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Background: Stereotactic ablative body radiation (SABR) is a well‐recognized treatment option for hepatocellular carcinoma (HCC). Due to the inherent motion of liver tumors, effective motion management is crucial for successful SABR. In the motion‐encompassing motion management technique, all 10 respiratory phase image datasets are delineated and designated as the internal target volume (ITV). Some treatment centers use single or combination image sets to delineate the target volume. This study determines which specialty image set most closely matches an all‐phase ITV contour on a synchronized contrast‐enhanced 4DCT. Materials and methods: Synchronized 4DCT contrast and delayed scans were acquired for 10 patients in the study. The maximum intensity projection (MiP), average intensity projection (AvgIP), and minimum intensity projection (MinIP) images were generated. The ITV delineation was done in all 10 phases (ITV_all_phase). The ITV_2phase combines the peak inhale and exhale phase, ITV_2 M combines MiP and MinIP, and ITV_3 M combines MiP, MinIP, and AvgIP. All ITVs were compared to ITV_all_phase with Dice similarity index (DSI) and volumes. Results: Using ITV_all_phase as the reference, the DSI and the mean ITV volumes for the different ITVs were as follows: ITV_all_phase (1 and 116.69 cc), ITV_2phase (0.87 and 105.27 cc), MiP (0.76 and 98.24 cc), AvgIP (0.72 and 94.54 cc), ITV_MinIP (0.67 and 81.08 cc), ITV_2 M (0.84 and 106.26 cc), and ITV_3 M (0.86 and 112.51 cc). Conclusion: The study demonstrates that in the motion‐encompassing technique of motion management, the target volume generated by delineating all phases of 4DCT provides the most accurate representation for patients with HCC. Specialty image sets and their combinations, while sometimes close, tend to result in less accurate targeting. Hence, the all‐phase 4DCT method should be preferred to avoid geographical misses and ensure optimal treatment outcomes. However, our conclusion may be limited by the technique we employed. [ABSTRACT FROM AUTHOR]

Radiotherapy (RT) for lung or liver tumors can be challenging due to respiration‐induced organ motion (RIOM). There are some methodological solutions to minimize RIOM. We explored a new approach to evaluate the feasibility and reproducibility of RIOM during RT with five total client‐owned tumor‐bearing animals using a remote‐triggered breath‐hold ventilator under general anesthesia during image acquisition and RT. There was one stereotactic body radiotherapy, one conventionally fractionated definitive intent, and three conventionally fractionated palliative intent RT cases. Based on repeated cone beam CT, there were no treatment table shifts required prior to initiating beam on. No clinically significant complications such as hypotension occurred during anesthesia. This technique appeared to be safe in this group of patients and was easily clinically implemented and highly reproducible. More complete follow‐up data and larger studies are needed to evaluate clinical outcomes with this breath‐hold ventilator technique in veterinary RT. [ABSTRACT FROM AUTHOR]

Introduction: Organ motion (OM) and volumetric changes pose challenges in radiotherapy (RT) for locally advanced cervical cancer (LACC). Magnetic Resonance-guided Radiotherapy (MRgRT) combines improved MRI contrast with adaptive RT plans for daily anatomical changes. Our goal was to analyze cervico-uterine structure (CUS) changes during RT to develop strategies for managing OM. Materials and methods: LACC patients received chemoradiation by MRIdian system with a simultaneous integrated boost (SIB) protocol. Prescription doses of 55–50.6 Gy at PTV1 and 45–39.6 Gy at PTV2 were given in 22 and 25 fractions. Daily MRI scans were co-registered with planning scans and CUS changes were assessed.Six PTVs were created by adding 0.5, 0.7, 1, 1.3, 1.5, and 2 cm margins to the CUS, based on the simulation MRI. Adequate margins were determined to include 95 % of the CUSs throughout the entire treatment in 95 % of patients. Results: Analysis of 15 LACC patients and 372 MR scans showed a 31 % median CUS volume decrease. Asymmetric margins of 2 cm cranially, 0.5 cm caudally, 1.5 cm posteriorly, 2 cm anteriorly, and 1.5 cm on both sides were optimal for PTV, adapting to CUS variations. Post-14th fraction, smaller margins of 0.7 cm cranially, 0.5 cm caudally, 1.3 cm posteriorly, 1.3 cm anteriorly, and 1.3 cm on both sides sufficed. Conclusion: CUS mobility varies during RT, suggesting reduced PTV margins after the third week. MRgRT with adaptive strategies optimizes dose delivery, emphasizing the importance of streamlined IGRT with reduced PTV margins using a tailored MRgRT workflow with hybrid MRI-guided systems.

BackgroundIn magnetic resonance (MR)-guided thermal therapy, respiratory motion can cause a significant temperature error in MR thermometry and reduce the efficiency of the treatment. A respiratory motion simulator is necessary for the development of new MR imaging (MRI) and motion compensation techniques.PurposeThe purpose of this study is to develop a low-cost and simple MR-compatible respiratory motion simulator to support proof-of-concept studies of MR monitoring approaches with respiratory-induced abdominal organ motion.MethodsThe phantom motion system integrates pneumatic control via an actuator subsystem located outside the MRI and coupled via plastic tubing to a compressible bag for distention and retraction within the MRI safe motion subsystem and phantom positioned within the MRI scanner. Performance of the respiratory motion simulator was evaluated with a real-time gradient echo MRI pulse sequence.ResultsThe motion simulator can produce respiratory rates in the range of 8-16 breaths/min. Our experiments showed the consistent periodic motion of the phantom during MRI acquisition in the range of 3.7-9 mm with 16 breaths/min. The operation of the simulator did not cause interference with MRI acquisition.ConclusionsIn this study, we have demonstrated the ability of the motion simulator to generate controlled respiratory motion of a phantom. The low-cost MR-compatible respiratory motion simulator can be easily constructed from off-the-shelf and 3D-printed parts based on open-source 3D models and instructions. This could lower the barriers to the development of new MRI techniques with motion compensation.

Abstract Background For accurate thoracic and abdominal radiotherapy, inter- and intrafractional geometrical uncertainties need to be considered to enable accurate margin sizes. We aim to quantify interfractional diaphragm and abdominal organ position variations, and intrafractional diaphragm motion in a large multicenter cohort of pediatric cancer patients (

Background and purpose: Imaging of respiration-induced anatomical changes is essential to ensure high accuracy in radiotherapy of lung cancer. We expanded here on methods for retrospective reconstruction of time-resolved volumetric magnetic resonance (4DMR) of the thoracic region and benchmarked the results against 4D computed tomography (4DCT). Materials and method: MR data of six lung cancer patients were collected by interleaving cine-navigator images with 2D data frame images, acquired across the thorax. The data frame images have been stacked in volumes based on a similarity metric that considers the anatomical deformation of lungs, while addressing ambiguities in respiratory phase detection and interpolation of missing data. The resulting images were validated against cine-navigator images and compared to paired 4DCTs in terms of amplitude and period of motion, assessing differences in internal target volume (ITV) margin definition. Results: 4DMR-based motion amplitude was on average within 1.8 mm of that measured in the corresponding 2D cine-navigator images. In our dataset, the 4DCT motion and the 4DMR median amplitude were always within 3.8 mm. The median period was generally close to CT references, although deviations up to 24 % have been observed. These changes were reflected in the ITV, which was generally larger for MRI than for 4DCT (up to 39.7 %). Conclusions: The proposed algorithm for retrospective reconstruction of time-resolved volumetric MR provided quality anatomical images with high temporal resolution for motion modelling and treatment planning. The potential for imaging organ motion variability makes 4DMR a valuable complement to standard 4DCT imaging.

