Perfusion Maps Research Articles

Sensitivity of Functional Arterial Spin Labelling in Detecting Cerebral Blood Flow Changes

Aims/Background Arterial spin labelling (ASL) is a non-invasive magnetic resonance imaging (MRI) method. ASL techniques can quantitatively measure cerebral perfusion by fitting a kinetic model to the difference between labelled images (tag images) and ones which are acquired without labelling (control images). ASL functional MRI (fMRI) provides quantitative perfusion maps by using arterial water as an endogenous tracer instead of depending on vascular blood oxygenation level.This study aimed to assess the number of pulsed ASL blocks that were needed to provide accurate and reliable regional estimates of cerebral blood flow (CBF) changes when participants engaged in visually guided saccade and fixation task; evaluate the localization to cortical control saccade versus fixation; investigate the relationship between the sensitivity of ASL fMRI and the number of blocks; and compare the sensitivity of blood oxygen level-dependent (BOLD) fMRI and ASL fMRI. Methods The experiment was a block-design paradigm consisting of two conditions: fixation and saccade. No response other than the eye movements of the participants was recorded during the scans. ASL and BOLD fMRI scans were conducted on all participants during the same session. The fMRI study consisted of two functional experiments: a CBF contrast was provided using the ASL sequence, and an optimized BOLD contrast was provided using the BOLD sequence. Results From group analysis in all divided blocks of ASL sessions (4, 6, 8...... 14, 16, 18......26, 28, 30), ASL yielded significant activation clusters in the visual cortex of the bilateral hemisphere from block 4. There was no false activation from block 4. No activation cluster was found by reversing analysis of block 2. Robust and consistent activation in the visual cortex was observed in each of the 14 divided blocks group analysis, and no activation was found in the eye field of the brain. The sensitivity of 4-block was found to be better than that of 8-block. More significant activation clusters of the visual cortex were found in BOLD than in ASL. No activation cluster of parietal eye field (PEF), frontal eye field (FEF) and supplementary eye field (SEF) was detected in ASL. The voxel size of the activation cluster increased with the increasing number of blocks, and the percent signal change in the activation cluster decreased with the escalating block number. The voxel size was positively correlated with the number of blocks (correlation coefficient = 0.98, p < 0.0001), and the percent signal change negatively correlated with the number of blocks (correlation coefficient = –0.90, p < 0.0001). Conclusion The 4-block pulsed functional ASL (fASL) presents accurate and reliable activation, with minimal time-on-task effect and little adverse impact of time, in participants engaging in visually guided saccade and fixation tasks. Despite having lower sensitivity than BOLD fMRI, ASL can determine accurate activation location. Although the time-on-task effects affect the observation for the sensitivity of ASL over task time, it is suggested that ASL fMRI may provide a powerful method for pinpointing the time-on-task effect over a long period of time.

A Novel Self-Supervised Learning-Based Method for Dynamic CT Brain Perfusion Imaging.

Dynamic computed tomography (CT)-based brain perfusion imaging is a non-invasive technique that can provide quantitative measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, due to high radiation dose, dynamic CT scan with a low tube voltage and current protocol is commonly used. Because of this reason, the increased noise degrades the quality and reliability of perfusion maps. In this study, we aim to propose and investigate the feasibility of utilizing a convolutional neural network and a bi-directional long short-term memory model with an attention mechanism to self-supervisedly yield the impulse residue function (IRF) from dynamic CT images. Then, the predicted IRF can be used to compute the perfusion parameters. We evaluated the performance of the proposed method using both simulated and real brain perfusion data and compared the results with those obtained from two existing methods: singular value decomposition and tensor total-variation. The simulation results showed that the overall performance of parameter estimation obtained from the proposed method was superior to that obtained from the other two methods. The experimental results showed that the perfusion maps calculated from the three studied methods were visually similar, but small and significant differences in perfusion parameters between the proposed method and the other two methods were found. We also observed that there were several low-CBF and low-CBV lesions (i.e., suspected infarct core) found by all comparing methods, but only the proposed method revealed longer MTT. The proposed method has the potential to self-supervisedly yield reliable perfusion maps from dynamic CT images.

