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Background: This study observed the clinical outcome of radiotherapy to extensive intrahepatic targets for advanced hepatocellular carcinoma (HCC) in a single institution. Methods: From September 2009 to July 2021, patients who underwent fractionated radiotherapy to a planning target volume (PTV) of over 100 ml with biological effective dose >30 Gy10 for advanced HCC were enrolled. Overall survival (OS) and radiation-induced liver toxicity (RILD) were evaluated. RILD was defined as an increase in Child-Pugh (CP) score ≥2 or liver function tests ≥2.5 times at 3 months after the end of radiotherapy. Results: A total of 136 patients were evaluated. Eighty-nine patients had portal vein tumor thrombus (PVTT), 37 patients were in CP B stage, and the median radiation dose to PTV was 48.8 Gy10. The median OS was 12.3 months. The factors most affecting OS were PVTT (P = 0.001), PTV (>500 ml, P = 0.001), incomplete coverage of the intrahepatic tumor (P = 0.004), and CP B (P = 0.006) in Cox regression. RILD occurred in 22.4% of the patients and was affected by PVTT (P = 0.003), PTV (P = 0.010), pretreatment bilirubin levels (>1.5 mg/ml, P = 0.016), and the mean normal liver dose (MNLD) (≥ EQD2 18 Gy3, P = 0.021) in binary logistic regression. As the PTV was in excess of >500 ml, RILD developed in 30.2% of patients and the prognostic importance of pretreatment bilirubin levels (P = 0.006) and the MNLD (P = 0.014) increased. Conclusions: As PTV is more extensive, the bilirubin level and the MNLD have to be taken into consideration for safe radiotherapy, in addition to the traditional prognostic factors. [ABSTRACT FROM AUTHOR]

Background: Intracranial stereotactic radiosurgery (SRS) aims at achieving highly conformal dose distribution and, at the same time, attaining rapid dose falloff outside the treatment target. SRS is performed using different techniques including dynamic conformal arcs (DCA) and volumetric modulated arc therapy (VMAT). Purpose: In this study, we compare dose conformity and falloff in DCA and VMAT plans for SRS with a single target. Methods: To compare dose conformity in SRS plans, we employ a novel conformity index CIdexp$C{I}_{{d}_{exp}}$, RTOG conformity index (CIRTOG$C{I}_{RTOG}$), and Riet‐Paddick conformity index (CIRP$C{I}_{RP}$). In addition, we use indices R50%$R50\% $, V10Gy${V}_{10Gy}$, and V12Gy${V}_{12Gy}$ to evaluate dose falloff. For each of the considered 118 cases of SRS, two plans were created using DCA and VMAT. A two‐tailed Student's t‐test was used to evaluate the difference between the employed indices for the DCA and VMAT plans. Results: The studied VMAT plans were characterized by higher dose conformity than the DCA plans. The differences between the conformity indices for the DCA plans and VMAT plans were statistically significant. The DCA plans had a smaller number of monitor units (MUs) and smaller indices R50%, V10Gy, and V12Gy than the VMAT plans. However, the differences between R50%, V10Gy, and V12Gy for the DCA and VMAT plans were not statistically significant. Conclusions: Although the studied VMAT plans had higher dose conformity, they also had larger MUs than the DCA plans. In terms of dose falloff characterized by parameters R50%, V10Gy, and V12Gy, DCA serves as a reasonable alternative to VMAT in the case of a single brain metastasis. [ABSTRACT FROM AUTHOR]

Background & Aims: The collimator angle significantly impacts radiation leakage between the multi-leaf collimator (MLCs) leaves. This study aims to examine dose-volume evaluation in planning target volume (PTV) and organs at risk (OARs) for Head & Neck patients undergoing volumetric-modulated arc therapy (VMAT) with 2.5 arcs and varying collimator angles. Materials & Methods: In this experimental study, five patients with nasopharyngeal cancer were selected for treatment with the VMAT method. CT images were prepared using a CT simulator and transferred to the treatment planning system. For optimizing VMAT plans, volume and dose constraints were applied to OARs and PTVs by the algorithm. Then, the doses were calculated using the AAA algorithm. Results: Although no significant differences were observed in DVH curves across different collimator angles, other parameters exhibited variations. Notably, in Head & Neck cancer patients, optimal values for dose conformity, homogeneity, MUs, and gradient index were found at collimator angles of 20° and 30°. Additionally, OAR sparing was favorable at these angles. Based on target coverage, homogeneity, and MUs, the collimator angles were optimized for VMAT planning. Conclusion: Our findings offer valuable guidance to clinical medical physicists in making informed decisions regarding collimator angles. The dosimetric analysis underscores the importance of selecting the optimal collimator angle for accurate PTV coverage.

Introduction:Breast cancer has been a leading malignancy in women across the globe. In breast conserving treatment, radiation therapy plays an important role. This is clinically approved that breast conserving surgery followed by adjuvant radiation therapy produces as the same survival rate as radical breast RT. The aim of this study was to find out suitable number of IMRT fields to treat left-sided breast cancer and analyze the effects of increasing the number of fields in IMRT plans.Material and Methods:We selected 105 patients retrospectively for this study diagnosed with left-sided breast cancer of age ranging from 33 to 74 years. There were 52 cases of chest wall (CW) irradiation including SCF, 20 cases of BCS and 33 cases were of CW including supra-clavicular fossa (SCF) and internal mammary lymph nodes (IMLN).Results:Our main objective was to analyze dose-distribution of left lung. Monitor Units (MUs) were also recorded and found almost same in these three modalities ranging from 1200 to 2000. The mean value of V20Gy(cc) in 11-bIMRT technique was found less by 8-17cc as compared to 7-and 9-bIMRT technique. It was observed that 11-bIMRT technique yielded slightly better outcomes in terms of V20Gy(cc).Conclusion: The technique 7-bIMRT gives slightly better result in controlling low-dose volume of underlying lung and heart. As the number of IMRT beams increases, it translates into better outcomes in terms of reducing high-dose volume as well as mean-dose of left lung. So, it is prudent to use ‘N’ number of IMRT fields such as 7≤ N ≤11 in left breast RT.

Stereotactic body radiation therapy is a novel treatment option for refractory ventricular tachycardia. We present a case of ventricular tachycardia, with epicardial origin located in large inferior infarct scar, that recurred despite treatment with multiple antiarrhythmic drugs, catheter ablation, and cardiac sympathetic denervation. Stereotactic body radiation therapy safely and effectively terminated the arrhythmia. (Level of Difficulty: Advanced.).

Background: Since 1964, there has been a scarcity of reported cases of primary ameloblastoma (AM) or ameloblastic carcinoma (AMCa) of the skull. The clinical presentation and distinctive features of this uncommon condition at specific anatomical sites remain unclear. We report a case of malignant transformation of a primary AM of the skull situated in the frontal-temporal-parietal region and highlight its similarities to other cases reported in the literature. Clinical presentation: A 53-year-old female patient presented with a 20-day history of headaches and bilateral lower limb weakness for 10 days. Physical examination revealed slow and unsteady gait. An occupying lesion was observed in the right frontal-temporal-parietal region of the skull on the Cranial imaging. A right cranial bone tumor margin expansion resection was performed. The patient's motor functions recovered normally after surgery. Postoperative imaging examinations showed10 tumor resection. Follow-up imaging examinations showed tumor recurrence. The patient underwent resection of the recurrent tumor. Postoperative pathological analysis revealed malignant transformation of the AM.Follow-up imaging examinations showed tumor recurrence again. The patient was admitted for stereotactic radiotherapy. Follow-up imaging examinations demonstrated no evidence of tumor recurrence and subsequent chest CT revealed no signs of metastasis. Conclusion: Primary AM or AMCa of the skull is increasingly being described in the literature, but detailed reports on the malignant transformation of primary AM of the skull are lacking. The pathogenesis of this condition remains unclear. Aggressive treatment and close follow-up may be crucial for preventing disease recurrence and malignant transformation. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to investigate whether variations in cranial angles and treatment accuracy during CyberKnife robotic radiosurgery necessitate adjustment of the margins of the planning target volume. Patients and Methods: Data from 66 patients receiving CyberKnife treatment for brain tumors were retrospectively analyzed. Patients were immobilized using a thermoplastic mask and headrest. The cranial angle was measured on planning CT and patients were divided into 2 groups: ≤10° (Group A) and >10° (Group B). Intrafractional motion was recorded using the CyberKnife tracking system over 50 min. Translational and rotational errors were compared between groups, and planning target volume margins were calculated. Results: In Group A, significant translational error differences were found along with the X-axis over time (P <.02). In Group B, significant differences occurred along with the Z-axis (P <.03). No significant rotational or 3-dimensional vector differences were found in either group. Group A had significantly lower Y-axis (P <.045) and roll axis (P <.005) errors compared to Group B. Estimated planning target volume margins in Group A were 0.56 mm (X), 0.46 mm (Y), and 0.47 mm (Z). In Group B, margins were 0.62 mm (X), 0.48 mm (Y), and 0.46 mm (Z). Margins covering 95% of intrafraction motion were 0.49 to 0.50 mm (X, Y, Z) and 0.69 mm (3-dimensional vector) for Group A, and 0.48 to 0.60 mm and 0.79 mm for Group B. With a 1-mm margin, complete coverage was achieved in Group A while 2.1% of vectors in Group B exceeded 1 mm. Conclusion: Adjusting cranial angle to ≤10° during thermoplastic mask molding provided better or similar intrafractional stability compared to >10°. [ABSTRACT FROM AUTHOR]

