Continuous positive airway pressure as an alternative to deep-inspiration breath holding for mediastinal lymphoma radiotherapy.

To directly quantify respiration-driven cerebrovascular resistance dynamics (CRD) using a gas-free MRI framework based on the internal-to-external artery carotid flow ratio (ratio_Q). Two independent datasets (n = 10 and n = 17) were used to evaluate repeatability and to compare breathing conditions. Real-time phase-contrast MRI (RT-PC) was performed at the C2-C3 level, and a dedicated in-house software was used to extract the respiratory-frequency components of internal and external carotid artery flow (Q_ICA and Q_ECA). The flow ratio (ratio_Q = Q_ICA/Q_ECA) was derived to attenuate cardiac-driven inflow effects. Its mean value (aver_ratio_Q) reflected baseline cerebrovascular resistance, while its pulsatility index (PI_ratio_Q = amplitude/mean) quantified respiration-driven CRD. In Dataset 1, ratio_Q showed excellent within-session repeatability for its mean value (ICC(3,1) = 0.96) and good repeatability for its pulsatility index (ICC(3,1) = 0.79). In Dataset 2, sustained deep breathing increased mean cerebrovascular resistance, evidenced by a decrease in aver_ratio_Q from 2.5 ± 0.9 to 1.7 ± 0.9. Specifically, aver_Q_ICA decreased by 30% (p < 0.001), whereas aver_Q_ECA showed no significant change (a 5% increase, p = 0.094). Respiration-driven CRD was enhanced during sustained deep breathing, with PI_ratio_Q increasing by ≈69% compared with free breathing (from 13.6 ± 5.0 to 23.0 ± 7.3, p < 0.001). This gas-free RT-PC approach using the ICA-to-ECA flow ratio provides a stable and reproducible index of respiration-driven CRD, enabling isolation of cerebrovascular resistance modulation from cardiac effects and supporting its potential role in the development of faster and more accessible CVR assessment strategies.

To compare regional ventilation assessed by non-contrast enhanced ventilation-weighted phase-resolved functional lung (PREFUL)MRI with parametric response mapping (PRM) and with pulmonary function test (PFT) parameters in patients with chronic obstructive pulmonary disease (COPD). This study was a retrospective analysis of a single-center subset of the prospective COPD cohort COSYCONET. PREFULMRI coronal sections were obtained during free breathing at 1.5 T using a spoiled gradient echo sequence. PRM was derived from paired low-dose inspiratory and expiratory CT scans. Matched coronal slices of PREFUL and PRM were co-registered. PREFUL ventilation defect percentage (PREFUL-VDP), as well as functional small airway disease (PRMfSAD), emphysema (PRMemph), and their combined metric (PRMfSAD+emph), were calculated. Global comparisons employed Spearman's correlation coefficient (r) and Wilcoxon signed-rank tests. Spatial agreement was assessed using spatial overlap and the Dice coefficient. Fifty-one patients (median age 65 [58-70]) were included in this study. PREFUL-VDP strongly correlated with combined PRMfSAD+emph (r = 0.86. p < 0.001) and with PFT parameters (PREFUL-VDP vs FEV1, r = -0.75, p < 0.001). Correlations between PREFUL-VDP with PRMfSAD and PRMemph separately were weaker (r = 0.57 and r = 0.82, p < 0.001 for both). In concordance, the highest spatial congruence was observed between PREFUL-VDP and PRMfSAD+emph (spatial overlap: 0.60 [0.55-0.66], Dice coefficient for defects: 0.53 [0.28-0.62]), indicating that PREFUL-VDP does not distinguish between small airway disease and emphysema. PREFUL-VDP correlates most strongly with the PRM measurement of emphysema and functional small airways disease combined and is a promising noninvasive, radiation-free tool for quantifying regional ventilation in COPD. QuestionHow does regional ventilation in COPD, measured by PREFUL MRI, correspond to CT-based PRM metrics? FindingsPREFUL MRI's VDP showed strong correlation and the highest spatial agreement with the combined CT PRM metric representing emphysema and functional small airways disease. Clinical relevancePREFUL MRI offers a non-invasive, radiation-free method for assessing regional ventilation in COPD. Although PREFUL cannot distinguish emphysema from small airways disease, its strong correlation with CT PRM highlights its value for disease characterization and functional monitoring.

