Radiation Delivery Research Articles

Dosimetric Impact of Voluntary Deep Inspiration Breath Hold (DIBH) in Mediastinal Hodgkin Lymphomas: A Comparative Evaluation of Three Different Intensity Modulated Radiation Therapy (IMRT) Delivery Methods Using Voluntary DIBH and Free Breathing Techniques.

Hodgkin lymphomas are radiosensitive and curable tumors that often involve the mediastinum. However, the application of radiation therapy to the mediastinum is associated with late effects including cardiac and pulmonary toxicities and secondary cancers. The adoption of conformal IMRT and deep inspiration breath- hold (DIBH) can reduce the dose to healthy normal tissues (lungs, heart and breast). We compared the dosimetry of organs at risk (OARs) using different IMRT techniques for two breathing conditions, i.e., deep inspiration breath hold (DIBH) and free breathing. Twenty-three patients with early-stage mediastinal Hodgkin lymphomas were accrued in the prospective study. The patients were given treatment plans which utilized full arc volumetric modulated arc therapy (F-VMAT), Butterfly VMAT (B-VMAT), and fixed field IMRT (FF-IMRT) techniques for both DIBH and free breathing methods, respectively. All the plans were optimized to deliver 95% of the prescription dose which was 25.2 Gy to 95% of the PTV volume. The mean dose and standard error of the mean for each OAR, conformity index (CI), and homogeneity index (HI) for the target using the three planning techniques were calculated and compared using Student's t-test for parametric data and Wilcoxon signed-rank test for non-parametric data. The HI and CI of the target was not compromised using the DIBH technique for mediastinal lymphomas. The mean values of CI and HI for both DIBH and FB were comparable. The mean heart doses were reduced by 2.1 Gy, 2.54 Gy, and 2.38 Gy in DIBH compared to FB for the F-VMAT, B-VMAT, and IMRT techniques, respectively. There was a significant reduction in V5Gy, V10Gy, and V15Gy to the heart (p < 0.005) with DIBH. DIBH reduced the mean dose to the total lung by 1.19 Gy, 1.47 Gy, and 1.3 Gy, respectively. Among the 14 female patients, there was a reduction in the mean right breast dose with DIBH compared to FB (4.47 Gy vs. 3.63 Gy, p = 0.004). DIBH results in lower heart, lung, and breast doses than free breathing in mediastinal Hodgkin Lymphoma. Among the different IMRT techniques, FF-IMRT, B-VMAT, and F-VMAT showed similar PTV coverage, with similar conformity and homogeneity indices. However, the time taken for FF-IMRT was much longer than for the F-VMAT and B-VMAT techniques for both breathing methods. B-VMAT and F-VMAT emerged as the optimal planning techniques able to achieve the best target coverage and lower doses to the OARs, with less time required to deliver the prescribed dose.

