Background The use of the deep inspiration breath-hold (DIBH) technique reduces cardiac and lung radiation exposure during left breast cancer radiotherapy. However, the optimal beam delivery technique and the effects of patient adaptation during DIBH remain incompletely understood. Objective In this study, the dosimetric differences between continuous semi-arc and tangent-arc plans in stage I left-sided breast cancer patients using DIBH were compared, and the treatment session duration was descriptively analyzed to characterize treatment-time trends during routine DIBH delivery. Methods Twenty patients treated at our hospital from 01/05/2022-31/05/2023 were retrospectively selected from the institutional database for exploratory dosimetric analysis. Two radiotherapy plans were created on the basis of each patient's computed tomography (CT) images. Dosimetric parameters for the planning target volume (PTV) and organs at risk (OARs), and beam-on and total treatment times, were compared. Results The conformity index (CI) for the PTV was significantly better with the continuous semi-arc plan (P < 0.05), whereas the other PTV parameters did not significantly differ between the plans (P > 0.05). The doses and beam-on time for all OARs (except the left ventricle) were significantly lower for the tangent-arc plan (P < 0.05). Treatment time tended to stabilize across fractions, with a significant difference between the 15th and 16th sessions (P < 0.05). Conclusion With the tangent-arc plan, the beam-on time and radiation exposure to OARs were observed to be lower, while adequate PTV coverage was maintained in patients with stage I left-sided breast cancer using DIBH. Treatment times tended to stabilize with increasing treatment fractions. This observation suggests gradual patient adaptation during routine DIBH rather than a predefined training effect. Given the exploratory nature of these findings and the limited sample size from a single institution, these findings should be interpreted with caution and warrant further investigation in larger, multicenter studies.

When RayStation is used for Halcyon treatment planning and the plan is transferred to the ARIA/Eclipse system for delivery verification, the dose must be recalculated using the Anisotropic Analytical Algorithm (AAA) or AcurosXB algorithm for compatibility. This study evaluated the dosimetric differences among the Collapsed Cone (CC), AAA, and AcurosXB algorithms for non-small cell lung cancer (NSCLC) volumetric modulated arc therapy (VMAT) plans on the Halcyon platform. Treatment plans for 60 lung cancer patients were initially generated using the CC algorithm in RayStation and then recalculated in Eclipse using AAA and AcurosXB without re-optimization or renormalization. Systematic variations were observed among the three algorithms. AcurosXB showed the largest reductions in target doses compared with CC (up to a 1.56% reduction in clinical target volume (CTV) D2%), while AAA demonstrated smaller differences. For planning target volume (PTV) metrics, both AAA and AcurosXB yielded lower doses than CC (AAA up to 2.16% in D95%; AcurosXB up to 1.58% in D2%). All variations in CTV and PTV metrics remained within approximately 1.7%. For organ-at-risk doses, AAA produced slightly lower values than CC, whereas AcurosXB yielded consistently lower doses across most parameters. Overall, this study shows that AAA and AcurosXB provide slightly lower dose estimates than CC for the same Halcyon plan, especially for PTV and organ-at-risk metrics. These results highlight the importance of consistent dose-calculation methodology in NSCLC radiotherapy, particularly in cross-platform workflows between RayStation and Eclipse.