Background: Evaluation of dose conformity is important to ensure minimum dose to normal tissue and sufficient dose coverage of the planning target volume (PTV). The existing conformity indices depend on the PTV volume and do not differentiate between two different scenarios: overdosing normal tissue and underdosing PTV. Purpose: In this study, we introduce a novel index to assess conformity of dose distributions in radiotherapy. Methods: The suggested conformity index CIdexp$C{I_{{d_{exp}}}}$ is defined by the ratio of the volume representing actual "non‐conformity" of the planned dose and the volume representing acceptable "non‐conformity." The latter volume is produced by expanding the PTV. If both the average distance (d¯$\overline d $) between the reference isodose surface and planning target volume and arbitrarily selected PTV expansion margin (dexp${d_{exp}}$) are much smaller than the size of the PTV, CIdexp$C{I_{{d_{exp}}}}$ approximately equals the ratio d¯dexp$\dfrac{{\bar d}}{{{d_{exp}}}}$. In this work, CIdexp$C{I_{{d_{exp}}}}$ was utilized to analyze 90 cases of brain metastases treated with stereotactic radiation therapy (SRS) and 102 cases of lung cancer treated with stereotactic body radiation therapy (SBRT). Results: For dexp${d_{exp}}$ = 0.1 cm, all considered SRS treatment plans were characterized by CIdexp<1$C{I_{{d_{exp}}}} < 1$ while 2 out of 102 SBRT plans had CIdexp>1$C{I_{{d_{exp}}}} > 1$. The average values of CIdexp$C{I_{{d_{exp}}}}$ for SRS and SBRT plans were 0.31 and 0.43, respectively. For dexp${d_{exp}}$ = 0.2 cm, all studied treatment plans had CIdexp<1$C{I_{{d_{exp}}}} < 1$, and the average values of CIdexp$C{I_{{d_{exp}}}}$ for SRS and SBRT plans were 0.15 and 0.25, respectively. Conclusions: The suggested conformity index CIdexp$C{I_{{d_{exp}}}}$ varies less with PTV volume than the RTOG and Riet‐Paddick indices frequently used for evaluation of dose conformity. In addition, CIdexp$C{I_{{d_{exp}}}}$ can be expressed as a sum of two terms which describe "over‐coverage" and "under‐coverage" of the treatment target. The results confirm that CIdexp$C{I_{{d_{exp}}}}$ can be used for evaluation of dose conformity in SRS and SBRT. [ABSTRACT FROM AUTHOR]

Background: Set-up errors are an undesirable part of the radiation treatment process. The goal of online imaging is to increase treatment accuracy by reducing the set-up errors. This study aimed to determine the daily variation of patient set-up uncertainties and planning target volume (PTV) margins for head and neck cancer patients using pre-treatment verification by mega voltage cone-beam computed tomography (MV-CBCT). Materials and methods: This retrospective study was internal record base of head and neck (H&N) cancer patients treated with definitive radiotherapy, adjuvant radiotherapy, and hypo-fractionated radiotherapy at our institution since the implementation of HalcyonTM 2.0 machine (Varian, US). Errors collected from each patient setup were recorded and evaluated for each direction [medio-lateral (ML), supero-inferior (SI), antero-posterior (AP)] discretely. For each patient, the systematic error (∑) and random error (σ) were collected. Clinical target volume (CTV) to planning target volume (PTV) margin was calculated using International Commission on Radiation Units and Measurements (ICRU) 62 (PTV margin = √(∑² + σ²)) Stroom's (PTV margin = 2∑ + 0.7σ), and Van Herk's (PTV margin = 2.5∑) + 0.7σ) formula. Results: A total of 7900 pre-treatment CBCT scans of 301 patients were analyzed and a total of 23,000 error measurements in the ML, SI, and AP directions were recorded. For all of our H&N cancer patients, the CTV to PTV margin, calculated from the van Herk formula for the head and neck patients was 0.49 mm in the anteroposterior axis. Conclusions: An isometric PTV margin of 5 mm may be considered safe if daily imaging is not being done. In case daily online pretreatment imaging is being utilized, further reduction of PTV margin is possible. [ABSTRACT FROM AUTHOR]

To retrospectively analyze the accuracy of radiotherapy using cone beam computed tomography (CBCT), Styrofoam fixation, and breast bracket fixation in the chest wall target area and supraclavicular lymphatic drainage area (supraclavicular target area) of patients with breast cancer.and compare the setting efficiency and comfort satisfaction. A total of 65 patients with postoperative lymphatic metastasis of breast cancer, including 36 cases of Styrofoam fixation and 29 cases of breast bracket fixation, were recruited from March 2021 to August 2022 and retrospectively analyzed. All the patients underwent CBCT scans weekly, and the setup errors of the chest wall and supraclavicular target volume were compared and recorded. The planning target volume (PTV) margins of the two groups were calculated using the correlation MPTV = 2.5Σ + 0.7σ. The setup time and comfort satisfaction scores of the two groups were recorded and analyzed. The correlations among errors in each direction were analyzed using the Pearson correlation analysis. There was a significant difference in the left-right direction (X) axis of the chest wall target area between the Styrofoam and breast bracket groups (1.59 ± 1.47 mm vs. 2.05 ± 1.64 mm, P = 0.012). There were statistical differences in the ventrodorsal direction (Z) and bed angle of the supraclavicular target area, the data were (1.36 ± 1.27 mm vs. 1.75 ± 1.55 mm, P = 0.046; 0.47 ± 0.47° vs. 0.66 ± 0.59°, P = 0.006, respectively). In the X, Y, and Z directions, the respective PTV margins of the two groups in the chest wall target area were 5.01 mm, 5.99 mm, and 5.47 mm in the Styrofoam group, while those in the breast bracket group were 6.10 mm, 6.34 mm, and 6.10 mm, respectively. Moreover, the PTV margins of the supraclavicular target in the three directions were 3.69 mm, 3.86 mm, and 4.28 mm in the Styrofoam group, while those in the breast bracket group were 3.99 mm, 3.72 mm, and 5.45 mm, respectively. The setup time of the two groups was 3.4 ± 1.1 min and 5.5 ± 3.1 min (P = 0.007). The subjective comfort satisfaction scores of the two groups were 27.50 ± 1.24 and 25.44 ± 1.23 (P < 0.001). The application of Styrofoam fixation in radiotherapy of breast cancer in the supraclavicular lymph node area has several advantages as compared to breast bracket fixation, including higher positioning accuracy, smaller external expansion boundary, improved work efficiency, and patients' comfort, which might provide a reference for clinical work. [ABSTRACT FROM AUTHOR]

Objective To explore the risk factors for neutropenia (grade 2 or higher) during postoperative adjuvant radiotherapy for breast cancer. Methods A total of 93 patients with breast cancer treated by postoperative adjuvant radiotherapy in Shaanxi Provincial People’s Hospital from January 2018 to December 2020 were assigned to a control group (no neutropenia or grade 1 neutropenia, n=62) and an observation group (grade 2 or higher neutropenia, n=31). The clinical data of the two groups were analyzed by univariate and logistic regression analyses to determine the independent risk factors for grade 2 or higher neutropenia, and the predictive efficacy of risk factors was established by the receiver operating characteristic (ROC) curve. Results The univariate analysis results showed that there were significant differences between the two groups in molecular types of breast cancer, white blood cell count and absolute neutrophil count at the first visit, proportion of patients with grade 4 myelosuppression during chemotherapy, white blood cell count, absolute neutrophil count, hemoglobin before radiotherapy, planning target volume (PTV), mean radiotherapy dose to the sternum (Dmean), and ratio of volume exposed to radiation greater than 20 Gy to total vo-lume and ratio of volume exposed to radiation greater than 30 Gy to total volume in the sternum (χ2=4.511,9.900,t=2.286-9.900,P733.28 mL and sternum Dmean >2 213.5 cGy are independent risk factors for grade 2 or higher neutropenia during postoperative adjuvant radiotherapy for breast cancer, and the combination of the two indices can improve the predictive efficacy for the occurrence of neutropenia.

