Apnea Research Articles

Comparing interfractional stability of heart dose among three breath-hold radiotherapy techniques in breast cancer

IntroductionBreath holding can reduce the cardiac dose in radiotherapy for left-sided breast cancer. We evaluated whether any of the existing commonly used breath-hold techniques was superior in maintaining a more reproducible mean heart dose (MHD) during treatment. Methods and MaterialsThis was a single-institution, interventional, non-randomized, three-armed prospective trial, comparing the reproducibility of MHD in breath-hold radiotherapy using voluntary deep inspiration breath hold (vDIBH), active breathing control (ABC) and surface guided radiotherapy (SGRT). The MHD were determined based on the anatomy in planning computer tomography and each weekly cone beam computer tomography (CBCT) during radiotherapy. The reproducibility of MHD was measured by calculating the interfractional variation of MHD (represented by the standard deviation) across the CBCT, and the difference between the cumulative MHD at CBCT and at planning CT. These two measures of reproducibility were then compared among vDIBH, ABC and SGRT. ResultsOf the 55 patients recruited, 19 had ABC, 20 had SGRT and 16 had vDIBH. SGRT was associated with a slightly greater interfractional variation of the MHD, compared with vDIBH (Least Square Means (LSM): 28.8cGy (SGRT) vs 10.5cGy (vDIBH), p=0.0052) and ABC (LSM: 28.8cGy (SGRT) vs 15.1cGy (ABC), p=0.026). In the SGRT group, the cumulative MHD at CBCT was lower than that at planning CT (mean difference: -22.1cGy, p=0.013). No such difference existed in vDIBH and ABC. In terms of the reproducibility of cumulative MHD at CBCT as compared to that in planning CT, there was no significant difference between vDIBH (mean: -12.1cGy), ABC (mean: -4.8cGy) and SGRT (mean: -22.1cGy) (p-value for pairwise comparison all >0.1). ConclusionSGRT was associated with a slightly greater interfractional variation of MHD compared with vDIBH and ABC, but the difference may not be clinically significant. All three breath-hold techniques were broadly comparable in their reproducibility of MHD at CBCT relative to the planning CT.

Abstract TMP55: The Impact of Statin Intensity on Cerebral Vasomotor Reactivity, White Matter Hyperintensities, and Micro-Bleeds in Stroke Patients

Background: Cerebral vasomotor reactivity (VMR) is crucial for regulating cerebral blood flow and neurological health. Research suggests that high-intensity statin therapy may improve VMR shortly after a stroke. This study aims to evaluate the duration of this improvement over three months and explore the association between white matter hyperintensities (WMH), cerebral micro-bleeding (CMB), and VMR as an endothelial function marker. Methods: We enrolled 120 ischemic stroke patients from July 2023 to June 2024 at an academic stroke center. Patients were divided retrospectively into high-intensity (40 or 80 mg Atorvastatin or equivalent) and moderate to low-intensity (10-20 mg Atorvastatin or equivalent) statin therapy groups. VMR was assessed using the Breath Holding Index (BHI) via transcranial Doppler ultrasound at two weeks and three months post-stroke. We analyzed the correlation between WMH, CMB, and VMR across different statin doses using multivariable regression, adjusting for baseline NIHSS, demographics, cerebrovascular risk factors, WMH, and CMB. Results: The cohort had an average age of 69.8 years, with 50.8% being male. High-intensity statins were used by 63 patients (52.5%). At baseline, the high-intensity group had a significantly higher BHI (Mean VMR: 0.9 vs. 0.7, P < 0.008), which remained higher at the three-month follow-up (Mean VMR: 0.8 vs. 0.7, P < 0.001). Baseline WMH was present in 29.2% of patients, and 18.3% had CMB. Patients with lower baseline VMR had a higher incidence of WMH (53.5% vs. 6.5%, P < 0.001), which persisted at three months (55.6% vs. 7.6%, P < 0.001). Lower baseline VMR was also associated with higher CMB rates (37.9% vs. 0%, P < 0.001), continuing at three months (40.7% vs. 0%, P < 0.001). The average baseline BHI was 0.65 in patients with WMH versus 0.81 in those without WMH (P < 0.001) and 0.64 in patients with CMB versus 0.79 in those without CMB (P < 0.001). Conclusion: High-intensity statin therapy positively affects VMR in stroke patients over three months. Lower VMR is associated with increased WMH and CMB, suggesting that optimizing statin treatment may improve vascular health and reduce stroke recurrence risk. Future research should investigate these findings further and assess the long-term effects of statin therapy on VMR and recurrent cerebrovascular events.

