Quantitative Perfusion Research Articles

Effects of foam rolling on vastus intermedius and lateralis microvascular blood flow

IntroductionFoam Rolling (FR) as a technique of self-massage has become a widely used intervention in clinical and sports practice. It is assumed that FR leads to an increased intramuscular microvascular blood flow (MBF), and therefore is commonly recommended as a warm-up or regeneration method. However, no data validate the effects of FR on MBF. This study aimed to assess whether FR increases intramuscular MBF using contrast-enhanced ultrasound (CEUS). MethodsTen healthy athletes performed a standardized FR intervention applied to the lateral thigh (3 sets: 45 s FR, 20 s rest). Intramuscular perfusion was determined by CEUS under resting conditions (t0), immediately (t1), and 30 min (t2) after the intervention. Peak enhancement (PE), wash-in rate (WiR), and wash-in perfusion index (WiPI) were evaluated as quantitative perfusion parameters in vastus lateralis (VL) and intermedius (VI) muscle separately via regions of interest mapping. ResultsImmediately after the intervention (t1), perfusion parameters showed a non-significant decrease in VL (p = 0.3; PE: -32.1%, WiPI: -29.6%, WiR: -50.4%) and VI (p = 0.4; PE: -10.3%, WiPI: -6.4%, WiR: -35.6%). A non-significant decrease was found at t2 in VL (p = 0.2; PE: -34%, WiPI -33.9%, WiR -61.2%) and VI (p = 0.2; PE -17.6%, WiPI -13.8%, WiR -43.2%). ConclusionsThe common assumption of intramuscular MBF improvement due to FR could not be confirmed for up to 30 min after the intervention. If an increase in intramuscular metabolism or MBF is intended, we recommend that alternative methods (i.e., traditional warm-up) should be preferred.

Dynamic Perfusion Representation and Aggregation Network for Nodule Segmentation using Contrast-enhanced US.

Dynamic contrast-enhanced ultrasound (CEUS) imaging has been widely applied in lesion detection and characterization, due to its offered real-time observation of microvascular perfusion. Accurate lesion segmentation is of great importance to the quantitative and qualitative perfusion analysis. In this paper, we propose a novel dynamic perfusion representation and aggregation network (DpRAN) for the automatic segmentation of lesions using dynamic CEUS imaging. The core challenge of this work lies in enhancement dynamics modeling of various perfusion areas. Specifically, we divide enhancement features into the two scales: short-range enhancement patterns and long-range evolution tendency. To effectively represent real-time enhancement characteristics and aggregate them in a global view, we introduce the perfusion excitation (PE) gate and cross-attention temporal aggregation (CTA) module, respectively. Different from the common temporal fusion methods, we also introduce an uncertainty estimation strategy to assist the model to locate the critical enhancement point first, in which a relatively distinguished enhancement pattern is displayed. The segmentation performance of our DpRAN method is validated on our collected CEUS datasets of thyroid nodules. We obtain the mean dice coefficient (DSC) and intersection of union (IoU) of 0.794 and 0.676, respectively. Superior performance demonstrates its efficacy to capture distinguished enhancement characteristics for lesion recognition. Code is available https://github.com/wanpeng16/DpRAN.

Long-term impact of myocardial inflammation on quantitative myocardial perfusion—a descriptive PET/MR myocarditis study

PurposeWhether myocardial inflammation causes long-term sequelae potentially affecting myocardial blood flow (MBF) is unknown. We aimed to assess the effect of myocardial inflammation on quantitative MBF parameters, as assessed by 13N-ammonia positron emission tomography myocardial perfusion imaging (PET-MPI) late after myocarditis.MethodsFifty patients with a history of myocarditis underwent cardiac magnetic resonance (CMR) imaging at diagnosis and PET/MR imaging at follow-up at least 6 months later. Segmental MBF, myocardial flow reserve (MFR), and 13N-ammonia washout were obtained from PET, and segments with reduced 13N-ammonia retention, resembling scar, were recorded. Based on CMR, segments were classified as remote (n = 469), healed (inflammation at baseline but no late gadolinium enhancement [LGE] at follow-up, n = 118), and scarred (LGE at follow-up, n = 72). Additionally, apparently healed segments but with scar at PET were classified as PET discordant (n = 18).ResultsCompared to remote segments, healed segments showed higher stress MBF (2.71 mL*min−1*g−1 [IQR 2.18–3.08] vs. 2.20 mL*min−1*g−1 [1.75–2.68], p < 0.0001), MFR (3.78 [2.83–4.79] vs. 3.36 [2.60–4.03], p < 0.0001), and washout (rest 0.24/min [0.18–0.31] and stress 0.53/min [0.40–0.67] vs. 0.22/min [0.16–0.27] and 0.46/min [0.32–0.63], p = 0.010 and p = 0.021, respectively). While PET discordant segments did not differ from healed segments regarding MBF and MFR, washout was higher by ~ 30% (p < 0.014). Finally, 10 (20%) patients were diagnosed by PET-MPI as presenting with a myocardial scar but without a corresponding LGE.ConclusionIn patients with a history of myocarditis, quantitative measurements of myocardial perfusion as obtained from PET-MPI remain altered in areas initially affected by inflammation.Graphical abstractCMR = cardiac magnetic resonance; PET = positron emission tomography; LGE = late gadolinium enhancement

Pretreatment brain CT perfusion thresholds for predicting final infarct volume in distal medium vessel occlusions.

