Respiratory Motion Management Research Articles

Impact of abdominal compression on heart and stomach motion for stereotactic arrhythmia radioablation.

To evaluate the effectiveness of abdominal compression (AC) as a respiratory motion management method for the heart and stomach during stereotactic arrhythmia radioablation (STAR). 4D computed tomography (4DCT) scans of patients imaged with AC or without AC (free-breathing: FB) were obtained from ventricular-tachycardia (VT) (n=3), lung cancer (n=18), and liver cancer (n=18) patients. Patients treated for VT were imaged both FB and with AC. Lung and liver patients were imaged once with FB or with AC, respectively. The heart, left ventricle (LV), LV components (LVCs), and stomach were contoured on each phase of the 4DCTs. Centre of mass (COM) translations in the left/right (LR), ant/post (AP), and sup/inf (SI) directions were measured for each structure. Minimum distances between LVCs and the stomach over the respiratory cycle were also measured on each 4DCT phase. Mann-Whitney U-tests were performed between AC and FB datasets with a significance of α=0.05. No statistical difference (all p values were>0.05) was found in COM translations between FB and AC patient datasets for all contoured cardiac structures. A reduction in COM translation with AC relative to FB was patient, direction, and structure specific for the three VT patients. A significant decrease in the AP range of motion of the stomach was observed under AC compared to FB. No statistical difference was found between minimum distances to the stomach and LVCs between FB and AC. AC was not a consistent motion management method for STAR, nor does not uniformly affect the separation distance between LVCs and the stomach. If AC is employed in future STAR protocols, the motion of the target volume and its relative distance to the stomach should be compared on two 4DCTs: one while the patient is FB and one under AC.

Survey on fan-beam computed tomography for radiotherapy: Current implementation and future perspectives of motion management and surface guidance devices

Background and purposeThis work reports on the results of a survey performed on the use of computed tomography (CT) imaging for motion management, surface guidance devices, and their quality assurance (QA). Additionally, it details the collected user insights regarding professional needs in CT for radiotherapy. The purpose of the survey is to understand current practice, professional needs and future directions in the field of fan-beam CT in radiation therapy (RT). Materials and methodsAn online institutional survey was conducted between 1-Sep-2022 and 10-Oct-2022 among medical physics experts at Belgian and Dutch radiotherapy institutions, to assess the current status, challenges, and future directions of motion management and surface image-guided radiotherapy. The survey consisted of a maximum of 143 questions, with the exact number depending on participants’ responses. ResultsThe response rate was 66 % (31/47). Respiratory management was reported as standard practice in all but one institution; surface imaging during CT-simulation was reported in ten institutions. QA procedures are applied with varying frequencies and methodologies, primarily with commercial anatomy-like phantoms. Surface guidance users report employing commercial static and dynamic phantoms. Four main subjects are considered clinically important by the respondents: surface guidance, CT protocol optimisation, implementing gated imaging (4DCT, breath-hold), and a tattoo-less workflow. ConclusionsThe survey highlights the scattered pattern of QA procedures for respiratory motion management, indicating the need for well-defined, unambiguous, and practicable guidelines. Surface guidance is considered one of the most important techniques that should be implemented in the clinical radiotherapy simulation workflow.

Dosimetric rationale and preliminary experience in proton plus carbon-ion radiotherapy for esophageal carcinoma: a retrospective analysis

BackgroundConcurrent chemoradiotherapy has been standard of care for unresectable esophageal carcinoma. There were no reports on proton radiotherapy (PRT) plus carbon-ion radiotherapy (CIRT) with pencil beam scanning (PBS) for esophageal carcinoma. This study evaluated the tolerability and efficiency of proton and sequential carbon-ion boost radiotherapy for esophageal carcinoma.MethodsFrom April 2017 to July 2020, 20 patients with primary esophageal carcinoma at stages II–IV were treated with PRT plus sequential CIRT with PBS. A median relative biological effectiveness-weighted PRT dose of 50 Gy in 25 fractions, and a sequential CIRT dose of 21 Gy in 7 fractions were delivered. Respiratory motion management was used if the tumor moved > 5 mm during the breathing cycle. A dosimetric comparison of photon intensity-modulated radiotherapy (IMRT), PRT, and CIRT was performed. The median times and rates of survivals were estimated using the Kaplan–Meier method. Comparison of the dose-volume parameters of the organs at risk employed the Wilcoxon matched-pairs test.ResultsTwenty patients (15 men and 5 women, median age 70 years) were included in the analysis. With a median follow-up period of 25.0 months, the 2-year overall survival and progression-free survival rates were 69.2% and 57.4%, respectively. The patients tolerated radiotherapy and chemotherapy well. Grades 1, 2, 3, and 4 acute hematological toxicities were detected in 25%, 30%, 10%, and 30% of patients, respectively. Grades 3–5 acute non-hematological toxicities were not observed. Late toxicity events included grades 1, 2, and 3 in 50%, 20%, and 10% (pulmonary and esophageal toxicity in each) of patients. Grades 4–5 late toxicities were not noted. PRT or CIRT produced lower doses to organs at risk than did photon IMRT, especially the maximum dose delivered to the spinal cord and the mean doses delivered to the lungs and heart.ConclusionsPRT plus CIRT with PBS appears to be a safe and effective treatment for esophageal carcinoma. PRT and CIRT delivered lower doses to organs at risk than did photon IMRT. Further investigation is warranted.