Objective: To investigate the dosimetric effects of using individualized silicone rubber (SR) bolus on the target area and organs at risk (OARs) during postmastectomy radiotherapy (PMRT), as well as evaluate skin acute radiation dermatitis (ARD). Methods: A retrospective study was performed on 30 patients with breast cancer. Each patient was prepared with an individualized SR bolus of 3 mm thickness. Fan-beam computed tomography (FBCT) was performed at the first and second fractions, and then once a week for a total of 5 times. Dosimetric metrics such as homogeneity index (HI), conformity index (CI), skin dose (SD), and OARs including the heart, lungs, and spinal cord were compared between the original plan and the FBCTs. The acute side effects were recorded. Results: In targets' dosimetric metrics, there were no significant differences in Dmean and V105% between planning computed tomography (CT) and actual treatments (P >.05), while the differences in D95%, V95%, HI, and CI were statistically significant (P <.05). In OARs, there were no significant differences between the Dmean, V5, and V20 of the affected lung, V5 of the heart and Dmax of the spinal cord (P >.05) except the V30 of affected lung, which was slightly lower than the planning CT (P <.05). In SD, both Dmax and Dmean in actual treatments were increased than plan A, and the difference was statistically significant (P <.05), while the skin-V20 and skin-V30 has no difference. Among the 30 patients, only one patient had no skin ARD, and 5 patients developed ARD of grade 2, while the remaining 24 patients were grade 1. Conclusion: The OR bolus showed good anastomoses and high interfraction reproducibility with the chest wall, and did not cause deformation during irradiation. It ensured accurate dose delivery of the target and OARs during the treatment, which may increase SD by over 101%. In this study, no cases of grade 3 skin ARD were observed. However, the potential of using OR bolus to reduce grade 1 and 2 skin ARD warrants further investigation with a larger sample size. [ABSTRACT FROM AUTHOR]

Recent innovations in image guidance, treatment delivery, and adaptive radiotherapy (RT) have created a new paradigm for planning target volume (PTV) margin design for patients with prostate cancer. We performed a review of the recent literature on PTV margin selection and design for intact prostate RT, excluding post-operative RT, brachytherapy, and proton therapy. Our review describes the increased focus on prostate and seminal vesicles as heterogenous deforming structures with further emergence of intra-prostatic GTV boost and concurrent pelvic lymph node treatment. To capture recent innovations, we highlight the evolution in cone beam CT guidance, and increasing use of MRI for improved target delineation and image registration and supporting online adaptive RT. Moreover, we summarize new and evolving image-guidance treatment platforms as well as recent reports of novel immobilization strategies and motion tracking. Our report also captures recent implementations of artificial intelligence to support image guidance and adaptive RT. To characterize the clinical impact of PTV margin changes via model-based risk estimates and clinical trials, we highlight recent high impact reports. Our report focusses on topics in the context of PTV margins but also showcase studies attempting to move beyond the PTV margin recipes with robust optimization and probabilistic planning approaches. Although guidelines exist for target margins conventional using CT-based image guidance, further validation is required to understand the optimal margins for online adaptation either alone or combined with real-time motion compensation to minimize systematic and random uncertainties in the treatment of patients with prostate cancer. [ABSTRACT FROM AUTHOR]

Introduction: Breast cancer has been a leading malignancy in women across the globe. In breast conserving treatment, radiation therapy plays an important role. This is clinically approved that breast conserving surgery followed by adjuvant radiation therapy produces as the same survival rate as radical breast RT. The aim of this study was to find out suitable number of IMRT fields to treat left-sided breast cancer and analyze the effects of increasing the number of fields in IMRT plans. Material and Methods:We selected 105 patients retrospectively for this study diagnosed with left-sided breast cancer of age ranging from 33 to 74 years. There were 52 cases of chest wall (CW) irradiation including SCF, 20 cases of BCS and 33 cases were of CW including supra-clavicular fossa (SCF) and internal mammary lymph nodes (IMLN). Results:Our main objective was to analyze dose-distribution of left lung. Monitor Units (MUs) were also recorded and found almost same in these three modalities ranging from 1200 to 2000. The mean value of V20Gy(cc) in 11-bIMRT technique was found less by 8-17cc as compared to 7-and 9-bIMRT technique. It was observed that 11-bIMRT technique yielded slightly better outcomes in terms of V20Gy(cc). Conclusion: The technique 7-bIMRT gives slightly better result in controlling low-dose volume of underlying lung and heart. As the number of IMRT beams increases, it translates into better outcomes in terms of reducing high-dose volume as well as mean-dose of left lung. So, it is prudent to use 'N' number of IMRT fields such as 7= N =11 in left breast RT. [ABSTRACT FROM AUTHOR]

Simple Summary: Vision transformers have been recently spread out to enhance segmentation accuracy, becoming an active area of research and development involved in radiotherapy. We found that the new network architecture did not guarantee improvement. Conventional CNN-based networks struggled with being expanded to the auto-segmentation of tumors from normal organs due to local geometric dependence and difficulty in the hyper-parameter selection. As seen in the development and success of nnU-Net, we emphasized the importance of finding suitable hyper-parameters for the vision transformer. We applied our proposed framework based on VT U-Net v.2 to the prostate target volume segmentation, followed by extensively validating its performance in segmentation accuracy against the other five competing deep neural networks through four-fold cross-validation using CT images. U-Net, based on a deep convolutional network (CNN), has been clinically used to auto-segment normal organs, while still being limited to the planning target volume (PTV) segmentation. This work aims to address the problems in two aspects: 1) apply one of the newest network architectures such as vision transformers other than the CNN-based networks, and 2) find an appropriate combination of network hyper-parameters with reference to recently proposed nnU-Net ("no-new-Net"). VT U-Net was adopted for auto-segmenting the whole pelvis prostate PTV as it consisted of fully transformer architecture. The upgraded version (v.2) applied the nnU-Net-like hyper-parameter optimizations, which did not fully cover the transformer-oriented hyper-parameters. Thus, we tried to find a suitable combination of two key hyper-parameters (patch size and embedded dimension) for 140 CT scans throughout 4-fold cross validation. The VT U-Net v.2 with hyper-parameter tuning yielded the highest dice similarity coefficient (DSC) of 82.5 and the lowest 95% Haussdorff distance (HD95) of 3.5 on average among the seven recently proposed deep learning networks. Importantly, the nnU-Net with hyper-parameter optimization achieved competitive performance, although this was based on the convolution layers. The network hyper-parameter tuning was demonstrated to be necessary even for the newly developed architecture of vision transformers. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate set-up error for head and neck cancer (HNC) patients according to each neck lymph node (LN) level. And clinical factors affecting set-up error were analyzed. Materials and Methods: Reference points (RP1, RP2, RP3, and RP4) representing neck LN levels I to IV were designated. These RP were contoured on simulation computed tomography (CT) and conebeam CT of 89 HNC patients with the same standard. After image registration was performed, movement of each RP was measured. Univariable logistic regression analyses were performed to analyze clinical factors related to measured movements. Results: The mean value of deviation of all axes was 1.6 mm, 1.3 mm, 1.8 mm, and 1.5 mm for RP1, RP2, RP3, and RP4, respectively. Deviation was over 3 mm in 24 patients. Movement of more than 3 mm was observed only in RP1 and RP3. In RP1, it was related to bite block use. Movement exceeding 3 mm was most frequently observed in RP3. Primary tumor and metastatic LN volume change were clinical factors related to the RP3 movement. Conclusion: Planning target volume margin of 4 mm for neck LN level I, 3 mm for neck LN level II, 5 mm for neck LN level III, and 3 mm for neck LN level IV was required to include all movements of each LN level. In patients using bite block, changes in primary tumor volume, and metastatic LN volume were related to significant movement. [ABSTRACT FROM AUTHOR]