Influences on rPPG-Based Spatial Blood Perfusion Maps

Abstract Recent studies show the feasibility of using local remote photoplethysmography (rPPG) for non-contact blood perfusion assessment by creating spatial pulsatile blood perfusion maps. While global rPPG has been widely studied for its robustness, e.g. for non-contact measurement of heart rate, local analyses pose greater challenges in terms of noise suppression and thus reliability. In this paper, the effect of temperature and illumination changes on signal-to-noise ratio (SNR) perfusion maps is analysed. The results show the importance of consistent temperature and controlled illumination for improving SNR and ensuring reliable blood perfusion measurements using rPPG. This emphasises the need for standardised external conditions for accurate interpretation of the results and medical applicability.

Imaging Photoplethysmography (iPPG) in Head and Neck Reconstructive Surgery: A Novel Technique for Noninvasive Flap Perfusion Monitoring.

Evaluate imaging photoplethysmography (iPPG) as a novel noninvasive technique to assess flap perfusion in head and neck free flap reconstructive (FFR) surgeries. Intraoperative iPPG was performed in 17 patients undergoing FFR surgery. Imaging consisted of a 30-s video from which perfusion maps were extracted, providing detailed information about blood flow and pulsatility in the flap microvasculature. During each procedure, iPPG acquisitions were acquired representing distinct perfusion conditions of the flap (fully perfused/ischemic/reperfused). When possible, postoperative measurements were performed to assess flap recovery during the critical time period (3 days) and long-term follow-up (30 days). Perfusion maps, displaying iPPG amplitude and delay times, correlated strongly (p < 0.001) with the perfusion status of the tissue. One case of postoperative thrombosis, leading to flap failure, was identified with iPPG. After surgical revision in this case, flap perfusion was restored and confirmed by iPPG. Postoperative follow-up imaging allowed for objective visualization of flap recovery short term (3 days) and up to 30 days after the surgical procedure. This study shows that iPPG is suitable for objective and noninvasive assessment of flap perfusion in head and neck FFR surgery. In addition, postoperative monitoring shows potential for assessing flap perfusion in patients with increased risk of postoperative complications.

Abstract 4145861: Systemic Sclerosis is Associated with Sub-Clinical Abnormalities in Myocardial Energetics, Perfusion and Increased Fibrosis

Background: Primary cardiac involvement in systemic sclerosis (SSc) is heterogenous, poorly defined and associated with significant cardiac morbidity and mortality. The underlying mechanism is not well understood but may include the impact of coronary microvascular dysfunction and myocardial inflammation. Myocardial cellular metabolic alterations in SSc are yet to be established. Aims: Using 31 Phosphorous magnetic resonance spectroscopy ( 31 P MRS) and cardiovascular magnetic resonance (CMR), we aimed to establish if myocardial energetics, measured as phosphocreatine (PCr) /ATP ratio, and quantitative myocardial perfusion were reduced in individuals with SSc compared to healthy volunteers (HV). Methods: A total of 35 age and sex matched participants were recruited (25 SSc, 10 HV). All subjects underwent 31 P MRS and comprehensive CMR protocol including volumetric analysis, quantitative myocardial perfusion and T1 mapping. Results: Table-1 shows clinical and CMR / 31 P MRS data. Bi-ventricular volumes, systolic function and left atrial function were similar in both groups. NT-Pro BNP and myocardial extra cellular volume (ECV) were significantly increased in SSc. Both PCr/ATP and myocardial perfusion reserve (MPR) were significantly reduced in SSc compared with controls. The disease activity as measured by the European Scleroderma Trials and Research group (EUSTAR) activity index did not correlate with either NTproBNP (P=0.79), PCr/ATP (P=0.35) or MPR (P=0.6). Conclusions: In addition to validating our previous observations of reduced perfusion and increased myocardial fibrosis in SSc, we have demonstrated for the first time significant reductions in myocardial energetics in patients with SSc. These findings provide further valuable insight into the pathogenesis of primary myocardial disease in SSc.