This study was conducted to develop and validate a novel deep reinforcement learning (DRL) algorithm incorporating the segment anything model (SAM) to enhance the accuracy of automatic contouring organs at risk during radiotherapy for cervical cancer patients. CT images were collected from 150 cervical cancer patients treated at our hospital between 2021 and 2023. Among these images, 122 CT images were used as a training set for the algorithm training of the DRL model based on the SAM model, and 28 CT images were used for the test set. The model’s performance was evaluated by comparing its segmentation results with the ground truth (manual contouring) obtained through manual contouring by expert clinicians. The test results were compared with the contouring results of commercial automatic contouring software based on the deep learning (DL) algorithm model. The Dice similarity coefficient (DSC), 95th percentile Hausdorff distance, average symmetric surface distance (ASSD), and relative absolute volume difference (RAVD) were used to quantitatively assess the contouring accuracy from different perspectives, enabling the contouring results to be comprehensively and objectively evaluated. The DRL model outperformed the DL model across all evaluated metrics. DRL achieved higher median DSC values, such as 0.97 versus 0.96 for the left kidney (P < 0.001), and demonstrated better boundary accuracy with lower HD95 values, e.g., 14.30 mm versus 17.24 mm for the rectum (P < 0.001). Moreover, DRL exhibited superior spatial agreement (median ASSD: 1.55 mm vs. 1.80 mm for the rectum, P < 0.001) and volume prediction accuracy (median RAVD: 10.25 vs. 10.64 for the duodenum, P < 0.001). These findings indicate that integrating SAM with RL (reinforcement learning) enhances segmentation accuracy and consistency compared to conventional DL methods. The proposed approach introduces a novel training strategy that improves performance without increasing model complexity, demonstrating its potential applicability in clinical practice.

This study evaluates the differences in application of the RayStation Monte Carlo algorithm (RMC) compared to Acuros XB (AXB) and the Anisotropic Analytical Algorithm (AAA) in Eclipse for conventional radiotherapy planning of lung cancer using the novel ring-shaped Halcyon accelerator. A total of 63 non-small-cell lung cancer patients were retrospectively included, with a prescription dose of 60 Gy delivered in 30 fractions. Radiotherapy plans were initially designed and optimized in RayStation, then recalculated in Eclipse using AXB and AAA to assess algorithmic differences in dose distributions. Analysis of data from 63 patients, combined with simulations using square fields and cylindrical water phantoms, revealed that RMC and AXB achieved high consistency in target dose coverage and conformity. High-dose indicators, such as D2% and D0.03cc, showed close agreement between RMC and AAA, while AXB tended to slightly underestimate peak doses. For prescription dose coverage metrics like D95% and D98%, the difference between RMC and AXB was less than 1%, whereas AAA exhibited minor degradation. In organ-at-risk dose evaluations, RMC delivered higher doses compared to AXB and AAA, with AAA doses exceeding those of AXB. These findings confirm the dose consistency of RayStation and Eclipse algorithms for use with the Halcyon accelerator. The RayStation Monte Carlo algorithm (RMC) is a viable alternative to AXB, especially in lung cancer cases with high tissue heterogeneity, as target coverage and conformity discrepancies remain within 0.5%. Additionally, recalculation of RMC-optimized plans in Eclipse using AXB resulted in lower organ-at-risk doses. Therefore, recalculations performed before treatment do not compromise the clinical adequacy of volumetric dose evaluations.

This study compared the plan quality and execution efficiency of VMAT plans using TrueBeam single-isocenter and Halcyon dual-isocenter systems for postoperative left-sided breast cancer, providing evidence for the selection and application of radiotherapy methods after breast cancer surgery. Twenty postoperative left-sided breast cancer patients treated at Zhejiang Cancer Hospital from January 2020 to August 2022 were included in the study. Using the RayStation 9 A system, TrueBeam single-isocenter (T group) and Halcyon dual-isocenter (H group) VMAT plans were created. The study compared PTV (Planning Target Volume) conformity index (CI), homogeneity index (HI), mean and maximum doses, dose to organs at risk (OAR), monitor units (MU), beam-on time, and plan complexity between the groups. Both groups’ plans met clinical objectives with good dose distribution and target coverage. Significant statistical differences were observed in the PTV maximum dose (Dmax), mean dose (Dmean), and D50 between the two groups (P < 0.05), with the H group outperforming the T group. There was no statistically significant difference in CI and HI between the two groups (P > 0.05). The OAR doses were lower in the H group compared to the T group, with significant statistical differences observed in heart Dmean, left lung (Dmean, V5, V20, V30), lungs (Dmean, V5, V20, V30), and humeral head Dmax (P < 0.05), and there was no statistically significant difference in heart (V30, V40), spinal cord Dmax, and right breast Dmean (P < 0.05). In terms of plan quality assessment, the total MU for the H group was significantly higher (1066.704 ± 135.183) than that for the T group (772.992 ± 104.023), with extremely significant statistical differences (P < 0.01). The beam-on time for the H group was significantly longer (101.328 ± 9.359 s) than that for the T group (53.535 ± 12.655 s), with extremely significant statistical differences (P < 0.01). The plan complexity for the H group was significantly higher (0.101 ± 0.009 cm−1) than that for the T group (0.068 ± 0.009 cm−1), with extremely significant statistical differences (P < 0.01). The study found that Halcyon dual-isocenter VMAT plans offered better PTV uniformity and coverage while protecting OARs more effectively. Despite higher MU, beam-on time, and plan complexity, the H group’s dosimetric advantages and reduced manual positioning errors make it a safe and effective treatment option for postoperative breast cancer.