Introduction: A system for stabilizing and monitoring eye movements during LINAC‐based photon beam one single fraction stereotactic radiotherapy was developed at our Institution. This study aimed to describe the feasibility and the efficacy of our noninvasive optical localization system that was developed, tested, and applied in 20 patients treated for uveal melanoma. Methods: Our system consisted of a customized thermoplastic mask to immobilize the head, a gaze fixation LED, and a digital micro‐camera. The localization procedure, which required the active collaboration of the patient, served to monitor the eye movements during all phases of the treatment, starting from the planning computed tomography up to the administration of radiotherapy, and allowed the operators to suspend the procedure and to interact with the patient in case of large movements of the pupil. Results: Twenty patients were treated with stereotactic radiosurgery (27 Gy in one fraction) for primary uveal melanoma. All patients showed a good tolerance to the treatment; until now, all patients were in local control during the follow up and one died for distant progression 6 months after radiosurgery. Conclusions: This study showed that this noninvasive technique, based on eye position control, is appropriate and can contribute to the success of LINAC‐based stereotactic radiotherapy. A millimetric safety margin to the clinical target volume was adequate to take account for the organ movement. All patients treated till now showed a good local control; failures in the disease control were due to metastatic spread. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the impact of treatment time and patterns in inoperable stage III non-small cell lung cancer (NSCLC) following concurrent chemoradiotherapy (cCRT) ± immune checkpoint inhibitors (ICIs). Methods: Patients were stratified by treatment year: A (2011–2014), B (2015–2017) and C (2018–2020). Tumor- and treatment-related characteristics regarding locoregional recurrence-free survival (LRRFS), progression-free survival (PFS) and overall survival (OS) were investigated. Results: One hundred and thirty-six consecutive patients were analyzed. All patients completed thoracic radiotherapy (TRT) to a total dose ≥ 60.0 Gy; 36 (26%) patients received ICI. Median PFS in subgroups A, B and C was 8.0, 8.2 and 26.3 months (p = 0.007). Median OS was 19.9 months, 23.4 months and not reached (NR), respectively. In group C, median LRRFS and PFS were 27.2 vs. NR; and 14.2 vs. 26.3 months in patients treated with and without ICI. On multivariate analysis planning target volume (PTV) ≥ 700 cc was a negative prognosticator of LRRFS (HR 2.194; p = 0.001), PFS (HR 1.522; p = 0.042) and OS (HR 2.883; p = 0.001); ICI was a predictor of LRRFS (HR 0.497; p = 0.062), PFS (HR 0.571; p = 0.071) and OS (HR 0.447; p = 0.1). In the non-ICI cohort, multivariate analyses revealed PTV ≥ 700 cc (p = 0.047) and a maximum standardized uptake value (SUVmax) ≥ 13.75 (p = 0.012) were predictors of PFS; PTV ≥ 700 cc (p = 0.017), SUVmax ≥ 13.75 (p = 0.002) and a total lung V20 ≥ 30% (V20 ≥ 30) (p < 0.05) were predictors of OS. Conclusions: Patients treated after 2018 had improved survival regardless of ICI use. Implementation of ICI resulted in further significant increase of all tested survival endpoints. PTV ≥ 700 cc and ICI were only prognosticators for LRRFS, PFS and OS in the analyzed cohort. [ABSTRACT FROM AUTHOR]

Purpose: To assess the optimal planning target volume (PTV) margins for stereotactic body radiotherapy (SBRT) of prostate cancer based on inter- and intra-fractional prostate motion determined from daily image guidance. Methods and Materials: Two hundred and five patients who were enrolled on two prospective studies of SBRT (8 Gy × 5 fractions) for localized prostate cancer treated at a single institution between 2012 and 2017 had complete inter- and intra-fractional shift data available. All patients had scheduled kilovoltage planar imaging during SBRT with rigid registration to intraprostatic fiducials prior to each of four half-arcs delivered per fraction, as well as cone beam CT verification of anatomy prior to each fraction. Inter- and intra- fractional shift data were obtained to estimate the required PTV margins based on the classic van Herk formula. Inter- and intra-fractional motion were compared between patients with and without severe toxicities using the independent two-sample Wilcoxon test. Results: The margins required to account for inter-fractional motion were estimated to be 0.99, 1.52, and 1.45 cm in lateral (LR), longitudinal (SI), and vertical (AP) directions, respectively. The margins required to account for intra-fractional motion were estimated to be 0.19, 0.27, and 0.31 cm in LR, SI and AP directions, respectively. Large intra-fractional shifts were mostly observed in the SI and AP directions, with 2.0 and 5.4% of patients experiencing average intra-fractional motion >3 mm in the SI and AP directions, respectively, compared with none experiencing mean shifts >3 mm in the LR direction. Six patients experienced grade 3 gastrointestinal or genitourinary toxicity. There were no significant differences in mean inter- or intra-fractional motion in any of the cardinal directions compared to patients without severe toxicity (inter-fractional p = 0.46-0.99, intra-fractional p = 0.10-0.84). Conclusion: The inter- and intra-fractional margins estimated from this study are in line with prior reported values. Intra-fractional prostate motion was generally small with larger margins required for the SI and AP directions, notably just slightly exceeding the commonly used 3 mm posterior PTV margin even with realignment between half-arcs. Development of severe toxicity was not significantly associated with the degree of inter- or intra-fractional motion.

Accurately calculating setup errors is crucial in ensuring quality assurance for patients undergoing radiation therapy treatment. This cross-sectional study aimed to determine the systematic, random, and planning target volume (PTV) margin errors for patients with head and neck cancer (n=48) and breast cancer (n=50). The treatment setup was performed using electronic portal imaging (EPIDs) and irradiated using Elekta linac. The errors were calculated using the van Herk formula. The systematic error for the head and neck was 0.89, 0.43, and 1.49 mm on the x, y, and z-axis, respectively, and 0.39, 0.74, 0.38 for the breast cases. The random error was 0.82, 0.68, 0.94 mm for the head and neck and 0.66, 0.72, 0.79 mm for the breast. The PTV margin shifting error for the head and neck were 2.79, 1.55, and 4.38 mm, while it was 1.43, 2.35, and 1.50 mm for the breast. The setup errors varied according to the tumor location. The study highlights the potential benefits of using EPIDs for reducing uncertainties in setup verification procedures. [ABSTRACT FROM AUTHOR]

Transperineal ultrasound (TPUS) is an image-guided radiotherapy system used for tracking intrafraction prostate displacements in real time. The objectives of this study are to evaluate intrafraction prostate displacements and derive planning target volume (PTV) margins for prostate radiotherapy at our institution. The ultrasound (US) data of nine prostate cancer patients referred for VMAT radiotherapy was retrieved. Prior to beam on, patient position was set up with the US probe positioned transperineally with the aid of reference images (fused US and computed tomography images). In each fraction, prostate displacements in three directions [superior/inferior (SI), left/right (LR) and anterior/posterior (AP)] were recorded. PTV margins were determined using Van Herk's formula. To assess the prostate displacement time trend, continuous displacement data were plotted in 30-s intervals for eight minutes. The intrafraction prostate monitoring found a population mean setup error (Mp) of 0.8, 0.1, − 1.7 mm, a systematic error of (∑p) 0.7, 0.4, 0.9 mm and random error (σp) of 0.2, 0.1, 0.3 mm in SI, LR and AP directions, respectively. The PTV margin was found to be the largest in the AP direction at 2.5 mm compared with 1.9 mm and 1.1 mm for SI and LR directions, respectively. The PTV margin allowed for prostate radiotherapy at our institution was 2.5 mm in all directions. The prostate displacement time trend showed an increase in intrafraction displacements, with most patients were observed to have strong positive correlation between time and intrafraction prostate displacements in SI direction. TPUS is feasible for monitoring intrafraction displacement of the prostate and may facilitate PTV margin generation to account for such displacements during radiotherapy. [ABSTRACT FROM AUTHOR]