Objective.Pencil beam scanning proton therapy is sensitive to respiratory motion, leading to potential dose inhomogeneities due to interplay effects. We developed and validated a predictive framework to assess interplay and motion robustness in lung and esophageal cancer patients treated under free-breathing conditions.Approach.A synthetic-breathing-based predictive model was implemented in the RayStation treatment planning system and validated against ana posterioriapproach using patient-specific respiratory traces and machine log files. Both were benchmarked against the Monte Carlo engine FRED. To demonstrate the methodology, the framework was applied to two clinical cases treated on the Mevion S250i system without rescanning. Dose accumulation incorporated respiratory phase, range (±3%), and setup (±5 mm) uncertainties.Main results.Excellent agreement was observed between TPS and FRED (<1% mean dose difference) and between predictive anda posteriorimodels (<2% across DVH metrics). Cumulative dose distributions for the primary CTV converged after five fractions, confirming robust delivery.Significance.This automated, clinically integrated framework enables pre-treatment prediction anda posteriorivalidation of interplay and motion robustness in Pencil beam scanning plans. Preliminary results support its clinical utility, especially for hypofractionation and targets with large motion (>2 cm). A larger cohort study is ongoing and will be reported separately.

Objectives: This study evaluated the utility of adaptive complex signal average (ACSA) diffusion-weighted imaging (DWI) specifically in breath-hold (BH) liver imaging, with a focus on signal intensity (SI) improvement, intrahepatic signal homogeneity, and apparent diffusion coefficient (ADC) behavior, and compared these findings with conventional non-ACSA DWI and free-breathing (FB) ACSA DWI. Methods: This retrospective study included 62 patients (mean age, 67.8 ± 13.6 years; 27 women) who underwent liver MRI with both FB and BH DWI on a 3-T system. Non-ACSA images were generated using conventional magnitude reconstruction, and ACSA images were reconstructed from identical raw data. SI, signal-to-noise ratio (SNR) and ADC were measured in the left lateral segment and right hepatic lobe. The signal intensity difference ratio (SIDR) between ACSA and non-ACSA, signal intensity ratio (SIR) and ADC ratio between right lobe and lateral segment were calculated. Results: In both FB and BH imaging, SI and SNR in both liver regions were significantly higher on ACSA DWI than on non-ACSA DWI (p < 0.01). ADC values were significantly lower with ACSA. SIDR was significantly higher in the left lateral segment (p < 0.01), indicating greater SI improvement in motion-prone regions. SIR and ADC ratios between lobes were significantly smaller with ACSA in both respiratory conditions (p < 0.01). FB-ACSA showed smaller SIR than BH-ACSA, while ADC ratios did not differ. Conclusions: ACSA DWI significantly improves SI, intrahepatic uniformity, and ADC reliability even under BH liver imaging. BH ACSA DWI may represent a potentially useful application complementary to FB ACSA DWI, supporting its consideration as a post-processing strategy for improving qualitative and quantitative liver DWI in future investigations.

Deformable Image Registration (DIR) is increasingly used in breast radiotherapy planning, but the impact of different parameter settings on clinical accuracy remains unclear. This study systematically evaluates how focus region selection and registration direction affect DIR performance, providing evidence-based recommendations for clinical implementation. We analyzed 73 patients with left-sided breast cancer who underwent both free breathing (FB) and deep inspiration breath-hold (DIBH) planning CT scans. Clinical target volume (CTV), heart, left anterior descending artery, and both lungs were retrospectively contoured by one radiation oncologist on both datasets. Deformable Image Registration was performed bidirectionally (FB↔DIBH) using four different approaches: no focus region, CTV-focused, heart-focused, and surgical clip-focused registration. Volume differences and Dice Similarity Index (DSI) were calculated to assess registration accuracy. Generalized estimating equations analyzed possible correlations. Focus region selection critically impacted DIR accuracy. CTV-focused registration achieved highest CTV overlap (DSI: 0.96 vs. 0.91 without focus, p < 0.005) but compromised other structures. Heart-focused registration optimized cardiac structure accuracy but reduced CTV precision. Registration direction showed minimal impact on volume differences but affected DSI values. Tidal volume significantly affected both CTV (p < 0.005) and heart DSI (p < 0.007), with opposite effects on each structure. Manual contour adjustment remained necessary in all cases regardless of parameter selection. DIR performance in breast radiotherapy is highly dependent on user-defined parameters, with no single configuration optimizing all structures simultaneously. Focus region selection creates a trade-off between local accuracy and global registration quality. Clinical implementation requires structure-specific parameter optimization and mandatory manual review. These findings establish practical limitations and benefits of hybrid DIR algorithms for breast radiotherapy workflows and highlight the continued necessity of expert oversight.

Fully self-gated dual-venc five-dimensional flow magnetic resonance imaging for simultaneous imaging of the cardiovascular and portal venous systems: A feasibility study.

