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Simple Summary: Stereotactic Body Radiotherapy (SBRT) is emerging as a promising, ablative, non-invasive alternative for treating liver and pancreatic tumors. The high conformality of SBRT, essential to minimize radiation-induced side effects on nearby gastrointestinal organs at risk while ensuring the delivery of high biologically effective doses to the tumor, makes the precise delineation of the target volume even more critical. While four-dimensional computed tomography (4DCT) remains the standard imaging modality for respiratory motion assessment, it often struggles to clearly visualize abdominal tumors due to poor contrast with the surrounding normal tissues in terms of Hounsfield Units (HUs). In this study, we report on our institutional approach to improve target volume delineation and respiratory motion management in abdominal SBRT planning by integrating 4DCT simulation with synchronized intravenous contrast injection. Background/Objectives: To present the technical aspects of contrast-enhanced 4DCT (ce4DCT) simulation for abdominal SBRT. Methods: Twenty-two patients underwent two sequential 4DCT scans: one baseline and one contrast-enhanced with personalized delay time (tdelay) calculated to capture the tumor in the desired contrast phase, based on diagnostic triple-phase CT. The internal target volume (ITV) was delineated on ten contrast phases, and a panel of three experts qualitatively evaluated tumor visibility. Aortic HU values were measured to refine the tdelay for subsequent patients. The commonly used approach of combining triple-phase CT with unenhanced 4DCT was simulated, and differences in target delineation were evaluated by volume, centroid shift, Dice and Jaccard indices, and mean distance agreement (MDA). The margins required to account for motion were calculated. Results: The ce4DCT acquisitions substantially improved tumor visibility over the entire breathing cycle in 20 patients, according to the experts' unanimous evaluation. The median contrast peak time was 54.5 s, and the washout plateau was observed at 70.3 s, with mean peak and plateau HU values of 292 ± 59 and 169 ± 25. The volumes from the commonly used procedure (ITV2) were significantly smaller than the ce4DCT volumes (ITV1) (p = 0.045). The median centroid shift was 4.7 mm. The ITV1-ITV2 overlap was 69% (Dice index), 53% (Jaccard index), and 2.89 mm (MDA), with the liver volumes showing significantly lower indices compared to the pancreatic volumes (p ≤ 0.011). The margins required to better encompass ITV1 were highly variable, with mean values ≥ 4 mm in all directions except for the left–right axis. Conclusions: The ce4DCT simulation was feasible, resulting in optimal tumor enhancement with minimal resource investment, while significantly mitigating uncertainties in SBRT planning by addressing poor visibility and respiratory motion. Triple-phase 3DCT with unenhanced 4DCT led to high variability in target delineation, making the isotropic margins ineffective. [ABSTRACT FROM AUTHOR]

Abstract Background We investigated the clinical outcomes of involved‐field high‐dose (≥66 Gy) chemoradiotherapy (CRT) combined with respiratory motion management for esophageal squamous cell carcinoma (ESCC). Methods Patients who underwent definitive CRT for histologically confirmed ESCC in our department between 2012 and 2018 were retrospectively analyzed. Respiratory motion management strategies included breath‐holding (63%) and mask immobilization (29%) based on individual measurements of respiratory tumor motion using radiographic fluoroscopy with endoscopically placed clip markers as landmarks. We evaluated patient characteristics, treatment efficacy, failure patterns, and toxicities. Results We enrolled 35 patients with a prescribed dose of 66–70 Gy in 33–35 fractions. The overall response rate within 6 months post‐CRT was 94.3%; the median follow‐up period for survivors was 43 months. The 2‐year overall survival (OS), progression‐free survival, and locoregional failure‐free survival rates were 51.4%, 42.9%, and 42.9%, respectively. A significant difference in OS was observed between patients with and without esophageal fistulas after CRT (p = 0.002, log‐rank test). Disease failure occurred in 16 patients (45.7%), including one (2.9%) with out‐of‐field regional nodal failure. Major grade 3 or higher toxicities included decreased white blood cell count (48.6%), neutrophil count (34.3%), and esophageal stenosis (31.4%). No grade 3 or higher cardiopulmonary toxicities were observed. Bronchial/tracheal tumor compression and a higher radiotherapy dose (70 Gy) were significantly correlated with esophageal fistulas. Conclusion Involved‐field high‐dose CRT with respiratory motion management may be a feasible treatment option for ESCC. However, a comprehensive assessment of esophageal fistula risk is required to identify suitable candidates.