Introduction: With innovation of medical imaging, radiotherapy attempts to conform the high dose region to the planning target volume (PTV). The present work aimed to assess the angle of concavity in PTV can be adopted as selection criteria for intensity-modulated radiation therapy (IMRT) or three-dimensional conformal radiotherapy (3DCRT) technique in Brain tumors. Materials and Methods: Thirty previously irradiated patients with brain tumors were replanned with both 3DCRT and IMRT technique. Angle of concavity (dip) in the PTV near the organs at risk was measured in the contoured structure set images of each patient. These cases were divided into three groups where angles were 0°, >120° and <120°. Dose of 60 Gy/30# was fixed. Results: In Group 1, the IMRT plan had better TV95% as compared to 3DCRT respectively with significant P value (P = 0.002). Mean of conformity index (CI) and Homogeneity Index (HI) were comparable. For Group 2 (angle >120°), the IMRT plan had better TV95% as compared to 3DCRT respectively with a significant P value (P = 0.021). HI and CI were not significant. For Group 3 (<120°), IMRT plan had better TV95% as compared to 3DCRT respectively with a significant P value (P = 0.001). HI and CI were better in IMRT arm with significant P value. Conclusion: The results from this study showed that the angle of concavity can be considered as an additional objective tool for selection criteria whether tumor can be treated with IMRT or 3DCRT. Tumors where angle of concavity was <120°, HI and CI provided more uniformity and conformity of dose distribution inside PTV with significant P values. [ABSTRACT FROM AUTHOR]

Purpose: We describe a new approach to evaluate conformity of dose distributions in radiotherapy. Methods: The suggested conformity factor is defined by using existing conformity indices and expansion of the planning target volume (PTV). If the average distance (d) between the PTV and reference isodose surface and an arbitrarily selected PTV expansion margin (dexp) are both much smaller than the size of the PTV, then approximately equals the ratio d dexp. We use to analyze several cases of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). Results: In the case of SRS with a single target or multiple targets, treatment plans produced with the help of volumetric modulated arc therapy (VMAT) have smaller than plans produced by using dynamic conformal arcs (DCA). Likewise, it is demonstrated that in the case of SBRT, is reduced by employing VMAT instead of DCA.It is also shown that if the distance between the reference isodose surface and surface of the PTV is fixed, varies less with variations in PTV volume compared to frequently used conformity indices. Conclusions: The described conformity factor can be applied clinically to compare and rank treatment plans for lesions of different sizes. It is suggested that conditions < 1 and > 1 can be employed as "pass" and "fail" criteria, respectively, for dose conformity assessment with appropriate choice of dexp. [ABSTRACT FROM AUTHOR]

Objectives: Image-guided radiotherapy maximizes therapeutic index of brain irradiation by reducing setup errors during treatment. The aim of study was to analyze setup errors in the radiation treatment of glioblastoma multiforme and if decrease in planning target volume (PTV), margin is feasible using daily cone beam CT (CBCT) and 6D couch correction. Materials and Methods: Twenty-one patients (630 fractions of radiotherapy) were studied in which corrections were made in 6° of freedom. We determined setup errors, impact of setup errors of initial three fractions CBCT versus rest of the treatment with daily CBCT, and mean difference in setup errors with or without application of 6D couch and volumetric benefit of reduction of PTV margin from 0.5 cm to 0.3 cm. Results: The mean shift in the conventional directions, namely, vertical, longitudinal, and lateral was 0.17 cm, 0.19 cm, and 0.11 cm. There was significant change in vertical shift when first three fractions were compared with rest of the treatment with daily CBCT. When the effect of 6D couch was nullified, all directions showed increased error with longitudinal shift being significant. The number of setup errors of magnitude >0.3 cm was more significant when only conventional shifts were applied as compared with 6D couch. There was significant decrease in volume of brain parenchyma irradiated when margin of PTV was reduced from 0.5 cm to 0.3 cm. Conclusion: Daily CBCT along with 6D couch correction can reduce setup error which allows reduction in PTV margin during radiotherapy planning in turn improving the therapeutic index. [ABSTRACT FROM AUTHOR]

Aim: The intent of the review was to identify different methodological approaches used to calculate the planning target volume (PTV) margin for head and neck patients treated with volumetric arc therapy (VMAT), and whether the necessary factors to calculate the margin size with the selected formula were used. Materials and Methods: A comprehensive, systematic search of related studies was done using the Hydi search engine and different databases: MEDLINE, PubMed, CINAHL, ProQuest (Nursing and Allied Health), Scopus, ScienceDirect and tipsRO. The literature search included studies published between January 2007 and December 2020. Eligibility screening was performed by two reviewers. Results: A total of seven studies were found. All the reviewed studies used the Van Herk formula to measure the PTV margin. None of the studies incorporated the systematic errors of target volume delineation in the PTV equation. Inter-fraction translational errors were assessed in all the studies, whilst intra-fraction errors were only included in the margin equation for two studies. The studies showed great heterogeneity in the key characteristics, aims and methods. Findings: Since systemic errors from target volume delineation were not considered and not all studies assess intra-fraction errors, PTV margins may be underestimated. The recommendations are that studies need to determine the effect of target volume variance on PTV margins. It is also recommended to compare PTV margin results using various formulas. [ABSTRACT FROM AUTHOR]

Purpose: Tumor motion is a major challenge in stereotactic ablative body radiotherapy (SABR) for non-small cell lung cancer (NSCLC), causing excessive irradiation to compensate for this motion. Real-time tumor tracking with a magnetic resonance imaging-guided linear accelerator (MR-Linac) could address this problem. This study aimed to assess the effects and advantages of MR-Linac in SABR for the treatment of lung tumors. Methods: Overall, 41 patients with NSCLC treated with SABR using MR-Linac between March 2019 and December 2021 were included. For comparison, 40 patients treated with SABR using computed tomography-based modalities were also enrolled. The SABR dose ranged from 48 to 60 Gy in 3–5 fractions. The primary endpoint was a lower radiation volume compared to CT-based SABR. The secondary endpoint was the local control rate of SABR using the MR-Linac. Results: The median follow-up time was 19 months (range: 3–105 months). There was no significant difference in the gross tumor volume between the MR and CT groups (7.1 ± 9.3 cm3 vs 8.0 ± 6.8 cm3, p = 0.643), but the planning target volume was significantly smaller in the MR group (20.8 ± 18.8 cm3 vs 34.1 ± 22.9 cm3, p = 0.005). The 1-year local control rates for the MR and CT groups were 92.1 and 75.4%, respectively (p = 0.07), and the 1-year overall survival rates were 87.4 and 87.0%, respectively (p = 0.30). Conclusion: Lung SABR with MR-Linac can reduce the radiation field without compromising the local control rate. Further follow-up is needed to assess the long-term effects. [ABSTRACT FROM AUTHOR]

Abstract Introduction Current contouring guidelines for curative radiation therapy for muscle‐invasive bladder cancer (MIBC) recommend margins of 1.5–2.0 cm, applied to the clinical target volume (CTV). This study assessed whether the use of volumetric modulated arc therapy (VMAT), cone beam computed tomography (CBCT) and strict bladder preparation allowed for a reduced planning target volume (PTV) expansion, resulting in lower doses to surrounding organs at risk (OARs). Methods Daily CBCT images for 12 patients (382 scans total) were retrospectively reviewed against four potential PTV margins created on and exported with the reference CT scan. To form the PTVs, three isotropic expansions of 0.5, 1.0 and 1.5 cm were applied to the CTV, as well as an anisotropic expansion of 1.5 cm superiorly and 1.0 cm in all other dimensions. Following treatment completion, the CBCTs were visually assessed to determine the margins encapsulating the bladder. For retrospective planning purposes, the 1.0‐cm and anisotropic margins were compared with the previously recommended margins to determine differences in OAR doses. Results The 0.5‐, 1.0‐ and 1.5‐cm isotropic margins (IM) and the anisotropic margin (ANIM) covered the CTV in 46.1, 96.8, 100 and 100% of CBCTs retrospectively. Doses to OARs were significantly lower for the reduced margin plans for the small bowel, rectum and sigmoid. Conclusion Bladder planning target volumes may be safely reduced. We endorse a PTV margin of 1.0cm anteriorly, posteriorly and inferiorly with 1.0–1.5 cm superiorly for radical whole bladder cases using strict bladder preparation, VMAT and pretreatment CBCTs.