A systematic review of deep inspiration breath hold and free breathing in proton beam therapy plans for breast cancer radiotherapy

A systematic review of deep inspiration breath hold and free breathing in proton beam therapy plans for breast cancer radiotherapy

Automated vs manual cardiac MRI planning: a single-center prospective evaluation of reliability and scan times.

Evaluating the impact of an AI-based automated cardiac MRI (CMR) planning software on procedure errors and scan times compared to manual planning alone. Consecutive patients undergoing non-stress CMR were prospectively enrolled at a single center (August 2023-February 2024) and randomized into manual, or automated scan execution using prototype software. Patients with pacemakers, targeted indications, or inability to consent were excluded. All patients underwent the same CMR protocol with contrast, in breath-hold (BH) or free breathing (FB). Supervising radiologists recorded procedure errors (plane prescription, forgotten views, incorrect propagation of cardiac planes, and field-of-view mismanagement). Scan times and idle phase (non-acquisition portion) were computed from scanner logs. Most data were non-normally distributed and compared using non-parametric tests. Eighty-two patients (mean age, 51.6 years ± 17.5; 56 men) were included. Forty-four patients underwent automated and 38 manual CMRs. The mean rate of procedure errors was significantly (p = 0.01) lower in the automated (0.45) than in the manual group (1.13). The rate of error-free examinations was higher (p = 0.03) in the automated (31/44; 70.5%) than in the manual group (17/38; 44.7%). Automated studies were shorter than manual studies in FB (30.3 vs 36.5 min, p < 0.001) but had similar durations in BH (42.0 vs 43.5 min, p = 0.42). The idle phase was lower in automated studies for FB and BH strategies (both p < 0.001). An AI-based automated software performed CMR at a clinical level with fewer planning errors and improved efficiency compared to manual planning. Question What is the impact of an AI-based automated CMR planning software on procedure errors and scan times compared to manual planning alone? Findings Software-driven examinations were more reliable (71% error-free) than human-planned ones (45% error-free) and showed improved efficiency with reduced idle time. Clinical relevance CMR examinations require extensive technologist training, and continuous attention, and involve many planning steps. A fully automated software reliably acquired non-stress CMR potentially reducing mistake risk and increasing data homogeneity.

Development of a machine learning tool to predict deep inspiration breath hold requirement for locoregional right-sided breast radiation therapy patients

Background and purpose. This study presents machine learning (ML) models that predict if deep inspiration breath hold (DIBH) is needed based on lung dose in right-sided breast cancer patients during the initial computed tomography (CT) appointment.Materials and methods. Anatomic distances were extracted from a single-institution dataset of free breathing (FB) CT scans from locoregional right-sided breast cancer patients. Models were developed using combinations of anatomic distances and ML classification algorithms (gradient boosting, k-nearest neighbors, logistic regression, random forest, and support vector machine) and optimized over 100 iterations using stratified 5-fold cross-validation. Models were grouped by the number of anatomic distances used during development; those with the highest validation accuracy were selected as final models. Final models were compared based on their predictive ability, measurement collection efficiency, and robustness to simulated user error during measurement collection.Results. This retrospective study included 238 patients treated between 2016 and 2021. Model development ended once eight anatomic distances were included, and the validation accuracy plateaued. The best performing model used logistic regression with four anatomic distances achieving 80.5% average testing accuracy, with minimal false negatives and positives (<27%). The anatomic distances required for prediction were collected within 3 min and were robust to simulated user error during measurement collection, changing accuracy by <5%.Conclusion. Our logistic regression model using four anatomic distances provided the best balance between efficiency, robustness, and ability to predict if DIBH was needed for locoregional right-sided breast cancer patients.

Evaluation of Knowledge and Skills of Postgraduate Medical Students and Healthcare Assistants in Managing Asthma Using Metered-Dose Inhalers