This study evaluated setup error and efficiency in patients with non-small cell lung cancer (NSCLC) receiving stereotactic body radiation therapy (SBRT), comparing surface-guided radiation therapy (SGRT) combined with a laser alignment system versus laser alignment alone, to assess the clinical value of the SGRT-assisted setup method in SBRT for NSCLC. A total of 80 patients with NSCLC were divided into an experimental group and a control group according to the treatment setup method. In the experimental group, an integrated fixation platform, vacuum cushions, and a cervicothoracic thermoplastic mask were used for immobilization, and a SGRT system and laser alignment system were used for setup. In the control group, the same immobilization devices were used, but only a laser alignment system was used for setup. All patients underwent pretreatment cone‒beam computed tomography (CBCT) scans. The CBCT images were registered to planning computed tomography (CT) images using grayscale registration. Translational setup errors in the left–right (LR), superior–inferior (SI), and anterior–posterior (AP) directions and rotational errors in the pitch, roll, and rotation directions were recorded. The setup time was also recorded and compared between the groups. Significant differences in the overall mean setup error in all six degrees of freedom were observed between the experimental and control groups (P ≤ 0.001). Within the experimental group, the overall mean setup error differed significantly between the LR and SI directions (P = 0.006). Within the control group, significant differences were found between the SI and AP directions (P < 0.001), as well as between pitch and rotation (P = 0.001) and between roll and rotation (P < 0.001). The overall mean setup time also significantly differed between the two groups (P < 0.001). Compared with the conventional laser-guided setup method, the combination of SGRT and a laser alignment system significantly reduced setup error and shortened the setup time in SBRT for NSCLC. This approach improves setup accuracy and treatment workflow efficiency, demonstrating clinical feasibility and potential for clinical application.

Objective The dosimetric characteristics and treatment efficiency of VMAT plans using two linear accelerator platforms, Halcyon and Infinity, in conventional radiotherapy for non-small cell lung cancer (NSCLC) are compared to provide data for selecting clinical equipment. The study also explores potential confounding factors that may influence treatment outcomes. Methods This retrospective cohort study aims to compare the dosimetric characteristics and treatment efficiency of VMAT plans delivered using Halcyon and Infinity linear accelerator platforms in patients with NSCLC. A retrospective analysis was performed on 60 NSCLC patients receiving conventional fractionated radiotherapy with VMAT plans developed for both Halcyon and Infinity. These plans were optimized with RayStation 9A with identical dose constraints and optimization parameters. The groups were compared in terms of target dose coverage, normal tissue sparing, plan complexity, and treatment efficiency. The dosimetric parameters included D98%, D2%, and Dmean for both the CTV and PTV and dose distributions for organs at risk (OARs), including the heart, lungs, and spinal cord. Logistic regression was performed to account for potential confounding factors, such as PTV volume, tumor stage, and tumor location. Results The VMAT plans of both platforms met the clinical dosimetric requirements. Halcyon showed superior protection of normal tissues in low-dose areas (e.g., Lungs V5Gy and Heart V30Gy), whereas Infinity excelled in controlling hot spots and achieving rapid dose fall-off at the target margins. Furthermore, Halcyon has fewer plan monitoring units and lower complexity than Infinity and reduced treatment time by 24.0%. Logistic regression analysis revealed that PTV volume was a significant predictor for dose metric differences, while tumor stage and tumor location had variable effects depending on the dose metric, highlighting the need to account for these factors in clinical comparisons. Overall, there was no significant difference in target dose coverage or uniformity between the platforms; each demonstrated specific strengths in protecting different OARs and in treatment execution efficiency. Conclusion Halcyon and Infinity offer distinct advantages in radiotherapy for NSCLC. Halcyon provides better protection of normal tissues and performance in low-dose regions, whereas Infinity offers greater treatment efficiency and superior control in high-dose regions. The study also highlights that PTV volume is an important factor influencing dosimetric outcomes. In choosing optimal radiotherapy equipment in clinical practice, the study results suggest that treatment planning should leverage the unique technical features of different accelerators to achieve the best individualized outcomes. Future studies should increase the sample size and employ prospective research designs to confirm the clinical relevance of these findings.

