Ultrasound in Medicine & Biology

BackgroundTumor progression is associated with alterations in tissue mechanical properties. Experimental studies in cancer mechanobiology suggest that increased viscosity of the tumor habitat can promote tumor growth, while malignant tumors often exhibit pronounced mechanical heterogeneity with coexisting soft and rigid regions that facilitate cell motility. Elastography enables noninvasive viscoelastic profiling of soft-tissue properties in vivo and may therefore detect tumor malignancy. PurposeTo investigate whether multiparametric external vibration-based ultrasound time-harmonic elastography (THE) can differentiate benign from malignant liver tumors and identify viscoelastic parameters associated with tumor malignancy. Materials and MethodsIn this prospective study conducted from January 2025 to March 2026, 94 patients with focal liver lesions underwent THE. Eighty-four patients were included in the final analysis (41 benign, 39 malignant; 45 women; age range 30-87 years). Liver and tumor stiffness (shear wave speed; SWS), viscosity (loss angle; {phi}), and spatial mechanical heterogeneity (spatial standard deviation, SWS-SD) were quantified. Diagnostic performance for differentiating benign and malignant tumors was assessed using the area under the receiver operating characteristic curve (AUC). ResultsTumor heterogeneity and surrounding habitat viscosity provided the most pronounced differentiation between malignant and benign lesions. Malignant tumors demonstrated higher SWS-SD (0.41{+/-}0.20 vs. 0.28{+/-}0.11 m/s) and increased {phi} (0.76{+/-}0.09 vs. 0.71{+/-}0.05 rad) with a combined discriminative power of AUC=0.72. These viscoelastic differences were more pronounced in larger tumors of [≥]2.5 cm2 area (SWS-SD: 0.47{+/-}0.19 vs. 0.32{+/-}0.11 m/s; {phi}: 0.78{+/-}0.10 vs 0.70{+/-}0.04 rad) yielding AUC=0.88 while excellent discriminative power of AUC=0.97 for [≥]6 cm2 tumor area. ConclusionElevated viscosity of the tumor habitat combined with increased tumor stiffness-heterogeneity measured by multiparametric THE can differentiate liver malignancies from benign liver lesions. THE may thus provide a rapid, cost-effective approach for viscoelastic profiling of liver tumors in clinical diagnostic imaging.

Objective:This study aims to compare the advantages and disadvantages of DLIR and adaptive statistical iterative reconstruction-V (ASIR-V) in thin-slice (2.5 mm) CT images of hepatic lesions characterized by high and low contrast. Additionally, the study seeks to determine the optimal DLIR strength for the evaluation of liver lesions. Methods:A retrospective analysis was performed on 90 patients who underwent abdominal contrast-enhanced CT scans. Group A comprised 48 patients with low-contrast lesions, while Group B included 42 patients with high-contrast lesions. The acquired images were reconstructed using post-processing DLIR at low (DLIR-L), medium (DLIR-M), and high (DLIR-H) strengths, all with a slice thickness of 2.5 mm (subgroups A1-A3, B1-B3). Furthermore, images were reconstructed with ASIR-V at 50% strength at slice thicknesses of 2.5 mm and 5 mm (subgroups A4/B4 and A5/B5, respectively). CT values and standard deviations (SD) of the liver and lesions were measured, and the corresponding signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The edge rise slope (ERS) was determined using ImageJ software by measuring CT values along a line from the liver parenchyma to the lesion. Objective metrics were compared using one-way ANOVA, with independent samples t-tests applied for inter-group differences. Subjective scoring, which encompassed noise level, diagnostic confidence, and lesion margin delineation, was conducted by two radiologists, with differences analyzed using the Kappa test. Results: Objective evaluation revealed a progressive decrease in lesion SD and a progressive increase in SNR and CNR from subgroups A1/B1 to A3/B3. The SD of Group A2 decreased by 57.4% compared to A4, while the SNR and CNR of A2 icreased by 19.3% and 24.6% compared to A4. Although subgroup B2 had a lower SNR than B5, the difference was not statistically significant. SNR and CNR in B2 increased by 24.1% and 11.9%, respectively, compared to B4. ERS gradually decreased from A1/B1 to A3/B3. ERS values in A2 and B2 increased by 27.0% and 39.4%, respectively, relative to A5 and B5. Although A3 had a lower ERS than A1 and A2, all DLIR subgroups exhibited higher ERS than A5; similar trends were observed in Group B. Subjective evaluation indicated good inter-reader agreement (Kappa > 0.61, p < 0.05). As DLIR strength increased, noise scores rose progressively in both groups. However, noise in A2 and B2 was lower than in A4/A5 and B4/B5. Diagnostic confidence and lesion margin delineation scores were highest in A2 and B2, while all subjective scores were lowest in A5 and B5. Discussion: Most prior studies evaluated the liver, vessels, or confirmed that image quality can be guaranteed at low doses. However, there are few studies on specific individual lesions. Therefore, this study aims to investigate specific individual lesions. The details and detection rate were analyzed separately to confirm the clinical acceptability of 2.5-mm DLIR image in different contrast lesions. Conclusion: For both high- and low-contrast hepatic lesions, DLIR provides superior image quality compared to ASIR-V, with the 2.5mm DLIR-M setting being optimal. DLIR-M reduces image noise, improves spatial resolution, and produces images more suitable for diagnostic purposes.