Objective. Investigating the aspects of proton beam delivery to track organ motion with pencil beam scanning therapy. Considering current systems as a reference, specify requirements for next-generation units aiming at real-time image-guided treatments. Approach. Proton treatments for six non-small cell lung cancer (NSCLC) patients were simulated using repeated 4DCTs to model respiratory motion variability. Energy corrections required for this treatment site were evaluated for different approaches to tumour tracking, focusing on the potential for energy adjustment within beamline momentum acceptance (d p / p). A respiration-synchronised tracking, taking into account realistic machine delivery limits, was compared to ideal tracking scenarios, in which unconstrained energy corrections are possible. Rescanning and the use of multiple fields to mitigate residual interplay effects and dose degradation have also been investigated. Main results. Energy correction requirements increased with motion amplitudes, for all patients and tracking scenarios. Higher dose degradation was found for larger motion amplitudes, rescanning has beneficial effects and helped to improve dosimetry metrics for the investigated limited d p / p of 1.2% (realistic) and 2.4%. The median differences between ideal and respiratory-synchronised tracking show minimal discrepancies, 1% and 5% respectively for dose coverage (CTV V95) and homogeneity (D5-D95). Multiple-field planning improves D5-D95 up to 50% in the most extreme cases while it does not show a significant effect on V95. Significance. This work shows the potential of implementing tumour tracking in current proton therapy units and outlines design requirements for future developments. Energy regulation within momentum acceptance was investigated to tracking tumour motion with respiratory-synchronisation, achieving results in line with the performance of ideal tracking scenarios. ±5% Δ p /p would allow to compensate for all range offsets in our NSCLC patient cohort, including breathing variability. However, the realistic momentum of 1.2% d p / p representative of existing medical units limitations, has been shown to preserve plan quality. [ABSTRACT FROM AUTHOR]

Introduction: With the global prevalence of coronavirus disease 2019 (COVID-19), an increasing number of people are experiencing respiratory discomfort. Respiratory biomechanics can monitor breathing patterns and respiratory movements and it is easier to prevent, diagnose, treat or rehabilitate. However, there is still a lack of global knowledge structure in the field of respiratory biomechanics. With the help of CiteSpace software, we aim to help researchers identify potential collaborators and collaborating institutions, hotspots and research frontiers in respiratory biomechanics. Methods: Articles on respiratory biomechanics from 2003 to 2022 were retrieved from the Web of Science Core Collection by using a specific strategy, resulting a total of 2,850 publications. We used CiteSpace 6.1.R6 to analyze the year of publication, journal/journals cited, country, institution, author/authors cited, references, keywords and research trends. Co-citation maps were created to visually observe research hot spots and knowledge structures. Results and discussion: The number of annual publications gradually increased over the past 20 years. Medical Physics published the most articles and had the most citations in this study. The United States was the most influential country, with the highest number and centrality of publications. The most productive and influential institution was Harvard University in the United States. Keall PJ was the most productive author and MCCLELLAND JR was the most cited authors The article by Keall PJ (2006) article (cocitation counts: 55) and the article by McClelland JR (2013) were the most representative and symbolic references, with the highest cocitation number and centrality, respectively. The top keywords were “radiotherapy”, “volume”, and “ventilation”. The top Frontier keywords were “organ motion,” “deep inspiration,” and “deep learning”. The keywords were clustered to form seven labels. Currently, the main area of research in respiratory biomechanics is respiratory motion related to imaging techniques. Future research may focus on respiratory assistance techniques and respiratory detection techniques. At the same time, in the future, we will pay attention to personalized medicine and precision medicine, so that people can monitor their health status anytime and anywhere. [ABSTRACT FROM AUTHOR]

Background: For accurate thoracic and abdominal radiotherapy, inter- and intrafractional geometrical uncertainties need to be considered to enable accurate margin sizes. We aim to quantify interfractional diaphragm and abdominal organ position variations, and intrafractional diaphragm motion in a large multicenter cohort of pediatric cancer patients (< 18 years). We investigated the correlation of interfractional position variations and intrafractional motion with age, and with general anesthesia (GA). Methods: In 189 children (mean age 8.1; range 0.4–17.9 years) from six institutes, interfractional position variation of both hemidiaphragms, spleen, liver, left and right kidneys was quantified using a two-step registration. CBCTs were registered to the reference CT relative to the bony anatomy, followed by organ registration. We calculated the group mean, systematic and random errors (standard deviations Σ and σ, respectively) in cranial-caudal (CC), left-right and anterior-posterior directions. Intrafractional right hemidiaphragm motion was quantified using CBCTs on which the breathing amplitude, defined as the difference between end-inspiration and end-expiration peaks, was assessed (N = 79). We investigated correlations with age (Spearman's ρ), and differences in motion between patients treated with and without GA (N = 75; all < 5.5 years). Results: Interfractional group means were largest in CC direction and varied widely between patients, with largest variations in the right hemidiaphragm (range -13.0–17.5 mm). Interfractional group mean of the left kidney showed a borderline significant correlation with age (p = 0.047; ρ = 0.17). Intrafractional right hemidiaphragm motion in patients ≥ 5.5 years (mean 10.3 mm) was significantly larger compared to patients < 5.5 years treated without GA (mean 8.3 mm) (p = 0.02), with smaller Σ and σ values. We found a significant correlation between breathing amplitude and age (p < 0.001; ρ = 0.43). Interfractional right hemidiaphragm position variations were significantly smaller in patients < 5.5 years treated with GA than without GA (p = 0.004), but intrafractional motion showed no significant difference. Conclusion: In this large multicenter cohort of children undergoing thoracic and abdominal radiotherapy, we found that interfractional position variation does not depend on age, but the use of GA in patients < 5.5 years showed smaller systematic and random errors. Furthermore, our results showed that breathing amplitude increases with age. Moreover, variations between patients advocate the need for a patient-specific margin approach. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to evaluate the intrafractional prostate motion captured during gated magnetic resonance imaging (MRI)-guided online adaptive radiotherapy for prostate cancer and analyze its impact on the delivered dose as well as the effect of gating. Methods: Sagittal 2D cine-MRI scans were acquired at 4 Hz during treatment at a ViewRay MRIdian (ViewRay Inc., Oakwood Village, OH, USA) MR linac. Prostate shifts in anterior–posterior (AP) and superior–inferior (SI) directions were extracted separately. Using the static dose cloud approximation, the planned fractional dose was shifted according to the 2D gated motion (residual motion in gating window) to estimate the delivered dose by superimposing and averaging the shifted dose volumes. The dose of a hypothetical non-gated delivery was reconstructed similarly using the non-gated motion. For the clinical target volume (CTV), rectum, and bladder, dose–volume histogram parameters of the planned and reconstructed doses were compared. Results: In total, 174 fractions (15.7 h of cine-MRI) from 10 patients were evaluated. The average (±1 σ) non-gated prostate motion was 0.6 ± 1.0 mm in the AP and 0.0 ± 0.6 mm in the SI direction with respect to the centroid position of the gating boundary. 95% of the shifts were within [−3.5, 2.7] mm in the AP and [−2.9, 3.2] mm in the SI direction. For the gated treatment and averaged over all fractions, CTV D98% decreased by less than 2% for all patients. The rectum and the bladder D2% increased by less than 3% and 0.5%, respectively. Doses reconstructed for gated and non-gated delivery were similar for most fractions. Conclusion: A pipeline for extraction of prostate motion during gated MRI-guided radiotherapy based on 2D cine-MRI was implemented. The 2D motion data enabled an approximate estimation of the delivered dose. For the majority of fractions, the benefit of gating was negligible, and clinical dosimetric constraints were met, indicating safety of the currently adopted gated MRI-guided treatment workflow. [ABSTRACT FROM AUTHOR]