Abdominal compression as motion management for stereotactic radiotherapy of ventricular tachycardia

Background and purposeStereotactic body radiotherapy (SBRT) has emerged as a promising treatment for patients with ventricular tachycardia (VT) who do not respond to standard treatments. However, the management of respiratory motion during treatment remains a challenge. This study aimed to investigate the effect of abdominal compression (AC) on respiratory induced motion in the heart. Materials and methodsA patient cohort of 18 lung cancer patients was utilized, where two four-dimensional computed tomography (4DCT) scans were performed for each patient, one with and one without AC. The patient setup consisted of an AC plate together with a stereotactic body frame. The left coronary artery, the left anterior descending artery, the lateral wall of the left ventricle, the heart apex, the carina, and the right and left diaphragm were delineated in max expiration and max inspiration phases in both 4DCT scans. The center of mass shift from expiration to inspiration phase was determined to assess the AC’s impact on respiratory motion. ResultsA significant reduction in motion in the superior-inferior direction was found for all heart structures when AC was used. The median respiratory motion of the heart structures decreased by approximately 1–3 mm with AC in the superior-inferior direction, and approximately 60% of the patients had a motion reduction ≥3 mm in the left ventricle wall. ConclusionThese findings suggest that AC has the potential to improve the motion management of SBRT for VT patients, by reducing the respiratory induced motion in the heart.

Favorable Survival after Definitive Ablative RT in Surgically Resectable Pancreatic Cancer Patients

Surgical resection has been considered the only curative option for patients with pancreatic adenocarcinoma (PDAC). Ablative RT ≥100Gy BED10 (A-RT) is associated with favorable survival in patients with locally advanced unresectable disease. We sought to evaluate A-RT outcomes in patients with technically resectable disease who did not undergo surgery. Our prospectively maintained database of patients treated with A-RT was queried for consecutive patients with radiographic T1/T2 resectable PDAC. Patients were treated with a standardized technique within a large academic cancer center regional network. Ablative RT using several hypofractionated regimens was delivered on either standard Linacs with respiratory motion management, CBCT image guidance and selective adaptive replanning or MR-Linac with compression belt and daily on-line adaptive replanning. Freedom from local progression (FFLP), distant metastasis-free and overall survival (DMFS and OS, respectively) were analyzed using the Kaplan Meier estimates. Between 2016 and 2022, 28 patients (54% male) with radiographically resectable PDAC received definitive A-RT. Median age was 80 (interquartile range, 77-84) years and 23 (82.1%) had KPS of 80 or below. Eighteen patients (64.3%) had T2 cancer, 5 (17.9%) were node positive, and 23 (82.1%) had head location. Median size was 2.6 (range, 1.6-4.0) cm with a median carbohydrate antigen 19-9 (CA19-9) of 160.5 (0-1823) U/mL. Twenty patients (71.4%) received induction chemotherapy for a median of 2.4 (0-6.2) months. RT regimens delivered on conventional Linacs unless otherwise indicated included 75Gy in 25 fractions (n = 15), 67.5Gy in 15 fractions (n = 10), 50Gy in 5 (N = 2, MR Linac), 60Gy in 10 (n = 1). 24-month FFLP and DMFS were 78.8% (52.3-91.7%) and 17.7% (95% CI, 5.8%-34.8%), respectively. 24-month and 48-month rate of OS from A-RT were 49.1% (95% CI, 27.53-67.5%) and 36.3 (95%16.0-57.1%). Grade 3 acute and late GI toxicity was noted in 3 and 1 patients, respectively, including 2 bleeding events treated with transfusions. There were no ≥ grade 4 events. In patients with surgically resectable PDAC we found that definitive A-RT following multiagent induction therapy was associated with oncologic outcomes similar to resection with minimal toxicity.