Contactless assessment of cardiopulmonary function remains an unmet need, with current approaches relying either on subjective clinical examination or on resource-intensive imaging. We evaluated a novel multipoint airborne ultrasound surface motion camera (SMC) designed to map thoracic vibration patterns without contact and to extract clinically relevant information through data-driven analysis. In a prospective observational study, clinically characterised participants underwent short-duration acquisitions during natural breathing and externally induced oscillations. The resulting signals were transformed into spatially and frequency-resolved maps and analysed using machine learning models to discriminate healthy individuals from patients with respiratory or cardiac disease. The approach proved feasible in a clinical setting and achieved excellent discrimination between healthy individuals and respiratory patients (area under the receiver operating characteristic curve (AUC) 0.90 {+/-} 0.07), including in patients with subtle abnormalities not detected by pulmonary function testing. Discrimination between healthy individuals and cardiac patients ranged from acceptable to excellent (AUC 0.76-0.90 depending on subgroup), with the highest performance observed in aortic stenosis. Model interpretability analyses revealed spatial and spectral patterns consistent with the known physiological organisation of lung mechanics and cardiac auscultation areas, supporting a structure-function relationship between recorded signals and underlying processes. These findings indicate that thoracic vibration transmission encodes spatially and spectrally organised information that can be captured without contact and exploited through explainable data-driven modelling. While the results require confirmation in larger populations, this approach may represent an operator-independent, low-burden extension of bedside assessment, with potential applications in early detection, triage, and monitoring of cardiopulmonary disease.

ObjectivePulsed field ablation (PFA) relies on irreversible electroporation to create nonthermal cardiac lesions, yet real-time indicators of electroporation progression and validated lethal electric field thresholds remain limited. This study aimed to develop a bioimpedance-based metric for real-time monitoring of cardiac electroporation, evaluate the impact of myocardial anisotropy under electroporation conditions, and derive waveform-specific lethal electric field thresholds. IntroductionCurrent PFA procedures lack direct intraoperative feedback on lesion formation, and uncertainty remains regarding the role of myocardial fiber orientation in shaping electric field distributions. Because electroporation dynamically alters tissue electrical properties, monitoring these changes during treatment may improve prediction of ablation outcomes. MethodsPFA was delivered to fresh ex vivo porcine ventricular tissue using clinically relevant and energy-matched waveforms with pulse widths from 1 to 100 {micro}s. Inter-burst broadband electrical impedance spectroscopy was performed using a low-voltage diagnostic waveform to quantify burst-resolved impedance changes. Lesions were visualized using metabolic staining, then finite element models incorporating nonlinear electroporation-dependent conductivity were used to compare anisotropic and homogenized electric field distributions. Lethal electric field thresholds were estimated by fitting simulated contours to measured lesion areas and validated using uniform electric fields generated by a parallel electrode array. ResultsAcross all waveforms, impedance measurements showed a rapid initial decrease followed by stabilization, indicating early electroporation saturation. Burst-to-burst percent change in impedance slope provided a consistent, waveform-agnostic metric of electroporation progression. Lesion morphology was not systematically influenced by fiber orientation, and modeling demonstrated that electroporation-induced conductivity increases homogenized tissue anisotropy. Lethal electric field thresholds increased with decreasing pulse width, ranging from 517 {+/-} 46 V/cm (100 {micro}s) to 1405 {+/-} 55 V/cm (1 {micro}s), and were validated under uniform field conditions. ConclusionBioimpedance-assisted monitoring enables real-time assessment of cardiac electroporation, while electroporation-induced homogenization supports simplified modeling and standardized PFA treatment design.