Quantitative CT perfusion (CTP) thresholds for assessing the extent of ischemia in patients with acute ischemic stroke (AIS) have been established; relative cerebral blood flow (rCBF) <30% is typically used for estimating estimated ischemic core volume and Tmax (time to maximum) >6seconds for critical hypoperfused volume in AIS patients with large vessel occlusion (LVO). In this study, we aimed to identify the optimal threshold values for patients presenting with AIS secondary to distal medium vessel occlusions (DMVOs). In this retrospective study, consecutive AIS patients with anterior circulation DMVO who underwent pretreatment CTP and follow-up MRI/CT were included. The CTP data were processed by RAPID (iSchemaView, Menlo Park, CA) to generate estimated ischemic core volumes using rCBF <20%, <30%, <34%, and <38% and critical hypoperfused volumes using Tmax (seconds) >4, >6, >8, and >10. Final infarct volumes (FIVs) were obtained from follow-up MRI/CT within 5days of symptom onset. Diagnostic performance between CTP thresholds and FIV was assessed in the successfully and unsuccessfully recanalized groups. Fifty-five patients met our inclusion criteria (32 female [58.2%], 68.0±12.1years old [mean±SD]). Recanalization was attempted with intravenous tissue-type plasminogen activator and mechanical thrombectomy in 27.7% and 38.1% of patients, respectively. Twenty-five patients (45.4%) were successfully recanalized. In the successfully recanalized patients, no CTP threshold significantly outperformed what is used in LVO setting (rCBF<30%). All rCBF CTP thresholds demonstrated fair diagnostic performances for predicting FIV. In unsuccessfully recanalized patients, all Tmax CTP thresholds strongly predicted FIV with relative superiority of Tmax >10seconds (area under the receiver operating characteristic curve=.875, p=.001). In AIS patients with DMVOs, longer Tmax delays than Tmax >6seconds, most notably, Tmax >10seconds, best predict FIV in unsuccessfully recanalized patients. No CTP threshold reliably predicts FIV in the successfully recanalized group nor significantly outperformed rCBF<30%.

Quantitative assessment of gastric ischemic preconditioning on conduit perfusion in esophagectomy: propensity score weighting study.

Gastric ischemic preconditioning prior to esophagectomy has been studied as a method to improve gastric conduit perfusion and reduce anastomotic complications, without conclusive results. The aim of this study is to evaluate the feasibility and safety of gastric ischemic preconditioning in terms of post-operative outcomes and quantitative gastric conduit perfusion. Patients who underwent an esophagectomy with gastric conduit reconstruction between January 2015 and October 2022 at a single high-volume academic center were reviewed. Patient characteristics, surgical approach, post-operative outcomes, and indocyanine green fluorescence angiography data (ingress index for arterial inflow and ingress time for venous outflow, and the distance from the last gastroepiploic branch to the perfusion assessment point) were analyzed. Two propensity score weighting methods were used to investigate whether gastric ischemic preconditioning reduces anastomotic leaks. Multiple linear regression analysis was used to evaluate the conduit perfusion quantitatively. There were 594 esophagectomies with gastric conduit performed, with 41 having a gastric ischemic preconditioning. Among 544 with cervical anastomoses, leaks were seen in 2/30 (6.7%) in the ischemic preconditioning group and 114/514 (22.2%) in the control group (p = 0.041). Gastric ischemic preconditioning significantly reduced anastomotic leaks on both weighting methods (p = 0.037 and 0.047, respectively). Ingress index and time of the gastric conduit with ischemic preconditioning were significantly better than those without preconditioning (p = 0.013 and 0.025, respectively) after removing the effect of the distance from the last gastroepiploic branch to the perfusion assessment point. Gastric ischemic preconditioning results in a statistically significant improvement in conduit perfusion and reduction in post-operative anastomotic leaks.