Abstract Introduction Guidelines recommend that the proximal seminal vesicles (PrSV) should be included in the clinical target volume for locally advanced prostate cancer patients undergoing radiotherapy. Verification and margins for the prostate may not necessarily account for PrSV displacement. The purpose was to determine the inter‐fraction displacement of the PrSV relative to the prostate during radiotherapy. Methods Fiducials were inserted into the prostate, and right and left PrSV (RSV and LSV) in 30 prostate cancer patients. Correctional shifts for the prostate, right and left PrSV and pelvic bones were determined from each patient's 39 daily orthogonal portal images relative to reference digitally reconstructed radiographs. Results There was a significant displacement of the RSV relative to the prostate in all directions: on average 0.38 mm (95% confidence interval (CI) 0.26 to 0.50) to the left, 0.80–0.81 mm (CI 0.68 to 0.93) superiorly and 1.51 mm (CI 1.36 to 1.65) posteriorly. The LSV was significantly displaced superiorly to the prostate 1.09–1.13 mm (CI 0.97 to 1.25) and posteriorly 1.81 mm (CI 1.67 to 1.96), but not laterally (mean 0.06, CI −0.06 to 0.18). The calculated PTV margins (left–right, superior–inferior, posterior–anterior) were 4.9, 5.3–5.6 and 4.8 mm for the prostate, 5.2, 7.1–8.0 and 9.7 mm for the RSV, and 7.2, 7.5–7.6 and 8.6 mm for the LSV. Conclusion There is a significant displacement of the PrSV relative to the prostate during radiotherapy. Greater margins are recommended for the PrSV compared to the prostate.

Purpose: In the beam penumbra of stereotactic body radiotherapy volumes, dose rate effects in implantable cardioverter-defibrillators (ICDs) may be the predominant cause for failures in the absence of neutron-generating photon energies. We investigate such dose rate effects in ICDs and provide evidence for safe use of lung tumor stereotactic radioablation with flattening filter free (FFF) and flattened 6 Megavolt (MV) beams in ICD-bearing patients.Methods: Sixty-two ICDs were subjected to scatter radiation in 1.0, 2.5, and 7.0 cm distance to 100 Gy within a 5 × 5 cm2 radiation field. Radiation was applied with 6 MV FFF beams (constant dose rate of 1400 cGy/min) and flattened (FLAT) 6 MV beams (430 cGy/min). Local dose rates (LDR) at the position of all ICDs were measured. All ICDs were monitored continuously.Results: With 6 MV FFF beams, ICD errors occurred at distances of 1.0 cm (LDR 46.8 cGy/min; maximum ICD dose 3.4 Gy) and 2.5 cm (LDR 15.6 cGy/min; 1.1 Gy). With 6 MV FLAT beams, ICD errors occurred only at 1 cm distance (LDR 16.8 cGy/min; 3.9 Gy). No errors occurred at an LDR below 7 cGy/min, translating to a safe distance of 2.5 cm (1.5 Gy) in flattened and 7 cm (0.4 Gy) in 6 MV FFF beams.Conclusion: A LDR in ICDs larger than 7 cGy/min may cause ICD malfunction. At identical LDR, differences between 6 MV FFF and 6 MV FLAT beams do not yield different rates of malfunction. The dominant reason for ICD failures could be the LDR and not the total dose to the ICD. For most stereotactic treatments, it is recommended to generate a planning risk volume around the ICD in which LDR larger than 7 cGy/min are avoided. [ABSTRACT FROM AUTHOR]

A dosimetric study was performed to show the importance of adaptive radiotherapy (ART) for head and neck cancer (HNC) patients using volumetric modulated arc therapy (VMAT). A total of 13 patients with HNC who required replanning during radiotherapy were included in this study. All plans succeeded to achieve the set objectives regarding target volume coverage and organ sparing. All target volumes presented a significant decrease with an average of 76.44 cm3 (p = 0.007) for PTVlow risk, 102.81 cm3 (p = 0.021) for PTVintermediate risk, and 47.10 cm3 (p = 0.003) for PTVhigh risk. Additionally, a positive correlation was found between PTV shrinkage and the number of fractions completed before replanning. Significant volume decrease was also observed for the parotid glands. The ipsilateral parotid decreased in volume by a mean of 3.75 cm3 (14.43%) (p = 0.067), while the contralateral decreased by 4.23 cm3 (13.23%) (p = 0.033). For all analyzed organs, a reduction in the final dose received after replanning was found. Our study showed that ART via rescanning, recontouring, and replanning using VMAT is essential whenever anatomical and positional variations occur. Furthermore, comparison with the literature has confirmed that ART using VMAT offers similar results to ART with intensity modulated radiotherapy. [ABSTRACT FROM AUTHOR]

Purpose: To quantify the relative motion of pelvic and groin lymph nodes (PLN and GLN) and define indicative margins for image-guided radiotherapy based on bony anatomy for the frog-leg position (FLP) and groin immobilization board (GIB). Materials and Methods: Twenty patients with planning computed tomography (CT) scan and on treatment cone beam CTs (median = 8) for groin and pelvic radiotherapy were included in the study. Of these nine were treated with FLP and eleven with GIB. The PLN and GLN regions on the left and right were outlined in each scan. Systematic and random uncertainties were determined along with correlations between the motions of these regions. The clinical target volume to planning target volume (PTV) margins required to take motion into account was calculated for each immobilization. Results: The mean shifts for PLN and GLN were lesser but not statistically lower using GIB over FLP. There was significant concordance in the vertical, longitudinal and lateral motion of the pelvis and right groin (P = 0.015, 0.09 and 0.049, respectively), pelvis and left groin (P = 0.001, 0.048, and 0.006, respectively) and between left and right groin (P = 0.013, 0.01 and 0.07, respectively) for FLP and not GIB. The PTV margins required by Van Herk and Stroom's formula were reduced from 11 mm and 9 mm to 6 mm and 5 mm for pelvis; 12 mm and 11 mm to 7 mm and 6 mm for groin, respectively, using FLP over GIB. Conclusions: GIB brings concordance in shifts between pelvis and groin and between bilateral groins, thereby reducing the required PTV margins.

Abstract Background Radiotherapy of gastric mucosa-associated lymphoid tissue (MALT) lymphoma should be delivered to the entire stomach with planning target volume (PTV) that accounts for variations in stomach volume, respiratory movement, and patient set-up error. In this study, we evaluated whether the use of four-dimensional cone-beam computed tomography (4D-CBCT) reduces the PTV. Methods Eight patients underwent radiotherapy with 15 fractions of gastric MALT lymphoma using 4D-CBCT. PTV structures of 5–30 mm margins (5 mm intervals) from the clinical target volume (CTV) delineated based on the 4D-CT images (CTV-4D) were generated. For the target localization, we performed matching based on skin marking (skin matching), bone anatomy (bone matching), and stomach anatomy (4D soft-tissue matching) based on registration between planning CT and 4D-CBCT images from 10 phases. For each patient, we calculated the covering ratio (CR) of the stomach with variable PTV structures, based on the 4D-CBCT images, with a total of 150 phases [CR (%) = (number of covering phases/150 phases) × 100], for three target localization methods. We compared the CR values of the different target localization methods and defined the PTV with an average CR of ≥ 95% for all patients. Results The average CR for all patients increased from 17.9 to 100%, 19.6 to 99.8%, and 33.8 to 100%, in the skin, bone, and 4D soft-tissue matchings, respectively, as the PTV structures increased from 5 to 30 mm. The CR obtained by 4D soft-tissue matching was superior to that obtained by skin (P = 0.013) and bone matching (P = 0.008) for a PTV structure of 15 mm margin. The PTV required an additional margin of 20 mm (average CR: 95.2%), 25 mm (average CR: 99.1%), and 15 mm (average CR: 98.0%) to CTV-4D for the skin, bone, and 4D soft-tissue matchings, respectively. Conclusions This study demonstrates that the use of 4D-CBCT reduces the PTV when applying 4D soft-tissue matching, compared to skin and bone matchings. Additionally, bone matching does not reduce the PTV as compared with traditional skin matching.