OBJECTIVE:Recurrent and metastatic tumors of the head and neck pose significant treatment challenges due to their proximity to critical structures and prior radiation exposure. This study aimed to evaluate the consistency between preoperative and postoperative dosimetric parameters in CT-guided 3D-printed noncoplanar template (3DPNCT)-assisted radioactive iodine-125 seed implantation (RISI). METHODS:Twenty-six patients with recurrent or metastatic head and neck cancer were retrospectively analyzed. Gross tumor volume (GTV) coverage and dosimetric parameters such as D90 (dose covering 90% of the GTV), conformity index (CI), and homogeneity index (HI) were compared before and after implantation. The Shapiro-Wilk test was used to assess data normality. RESULTS:There were no significant differences between pre- and postoperative D90, V100, V150, or CI values (P > 0.05). Bland-Altman analysis showed high agreement for key metrics. CONCLUSIONS:3DPNCT-assisted RISI demonstrated accurate dose delivery and high reproducibility. This approach may enhance local control while minimizing radiation to organs at risk in complex head and neck anatomies. These results suggest that this technique has promising clinical applicability in complex head and neck cases; however, further validation through larger prospective studies is warranted to confirm long-term efficacy and safety.

This study aims to evaluate the feasibility of using RayStation’s scripting function to generate automated radiotherapy plans for non-small cell lung cancer (NSCLC) patients on a Varian Halcyon accelerator and to compare their dosimetric characteristics with those of retrospectively collected manual clinical plans. A total of 63 conventional fractionation plans for NSCLC, previously designed using RayStation 4.5 for a variety of linear accelerators—including Trilogy, TrueBeam, Halcyon, and Elekta Infinity—were compared with automated plans generated using RayStation 9.0 for Halcyon. This heterogeneous control group was chosen to reflect real-world clinical practice across multiple platforms. Target coverage, doses to organs at risk (OARs), monitor units, and plan complexity were assessed. The automated plans showed improved dose conformity and lower OAR exposure under the planning configuration used. However, these differences should be interpreted with caution, as the comparison involved different treatment planning systems (TPS) versions and hardware platforms. Further controlled studies using the same TPS and linac are needed to validate the observed improvements.

Respiratory-induced tumor motion is a major obstacle in the precise delivery of stereotactic body radiotherapy (SBRT) for lung cancer, often leading to geometric uncertainties, insufficient tumor coverage and increased radiation-induced toxicity such as pneumonitis, esophagitis and rib fractures. The present review systematically assesses motion management techniques used in lung SBRT, synthesizing evidence from 352 high-quality clinical studies published between 2000 and 2024. Selected studies included patients with non-small cell lung cancer treated exclusively with SBRT which incorporated strategies such as deep inspiration breath-hold, abdominal compression, respiratory gating and real-time tumor tracking, and often integrated with image guidance technologies such as 4DCT, cone beam CT and MRI. These techniques demonstrated notable reductions in planning target volume margins and normal tissue dose, leading to improved local control and lower toxicity rates, particularly in tumors with large motion amplitudes or proximity to critical structures. Despite these benefits, implementation remains variable due to patient-specific challenges, technical complexity and institutional resource differences. The present review highlights the clinical applications and limitations of each strategy, and proposes a decision-making framework to guide clinicians in selecting the most appropriate motion management strategy based on tumor characteristics, motion amplitude and patient-specific factors. The integration of respiratory motion management with advanced imaging is essential for optimizing therapeutic outcomes and safety in lung SBRT.