Background: Asthma remains a significant global health concern, with its rising prevalence particularly challenging in low- and middle-income countries due to factors such as pollution, urbanization, and inadequate healthcare infrastructure. The purpose of this study was to evaluate the knowledge and skills of postgraduate medical students and healthcare assistants in managing asthma using metered-dose inhalers, with the goal of identifying gaps to inform targeted training and educational interventions. Aim of the study: The aim of the study was to assess the knowledge and skills of postgraduate medical students and healthcare assistants in managing asthma using metered-dose inhalers. Methods: This cross-sectional observational study in the Department of Internal Medicine at Bangabandhu Sheikh Mujib Medical University (BSMMU) Hospital, Dhaka, was conducted from July to December 2015, involving 200 postgraduate medical students &amp; health-assistants (nurses, ward-boys, pharmacists, drug dispensers). Data were collected through structured interviews and observations, analyzed using SPSS version 17.0, and Chi-square tests, with a significance threshold of p &lt; 0.05. Ethical approval and informed consent were obtained. Results: In a study of 200 postgraduate medical students &amp; health- assistants, with a mean age of 30.8 years, 57.4% were male, and 50% were postgraduate medical students 25% were nurses, 15% were ward-boys, 5% were pharmacist &amp; 5% were drug dispensers. All counseled-on inhaler use, but only 71.8% recommended medications. Most performed initial inhaler steps well, but adherence to final steps was inconsistent. Post gradual medical students generally outperformed nurses &amp; other health- assistants, except in "Breathe out slowly and completely" and "Hold breath for 10-15 seconds" and the nurses out-perform the pharmacist. Conclusion: Postgraduate medical students display varied proficiency in metered-dose inhaler techniques, with final steps showing ...

Sex-based variations in breath-holding: oxygen storage and diving response among non-divers.

Breath-hold diving performances are typically better in men than in women. However, it is still being determined if there are differences in the physiological responses to breath-holding between the sexes. We conducted a study comparing the maximum breath-hold duration, heart rate (HR) reduction, peripheral oxygen saturation (SpO2), and spleen volume and contraction in 37 men and 44 women, all of whom had no prior breath-holding experience. They performed two dry apneas separated by 2min; the first was limited to 60s, followed by a maximal effort apnea. HR and SpO2 were measured continuously. Spleen diameters were measured via ultrasonography before and immediately following each apnea. The maximal apneic duration was longer in men (78 ± 19s) compared with women (61 ± 18s, p < 0.001), while the HR reduction was similar (women: 16% ± 19% versus men: 16% ± 17%, p = 0.973). The absolute splenic contraction was greater in men (59 ± 56mL) compared with women (35 ± 28mL, p < 0.001) in the first apnea, while the relative contraction was similar (women: 21% ± 17% versus men: 23% ± 13%, p = 0.528). In addition, the lowest SpO2 during the maximal apnea was similar between sexes (women: 93.3% ± 4.4%; men: 91.9% ± 4.3%, p = 0.161). We conclude that men have larger spleen size and contraction, lung size, and maximal apneic duration than women. The cardiovascular diving response is similar between sexes for those inexperienced with apneic diving. The longer breath-hold duration in men may be partly due to greater oxygen storage capacity, which results from larger vital capacity and greater spleen size and contraction.

Evolving Trends and Patterns of Utilization of Magnetic Resonance-Guided Radiotherapy at a Single Institution, 2018-2024.

Background/Objectives: Over the past decade, significant advances have been made in image-guided radiotherapy (RT) particularly with the introduction of magnetic resonance (MR)-guided radiotherapy (MRgRT). However, the optimal clinical applications of MRgRT are still evolving. The intent of this analysis was to describe our institutional MRgRT utilization patterns and evolution therein, specifically as an early adopter within a center endowed with multiple other technology platforms. Materials/Methods: We retrospectively evaluated patterns of MRgRT utilization for patients treated with a 0.35-Tesla MR-Linac at our institution from April 2018 to April 2024. We analyzed changes in utilization across six annualized periods: Period 1 (April 2018-April 2019) through Period 6 (April 2023-April 2024). We defined ultra-hypofractionation (UHfx) as 5 or fewer fractions with a minimum fractional dose of 5 Gy. Electronic health records were reviewed, and data were extracted related to patient, tumor, and treatment characteristics. Results: A total of 823 treatment courses were delivered to 712 patients treated for 854 lesions. The most commonly treated sites were the pancreas (242 [29.4%]), thorax (172; 20.9%), abdominopelvic lymph nodes (107; 13.0%), liver (72; 8.7%), and adrenal glands (68; 8.3%). The median total prescribed dose of 50 Gy in five fractions (fxs) was typically delivered in consecutive days with automatic beam gating in inspiration breath hold. The median biologically effective dose (α/β = 10, BED10) was 94.4 Gy with nearly half (404, 49.1%) of all courses at a prescribed BED10 ≥ 100 Gy, which is widely regarded as a highly effective ablative dose. Courses in Period 6 vs. Period 1 more often had a prescribed BED10 ≥ 100 Gy (60.2% vs. 41.6%; p = 0.004). Of the 6036 total delivered fxs, nearly half (2643, 43.8%) required at least one fx of on-table adaptive radiotherapy (oART), most commonly for pancreatic tumors (1081, 17.9%). UHfx was used in over three quarters of all courses (630, 76.5%) with 472 (57.4%) of these requiring oART for at least one fraction. The relative utilization of oART increased significantly from Period 1 to Period 6 (37.6% to 85.0%; p < 0.001); a similar increase in the use of UHfx (66.3% to 89.5%; p < 0.001) was also observed. The median total in-room time for oART decreased from 81 min in Period 1 to 45 min in Period 6, while for non-oART, it remained stable around 40 min across all periods. Conclusions: Our institution implemented MRgRT with a priority for targeting mobile extracranial tumors in challenging anatomic locations that are frequently treated with dose escalation, require enhanced soft-tissue visualization, and could benefit from an ablative radiotherapy approach. Over the period under evaluation, the use of high-dose ablative doses (BED10 ≥ 100 Gy), oART and UHfx (including single-fraction ablation) increased significantly, underscoring both a swift learning curve and ability to optimize processes to maximize throughput and efficiency.