Abstract The advancement of precision radiotherapy techniques, such as volumetric modulated arc therapy (VMAT), stereotactic body radiotherapy (SBRT), and particle therapy, highlights the importance of radiotherapy in the treatment of cancer, while also posing challenges for respiratory motion management in thoracic and abdominal tumors. MRI-guided radiotherapy (MRIgRT) stands out as state-of-art real-time respiratory motion management approach owing to the non-ionizing radiation nature and superior soft-tissue contrast characteristic of MR imaging. In clinical practice, MR imaging often operates at a frequency of 4 Hz, resulting in approximately a 300 ms system latency of MRIgRT. This system latency decreases the accuracy of respiratory motion management in MRIgRT. Artificial intelligence (AI)-based respiratory motion prediction has recently emerged as a promising solution to address the system latency issues in MRIgRT, particularly for advanced contour prediction and volumetric prediction. However, implementing AI-based respiratory motion prediction faces several challenges including the collection of training datasets, the selection of prediction methods, and the formulation of complex contour and volumetric prediction problems. This review presents modeling approaches of AI-based respiratory motion prediction in MRIgRT, and provides recommendations for achieving consistent and generalizable results in this field.

Background: We investigated the clinical outcomes of involved‐field high‐dose (≥66 Gy) chemoradiotherapy (CRT) combined with respiratory motion management for esophageal squamous cell carcinoma (ESCC). Methods: Patients who underwent definitive CRT for histologically confirmed ESCC in our department between 2012 and 2018 were retrospectively analyzed. Respiratory motion management strategies included breath‐holding (63%) and mask immobilization (29%) based on individual measurements of respiratory tumor motion using radiographic fluoroscopy with endoscopically placed clip markers as landmarks. We evaluated patient characteristics, treatment efficacy, failure patterns, and toxicities. Results: We enrolled 35 patients with a prescribed dose of 66–70 Gy in 33–35 fractions. The overall response rate within 6 months post‐CRT was 94.3%; the median follow‐up period for survivors was 43 months. The 2‐year overall survival (OS), progression‐free survival, and locoregional failure‐free survival rates were 51.4%, 42.9%, and 42.9%, respectively. A significant difference in OS was observed between patients with and without esophageal fistulas after CRT (p = 0.002, log‐rank test). Disease failure occurred in 16 patients (45.7%), including one (2.9%) with out‐of‐field regional nodal failure. Major grade 3 or higher toxicities included decreased white blood cell count (48.6%), neutrophil count (34.3%), and esophageal stenosis (31.4%). No grade 3 or higher cardiopulmonary toxicities were observed. Bronchial/tracheal tumor compression and a higher radiotherapy dose (70 Gy) were significantly correlated with esophageal fistulas. Conclusion: Involved‐field high‐dose CRT with respiratory motion management may be a feasible treatment option for ESCC. However, a comprehensive assessment of esophageal fistula risk is required to identify suitable candidates. [ABSTRACT FROM AUTHOR]

The advancement of precision radiotherapy techniques, such as volumetric modulated arc therapy (VMAT), stereotactic body radiotherapy (SBRT), and particle therapy, highlights the importance of radiotherapy in the treatment of cancer, while also posing challenges for respiratory motion management in thoracic and abdominal tumors. MRI-guided radiotherapy (MRIgRT) stands out as state-of-art real-time respiratory motion management approach owing to the non-ionizing radiation nature and superior soft-tissue contrast characteristic of MR imaging. In clinical practice, MR imaging often operates at a frequency of 4 Hz, resulting in approximately a 300 ms system latency of MRIgRT. This system latency decreases the accuracy of respiratory motion management in MRIgRT. Artificial intelligence (AI)-based respiratory motion prediction has recently emerged as a promising solution to address the system latency issues in MRIgRT, particularly for advanced contour prediction and volumetric prediction. However, implementing AI-based respiratory motion prediction faces several challenges including the collection of training datasets, the selection of prediction methods, and the formulation of complex contour and volumetric prediction problems. This review presents modeling approaches of AI-based respiratory motion prediction in MRIgRT, and provides recommendations for achieving consistent and generalizable results in this field. [ABSTRACT FROM AUTHOR]