Impaired myocardial energetics in both sarcomere positive and negative HCM are linked to arrhythmic risk

Abstract Background Impaired myocardial energetics play a pivotal role in the complex pathophysiology of hypertrophic cardiomyopathy (HCM), and are thought to be mediated by energy-costly sarcomeric mutations and mitochondrial dysfunction (1). Two thirds of HCM patients, however, do not possess pathogenic sarcomeric mutations (2) and instead develop the condition due to a combination of increased polygenic susceptibility and comorbidities. Whether energetic impairment, a target of novel HCM treatments (e.g., myosin modulators such as Mavacamten), similarly affects sarcomere mutation positive (Sarc+) and negative (Sarc-) HCM remains unclear, as does the association between impaired energetics and markers of arrhythmic risk such as hypertrophy severity, cardiac function and non-sustained ventricular tachycardia (NSVT). This study aimed to investigate differences in resting myocardial energetics between Sarc+ and Sarc- HCM by measuring the phosphocreatine-to-adenosine triphosphate (PCr/ATP) ratio using phosphorus magnetic resonance spectroscopy (31P-MRS) and explore the association between impaired energetics and markers of arrhythmic risk in HCM. Methods We recruited one hundred (100) participants (80 non-obstructive HCM patients and 20 age- and sex-matched controls). Myocardial energetics were assessed using 31P-MRS to measure the PCr/ATP ratio. Cardiac magnetic resonance (CMR) imaging including cine, T1 (ShMOLLI), quantitative pixel-wise perfusion mapping (3) and late gadolinium enhancement (LGE) imaging was also performed. In addition, HCM patients underwent 7-day ECG monitoring to document NSVT episodes (3 beats ≥120 bpm). Results HCM patients had impaired myocardial energetics (PCr/ATP ratio) relative to controls (HCM 1.64±0.36 vs controls 1.97±0.32 p&amp;lt;0.001). PCr/ATP ratios did not differ between Sarc+ and Sarc- HCM even after adjustment for confounders including age, hypertrophy and fibrosis burden (Sarc+ 1.64 [1.50-1.78] vs Sarc- 1.64 [1.52-1.77], p=0.993). PCr/ATP ratio showed no correlation with maximum wall thickness (p=0.257), left ventricular ejection fraction (p=0.727) or myocardial perfusion reserve (p=0.851), but did inversely correlate with global longitudinal strain (r=-0.3, p=0.025). Reduced PCr/ATP was associated with presence of fibrosis (LGE+ 1.58±0.35 vs LGE- 1.79±0.37 p=0.025) and with NSVT, independent of age or fibrosis burden (NSVT+ 1.54 [1.40-1.67] vs NSVT- 1.73 [1.62-1.86], p=0.046). Conclusion Myocardial energetics are similarly impaired in Sarc+ and Sarc- HCM, and are independently associated with impaired contractility, greater fibrosis severity and heightened arrhythmic risk. Our findings provide novel mechanistic insights into the potentially favourable response of HCM patients to energy-sparing myosin modulator therapies irrespective of genotype and highlight the potential for cardiac energetics to serve as a marker of arrhythmic risk.

Real-Time Perfusion and Leak Assessment in Bariatric Surgery: Bridging Traditional and Advanced Techniques.