Background and Objective:In stereotactic body radiotherapy (SBRT) for lung cancer, the choice of volumetric modulated arc therapy (VMAT) optimization strategy is critical for achieving optimal target dose coverage while minimizing exposure to normal tissues. This study aims to compare the dosimetric performance and plan complexity of two VMAT optimization strategies in Monaco: single-beam dual-arc (1B2A) versus dual-beam single-arc (2B1A). Methods:A retrospective analysis was conducted on 50 lung cancer patients treated with SBRT (prescription dose: 50 Gy in 5 fractions). Two VMAT plans were re-optimized using the Monaco treatment planning system: the 1B2A plan (single-beam dual-arc, collimator angle 10°) and the 2B1A plan (dual-beam single-arc, collimator angles 10° and 350°). Dosimetric parameters, including target dose coverage, conformity index (CI), and gradient index (GI), were evaluated for the internal target volume (ITV) and planning target volume (PTV). Dose metrics for organs at risk (OARs) were also analyzed. Plan complexity was assessed based on monitor units (MU), number of control points, complexity index, and integral dose to normal tissues. Results:Significant dosimetric differences were observed between the two strategies. When normalized to ensure the prescribed 50 Gy isodose line covers 95% of the PTV volume, the high-dose parameters (D1%, D50%, Dmean) of the ITV and PTV were significantly lower in the 1B2A group compared to the 2B1A group (p < 0.001), indicating superior dose distribution with the 2B1A approach. Although the 1B2A plan exhibited marginally better CI, GI, and low-dose lung sparing (V5-V30), these differences were minimal and clinically insignicant. No substantial dierences were found in the dose sparing of other OARs, including the spinal cord, heart, and ribs. Additionally, the 1B2A plan required signicantly higher MU (+15.5%, p < 0.001) and had greater plan complexity (+9.47%, p < 0.001), suggesting lower treatment efficiency. Conclusions:In peripheral lung cancer SBRT, the dual-beam single-arc (2B1A) strategy offers superior target dose distribution and treatment efficiency, making it a preferable optimization approach.

Introduction Radiotherapy (RT) is the main treatment for patients with nasopharyngeal carcinoma (NPC). NPC patients at different stages have varying levels of damage to normal brain tissue after RT. No study has yet thoroughly analyzed the variations in radiation dosages in the brain for different stages of NPC patients treated with RT. This study aims to examine these variations. Methods 1446 NPC patients’ CT and RTdose data were retrospectively reviewed. Analysis of the radiation dosage was executed on these 803 patients. The RTdose images for several patient groups were averaged after registering each patient’s RTdose data to the CT brain template created in our earlier study. The voxel-based (VB) analysis was used to examine the dose variations in the brains of three groups of NPC patients: the early-stage group, the stage III group, and the stage IV group. Results As the disease progresses from early to advanced stages, the intensity and volume of radiation in the brain increase. The normal brain tissue accepted a substantially larger dosage in more advanced NPC patients. Differences in brain regions between stage III and early-stage patients were minimal compared to any other two groups. Brain regions exhibited substantial variations between the stage IV group and all other patient groups were broadly distributed. Conclusion Our findings highlight the critical role of NPC staging in the therapeutic strategy, emphasizing the heterogeneity of radiation-induced tissue damage across disease stages and implying the need to develop stage-specific RT plans.

This study aims to evaluate the dosimetric performance and treatment efficiency of two linear accelerators, Halcyon and Infinity, in volumetric modulated arc therapy (VMAT) for non-small cell lung cancer (NSCLC). A retrospective analysis was conducted on treatment plans for 60 NSCLC patients who received conventional fractionated radiotherapy. All plans were optimized using RayStation 9A, with identical dose constraints and optimization parameters to ensure a fair comparison. Key comparisons were made regarding dose coverage of the target (CTV and PTV), dose exposure to organs at risk (OARs), treatment plan complexity (e.g., control points and monitor units (MUs)), and treatment efficiency (treatment time). The results indicate that the Halcyon platform has a significant advantage in treatment efficiency, while the differences in dosimetric characteristics between the two platforms were minimal. This study provides critical data to support platform selection in clinical practice and lays the foundation for future multi-center comparative studies.