Stereotactic Body Radiotherapy (SBRT) for Adrenal Metastases: Practice Patterns at Community-Based Radiotherapy Centers

To analyze SBRT of adrenal metastases at free-standing centers within a large network in the USA, in order to guide institutional recommendations. We interrogated records of patients treated with SBRT to adrenal metastases from January 2019 to June 2022 from a database of 13,363 patients who were treated with SBRT at 21 community-based centers clustered into five regions within a network. We reported patient characteristics, frequency, survival rate, and biologically effective dose (BED10) prescribed, respiratory motion capture according to region and treatment year. Survival was calculated by Kaplan-Meier estimates. A total of 271 patients were treated to metastatic adrenal lesions (2.0% of all SBRT patients). Median age was 69.8 years (range 32-96). Frequency of treatment increased by an average of 4.5% per year over the period. Table 1 gives the frequency of primary tumor sites, histological types, and dose fractionations. It also shows the range of BED10 used. 91% received five fractions, and 6% received 3 fractions. Median BED10 was 72 Gy (mean 68.0 Gy SD = 18.7). The most common regimen was 8 Gy x 5 (n = 75, 28%), but ranged from 5 Gy x 5 (n = 20) to 10 Gy x 5 (n = 34). BED10 varied according to geographic region ranging from 61.2 Gy to 73.0 Gy (p = 0.01). Median BED was 72 or above in 2 of 5 regions and less than 72 in 3 regions. Respiratory motion capture simulation was done in 65.1% of cases and frequency varied across the 5 locations as shown in Table1 from 93.3% in region 1 to 41.7% in region 5 (p<.0001). 4D CT simulation was used in 46.2% of cases and use was relatively stable over time: 52.8% in July to December 2020 and 40.9% from January to June 2022 with no trend over time: p = .7635 At median follow-up 6.6 months (range 0.3-48.5), 203 (74.9%) of patients were alive with a median overall survival of 24.3 months. 1-year and 2-year survival was 72.7% and 51.5% respectively. Use of respiratory motion simulation was not significantly associated with survival p = 0.47. Despite variation in BED10 and respiratory motion management, 2-year overall survival was over 50% in patients treated with SBRT for adrenal metastases in a large community network. Further study will address refinement of recommendations regarding dose and other treatment characteristics and expansion of clinical research in this setting.

Real-world effectiveness and safety of stereotactic body radiotherapy for liver metastases with different respiratory motion management techniques.

Stereotactic body radiotherapy (SBRT) has been firmly established as atreatment choice for patients with oligometastases, as it has demonstrated both safety and efficacy by consistently achieving high rates of local control. Moreover, it offers potential survival benefits for carefully selected patients in real-world clinical settings. Between January 2008 and May 2020, atotal of 149 patients (with 414 liver metastases) received treatment. The Active Breathing Coordinator device was used for 68 patients, while respiratory gating was used for 65 and abdominal compression was used for 16patients. The most common histological finding was colorectal adenocarcinoma, with 37.6% of patients having three or more metastases, and 18% having two metastases. The prescribed dose ranged from 36 to 60 Gy, delivered in 3-5fractions. Local control rates at 2 and 3years were 76.1% and 61.2%, respectively, with no instances of local recurrence after 3years. Factors negatively impacting local control included colorectal histology, lower prescribed dose, and the occurrence of new liver metastases. The median overall survival from SBRT was 32months, with the presence of metastases outside the liver and the development of new liver metastases after SBRT affecting survival. The median disease-free survival was 10months. No substantial differences in both local control and survival were observed between the respiratory motion control techniques employed. Treatment tolerance was excellent, with only one patient experiencing acute gradeIV thrombocytopenia and two patients suffering from ≥ gradeII chronic toxicity. For radical management of single or multiple liver metastases, SBRT is an effective and well-tolerated treatment option. Regardless of the technology employed, experienced physicians can achieve similarly positive outcomes. However, additional studies are required to elucidate prognostic factors that can facilitate improved patient selection.

Liver stereotactic body radiation therapy without fiducial or retained ethiodized oil guidance warrants greater than 5 mm planning target volumes.