Handheld ultrasound devices have revolutionized point-of-care diagnostics, but their effectiveness remains limited by operator dependency and the need for specialized training. This paper presents an intelligent guidance and diagnostic assistance system for the handheld wireless ultrasound device, enabling automated carotid artery and thyroid examinations through handheld operation. Drawing inspiration from the Actor-Critic framework, we implement a simulation-based reinforcement learning approach for real-time probe navigation toward standard anatomical views. The system integrates YOLOv8n-based detection networks for carotid plaque and thyroid nodule identification, achieving real-time inference at 30 frames per second. Furthermore, we propose a hybrid measurement approach combining UNet segmentation with the Snake algorithm for precise biometric quantification, including carotid intima-media thickness (IMT), lumen diameter, and lesion dimensions. Experimental validation on clinical datasets demonstrates that the proposed system achieves 91.2% accuracy in standard plane acquisition, 87.5% mean average precision (mAP) for plaque detection, and 89.3% mAP for nodule identification. Measurement results show excellent agreement with expert sonographers, with IMT measurements exhibiting a mean absolute difference of 0.08 mm. These findings demonstrate the feasibility of intelligent handheld ultrasound examination, significantly reducing operator dependency while maintaining diagnostic accuracy comparable to experienced clinicians.

PurposeImaging of the central lymphatic system enables characterization of patient-specific lymphatic anatomy and accurate localization of leaks. Advancements in CT technology, particularly spectral CT, can enhance CT lymphangiography (CTL) with improved visualization and quantification. This study aimed to assess the feasibility of spectral CTL in both static and dynamic scans. Materials and Methods50% diluted iodinated contrast was injected into the bilateral superficial inguinal lymph nodes of a pig. The pig was scanned with a dual-layer spectral CT every 60 seconds for 10 minutes. To optimize contrast and visualize peristalsis, a second animal was injected with 25% and 10% diluted contrast and scanned dynamically 4 and 6.25 minutes after contrast injection. Conventional images and iodine maps were reconstructed to calculate the contrast-to-noise ratio (CNR). Additionally, the iodine density was measured adjacent to the lymphovenous junction to show fluctuations from peristalsis and contrast washout. ResultsIodine maps, compared to conventional images, separated the contrast-filled central lymphatic system from surrounding soft tissue and increased CNR to 895 compared to 43 with conventional images. 25% diluted contrast provided the best balance between visualization and quantification of the central lymphatic system, showing high and low iodine density regions corresponding to peristalsis. Iodine density peaked at 15.4 {+/-} 0.6 mg/mL and decreased to 2.0 {+/-} 0.1 mg/mL at 10.5 minutes. ConclusionSpectral CTL not only improves visualization of the central lymphatic system compared to CTL but also provides quantitative information for physiological characterization of lymphatic disease that can enhance current subjective assessment. Research highlights- Iodine maps from spectral CT lymphangiography separated contrast-filled lymphatic structures from surrounding soft tissue and provided better contrast-to-noise compared to conventional images. - Spectral CT lymphangiography enabled quantification of contrast in the central lymphatic system that demonstrated contrast washout and may be utilized for physiological characterization of disease. - Dynamic spectral CT imaging of the lymphatic system visually showed peristalsis in the thoracic duct and was further reflected in quantitative iodine density measurements.

Background: Quantitative lipid assessment is central to identifying rupture-prone coronary plaques and represents a therapeutic target for lipid-lowering therapy. Near-infrared spectroscopy (NIRS)-derived lipid core burden index (LCBI) is well validated and widely used for detecting lipid-rich lesions. Optical frequency domain imaging (OFDI) is increasingly adopted for guiding percutaneous coronary intervention (PCI) due to its high-resolution structural imaging capabilities. Depolarization-sensitive OFDI (depOFDI) provides intrinsic lipid contrast and may enable combined structural and compositional plaque characterization within a single OFDI-based platform. Objective: To define an OFDI-derived lipid metric and evaluate its agreement with NIRS-derived LCBI. Methods: Thirty-three patients underwent both polarization-sensitive OFDI and NIRS-intravascular ultrasound imaging during PCI. After exclusion of 4 datasets, 29 co-registered pullbacks were analyzed. A signal-to-noise-corrected depolarization metric was used to identify lipid-rich regions and generate depOFDI chemograms. maxLCBI4mm value and location, as well as total LCBI, were computed and compared with NIRS. Results: depOFDI demonstrated strong agreement with NIRS, showing high correlation for maxLCBI4mm (r^2 = 0.862) and total LCBI (r^2 = 0.867), along with strong spatial concordance for the location of the maxLCBI4mm (r^2 = 0.900). Bland-Altman analysis of LCBI4mm showed minimal bias (10.7) with 95% limits of agreement of [81.4 to 102.8]. Conclusions: depOFDI enables accurate quantification of lipid burden alongside the high-resolution structural information inherently provided by OFDI. Because depolarization metrics can be derived from polarization-diverse detection available in many commercial OFDI systems, this approach provides a practical pathway toward comprehensive plaque characterization within existing PCI workflows, without the need for additional imaging modalities.