Background: Recent advances in stereotactic body radiation therapy (SBRT) technology for early-stage peripheral lung cancer have been remarkable and are becoming a viable alternative to surgery. However, the most important problem in performing SBRT correctly is minimizing the respiratory motion of the tumor. Materials and methods: Thirty-eight patients treated with SBRT were evaluated to clarify factors affecting respiratory motion of early-stage peripheral lung cancer in the management of restrictive breathing technique (abdominal compression) to reduce respiratory tumor motion in SBRT. We investigated age, gender, body mass index (BMI), Brinkman index (BI), forced expiratory volume in 1 second (FEV 1.0), and type of ventilatory impairment as patient factors, and T-factor, stage, tumor-bearing lung lobe, and tumor pathology as tumor factors. Respiratory motion was assessed by volume differences between clinical target volume (CTV) and internal target volume (ITV). The degree of tumor motion due to respiration was compared using the formula of (ITV–CTV)/CTV as an index. Results: In the results, univariate analyses showed that only age was a significant predictor of respiratory tumor motion (p = 0.048). In multi-variate analyses, only T factor was an independent significant predictor of respiratory tumor motion (p = 0.045), while there was a significant trend for age (p = 0.061), and tumor location (p = 0.067). Conclusions: In late elderly patients or T1a tumor, respiratory motion in early-stage peripheral lung cancer was significantly large. However, it is not predictable by patient and tumor characteristics. Therefore, respiratory motion of the tumor should be measured in all patients in some way. [ABSTRACT FROM AUTHOR]

Purpose: High‐quality CBCT and AI‐enhanced adaptive planning techniques allow CBCT‐guided stereotactic adaptive radiotherapy (CT‐STAR) to account for inter‐fractional anatomic changes. Studies of intra‐fractional respiratory motion management with a surface imaging solution for CT‐STAR have not been fully conducted. We investigated intra‐fractional motion management in breath‐hold Ethos‐based CT‐STAR and CT‐SBRT (stereotactic body non‐adaptive radiotherapy) using optical surface imaging combined with onboard CBCTs. Methods: Ten cancer patients with mobile lower lung or upper abdominal malignancies participated in an IRB‐approved clinical trial (Phase I) of optical surface image‐guided Ethos CT‐STAR/SBRT. In the clinical trial, a pre‐configured gating window (± 2 mm in AP direction) on optical surface imaging was used for manually triggering intra‐fractional CBCT acquisition and treatment beam irradiation during breath‐hold (seven patients for the end of exhalation and three patients for the end of inhalation). Two inter‐fractional CBCTs at the ends of exhalation and inhalation in each fraction were acquired to verify the primary direction and range of the tumor/imaging‐surrogate (donut‐shaped fiducial) motion. Intra‐fractional CBCTs were used to quantify the residual motion of the tumor/imaging‐surrogate within the pre‐configured breath‐hold window in the AP direction. Fifty fractions of Ethos RT were delivered under surface image‐guidance: Thirty‐two fractions with CT‐STAR (adaptive RT) and 18 fractions with CT‐SBRT (non‐adaptive RT). The residual motion of the tumor was quantified by determining variations in the tumor centroid position. The dosimetric impact on target coverage was calculated based on the residual motion. Results: We used 46 fractions for the analysis of intra‐fractional residual motion and 43 fractions for the inter‐fractional motion analysis due to study constraints. Using the image registration method, 43 pairs of inter‐fractional CBCTs and 100 intra‐fractional CBCTs attached to dose maps were analyzed. In the motion range study (image registration) from the inter‐fractional CBCTs, the primary motion (mean ± std) was 16.6 ± 9.2 mm in the SI direction (magnitude: 26.4 ± 11.3 mm) for the tumors and 15.5 ± 7.3 mm in the AP direction (magnitude: 20.4 ± 7.0 mm) for the imaging‐surrogate, respectively. The residual motion of the tumor (image registration) from intra‐fractional breath‐hold CBCTs was 2.2 ± 2.0 mm for SI, 1.4 ± 1.4 mm for RL, and 1.3 ± 1.3 mm for AP directions (magnitude: 3.5 ± 2.1 mm). The ratio of the actual dose coverage to 99%, 90%, and 50% of the target volume decreased by 0.95 ± 0.11, 0.96 ± 0.10, 0.99 ± 0.05, respectively. The mean percentage of the target volume covered by the prescribed dose decreased by 2.8 ± 4.4%. Conclusion: We demonstrated the intra‐fractional motion‐managed treatment strategy in breath‐hold Ethos CT‐STAR/SBRT using optical surface imaging and CBCT. While the controlled residual tumor motion measured at 3.5 mm exceeded the predetermined setup value of 2 mm, it is important to note that this motion still fell within the clinically acceptable range defined by the PTV margin of 5 mm. Nonetheless, additional caution is needed with intra‐fractional motion management in breath‐hold Ethos CT‐STAR/SBRT using optical surface imaging and CBCT. [ABSTRACT FROM AUTHOR]