Background: Rapid kV cone-beam computed tomography (CBCT) scans are achievable in under 20 s on select linear accelerator systems to generate volumetric images in three dimensions (3D). Daily pre-treatment four-dimensional CBCT (4DCBCT) is recommended in image-guided lung radiotherapy to mitigate the detrimental effects of respiratory motion on treatment quality. Purpose: To demonstrate the potential for thoracic 4DCBCT reconstruction using projection data that was simulated using a clinical rapid 3DCBCT acquisition protocol. Methods: We simulated conventional (1320 projections over 4 min) and rapid (491 projections over 16.6 s) CBCT acquisitions using 4D computed tomography (CT) volumes of 14 lung cancer patients. Conventional acquisition data were reconstructed using the 4D Feldkamp-Davis-Kress (FDK) algorithm. Rapid acquisition data were reconstructed using 3DFDK, 4DFDK, and MotionCompensated FDK (MCFDK). Image quality was evaluated using Contrastto-Noise Ratio (CNR), Tissue Interface Width (TIW), Root-Mean-Square Error (RMSE), and Structural SIMilarity (SSIM). Results: The conventional acquisition 4DFDK reconstructions had median phase averaged CNR, TIW, RMSE, and SSIM of 2.96, 8.02 mm, 83.5, and 0.54, respectively. The rapid acquisition 3DFDK reconstructions had median CNR, TIW, RMSE, and SSIM of 2.99, 13.6 mm, 112, and 0.44 respectively. The rapid acquisition MCFDK reconstructions had median phase averaged CNR, TIW, RMSE, and SSIM of 2.98, 10.2 mm, 103, and 0.46, respectively. Rapid acquisition 4DFDK reconstruction quality was insufficient for any practical use due to sparse angular projection sampling. Conclusions: Results suggest that 4D motion-compensated reconstruction of rapid acquisition thoracic CBCT data are feasible with image quality approaching conventional acquisition CBCT data reconstructed using standard 4DFDK. [ABSTRACT FROM AUTHOR]

• We investigated the impact of organ motion on the effectiveness of hypoxia-guided proton therapy in lung cancer patients. • Large motion amplitude, especially together with increased dose escalation, was associated with a reduction of target coverage and dose homogeneity. • TCP benefits from dose escalation outweigh motion-induced TCP losses. • Large NTCP benefits for lungs, heart and oesophagus were found for escalated proton plans, even compared to photon plans. • Respiratory gating in combination with rescanning is the recommended strategy should motion mitigation be necessary. To investigate the impact of organ motion on hypoxia-guided proton therapy treatments for non-small cell lung cancer (NSCLC) patients. Hypoxia PET and 4D imaging data of six NSCLC patients were used to simulate hypoxia-guided proton therapy with different motion mitigation strategies including rescanning, breath-hold, respiratory gating and tumour tracking. Motion-induced dose degradation was estimated for treatment plans with dose painting of hypoxic tumour sub-volumes at escalated dose levels. Tumour control probability (TCP) and dosimetry indices were assessed to weigh the clinical benefit of dose escalation and motion mitigation. In addition, the difference in normal tissue complication probability (NTCP) between escalated proton and photon VMAT treatments has been assessed. Motion-induced dose degradation was found for target coverage (CTV V 95% up to −4%) and quality of the dose-escalation-by-contour (Q RMS up to 6%) as a function of motion amplitude and amount of dose escalation. The TCP benefit coming from dose escalation (+4–13%) outweighs the motion-induced losses (<2%). Significant average NTCP reductions of dose-escalated proton plans were found for lungs (−14%), oesophagus (−10%) and heart (−16%) compared to conventional VMAT plans. The best plan dosimetry was obtained with breath hold and respiratory gating with rescanning. NSCLC affected by hypoxia appears to be a prime target for proton therapy which, by dose-escalation, allows to mitigate hypoxia-induced radio-resistance despite the sensitivity to organ motion. Furthermore, substantial reduction in normal tissue toxicity can be expected compared to conventional VMAT. Accessibility and standardization of hypoxia imaging and clinical trials are necessary to confirm these findings in a clinical setting. [ABSTRACT FROM AUTHOR]

In this paper, we aim to evaluate the entity of inter-fraction organ motion and deformation in stereotactic body radiotherapy (SBRT) treatments for nodal oligometastatic prostate cancer (PCa). Thirty-three patients with lymph nodes showing oligometastatic PCa treated with SBRT were included. Organs at risk (OARs) were delineated using both simulation computer tomography (s-CT) and daily cone beam CTs (CBCTs) using the Raystation planning system. For each OAR, the union volume (UV) between all the CBCTs and s-CT was computed. An expanded volume (EV) of the s-CT OARs was applied using six different margins (3, 5, 8, 10, 15, and 20 mm). A percentage volume (V%) was computed to assess the intersection between each EV and UV. The OAR deformation and motion were further evaluated using the dice similarity coefficient (DSC) and mean distance to agreement (Mean_DA). The percentage maximum dose variations for all the OARs were estimated. A recalculation with higher dose prescriptions was performed by prescribing 36 Gy/3 fx, as well as 45 Gy/3 fx. The cauda showed the highest matching (DSC = 0.72; Mean_DA = 0.14 cm), and the colon showed the lowest one (DSC = 0.37; Mean_DA = 0.44 cm). The minimum margin, which ensured a V% > 95%, was 3 mm (97.5%) for the cauda and 15 mm (96.6%) for the colon. All the OARs reached the compliance of the constraints in each session. Regarding 36 Gy-plans, the ileum punctual compliance Dmax failed in 58.8% of patients, and it failed in 70.6% of the patients for the ileum, 7.14% for the colon, and 12.5% for the bladder in the case of 45 Gy-plans. This study is an ancillary study of the RADIOSA clinical trial (AIRC IG-22159) and can be used as a benchmark for dose escalation. [ABSTRACT FROM AUTHOR]

We evaluated the impact of respiratory motion on the lung dose during linacbased intensity-modulated total marrow irradiation (IMTMI) using two different approaches: (1) measurement of doses within the lungs of an anthropomorphic phantom using thermoluminescent detectors (TLDs) and (2) treatment delivery measurements using ArcCHECK where gamma passing rates (GPRs) and the mean lung doses were calculated and compared with and without motion. In the first approach, respiratory motions were simulated using a programmable motion platform by using typical published peak-to-peak motion amplitudes of 5, 8, and 12mmin the craniocaudal (CC) direction, denoted here as M1, M2, and M3, respectively, with 2 mm in both anteroposterior (AP) and lateral (LAT) directions. TLDs were placed in five selected locations in the lungs of a RANDO phantom. Average TLD measurements obtained with motion were normalized to those obtained with static phantom delivery. The mean dose ratios were 1.01 (0.98-1.03), 1.04 (1.01-1.09), and 1.08 (1.04-1.12) for respiratory motions M1, M2, and M3, respectively. To determine the impact of directional respiratory motion, we repeated the experiment with 5-, 8-, and 12-mm motion in the CC direction only. The differences in average TLD doses were less than 1% when compared with the M1, M2, and M3 motions indicating a minimal impact from CC motion on lung dose during IMTMI. In the second experimental approach, we evaluated extreme respiratory motion 15 mm excursion in only the CC direction. We placed an ArcCHECK device on a commercial motion platform and delivered the clinical IMTMI plans of five patients. We compared, with and without motion, the dose volume histograms (DVHs) and mean lung dose calculated with the ArcCHECK-3DVH tool as well as GPR with 3%, 5%, and 10% dose agreements and a 3-mm constant distance to agreement (DTA). GPR differed by 11.1 ± 2.1%, 3.8 ± 1.5%, and 0.1 ± 0.2% with dose agreement criteria of 3%, 5%, and 10%, respectively. This indicates that respiratory motion impacts dose distribution in small and isolated parts of the lungs. More importantly, the impact of respiratory motion on the mean lung dose, a critical indicator for toxicity in IMTMI, was not statistically significant (p > 0.05) based on the Student's t-test. We conclude that most patients treated with IMTMI will have negligible dose uncertainty due to respiratory motion. This is particularly reassuring as lung toxicity is the main concern for future IMTMI dose escalation studies. [ABSTRACT FROM AUTHOR]