Comparison of the diagnostic accuracy of dynamic CT perfusion and cardiac CMR with quantitative perfusion: a subanalysis of ADVANTAGE II study

Abstract Funding Acknowledgements Type of funding sources: None. Background The ADVANTAGE II study has evaluated the performance of dynamic myocardial perfusion assessed by CT (CTP) in stented patient using ICA and in particular invasive coronary physiology (FFR and IMR) as gold-standard. Recently, quantitative myocardial blood flow (MBF) analysis using stress cardiac magnetic resonance (CMR) has been showed to detect obstructive coronary artery disease (CAD) and coronary microvascular dysfunction (CMD). In a substudy of ADVANTAGE II we aimed to evaluate the performance of quantitative stress CMR in comparison to CTP. Methods We present data from 39 subjects with clinically indicated ICA who underwent both vasodilator stress CMR using 1.5T MR scanner (General Electric) and dynamic stress myocardial CTP using a last generation scanner characterized by a 16-cm Z-axis coverage. In CMR Quantitative myocardial perfusion imaging was performed using the dual sequence technique (i.e. low-resolution slice for arterial input function and 2–3 short axis slices for myocardial perfusion). Resting MBF (rMBF), Stress MBF (sMBF), and myocardial perfusion reserve (MPR) were measured using Fermi deconvolution (Circle Cvi42). Quantitative perfusion results were displayed on color-encoded pixel-wise maps and on a 16-segment plot with segmental values listed. Results When FFR was used as gold standard the diagnostic accuracy of CTP was higher than those of CCTA (84.7% vs. 61.5%, p&amp;lt;0.001). When IMR was used as gold standard, diagnostic accuracy of CTP was higher than CCTA (82.9% vs. 59.3%, p&amp;lt;0.01, respectively). When the presence of at least one abnormal physiological parameter among FFR and IMR was used as gold standard, the diagnostic accuracy of CTP was higher than that of CCTA (90.8%vs 68%). Quantitative stress CMR using 2.2 ml/min/g as cut-off has a sensitivity of 83.3%, 77.7% and 100% vs QCA, FFR and IMR, respectively with higher performance of dynamic CTP in comparison to quantitative stress CMR. Conclusions In this substudy of ADVANTAGE II, we showed that global sMBF in MRI can accurately identify patients with CAD. Dynamic CTP seems to offer higher value of diagnostic performance in comparison to quantitative CMR that seems to be very promising, but more data are needed.

Evidence for microstructural alteration and microvascular disease in subclinical and overt hypertrophic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation - Clinical Research Training Fellowship Background Disarray and microvascular disease (MVD) are implicated in adverse events in hypertrophic cardiomyopathy (HCM). Advances in CMR permit quantification of microstructural indices reflecting disarray, and microvascular disease. As novel myosin inhibitors provide promise for disease modification, early and disease-specific biomarkers are a rapidly emerging clinical priority. Purpose Using latest imaging techniques, we investigated MVD and disarray in 3 HCM groups: overt disease, either genotype positive (G+LVH+) or negative (G-LVH+), and subclinical HCM (G+LVH-), exploring relationships to electrical changes and genetic substrate. Methods A 207 subject, multi-centre consortium: 102 patients with overt HCM (52 G+LVH+, 50 G-LVH+), 77 subclinical (G+LVH-) and 28 matched healthy volunteers (HV). All underwent ECG, quantitative perfusion (measuring myocardial blood flow (MBF), perfusion reserve (MPR) and perfusion defects) and cardiac diffusion tensor imaging (cDTI) to investigate for evidence of disarray, measured as fractional anisotropy (FA – the directional variability of diffusion, reflecting myocyte disarray), mean diffusivity (MD – reflecting myocyte packing and intra- and extracellular volume) and absolute second eigenvector angle (E2A –measuring orientation of sheetlets, functional units of myocytes that re-orientate to facilitate wall-thickening). Results Compared to HV, overt HCM had evidence of microstructural alteration (lower FA (suggestive of disarray), higher MD and higher E2A, all p&amp;lt;0.001) and MVD (lower stress MBF and MPR p&amp;lt;0.001). Compared to G+LVH+, G-LVH+ had elevated E2A (64.4°(58.7–66.5) vs 60.1°(55.6–63.7 p = 0.006)). Perfusion defects were found in all G+ but not all G- overt disease (100%(52/52) vs 82%(41/50) p = 0.001). Compared to HV, subclinical HCM (G+LVH-) had evidence of microstructural alteration (lower FA suggestive of disarray, higher MD and higher E2A, all p&amp;lt;0.001) and MVD (reduced stress MBF (2.43±0.52 vs 2.77±0.62ml/g/min p = 0.006) with perfusion defects in 29% (vs 0 HV p = 0.001)). Microstructural markers and MVD were independently associated, in both overt and subclinical disease (overt: E2A and stress MBF: β=-0.29, p = 0.002; subclinical: those with perfusion defects (vs without) had lower FA &amp; higher E2A). Disarray markers and MVD independently associated with pathological ECG abnormalities in both overt and subclinical disease, after adjustment for degree of fibrosis and LVH (overt: FA odds ratio (OR) for abnormal ECG=3.2, p = 0.014; stress MBF OR=2.8, p = 0.013; subclinical: FA OR=3.4, p = 0.006, MPR OR=4.0 p = 0.008). Conclusions In Hypertrophic Cardiomyopathy, sarcomere mutation carriers without hypertrophy have microstructural alterations and microvascular disease that are detectable, correlate, and associate with pathological ECG changes. These are more prominent once LVH is present, with genotype positive and genotype negative overt disease patients having differing phenotypes.