This comprehensive literature review explores the efficacy of real-time perfusion and leak assessment methods in bariatric surgery, comparing traditional techniques with advanced imaging modalities. As the global incidence of obesity and related comorbidities rises, the demand for bariatric surgeries such as Roux-en-Y gastric bypass and sleeve gastrectomy has increased, along with the risk of serious complications like anastomotic and staple line leaks. Traditional intraoperative leak testing methods, including the air leak and methylene blue dye tests, are commonly employed but exhibit inconsistent sensitivity in leak detection. Intraoperative endoscopy, although underutilized, offers enhanced visualization and has been associated with reduced leak and complication rates in certain cases. Emerging technologies such as indocyanine green (ICG) fluorescence, laser speckle contrast imaging (LSCI), and hyperspectral imaging (HSI) provide real-time assessment of tissue perfusion, potentially improving surgical outcomes. ICG fluorescence enables visualization of blood flow to detect ischemia, while LSCI offers immediate, dye-free perfusion mapping, and HSI assesses tissue oxygenation without the need for contrast agents. Despite their promise, these technologies are limited by high costs, technical complexity, and varying accessibility, with current evidence insufficient to confirm their superiority over traditional methods. Future research should focus on large-scale, multicenter trials to validate these advanced techniques and refine their application in clinical practice. Integrating traditional and emerging methods may optimize intraoperative decision-making, reduce complications rates, and enhance patient outcomes in bariatric surgery.

Frontoparietal network integrity supports cognitive function in pre-symptomatic frontotemporal dementia: Multimodal analysis of brain function, structure, and perfusion.

Genetic mutation carriers of frontotemporal dementia can remain cognitively well despite neurodegeneration. A better understanding of brain structural, perfusion, and functional patterns in the pre-symptomatic stage could inform accurate staging and potential mechanisms. We included 207 pre-symptomatic genetic mutation carriers and 188 relatives without mutations. The gray matter volume, cerebral perfusion, and resting-state functional network maps were co-analyzed using linked independent component analysis (LICA). Multiple regression analysis was used to investigate the relationship of LICA components to genetic status and cognition. Pre-symptomatic mutation carriers showed an age-related decrease in the left frontoparietal network integrity, while non-carriers did not. Executive functions of mutation carriers became dependent on the left frontoparietal network integrity in older age. The frontoparietal network integrity of pre-symptomatic mutation carriers showed a distinctive relationship to age and cognition compared to non-carriers, suggesting a contribution of the network integrity to brain resilience. A multimodal analysis of structure, perfusion, and functional networks. The frontoparietal network integrity decreases with age in pre-symptomatic carriers only. Executive functions of pre-symptomatic carriers dissociated from non-carriers.

A Macrocyclic Hybrid PET/MRI Probe for Quantitative Perfusion Imaging In Vivo.

Perfusion dynamics play a vital role in delivering essential nutrients and oxygen to tissues while removing metabolic waste products. Imaging techniques such as magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET) use contrast agents to visualize perfusion and clearance patterns; however, each technique has specific limitations. Hybrid PET/MRI combines the quantitative power and sensitivity of PET with the high functional and anatomical detail of MRI and holds great promise for precision in molecular imaging. However, the development of dual PET/MRI probes has been hampered by challenging synthesis and radiolabeling. Here, we present a novel PET/MRI probe, [18F][Gd(FL1)], which exhibits excellent stability comparable to macrocyclic MRI contrast agents used in clinical practice. The unique molecular design of [18F][Gd(FL1)] allows selective and expeditious radiolabeling of the gadolinium chelate in the final synthetic step. Leveraging the strengths of MRI and PET signals, the probe enables quantitative in vivo mapping of perfusion and excretion dynamics through an innovative voxel-based analysis. The diagnostic capabilities of [18F][Gd(FL1)] were demonstrated in a pilot study on healthy mice, successfully detecting early cases of unilateral renal dysfunction, a condition that is typically challenging to diagnose. This study introduces a new approach for PET/MRI and emphasizes a streamlined probe design for practical synthesis and improved diagnostic accuracy.