Noninvasive detection of chronic pancreatitis (CP) is important for proper treatment and prevention of severe pain and pancreatic insufficiency. To evaluate if T1ρ MRF is significantly different in healthy volunteers and patients with CP. Prospective. Seventeen healthy volunteers (9 male, mean age: 38.0 ± 6.7 years) and 20 patients (12 male, mean age: 53.6 ± 6.4 years) who were clinically diagnosed with CP. 3 T, T1ρ MRF acquired during breath-hold (BH-MRF) and free breathing (FB-MRF), conventional T1/T2 mapping sequences. Mean T1/T2/T1ρ values in the whole pancreas were compared between diagnosed CP patients and controls. The Cambridge classification (CC) score was used to divide patients into mild-moderate (CC = 1-3) and severe (CC = 4) CP subgroups. T1, T2, and T1ρ relaxation maps were generated from both breath-hold (BH) and free-breathing (FB) MRF data. Mixed effects models were calculated for healthy control versus CP, and between mild-moderate and severe CP. Receiver operator characteristic (ROC) curves were analyzed and areas under the curves (AUCs) were calculated. A p-value < 0.05 was considered significant and multiple comparison corrections were applied. BH-MRF T1/T2/T1ρ values were significantly higher in the CP group (1327.3, 48.6, 49.1 ms) compared to healthy controls (821.6, 41.6, 39.5 ms) with AUCs of 0.994, 0.873, and 0.862, respectively. The MRF BH T1/T2/T1ρ values of mild-moderate CP (N = 7) and severe CP (N = 13) patients were also significantly higher compared to healthy controls. T1 was significantly higher in severe CP compared to mild-moderate CP (1497 and 1012.1 ms, respectively) with AUC = 0.945. FB MRF T1 relaxation times demonstrated good correlation with BH values (0.981), while T2 and T1ρ had moderate correlations (0.507 and 0.697, respectively). T1, T2, and T1ρ relaxation times have potential for noninvasively assessing CP. 2. Stage 2.

The purpose of this study is to enable 3D abdominal imaging and quantitative parameter mapping in free breathing conditions and simultaneously provide proton-density fat fraction (PDFF), water-specific and fat-specific T1 maps. A radially encoded MP2RAGE with alternated fat and water selective pulses was implemented and validated on a phantom containing gadolinium (Gd) and pork fat at different concentrations. Comparison with MR spectroscopy and imaging techniques of reference was performed invitro. Multiple experiments were carried out on healthy volunteers and individuals with a record of liver disease and benign bone marrow lesions to evaluate the method's repeatability, accuracy and potential for clinical application. Invitro water or fat specific T1 was in agreement with estimates provided by reference methods over a wide range of mixture ratios. PDFF was strongly correlated with spectroscopy (Pearson coefficient of 0.98) and other imaging techniques although underestimated due to the imperfect pulse selectivity profile. Images free of ghosting artefacts were acquired invivo on seven volunteers. The whole abdomen was imaged, as well as a large part of the spine (from T11 to L5). Parametric maps provided repeatable estimates in the liver, the bone marrow and the subcutaneous fat that were consistent with values reported in literature and other imaging techniques. The acquisition time could be halved without significantly affecting the quantitative values. Overall, high-contrast MP2RAGE abdominal images, water- and fat- specific T1 maps and PDFF maps were achieved in a single 3D acquisition under free breathing.

Balanced steady-state free-precession (bSSFP) cine imaging is the clinical standard for ventricular function assessment but requires multiple breath-holds, which can be challenging for pediatric and young adult patients. Deep learning (DL)-accelerated cine imaging offers the potential to reduce breath-hold burden, shorten scan time, and enable free-breathing acquisitions. To clinically evaluate a commercially available DL-accelerated cine bSSFP sequence (SonicDL) across multiple acceleration levels and breath-hold/free-breathing configurations, and to assess diagnostic image quality, ventricular volumetric accuracy, and scan time reductions. This retrospective study included 25 patients with pectus excavatum and 15 with cardiomyopathy who underwent conventional cine imaging with breath-hold duration of nine cardiac-cycle interval (9-RR) and SonicDL acquisitions at 4-RR breath-hold, 1-RR breath-hold, and 1-RR free breathing. Diagnostic image quality was independently scored by three expert readers using a 5-point scale. Automated DL-based segmentation provided biventricular volumetric indices, with phase-contrast flow serving as the physiological reference for stroke volume. Statistical analysis included repeated-measures ANOVA, paired tests, ICCs, and Bland-Altman analysis. SonicDL significantly reduced scan time 57% (4-RR breath-hold), 79% (1-RR breath-hold), and 87% (1-RR free breathing) compared with 9-RR breath-hold imaging. Diagnostic image quality was highest for 4-RR breath-hold (median 4.50), significantly exceeding other protocols (P<0.0001). Across all SonicDL protocols, volumetric indices showed small biases (<2mL/m2 for most parameters) with limits of agreement typically within ±6mL/m2. Stroke volumes showed close agreement with phase-contrast flow (biases 1-5mL/m2) across all protocols. In cardiomyopathy patients, diagnostic image quality was lower overall, but volumetric indices agreement remained within clinically acceptable ranges. SonicDL cine bSSFP imaging substantially reduces breath-hold burden and scan time while maintaining diagnostic image quality and close agreement with conventional cine and physiologic flow measurements. The 4-RR breath-hold protocol provided the most favorable balance of acceleration and fidelity, while free-breathing acquisitions offered a practical alternative for patients with limited breath-hold capacity.