For liver stereotactic body radiation therapy (SBRT), the placement of fiducial markers or retained ethiodized oil by transarterial chemoembolisation (TACE) provides a landmark for consistent target localisation. TACE and fiducial markers are invasive procedures that harbour additional risks. We hypothesise that liver SBRT can be accurately delivered without the use of these invasive surrogate markers. We retrospectively identified 50 consecutive patients who underwent liver SBRT with respiratory motion management to a single lesion which exhibited retained ethiodized oil per prior TACE delivery. For each SBRT fraction, two manual rigid image registrations were performed by the treating physician. One using the liver contour as a surrogate for the target and second aligning only to the radio-opaque retained ethiodized oil of the treated lesion. The magnitude of the displacement vector between the two registration methods was used to assess the accuracy of target localisation if ethiodized oil was not present. For the 50 patients, a total of 244 analysable cone-beam CTs (CBCTs) were included (six CBCTs excluded due to poor ethiodized oil visualisation). Respiratory motion management techniques consisted of active breathing control for 13 and abdominal compression for 37 patients. Forty-two patients had peripheral lesions and eight had central lesions (<2 cm from left and right portal veins). The average target localisation offset between the two registration methods (i.e. liver contour vs. retained ethiodized oil alignment) for patients with a single peripheral or central liver lesion was 5.8 and 5.3 mm, respectively. Across all patients, the average change in target position exceeded 5 mm for image registration methods based on the liver contour alone versus the retained ethiodized oil region. This suggests that margins greater than 5 mm may be required for respiratory motion-managed liver SBRT treatments in patients who do not undergo prior TACE or fiducial placement.

Shallow kinetics induced by a metronome (SKIM): A novel contactless respiratory motion management.

As an alternative to conventional compression amidst the COVID-19 pandemic, we developed a contactless motion management strategy. By increasing the patient's breathing rate to induce shallow breathing with the aid of a metronome, our hypothesis is that the motion magnitude of the target may be minimized without physical contact or compression. Fourteen lung stereotactic body radiation therapy (SBRT) patients treated under fast shallow-breathing (FSB) were selected for inclusion in this retrospective study. Our proposed method is called shallow kinetics induced by a metronome (SKIM). We induce FSB by setting the beats-per-minute (BPM) high (typically in the range of 50-60). This corresponded to a patient breathing rate of 25-30 (breathing) cycles per minute. The magnitude of target motion in 3D under SKIM was evaluated using 4DCT datasets. Comparison with free breathing (FB) 4DCT was also made for a subset for which FB data available. The overall effectiveness of SKIM was evaluated with 18 targets (14 patients). Direct comparison with FB was performed with 12 targets (10patients). The vector norm mean±SD value of motion magnitude under SKIM for 18 targets was 8.2±4.1mm. The mean±SD metronome BPM was 54.9±4.0 in this group. The vector norm means±SD values of target motion for FB and SKIM in the 12 target sub-group were 14.6±8.5mm and 9.3±3.7mm, respectively. The mean±SD metronome BPM for this sub-group was 56.3±2.5. Compared with FB, SKIM can significantly reduce respiratory motion magnitude of thoracic targets. The difference in maximum motion reduction in the overall vector norm, S-I, and A-P directions was significant (p=0.033, 0.042, 0.011). Our proposed method can be an excellent practical alternative to conventional compression due to its flexibility and ease of implementation.

A Framework for Assessing the Effect of Cardiac and Respiratory Motion for Stereotactic Arrhythmia Radioablation Using a Digital Phantom With a 17-Segment Model: A STOPSTORM.eu Consortium Study

The optimal motion management strategy for patients receiving stereotactic arrhythmia radioablation (STAR) for the treatment of ventricular tachycardia (VT) is not fully known. We developed a framework using a digital phantom to simulate cardiorespiratory motion in combination with different motion management strategies to gain insight into the effect of cardiorespiratory motion on STAR. The 4-dimensional (4D) extended cardiac-torso (XCAT) phantom was expanded with the 17-segment left ventricular (LV) model, which allowed placement of STAR targets in standardized ventricular regions. Cardiac- and respiratory-binned 4D computed tomography (CT) scans were simulated for free-breathing, reduced free-breathing, respiratory-gating, and breath-hold scenarios. Respiratory motion of the heart was set to population-averaged values of patients with VT: 6, 2, and 1 mm in the superior-inferior, posterior-anterior, and left-right direction, respectively. Cardiac contraction was adjusted by reducing LV ejection fraction to 35%. Target displacement was evaluated for all segments using envelopes encompassing the cardiorespiratory motion. Envelopes incorporating only the diastole plus respiratory motion were created to simulate the scenario where cardiac motion is not fully captured on 4D respiratory CT scans used for radiation therapy planning. The average volume of the 17 segments was 6 cm3 (1-9 cm3). Cardiac contraction-relaxation resulted in maximum segment (centroid) motion of 4, 6, and 3.5 mm in the superior-inferior, posterior-anterior, and left-right direction, respectively. Cardiac contraction-relaxation resulted in a motion envelope increase of 49% (24%-79%) compared with individual segment volumes, whereas envelopes increased by 126% (79%-167%) if respiratory motion also was considered. Envelopes incorporating only the diastole and respiration motion covered on average 68% to 75% of the motion envelope. The developed LV-segmental XCAT framework showed that free-wall regions display the most cardiorespiratory displacement. Our framework supports the optimization of STAR by evaluating the effect of (cardio)respiratory motion and motion management strategies for patients with VT.