Purpose: In vivo studies are often required to prove the functionality and safety of medical devices. Clinical trials are costly and complex, adding to ethical scrutiny of animal testing. Anthropomorphic phantoms with versatile functionalities can overcome these issues with regard to medical education or an effective development of assistance systems during image-guided interventions (e.g., robotics, navigation/registration algorithms). In this work, an MRI-compatible and customizable motion phantom is presented to mimic respiratory-triggered organ movement as well as human anatomy., Methods: For this purpose, polyvinyl alcohol cryogel (PVA-C) was the foundation for muscles, liver, kidneys, tumors, and remaining abdominal tissue in different sizes of the abdominal phantom body (APB) with the ability to mimic human tissue in various properties. In addition, a semi-flexible rib cage was 3D-printed. The motion unit (MU) with an electromagnetically shielded stepper motor and mechanical extensions simulated a respiration pattern to move the APB., Results: Each compartment of the APB complied the relaxation times, dielectricity, and elasticity of human tissue. It showed resistance against mold and provided a resealable behavior after needle punctures. During long-term storage, the APB had a weight loss of 2.3%, followed by changes to relaxation times of 9.3% and elasticity up to 79%. The MU was able to physiologically appropriately mimic the organ displacement without reducing the MRI quality., Conclusion: This work presents a novel modularizable and low-cost PVA-C based APB to mimic fundamental organ motion. Beside a further organ motion analysis, an optimization of APB's chemical composition is needed to ensure a realistic motion simulation and reproducible long-term use. This phantom enhances diverse and varied training environments for prospective physicians as well as effective R&D of medical devices with the possibility to reduce in vivo experiments., Competing Interests: Declarations. Conflict of interest: The authors have no relevant financial or non-financial interests to disclose., (© 2024. The Author(s).)

Introduction: The inter-fraction motion of pelvic ± para-aortic (PA) nodal volumes in prostate cancer patients with involved nodes is yet to be quantified and the optimal IGRT strategy for these patients is currently unknown., Methods: A single-centre retrospective evaluation was performed investigating inter-fraction motion in the prostate and involved nodal volumes of patients receiving pelvic ± PA nodal irradiation. Patients were selected for inclusion if they; were undergoing prostate + pelvic node +/- PA node radiation for prostate cancer with involved lymph nodes and had received daily online CBCT scans. The planning CT and subsequent CBCT images from each treatment fraction were selected for analysis., Results: Out of 567 CBCTs, from 20 patients, there were no incidences where independent lymph node displacement was >0.5 cm from planning volumes. Lymph node motion relative to prostate was >0.5 cm on 15 occasions out of 567 scans (2.6%). Where the difference between prostate and lymph nodes was >0.5 cm, this was always a result of the rectum causing variation in the prostate position, not a change in nodal position., Discussion: These results suggests that there is limited independent displacement between the involved pelvic ± PA nodal volumes and bony anatomy. Therefore, bony anatomy could be used as a lymph node match surrogate for prostate patients receiving nodal irradiation for active disease. The results also suggest additional emphasis should be placed on bowel preparation in these patients to reduce the risk of geographical miss., Conclusion: In conclusion, the results of this evaluation suggests that there is limited independent displacement between the involved pelvic ± PA nodal volumes and bony anatomy. This provides evidence to trials investigating the role of pelvic ± PA nodal irradiation to ensure appropriate margins and IGRT strategies are used when investigating this further., (Copyright © 2024. Published by Elsevier Inc.)

Purpose: To assess late gastrointestinal (GI) and genitourinary (GU) side effects in patients with organ-confined unfavorable prostate cancer (PCa) treated with single-dose ablative radiation therapy (SDRT)., Methods and Materials: Thirty patients enrolled in a single-arm prospective trial received 24 Gy SDRT to the whole prostate with urethra-sparing and organ motion control delivered on a Linac platform with a 10 MV flattening filter-free single partial arc. Androgen deprivation therapy was prescribed as per standard of care. Treatment-related acute and late GU and GI toxicities (Common Terminology Criteria for Adverse Events&#95;v5 scale) and quality of life (QoL) outcomes (European Organisation for Research and Treatment of Cancer [EORTC] QLQ-PR25/C30, International Prostate Symptom Score [IPSS]) were assessed at different time points. Minimal important difference (MID) was established as a change of >0.5 pooled standard deviations from baseline. Statistical analysis included analysis of variance and logistic regression., Results: Median follow-up was 18 months (range, 6-31 months), with no ≥G3 late side effects observed. G2 late GI and G2 late GU toxicities occurred in 1 and 2 patients, respectively. GI toxicity of any grade correlated with maximum rectal dose (P = .021). Lower baseline QoL score (P = .025), higher baseline IPSS score (P = .049), acute GU toxicity (P = .029), and acute urinary domain MID (P = .045) predicted GU toxicity of any grade. In multivariate analysis (MVA), only baseline QoL score (odds ratio [OR], 0.95, P = .031) and acute GU toxicity (OR, 8.4, P = .041) remained significant. Significant QoL change was observed only in the urinary domain (P = .005), with a median increase from 8 to 17. Late urinary MID correlated with acute urinary MID (P = .003), acute QoL MID (P = .029), acute GU toxicity (P = .030), and lower baseline urinary score (P = .033). In MVA, only acute urinary MID predicted late urinary MID (OR, 9.7, P = .035)., Conclusions: Our findings provide promising data on the feasibility and safety of 24 Gy whole-gland SDRT with urethra-sparing and organ motion control, in association with androgen deprivation therapy and an adequate prophylactic medication, in organ-confined unfavorable PCa. Long-term follow-up is needed to confirm these results., (Copyright © 2024 Elsevier Inc. All rights reserved.)

We evaluated the impact of respiratory motion on the lung dose during linac-based intensity-modulated total marrow irradiation (IMTMI) using two different approaches: (1) measurement of doses within the lungs of an anthropomorphic phantom using thermoluminescent detectors (TLDs) and (2) treatment delivery measurements using ArcCHECK where gamma passing rates (GPRs) and the mean lung doses were calculated and compared with and without motion. In the first approach, respiratory motions were simulated using a programmable motion platform by using typical published peak-to-peak motion amplitudes of 5, 8, and 12 mm in the craniocaudal (CC) direction, denoted here as M1, M2, and M3, respectively, with 2 mm in both anteroposterior (AP) and lateral (LAT) directions. TLDs were placed in five selected locations in the lungs of a RANDO phantom. Average TLD measurements obtained with motion were normalized to those obtained with static phantom delivery. The mean dose ratios were 1.01 (0.98–1.03), 1.04 (1.01–1.09), and 1.08 (1.04–1.12) for respiratory motions M1, M2, and M3, respectively. To determine the impact of directional respiratory motion, we repeated the experiment with 5-, 8-, and 12-mm motion in the CC direction only. The differences in average TLD doses were less than 1% when compared with the M1, M2, and M3 motions indicating a minimal impact from CC motion on lung dose during IMTMI. In the second experimental approach, we evaluated extreme respiratory motion 15 mm excursion in only the CC direction. We placed an ArcCHECK device on a commercial motion platform and delivered the clinical IMTMI plans of five patients. We compared, with and without motion, the dose volume histograms (DVHs) and mean lung dose calculated with the ArcCHECK-3DVH tool as well as GPR with 3%, 5%, and 10% dose agreements and a 3-mm constant distance to agreement (DTA). GPR differed by 11.1 ± 2.1%, 3.8 ± 1.5%, and 0.1 ± 0.2% with dose agreement criteria of 3%, 5%, and 10%, respectively. This indicates that respiratory motion impacts dose distribution in small and isolated parts of the lungs. More importantly, the impact of respiratory motion on the mean lung dose, a critical indicator for toxicity in IMTMI, was not statistically significant (p > 0.05) based on the Student’s t-test. We conclude that most patients treated with IMTMI will have negligible dose uncertainty due to respiratory motion. This is particularly reassuring as lung toxicity is the main concern for future IMTMI dose escalation studies.