Automated quantitative myocardial perfusion cardiac magnetic resonance with artificial intelligence-based arterial input function correction versus fractional flow reserve

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Wellcome Trust. Background Quantitative myocardial perfusion cardiac magnetic resonance (QP-CMR) is gaining importance in clinical practice due to the increasing availability of automated processing software. However, a significant obstacle in the widespread deployment of QP-CMR is the accurate estimation of the arterial input function (AIF), as this is precluded by the non-linear relationship between observed MR signal and the concentration of contrast agent. Modern solutions favour a dual-saturation acquisition sequence, acquiring specific low-resolution images with a short saturation time to minimise the signal saturation of the AIF. However, this approach is limited by the availability of the pulse sequence. Recently, the AI-AIF has been proposed (1), which uses an artificial intelligence (AI)-based correction of the AIF, without the need for a dual-sequence or dual-bolus acquisition. Purpose In this work, we compare QP-CMR values, quantified with the AI-AIF versus the invasive reference standard: fractional flow reserve (FFR), to identify diagnostically significant coronary artery disease (CAD), as defined by FFR &amp;lt; 0.80. Methods This study enrolled 18 patients (mean age 65 (± 11), 8 female) who underwent stress perfusion CMR (Philips Achieva 3T) and invasive FFR assessment of at least one coronary artery. Perfusion was quantified in a fully-automated manner with motion compensation (2) and AI-based segmentation and processing (3), using a Fermi function-constrained deconvolution. Fully automated pixelwise perfusion maps were generated, and further subdivided into 16 myocardial segments. Segments were assigned to their respective perfusion territory (4) and the QP value for a territory is given as the mean of its two lowest segments. Receiver operating characteristic (ROC) analysis was performed to identify cut-off thresholds and report the diagnostic accuracy of the proposed approach. Results The overall mean QP-CMR value was 2.29 ml/min/g (± 0.32). Figure 1 shows QP maps and FFR values for 3 example patients. The mean QP-CMR value was 2.09 ml/min/g (± 0.36) in patients with significant CAD and 2.95 ml/min/g (± 0.48) in patients without significant CAD. In total, 28 vessels underwent FFR assessment with 12 vessels in 10 patients being positive for significant CAD (FFR &amp;lt; 0.80). The mean QP-CMR value in FFR-positive coronary territories was 1.76 ml/min/g (± 0.37). The ROC curves are shown in Figure 2 on a per-vessel (left) and per-patient (right) level. The optimal QP threshold on a per-vessel level is 2.11 ml/min/g and on a per-patient level is 1.96 ml/min/g. Conclusion QP-CMR is feasible with the AI-AIF and does not require dual-sequence acquisition or a dual contrast injection. The QP values derived after the AI-based correction of the AIF show good agreement with FFR assessment of epicardial coronary disease. However, due to the limited sample size, further work is required to confirm these findings.

Impact of myocardial inflammation on quantitative myocardial perfusion at long-term follow-up - a descriptive hybrid PET/MR myocarditis study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation (SNSF). Background Whether myocardial inflammation causes long-term sequelae potentially affecting myocardial blood flow (MBF) is unknown. Objectives To assess the effect of myocardial inflammation on quantitative MBF parameters, as assessed by 13N-ammonia positron emission tomography myocardial perfusion imaging (PET-MPI) late after myocarditis. Methods Fifty patients with a history of myocarditis underwent cardiac magnetic resonance (CMR) imaging at diagnosis and PET/MR imaging at follow-up at least 6 months later. Segmental MBF, myocardial flow reserve (MFR), and 13N-ammonia washout were obtained from PET, and segments with reduced 13N-ammonia retention, resembling scar, were recorded. Based on CMR, segments were classified as remote (n=469), healed (inflammation at baseline but no late gadolinium enhancement [LGE] at follow-up, n=118), and scarred (LGE at follow-up, n=72). Additionally, apparently healed segments but with scar at PET were classified as PET discordant (n=18). Results Compared to remote segments, healed segments showed higher stress MBF (2.71mL*min-1*g-1 [IQR 2.18–3.08] vs. 2.20 mL*min-1*g-1 [1.75–2.68], p&amp;lt;0.0001), MFR (3.78 [2.83–4.79] vs. 3.36 [2.60–4.03], p&amp;lt;0.0001) and washout (rest 0.24/min [0.18–0.31] and stress 0.53/min [0.40–0.67] vs. 0.22/min [0.16–0.27] and 0.46/min [0.32–0.63], p = 0.010 and p = 0.021, respectively). While PET discordant segments did not differ from healed segments regarding MBF and MFR, washout was higher by ∼30% (p&amp;lt;0.014). Finally, 10 (20%) patients were diagnosed by PET-MPI as presenting with myocardial scar but without corresponding LGE. Conclusions In patients with a history of myocarditis, quantitative measurements of myocardial perfusion as obtained from PET-MPI remain altered in areas initially affected by inflammation.