An analysis of the impact of different levels of inspiratory volume using active breathing control on the intrafraction motion and dose coverage of target volumes in patients undergoing thoracic radiotherapy

PurposeTo determine whether the level of inspiratory volume affect the extent to which active breathing control (ABC) reduces intrafraction motion and the dose coverage of target volumes in patients receiving external beam radiation therapy (EBRT) to the thoracic region Materials/methods20 patients undergoing thoracic radiotherapy enrolled in a prospective study using ABC for respiratory motion management and volumetric-modulated arc therapy (VMAT) as the treatment technique. They were randomized to one of two groups, the control group of 80% inspiratory volume and the other test group of 70%. At least one set of repeated CBCTs was done weekly. All images including CBCTs and Planning CTs were sent to MIM softwareTM for analysis of intrafraction motion using Dice Similarity Coefficient (DSC). The target dose conformality was assessed using conformation number (CN). Intention-to-treat analysis was employed for statistical purpose. ResultsThe DSC for the 70% and 80% inspiratory volume group were 0.93 and 0.92, respectively. For the 70% group, there was a significant negative correlation (p < 0.05) between DSC and time between two CBCTs, but not for the 80% group. The average percentage change in CN for the 70% and 80% group was 10.91% and 8.14%, respectively, and their difference was significant (p < 0.05). Furthermore, the actual change in volume had a significant positive correlation (p < 0.05) with the percentage change in CN for the 70% inspiratory volume group but not the 80% group. ConclusionMore evidence suggests that the target volumes from the 80% inspiratory volume group have less intrafraction motion compared to the 70% group. The findings from the percentage change in CN suggest that there could potentially be less tumor motion for higher levels of inspiratory volume and this could possibly contribute to why intrafraction motion is less for the 80% inspiratory volume group.

Clinical Factors That Affect Fiducial Tracking in Robotic SABR for Lung Tumors

SABR is a treatment option for patients with lung tumors that employs fiducials to track tumors during the breathing cycle. Currently, there is a paucity of data on how relative fiducial location and patient clinical characteristics affect fiducial tracking and clinical outcomes. This study aimed to identify factors that reduce the number of fiducials tracked with respiratory motion management during SABR. An institutional review board-approved retrospective review was performed of patients receiving robotic SABR for lung tumors at our institution from 2016 to 2019. Clinical data including demographics, medical history, treatment data, and follow-up were collected. Fiducial geometries were obtained with Velocity contouring software and MATLAB. Mann-Whitney U, χ2, and t tests were completed using MedCalc. A total of 73 patients with 77 treatments were identified. The χ2 analysis revealed that chronic obstructive pulmonary disease was associated with having 3 or more fiducials tracked (P=.034). Tumors in lower lobes were associated with higher rates of uncertainty errors (P=.015). The number of fiducials tracked had no effect on local tumor control or overall survival, with a median of 36 months of follow-up. A total of 28 treatments had fiducial centroid data available for geometric analysis. The most common tracking errors were rigid body error (RBE; 57%) and spacing errors (36.4%). Spacing errors had a shorter average minimum interfiducial distance than nonspacing errors (1.0 cm vs 1.7 cm, respectively; P=.017). RBE treatments had a longer average maximum distance than non-RBE treatments (4.0 cm vs 3.0 cm; P=.022). Greater motion in lower lobes can contribute to certain tracking errors that prevent more fiducials from being tracked. Maintaining interfiducial distance between experimentally determined guidelines may limit spacing errors and RBEs, the 2 most common tracking errors. An increased number of patients in a data set may result in stronger correlations between patient and tumor factors and outcomes.

Respiratory motion management using a single rapid MRI scan for a 0.35 T MRI-Linac system.