• Thoracic and abdominal organ motion in children varies widely. • Wide variation of margin sizes in thoracic/abdominal area in pediatric patients. • Margin sizes were often not different for (younger) children and adults. • Impact of delineation variability to geometrical errors remains uncertain in children. For radiotherapy of thoracic and abdominal tumors safety margins are applied to address geometrical uncertainties caused by e.g. set-up errors, organ motion and delineation variability. For pediatric patients no standardized margins are defined. Moreover, studies on these geometrical uncertainties are relatively scarce. Therefore, this systematic review presents an overview of organ motion, applied margin sizes and delineation variability in patients <18 years. A search from January 2000 to March 2021 in Medline, Embase, Web of Science, ClinicalTrials.gov and the International Trials Registry Platform resulted in the inclusion of 117 studies reporting on organ motion, margin sizes and/or delineation variability. Studies were heterogeneous concerning age, tumor types, the use of general anesthesia, imaging modalities; image guidance techniques were reported in 39% of the studies. Inter- and intrafractional motion as reported for different organs was largest in cranio-caudal direction and ranged from −9.1 to 10.0 mm and −4.4 to 19.5 mm, respectively. Motion quantification methodologies differed between studies regarding measures of displacement and definitions of motion direction. Reported CTV–PTV margins varied from 3 to 20 mm for both thoracic and abdominal targets, and for spinal and pelvic from 3to 15 mm and 3 to 10 mm, respectively. Studies reported wide variation in interobserver variability of target volume delineation, which may affect dose distributions to both target volumes and organs at risk. Results of this review indicate possible reduction of margin sizes for children, however, wide variation in organ motion and delineation variability caused by differences in methodologies and outcomes hamper the use of standardized margins. [ABSTRACT FROM AUTHOR]

Inter-fraction organ variations cause deviations between planned and delivered doses in patients receiving radiotherapy for prostate cancer. This study compared planned (D P) vs accumulated doses (D A) obtained from daily cone-beam computed tomography (CBCT) scans in high-risk- prostate cancer with pelvic lymph nodes irradiation. An intensity-based deformable image registration algorithm used to estimate contours for D A was validated using geometrical agreement between radiation oncologist's and deformable image registration algorithm propagated contours. Spearman rank correlations (r s) between geometric measures and changes in organ volumes were evaluated for 20 cases. Dose-volume (DV) differences between D A and D P were compared (Wilcoxon rank test, p < 0.05). A novel region-of-interest (ROI) method was developed and mean doses were analyzed. Geometrical measures for the prostate and organ-at-risk contours were within clinically acceptable criteria. Inter-group mean (± SD) CBCT volumes for the rectum were larger compared to planning CT (pCT) (51.1 ± 11.3 cm3 vs 46.6 ± 16.1 cm3), and were moderately correlated with variations in pCT volumes, rs = 0.663, p < 0.01. Mean rectum DV for D A was higher at V30-40 Gy and lower at V70-75 Gy, p < 0.05. Mean bladder CBCT volumes were smaller compared to pCT (198.8 ± 55 cm3 vs 211.5 ± 89.1 cm3), and was moderately correlated with pCT volumes, rs = 0.789, p < 0.01. Bladder D A was higher at V30-65 Gy and lower at V70-75 Gy (p < 0.05). For the ROI method, rectum and bladder D A were lower at 5 to 10 mm (p < 0.01) as compared to D P , whilst bladder D A was higher than D P at 20 to 50 mm (p < 0.01). Generated D A demonstrated significant differences in organ-at-risk doses as compared to D P. A well-constructed workflow incorporating a ROI DV-extraction method has been validated in terms of efficiency and accuracy designed for seamless integration in the clinic to guide future plan adaptation. [ABSTRACT FROM AUTHOR]

Aim: Radiation therapy has historically used margins for target volume to ensure dosimetric planning criteria. The size of margin for a given treatment site is still uncertain particularly for moving targets along with set-up variations leading to a fuzziness of target volume. In this study, we have estimated the dosimetric benefit of normal structures using biological-based optimal margins. The treatment margins are derived by knowledge-based fuzzy logic technique which is considering the radiotherapy uncertainties in treatment planning. Materials and methods: All treatment plans were performed using stepped increments of asymmetric margins to estimate prostate radiobiological indices such as tumour control probability (TCP) and normal tissue complication probability (NTCP). An absolute NTCP of 5% was considered to be the maximum acceptable value while TCP of 85% was considered to be the minimal acceptable limit for each volumetric modulated arc therapy (VMAT) plan of localised prostate cancer radiotherapy. Results were used to formulate rules and membership functions for Mamdani-type fuzzy inference system (FIS). In implementing the rules for the fuzzy system for ΔNTCP values above 10%, the PTV margin was not permitted to exceed 5 mm to avoid rectal complications due to margin selection. The new margins were applied in VMAT planning of prostate cancer for standard displacement errors. The dosimetric results of normal tissue predictors were estimated such as organ mean doses, rectum V60 (volume receiving 60 Gy), bladder V65 (volume receiving 65 Gy) and other clinically significant dose–volume indicators and compared with VMAT plans using current margin formulations. Results: Dosimetric results compared well to the results obtained by current techniques. Good agreement was obtained between proposed fuzzy model margins and currently used margins in lower error magnitude, but significant results were observed at higher error magnitude when organ toxicity concerned without compromising the target volumes. Findings: The new margins may be helpful to estimate possible outcomes of normal tissue complications and thus may improve complication free survival particularly when organ motion errors are inevitable, case by case. [ABSTRACT FROM AUTHOR]

Background: Radiotherapy plays an important role in cancer treatment today. Successful radiotherapy includes precise positioning and accurate dosimetry.Objective: To use NIPAM gel dosimeter and concentric swing machine to simulate and evaluate the feasibility of lung or upper abdominal tumor dose distribution during breathing.Methods: We used a concentric swing machine to simulate actual radiotherapy for lung or upper abdomen tumors. A 4 × 4 cm2 irradiation field area was set and MRI was performed. Next, readout analysis was performed using MATLAB and the 3 mm, 3% gamma passing rate > 95% was used as a basis for evaluation.Results: The concentric dynamic dose curve for a simulated respiratory rate of 3 seconds/breath and 4 × 4 cm2 field was compared with 4 × 4, 3 × 3, and 2 × 2 cm2 treatment planning systems (TPS), and the 3 mm, 3% gamma passing rate was 42.87%, 54.96%, and 49.92%, respectively. Pre-simulation showed that the high-dose region dose curve was similar to the 2 × 2 cm2 TPS result. After appropriate selection and comparison, we found that the 3 mm, 3% gamma passing rate was 97.92% on comparing the > 60% dose curve with the 2 × 2 cm2 TPS.Conclusions: NIPAM gel dosimeter and concentric swing machine use is feasible to simulate dose distribution during breathing and results conforming to clinical evaluation standards. [ABSTRACT FROM AUTHOR]

Approximately 50% of melanomas, 30-40% of lung and breast cancers and 10-20% of renal and gastrointestinal tumors metastasize to the adrenal gland. Metastatic adrenal involvement is diagnosed by computed tomography (CT) with contrast medium, ultrasound (which does not explore the left adrenal gland well), magnetic resonance imaging (MRI) with contrast medium and 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18FDGPET -CT) which also evaluates lesion uptake. The simulation CT should be performed with contrast medium; an oral bolus of contrast medium is useful, given adrenal gland proximity to the duodenum. The simulation CT may be merged with PET -CT images with 18FDG in order to evaluate uptaking areas. In contouring, the radiologically visible and/or uptaking lesion provides the gross tumor volume (GTV). Appropriate techniques are needed to overcome target motion. Single fraction stereotactic radiotherapy (SRT) with median doses of 16-23 Gy is rarely used. More common are doses of 25-48 Gy in 3-10 fractions although 3 or 5 fractions are preferred. Local control at 1 and 2 years ranges from 44 to 100% and from 27 to 100%, respectively. The local control rate is as high as 90%, remaining stable during follow-up when BED10Gy is equal to or greater than 100 Gy. SRT -related toxicity is mild, consisting mainly of gastrointestinal disorders, local pain and fatigue. Adrenal insufficiency is rare. [ABSTRACT FROM AUTHOR]