CBCT-Guided Pencil Beam Scanning Proton Therapy for Moving Lung Tumours: PROMO Study- Standardised Workflow and Early Outcomes From a Consecutive Real-World Cohort.

Geometric and dosimetric impact of heart and cardiac substructure contouring variability in left-sided breast radiotherapy using VMAT-FFF: A FB versus DIBH analysis.

Advanced Imaging to Assess Airway Dynamics.

Evaluating the setup accuracy and workflow efficiency of tattooless surface-guided radiation therapy for breast cancer.

There is increasing interest in the application of proton beam therapy to left-sided breast cancer, due itspotential to reduce heart dose. However, state-of-the-art volumetric modulated arc therapy (VMAT) in conjunction with deep-inspiration breath hold (DIBH) and knowledge-based (KB) planning has demonstrated that low heart doses can be achieved in left-sided breast cancer with X-ray therapy. Fourteen left-sided breast cancer patients with comprehensive lymph node involvement previously treated at Royal North Shore Hospital (RNSH) were included in the project. All patients were scanned in DIBH and free-breathing (FB) during simulation. Photon plans were generated using the RNSH KB planning model on the DIBH scan. Intensity modulated proton therapy (IMPT) plans were generated on the FB datasets using a two-field approach with multifield optimisation (MFO).IMPT plans were designed to provide equivalent robust target coverage of the VMAT plans with the intention of comparing dose differences to organs at risk (OARs). Mean heart dose was significantly reduced (p<0.0001) for IMPT plans. However, mean heart doses were all below 2Gy for VMAT plans. Contralateral breast and ipsilateral lung were also significantly reduced with IMPT. Other OARs, including left anterior descending coronary artery, oesophagus, thyroid, spinal cord, humeral head and trachea did not show significant difference between modalities. Although statistically significant dose reductions for IMPT plans relative to VMAT were reported, the low mean heart doses observed with DIBH KB VMAT plans may limit clinical benefit when considering adverse cardiac events.

Background/Objectives: Radiation therapy for left-sided breast cancer exposes the heart and lungs to incidental radiation, increasing long-term risk of cardiopulmonary morbidity. This study evaluated the dosimetric impact of DIBH compared with free breathing (FB) and explored patient- and treatment-related predictors of benefit. Methods: We retrospectively analyzed 90 patients with left-sided breast cancer or chest wall irradiation planned under both FB and DIBH. Dosimetric parameters included mean heart dose (MHD), mean lung dose (MLD), heart V5, and lung V20. Univariable analyses assessed associations between dose reductions (Δ%) and clinical factors (age, BMI, fractionation, boost, nodal fields, and smoking). Multivariable regression identified independent predictors. Results: DIBH significantly reduced mean doses to the heart (FB 4.25 ± 1.47 Gy vs. DIBH 2.64 ± 1.28 Gy; Δ -1.60 Gy, p < 0.001, and Cohen's d = 2.46) and lung (FB 14.00 ± 3.45 Gy vs. DIBH 11.64 ± 3.32 Gy; Δ -2.36 Gy, p < 0.001, and Cohen's d = 2.73). Similarly, heart V5 (median Δ -10.5%, p < 0.001) and lung V20 (median Δ -5.5%, p < 0.001) were significantly improved. Higher BMI was independently associated with smaller relative reductions in MHD (-1.4% per unit, p < 0.001) and MLD (-0.31% per unit, p = 0.019). Hypofractionation was linked to greater MHD and MLD reductions (+8.9%, p = 0.007), (3.7%, p = 0.035), respectively. Supraclavicular field irradiation increased lung exposure, while internal mammary chain fields elevated both lung and heart doses. Age showed no significant influence. Conclusions: DIBH provides robust and consistent reductions in cardiac and pulmonary radiation doses during left-sided breast irradiation. The degree of sparing is modulated by BMI, fractionation, and nodal field inclusion.