Background: Before transcatheter aortic valve replacement (TAVR), patients with severe aortic valve stenosis are at an increased risk of developing fluid volume overload and heart failure, which is associated with subsequent adverse outcomes after TAVR. Purpose: To quantify fluid volume status as whole-body fast-exchange extracellular volume (FE-ECV) in patients undergoing TAVR compared to healthy reference values using photon-counting CT (PCCT). Methods: Consecutive patients referred for TAVR and healthy living kidney donor candidates, respectively, underwent PCCT including the pelvis. FE-ECV (mL) was quantified using venous hematocrit, injected iodinated contrast concentration and volume, and blood iodine concentration and urinary bladder excreted iodine mass quantified in iodine map regions of interest from the inferior vena cava and covering the urinary bladder, acquired at one time point 6-10 minutes after intravenous iodinated contrast administration. Results: The study included 156 subjects (healthy: n=51, age 47{+/-}9 years, 55% female; TAVR: n=105, age 78{+/-}6 years, 39% female). In healthy subjects, FE-ECV was 160{+/-}22 mL/kg lean body mass (LBM), 95% limits 116-204 mL/kg LBM, and was independent of age, sex, contrast agent type, and scan delay time after contrast injection (p>0.66 for all). Compared to healthy subjects, FE-ECV in patients referred for TAVR was higher (174{+/-}34 mL/kg LBM, p=0.01), with 19 patients (18%) exceeding the normal range. Conclusion: One in five patients referred for TAVR demonstrated increased FE-ECV, revealing a substantial prevalence of fluid overload detectable by single-time point late-phase PCCT iodine mapping.

BackgroundIntracranial steno-occlusive disease (SOD) assessment benefits from hemodynamic imaging, but comprehensive evaluation often relies on contrast- or radiation-based techniques. Arterial spin labeling (ASL) provides a non-invasive alternative for quantifying tissue-level perfusion and cerebrovascular reactivity, yet does not capture upstream arterial flow dynamics. As a result, non-invasive assessment of macrovascular hemodynamics for SOD remains limited. This study evaluates whether quantitative 4D-MRA provides complementary arterial information beyond established ASL-derived metrics. MethodsTwelve SOD patients (7 women; age 42.3{+/-}25.8 years) underwent multi-delay ASL and 4D-MRA before and after acetazolamide. Cerebrovascular reactivity (CVR), arterial transit time (ATT), macrovascular ATT (mATT), and labeled blood volume (LBV) were quantified. Associations and vasodilatory responses were assessed using linear mixed-effects models. ResultsAt baseline, mATT correlated with ATT ({beta}=0.66{+/-}0.08, p<0.001). Both decreased following acetazolamide (mATT: 1.07{+/-}0.03s to 1.01{+/-}0.03s, p=0.029; ATT: 1.63{+/-}0.07s to 1.40{+/-}0.07s, p<0.001). However, changes in mATT and ATT were not associated with CVR. In contrast, CVR was positively associated with {Delta}LBV ({beta}=8.84, SE=2.43, p=0.01). Case analyses further demonstrated artery-level delayed inflow and vascular steal. ConclusionQuantitative 4D-MRA provides complementary macrovascular information to ASL in SOD. {Delta}LBV more consistently reflects cerebrovascular reactivity than transit-based metrics and is sensitive to artery-level delayed inflow and vascular steal. The local Medical Ethical Review Committee declared that the Medical Research Involving Human Subjects Act (WMO) did not apply (internal trial nr. 21-406).