Cardiac dose comparison of abdominal and thoracic deep inspiration breath hold in adult female with left-sided breast cancer receiving radiation therapy: A systematic review and meta-analysis.

Deep inspiration breath hold technique has shown promise in reducing cardiac toxicity and improving patient outcomes. However, there is a lack of consensus regarding the implementation of abdominal breath hold technique and its impact on cardiac dose. This systematic review and meta-analysis aim to provide insights into the comparative effectiveness of abdominal and thoracic breath hold in mitigating cardiac toxicity during radiation therapy for left-sided breast cancer. A comprehensive literature search was conducted in electronic databases (PubMed, Medline, Science Direct) to identify relevant studies. Dosimetric comparison studies between abdominal and thoracic breath hold conducted on adult female patients with primary left-sided breast cancer undergoing DIBH radiation therapy were included. Random effects meta-analyses were performed to estimate pooled effect sizes, and heterogeneity was evaluated using I2 statistic. A total of four studies, encompassing 166 patients, were included in the review. Meta-analysis revealed a statistically significant reduction in the mean dose to the left anterior descending artery with abdominal breath hold compared to thoracic breath hold (2.03Gy, 95%CI 0.58-3.47). No significant difference was observed in mean heart dose between the two techniques (0Gy, 95%CI -0.28-0.27). Variations in patient coaching and radiation therapy planning practices may impact the achieved cardiac dose reduction. Further studies are warranted to evaluate long-term clinical outcomes associated with different DIBH techniques and optimize treatment planning strategies in left-sided breast radiation therapy. Results of the study suggested that implementation of abdominal DIBH may reduce the potential risk of radiation-related cardiac complications. By establishing consistent standards for coaching techniques, radiation therapists can promote uniformity in training and improve the accuracy and reproducibility of breath hold treatments.

Estimation of heart dose in left breast cancer radiotherapy: Assessment of vDIBH feasibility using the supervised machine learning algorithm.

The volunteer deep inspiration breath hold (vDIBH) technique is used to reduce the heart dose in left breast cancer radiotherapy. Many times, it is faced that despite rigorous exercise and training, not all patients get benefited as expected. The primary objective of this study was to develop a machine learning program for prediction of mean heart dose before left breast radiotherapy under vDIBH. The present work is based on the dosimetric parameters of eighty-two left breast cancer patients, who have undergone modified radical mastectomy, enrolled for their radiation treatment. The trained machine learning algorithm employed linear regression to establish a correlation between Haller Index and heart mean dose (HMD) received during the ca left breast cancer radiotherapy. Subsequently, HMD values were used to model the regression relationship with maximum heart distance (MHD). The method adopted is beneficial in patient selection and assessment for suitability of patients' radiotherapy planning under vDIBH treatment technique. For data from 21 test patients, the mean of HMD obtained from the treatment planning system (TPS) and the mean of predicted HMD by developed program were found to be 468.76 cGy and 464.66 cGy, respectively. The present work facilitates precise HMD prediction in left breast cancer radiation therapy even before starting the treatment planning process. Additionally, this program offers suggestions in terms of modifications in treatment settings for even better results of vDIBH techniques if not matches with the anticipated results.

Breath-Holding as a Stimulus to Assess Peripheral Oxygenation Flow Using Near-Infrared Spectroscopic Imaging.