MRI has a rapidly growing role in radiation therapy (RT) for treatment planning, real-time image guidance, and beam gating (e.g., MRI-Linac). Free-breathing 4D-MRI is desirable in respiratory motion management for therapy. Moreover, high-quality 3D-MRIs without motion artifacts are needed to delineate lesions. Existing MRI methods require multiple scans with lengthy acquisition times or are limited by low spatial resolution, contrast, and signal-to-noise ratio. We developed a novel method to obtain motion-resolved 4D-MRIs and motion-integrated 3D-MRI reconstruction using a single rapid (35-45 s scan on a 0.35 T MRI-Linac. Golden-angle radial stack-of-stars MRI scans were acquired from a respiratory motion phantom and 12 healthy volunteers (n=12) on a 0.35 T MRI-Linac. A self-navigated method was employed to detect respiratory motion using 2000 (acquisition time=5-7 min) and the first 200 spokes (acquisition time=35-45 s). Multi-coil non-uniform fast Fourier transform (MCNUFFT), compressed sensing (CS), and deep-learning Phase2Phase (P2P) methods were employed to reconstruct motion-resolved 4D-MRI using 2000 spokes (MCNUFFT2000) and 200 spokes (CS200 and P2P200). Deformable motion vector fields (MVFs) were computed from the 4D-MRIs and used to reconstruct motion-corrected 3D-MRIs with the MOtion Transformation Integrated forward-Fourier (MOTIF) method. Image quality was evaluated quantitatively using the structural similarity index measure (SSIM) and the root mean square error (RMSE), and qualitatively in a blinded radiological review. Evaluation using the respiratory motion phantom experiment showed that the proposed method reversed the effects of motion blurring and restored edge sharpness. In the human study, P2P200 had smaller inaccuracy in MVFs estimation than CS200. P2P200 had significantly greater SSIMs (p<0.0001) and smaller RMSEs (p<0.001) than CS200 in motion-resolved 4D-MRI and motion-corrected 3D-MRI. The radiological review found that MOTIF 3D-MRIs using MCNUFFT2000 exhibited the highest image quality (scoring>8 out of 10), followed by P2P200 (scoring>5 out of 10), and then motion-uncorrected (scoring<3 out of 10) in sharpness, contrast, and artifact-freeness. We have successfully demonstrated a method for respiratory motion management for MRI-guided RT. The method integrated self-navigated respiratory motion detection, deep-learning P2P 4D-MRI reconstruction, and a motion integrated reconstruction (MOTIF) for 3D-MRI using a single rapid MRI scan (35-45 s) on a 0.35 T MRI-Linac system.

PO-04-095 ACCURATE EAM-BASED TARGET DELINEATION IN STEREOTACTIC ARRHYTHMIA RADIOABLATION OF VT

Stereotactic Arrhythmia Radiotherapy (STAR) aided by precise image-guided delivery and respiratory motion management has been used successfully for experimental treatment of refractory VT. However, accurate target selection remains challenging. Current methods often rely on manual delineation and/or visual estimation of predefined cardiac segments. Develop a systematic process for registering VT targets from electroanatomic maps (EAM) to reference imaging coordinates of the planning CT (pCT) used for radiation treatment. The goal is to minimize potential variations in target site selection as well as treated volumes. In patients on antiarrhythmic treatment and undergoing a 2nd unsuccessful VT ablation, EA maps of the LV (and LA/RV when possible) and more focal maps of VT target sites were acquired (CARTO®3, Biosense-Webster, CA, USA) and exported. In-house software was used to register these to a planning image set and convert them to DICOM structure files (Fig 1). Dice similarity coefficients were calculated between ventricular mesh data and corresponding reference contours. Initial targets (GTV) were expanded to include internal target volumes (ITV) and planning target volumes (PTV) to account for respiratory and cardiac motion and residual uncertainties, with minor manual adjustments guided by consensus among electrophysiologists, radiation oncologists and medical physicists. STAR was delivered as a single fraction of 25 Gy using volumetric-modulated arc therapy or dynamic conformal arc therapy depending on the target shape. 7 patients with refractory VT were treated by defining targets based on registering individualized EAM maps on the planning images. Dice similarity indices between transferred reference map and reference contours were 0.83 ± 0.04 and 0.72 ± 0.04 for LV and LA/RV, respectively (table 1). The median clinical target was 22cc, with PTVs ranging from 62.4 to 199.6 cc. All patients demonstrated a significant reduction in VT events by 6 weeks post STAR. We have developed an effective methodology for direct registration of VT targets selected for STAR, based on direct anatomic registration of individualized EA maps acquired during ablation procedures. This process offers a way to efficiently delineate variable target boundaries in a semi-automated way, which is advantageous when unusual contours make standard segmentation inaccurate and visual estimation difficult. However, rigorous comparison with other approaches remains to be done.Tabled 1Patient-specific metrics1234567Dice, LV0.8680.8450.7910.8060.7210.8720.794Dice, LA/RV0.7520.6670.734N/A0.382N/A0.338GTV (cc)22.313.526.520.759.863.927.2ITV (cc)45.529.142.230.959.8127.829.6PTV (cc)98.662.488.275.5166.8199.672.8 Open table in a new tab

A survey of practice patterns for real-time intrafractional motion-management in particle therapy.