Purpose: The feasibility of a deep learning‐based markerless real‐time tumor tracking (RTTT) method was retrospectively studied with orthogonal kV X‐ray images and clinical tracking records acquired during lung cancer treatment. Methods: Ten patients with lung cancer treated with marker‐implanted RTTT were included. The prescription dose was 50 Gy in four fractions, using seven‐ to nine‐port non‐coplanar static beams. This corresponds to 14–18 X‐ray tube angles for an orthogonal X‐ray imaging system rotating with the gantry. All patients underwent 10 respiratory phases four‐dimensional computed tomography. After a data augmentation approach, for each X‐ray tube angle of a patient, 2250 digitally reconstructed radiograph (DRR) images with gross tumor volume (GTV) contour labeled were obtained. These images were adopted to train the patient and X‐ray tube angle‐specific GTV contour prediction model. During the testing, the model trained with DRR images predicted GTV contour on X‐ray projection images acquired during treatment. The predicted three‐dimensional (3D) positions of the GTV were calculated based on the centroids of the contours in the orthogonal images. The 3D positions of GTV determined by the marker‐implanted RTTT during the treatment were considered as the ground truth. The 3D deviations between the prediction and the ground truth were calculated to evaluate the performance of the model. Results: The median GTV volume and motion range were 7.42 (range, 1.18–25.74) cm3 and 22 (range, 11–28) mm, respectively. In total, 8993 3D position comparisons were included. The mean calculation time was 85 ms per image. The overall median value of the 3D deviation was 2.27 (interquartile range: 1.66–2.95) mm. The probability of the 3D deviation smaller than 5 mm was 93.6%. Conclusions: The evaluation results and calculation efficiency show the proposed deep learning‐based markerless RTTT method may be feasible for patients with lung cancer. [ABSTRACT FROM AUTHOR]

Background and purpose: In lung Stereotactic Body Radiotherapy (SBRT) respiratory management is used to reduce target motion due to respiration. This study aimed (1) to estimate intrafraction shifts through a Cone Beam Computed Tomography (CBCT) acquired during the first treatment arc when deep inspiration breath-hold (DIBH) was performed using spirometry-based (SB) or surface-guidance (SG) systems and (2) to analyze the obtained results depending on lesion localization. Material and methods: A sample of 157 patients with 243 lesions was analyzed. A total of 860 and 410 fractions were treated using SB and SG. Averaged intrafraction shifts were estimated by the offsets obtained when registering a CBCT acquired during the first treatment arc with the planning CT. Offsets were recorded in superior-inferior (SI), left–right (LR) and anterior-posterior (AP). Significance tests were applied to account for differences in average offsets and variances between DIBH systems. Systematic and random errors were computed. Results: Average offset moduli were 2.4 ± 2.2 mm and 3.5 ± 2.6 mm for SB and SG treatments (p 0.3). However, variances were statistically smaller for SB than for SG (p

Background: For delivering high radiation doses to pancreatic tumors, organ motion management is indispensable; however, studies on this are limited. We aimed to evaluate the efficacy and safety of dynamic tumor tracking (DTT) moderately hypofractionated intensity-modulated radiotherapy (IMRT) in patients with locally advanced pancreatic cancer (LAPC)., Methods: Patients with histological confirmation for LAPC were included. A linac system, which was mounted with a gimbal function, was used for DTT-IMRT. The prescribed dose was 48 Gy in 15 fractions. The primary endpoint was the 1-year rate of freedom from locoregional progression (FFLP)., Results: DTT-IMRT was successfully administered in 25 patients enrolled from four institutions. The median range of respiratory motion during DTT-IMRT was 9.8 mm (range: 3.5-27.3 mm), and the median tracking accuracy was 2.6 mm (range: 0.7-5.2 mm). With a median follow-up period of 13.9 months, the 1-year FFLP rate was 75.3% (lower limit of one-sided 80% confidence interval [CI]: 60.2%), which satisfied the predetermined primary endpoint. One-year locoregional progression-free survival, progression-free survival, and overall survival were 56.0% (95% CI: 34.8%-72.7%), 44.0% (95% CI: 24.5%-61.9%), and 60.0% (95% CI: 38.4%-76.1%), respectively. Regarding nonhematologic toxicities, grade 3 acute gastrointestinal (GI) toxicity was observed in two patients (8%), and two patients (8%) each experienced grade 3 late GI and non-GI toxicities. No grade 4 or 5 nonhematologic toxicities were observed., Conclusions: DTT moderately hypofractionated IMRT shows preferable locoregional control without significant toxicity in patients with LAPC., Trial Registration: UMIN000017521., (© 2025 The Author(s). Cancer Medicine published by John Wiley & Sons Ltd.)