A mammalian breath-hold (BH) mechanism can induce vasoconstriction in the limbs, altering blood flow and oxygenation flow changes in a wound site. Our objective was to utilize a BH paradigm as a stimulus to induce peripheral tissue oxygenation changes via studies on control and diabetic foot ulcer (DFU) subjects. Subjects were imaged under a breath-hold paradigm (including 20 s BH) using a non-contact spatio-temporal-based NIRS device. Oxygenated flow changes were similar between darker and lighter skin colors but differed between wound site and normal background tissues. Thus, the ability of peripheral vasculature to response to oxygenation demand can be assessed in DFUs.

Cognitive impairments after maximal repeated breath-holding in elite breath-hold divers.

Breath-hold (BH) training over several years may result in mild but persistent neurocognitive impairment. Paradoxically, the acute effects of repeated BH generating intermittent hypoxia on neurocognitive functions are still poorly understood. Therefore, we decided to examine the impact of five-repeated maximal BH on attention, processing speed, and reasoning abilities. Thirty six men separated in 3 groups (12 elite BH divers: E<inf>BHD</inf>; 12 novice BH divers: N<inf>BHD</inf>; and 12 non BH divers: CTL) performed before and after 5 maximal BHs, neuropsychological computerized tasks sensitive to hypoxia. Heart rate (HR) and peripheral oxygen saturation were recorded continuously during all tests. Immediately after the five BHs, all the participants presented lower response time on the visual reaction task. E<inf>BHD</inf> did not exhibit difference in neuropsychological performance compared to N<inf>BHD</inf> and CTL, despite enduring longer BH durations. Regardless of BHD training level, repeated maximal BH may affect certain aspects of neuropsychological performance, in particularly visual reaction times. However, elite BHDs may have developed adaptive mechanisms that allow them to maintain their neurocognitive function at levels comparable to those of less trained BHDs and CTL, even with a higher dose of hypoxia.

CBCT-Based Online Adaptive Radiotherapy: A Promising Approach for Gastric Mucosa-Associated Lymphoid Tissue (MALT) Lymphoma?

PurposeDaily online adaptive radiotherapy (oART) opens the opportunity to treat gastric mucosa-associated lymphoid tissue (MALT) lymphoma with a reduced margin. This study reports our early experience of cone-beam computed tomography (CBCT)-based daily oART treating gastric MALT lymphoma with breath-hold (BH) and reduced margins. MethodsTen patients were treated on a CBCT-based oART system. Organs at risk (OARs) and the clinical target volume (CTV) were adjusted based on the daily CBCT. Planning target volume (PTV) was derived from the CTV with a 0.5-0.7 cm margin with BH. Multiple beam arrangements were compared during the preplanning phase to ensure minimal Monitor Unit (MU) for patient comfort and breath-hold reproducibility. For 108 fractions from the ten patients, the PTV, CTV coverage, Paddick Conformity Index (CI) were compared between the adapted and scheduled plans. The MU, Paddick CI, and gradient index (GI) were compared using relative percentage differences between the adapted plans and preplans. The OAR doses from 106 fractions across nine patients were reported for the preplans, adapted plans, and scheduled plans. The time statistics for each step of the clinical workflow were recorded and reported for 93 treatment fractions from nine patients. ResultsThe PTV volume varied from -37.1% to 90.5% (11.7% ± 18.5%) throughout treatments across all patients. The adapted plan was chosen as the treatment plan for each fraction due to superior PTV and CTV coverage while maintaining a similar OAR dose. The PTV and CTV coverage for the adapted and scheduled plans was VRx=95.0 ± 0.3% vs. 64.1 ± 19.6% and VRx=99.9 ± 0.1% vs. 74.0 ± 22.2%, respectively. The adapted plans' MU, Paddick CI, and GI were, on average, 4.1%, 0.4%, and -4.2% of the preplan values, respectively. The console's adaptive workflow and physician time were 25±7 and 19±6 minutes, respectively. ConclusionA CBCT-based oART system with the proposed workflow is feasible for treating gastric MALT lymphoma patients using a reduced PTV margin while maintaining excellent target coverage within a reasonable time, resulting in consistent adapted plan quality. This approach can be expanded to a larger cohort of gastrointestinal patients.

How to protect the proximal bronchial tree during stereotactic radiotherapy of ultracentral lung tumors: Lessons from MR-guided treatment.