Even though systemic therapy is standard treatment for lymph node metastases, metastasis-directed stereotactic radiotherapy (SRT) seems to be a valid option in oligometastatic patients with a low disease burden. Positron emission tomography-computed tomography (PET -CT) is the gold standard for assessing metastases to the lymph nodes; co-registration of PET -CT images and planning CT images are the basis for gross tumor volume (GTV) delineation. Appropriate techniques are needed to overcome target motion. SRT schedules depend on the irradiation site, target volume and dose constraints to the organs at risk (OARs) of toxicity. Although several fractionation schemes were reported, total doses of 48-60 Gy in 4-8 fractions were proposed for mediastinal lymph node SRT, with the spinal cord, esophagus, heart and proximal bronchial tree being the dose limiting OAR s. Total doses ranged from 30 to 45 Gy, with daily fractions of 7-12 Gy for abdominal lymph nodes, with dose limiting OARs being the liver, kidneys, bowel and bladder. SRT on lymph node metastases is safe; late side effects, particularly severe, are rare. [ABSTRACT FROM AUTHOR]

The liver is the first metastatic site in 15-25% of colorectal cancer patients and one of the first metastatic sites for lung and breast cancer patients. A computed tomography (CT) scan with contrast medium is a standard procedure for assessing liver lesions but magnetic resonance imaging (MRI) characterizes small lesions better thanks to its high soft-tissue contrast. Positron emission tomography with computed tomography (PET -CT) plays a complementary role in the diagnosis of liver metastases. Triphasic (arterial, venous and time-delayed) acquisition of contrast-medium CT images is the first step in treatment planning. Since the liver exhibits a relatively wide mobility due to respiratory movements and bowel filling, appropriate techniques are needed for target identification and motion management. Contouring requires precise recognition of target lesion edges. Information from contrast MRI and/or PET -CT is crucial as they best visualize metastatic disease in the parenchyma. Even though different fractionation schedules were reported, doses and fractionation schedules for liver stereotactic radiotherapy (SRT) have not yet been established. The best local control rates were obtained with BED10 values over 100 Gy. Local control rates from most retrospective studies, which were limited by short follow-ups and included different primary tumors with intrinsic heterogeneity, ranged from 60% to 90% at 1 and 2 years. The most common SRT -related toxicities are increases in liver enzymes, hyperbilirubinemia and hypoalbuminemia. Overall, late toxicity is mild even in long-term follow-ups. [ABSTRACT FROM AUTHOR]

30-60% of cancer patients develop lung metastases, mostly from primary tumors in the colon-rectum, lung, head and neck area, breast and kidney. Nowadays, stereotactic radiotherapy (SRT) is considered the ideal modality for treating pulmonary metastases. When lung metastases are suspected, complete disease staging includes a total body computed tomography (CT) and/or positron emission tomography-computed tomography (PET -CT) scan. PET -CT has higher specificity and sensitivity than a CT scan when investigating mediastinal lymph nodes, diagnosing a solitary lung lesion and detecting distant metastases. For treatment planning, a multi-detector planning CT scan of the entire chest is usually performed, with or without intravenous contrast media or esophageal lumen opacification, especially when central lesions have to be irradiated. Respiratory management is recommended in lung SRT, taking the breath cycle into account in planning and delivery. For contouring, co-registration and/or matching planning CT and diagnostic images (as provided by contrast enhanced CT or PET -CT) are useful, particularly for central tumors. Doses and fractionation schedules are heterogeneous, ranging from 33 to 60 Gy in 3-6 fractions. Independently of fractionation schedule, a BED10 > 100 Gy is recommended for high local control rates. Single fraction SRT (ranges 15-30 Gy) is occasionally administered, particularly for small lesions. SRT provides tumor control rates of up to 91% at 3 years, with limited toxicities. The present overview focuses on technical and clinical aspects related to treatment planning, dose constraints, outcome and toxicity of SRT for lung metastases. [ABSTRACT FROM AUTHOR]

Stereotactic radiotherapy (SRT) is a multi-step procedure with each step requiring extreme accuracy. Physician-dependent accuracy includes appropriate disease staging, multi-disciplinary discussion with shared decision-making, choice of morphological and functional imaging methods to identify and delineate the tumor target and organs at risk, an image-guided patient set-up, active or passive management of intra-fraction movement, clinical and instrumental follow-up. Medical physicist-dependent accuracy includes use of advanced software for treatment planning and more advanced Quality Assurance procedures than required for conventional radiotherapy. Consequently, all the professionals require appropriate training in skills for high-quality SRT. Thanks to the technological advances, SRT has moved from a "frame-based" technique, i.e. the use of stereotactic coordinates which are identified by means of rigid localization frames, to the modern "frame-less" SRT which localizes the target volume directly, or by means of anatomical surrogates or fiducial markers that have previously been placed within or near the target. This review describes all the SRT steps in depth, from target simulation and delineation procedures to treatment delivery and image-guided radiation therapy. Target movement assessment and management are also described. [ABSTRACT FROM AUTHOR]

Purpose: This work presents the implementation of an RGB-D camera as a surrogate signal for liver respiratory-induced motion estimation. This study aims to validate the feasibility of RGB-D cameras as a surrogate in a human subject experiment and to compare the performance of different correspondence models., Methods: The proposed approach uses an RGB-D camera to compute an abdominal surface reconstruction and estimate the liver respiratory-induced motion. Two sets of validation experiments were conducted, first, using a robotic liver phantom and, secondly, performing a clinical study with human subjects. In the clinical study, three correspondence models were created changing the conditions of the learning-based model., Results: The motion model for the robotic liver phantom displayed an error below 3 mm with a coefficient of determination above 90% for the different directions of motion. The clinical study presented errors of 4.5, 2.5, and 2.9 mm for the three different motion models with a coefficient of determination above 80% for all three cases., Conclusion: RGB-D cameras are a promising method to accurately estimate the liver respiratory-induced motion. The internal motion can be estimated in a non-contact, noninvasive and flexible approach. Additionally, three training conditions for the correspondence model are studied to potentially mitigate intra- and inter-fraction motion., (© 2024. The Author(s).)

Aims: Delineation variations and organ motion produce difficult-to-quantify uncertainties in planned radiation doses to targets and organs at risk. Similar to manual contouring, most automatic segmentation tools generate single delineations per structure; however, this does not indicate the range of clinically acceptable delineations. This study develops a method to generate a range of automatic cardiac structure segmentations, incorporating motion and delineation uncertainty, and evaluates the dosimetric impact in lung cancer., Materials and Methods: Eighteen cardiac structures were delineated using a locally developed auto-segmentation tool. It was applied to lung cancer planning CTs for 27 curative (planned dose ≥50 Gy) cases, and delineation variations were estimated by using ten mapping-atlases to provide separate substructure segmentations. Motion-related cardiac segmentation variations were estimated by auto-contouring structures on ten respiratory phases for 9/27 cases that had 4D-planning CTs. Dose volume histograms (DVHs) incorporating these variations were generated for comparison., Results: Variations in mean doses (Dmean), defined as the range in values across ten feasible auto-segmentations, were calculated for each cardiac substructure. Over the study cohort the median variations for delineation uncertainty and motion were 2.20-11.09 Gy and 0.72-4.06 Gy, respectively. As relative values, variations in Dmean were between 18.7%-65.3% and 7.8%-32.5% for delineation uncertainty and motion, respectively. Doses vary depending on the individual planned dose distribution, not simply on segmentation differences, with larger dose variations to cardiac structures lying within areas of steep dose gradient., Conclusion: Radiotherapy dose uncertainties from delineation variations and respiratory-related heart motion were quantified using a cardiac substructure automatic segmentation tool. This predicts the 'dose range' where doses to structures are most likely to fall, rather than single DVH curves. This enables consideration of these uncertainties in cardiotoxicity research and for future plan optimisation. The tool was designed for cardiac structures, but similar methods are potentially applicable to other OARs., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