Objective: Coronary artery calcification (CAC) assessment for cardiovascular risk stratification is traditionally achieved using ECG-gated computed tomography (CT). Automated deep-learning (DL) algorithms may streamline opportunistic CAC detection and scoring, particularly on non-gated CT scans. This study evaluated the performance of a fully automated DL-based CAC scoring algorithm ("DL-CAC") against expert human scoring. Methods: The algorithm was trained on 1,260 chest CT scans from multiple databases to automatically identify coronary calcium, calculate Agatston scores, and assign a cardiovascular disease (CVD) risk classification. Performance was assessed on a holdout dataset (n=500) comprising ECG-gated calcium scoring CT scans and lung cancer screening non-gated chest CTs as well as in an external, independent CT dataset (n=129) from liver transplant candidates. Agreement with expert scoring was assessed using intraclass correlation coefficient (ICC) for Agatston scores and Cohen's {kappa} for CVD risk classification. Results: The algorithm demonstrated high agreement with expert scoring in the pooled calcium scoring and lung cancer screening cohorts, with an ICC of 0.947 for Agatston scores and {kappa} of 0.936 for CVD risk classification. For liver transplant candidates, the algorithm exhibited substantial agreement with expert scoring of non-gated CT scans ({kappa}=0.79) and a sensitivity of 90.4% and specificity of 96.4% in high-risk cases. Conclusion: These findings suggest that DL-based CAC scoring on non-gated CT scans may be a feasible alternative to traditional methods and could support opportunistic cardiovascular risk assessment in routine imaging. Further validation is warranted to assess clinical integration in broader practice settings.

Myocaridum biomechanics are a biomarker for multiple cardiac pathologies. However the rapid and complex heart motion hampers accurate measurements of the tissue stiffness. Current in vivo methods for the evaluation of myocardium mechanical health are either highly invasive or can only provide with a global surrogate of heart function as they suffer from poor spatiotemporal resolution. We propose a new in vivo technique, transient magnetic resonance elastography (tMRE), to assess the dynamic cardiac biomechanics. tMRE is able to quantify local shear wave speed as a proxy for myocardial stiffness at user-defined times within the cardiac cycle. We report proof-of-concept results where we probe the septum of 4 different healthy rat specimens at 3 physiologically distinct cardiac phases. We provide with apparent speed measurements for early systole, mid-late systole and early diastole that match the expected values from the cardiac cycle physiological mechanics. We correct for non-negligible geometrical biases using literature results and report true stiffness values where possible. Finally, we validate tMRE in phantom experiments.

Background. Carotid webs (CaWs) are shelf-like protrusions in carotid bifurcation recognized as a potential cause of ischemic stroke. However, their impact on wall-based hemodynamic metrics (TAWSS, OSI, RRT) in distinguishing from normal bifurcations remains unclear. Methods. Carotid geometries were reconstructed from CT angiography in patients with CaWs, classified as symptomatic (with ischemic stroke) or asymptomatic (incidentally detected), and controls with normal bifurcations. Influence of three blood viscosity models (Newtonian, Carreau-Yasuda, Casson) was evaluated. Metrics were quantified using a Gaussian-weighted spatial averaging method and compared between groups. Results. CFD simulations were performed in 22 CaW cases (16 symptomatic, 6 asymptomatic) and 6 normal bifurcations. Simulations predicted recirculation corresponding to delayed contrast clearance on DSA. Viscosity models had minimal influence on flow patterns (<2% differences). CaWs showed greater inter-patient variability than normal bifurcations, but overlap remained (e.g., TAWSS 3.39 (2.72-8.96) vs 4.18 (3.09-4.56) Pa, p = 0.858). Symptomatic CaWs showed lower TAWSS and higher OSI and RRT than asymptomatic CaWs (TAWSS 3.39 vs 6.63 Pa), although did not reach statistical significance (p > 0.25). Conclusion. Symptomatic CaWs show lower shear stress and stronger oscillations than asymptomatic CaWs. However, wall-based hemodynamic metrics alone may not distinguish CaWs from normal carotid geometries.