(016) Sexual Health Toxicity Following MRI-Guided versus CT-guided Prostate SBRT

Abstract Introduction Sexual health toxicities remain an under-reported but important health outcome for patients undergoing radiotherapy for localized prostate cancer. With the increasing adoption of higher daily doses of radiation over shorter timeframes delivered using stereotactic body radiotherapy (SBRT), the precision of radiation delivery remains an important factor that can reduce patient toxicity. MRI-guided SBRT (MRgRT) allows for improved image quality, treatment gating, and planning target volume margin reduction, offering improved radiation precision, which may translate to reduced treatment-related toxicity as compared to traditional CT-guided SBRT (CTgRT). Objective We sought to evaluate the effect of MRI-guidance on sexual health toxicity in patients following prostate SBRT for the treatment of localized prostate cancer. Methods We conducted a post-hoc analysis of patients enrolled on a phase III single-center randomized trial (MIRAGE: NCT04384770). The trial overall seeks to study the relative benefit of MRI vs CT guided SBRT (40 Gy/5 fractions) in patients with localized prostate cancer. Right and left neurovascular bundles (NVBs) and internal pudendal arteries (IPAs) were contoured on treatment planning images. Dosimetric parameters for these structures (Dmax, Dmin, Dmean, and V20Gy) were collected. Patient-reported sexual function outcomes (SHIM and EPIC-26 surveys) were also collected prior to treatment and at 1, 3, and 12 months following treatment. A clinically relevant decrement was defined as a ≥24 point decrease in the EPIC-26 sexual domain scores and a ≥9 point decrease on SHIM surveys. Unpaired t-tests and chi-square tests were used to evaluate for statistical significance. Results 152 patients received either MRgRT (n = 77) or CTgRT (n = 75). MRgRT resulted in a significant improvement in the volume receiving 20 Gy or less of radiation (V20Gy) in the left NVB (7.3cc vs 10.9cc, p = 4.4x10-8), right NVB (7.0cc vs 10.7cc, p = 2.8x10-7), and right IPA (0.42cc vs 1.35cc, p = 0.049), and trended towards significance for the left IPA (0.3cc vs 1.1cc, p = 0.066). Only 48 patients were not given hormonal therapy with radiotherapy. No statistically significant differences in clinically relevant decrements in patient-reported SHIM or EPIC scores were seen between MRgRT and CTgRT in these patients. No clear association between acute or chronic (12-months post-RT) sexual health toxicity and radiation exposure to the NVBs or IPAs was identified. Conclusions Patients treated with MRgRT had decreased radiation exposure to the bilateral NVBs and IPAs compared to patients treated with CTgRT. These data highlight the dosimetric benefits of MRgRT with regard to sexually relevant organs at risk. Power to detect associations between dosimetry and patient-reported sexual health outcomes will increase as the data matures and more patients have recovered testosterone after use of hormonal therapy. Future work will assess the impact on MRI-guided vs CT-guided radiation on sexual health outcomes at later time points. Disclosure No.

Resolving signal drift in the wall-mounted camera of the RGSC system.

To present a modified calibration method to reduce signal drift due to table sagging in Respiratory Gating for Scanner (RGSC) systems with a wall-mounted camera. Approximately 70kg of solid water phantoms were evenly distributed on the CT couch, mimicking the patient's weight. New calibration measurements were performed at 9 points at the combination of three lateral positions, the CT isocenter and±10cm laterally from the isocenter, and three longitudinal locations, the CT isocenter and±30cm or±40cm from the isocenter. The new calibration was tested in two hospitals. Implementing the new weighed calibration method at the extended distance yielded improved results during the DIBH scan, reducing the drift to within 1 from 3mm. The extended calibration positions exhibited similarly reduced drift in both hospitals, reinforcing the method's robustness and its potential applicability across all centers. This proposed solution aims to minimize the systematic error in radiation delivery for patients undergoing motion management with wall-mounted camera RGSC systems, especially in conjunction with a bariatric CT couchtop.

Beginning of clinical treatment using the 1.5 Tesla MR-Linac system in Japan: a narrative review.

In the field of radiation therapy, image-guided radiotherapy (IGRT) technology has been gradually improving and highly accurate radiation treatment has been possible. Research on IGRT using 1.5 Tesla magnetic resonance imaging (MRI) began in 1999, and a radiation therapy device called 1.5 Tesla magnetic resonance linear accelerator (MR-Linac), which combines a linear accelerator with 1.5 Tesla MRI, was developed in Europe. The aim of this review is to present an overview of 1.5 Tesla MR-Linac with a review of the literature and our experience. Reports related to 1.5 Tesla MR-Linac were searched for in PubMed and are discussed in relation to our experience. The 1.5 Tesla MR-Linac enables IGRT using 1.5 Tesla MRI, further enhancing the precision of radiation therapy. Position verification by cone-beam computed tomography (CBCT) is performed in many institutions, but soft tissue contrast is often unclear in CBCT images of the abdomen and mediastinal organs. Since the 1.5 Tesla MR-Linac allows position verification using MRI, position verification can be performed using clear MRI even in regions where CBCT is unclear. With the 1.5 Tesla MR-Linac, it is possible to perform online adaptive radiotherapy (ART) using 1.5 Tesla MRI. Online ART is a method in which images are acquired while the patient is on the treatment table. The method is based on the current condition of the organs in the body on that day and an optimal treatment field is recreated. Additionally, it allows monitoring of tumor motion using cine images obtained by 1.5 Tesla MRI during the delivery of X-ray radiation. A previous report showed that patients with prostate cancer who received radiotherapy by MR-Linac had fewer side effects than those in patients who received conventional CBCT radiation therapy. The 1.5 Tesla MR-Linac obtained CE-mark certification in Europe in August 2018 and it has been used for clinical treatment. In Japan, clinical treatment using this device started in 2021. By using 1.5 Tesla MR-Linac, patients can be provided with higher precision radiotherapy. In this review, we provide an overview of 1.5 Tesla MR-Linac.