Organ motion compromises accurate particle therapy delivery. This study reports on the practice patterns for real-time intrafractional motion-management in particle therapy to evaluate current clinical practice and wishes and barriers to implementation. An institutional questionnaire was distributed to particle therapy centres worldwide (7/2020-6/2021) asking which type(s) of real-time respiratory motion management (RRMM) methods were used, for which treatment sites, and what were the wishes and barriers to implementation. This was followed by a three-round DELPHI consensus analysis (10/2022) to define recommendations on required actions and future vision. With 70 responses from 17 countries, response rate was 100% for Europe (23/23 centres), 96% for Japan (22/23) and 53% for USA (20/38). Of the 68 clinically operational centres, 85% used RRMM, with 41% using both rescanning and active methods. Sixty-four percent used active-RRMM for at least one treatment site, mostly with gating guided by an external marker. Forty-eight percent of active-RRMM users wished to expand or change their RRMM technique. The main barriers were technical limitations and limited resources. From the DELPHI analysis, optimisation of rescanning parameters, improvement of motion models, and pre-treatment 4D evaluation were unanimously considered clinically important future focus. 4D dose calculation was identified as the top requirement for future commercial treatment planning software. A majority of particle therapy centres have implemented RRMM. Still, further development and clinical integration were desired by most centres. Joint industry, clinical and research efforts are needed to translate innovation into efficient workflows for broad-scale implementation.

Erratum: “Evaluation of radixact motion synchrony for 3D respiratory motion: Modeling accuracy and dosimetric fidelity”

Journal of Applied Clinical Medical PhysicsVolume 24, Issue 1 e13805 ERRATUMOpen Access Erratum: “Evaluation of radixact motion synchrony for 3D respiratory motion: Modeling accuracy and dosimetric fidelity” This article corrects the following: Evaluation of radixact motion synchrony for 3D respiratory motion: Modeling accuracy and dosimetric fidelity William S. Ferris, Michael W. Kissick, John E. Bayouth, Wesley S. Culberson, Jennifer B. Smilowitz, Volume 21Issue 9Journal of Applied Clinical Medical Physics pages: 96-106 First Published online: July 21, 2020 First published: 20 January 2023 https://doi.org/10.1002/acm2.13805AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat In Ferris et al.,1 the corresponding author has requested to update the Conflict of Interest. The Conflict of Interest should be updated as below. Michael Kissick is employed by and has ownership interest in Accuray, Inc. John E Bayouth has ownership interest in MR guidance, LLC, which has business activity with a company that utilizes respiratory motion management (ViewRay, Inc.). The remaining authors have no conflicts of interest to disclose. REFERENCE 1Ferris WS, Kissick MW, Bayouth JE, et al. Evaluation of radixact motion synchrony for 3D respiratory motion: Modeling accuracy and dosimetric fidelity. J Appl Clin Med Phys. 2020; 21: 96- 106. Volume24, Issue1January 2023e13805 ReferencesRelatedInformation

Patient-specific respiratory motion management using lung tumors vs fiducial markers for real-time tumor-tracking stereotactic body radiotherapy.

In real-time lung tumor-tracking stereotactic body radiotherapy (SBRT), tracking accuracy is related to radiotherapy efficacy. This study aimed to evaluate the respiratory movement relationship between a lung tumor and a fiducial marker position in each direction using four-dimensional (4D) computed tomography (CT) images. A series of 31 patients with a fiducial marker for lung SBRT was retrospectively analyzed using 4DCT. In the upper (UG) and middle and lower lobe groups (MLG), the cross-correlation coefficients of respiratory movement between the lung tumor and fiducial marker position in four directions (anterior-posterior, left-right, superior-inferior [SI], and three-dimensional [3D]) were calculated for each gating window (≤1, ≤2, and≤3mm). Subsequently, the proportions of phase numbers in unplanned irradiation (with lung tumors outside the gating window and fiducial markers inside the gating window) were calculated for each gating window. In the SI and 3D directions, the cross-correlation coefficients were significantly different between UG (mean r=0.59, 0.63, respectively) and MLG (mean r=0.95, 0.97, respectively). In both the groups, the proportions of phase numbers in unplanned irradiation were 11%, 28%, and 63% for the≤1-, ≤2-, and≤3-mm gating windows, respectively. Compared with MLG, fiducial markers for UG have low cross-correlation coefficients between the lung tumor and the fiducial marker position. Using 4DCT to assess the risk of unplanned irradiation in a gating window setting and selecting a high cross-correlation coefficient fiducial marker in advance are important for accurate treatment using lung SBRT.

Results from the AAPM Task Group 324 respiratory motion management in radiation oncology survey.

To quantify the clinical practice of respiratory motion management in radiation oncology. 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. 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. 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.