3D - Conformal Radiotherapy (3DCRT) for decades was a standard technique in the prostate cancer radical radiotherapy treatment. Technological advances and implementation of an innovative radiotherapy technique-Intensity Modulated Radiation Therapy (IMRT), enable even more precise treatment of the prostate cancer patients. Intensity Modulated Radiation Therapy (IMRT) is a technological advancement in Conformal Radiotherapy which allows superior conformity and homogeneity of the absorbed dose in planning target volume with maximal sparing organs of risk. This technique gives us possibility to escalate the radiotherapy dose, prerequisite for the adequate local tumor control. Evaluation of dosimetric parameters 3DCRT vs. IMRT: the homogeneity index, the conformity index, parameters of absorbed dose in planning target volume, dose volume constraints for organs of risk shows that IMRT is an optimal technique in the prostate cancer radical treatment. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate the dosimetric effect and delivery reliability of jaw tracking (JT) with increasing planning target volume (PTV) for lung stereotactic body radiation therapy (SBRT) plans. A threshold of PTV was proposed as a selection criterion between JT and fixed-jaw (FJ) techniques. Methods: A total of 28 patients with early-stage non-small-cell lung cancer were retrospectively included. The PTVs ranged from 4.88 cc to 68.74 cc, prescribed with 48 Gy in four fractions. Three-partial-arc volumetric modulated arc therapy (VMAT) plans with FJ and with JT were created for each patient with the same optimization objectives. These two sets of plans were compared using metrics, including conformity index (CI), V50%, R50%, D2cm, dose–volume parameters of organs at risk, and monitor units (MUs). The ratio of small subfields (<3 cm in either dimension), %SS, was acquired as a surrogate for the small-field uncertainty. Statistical analyses were performed to evaluate the correlation between the differences in these parameters and the PTV. Results: The V50%, R50%, D2cm, and V20Gy, D1,500cc, and D1,000cc of the lung showed a statistically significant improvement in JT plans as opposed to FJ plans, while the number of MU in JT plans was higher by an average of 1.9%. Between FJ and JT plans, the PTV was strongly correlated with the differences in V50%, moderately correlated with those in V20Gy of the lung, and weakly correlated with those in D2cm and D1,500cc of the lung. By using JT, %SS was found to be negatively correlated with the PTV, and the PTV should be at least approximately 12.5 cc for an expected %SS <50%, which was 15 cc for a %SS <20% and 20 cc for a %SS <5%. Conclusions: Considering the dosimetric differences and small-field uncertainties, JT could be selected using a PTV threshold, such as 12.5, 15, or 20 cc, on the basis of the demand of delivery reliability for lung SBRT. [ABSTRACT FROM AUTHOR]

Introduction This study aimed to estimate the planning target volume (PTV) margin in lung tumors using 4D computed tomography (CT) scan and evaluate other factors that have an effect on tumor motion. Materials and Methods We recruited 43 biopsy-proven, newly diagnosed carcinoma lung patients who were treated with definitive intent from January 2017 to June 2018. The radiation dose was delivered using a 3D conformal radiation therapy (CRT)/intensity-modulated radiotherapy (IMRT)/volumetric modulated arc therapy (VMAT) plan to a dose of 6000 to 6600 cGy in 30 or more fractions to the whole primary. All patients underwent 4D CT scan on the Elekta machine where all the 10 phases of respiration in free breathing were recorded. These phases are fused with CT simulation images, on which gross tumor volume (GTV) and clinical target volume (CTV) are contoured in all phases of respiration. Following this, an internal target volume (ITV) was created by measuring tumor motion all the directions from the center of tumor and PTV was concluded. Results The mean ITV for tumor in all six directions, that is, in superior, inferior, anterior, posterior, medial and lateral directions was 0.9, 0.9, 0.8, 0.9, 0.8, and 0.9 cm, respectively. For coverage of tumor for 90% of patients, the margins required in superior, inferior, anterior, posterior, medial, and lateral directions were 1.3, 1.5, 1.5, 1.4, 1.5, and 1.3 cm, respectively. Other factors such as size of the tumor and location of the tumor did not significantly contribute to PTV changes in our study. Conclusion Mean ITV for tumor in all six directions summed up to be 0.8 cm, but there was significant movement in inferior direction for upper lobe tumors (0.9 cm) (p = 0.008), in medial direction for middle lobe tumors (0.8 cm) (p = 0.05), and in medial direction for lower lobe tumors (0.75 cm) (p = 0.005).

PurposeThis study aimed to investigate the dosimetric effect and delivery reliability of jaw tracking (JT) with increasing planning target volume (PTV) for lung stereotactic body radiation therapy (SBRT) plans. A threshold of PTV was proposed as a selection criterion between JT and fixed-jaw (FJ) techniques.MethodsA total of 28 patients with early-stage non-small-cell lung cancer were retrospectively included. The PTVs ranged from 4.88 cc to 68.74 cc, prescribed with 48 Gy in four fractions. Three-partial-arc volumetric modulated arc therapy (VMAT) plans with FJ and with JT were created for each patient with the same optimization objectives. These two sets of plans were compared using metrics, including conformity index (CI), V50%, R50%, D2cm, dose–volume parameters of organs at risk, and monitor units (MUs). The ratio of small subfields (

Online adaptive radiotherapy (oART) uses daily imaging to identify changes in the patient's anatomy and generate a new treatment plan adapted to these changes, and it can be used for treating gastric mucosa-associated lymphoid tissue (MALT) lymphomas. This study aimed to determine the intrafraction motion and planning target volume (PTV) margins required for an oART workflow on a cone beam computed tomography (CBCT)-based dedicated system (Ethos®, Varian Medical Systems, Palo Alto, California, United States) and investigate the potential benefits for patients compared with a non-adaptive workflow. Involving three patients treated for gastric MALT lymphoma with the oART under breath-hold (BH) technique, the study determined a PTV margin for adaptive treatment using CBCT scans performed at the beginning and just before treating the patients for 34 fractions. Different PTVs were made by isotropically extending the clinical target volume (CTV) contoured on the first CBCT (CTV1) at intervals of 1 mm to evaluate intrafraction gastric motion, with the expansion covering the contoured CTV on the second CBCT (CTV2) quantifying the intrafraction motion (adaptive treatment) and the expansion from the CTV delineated on the planning scanner (CTVplanning) that could cover both CTV1 and CTV2 defining the interfraction motion (non-adaptive treatment). PTV margins were then determined as the extension of the CTV allowing coverage of 95% of its volume in 90% of fractions, and the dosimetric impact on dose constraints between an adaptive plan and a non-adaptive plan based on the predetermined margins was evaluated. A total of 68 CBCTs were analyzed, revealing that the PTV margin for oART was 4 mm, while for non-adaptive treatment it was 12 mm, with an average time elapsed between CBCT1 and CBCT2 of 11.62 minutes and no correlation between inter-CBCT timing and PTV margins (Pearson R-coefficient=0.10). All dosimetric constraints were met in both adaptive and non-adaptive plans, but the adaptive plan allowed for reduced organ-at-risk (OAR) doses in each patient. The study concluded that oART could reduce PTV margins in the treatment of gastric MALT lymphoma, especially with a BH strategy, impacting OAR dosimetry, though more prospective studies are required to validate these findings and determine their clinical impact on patients., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: Julien Pierrard declare(s) a grant from Varian, a Siemens Healthineers Company. His PhD project (wich has nothing to do with this work) was partially funded by Varian. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Tison et al.)

Introduction: Current contouring guidelines for curative radiation therapy for muscle‐invasive bladder cancer (MIBC) recommend margins of 1.5–2.0 cm, applied to the clinical target volume (CTV). This study assessed whether the use of volumetric modulated arc therapy (VMAT), cone beam computed tomography (CBCT) and strict bladder preparation allowed for a reduced planning target volume (PTV) expansion, resulting in lower doses to surrounding organs at risk (OARs). Methods: Daily CBCT images for 12 patients (382 scans total) were retrospectively reviewed against four potential PTV margins created on and exported with the reference CT scan. To form the PTVs, three isotropic expansions of 0.5, 1.0 and 1.5 cm were applied to the CTV, as well as an anisotropic expansion of 1.5 cm superiorly and 1.0 cm in all other dimensions. Following treatment completion, the CBCTs were visually assessed to determine the margins encapsulating the bladder. For retrospective planning purposes, the 1.0‐cm and anisotropic margins were compared with the previously recommended margins to determine differences in OAR doses. Results: The 0.5‐, 1.0‐ and 1.5‐cm isotropic margins (IM) and the anisotropic margin (ANIM) covered the CTV in 46.1, 96.8, 100 and 100% of CBCTs retrospectively. Doses to OARs were significantly lower for the reduced margin plans for the small bowel, rectum and sigmoid. Conclusion: Bladder planning target volumes may be safely reduced. We endorse a PTV margin of 1.0cm anteriorly, posteriorly and inferiorly with 1.0–1.5 cm superiorly for radical whole bladder cases using strict bladder preparation, VMAT and pretreatment CBCTs. [ABSTRACT FROM AUTHOR]