Purpose: To quantify the clinical practice of respiratory motion management in radiation oncology. Methods: A respiratory motion management survey was designed and conducted based on clinician survey guidelines. The survey was administered to American Association of Physicists in Medicine (AAPM) members on 17 August 2020 and closed on 13 September 2020. Results: A total of 527 respondents completed the entire survey and 651 respondents completed part of the survey, with the partially completed surveys included in the analysis. Overall, 84% of survey respondents used deep inspiration breath hold for left‐sided breast cancer. Overall, 83% of respondents perceived respiratory motion management for thoracic and abdominal cancer radiotherapy patients to be either very important or required. Overall, 95% of respondents used respiratory motion management for thoracic and abdominal sites, with 36% of respondents using respiratory motion management for at least 90% of thoracic and abdominal patients. The majority (60%) of respondents used the internal target volume method to treat thoracic and abdominal cancer patients, with 25% using breath hold or abdominal compression and 13% using gating or tracking. Conclusions: A respiratory motion management survey has been completed by AAPM members. Respiratory motion management is generally considered very important or required and is widely used for breast, thoracic, and abdominal cancer treatments. [ABSTRACT FROM AUTHOR]

Stereotactic body radiotherapy, a hypofractionated radiation therapy method with fewer fractions and a large single radiation dose, is the preferred method for treating patients with early-stage non-small cell lung cancer who are clinically unsuitable for or refuse surgery. Accuracy and repeatability requirements of the target position are, therefore, necessary. In view of this, adjuvant treatments such as image-guided and respiratory motion management technology and immobilization devices are used clinically to reduce the impact of respiratory motion. This paper summarizes the research status of these approaches and proposes future directions based on the problems existing in each technology.

Background: Recent advances in stereotactic body radiation therapy (SBRT) technology for early-stage peripheral lung cancer have been remarkable and are becoming a viable alternative to surgery. However, the most important problem in performing SBRT correctly is minimizing the respiratory motion of the tumor., Materials and Methods: Thirty-eight patients treated with SBRT were evaluated to clarify factors affecting respiratory motion of early-stage peripheral lung cancer in the management of restrictive breathing technique (abdominal compression) to reduce respiratory tumor motion in SBRT. We investigated age, gender, body mass index (BMI), Brinkman index (BI), forced expiratory volume in 1 second (FEV 1.0), and type of ventilatory impairment as patient factors, and T-factor, stage, tumor-bearing lung lobe, and tumor pathology as tumor factors. Respiratory motion was assessed by volume differences between clinical target volume (CTV) and internal target volume (ITV). The degree of tumor motion due to respiration was compared using the formula of (ITV-CTV)/CTV as an index., Results: In the results, univariate analyses showed that only age was a significant predictor of respiratory tumor motion (p = 0.048). In multi-variate analyses, only T factor was an independent significant predictor of respiratory tumor motion (p = 0.045), while there was a significant trend for age (p = 0.061), and tumor location (p = 0.067)., Conclusions: In late elderly patients or T1a tumor, respiratory motion in early-stage peripheral lung cancer was significantly large. However, it is not predictable by patient and tumor characteristics. Therefore, respiratory motion of the tumor should be measured in all patients in some way., Competing Interests: Conflict of interests: The authors declare no conflict of interests., (© 2024 Greater Poland Cancer Centre.)

Purpose: Ethos adaptive radiotherapy (ART) is emerging with AI‐enhanced adaptive planning and high‐quality cone‐beam computed tomography (CBCT). Although a respiratory motion management solution is critical for reducing motion artifacts on abdominothoracic CBCT and improving tumor motion control during beam delivery, our institutional Ethos system has not incorporated a commercial solution. Here we developed an institutional visually guided respiratory motion management system to coach patients in regular breathing or breath hold during intrafractional CBCT scans and beam delivery with Ethos ART. Methods: The institutional visual‐guidance respiratory motion management system has three components: (1) a respiratory motion detection system, (2) an in‐room display system, and (3) a respiratory motion trace management software. Each component has been developed and implemented in the clinical Ethos ART workflow. The applicability of the solution was demonstrated in installation, routine QA, and clinical workflow. Results: An air pressure sensor has been utilized to detect patient respiratory motion in real time. Either a commercial or in‐house software handled respiratory motion trace display, collection and visualization for operators, and visual guidance for patients. An extended screen and a projector on an adjustable stand were installed as the in‐room visual guidance solution for the closed‐bore ring gantry medical linear accelerator utilized by Ethos. Consistent respiratory motion traces and organ positions on intrafractional CBCTs demonstrated the clinical suitability of the proposed solution in Ethos ART. Conclusion: The study demonstrated the utilization of an institutional visually guided respiratory motion management system for Ethos ART. The proposed solution can be easily applied for Ethos ART and adapted for use with any closed bore‐type system, such as computed tomography and magnetic resonance imaging, through incorporation with appropriate respiratory motion sensors. [ABSTRACT FROM AUTHOR]