#6323 RENAL CONTRAST-ENHANCED ULTRASOUND AND GLOMERULONEPHRITIS: A GOOD MARKER OF DISEASE ACTIVITY

Abstract Background Contrast-enhanced ultrasound (CEUS) could provide a lot of information of renal blood flow. Renal blood flow is an excellent marker of inflammatory and fibrotic processes in the kidney such as glomerulonephritis. Therefore, in patients with these diseases, renal CEUS can be both a prognostic marker and an index of response to therapy. Currently in the literature there are preliminary studies showing the role of CEUS in terms of histology and outcome in the evaluation of patients with glomerulonephritis. In this pilot study we used perfusion CEUS parameters (WiR and WoR; WiAUC and WoAUC) as possible markers of renal microvascular damage. We compared the perfusion parameters with the clinical and histological findings of our patients. Method Eighteen patients with clinical and laboratory signs of glomerulonephritis were enrolled. All patients underwent ultrasound-assisted renal biopsy and B-mode ultrasound examination, color Doppler ultrasound and contrast-enhanced ultrasound. Time Intensity (TI) curves were obtained from renal CEUS. TI curves and several quantitative perfusion parameters were defined using VueBox® Quantitation Software. Results From April to October 2022, 18 patients (12 men and 6 women) with clinical and laboratory suspicion of glomerular disease were enrolled. Median age was 48.05 years, all patients underwent renal biopsy and contrast-enhanced ultrasound at basal condition. Table 1 shows patients characteristics. CKD patients were stratified into two groups according to their eGFR: group I (eGFR &amp;lt; 60 ml/min/1.73 m2, n. = 4) and group II (eGFR ≥ 60 ml/min/1.73 m2, n. = 3). Moreover, we divided patients into two groups based on the presence of nephrotic-range proteinuria (≥ 3.5 g/24h). At this time, seven patient data are suitable for analysis. The small sample size at present does not allow for statistical significance. However, in our study, the persistence of contrast agent signal during the wash-out phase was differed markedly in correlation with the degree of CKD. In particular, we observed a slower wash-in phase in the presence of vascular hyalinosis (Fig. 1). Conclusion Our experience seems to confirm that CEUS parameters can be excellent indicators both in terms of patient disease outcomes and histological data. CEUS can effectively and quantitatively demonstrate renal microvascular perfusion in patients with glomerulonephritis. Future goal is that CEUS could also be a prognostic and follow-up marker after renal biopsy in patients with glomerulonephritis.

Histogram analysis of dynamic contrast-enhanced magnetic resonance imaging to predict extramural venous invasion in rectal cancer

BackgroundTo explore the potential of histogram analysis (HA) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in the identification of extramural venous invasion (EMVI) in rectal cancer patients.MethodsThis retrospective study included preoperative images of 194 rectal cancer patients at our hospital between May 2019 and April 2022. The postoperative histopathological examination served as the reference standard. The mean values of DCE-MRI quantitative perfusion parameters (Ktrans, Kep and Ve) and other HA features calculated from these parameters were compared between the pathological EMVI-positive and EMVI-negative groups. Multivariate logistic regression analysis was performed to establish the prediction model for pathological EMVI-positive status. Diagnostic performance was assessed and compared using the receiver operating characteristic (ROC) curve. The clinical usefulness of the best prediction model was further measured with patients with indeterminate MRI-defined EMVI (mrEMVI) score 2(possibly negative) and score 3 (probably positive).ResultsThe mean values of Ktrans and Ve in the EMVI-positive group were significantly higher than those in the EMVI-negative group (P = 0.013 and 0.025, respectively). Significant differences in Ktrans skewness, Ktrans entropy, Ktrans kurtosis, and Ve maximum were observed between the two groups (P = 0.001,0.002, 0.000, and 0.033, respectively). The Ktrans kurtosis and Ktrans entropy were identified as independent predictors for pathological EMVI. The combined prediction model had the highest area under the curve (AUC) at 0.926 for predicting pathological EMVI status and further reached the AUC of 0.867 in subpopulations with indeterminate mrEMVI scores.ConclusionsHistogram Analysis of DCE-MRI Ktrans maps may be useful in preoperative identification of EMVI in rectal cancer, particularly in patients with indeterminate mrEMVI scores.

Towards quantitative digital subtraction perfusion angiography: An animal study.