A treatment planning study to compare radiotherapy delivery techniques for glioblastoma multiforme patients

A treatment planning study to compare radiotherapy delivery techniques for glioblastoma multiforme patients

GammaTile® (GT) as a brachytherapy platform for rapidly proliferating glioblastomas: from case series to clinical trials.

Radiation plays a central role in glioblastoma treatment. Logistics related to coordinating clinic visits, radiation planning, and surgical recovery necessitate delay in radiation delivery from the time of diagnosis. Unimpeded tumor growth occurs during this period, and is associated with poor clinical outcome. Here we provide a pilot experience of GammaTile ® (GT), a collagen tile-embedded Cesium-131 (131Cs) brachytherapy platform for such aggressive tumors. We prospectively followed seven consecutive patients (2019-2023) with newly diagnosed (n = 3) or recurrent (n = 4) isocitrate dehydrogenase wild-type glioblastoma that grew > 100% in volume during the 30days between the time of initial diagnosis/surgery and the radiation planning MRI. These patients underwent re-resection followed by GT placement. There were no surgical complications. One patient developed right hemiparesis prior to re-resection/GT placement and was discharged to rehabilitation, all others were discharged home-with a median hospital stay of 2days (range: 1-5days). There was no 30-day mortality and one 30-day readmission (hydrocephalus, requiring ventriculoperitoneal shunting (14%)). With a median follow-up of 347days (11.6months), median progression free survival of ≥ 320days (10.6months) was achieved for both newly and recurrent glioblastoma patients. The median overall survival (mOS) was 304 and 347days (10 and 11.5 mo) for recurrent and newly diagnosed glioblastoma patients, respectively. Our pilot experience suggests that GT offers favorable local control and safety profile for patients afflicted with rapidly proliferating glioblastomas and lay the foundation for future clinical trial design.

Adaptive ultra-hypofractionated whole-pelvic radiotherapy in high-risk and very high-risk prostate cancer on 1.5-Tesla MR-Linac: Estimated delivered dose and early toxicity results.

Magnetic resonance (MR)-guided ultra-hypofractionated radiotherapy with whole-pelvic irradiation (UHF-WPRT) is a novel approach to radiotherapy for patients with high-risk (HR) and very high-risk (VHR) prostate cancer (PCa). However, the inherent complexity of adaptive UHF-WPRT might inevitably result in longer on-couch time. We aimed to estimate the delivered dose, study the feasibility and safety of adaptive UHF-WPRT on a 1.5-Tesla MR-Linac. Ten patients with clinical stage T3a-4N0-1M0-1c PCa, who consecutively received UHF-WPRT, were enrolled prospectively. The contours of the target and organ-at-risks on the position verification-MR (PV-MR), beam-on 3D-MR(Bn-MR), and post-MR (after radiotherapy delivery) were derived from the pre-MR data by deformable image registration. The physician then manually adjusted them, and dose recalculation was performed accordingly. GraphPad Prism 9 (GraphPad Prism Software Inc.) was utilized for conducting statistical analyses. In total, we collected 188 MR scans (50 pre-MR, 50 PV-MR, 44 Bn-MR, and 44 post-MR scans). With median 59 min, the mean prostate clinical target volume (CTV)-V100% was 98.59% ± 2.74%, and the mean pelvic CTVp-V100% relative percentages of all scans was 99.60% ± 1.18%. The median V29 Gy change in the rectal wall was -2% (-18% to 20%). With a median follow-up of 9 months, no patient had acute Common Terminology Criteria for Adverse Events (CTCAE) grade 2 or more severe genitourinary (GU) or gastrointestinal (GI) toxicities (0%). UHF-RT to the prostate and the whole pelvis with concomitant boost to positive nodes using an Adapt-To-Shape (ATS) workflow was technically feasible for patients with HR and VHR PCa, presenting only mild GU and GI toxicities. The estimated target dose during the beam-on phase was clinically acceptable based on the 3D-MR-based dosimetry analysis. Chinese Clinical Trial Registry ChiCTR2000033382.