Deep inspiration breath hold (DIBH) is a common method used worldwide for reducing the radiation dose to the heart. However, few studies have reported on the relationship between dose reduction and patient-specific parameters. The aim of this study was to compare the reductions of heart dose and volume using DIBH with the dose/volume of free breathing (FB) for patients with left-sided breast cancer and to analyse patient-specific dose reduction parameters. A total of 85 Asian patients who underwent whole-breast radiotherapy after breast-conserving surgery were recruited. Treatment plans for FB and DIBH were retrospectively generated by using an automated breast planning tool with a two-field tangential intensity-modulated radiation therapy technique. The prescribed dose was 50 Gy in 25 fractions. The dosimetric parameters (e.g., mean dose and maximum dose) in heart and lung were extracted from the dose–volume histogram. The relationships between dose–volume data and patient-specific parameters, such as age, body mass index (BMI), and inspiratory volume, were analyzed. The mean heart doses for the FB and DIBH plans were 1.56 Gy and 0.75 Gy, respectively, a relative reduction of 47%. There were significant differences in all heart dosimetric parameters (p  < 0.001). For patients with a high heart dose in the FB plan, a relative reduction of the mean heart dose correlated with inspiratory volume (r  = 0.646). There was correlation between the relative reduction of mean heart dose and BMI (r  = −0.248). We recommend considering the possible feasibility of DIBH in low BMI patients because the degree of benefit from DIBH varied with BMI. [ABSTRACT FROM AUTHOR]

To evaluate the target dose coverage for lung stereotactic body radiotherapy (SBRT) using helical tomotherapy (HT) with the internal tumor volume (ITV) margin settings adjusted according to the degree of tumor motion. Lung SBRT with HT may cause a dosimetric error when the target motion is large. Two lung SBRT plans were created using a tomotherapy planning station. Using these original plans, five plans with different ITV margins (4.0–20.0 mm for superior-inferior [SI] dimension) were generated. To evaluate the effects of respiratory motion on HT, an original dynamic motion phantom was developed. The respiratory wave of a healthy volunteer was used for dynamic motion as the typical tumor respiratory motion. Five patterns of motion amplitude that corresponded to five ITV margin sizes and three breathing cycles of 7, 14, and 28 breaths per minute were used. We evaluated the target dose change between a static delivery and a dynamic delivery with each motion pattern. The target dose difference increased as the tumor size decreased and as the tumor motion increased. Although a target dose difference of <5 % was observed at ≤10 mm of tumor motion for each condition, a maximum difference of -9.94 % ± 7.10 % was observed in cases of small tumors with 20 mm of tumor motion under slow respiration. Minimizing respiratory movement is recommended as much as possible for lung SBRT with HT, especially for cases involving small tumors. [ABSTRACT FROM AUTHOR]

Purpose: To quantify the effects of combining layer‐based repainting and respiratory gating as a strategy to mitigate the dosimetric degradation caused by the interplay effect between a moving target and dynamic spot‐scanning proton delivery. Methods: An analytic routine modeled three‐dimensional dose distributions of pencil‐beam proton plans delivered to a moving target. Spot positions and weights were established for a single field to deliver 100 cGy to a static, 15‐cm deep, 3‐cm radius spherical clinical target volume with a 1‐cm isotropic internal target volume expansion. The interplay effect was studied by modeling proton delivery from a clinical synchrotron‐based spot scanning system and respiratory target motion, patterned from surrogate patient breathing traces. Motion both parallel and orthogonal to the beam scanning direction was investigated. Repainting was modeled using a layer‐based technique. For each of 13 patient breathing traces, the dose from 20 distinct delivery schemes (combinations of four gate window amplitudes and five repainting techniques) was computed. Delivery strategies were inter‐compared based on target coverage, dose homogeneity, high dose spillage, and delivery time. Results: Notable degradation and variability in plan quality were observed for ungated delivery. Decreasing the gate window reduced this variability and improved plan quality at the expense of longer delivery times. Dose deviations were substantially greater for motion orthogonal to the scan direction when compared with parallel motion. Repainting coupled with gating was effective at partially restoring dosimetric coverage at only a fraction of the delivery time increase associated with very small gate windows alone. Trends for orthogonal motion were similar, but more complicated, due to the increased severity of the interplay. Conclusions: Layer‐based repainting helps suppress the interplay effect from intra‐gate motion, with only a modest penalty in delivery time. The magnitude of the improvement in target coverage is strongly influenced by individual patient breathing patterns and the tumor motion trajectory. [ABSTRACT FROM AUTHOR]