Background and PurposeNeurointerventional outcomes depend on clot composition and may be influenced by clot contraction. Thus, a priori identification of clot composition and contraction could inform procedural strategies and improve outcomes. The goal of our work is to conduct an in vitro test to determine whether MRI can reliably predict both clot composition and contractile state. Materials and MethodsTo this end, we prepared blood clots spanning clinically observed compositions (0-80% red blood cells (RBCs)) in both contracted and uncontracted states. Contraction was controlled by coagulating blood with or without thrombin. We imaged these clots using quantitative, clinical, and investigational MRI sequences. Using these data, we then determined whether MRI signal intensities, quantitative parameters, and radiomic features capturing intensity and texture patterns can (i) predict clot hematocrit and (ii) classify clots by composition (RBC-rich vs. fibrin-rich) and contraction state. ResultsQuantitative MRI parameters (T1, T2, ADC) decreased with increasing hematocrit (R2 = 0.56-0.85, p < 0.001), while signal intensities from clinical sequences showed weaker correlations (R2 = 0.46-0.62, p < 0.001). Radiomic models predicted hematocrit with performance comparable to MRI parameters. When applied to classification, radiomic features accurately discriminated RBC-versus fibrin-rich clots, with AUCs exceeding 0.90 across nearly all sequences. In contrast, classification of contraction state showed greater variability in AUCs across sequences but remained high for quantitative T1 and T2 values (AUCs up to 0.88). Trends were consistent across clots coagulated with and without thrombin. Pooling features across sequences did not outperform the best individual sequence for either regression or classification. ConclusionsWe demonstrate that MRI-based radiomic analysis quantitatively characterizes clot composition and contraction in vitro. These findings support the feasibility of using MRI for pre-interventional clot phenotyping, with potential to inform thrombolytic and mechanical thrombectomy strategies. Thus, in vivo studies validating these results are warranted.

Adult hippocampal neurogenesis plays a central role in learning, memory formation, and adaptive neural plasticity, making it an attractive target for noninvasive neuromodulation strategies. Low-intensity focused ultrasound (LIFU) has emerged as a promising modality for modulating brain function, yet its effects on adult neurogenesis and the role of stimulation frequency remain incompletely understood. In this study, we evaluated whether transcranial LIFU applied to the dentate gyrus influences neurogenic and cognitive outcomes in a frequency-dependent manner. Adult rats received twice-weekly ultrasound stimulation for four weeks at 0.5, 1, or 5 MHz. Neurogenesis was assessed through BrdU incorporation and neuronal differentiation by BrdU/NeuN co-labeling, while expression of neurogenesis-associated markers (BDNF, FGF-2, and Sox-2) was quantified using qRT-PCR. Behavioral effects were examined using the novel object recognition task. Among the tested conditions, 0.5 MHz stimulation produced the most pronounced neurogenic response, with increased cellular proliferation in the dentate gyrus, elevated expression of neurogenic markers, and improved recognition memory relative to sham-treated animals. Higher stimulation frequencies yielded comparatively weaker effects. These findings identify stimulation frequency as a critical determinant of LIFU-driven neuroplastic responses and support the potential of focused ultrasound as a noninvasive approach for promoting hippocampal regeneration and functional recovery.

Mitochondrial diseases are a diverse group of inherited neuromuscular disorders leading to progressive disability and early mortality. Mitochondrial myopathy is a common feature of mitochondrial disorders, affecting most patients. Assessment of disease progression and treatment efficacy in mitochondrial disease trials has often relied on muscle biopsies, however, these are increasingly considered unfavourable by patients. Imaging biomarkers of disease could reduce the patient burden, enabling non-invasive longitudinal monitoring of molecular information. Photoacoustic imaging combines the molecular sensitivity of light absorption with the deep tissue imaging capabilities of ultrasound, enabling a safe and fast imaging technique. Tuning the wavelength of light allows for the detection of molecular constituents such as oxy- and deoxy-haemoglobin, lipids, and water. These signatures may reflect underlying pathophysiological alterations and serve as valuable indicators of disease state and progression. We conducted an exploratory study of a photoacoustic imaging dataset in patients with mitochondrial myopathy due to the m.3243A>G mt-tRNALeu mutation and compared to healthy volunteers. We generated photoacoustic measurements at wavelengths in the near infrared, comparing absolute values and ratios derived in the bicep muscle. Confounding factors such as skin colour and sex were considered, and we ensured that these parameters were matched in healthy volunteers and patients. We identified significant differences between patients and controls, revealing changes in ratios between water and total haemoglobin, lipid and total haemoglobin, and lipid and water content. This study highlights the promise of photoacoustic imaging as a novel imaging biomarker in mitochondrial myopathies, paving the way for larger scale studies.

