues to play an integral role in the conditioning of patients undergoing bone marrow transplantation. Historically, conventional TBI (C-TBI) has been delivered based on a clinical plan without CT simulation. However, volumetric modulated arc therapy TBI (V-TBI) is emerging as an alternative method to deliver TBI in a contemporary fashion. We aimed to compare these two methods of TBI delivery. Patients undergoing treatment with V-TBI were identified. C-TBI plans were created using their existing simulation CT images. Patient thickness was measured on the scan and compensators such as lead sheets to attenuate dose in areas with less separation and lung blocks drawn on digitally reconstructed radiographs (DRR) were added when necessary. A 3D dose distribution was then calculated allowing for the direct comparison between C-TBI and V-TBI on the same patient using the same CT image set. Dosimetric data from each plan including target volume coverage, dose homogeneity, absolute max dose, and dose to lungs were recorded. V-TBI and C-TBI plans for a total of four patients were preliminarily analyzed. Two patients were prescribed 200 cGy in a single fraction, while the other two were prescribed 1200 cGy in eight fractions. V-TBI resulted in a more favorable dosimetry for all four patients in most evaluated metrics including dose coverage, dose homogeneity, and lung dose (Table 1). V-TBI did result in an increased absolute maximum dose to all four patients compared to c-TBI, but still met the desired constraint of D0.03cc<125%. V-TBI resulted in more favorable dosimetry for all four patients compared to C-TBI. To our knowledge, this is the first direct dosimetric comparison between the two methods. Analysis of 8 more V-TBI cases is currently underway. In the future, we plan to design a prospective study to evaluate the clinical outcomes of patients undergoing V-TBI vs C-TBI.

Radiation Treatment Preparation Safety Risk Prediction.

To determine the effect of delays in radiation treatment preparation task timeliness on reported safety events. For 2022, all patients treated at four community-based radiation oncology clinics were included for analysis. Safety reports which occurred during treatment preparation tasks (i.e., between CT simulation and the first treatment) were included for this analysis. Patients with a reported safety event were the report cohort and those without were the control cohort. Treatment preparation tasks are completed sequentially and included contouring, treatment planning, Radiation Oncologist review, Medical Physicist review, Therapist quality check. At baseline, each task was scheduled a standard interval for completion based on treatment technique. The time taken to complete each task was captured using ARIA v16.0 Care Path module (Varian Medical Systems, Palo Alto, CA) and extracted through database query. For each task, two metrics were quantified: Task (1) Completion Timeliness: the time (hours) to complete each task, relative to the time allocated to each task. A negative value indicated more time taken than scheduled. (2) Overall Timeliness: specific task timeliness (hours) relative to overall timeliness for the whole Care Path. A negative value indicated the tasks were behind schedule. A student's t-test with an alpha of 0.05 was used to indicate significance. Over the study period, 66 courses had a reported treatment preparation safety event (report) and 2690 did not (control). Techniques include 54% and 56% 3DCRT, 35% and 35% IMRT, 3% and 3% SRS, and 6% and 8% SBRT, for the report and control groups, respectively. Disease sites include breast, GU, GI, head and neck, CNS, thoracic, skin, secondary, gynecological, sarcoma, and heme. Table 1 displays the timeliness for each of the five tasks. Of the courses with safety events, overall timeliness was significantly behind the control group from the in contouring, treatment planning, Radiation Oncologist review, and Medical Physicist review. Courses with safety events took significantly more time than scheduled early in treatment preparation with a significant increase at treatment planning and significantly less time towards the end with the therapist quality check. Patient courses with reported safety events had significantly longer treatment planning times, and as a result inadequate time to perform each downstream pre-treatment activity. The implication of this analysis is that a flag could be created to indicate risk of a safety event early in the treatment preparation process.

CT-on-Rails Utilization for Image Guidance and Plan Adaptation at a Single-Room Proton Therapy Center.