To use imaging data from stereotactic MR-guided online adaptive radiotherapy (SMART) of ultracentral lung tumors (ULT) for development of a safe non-adaptive approach towards stereotactic body radiotherapy (SBRT) of ULT. Analysis is based on 19 patients with ULT who received SMART (10×5.0-5.5Gy) on a 0.35T MR-Linac (MRIdian®) in the prospective MAGELLAN trial. 4D-planning CT data of six patients served to quantify proximal bronchial tree (PBT) breathing motion. Daily fraction MRIs are used to calculate interfractional translations (mediolateral (ML), anterior-posterior (AP), superior-inferior (SI)) and their dosimetric consequences for the PBT. A planning risk volume (PRV) is calculated for an assumed non-adaptive SBRT in deep-inspiration breath hold (DIBH) with surface-guidance (AlignRT®). Finally, non-adaptive volumetric modulated arc (VMAT) SBRT is simulated with and without a PRV for N = 10 patients (10×5.5Gy). The PBT shows relevant breathing motion, especially in superior-inferior direction (median ML: 2.5mm, AP: 1.9mm and SI: 9.2mm). Furthermore, moderate interfractional translations are observed (mean absolute translation ML: 1.3mm, AP: 1.3mm, SI: 1.1mm), with an estimated 2mm PRV margin for interfractional changes alone. Simulated non-adaptive SBRT leads to PBT overdoses in 60% of patients (median overdosed fractions VMAT: 2.5, predicted MR-linac plans 4). Both MR-guided online plan adaptation (SMART) and PRV-based non-adaptive VMAT prevent PBT overdoses, but SMART yields significantly higher planning target volume (PTV) coverage (SMART: median 96% [IQR 95-96], VMAT: median 89% [IQR 77-94], p=0.014). Both intrafractional breathing motion and interfractional translations may impact doses to the PBT during SBRT of ULT. SMART protects the PBT from overdoses while maintaining high PTV coverage. Non-adaptive SBRT appears safe with advanced breathing motion management and PRV, but yields inferior PTV coverage.

Modern radiotherapy for breast cancer: Update and new developments

AbstractThe delivery of radiotherapy for breast cancer has evolved significantly over the years. The aim of this review is to highlight important developments and current concepts. Postoperative hypofractionated three-dimensional conformal or intensity-modulated photon radiotherapy continues to be the standard application after breast-conserving surgery to improve local control. New therapy techniques in deep inspiration breath hold or physical-biological advantages of proton beam therapy offer innovative therapy methods with regard to the protection of normal tissue and reduced cardiotoxicity. Ultra-hypofractionated therapy concepts and the integration of a simultaneous integrated boost in hypofractionated therapy concepts also enable the duration of treatment to be reduced to a few days or weeks. In low-risk constellations, the radiation volume may also be de-escalated to partial breast irradiation, and if life expectancy is severely restricted at the same time, the omission of postoperative radiotherapy might be critically discussed. The oncological benefit of an irradiation of the regional lymph node regions continues to be confirmed in locally advanced, node-positive carcinomas and further enables the omission of surgical axillary lymph node dissection with low morbidity in individualized therapy approaches.

Assessing Lung Ventilation and Bronchodilator Response in Asthma and Chronic Obstructive Pulmonary Disease with 19F MRI.

Background Pulmonary function tests are central to diagnosis and monitoring of respiratory diseases but do not provide information on regional lung function heterogeneity. Fluorine 19 (19F) MRI of inhaled perfluoropropane permits quantitative and spatially localized assessment of pulmonary ventilation properties without tracer gas hyperpolarization. Purpose To assess regional lung ventilation properties using 19F MRI of inhaled perfluoropropane in participants with asthma, participants with chronic obstructive pulmonary disease (COPD), and healthy participants, including quantitative evaluation of bronchodilator response in participants with respiratory disease. Materials and Methods This prospective, dual-center study included participants with asthma or COPD from July 2019 to September 2022 and healthy participants from May 2018 to June 2019. Participants underwent conventional spirometry, proton MRI, and 19F MRI following inhalation of a 79% perfluoropropane and 21% oxygen gas mixture. Three-dimensional 19F MRI scans were acquired during a single breath hold. For participants with asthma or COPD, spirometric and MRI measurements were repeated following administration of nebulized salbutamol. Ventilation defect percentage (VDP) was calculated from perfluoropropane distribution. Linear mixed-effects models were used to assess differences in VDP between participant groups and before and after bronchodilator administration. Results Thirty-five participants with asthma (mean age, 50 years ± 18 [SD]; 21 male participants), 21 participants with COPD (mean age, 69 years ± 6; 14 male participants), and 38 healthy participants (mean age, 41 years ± 11; 20 male participants) were evaluated. 19F MRI-derived VDP was elevated in participants with COPD (geometric mean, 27.2%) and participants with asthma (geometric mean, 8.3%) compared with healthy participants (geometric mean, 1.8%; geometric mean ratio, 15.2 [95% CI: 11.1, 20.6] for COPD and 4.6 [95% CI: 3.2, 6.6] for asthma; P < .001 for both). After bronchodilator administration, VDP was reduced by 33% in participants with asthma (from 8.3% to 5.6%) and 14% in participants with COPD (from 27.2% to 23.3%; P < .001 for both). Conclusion 19F MRI of inhaled perfluoropropane was sensitive to changes in regional ventilation properties associated with lung disease and enabled quantification of changes following bronchodilator therapy. Published under a CC BY-NC-ND 4.0 license. Supplemental material is available for this article. See also the editorial by Unger in this issue.