To systematically evaluate and compare geometric setup errors and calculate optimal planning target volume (PTV) margins for patients with left-sided breast carcinoma treated with three-dimensional conformal radiotherapy (3D-CRT) using free-breathing (FB) versus deep inspiration breath-hold (DIBH) techniques. A retrospective analysis was conducted on 103 postoperative breast carcinoma patients (n = 47 in the FB group; n = 56 in the DIBH group). Daily setup verification was performed using paired kilovoltage (kV) orthogonal images, yielding 348 analysed fractions. Setup deviations were measured in anterior-posterior (AP), superior-inferior (SI), and right-left (RL) directions. PTV margins were derived using the Van Herk formula. In the FB group, systematic errors were 0.16 cm (AP), 0.17 cm (SI), and 0.17 cm (RL), with random errors of 0.28 cm, 0.37 cm, and 0.29 cm, respectively. In the DIBH group, systematic errors were 0.14 cm (AP), 0.16 cm (SI), and 0.16 cm (RL), with random errors of 0.25 cm, 0.29 cm, and 0.27 cm, respectively. DIBH significantly reduced setup errors in the SI direction (p = 1.1 x 10-5). Calculated PTV margins for DIBH were smaller, particularly in the SI axis (0.61 cm vs. 0.69 cm). DIBH significantly mitigates random setup errors in the longitudinal direction by stabilizing diaphragmatic motion, allowing for reduced PTV margins and improved sparing of organs at risk.

Continuous positive airway pressure (CPAP) has been demonstrated to provide favorable physiological changes for lung stereotactic ablative radiotherapy (SABR) delivery. This study investigates its specific utility for central lung tumors. Patients with central lung primary or metastatic tumors were recruited prospectively for SABR treatment with 60Gy in eight fractions. All patients were fitted with CPAP masks and assessed for tolerance of pressures up to 15cmH2O. 4D-CT planning imaging was acquired in standard free breathing and CPAP techniques. Forward-planned 3D conformal SABR plans were generated for both techniques for each patient. Outcomes for analysis included plan selection, planning target volume (PTV) displacement distance from primary central organ at risk (OAR), target volume size, target volume and OAR dosimetry, and qualitative analysis of CPAP tolerability. Twelve of 14 patients tolerated CPAP and underwent CT simulation and planning with standard and CPAP techniques. CPAP plans were preferred in 8 of the 12 patients. The mean PTV-OAR displacement was 5.8mm (SD=9.29) with CPAP compared to 4.1mm (SD=6.13) with free breathing (p=0.65). The mean maximum dose to the primary central OAR was 46.4Gy (SD=16.9) in the CPAP group and 51.3Gy (SD=15.8) in the standard group (p=0.22). CPAP is a safe and well-tolerated treatment adjunct in central lung SABR. Further investigation is required to determine whether CPAP can provide dosimetric advantages.

Functional ultrasound imaging (fUSI) is an emerging technology for assessing functional brain activity. To date, functional ultrasound without contrast agents has only been applied to human imaging during surgery with the skull removed or in neonates through a fontanel window. Here, we showcase a proof-of-concept study of contrast-free transcranial fUSI (tfUSI) through adult skulls. To achieve the high sensitivity and image quality required for tfUSI, we utilize several techniques including compound Barker coded excitation to boost signal-to-noise ratio, adaptive motion compensation and a head fixation device to minimize the effects of motion, and an eigen-based filtering approach to separate blood flow from tissue clutter. We assessed cerebrovascular reactivity induced by a breath hold by measuring cerebral blood volume with power Doppler imaging. We targeted the vasculature surrounding the midbrain in 13 healthy adult volunteers during a six minute task of alternating free breathing and breath holding periods. We showed that the power Doppler signal was correlated to the breath hold task ($\rho = 0.53 \pm 0.08$) and oxygen saturation ($\rho = 0.71 \pm 0.10$). Correlation coefficients were statistically significant for each subject (one-tailed $t$-test, $\alpha =0.01$). We also observed delayed vasodilation response in the power Doppler signal that reflected the expected delayed oxygen saturation drop from the breath hold. Delays to maximal signal were $47.69 \pm 23.7$ s for the first breath hold and $52.31 \pm 18.0$ s for the second breath hold. Our results demonstrate the utility of tfUSI for evaluating cerebrovascular reactivity and pave the way for further development to enable assessment of neural activation.

Optimizing Cardiac Dose Prediction in Left-Sided Breast Cancer Radiation Therapy: Clinical Strategies for Identifying Beneficiaries of the Deep Inspiration Breath-Hold Technique