Surface Imaging-Guided Adaptive Radiotherapy (ART): Imaging Protocol and Verification for Inter- and Intra-Fractional Motion Managements

<h3>Purpose/Objective(s)</h3> CBCT-guided adaptive radiotherapy (CT-ART) has proven to account for inter-fractional anatomic changes. However, no commercial solution for intra-fractional respiratory motion management existed in CT-ART. Therefore, we investigated intra-fractional motion-managed treatment strategies in CT-ART (or Image-guided RT: IGRT) using optical surface imaging combined with <i>in-situ</i> CBCTs. <h3>Materials/Methods</h3> Eight of ten cancer patients with mobile lower lung or upper abdominal malignancies have completed CT-ART (or IGRT) using Ethos radiotherapy in an IRB-approved clinical trial (phase I). Four of the eight patients underwent additional MR simulations, including cine MRIs, to estimate the tumor/abdominal skin motion correlation. In CT-ART, a pre-configured gating window (±2 mm in vertical position) on surface imaging was used for manually triggering intra-fractional CBCT and treatment beam irradiation in breath-hold (six patients for exhalation and two patients for inhalation). A donut-shaped imaging-surrogate on patient's abdomen was used to localize Region of Interest (ROI) of the abdomen on CBCTs. Two inter-fractional CBCTs at exhalation and inhalation in each fraction were acquired to verify the tumor/imaging-surrogate motions range. Intra-fractional CBCTs were used to quantify the residual motion of the tumor/imaging-surrogate within the pre-configured gating window. Tumor motion was measured by tracking the position of a tumor centroid. <h3>Results</h3> The pre-configured gating window on surface imaging was confirmed based on the correlation of the tumor and abdominal skin motions using cine MRIs. Thirty-six pairs of inter-fractional CBCTs and 100 intra-fractional CBCTs from 36 fractions were analyzed (13 fractions for IGRT and 23 for ART). In the motion range study from the inter-fractional CBCTs, the values of mean ± std were 17.3 ± 12.0 mm in the SI direction for the tumors and 16.6 ± 7.9 mm in the AP direction for the imaging-surrogate, respectively. The residual motion of the imaging-surrogate from intra-fractional CBCTs was 2.5 ± 2.1 mm for SI, 2.3 ± 2.0 mm for RL, and 2.1 ± 2.3 mm for AP directions. The residual motion of the tumors was 2.4 ± 3.1 mm for SI, 2.3 ± 2.3 mm for RL, and 2.2 ± 2.0 mm for AP directions. Trends in the residual motion during the course of treatment fractions and over time through delivery were stable. Inter-fractional residual motions of the tumors were 2.3 ± 0.8 mm for SI, 2.3 ± 0.6 mm for RL, and 2.2 ± 0.7 mm for AP directions. Intra-fractional residual motions of the tumors were 2.4 ± 0.9 mm for SI, 2.4 ± 0.7 mm for RL, and 3.2 ± 1.3 mm for AP. <h3>Conclusion</h3> We demonstrated the inter- and intra-fractional motion-managed treatment strategies in CBCT-guided ART using surface imaging. Since the residual motion of the tumors was comparable to that of the imaging-surrogate within clinical PTV margins (5 mm) but a bit larger than the pre-configured gating window, additional caution is needed with intra-fractional motion management in CT-ART using the optical surface imaging.

Adoption of respiratory motion management in radiation therapy.

Background and PurposeA survey on the patterns of practice of respiratory motion management (MM) was distributed to 111 radiation therapy facilities to inform the development of an end-to-end dosimetry audit including respiratory motion.Materials and methodsThe survey (distributed via REDCap) asked facilities to provide information specific to the combinations of MM techniques (breath-hold gating – BHG, internal target volume – ITV, free-breathing gating – FBG, mid-ventilation – MidV, tumour tracking – TT), sites treated (thorax, upper abdomen, lower abdomen), and fractionation regimes (conventional, stereotactic ablative body radiation therapy – SABR) used in their clinic.ResultsThe survey was completed by 78% of facilities, with 98% of respondents indicating that they used at least one form of MM. The ITV approach was common to all MM-users, used for thoracic treatments by 89% of respondents, and upper and lower abdominal treatments by 38%. BHG was the next most prevalent (41% of MM users), with applications in upper abdominal and thoracic treatment sites (28% vs 25% respectively), but minimal use in the lower abdomen (9%). FBG and TT were utilised sparingly (17%, 7% respectively), and MidV was not selected at all.ConclusionsTwo distinct treatment workflows (including use of motion limitation, imaging used for motion assessment, dose calculation, and image guidance procedures) were identified for the ITV and BHG MM techniques, to form the basis of the initial audit. Thoracic SABR with the ITV approach was common to nearly all respondents, while upper abdominal SABR using BHG stood out as more technically challenging. Other MM techniques were sparsely used, but may be considered for future audit development.