X-ray digital subtraction angiography (DSA) is the imaging modality for peri-procedural guidance and treatment evaluation in (neuro-) vascular interventions. Perfusion image construction from DSA, as a means of quantitatively depicting cerebral hemodynamics, has been shown feasible. However, the quantitative property of perfusion DSA has not been well studied. To comparatively study the independence of deconvolution-based perfusion DSA with respect to varying injection protocols, as well as its sensitivity to alterations in brainconditions. We developed a deconvolution-based algorithm to compute perfusion parametric images from DSA, including cerebral blood volume (CBV ), cerebral blood flow (CBF ), time to maximum (Tmax), and mean transit time (MTT ) and applied it to DSA sequences obtained from two swine models. We also extracted the time intensity curve (TIC)-derived parameters, that is, area under the curve (AUC), peak concentration of the curve, and the time to peak (TTP) from these sequences. Deconvolution-based parameters were quantitatively compared to TIC-derived parameters in terms of consistency upon variations in injection profile and time resolution of DSA, as well as sensitivity to alterations of cerebralcondition. Comparing to TIC-derived parameters, the standard deviation (SD) of deconvolution-based parameters (normalized with respect to the mean) are two to five times smaller, indicating that they are more consistent across different injection protocols and time resolutions. Upon ischemic stroke induced in a swine model, the sensitivities of deconvolution-based parameters are equal to, if not higher than, those of TIC-derivedparameters. In comparison to TIC-derived parameters, deconvolution-based perfusion imaging in DSA shows significantly higher quantitative reliability against variations in injection protocols across different time resolutions, and is sensitive to alterations in cerebral hemodynamics. The quantitative nature of perfusion angiography may allow for objective treatment assessment in neurovascularinterventions.

A changing heart in tako-tsubo syndrome.

A 63-year-old female presented with acute chest pain and ECG showing T wave inversion in the anterior and inferior leads. Troponin T (TnT) was significantly elevated (peak 1378 ng/L; normal <14 ng/L), as was NT-proBNP (3091 ng/L; normal <400 ng/L). Invasive angiography showed unobstructed coronary arteries with mid-ventricular ballooning and hypokinesia on ventriculography (see Supplementary data online, Video S1) and echocardiography (see Supplementary data online, Video S2), suggesting a mid-ventricular tako-tsubo syndrome (TTS). Cardiac magnetic resonance (CMR) was booked but the patient was unable to attend. Focussed history using the InterTAK diagnostic score assessment revealed no emotional or physical triggers. The patient re-presented six months later with similar symptoms and elevated TnT. Inpatient echocardiography showed a reverse TTS pattern (see Supplementary data online, Video S3) and CMR at 1.5T showed basal hypokinesia with matching elevated native T1 (1220 ms; normal 950–1100 ms) and T2 (69 ms; normal <48 ms) (Panels A–B). Quantitative perfusion maps following adenosine stress perfusion to investigate microvascular disease showed basal to mid circumferential hypoperfusion with normal apical myocardial blood flow, not suggestive of specific coronary artery territory ischaemia (Panel D) and no late gadolinium enhancement (LGE) (Panel C), confirming a reverse TTS. The patient further presented two months later with chest pain and TnT elevation. Repeat inpatient CMR on this occasion showed a classic TTS pattern with apical hypokinesia and elevated T1 and T2 (1261 ms and 81 ms, respectively) at the mid to apical segments with no LGE (Panels E–G). The case was further explored but no triggers, including neurological or psychiatric abnormalities were found. Recurrent TTS with different phenotypes has previously been described but is rare, especially without a trigger. Our case illustrates the utility of multimodality imaging in the investigation of TTS; in particular, multiparametric tissue mapping by CMR. Furthermore, the novel quantitative perfusion maps characterising myocardial blood flow added diagnostic utility.

Fully automated pixel-wise quantitative CMR-myocardial perfusion with CMR-coronary angiography to detect hemodynamically significant coronary artery disease.

We applied a fully automated pixel-wise post-processing framework to evaluate fully quantitative cardiovascular magnetic resonance myocardial perfusion imaging (CMR-MPI). In addition, we aimed to evaluate the additive value of coronary magnetic resonance angiography (CMRA) to the diagnostic performance of fully automated pixel-wise quantitative CMR-MPI for detecting hemodynamically significant coronary artery disease (CAD). A total of 109 patients with suspected CAD were prospectively enrolled and underwent stress and rest CMR-MPI, CMRA, invasive coronary angiography (ICA), and fractional flow reserve (FFR). CMRA was acquired between stress and rest CMR-MPI acquisition, without any additional contrast agent. Finally, CMR-MPI quantification was analyzed by a fully automated pixel-wise post-processing framework. Of the 109 patients, 42 patients had hemodynamically significant CAD (FFR ≤ 0.80 or luminal stenosis ≥ 90% on ICA) and 67 patients had hemodynamically non-significant CAD (FFR ˃ 0.80 or luminal stenosis < 30% on ICA) were enrolled. On the per-territory analysis, patients with hemodynamically significant CAD had higher myocardial blood flow (MBF) at rest, lower MBF under stress, and lower myocardial perfusion reserve (MPR) than patients with hemodynamically non-significant CAD (p < 0.001). The area under the receiver operating characteristic curve of MPR (0.93) was significantly larger than those of stress and rest MBF, visual assessment of CMR-MPI, and CMRA (p < 0.05), but similar to that of the integration of CMR-MPI with CMRA (0.90). Fully automated pixel-wise quantitative CMR-MPI can accurately detect hemodynamically significant CAD, but the integration of CMRA obtained between stress and rest CMR-MPI acquisition did not provide significantly additive value. • Full quantification of stress and rest cardiovascular magnetic resonance myocardial perfusion imaging can be postprocessed fully automatically, generating pixel-wise myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) maps. • Fully quantitative MPR provided higher diagnostic performance for detecting hemodynamically significant coronary artery disease, compared with stress and rest MBF, qualitative assessment, and coronary magnetic resonance angiography (CMRA). • The integration of CMRA and MPR did not significantly improve the diagnostic performance of MPR alone.