Background: To determine whether a dual-isocenter volumetrically modulated arc therapy (VMAT) technique results in lower normal pulmonary dosage compared to a traditional single isocenter technique for boot-shaped lung cancer. Methods: A cohort of 15 patients with advanced peripheral or central lung cancer who had metastases in the mediastinum and supraclavicular lymph nodes was randomly selected for this retrospective study. VMAT plans were generated for each patient using two different beam alignment techniques with the 6-MV flattening filter-free (FFF) photon beam: single-isocenter jaw-tracking VMAT based on the Varian TrueBeam linear accelerator (S-TV), and dual-isocenter VMAT based on both TrueBeam (D-TV) and Halcyon linear accelerator (D-HV). For all 45 treatment plans, planning target volume (PTV) dose coverage, conformity/homogeneity index (CI/HI), mean heart dose (MHD), mean lung dose (MLD) and the total lung tissue receiving 5, 20, 30 Gy (V-5, V-20, V-30) were evaluated. The monitor units (MUs), delivery time, and plan quality assurance (QA) results were recorded. Results: The quality of the objectives of the three plans was comparable to each other. In comparison with S-TV, D-TV and D-HV improved the CI and HI of the PTV (p < 0.05). The MLD was 13.84 +/- 1.44 Gy (mean +/- SD) for D-TV, 14.22 +/- 1.30 Gy and 14.16 +/- 1.42 Gy for S-TV and D-HV, respectively. Lungs-V-5Gy was 50.78 +/- 6.24%, 52.00 +/- 7.32% and 53.36 +/- 8.48%, Lungs-V-20Gy was 23.72 +/- 2.27%, 26.18 +/- 2.86% and 24.96 +/- 3.09%, Lungs-V30Gy was 15.69 +/- 1.76%, 17.20 +/- 1.72% and 16.52 +/- 2.07%. Compared to S-TV, D-TV provided statistically significant better protection for the total lung, with the exception of the lungs-V-5. All plans passed QA according the gamma criteria of 3%/3 mm. Conclusions: Taking into account the dosimetric results and published clinical data on radiation-induced pulmonary injury, dual-isocenter jaw-tracking VMAT may be the optimal choice for treating boot-shaped lung cancer.

This study utilized the U-Net deep learning model to automate the segmentation of three-dimensional after-loaded metal source applicators, aiming to expedite treatment planning, reduce patient wait times, and enhance the treatment process. Using CT images from cervical cancer patients treated between December 2020 and August 2023, 27 images formed the training set, 3 were for validation, and 10 for testing. The model’s performance was evaluated against expert delineations using metrics like the Dice similarity coefficient (DSC), Hausdorff distance 95% (HD95), and others. The results were integrated into an after-loading planning system to locate applicator pathways and assess dose accuracy and feasibility. For the test group, the DSC ranged from 0.90 to 0.93, HD95 from 0.79 to 0.80 mm, and ASSD from 0.03 to 0.22 mm, with an average segmentation time of 65 seconds, significantly faster than manual delineation. The automatic pathways closely matched the original plan’s dosimetric parameters (P >0.05), indicating the system’s potential for safe application in after-loading planning for cervical cancer treatment. The U-Net-based region-growing method shows promise in improving the efficiency and accuracy of after-loaded applicator segmentation.