Beam control system and output fine-tuning for safe and precise delivery of FLASH radiotherapy at a clinical linear accelerator.

We have previously adapted a clinical linear accelerator (Elekta Precise, Elekta AB) for ultra-high dose rate (UHDR) electron delivery. To enhance reliability in future clinical FLASH radiotherapy trials, the aim of this study was to introduce and evaluate an upgraded beam control system and beam tuning process for safe and precise UHDR delivery. The beam control system is designed to interrupt the beam based on 1) a preset number of monitor units (MUs) measured by a monitor detector, 2) a preset number of pulses measured by a pulse-counting diode, or 3) a preset delivery time. For UHDR delivery, an optocoupler facilitates external control of the accelerator's thyratron trigger pulses. A beam tuning process was established to maximize the output. We assessed the stability of the delivery, and the independent interruption capabilities of the three systems (monitor detector, pulse counter, and timer). Additionally, we explored a novel approach to enhance dosimetric precision in the delivery by synchronizing the trigger pulse with the charging cycle of the pulse forming network (PFN). Improved beam tuning of gun current and magnetron frequency resulted in average dose rates at the dose maximum at isocenter distance of >160 Gy/s or >200 Gy/s, with or without an external monitor chamber in the beam path, respectively. The delivery showed a good repeatability (standard deviation (SD) in total film dose of 2.2%) and reproducibility (SD in film dose of 2.6%). The estimated variation in DPP resulted in an SD of 1.7%. The output in the initial pulse depended on the PFN delay time. Over the course of 50 measurements employing PFN synchronization, the absolute percentage error between the delivered number of MUs calculated by the monitor detector and the preset MUs was 0.8 ± 0.6% (mean ± SD). We present an upgraded beam control system and beam tuning process for safe and stable UHDR electron delivery of hundreds of Gy/s at isocenter distance at a clinical linac. The system can interrupt the beam based on monitor units and utilize PFN synchronization for improved dosimetric precision in the dose delivery, representing an important advancement toward reliable clinical FLASH trials.

Embracing Personalized Strategies in Radiotherapy for Nasopharyngeal Carcinoma: Beyond the Conventional Bounds of Fields and Borders.

Radiotherapy is the primary treatment modality for non-metastatic nasopharyngeal carcinoma (NPC) across all TN-stages. Locoregional control rates have been impressive even from the 2D radiotherapy (RT) era, except when the ability to deliver optimal dose coverage to the tumor is compromised. However, short- and long-term complications following head and neck RT are potentially debilitating, and thus, there has been much research investigating technological advances in RT delivery over the past decades, with the primary goal of limiting normal tissue damage. On this note, with a plateau in gains of therapeutic ratio by modern RT techniques, future advances have to be focused on individualization of RT, both in terms of dose prescription and the delineation of target volumes. In this review, we analyzed the guidelines and evidence related to contouring methods, and dose prescription for early and locoregionally advanced (LA-) NPC. Next, with the preference for induction chemotherapy (IC) in patients with LA-NPC, we assessed the evidence concerning radiotherapy adaptations guided by IC response, as well as functional imaging and contour changes during treatment. Finally, we discussed on RT individualization that is guided by EBV DNA assessment, and its importance in the era of combinatorial immune checkpoint blockade therapy with RT.

Abstract A005: A multi-institutional randomized phase III trial of chemotherapy alone versus chemotherapy and ablative 5-fraction MRI-guided adaptive radiation therapy for locally advanced pancreatic cancer (LAP-ABLATE)