Introduction: Stereotactic body radiotherapy (SBRT) has emerged as an important modality in malignant lung tumor treatment both in early localized primary and oligometastatic setting. This study aims to present the results of lung SBRT both in terms of dosimetry and clinical outcome.Materials and Methods: Twenty-seven patients were assessed from 2012 to 2016. Both the primary and oligometastatic lung tumors were evaluated. Respiratory motion management was done employing ANZAI (Siemens, Germany) based four-dimensional computed tomography (CT). Commonly used fractionations were 60 Gy/5 fractions for peripheral tumors and 48 Gy/6 fractions for central tumors. Radiation Therapy Oncology Group toxicity criteria were used for toxicity and whole-body positron emission tomography-CT scan was done at follow-up for response evaluation.Results: Twenty-seven patients were evaluated, 18 (66.7%) patients had a primary, and 9 (33.3%) patients had metastatic lung tumors. The male-to-female ratio for the entire cohort was 2:1. The median age at diagnosis was 65.8 years. Mean planning target volume (PTV) D2cc was 54.9 ± 9.04 Gy and mean internal target volume diameter was 3.0 ± 1.07 cm. Mean V20 Gy, V10 Gy, and V5 Gy of (lungs total-PTV) and (Lung ipsilateral - PTV) were 5.4 ± 4% and 10.9 ± 7.9%, 11.7 ± 5.8% and 24.2 ± 14.0%, and 22.05 ± 12.4% and 33.2 ± 15.3%, respectively. In total 21 (84%) patients and 4 patients (16%) showed a complete and partial response, respectively. One (3%) patient developed Gr 3 radiation pneumonitis. One year local control was in 18 (81%) patients whereas 4 (14%) patients progressed and three patients did not report. A higher prescribed dose significantly correlated with 1 year tumor control (P = 0.036).Conclusion: This study infers the feasibility and a favorable outcome for lung cancer amenable to SBRT in addition to being one of the largest clinical experiences for lung stereotactic treatment in our country. [ABSTRACT FROM AUTHOR]

Purpose Respiratory motion-management techniques (MMT) aim to ensure tumor dose coverage while sparing lung tissue. Dynamic treatment-couch tracking of the moving tumor is a promising new MMT and was compared to the internal-target-volume (ITV) concept, the mid-ventilation (MidV) principle and the gating approach in a planning study based on 4D dose calculations. Methods For twenty patients with lung lesions, planning target volumes (PTV) were adapted to the MMT and stereotactic body radiotherapy treatments were prepared with the 65%-isodose enclosing the PTV. For tracking, three concepts for target volume definition were considered: Including the gross tumor volume of one phase (single-phase tracking), including deformations between phases (multi-phase tracking) and additionally including tracking latencies of a couch tracking system (reliable couch tracking). The accumulated tumor and lung doses were estimated with 4D dose calculations based on 4D-CT datasets and deformable image registration. Results Single-phase tracking showed the lowest ipsilateral lung Dmean (median: 3.3 Gy), followed by multi-phase tracking, gating, reliable couch tracking, MidV and ITV concepts (3.6, 3.8, 4.1, 4.3 and 4.8 Gy). The 4D dose calculations showed the MidV and single-phase tracking overestimated the target mean dose (−2.3% and −1.3%), while it was slightly underestimated by the other MMT (<+1%). Conclusion The ITV concept ensures tumor coverage, but exposes the lung tissue to a higher dose. The MidV, gating and tracking concepts were shown to reduce the lung dose. Neglecting non-translational changes of the tumor in the target volume definition for tracking results in a slightly reduced target coverage. The slightly inferior dose coverage for MidV should be considered when applying this technique clinically. [ABSTRACT FROM AUTHOR]