In this paper, we aim to evaluate the entity of inter-fraction organ motion and deformation in stereotactic body radiotherapy (SBRT) treatments for nodal oligometastatic prostate cancer (PCa). Thirty-three patients with lymph nodes showing oligometastatic PCa treated with SBRT were included. Organs at risk (OARs) were delineated using both simulation computer tomography (s-CT) and daily cone beam CTs (CBCTs) using the Raystation planning system. For each OAR, the union volume (UV) between all the CBCTs and s-CT was computed. An expanded volume (EV) of the s-CT OARs was applied using six different margins (3, 5, 8, 10, 15, and 20 mm). A percentage volume (V%) was computed to assess the intersection between each EV and UV. The OAR deformation and motion were further evaluated using the dice similarity coefficient (DSC) and mean distance to agreement (Mean_DA). The percentage maximum dose variations for all the OARs were estimated. A recalculation with higher dose prescriptions was performed by prescribing 36 Gy/3 fx, as well as 45 Gy/3 fx. The cauda showed the highest matching (DSC = 0.72; Mean_DA = 0.14 cm), and the colon showed the lowest one (DSC = 0.37; Mean_DA = 0.44 cm). The minimum margin, which ensured a V% > 95%, was 3 mm (97.5%) for the cauda and 15 mm (96.6%) for the colon. All the OARs reached the compliance of the constraints in each session. Regarding 36 Gy-plans, the ileum punctual compliance Dmax failed in 58.8% of patients, and it failed in 70.6% of the patients for the ileum, 7.14% for the colon, and 12.5% for the bladder in the case of 45 Gy-plans. This study is an ancillary study of the RADIOSA clinical trial (AIRC IG-22159) and can be used as a benchmark for dose escalation.

Introduction: Organ motion (OM) and volumetric changes pose challenges in radiotherapy (RT) for locally advanced cervical cancer (LACC). Magnetic Resonance-guided Radiotherapy (MRgRT) combines improved MRI contrast with adaptive RT plans for daily anatomical changes. Our goal was to analyze cervico-uterine structure (CUS) changes during RT to develop strategies for managing OM., Materials and Methods: LACC patients received chemoradiation by MRIdian system with a simultaneous integrated boost (SIB) protocol. Prescription doses of 55-50.6 Gy at PTV1 and 45-39.6 Gy at PTV2 were given in 22 and 25 fractions. Daily MRI scans were co-registered with planning scans and CUS changes were assessed.Six PTVs were created by adding 0.5, 0.7, 1, 1.3, 1.5, and 2 cm margins to the CUS, based on the simulation MRI. Adequate margins were determined to include 95 % of the CUSs throughout the entire treatment in 95 % of patients., Results: Analysis of 15 LACC patients and 372 MR scans showed a 31 % median CUS volume decrease. Asymmetric margins of 2 cm cranially, 0.5 cm caudally, 1.5 cm posteriorly, 2 cm anteriorly, and 1.5 cm on both sides were optimal for PTV, adapting to CUS variations. Post-14th fraction, smaller margins of 0.7 cm cranially, 0.5 cm caudally, 1.3 cm posteriorly, 1.3 cm anteriorly, and 1.3 cm on both sides sufficed., Conclusion: CUS mobility varies during RT, suggesting reduced PTV margins after the third week. MRgRT with adaptive strategies optimizes dose delivery, emphasizing the importance of streamlined IGRT with reduced PTV margins using a tailored MRgRT workflow with hybrid MRI-guided systems., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier B.V. on behalf of European Society for Radiotherapy and Oncology.)

Purpose&#xD;4D computed tomography (4DCT) is the clinical standard to image organ motion in radiotherapy, although it is limited in imaging breathing variability. We propose a method to transfer breathing motion across longitudinal imaging datasets to include intra-patient variability and verify its performance in lung cancer patients. &#xD;Methods &#xD;Five repeated control 4DCTs for 6 non-small cell lung cancer patients were combined into multi-breath datasets (m4DCT) by merging stages of deformable image registration to isolate respiratory motion. The displacement of the centre of mass of the primary tumour and its volume changes were evaluated to quantify intra-patient differences. Internal target volumes defined on the m4DCT were compared with those conventionally drawn on the 4DCT.&#xD;Results &#xD;Motion analysis suggests no discontinuity at the junction between successive breaths, confirming the method's ability to merge repeated imaging into a continuum. Motion (variability) is primarily in superior-inferior direction and goes from 14.4 mm (8.7 mm) down to 0.1 mm (0.6 mm), respectively for tumours located in the lower lobes or most apical ones. On average, up to 65% and 74% of the tumour volume was subject to expansion or contraction in the inhalation and exhalation phases. These variations lead to an enlargement of the ITV up to 8% of its volume in our dataset.&#xD;Conclusion &#xD;4DCT can be extended to model variable breathing motion by adding synthetic phases from multiple time-resolved images. The inclusion of this improved knowledge of patients' breathing allows better definition of treatment volumes and their margins for radiation therapy.&#xD., (Creative Commons Attribution license.)

Purpose: This study aimed to assess the margin for the planning target volume (PTV) using the Van Herk formula. We then validated the proposed margin by real-time magnetic resonance imaging (MRI)., Methods: An analysis of cone-beam computed tomography (CBCT) data from early glottic cancer patients was performed to evaluate organ motion. Deformed clinical target volumes (CTV) after rigid registration were acquired using the Velocity program (Varian Medical Systems, Palo Alto, CA, USA). Systematic (Σ) and random errors (σ) were evaluated. The margin for the PTV was defined as 2.5 Σ + 0.7 σ according to the Van Herk formula. To validate this margin, we accrued healthy volunteers. Sagittal real-time cine MRI was conducted using the ViewRay system (ViewRay Inc., Oakwood Village, OH, USA). Within the obtained sagittal images, the vocal cord was delineated. The movement of the vocal cord was summed up and considered as the internal target volume (ITV). We then assessed the degree of overlap between the ITV and the PTV (vocal cord plus margins) by calculating the volume overlap ratio, represented as (ITV∩PTV)/ITV., Results: CBCTs of 17 early glottic patients were analyzed. Σ and σ were 0.55 and 0.57 for left-right (LR), 0.70 and 0.60 for anterior-posterior (AP), and 1.84 and 1.04 for superior-inferior (SI), respectively. The calculated margin was 1.8 mm (LR), 2.2 mm (AP), and 5.3 mm (SI). Four healthy volunteers participated for validation. A margin of 3 mm (AP) and 5 mm (SI) was applied to the vocal cord as the PTV. The average volume overlap ratio between ITV and PTV was 0.92 (range 0.85-0.99) without swallowing and 0.77 (range 0.70-0.88) with swallowing., Conclusion: By evaluating organ motion by using CBCT, the margin was 1.8 (LR), 2.2 (AP), and 5.3 mm (SI). The margin acquired using CBCT fitted well in real-time cine MRI. Given that swallowing during radiotherapy can result in a substantial displacement, it is crucial to consider strategies aimed at minimizing swallowing and related motion., (© 2024. The Author(s).)