Transient ischaemic dilation ratio thresholds in patients with zero coronary calcium score undergoing exercise or dipyridamole stress SPECT myocardial perfusion imaging using a cadmium-zinc-telluride camera.

Transient ischaemic dilation (TID) is a marker of underlying extensive coronary artery disease (CAD) during myocardial perfusion imaging (MPI). The cut-off for a normal TID ratio (TIDr) value is often derived from a cohort of individuals with no apparent CAD. Varying criteria have been used to define the absence of CAD. We aim to derive TIDr cut-offs using patients with normal MPI and coronary artery calcium (CAC) score of zero, and compare the TIDr obtained from different software packages. We studied 232 patients with zero CAC and normal MPI undergoing exercise or dipyridamole stress using either a 1- or 2-day protocol. All patients were scanned in the supine position with a cadmium-zinc-telluride camera. TIDr was automatically generated using quantitative perfusion SPECT (QPS) software initially, and subsequently using Myometrix for comparison. The TIDr cut-offs calculated using the mean + 2 standard deviation were 1.29 and 1.24 for the 1- and 2-day protocol groups, respectively. In patients undergoing a 2-day protocol, dipyridamole stress resulted in significantly higher mean TIDr when compared to exercise stress (1.07 ± 0.13 vs. 1.01 ± 0.12, P = 0.035). Myometrix-derived TIDr were also significantly lower compared to QPS-derived values for most protocols except for 2-day exercise stress. This study is the first to derive TIDr threshold values using a normal population defined by zero CAC and normal MPI. TIDr was found to vary depending on stress modality, protocol as well as the software used.

Potential utility of B-type natriuretic peptides in secondary prevention following percutaneous coronary intervention in remote communities of Western Australia

Introduction A third of all acute coronary events that present in the Australian population occur in patients with established coronary heart disease. This study assessed the prognostic value of combined B-type natriuretic peptides (BNP) measurement and quantitative myocardial perfusion scan (MPS) data for cardiac events (CE). Material and methods This retrospective cohort study involved 133 patients from rural Western Australia. The cut-off for normality was 6.0 for qualitative summed difference scores (SDS) of MPS and 400 pg/mL for BNP. Results Patients with no CE had a mean SDS and BNP (1.52 with a 95% CI of 0.34 to 2.69), (175.9 with a 95% CI of 112.7-239.1) that was lower than patients with CE (6.54 with 95% CI 4.18-9.89) (P = 0.0003), (669.1 with 95% CI 543.9-794.3) (P < 0.0001). The sensitivity and specificity of combined testing for predicting CE respectively were 79.6% and 86.3% for SDS, 84.6% and 94.1% for BNP, and 100% and 92.7% for SDS and BNP combined. Discussion and conclusion Elevated BNP is marginally superior to MPS in predicting CEs in patients who have previously undergone percutaneous coronary intervention (PCI); however, MPS can identify the region of myocardium most at risk. Routine BNP monitoring in this subgroup may serve as secondary prevention by identifying subclinical disease.

Optical Coherence Tomography Angiography in Retinal Vascular Disorders.

Traditionally, abnormalities of the retinal vasculature and perfusion in retinal vascular disorders, such as diabetic retinopathy and retinal vascular occlusions, have been visualized with dye-based fluorescein angiography (FA). Optical coherence tomography angiography (OCTA) is a newer, alternative modality for imaging the retinal vasculature, which has some advantages over FA, such as its dye-free, non-invasive nature, and depth resolution. The depth resolution of OCTA allows for characterization of the retinal microvasculature in distinct anatomic layers, and commercial OCTA platforms also provide automated quantitative vascular and perfusion metrics. Quantitative and qualitative OCTA analysis in various retinal vascular disorders has facilitated the detection of pre-clinical vascular changes, greater understanding of known clinical signs, and the development of imaging biomarkers to prognosticate and guide treatment. With further technological improvements, such as a greater field of view and better image quality processing algorithms, it is likely that OCTA will play an integral role in the study and management of retinal vascular disorders. Artificial intelligence methods-in particular, deep learning-show promise in refining the insights to be gained from the use of OCTA in retinal vascular disorders. This review aims to summarize the current literature on this imaging modality in relation to common retinal vascular disorders.

The Preventive Effects of Probiotic Prevotella histicola on the Bone Loss of Mice with Ovariectomy-Mediated Osteoporosis.