BackgroundExisting neuromonitoring tools lack the capability for continuous, intraoperative assessment of cerebral oxygenation and tissue viability during endovascular thrombectomy (EVT) of large vessel occlusion stroke. Time-domain near-infrared spectroscopy (TD-NIRS), an advanced non-invasive optical technique, may overcome this challenge. However, no study has yet investigated TD-NIRS feasibility as an intraoperative neuromonitoring tool during EVT and its capability in predicting post-recanalization infarct. MethodsIn this prospective observational study, eleven patients with middle cerebral artery or internal carotid artery occlusion were monitored during EVT using TD-NIRS. Absolute concentrations of oxyhemoglobin ([HbO2]), deoxyhemoglobin ([HHb]), total hemoglobin ([tHb]), and tissue oxygen saturation (StO2) on both hemispheres was derived using a scaled Monte Carlo approach. Patients were dichotomized into post-EVT cortical infarct and no infarct, and the {Delta}[HbO2]/[HHb] pre- vs post-recanalization was assessed. ResultsSignificant differences were observed in pre- vs post-recanalization [HbO2] (p=0.0068), [HHb] (p=0.042), and StO2 (p=0.0020) on the affected hemisphere. The {Delta}[HbO2]/[HHb] significantly differed between patients with and without post-EVT infarct (p=0.0043). Logistic regression (p=0.0041) and ROC (AUC=0.82) determined that {Delta}[HbO2]/[HHb] reliably predicts post-EVT cortical infarct. ConclusionsThese results suggest TD-NIRS as a novel, adjunctive intraoperative neuromonitoring tool during EVT, with potential to predict post-EVT cortical infarct, guiding clinical management before/after thrombectomy. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/26345790v1_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@106e02eorg.highwire.dtl.DTLVardef@681070org.highwire.dtl.DTLVardef@f3387org.highwire.dtl.DTLVardef@2df_HPS_FORMAT_FIGEXP M_FIG C_FIG

Background: Cardiovascular magnetic resonance (CMR) quantification of the left ventricular (LV) volumes and ejection fraction (EF) typically involves manual segmentation of many short axis (SAx) and long axis (LAx) slices of the left ventricle. The scan time and the number of breath holds is proportional to the number of slices. We aimed to evaluate a geometric model of the left ventricle that could enable planimetry from a reduced number of slices. We sought to determine whether acceptable accuracy was retained for evaluating the End Diastolic Volume (EDV), End Systolic Volume (ESV), Stroke Volume (SV), and EF to provide a rapid and reliable clinical alternative. Methods: A cohort of 342 patients, median age: 54 (40 - 65) years, with full-stack CMR examinations was used. Nine geometrical combinations were evaluated: 3, 4 or 5 short axis slices and one of three LAx orientations (2-chamber, 3-chamber or 4-chamber) by retrospectively decimating the full-stack acquisition. LV volumes were calculated as a sum of trapezoidal approximations for apical and mid-cavity slices and a generalized prismoidal model at the base. The accuracy of the volume calculations was quantified against the full-stack reference for the EDV, ESV, SV, and EF using concordance correlation coefficient (CCC), two-way repeated measures ANOVA, pairwise tests, and Bayes factor log10(BF10) analysis. Results: The choice of the long axis (LAx) view was the most influential driver of accuracy (g2 = 0.104, for EDV), approximately 50 times more impactful than the number of SAx slices (g2 = 0.002, for EDV). Volumes calculated using the combination of 2-chamber LAx view and 5 SAx slices had the highest concordance with the full stack (CCC>0.90). While the estimated absolute volumes displayed a systematic negative bias, EF and SV remained highly robust due to bias cancellation. For a 2ch + 5 SAx protocol, EF bias was just 0.83% (LoA: -6.18 to 7.84%), with a minimum detectable change (MDC) of 7.01%, compared to 8.7% reported for expert human readers, suggesting strong concordance. Bayesian paired-samples t-tests yielded log10(BF10) = 6.42 in favor of 5 SAx over 3 SAx, constituting decisive evidence on the Jeffreys scale. The bias and limits of agreement (LoA) for stroke volume and ejection fraction were found to be lower than scan-rescan reproducibility in literature. Conclusion: This reduced-slice geometric model allows for reduced number of breath holds compared to a conventional full-stack CMR acquisition and provides an acceptable accuracy with bias less than scan-rescan variability.