This study utilized the U-Net deep learning model to automate the segmentation of three-dimensional after-loaded metal source applicators, aiming to expedite treatment planning, reduce patient wait times, and enhance the treatment process. Using CT images from cervical cancer patients treated between December 2020 and August 2023, 27 images formed the training set, 3 were for validation, and 10 for testing. The model’s performance was evaluated against expert delineations using metrics like the Dice similarity coefficient (DSC), Hausdorff distance 95% (HD95), and others. The results were integrated into a after-loading planning system to locate applicator pathways and assess dose accuracy and feasibility. For the test group, the DSC ranged from 0.90 to 0.93, HD95 from 0.79 to 0.80 mm, and ASSD from 0.03 to 0.22 mm, with an average segmentation time of 65 seconds, significantly faster than manual delineation. The automatic pathways closely matched the original plan’s dosimetric parameters (P > 0.05), indicating the system’s potential for safe application in after-loading planning for cervical cancer treatment. The U-Net-based region-growing method shows promise in improving the efficiency and accuracy of after-loaded applicator segmentation.

The current Radiotherapy (RT) technology still inevitably irradiated normal brain tissue, causing implicit radiation-induced injury. This study investigates the precise localization and the corresponding radiation dosage of brain regions susceptible to damage in nasopharyngeal carcinoma (NPC) patients following RT. Utilizing the Advanced Normalization Tools (ANTs) package, a computed tomography (CT) brain template was created in the standard Montreal Neurological Institute (MNI) space, based on 803 Chinese NPC patients (T0~T4) who underwent RT. With this template, all patients' CT and RTdose data were registered to the MNI space, and the RTdose distribution characteristics in normal brain tissues were compared for NPC patients treated with Intensity-modulated radiotherapy (IMRT) or Volumetric Modulated Arc Therapy (VMAT), with patients' age and gender as covariates. Analysis of the average dosages indicated that certain areas within the Limbic, Temporal, and Posterior Lobes, the Brainstem, and the Cerebellum Posterior Lobe were exposed to doses exceeding 50 Gy. Inter-group analysis revealed that IMRT delivered higher doses than VMAT to brain regions anterior to the nasopharyngeal tumor, whereas VMAT affected the posterior regions more. Interestingly, VMAT showed a drawback in preserving the normal brain tissues for T4-stage patients. This revealed that the two treatment modalities have unique characteristics in preserving normal brain tissue, each with advantages. With better localization precision, the created CT brain template in MNI space may be beneficial for NPC patients' toxicity and dosimetric analyses.

Objective: This study aims to compare the dosimetric calculationsin standard non-small cell lung cancer (NSCLC) radiotherapy planningusing the Collapsed Cone (CC) algorithm of the RayStation planningsystem on the Varian Halcyon accelerator, with the Analytical AnisotropicAlgorithm (AAA) and Acuros XB algorithms on the Eclipse accelerator. Methods: The RayStation planning system was employed to designthe RapidArc radiotherapy plans for 15 lung cancer patients on theHalcyon accelerator, using the CC algorithm for dose calculation.The plans were then transferred to the Eclipse planning system. Withoutmaking any changes to these plans, doses were computed using bothAAA and Acuros XB algorithms. The differences in dose-volume indicesfor the clinical target volume (CTV), planned target volume (PTV),and other organs at risk were evaluated. Results: Compared with the CC algorithm, the AAA algorithmshowed slightly lower dose-volume indices for both the CTV (D2%,D50%, D95%, D98%, and mean dose) and the PTV (D2%, D50%, andmean dose), with differences within 1%. Specifically, the PTV's D95%and D98% were respectively 1.7% and 2.4% lower, the heart's meandose was 3.2% lower, the lung's V20Gy was 0.2% lower, the averagedose was 0.2% higher, and the spinal cord's maximum dose (representedby D0.1cc) was 0.9% lower. In contrast to the CC algorithm, the AcurosXB algorithm also showed slightly lower dose-volume indices for theCTV and the PTV, with differences within 1.5%. Specifically, thePTV's D95% and D98% were respectively 1.6% and 2.3% lower, theheart's mean dose was 4.4% lower, the lung's V20Gy was 0.3% lower,the average dose was 1.4% lower, and the spinal cord's maximum dosewas 2.3% lower. Paired t-tests indicated that all these results hadsignificant differences (p<0.05). Conclusion: This study aimed to quantify the impact of usingRayStation system and CC algorithm on Halcyon accelerator for clinicaldose evaluations, by comparing it with the AAA and Acuros XB algorithmsof the Varian Eclipse planning system. For lung cancer radiotherapyplanning, dose calculations obtained from the AAA and Acuros XB algorithmsunder the Eclipse system were slightly lower compared to the RayStationCC algorithm across various clinical indices. Notably, the differencesin the PTV's D95% and D98% indices were over 1.5%, while dose indicesfor various organs at risk were approximately 2 ∼ 3% lower. The results of this study can serve as a reference for institutionsthat are preparing to use the RayStation planning system for the designand clinical application of plans on the Varian Halcyon accelerator.