It has been demonstrated that the disturbance of gut microbiota (GM) is closely related to the reduction of bone mass and incidence of osteoporosis (OP). The aim of this study is to investigate whether the supplementation of Prevotella histicola (Ph) can prevent the bone loss in mice with ovariectomy (OVX)-mediated OP, and further explore relevant mechanisms. Regular (once a day for 8 consecutive weeks) and quantitative (200 µL/d) perfusion of Ph (the bacteria that orally gavaged) was conducted starting from 1 week after the construction of mice models. Bone mass and bone microstructure were detected by Micro-computed tomography (Micro-CT). Expressions of intestinal permeability, pro-inflammatory cytokines, and osteogenic and osteoclastic activities of mice were analyzed by histological staining and immunohistochemistry (IHC). 16S rRNA high throughput sequencing technique was applied to analyze the alterations of composition, abundance, and diversity of collected feces. Regular and quantitative perfusion of Ph mitigated the bone loss in mice with OVX-mediated OP. Compared with OVX + PBS group, perfusion of Ph repressed osteoclastogenesis and promoted osteogenesis, reduced release of pro-inflammatory cytokine cytokines (interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α)), and reversed expressions of tight junction proteins (zonula occludens protein 1 (ZO-1) and Occludin). Besides, the perfusion of Ph improved the composition, abundance, and diversity of GM. Collectively, this study revealed that regular and quantitative perfusion of Ph can improve the bone loss in mice with OVX-mediated OP by repairing intestinal mucosal barrier damage, optimizing intestinal permeability, inhibiting release of pro-osteoclastogenic cytokines, and improving disturbance of GM.

Alternatives to DEXA for the assessment of bone density: a systematic review of the literature and future recommendations.

Osteoporosis has significant implications in spine fusion surgery, for which reduced spinal bone mineral density (BMD) can result in complications and poorer outcomes. Currently, dual-energy x-ray absorptiometry (DEXA) is the gold standard for radiographic diagnosis of osteoporosis, although DEXA accuracy may be limited by the presence of degenerative spinal pathology. In recent years, there has been an evolving interest in using alternative imaging, including CT and MRI, to assess BMD. In this systematic review of the literature, the authors assessed the use and effectiveness of MRI, opportunistic CT (oCT), and quantitative CT (qCT) to measure BMD. In accordance with the PRISMA guidelines, the authors conducted a systematic search for articles posted on PubMed between the years 2000 and 2022 by using the keywords "opportunistic CT, quantitative CT, MRI" AND "bone density" AND "spine." Inclusion criteria consisted of articles written in English that reported studies pertaining to human or cadaveric subjects, and studies including a measure of spinal BMD. Articles not related to spinal BMD, osteoporosis, or spinal surgery or reports of studies that did not include the use of spinal MRI or CT were excluded. Key study outcomes were extracted from included articles, and qualitative analysis was subsequently performed. The literature search yielded 302 articles. Forty-two articles reported studies that met the final inclusion criteria. Eighteen studies utilized MRI protocols to correlate spinal BMD with vertebral bone quality scores, M-scores, and quantitative perfusion markers. Eight studies correlated oCT with spinal BMD, and 16 studies correlated qCT with spinal BMD. With oCT and qCT imaging, there was consensus that Hounsfield unit (HU) values > 160 demonstrated significant reduction in risk of osteoporosis, whereas HU values < 110 were significantly correlated with osteoporosis. Osteoporosis is increasingly recognized as a significant risk factor for complications after spinal fusion surgery. Consequently, preoperative assessment of BMD is a critical factor to consider in planning surgical treatment. Although DEXA has been the gold standard for BMD measurement, other imaging modalities, including MRI, oCT, and qCT, appear to be viable alternatives and may offer cost and time savings.

A quantitative laser speckle-based velocity prediction approach using machine learning

Laser speckle contrast imaging (LSCI) can be applied to non-invasive blood perfusion measurement with high resolution and fast speed. However, it is lack of measurement accuracy. The aim of this study is to enable quantitative measurement of LSCI by using Artificial Intelligence (AI), and this is achieved by using a set of experimental data obtained from a rotating diffuser (a tissue phantom mimicking blood flow under skins) within simulated flow velocity of 0.08–10.74 mm/s. These data were used to train a three-dimensional convolutional neural network (3D-CNN) to establish a LSCI velocities prediction model (CNN-LSCI) with behavioral feature learning. The trained model has 0.33 MSE (mean squared error) and 0.34 MAPE (mean absolute percentage error) and is verified by ten phantom velocities (0.2-4 mm/s, step is 0.445 mm/s) covering the typical blood flow velocity range of human body (0-2 mm/s) with the correlation of 0.98. The better performance of the proposed model is demonstrated by the results compared to traditional LSCI and multi-exposure laser speckle contrast imaging (MELSCI). This study shows the potential of LSCI to achieve quantitative blood perfusion measurement using machine learning.