Background: The specific 3D morphological substrates distinguishing the newly defined massive and torrential functional tricuspid regurgitation (FTR) phenotypes from standard severe disease remain under-characterized. Objectives: This study investigates the 3D geometric changes of the tricuspid valve (TV) apparatus across the spectrum of FTR, specifically focusing on the structural definition of massive and torrential grades. Methods: Three-dimensional (3D) transesophageal echocardiography (TEE) was performed in 322 patients with FTR secondary to left-sided heart disease. Patients were stratified into mild-moderate (n=166), severe (n=82), and massive-torrential (n=74) groups. TV geometry, including annular dimensions, leaflet tethering, and subvalvular apparatus, was quantified using 3D modeling software. Results: Patients with massive-torrential TR were characterized by advanced age, female predominance, and atrial fibrillation (75%). 3D analysis demonstrated that massive-torrential TR represents a distinct phenotype defined by extreme annular circularization (ellipticity index 1.0) and planar flattening (P < 0.001). Furthermore, these patients exhibited a critical leaflet-annulus uncoupling, where compensatory leaflet growth (relative length < 80%) failed to match the massive annular dilation. Consequently, the regurgitant orifice in massive-torrential grades appeared highly complex, frequently manifesting as multiple irregular orifices. Conclusions: Massive and torrential FTR are characterized by a unique geometric profile involving extreme annular circularization, severe leaflet tethering, and leaflet-annulus uncoupling. These morphological insights suggest that conventional repair strategies may be insufficient for these advanced phenotypes, highlighting the necessity for pre-procedural 3D TEE to guide device selection.

IntroductionArteries, like other soft tissues, exhibit viscoelastic mechanical behavior, meaning their response to stress and strain is time dependent. This implies that the way arteries deform depends not only on the amount of force applied but also on the rate at which the force is applied. This study investigates the effects of different loading rates on the mechanical behavior of human femoropopliteal arteries (FPAs) to understand their rate-dependent characteristics. MethodsHuman FPA specimens were collected from 14 donors, including 7 males and 7 females, aged 45-55 years. A 10x10 mm segment was isolated, mounted onto a biaxial testing device, and subjected to varying loading rates (10 to 50 mN/s). Mechanical responses were recorded, and stress-stretch curves were analyzed. Statistical analyses, including mixed-design ANOVA, assessed the impact of sex and loading rates on tissue stiffness. ResultsResults indicated significant loading-rate dependency, particularly in the circumferential direction. Stretch values decreased with increasing loading rates, more prominently in the circumferential than in the longitudinal direction (p-value<0.01). Statistical analyses revealed no significant interaction between sex and loading rate, though male arteries exhibited slightly higher compliance than female arteries. DiscussionThe findings demonstrate that the mechanical response of FPAs is highly dependent on the loading rate, with more pronounced effects observed in the circumferential direction. At higher loading rates, the human FPAs demonstrated a stiffer response in the circumferential direction. DedicationWe dedicate this work to the memory of our late student, Ali Zolfaghari Sichani, who passed away tragically during his doctoral studies. Ali performed the majority of the experiments and the initial analysis reported in this paper. His passion, dedication, and hard work were the foundation of this research, and he is deeply missed.

ObjectivesTo characterize longitudinal age-related changes in abdominal organ volumes using CT volumetry and to model nonlinear trajectories across multiple organs. Materials & MethodsThis retrospective single-center study included adults who underwent whole-body screening low-dose CT between 2006 and 2017. Subjects with at least eight examinations during a follow-up period of at least 78 months were included. After applying exclusion criteria, 700 participants with 6,739 CT series were analyzed. Non-contrast CT images were processed using automated organ segmentation, and volumes of the liver, pancreas, spleen, and kidneys were quantified. Longitudinal changes were modeled using generalized additive mixed models with sex-specific smooth functions of age and subject-level random effects. Age-dependent rates of change were estimated from model derivatives. ResultsA total of 700 participants (mean age, 56.9 {+/-} 9.8 years, 29.6% women) were evaluated. Liver, pancreas, and kidney volumes showed mild increases or plateaued at approximately 40-60 years of age, depending on the organ, and were followed by gradual declines with advancing age, whereas splenic volume showed a progressive decrease across the age range. These patterns showed nonlinear age dependence. The transition from positive to negative change rates tended to occur earlier in women than in men for several organs, particularly the liver and kidneys. ConclusionLongitudinal CT analysis demonstrated nonlinear age-related changes in abdominal organ volumes, with organ-specific trajectories and sex-related differences in the timing and magnitude of volume changes. QuestionHow do abdominal organ volumes change longitudinally with age, and can their trajectories be characterized for each organ? FindingsLongitudinal CT analysis demonstrated nonlinear, organ-specific volume trajectories, with transitions from stability to decline around 40-60 years and earlier transitions in women than men. Clinical RelevanceLongitudinal reference patterns of abdominal organ volumes on CT improve the interpretation of age-related changes and support more accurate differentiation between physiological variation and disease-related volume alterations.