Abstract Background: Prospective studies demonstrate that chemotherapy and non-ablative radiation therapy (RT) achieve superior locoregional control (LRC) although have not improved overall survival (OS) relative to chemotherapy alone for patients with locally advanced pancreatic cancer (LAPC). Emerging data suggest that significant radiation dose escalation may further enhance LRC, and it has been hypothesized that in a subset of patients this may improve OS. However, delivering ablative radiation dose in 5 or fewer fractions with computerized tomography (CT) guidance is associated with unacceptable rates of grade 3-5 toxicity. Safe dose escalation can be facilitated by radiation delivery systems that utilize magnetic resonance image (MRI) guidance and on-table adaptive replanning. A growing body of literature describes promising efficacy and safety of ablative 5-fraction stereotactic MRI-guided adaptive radiation therapy (SMART) for LAPC compared to historical non-ablative outcomes. Based on these encouraging results, the LAP-ABLATE trial has been designed to test the hypothesis that ablative SMART improves OS. Methods: The LAP-ABLATE trial is a multi-institutional group sequential randomized phase III study for patients with LAPC. Patients are eligible after first receiving 4-6 months of (modified)FOLFIRINOX or gemcitabine/nab-paclitaxel with either stable or responding disease. Other key eligibility criteria include CA 19-9 &amp;lt;180 U/mL and no contraindication to undergoing MRI scans. Patients are randomized (1:2) to receiving no ablative SMART (arm A) versus ablative SMART (arm B), with subsequent systemic therapy or surgery being optional in both arms. Ablative SMART will be delivered using the MRIdian Linac, a 0.35 Tesla MRI-guided linear accelerator. The prescribed dose is 50 Gy to gross disease and 33 Gy to elective regions in 5 fractions using a simultaneous integrated boost (SIB). The primary objective is to compare 2-year OS with secondary objectives including assessment of LRC, distant metastasis free survival (DMFS), progression-free survival (PFS), quality of life (QOL), and toxicity. Randomization will be stratified by participating center, baseline CA 19-9 level and induction chemotherapy regimen. Target accrual is 267 patients (arm A: 89, arm B: 178). Discussion: The LAP-ABLATE trial is the first prospective randomized phase III study designed to compare OS in LAPC patients following induction systemic therapy randomized to with or without ablative 5-fraction RT. Citation Format: Michael D. Chuong, Jessica M. Frakes, Kathryn E. Mittauer, James Good, Josh Kim, Daniel Chang, Dae Won Kim, Stefanie Corradini, Luca Boldrini, Mokenge Malafa, Eileen O'Reilly. A multi-institutional randomized phase III trial of chemotherapy alone versus chemotherapy and ablative 5-fraction MRI-guided adaptive radiation therapy for locally advanced pancreatic cancer (LAP-ABLATE) [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A005.

Effects of respiratory motion on accurate four-dimensional computed tomography acquisition and plan delivery for lung stereotactic body radiation therapy

AbstractThis study evaluated the impact of respiratory movement on four-dimensional computed tomography (4D-CT) acquisition and radiotherapy delivery. QUASAR™ Respiratory Motion Phantom with nine sinusoidal waveforms that combined three amplitudes (10, 20, and 30 mm) and three breaths per minute (BPMs) (10, 15, and 20) was used. We acquired 4D-CT for nine respective waveforms and measured and compared geometrical factors (volume, shape, and motion) to reference static CT. We optimized and delivered radiotherapy plans on a Vital Beam and evaluated gamma for dose distribution analysis with three acceptance criteria: 3%/3 mm, 3%/3 mm, and 5%/5 mm. Geometrical analysis revealed that an increase in amplitude decreased 4D-CT acquisition accuracy. Geometrical factors for an amplitude of ≤ 20 mm were within tolerance limits, however, amplitude 30 mm resulted in significant deviations over tolerance limits. BPM had a minimal effect on geometrical accuracy when accurate pitch values for respective BPMs were selected for scanning. Dose distribution analysis also indicated that an increase in amplitude decreased the gamma passing rates. Amplitude 30 mm failed to achieve a 95% passing rate for all three gamma evaluation criteria adopted in the present study. Overall, our results demonstrate that respiratory motion has significant effects on the accuracy of both 4D-CT acquisition and planned radiotherapy delivery. Small amplitude of ≤ 20 mm is required to ensure accuracy.

Simulating an intra-fraction adaptive workflow to enable PTV margin reduction in MRIgART volumetric modulated arc therapy for prostate SBRT.