Systematizing the risk management process in clinical radiotherapy practice: Recommendations of the working group on risk management of the DGMP

PurposeThe Deutsche Gesellschaft für Medizinische Physik [German Society of Medical Physics] has recently published two coherent reports, No. 25 and No. 28, detailing the design and implementation of a risk management (RM) process for German radiotherapy (RT) departments. This study offers an overview and background of the efforts behind these reports. Methods and MaterialsFor three years, up to nine medical physicists (MPs) with practical RM experience held weekly meetings to develop recommendations for a clinical RM process. Care was taken to ensure that the recommendations were equally applicable to RT departments of various sizes. A process-based method derived from the failure mode and effects analysis (FMEA) was created to identify and address risks from unintentional radiation exposure. This method was applied to exemplarily analyze the hazardous scenarios in breast RT using surface guidance and deep inspiration breath hold (DIBH) techniques. Three common criticality methods—risk matrix, risk priority number, and action priority—were applied, and each step was schematically explained for first-time users. Each report was peer-reviewed by two radiation oncologists and 11 MPs. ResultsIn report No. 25, basic requirements were outlined for running the RM process, conducting risk assessments, and monitoring clinical procedures. A three-year plan-do-check-act cycle was proposed for continuous improvement. In report No. 28, general process lists for external beam radiotherapy (EBRT), brachytherapy, and radionuclide therapy were designed. Based on the EBRT process list, 45 hazardous scenarios in the surface-guided breast RT in DIBH were identified. Two scenarios were used to illustrate handling instructions for the three criticality methods. ConclusionsThe recommendations provide clinical MPs and other health professionals with a pragmatic approach to RM, balancing both the needs of smaller practices and larger clinics in Germany. The risk of unintended exposures of patients is viewed acceptable once it has been lowered to a state that is as low as reasonably achievable.

Quantitative mapping of cerebrovascular reactivity amplitude and delay with breath-hold BOLD fMRI when end-tidal CO2 quality is low.

Cerebrovascular reactivity (CVR), the ability of cerebral blood vessels to dilate or constrict in order to regulate blood flow, is a clinically useful measure of cerebrovascular health. CVR is often measured using a breath-hold task to modulate blood CO2 levels during an fMRI scan. Measuring end-tidal CO2 (PETCO2) with a nasal cannula during the task allows CVR amplitude to be calculated in standard units (vascular response per unit change in CO2, or %BOLD/mmHg) and CVR delay to be calculated in seconds. The use of standard units allows for normative CVR ranges to be established and for CVR comparisons to be made across subjects and scan sessions. Although breath-holding can be successfully performed by diverse patient populations, obtaining accurate PETCO2 measurements requires additional task compliance; specifically, participants must breathe exclusively through their nose and exhale immediately before and after each breath hold. Meeting these requirements is challenging, even in healthy participants, and this has limited the translational potential of breath-hold fMRI for CVR mapping. Previous work has focused on using alternative regressors such as respiration volume per time (RVT), derived from respiratory belt measurements, to map CVR. Because measuring RVT does not require additional task compliance from participants, it is a more feasible measure than PETCO2. However, using RVT does not produce CVR in standard units. In this work, we explored how to achieve CVR maps, in standard units, when breath-hold task PETCO2 data quality is low. First, we evaluated whether RVT could be scaled to units of mmHg using a subset of PETCO2 data of sufficiently high quality. Second, we explored whether a PETCO2 timeseries predicted from RVT using deep learning allows for more accurate CVR measurements. Using a dense-mapping breath-hold fMRI dataset, we showed that both rescaled RVT and rescaled, predicted PETCO2 can be used to produce maps of CVR amplitude and delay in standard units with strong absolute agreement to ground-truth maps. However, the rescaled, predicted PETCO2 regressor resulted in superior accuracy for both CVR amplitude and delay. In an individual with regions of increased CVR delay due to Moyamoya disease, the predicted PETCO2 regressor also provided greater sensitivity to pathology than RVT. Ultimately, this work will increase the clinical applicability of CVR in populations exhibiting decreased task compliance.