To evaluate the impact of the planning target volume (PTV) density on treatment planning for lung Stereotactic Body Radiation Therapy (SBRT). The PTV coverage was analyzed in two groups of 40 lung SBRT patients. One group had PTV density <0.5 g/cm3, while the other group had PTV density >0.5 g/cm3. The treatments were planned in Pinnacle 9.10, using the collapsed cone convolution (CCC) algorithm. The prescribed dose was 60 Gy to the PTV in 4–8 fractions. Respecting constraint for the PTV coverage (D98% > 95%), we compared changes in the isodose line prescription, the number of monitor units (MU), maximum dose (Dmax), irradiated volume covered with 30 Gy (V30Gy), and the optimization planning volume (OPV). For the same median values of the PTV coverage (98.3%), the differences are presented with median values between lower and higher density than 0.5 g/cm3. The isodose line prescription was 83 vs. 90% (p < 0.0001), the MUs were 2294 vs. 1655 MU (p < 0.0001), Dmax was 74.26 vs. 68.09 Gy (p < 0.0001), V30Gy was 117.03 vs. 104.81 cc (p = 0.04), and OPV was 28.48 vs. 39.35 cc (p < 0.001). By overriding the ITV density to 0.8 g/cm3, the isodose line prescription decreases. The Dmax and MUs decrease by 7%, V30Gy by 34%, and OPV by 70%. To obtain similar PTV coverage for PTV which is <0.5 g/cm3, a larger margin irradiating a large OPV was used. More MUs and a higher maximum dose were delivered. For the PTV density of ≤0.36 g/cm3, overriding is recommended to reduce the dose and irradiated volume. [ABSTRACT FROM AUTHOR]

Introduction: Guidelines recommend that the proximal seminal vesicles (PrSV) should be included in the clinical target volume for locally advanced prostate cancer patients undergoing radiotherapy. Verification and margins for the prostate may not necessarily account for PrSV displacement. The purpose was to determine the inter‐fraction displacement of the PrSV relative to the prostate during radiotherapy. Methods: Fiducials were inserted into the prostate, and right and left PrSV (RSV and LSV) in 30 prostate cancer patients. Correctional shifts for the prostate, right and left PrSV and pelvic bones were determined from each patient's 39 daily orthogonal portal images relative to reference digitally reconstructed radiographs. Results: There was a significant displacement of the RSV relative to the prostate in all directions: on average 0.38 mm (95% confidence interval (CI) 0.26 to 0.50) to the left, 0.80–0.81 mm (CI 0.68 to 0.93) superiorly and 1.51 mm (CI 1.36 to 1.65) posteriorly. The LSV was significantly displaced superiorly to the prostate 1.09–1.13 mm (CI 0.97 to 1.25) and posteriorly 1.81 mm (CI 1.67 to 1.96), but not laterally (mean 0.06, CI −0.06 to 0.18). The calculated PTV margins (left–right, superior–inferior, posterior–anterior) were 4.9, 5.3–5.6 and 4.8 mm for the prostate, 5.2, 7.1–8.0 and 9.7 mm for the RSV, and 7.2, 7.5–7.6 and 8.6 mm for the LSV. Conclusion: There is a significant displacement of the PrSV relative to the prostate during radiotherapy. Greater margins are recommended for the PrSV compared to the prostate. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of present study is to estimate asymmetric margins of prostate target volume based on biological limitations with help of knowledge based fuzzy logic considering the effect of organ motion and setup errors. Materials and Methods: A novel application of fuzzy logic modelling technique considering radiotherapy uncertainties including setup, delineation and organ motion was used in this study to derive margins. The new margin was applied in prostate cancer treatment planning and the results compared very well to current techniques Here volumetric modulated arc therapy treatment plans using stepped increments of asymmetric margins of planning target volume (PTV) were performed to calculate the changes in prostate radiobiological indices and results were used to formulate the rule based and membership function for Mamdani-type fuzzy inference system. The optimum fuzzy rules derived from input data, the clinical goals and knowledge-based conditions imposed on the margin limits. The PTV margin obtained using the fuzzy model was compared to the commonly used margin recipe. Results: For total displacement standard errors ranging from 0 to 5 mm the fuzzy PTV margin was found to be up to 0.5 mm bigger than the vanHerk derived margin, however taking the modelling uncertainty into account results in a good match between the PTV margin calculated using our model and the one based on van Herk et al. formulation for equivalent errors of up to 5 mm standard deviation (s. d.) at this range. When the total displacement standard errors exceed 5 mm s. d., the fuzzy margin remained smaller than the van Herk margin. Conclusion: The advantage of using knowledge based fuzzy logic is that a practical limitation on the margin size is included in the model for limiting the dose received by the critical organs. It uses both physical and radiobiological data to optimize the required margin as per clinical requirement in real time or adaptive planning, which is an improvement on most margin models which mainly rely on physical data only.

Image‐guided, intensity modulated radiation therapy (IG‐IMRT) reduces dose to pelvic organs at risk without losing dose coverage to the planning target volume (PTV) and might permit margin reductions potentially resulting in lower toxicity. Appropriate PTV margins have not been established for IG‐IMRT in abdominopelvic tumours in dogs, and herein we explore if our usual PTV 5 mm margin can be reduced further. Datasets from dogs that underwent IG‐IMRT for non‐genitourinary abdominopelvic neoplasia with 5 mm‐PTV expansion were included in this retrospective virtual study. The clinical target volumes and organs at risk (OAR) colon, rectum, spinal cord were adapted to each co‐registered cone‐beam computed tomography (CBCT) used for positioning. New treatment plans were generated and smaller PTV margins of 3 mm and 4 mm evaluated with respect to adequate dose coverage and normal tissue complication probability (NTCP) of OAR. Ten dogs with a total of 70 CBCTs were included. Doses to the OAR of each CBCT deviated mildly from the originally planned doses. In some plans, insufficient build‐up of the high dose‐area at the body surface was found due to inadequate or missing bolus placement. Overall, the margin reduction to 4 mm or 3 mm did not impair dose coverage and led to significantly lower NTCP in all OAR except for spinal cord delayed myelopathy. However, overall NTCP for spinal cord was very low (<4%). PTV‐margins depend on patient immobilization and treatment technique and accuracy. IG‐IMRT allows treatment with very small margins in the abdominopelvic region, ensuring appropriate target dose coverage, while minimizing NTCP. [ABSTRACT FROM AUTHOR]

Target delineation uncertainty is arguably the largest source of geometric uncertainty in radiotherapy. Several factors can affect it, including the imaging modality used for delineation. It is accounted for by applying safety margins to the target to produce a planning target volume (PTV), to which treatments are designed. To determine the margin, the delineation uncertainty is measured as the delineation error, and then a margin recipe used. However, there is no published evidence of such analysis for recurrent gynaecological cancers (RGC). The aims of this study were first to quantify the delineation uncertainty for RGC gross tumour volumes (GTVs) and to calculate the associated PTV margins and then to quantify the difference in GTV, delineation uncertainty and PTV margin, between a computed tomography-magnetic resonance imaging (CT-MRI) and MRI workflow. Seven clinicians delineated the GTV for 20 RGC tumours on co-registered CT and MRI datasets (CT-MRI) and on MRI alone. The delineation error, the standard deviation of distances from each clinician's outline to a reference, was measured and the required PTV margin determined. Differences between using CT-MRI and MRI alone were assessed. The overall delineation error and the resulting margin were 3.1 mm and 8.5 mm, respectively, for CT-MRI, reducing to 2.5 mm and 7.1 mm, respectively, for MRI alone. Delineation errors and therefore the theoretical margins, varied widely between patients. MRI tumour volumes were on average 15% smaller than CT-MRI tumour volumes. This study is the first to quantify delineation error for RGC tumours and to calculate the corresponding PTV margin. The determined margins were larger than those reported in the literature for similar patients, bringing into question both current margins and margin calculation methods. The wide variation in delineation error between these patients suggests that applying a single population-based margin may result in PTVs that are suboptimal for many. Finally, the reduced tumour volumes and safety margins suggest that patients with RGC may benefit from an MRI-only treatment workflow. • The first paper to focus on recurrent gynaecological tumour radiotherapy targets • Presents values for delineation error and the corresponding safety margins • Standard methods produce margins larger than those reportedly used elsewhere • Using MRI alone results in smaller target volumes than using CT and MRI together [ABSTRACT FROM AUTHOR]