This study simulates a novel prostate SBRT intra-fraction re-optimization workflow in MRIgART to account for prostate intra-fraction motion and evaluates the dosimetric benefit of reducing PTV margins. VMAT prostate SBRT treatment plans were created for 10 patients using two different PTV margins, one with a 5 mm margin except 3 mm posteriorly (standard) and another using uniform 2 mm margins (reduced). All plans were prescribed to 36.25 Gy in 5 fractions and adapted onto each daily MRI dataset. An intra-fraction adaptive workflow was simulated for the reduced margin group by synchronizing the radiation delivery with target position from cine MRI imaging. Intra-fraction delivered dose was reconstructed and prostate DVH metrics were evaluated under three conditions for the reduced margin plans: Without motion compensation (no-adapt), with a single adapt prior to treatment (ATP), and lastly for intra-fraction re-optimization during delivery (intra). Bladder and rectum DVH metrics were compared between the standard and reduced margin plans. As expected, rectum V18 Gy was reduced by 4.4 ± 3.9%, D1cc was reduced by 12.2 ± 6.8% (3.4 ± 2.3 Gy), while bladder reductions were 7.8 ± 5.6% for V18 Gy, and 9.6 ± 7.3% (3.4 ± 2.5 Gy) for D1cc for the reduced margin reference plans compared to the standard PTV margin. For the intrafraction replanning approach, average intra-fraction optimization times were 40.0 ± 2.9 seconds, less than the time to deliver one of the four VMAT arcs (104.4 ± 9.3 seconds) used for treatment delivery. When accounting for intra-fraction motion, prostate V36.25 Gy was on average 96.5 ± 4.0%, 99.1 ± 1.3%, and 99.6 ± 0.4 for the non-adapt, ATP, and intra-adapt groups, respectively. The minimum dose received by the prostate was less than 95% of the prescription dose in 84%, 36%, and 10% of fractions, for the non-adapt, ATP, and intra-adapt groups, respectively. Intra-fraction re-optimization improves prostate coverage, specifically the minimum dose to the prostate, and enables PTV margin reduction and subsequent OAR sparing. Fast re-optimizations enable uninterrupted treatment delivery.

HypoFocal SRT Trial: Ultra-hypofractionated focal salvage radiotherapy for isolated prostate bed recurrence after radical prostatectomy; single-arm phase II study; clinical trial protocol

IntroductionDespite radical prostatectomy (RP) and radiotherapy (RT) being established treatments for localised prostate cancer, a significant number of patients experience recurrent disease. While conventionally fractionated RT is still being used...

Current Perspectives on Proton Therapy: Techniques Shaping the Future of Cancer Treatment

Traditional Radiation Therapy (RT) predominantly comprises a targeted therapeutic strategy focused on improving localised tumour control and achieving a cure while minimising the occurrence of adverse side effects. It could be feasible to take advantage of the better dose distribution by enabling larger RT dosages to the malignancy while preventing a rise in the toxicity of RT-induced healthy tissue, or by reducing adverse reactions to manageable levels. Poor local disease control and important dose-limiting normal tissue, which prevent safe dosage increase with conventional photon RT, have been the key justifications for RT. Proton treatment, on the other hand, delivers therapeutic protons or positive particles using proton beams. The potential advantage of protons’ physical properties allows for more localised RT delivery. By increasing the dosage to equitoxic levels, it is also possible to take advantage of the potential improvement in normal tissue sparing to support local tumour management and, ideally, longevity. Proton treatment preserves more important structures than photon therapy because of its unique physics. Thus, there is a need for wide usage of Proton Therapy (PT) for successive cancer treatment. The present review focuses on PT based on tumour site, clinical studies, biological barriers, instrumentation of PT, significance, and limitations.

2V-CBCT: Two-Orthogonal-Projection based CBCT Reconstruction and Dose Calculation for Radiation Therapy using Real Projection Data.

This work demonstrates the feasibility of two-orthogonal-projection-based CBCT (2V-CBCT) reconstruction and dose calculation for radiation therapy (RT) using real projection data, which is the first 2V-CBCT feasibility study with real projection data, to the best of our knowledge. RT treatments are often delivered in multiple fractions, for which on-board CBCT is desirable to calculate the delivered dose per fraction for the purpose of RT delivery quality assurance and adaptive RT. However, not all RT treatments/fractions have CBCT acquired, but two orthogonal projections are always available. The question to be addressed in this work is the feasibility of 2V-CBCT for the purpose of RT dose calculation. 2V-CBCT is a severely ill-posed inverse problem for which we propose a coarse-to-fine learning strategy. First, a 3D deep neural network that can extract and exploit the inter-slice and intra-slice information is adopted to predict the initial 3D volumes. Then, a 2D deep neural network is utilized to fine-tune the initial 3D volumes slice-by-slice. During the fine-tuning stage, a perceptual loss based on multi-frequency features is employed to enhance the image reconstruction. Dose calculation results from both photon and proton RT demonstrate that 2V-CBCT provides comparable accuracy with full-view CBCT based on real projection data.