In-room CT-on-rails is a relatively rare imaging modality in proton therapy. This work evaluated the utilization of CT-on-rails (CTOR) for image guidance and plan adaptation at a single-room proton therapy center. All patients treated from the proton center beginning treatment to the current date were evaluated (May 2021 - January 2023). Patients were treated using a Mevion S250i scanning beam proton therapy system with an in-room Definition Edge CTOR. The image guidance technique utilized for each patient was evaluated (CTOR, orthogonal planar kV imaging, or both). For patients who required a new CT for plan adaptation, the use of CT images from CTOR or a new simulation CT was assessed. Of the 132 patients treated over the evaluated time period, 56.0% utilized CTOR for image guidance at some point during their treatment. 21.2% utilized CTOR as the only image guidance technique, while 34.8% utilized CTOR in combination with kV planar imaging. For 43.9% of patients, only orthogonal planar kV imaging was utilized. Head and neck treatment sites most often utilized CTOR alone as an image guidance technique, while central nervous system sites most often utilized kV planar imaging alone. Of the patients who required new CT imaging for plan adaptation, 75.0% utilized CTOR images. Some reasons for patients not being able to utilize CTOR imaging for re-planning were the need for 4DCT imaging (which was not available on the CTOR) or the need to re-make immobilization devices (such as thermoplastic masks due to becoming loose). CTOR was shown to be utilized for image guidance in the majority of patients receiving proton therapy at a single-room proton therapy center. CTOR was able to be used for plan adaptation in a large majority of patients, eliminating the need to schedule additional CT simulation appointments for these patients.

Online Correction of Intrafraction Motion during Volumetric Modulated Arc Therapy for Prostate Radiotherapy: A Cohort Study Quantifying the Frequency of Shifts and Analysis of Men at Highest Risk.

We have previously described our early experience using fiducial markers to correct for intrafraction motion during radiation therapy (RT) to the prostate using the TrueBeam Advanced imaging package. We sought to further characterize the utility of this approach in a larger cohort, and analyze factors associated with intrafraction motion. A total of 132 men with fiducial markers treated with RT for intact prostate cancer at a single center were treated with a VMAT technique using 2-3 arcs. All patients underwent planning CT after a rectal enema and same day placement of 3 fiducial markers (Gold Anchor). Triggered kV images were acquired every 10 seconds using an onboard imaging system. Intrafraction motion correction was considered if any two fiducial markers were observed beyond a 3 mm tolerance margin. A manual 2D-3D match was performed using the fiducial markers from the single triggered kV image to obtain a couch shift. Shift data were extracted from the record and verify system and expressed as a single 3-dimensional translation. Shift percent was defined as the number of instances of a >3 mm intrafraction correction divided by the total number of fractions for a given patient. Clinical variables were evaluated, including body mass index, hormone therapy (ADT), prostate, rectal bladder volumes, and rectal width (transverse dimension of rectum at the mid-gland of prostate on simulation CT). Across 2659 fractions, intrafraction motion correction was performed 582 times, in 463 fractions (17%). 101/132 patients (77%) had at least one shift during their treatment course, and 48/132 patients (36%) had shifts with an average magnitude of at least 5 mm. The median shift was 3.6 mm (range, 0-2.4 cm; IQR, 1.5-5.4 mm). 25% of men had a shift percent >20% (SP>20%). Univariate analysis revealed that only larger rectal volume or width, smaller prostate size, and use of ADT were associated with SP>20% (p<0.05). Men with rectal width in the top quartile (>3.6 cm) were more likely to have intrafraction motion corrected with SP>20% (47% vs 18%, p = 0.0016), and similarly men with rectal volume in the top quartile (>112 cc) were more likely to have SP>20% (44% vs 19%, p = 0.0067). On multivariate analysis, only rectal parameters (e.g., top quartile rectal width, HR 3.9, p = 0.0024) were correlated with a higher frequency of intrafraction motion. Intrafraction motion occurs in a significant percentage of men undergoing prostate RT with VMAT, and is correctable utilizing a common feature. On multivariate analysis, rectal volume and width were associated with larger shift percent. Treatment approaches which do not account for intrafraction motion should consider including methods of immobilization, or larger PTV margins in order to avoid marginal miss of the prostate.