Impact of deep inspiration breath hold, surface-guided radiotherapy, and daily CBCT on the organs at risk in breast cancer radiotherapy

The goal of the study was to assess the impact of deep inspiration breath hold technique (DIBH), surface-guided radiotherapy (SGRT), and daily kilovoltage cone-beam computed tomography (kV-CBCT) on the dose to organs at risk (OAR) in left-sided breast cancer radiotherapy. Twenty-six consecutive left-sided breast cancer patients treated using Volumetric Intensity Modulated Arc Therapy (VMAT), DIBH, SGRT, and a hypofractionated regimen were retrospectively evaluated in this study. Dose parameters were extracted from dose-volume histograms (DVH). The Wilcoxon Matched Pairs test was used to test dose parameters obtained in free breathing (FB) and DIBH for statistical significance. Multivariable analysis of variance (ANOVA) and receiver operating characteristics (ROC) analysis were used to identify parameters and cut-off points associated with the reduction of the mean heart dose (MHD) by DIBH. Based on published models, the risk of cardiac and lung toxicity (pneumonitis) using SGRT or daily kV-CBCT was estimated and compared. DIBH substantially reduced the MHD (median, 43.6%; range, 4.2% to 75.1%; P < 0.00001). The risk of cardiac toxicity using SGRT increased by 1%, compared to 3.6% to 20.5% using daily kV-CBCT. No significant difference in the risk of radiation-induced pneumonitis using SGRT versus daily kV-CBCT was detected. The ANOVA revealed the relative increase of the left lung volume by DIBH as the only significant impact factor for the MHD. The ROC analysis of this parameter showed an area under the curve (AUC) of 0.89 (95%CI, 0.71 to 0.98; P < 0.0001). DIBH can substantially reduce the MHD in left-sided breast cancer patients treated with modern radiotherapy techniques and hypofractionation. Patient setup using SGRT compared to daily kV-CBCT may be the preferred option for many patients. In our patient cohort, the relative reduction of the left lung volume by DIBH can be used as a predictor to select patients who benefit from DIBH.

Abstract 4112524: Novel Contactless and AI-Based Method Can Determine Heart Rate and Cardiac-Induced Vibrations of Chest

Introduction: Seismocardiography (SCG) - measurements of cardiovascular-induced vibrations on the chest - has shown potential for providing clinical information for cardiac conditions. SCG is conventionally recorded by an accelerometer attached to a single point on chest. Recent research suggests multichannel SCG (mSCG) - measurements from multiple chest locations - can provide extra and more accurate clinical information. Current mSCG methods are limited to accelerometer arrays, laser Doppler vibrometry, and airborne ultrasound that are either costly, difficult for inexperienced users, or need bulky equipment, thereby impeding their use beyond research or clinical settings. Hypothesis: mSCG signals can be accurately estimated from tiny chest movements in chest videos recorded by ordinary cameras, e.g., those in smartphones. Methods: We enrolled 10 subjects (sbjs) with no history of CVDs (21.7 ± 1.7 years, 40% women). ECG and chest video of sbjs were recorded at rest for 15 sec during breath hold at the end of inhalation followed by another 15 sec recording during breath hold at the end of exhalation. We developed an AI-powered mobile app to record the chest videos and convert them to 0-30 Hz mSCG in right-to-left (RL) and head-to-foot (HF) directions (Fig 1a). Heart rate (HR) based on ECG RR interval and mSCG was measured and compared. Results: HR estimated from mSCG in both RL and HF directions had a good agreement with ECG-based HR using Bland-Altman analysis [RL: bias = 1.4 bpm, 95% CI = 5.6 bpm; HF: bias = 0.8 bpm, 95% CI = 6.2 bpm (Fig 1b)]. High-quality mSCG and ECG measurements were obtained for all sbjs. Conclusion: Clinically relevant information can be accurately extracted from chest videos using our novel, contactless, AI-based method. Given that the vast majority of Americans have access to a camera phone, future developments of this method may provide new means of remote and accessible cardiac monitoring.