Dosimetric effect of rotational setup errors in volumetric modulated arc therapy and field-in-field treatment of left-sided breast cancer

Setup errors are an important factor in the dosimetric accuracy of radiotherapy delivery. In this study, we investigated how rotational setup errors influence the dose distribution in volumetric modulated arc therapy (VMAT) and tangential field-in-field (FiF) treatment of left-sided breast cancer with supraclavicular lymph node involvement in deep inspiration breath hold. Treatment planning computed tomography images and radiotherapy plans of 20 patients were collected retrospectively for the study. Rotational setup errors up to 3° were simulated by rotating the planning images, and the resulting dosimetric changes were calculated. With rotational setup errors up to 3°, the median decrease of V95% to clinical target volume was less than 0.8 percentage point in both VMAT and FiF plans. The dose distribution of the heart and left anterior descending artery was more stable with respect to rotations in VMAT plans compared to FiF plans. Correction of ≥1° setup errors is recommended due to increased doses to the heart and left anterior descending artery after 1° setup errors.

ANALYSIS OF THE PRODUCTION OF RARE-EARTH ISOTOPES AT THE WWR-K RESEARCH REACTOR: PROMISING THERAPEUTIC RADIONUCLIDES

Rare Earth Elements (REE) are a group of seventeen chemical elements in the periodic table, including lanthanides and scandium and yttrium. These elements have unique physical and chemical properties that make them valuable in various industries, including electronics, magnets, and catalysts. However, radioactive isotopes of rare earth elements also possess effective nuclear physical properties that make them promising for the development of new radiopharmaceuticals for therapeutic purposes. These radioactive isotopes have unstable atoms with excess nuclear energy, and they undergo radioactive decay, which can be utilized for medical applications.The nuclear physical properties of radioactive isotopes of rare earth elements make them suitable for therapeutic purposes in medicine. For example, technetium-99m, a radioactive isotope of technetium, is widely used in diagnostic nuclear medicine due to its outstanding physical-chemical characteristics. Other radioactive isotopes of rare earth elements, such as holmium-166, have been established for a broad spectrum of medical applications. These isotopes can be used in targeted radiation therapy to treat various diseases, including cancer. The unique properties of these radioactive isotopes allow for precise targeting and delivery of radiation to specific tissues or cells, minimizing damage to healthy tissues.The potential of radioactive isotopes of rare earth elements for therapeutic purposes extends beyond the current applications. Ongoing research and innovations in the field of radiopharmaceuticals continue to explore the use of underutilized lanthanoid radionuclides for theranostic purposes. For example, astatine, a rare and highly radioactive element, exhibits multiple isotopes that can be potentially utilized in targeted therapy. The development of new radiopharmaceuticals using radioactive isotopes of rare earth elements holds promise for advancing medical treatments and improving patient outcomes. With further research and advancements, these isotopes may play a crucial role in the future of therapeutic medicine.This research work makes it possible to evaluate the possibility of obtaining REE such radioisotopes as: 90Y, 141Ce, 147Nd, 153Sm, 165Dy, 166Ho, 169Tm, 175Yb, 177Yb, 177Lu by reaction (n, γ) at the WWR-K reactor.

ACR-ARS Practice Parameter for Radiation Oncology.

This practice parameter was revised collaboratively by the American College of Radiology (ACR), and the American Radium Society. This practice parameter provides updated reference literature regarding radiation oncology practice and its key personnel. This practice parameter was developed according to the process described under the heading The Process for Developing ACR Practice Parameters and Technical Standards on the ACR website ( https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards ) by the Committee on Practice Parameters-Radiation Oncology of the ACR Commission on Radiation Oncology in collaboration with the American Radium Society. This practice parameter provides a comprehensive update to the reference literature regarding radiation oncology practice in general. The overall roles of the radiation oncologist, the Qualified Medical Physicist, and other specialized personnel involved in the delivery of external-beam radiation therapy are discussed. The use of radiation therapy requires detailed attention to equipment, patient and personnel safety, equipment maintenance and quality assurance, and continuing staff education. Because the practice of radiation oncology occurs in a variety of clinical environments, the judgment of a qualified radiation oncologist should be used to apply these practice parameters to individual practices. Radiation oncologists should follow the guiding principle of limiting radiation exposure to patients and personnel while accomplishing therapeutic goals. This practice parameter can be used as an effective tool to guide radiation oncology practice by successfully incorporating the close interaction and coordination among radiation oncologists, medical physicists, dosimetrists, nurses, and radiation therapists.