Background and purpose The objective of this study was to compare the latest respiratory motion-management strategies, namely the internal-target-volume (ITV) concept, the mid-ventilation (MidV) principle, respiratory gating and dynamic couch tracking. Materials and methods An anthropomorphic, deformable and dynamic lung phantom was used for the dosimetric validation of these techniques. Stereotactic treatments were adapted to match the techniques and five distinct respiration patterns, and delivered to the phantom while radiographic film measurements were taken inside the tumor. To report on tumor coverage, these dose distributions were used to calculate mean doses ( D mean ), changes in homogeneity indices (Δ H 2 - 98 ), gamma agreement, and areas covered by the planned minimum dose ( A >Dmin ). Results All techniques achieved good tumor coverage ( A >Dmin > 99.0%) and minor changes in D mean (±3.2%). Gating and tracking strategies showed superior results in gamma agreement and Δ H 2 - 98 compared to ITV and MidV concepts, which seem to be more influenced by the interplay and the gradient effect. For lung, heart and spinal cord, significant dose differences between the four techniques were found ( p < 0.05), with lowest doses for gating and tracking strategies. Conclusion Active motion-management techniques, such as gating or tracking, showed superior tumor dose coverage and better organ dose sparing than the passive techniques based on tumor margins. [ABSTRACT FROM AUTHOR]

Background: Dynamic tumor tracking (DTT) is a method of respiratory motion management in radiotherapy. It reduces the radiation field but risks delivering an insufficient radiation dose to the tumor. We investigated the local control of DTT-stereotactic body radiotherapy (SBRT) for lung tumors., Methods: Patients treated with SBRT for early-stage, non-small-cell lung cancer and lung metastases (2013-18) were retrospectively reviewed. Patients with tumor motion >1 cm were treated with DTT-SBRT (DTT group); those with tumor motion ≤1 cm were treated with static-SBRT (static group). A static planning target volume for the static-SBRT plan was also created for patients in the DTT group, and planning target volume reduction relative to the planning target volume for the DTT-SBRT plan was assessed. Patients were matched in a 1:1 ratio using a propensity score predictive of the SBRT technique., Results: Of the 245 lesions in 218 patients (median follow-up, 25.4 months), 69 were treated with DTT-SBRT and 176 with static-SBRT. The median planning target volume reduction in the DTT group was 30.3%. After propensity score matching, 124 lesions were included (62 per group). Two-year local control rates for the DTT and static groups were 94.2 and 95.9%, respectively, for all lesions (P = 0.19) and 96.3 and 94.5%, respectively, for matched lesions (P = 0.79). In univariate analysis, DTT-SBRT was not associated with local control for all lesions (hazard ratio, 2.06; P = 0.20) or matched lesions (hazard ratio, 1.22; P = 0.79). No grade 4/5 toxicities were observed., Conclusions: DTT-SBRT for lung tumors reduced the planning target volume, but not local control rates. DTT was useful for respiratory motion management., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

A four-dimensional magnetic resonance imaging (4-D-MRI) technique with Sagittal-Coronal-Diaphragm Point-of-Intersection (SCD-PoI) as a respiratory surrogate is proposed. To develop an image-based respiratory surrogate, the SCD-PoI motion tracking method is used for retrospective 4-D-MRI reconstruction. Single-slice sagittal MR cine was acquired at a location near the center of the diaphragmatic dome. Multiple-slice coronal MR cines were acquired for 4-D-MRI reconstruction. As a motion surrogate, the diaphragm motion was measured from the PoI among the sagittal MRI cine plane, coronal MRI cine planes, and the diaphragm surface. These points were defined as the SCD-PoI. This point is used as a one-dimensional diaphragmatic navigator in our study. The 4-D-MRI technique was evaluated on a 4-D digital extended cardiac-torso (XCAT) human phantom, a motion phantom, and seven human subjects (five healthy volunteers and two cancer patients). Motion trajectories of a selected region of interest were measured on 4-D-MRI and compared with the known XCAT motion that served as references. The mean absolute amplitude difference ([Formula: see text]) and the cross-correlation coefficient (CC) of the comparisons were determined. 4-D-MRI of the XCAT phantom demonstrated highly accurate motion information ([Formula: see text], [Formula: see text]). Motion trajectories of the motion phantom measured on 4-D-MRI matched well with the references ([Formula: see text], [Formula: see text]). 4-D-MRI of human subjects showed minimal artifacts and clearly revealed the respiratory motion of organs and tumor (mean [Formula: see text]; mean [Formula: see text]). A 4-D-MRI technique with image-based respiratory surrogate has been developed and tested on phantoms and human subjects.