Purpose: Left ventricle (LV) regional myocardial displacement due to cardiac motion was assessed using cardiovascular magnetic resonance (CMR) cine images to establish region-specific margins for cardiac radioablation treatments., Methods: CMR breath-hold cine images and LV myocardial tissue contour points were analyzed for 200 subjects, including controls (n = 50) and heart failure (HF) patients with preserved ejection fraction (HFpEF, n = 50), mid-range ejection fraction (HFmrEF, n = 50), and reduced ejection fraction (HFrEF, n = 50). Contour points were divided into segments according to the 17-segment model. For each patient, contour point displacements were determined for the long-axis (all 17 segments) and short-axis (segments 1-12) directions. Mean overall, tangential (longitudinal or circumferential), and normal (radial) displacements were calculated for the 17 segments and for each segment level., Results: The greatest overall motion was observed in the control group-long axis: 4.5 ± 1.2 mm (segment 13 [apical anterior] epicardium) to 13.8 ± 3.0 mm (segment 6 [basal anterolateral] endocardium), short axis: 4.3 ± 0.8 mm (segment 9 [mid inferoseptal] epicardium) to 11.5 ± 2.3 mm (segment 1 [basal anterior] endocardium). HF patients exhibited lesser motion, with the smallest overall displacements observed in the HFrEF group-long axis: 4.3 ± 1.7 mm (segment 13 [apical anterior] epicardium) to 10.6 ± 3.4 mm (segment 6 [basal anterolateral] endocardium), short axis: 3.9 ± 1.3 mm (segment 8 [mid anteroseptal] epicardium) to 7.4 ± 2.8 mm (segment 1 [basal anterior] endocardium)., Conclusions: This analysis provides an estimate of epicardial and endocardial displacement for the 17 segments of the LV for patients with normal and impaired LV function. This reference data can be used to establish treatment planning margin guidelines for cardiac radioablation. Smaller margins may be used for patients with higher degree of impaired heart function, depending on the LV segment., (© 2024 The Authors. Journal of Applied Clinical Medical Physics is published by Wiley Periodicals, Inc. on behalf of The American Association of Physicists in Medicine.)

Background: Image-guidance promises to make complex situations in liver interventions safer. Clinical success is limited by intraoperative organ motion due to ventilation and surgical manipulation. The aim was to assess influence of different ventilatory and operative states on liver motion in an experimental model., Methods: Liver motion due to ventilation (expiration, middle, and full inspiration) and operative state (native, laparotomy, and pneumoperitoneum) was assessed in a live porcine model (n = 10). Computed tomography (CT)-scans were taken for each pig for each possible combination of factors. Liver motion was measured by the vectors between predefined landmarks along the hepatic vein tree between CT scans after image segmentation., Results: Liver position changed significantly with ventilation. Peripheral regions of the liver showed significantly higher motion (maximal Euclidean motion 17.9 ± 2.7 mm) than central regions (maximal Euclidean motion 12.6 ± 2.1 mm, p < 0.001) across all operative states. The total average motion measured 11.6 ± 0.7 mm (p < 0.001). Between the operative states, the position of the liver changed the most from native state to pneumoperitoneum (14.6 ± 0.9 mm, p < 0.001). From native state to laparotomy comparatively, the displacement averaged 9.8 ± 1.2 mm (p < 0.001). With pneumoperitoneum, the breath-dependent liver motion was significantly reduced when compared to other modalities. Liver motion due to ventilation was 7.7 ± 0.6 mm during pneumoperitoneum, 13.9 ± 1.1 mm with laparotomy, and 13.5 ± 1.4 mm in the native state (p < 0.001 in all cases)., Conclusions: Ventilation and application of pneumoperitoneum caused significant changes in liver position. Liver motion was reduced but clearly measurable during pneumoperitoneum. Intraoperative guidance/navigation systems should therefore account for ventilation and intraoperative changes of liver position and peripheral deformation., (© 2023. The Author(s).)

Purpose: Accuracy of image-guided liver surgery is challenged by deformation of the liver during the procedure. This study aims at improving navigation accuracy by using intraoperative deep learning segmentation and nonrigid registration of hepatic vasculature from ultrasound (US) images to compensate for changes in liver position and deformation., Methods: This was a single-center prospective study of patients with liver metastases from any origin. Electromagnetic tracking was used to follow US and liver movement. A preoperative 3D model of the liver, including liver lesions, and hepatic and portal vasculature, was registered with the intraoperative organ position. Hepatic vasculature was segmented using a reduced 3D U-Net and registered to preoperative imaging after initial alignment followed by nonrigid registration. Accuracy was assessed as Euclidean distance between the tumor center imaged in the intraoperative US and the registered preoperative image., Results: Median target registration error (TRE) after initial alignment was 11.6 mm in 25 procedures and improved to 6.9 mm after nonrigid registration (p = 0.0076). The number of TREs above 10 mm halved from 16 to 8 after nonrigid registration. In 9 cases, registration was performed twice after failure of the first attempt. The first registration cycle was completed in median 11 min (8:00-18:45 min) and a second in 5 min (2:30-10:20 min)., Conclusion: This novel registration workflow using automatic vascular detection and nonrigid registration allows to accurately localize liver lesions. Further automation in the workflow is required in initial alignment and classification accuracy., (© 2023. CARS.)

Background and Purpose: Imaging of respiration-induced anatomical changes is essential to ensure high accuracy in radiotherapy of lung cancer. We expanded here on methods for retrospective reconstruction of time-resolved volumetric magnetic resonance (4DMR) of the thoracic region and benchmarked the results against 4D computed tomography (4DCT)., Materials and Method: MR data of six lung cancer patients were collected by interleaving cine-navigator images with 2D data frame images, acquired across the thorax. The data frame images have been stacked in volumes based on a similarity metric that considers the anatomical deformation of lungs, while addressing ambiguities in respiratory phase detection and interpolation of missing data. The resulting images were validated against cine-navigator images and compared to paired 4DCTs in terms of amplitude and period of motion, assessing differences in internal target volume (ITV) margin definition., Results: 4DMR-based motion amplitude was on average within 1.8 mm of that measured in the corresponding 2D cine-navigator images. In our dataset, the 4DCT motion and the 4DMR median amplitude were always within 3.8 mm. The median period was generally close to CT references, although deviations up to 24 % have been observed. These changes were reflected in the ITV, which was generally larger for MRI than for 4DCT (up to 39.7 %)., Conclusions: The proposed algorithm for retrospective reconstruction of time-resolved volumetric MR provided quality anatomical images with high temporal resolution for motion modelling and treatment planning. The potential for imaging organ motion variability makes 4DMR a valuable complement to standard 4DCT imaging., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)

Objective . Carbon ion radiotherapy is a promising radiation technique for malignancies like pancreatic cancer. However, organs' motion imposes challenges for achieving homogeneous dose delivery. In this study, an anthropomorphic P ancreas P hantom for I on-b e am T herapy (PPIeT) was developed to simulate breathing and gastrointestinal motion during radiotherapy. Approach . The developed phantom contains a pancreas, two kidneys, a duodenum, a spine and a spinal cord. The shell of the organs was 3D printed and filled with agarose-based mixtures. Hounsfield Units (HU) of PPIeTs' organs were measured by CT. The pancreas motion amplitude in cranial-caudal (CC) direction was evaluated from patients' 4D CT data. Motions within the obtained range were simulated and analyzed in PPIeT using MRI. Additionally, GI motion was mimicked by changing the volume of the duodenum and quantified by MRI. A patient-like treatment plan was calculated for carbon ions, and the phantom was irradiated in a static and moving condition. Dose measurements in the organs were performed using an ionization chamber and dosimetric films. Main results . PPIeT presented tissue equivalent HU and reproducible breathing-induced CC displacements of the pancreas between (3.98 ± 0.36) mm and a maximum of (18.19 ± 0.44) mm. The observed maximum change in distance of (14.28 ± 0.12) mm between pancreas and duodenum was consistent with findings in patients. Carbon ion irradiation revealed homogenous coverage of the virtual tumor at the pancreas in static condition with a 1% deviation from the treatment plan. Instead, the dose delivery during motion with the maximum amplitude yielded an underdosage of 21% at the target and an increased uncertainty by two orders of magnitude. Significance . A dedicated phantom was designed and developed for breathing motion assessment of dose deposition during carbon ion radiotherapy. PPIeT is a unique tool for dose verification in the pancreas and its organs at risk during end-to-end tests., (Creative Commons Attribution license.)