BackgroundRadiotherapy (RT) is the primary treatment for nasopharyngeal carcinoma (NPC). However, it can cause implicit RT-induced injury by irradiating normal brain tissue. To date, there have been no detailed reports on the radiated exact location in the brain, the corresponding radiation dose, and their relationship.MethodsWe analyzed 803 Chinese NPC patients treated with RT and used a CT brain template in a Montreal Neurological Institute (MNI) space to compare the group differences in RT dose distribution for different RT technologies (IMRT or VMAT).ResultsBrain regions that received high doses (>50 Gy) of radiation were mainly located in parts of the temporal and limbic lobes, where radioactive damage often occurs. Brain regions that accepted higher doses with IMRT were mainly located near the anterior region of the nasopharyngeal tumor, while brain regions that accepted higher doses with VMAT were mainly located near the posterior region of the tumor. No significant difference was detected between IMRT and VMAT for T1 stage patients. For T2 stage patients, differences were widely distributed, with VMAT showing a significant dose advantage in protecting the normal brain tissue. For T3 stage patients, VMAT showed an advantage in the superior temporal gyrus and limbic lobe, while IMRT showed an advantage in the posterior cerebellum. For T4 stage patients, VMAT showed a disadvantage in protecting the normal brain tissue. These results indicate that IMRT and VMAT have their own advantages in sparing different organs at risk (OARs) in the brain for different T stages of NPC patients treated with RT.ConclusionOur approach for analyzing dosimetric characteristics in a standard MNI space for Chinese NPC patients provides greater convenience in toxicity and dosimetry analysis with superior localization accuracy. Using this method, we found interesting differences from previous reports: VMAT showed a disadvantage in protecting the normal brain tissue for T4 stage NPC patients.

目的 介绍一种基于治疗中实时肿瘤运动状态的四维剂量重建方法,并使用该方法对已经完成治疗的肺癌立体定向放疗(SBRT)患者进行剂量学重建后的评估.方法 使用光学体表追踪系统获取肺癌SBRT技术下治疗时的肿瘤运动状态;基于Python语言计算出患者治疗期间不同四维CT时相上的治疗时间权重;在治疗计划系统中按治疗时间权重重建出患者每一个时相CT下患者的加权剂量;将加权剂量形变配准到平均密度投影CT上,得到患者的实际治疗的四维重建剂量,采用上述方法,序贯选取2022年1月至2023年1月在浙江省人民医院行SBRT治疗的10例早期非小细胞肺癌(NSCLC)患者进行四维剂量学评估,并与传统的三维剂量学评估方法进行剂量学参数的对比分析.结果 本研究中靶区的适形指数及剂量梯度指数R50、全肺的最小剂量及V10、肋骨超过3 cm3体积对应的剂量,两者比较差异均有统计学意义(均P＜0.05),其余靶区以及危及器官参数的剂量差异均无统计学意义(均P＞0.05),对危及器官和靶区的剂量偏差的纵向比较发现,除了第5例和第9例为患者肺的剂量偏差＞5％,第5例患者心脏剂量偏差较大(25％),第9例患者的适形指数偏差＞5％外,其余靶区剂量和危及器官剂量都在5％以内.结论 本文采用四维剂量重建方法,考虑到了患者治疗期间不同时相下解剖结构变化,并依据不同时相CT在治疗期间的时间权重进行了剂量加权修正,弥补了传统按平均时间剂量权重分配方法的不足,可以更加准确反映患者实际的照射剂量.