Impact of Maximum Point Dose Within the Planning Target Volume on Local Control of Nonsmall Cell Lung Cancer Treated With Stereotactic Body Radiotherapy.

No consensus exists on the maximum dose delivered to the planning target volume (PTV) in the delivery of stereotactic body radiotherapy (SBRT) for primary lung cancer. We investigated whether higher biologically effective doses (BED) within the PTV were associated with improved tumor control. We reviewed patients with early-stage, node-negative nonsmall cell lung cancer who received curative-intent SBRT between 2005 and 2018. We calculated the maximum BED (maxBED) within the PTV for all patients, analyzing outcomes using the cumulative incidence method and Fine-Gray test statistics to assess prognostic impact. We analyzed 171 patients (median age, 70.2; range, 43 to 90y) with 181 lung nodules. Median follow-up was 2.7 years (range, 0.1 to 12y) for all patients and 4.2 years (range, 0.2 to 8.4y) for living patients. Median maximum tumor diameter was 1.9cm (range, 0.7 to 5.6cm). Patients received a prescription of 48 or 50 Gy in 4 or 5 fractions, respectively, except for one who received 60 Gy in 5 fractions. Median maxBED was 120 Gy (range, 101 to 171 Gy). There was no difference in the 3-year local control (LC) rate among patients treated with a maxBED<120 Gy versus ≥120 Gy ( P =0.83). No significant differences in LC were observed between patients with early-stage nonsmall cell lung cancer treated with SBRT in 4 or 5 fractions with a maxBED≥120 Gy. However, a higher maxBED trended toward improved LC rates, suggesting a maxBED threshold greater than 120 Gy may be needed to improve LC rates.

Incidence and survival of secondary malignancies after external beam radiotherapy for prostate cancer in the SEER database.

We investigated the incidence of secondary bladder (BCa) and rectal cancers (RCa) after external beam radiotherapy (EBRT) for prostate cancer (PCa) compared to radical prostatectomy (RP) alone, and compared cancer-specific survival (CSS) of these secondary neoplasms to their primary counterparts. This retrospective cohort study included men in the SEER cancer registry with a diagnosis of non-metastatic, clinically node-negative PCa treated with either RP or EBRT from 1995-2011 and allowed a minimum five-year lag period for the development of secondary BCa or RCa. Patients were divided into two eras, 1995-2002 and 2003-2011, to examine differences in incidence of secondary malignancies over time. Univariable and multivariable competing risk analyses with Fine-Gray subdistribution hazard and cause-specific hazard models were used to examine the risk of developing a secondary BCa or RCa. Competing risks analyses were used to compare CSS of primary vs. secondary BCa and RCa. A total of 198 184 men underwent RP and 190 536 underwent EBRT for PCa. The cumulative incidence of secondary BCa at 10 years was 1.71% for RP, and 3.7% for EBRT (p<0.001), while that of RCa was 0.52% for RP and 0.99% for EBRT (p<0.001). EBRT was associated with almost twice the risk of developing a secondary BCa and RCa compared to RP. The hazard of secondary BCa following EBRT delivered during 2003-2011 was 20% less than from 1995-2002 (p<0.09, Fine-Gray model), while that of secondary RCa was 31% less (p<0.001) (hazard ratio 0.78, p<0.001) for Fine-Gray and cause-specific hazard models. In the Fine-Gray model, the risk of death from BCa was 27% lower for secondary BCa after RP compared to primary BCa, while the risk of death was 9% lower for secondary BCa after EBRT compared to primary BCa. There was no difference in RCa-specific survival between primary or secondary RCa after RP or EBRT. The risk of BCa and RCa is almost twice as high for men undergoing EBRT for localized PCa vs. RP, but that risk is declining, likely reflecting advances in radiation delivery. The development of secondary RCa or BCa does not confer elevated risk of death compared to their primary counterparts.