Segmentation of acute ischemic stroke lesions based on deep feature fusion

Acute ischemic stroke (AIS) is a common brain disease worldwide, and diagnosing AIS requires effectively utilizing information from multiple Computed Tomography Perfusion (CTP) maps. As far as we know, most methods independently process each CTP map or fail to fully utilize medical prior information when integrating the information from CTP maps. Considering the characteristics of AIS lesions, we propose a method for efficient information fusion of CTP maps to achieve accurate segmentation results. We propose Window Multi-Head Cross-Attention Net (WMHCA-Net), which employs a multi-path U-shaped architecture for encoding and decoding. After encoding, multiple independent windowed cross-attentions are used to deeply integrate information from different maps. During the decoding phase, a Channel Cross-Attention (CCA) module is utilized to enhance information recovery during upsampling. We also added a segmentation optimization module to optimize low-resolution segmentation results, improving the overall performance. Finally, experimental results demonstrate that our proposed method exhibits strong balance and excels across multiple metrics. It can provide more accurate AIS lesion segmentation results to assist doctors in evaluating patient conditions. Our code are available at https://github.com/MTVLab/WMHCA-Net.

Measurement and modeling of xenon gas transfer in the human brain with 1H and hyperpolarized 129Xe MRI

BackgroundThe feasibility of imaging hyperpolarized 129Xe dissolved in brain tissue following inhalation of xenon gas in the lungs has recently been demonstrated in humans. The image contrast in 129Xe brain MRI represents a combination of factors, including regional perfusion, polarization decay and gas transfer rate across the blood-brain barrier. PurposeTo investigate the repeatability of hyperpolarized 129Xe brain MRI in healthy normal individuals and to identify the dominant mechanisms of image contrast by assessing voxel-wise correlation between HP 129Xe brain MRI and models of 129Xe brain uptake derived from 1H arterial spin labeling (ASL) perfusion mapping. Materials and MethodsTo assess repeatability, 3 sets of hyperpolarized 129Xe brain images were acquired from 5 healthy volunteers. Quantitative maps of the human brain, including cerebral blood flow, volume and predicted xenon uptake, were derived from 1H arterial spin labeling and T2-weighted MRI. These maps were then spatially cross-correlated with hyperpolarized 129Xe brain MRI. ResultsSignal to noise ratios of 8.7–17.7 were observed across volunteers for a voxel size of 8 × 8 × 50 mm3 with intra-subject repeatability of between 6 and 29 %. Hyperpolarized 129Xe brain images showed voxel-wise correlations with cerebral blood flow (R = 0.32 to 0.62), volume (R = 0.33 to 0.63) and predicted xenon uptake (R = 0.34 to 0.63), but did not correlate with arterial transit time (R = 0.05 to 0.26). ConclusionVoxel-wise cross correlation between 129Xe and 1H ASL suggests that the regional quantity of dissolved xenon delivered by cerebral blood flow is the dominant mechanism of image contrast in HP 129Xe brain MRI, assuming normal blood-brain barrier function. Combining 1H and 129Xe brain MRI provides new opportunities to quantitatively investigate brain pathophysiology and function.

Cerebral perfusion software: comparative evaluation

IntroductionPerfusion CT (CTP) is crucial in defining the best treatment strategy for patients with acute ischemic stroke. Several software is available for assessing cerebral perfusion maps, which may show some variability in results. We aim to investigate the agreement between CT perfusion values in acute ischemic stroke of 2 different software (Syngo.via and Icobrain) in estimating ischemic core, ischemic penumbra, and mismatch ratio.Methods17 patients (10 women, mean age = 79.5 years) with acute stroke with large vessel occlusion (LVO) were enrolled in our study between August 2022 and March 2023. All patients underwent a CTP scan to determine the best treatment approach: endovascular treatment or systemic fibrinolysis according to DAWN/DEFUSE-3 criteria. All CTP examinations were analyzed using 2 different dedicated software (Syngo.via, Icobrain) and the perfusion values obtained (core, penumbra, mismatch ratio) were compared with each other. A basal CT scan 24 h after treatment was acquired to assess the final infarct volume (FIV) and possible hemorrhagic infarction. Then we compared the true FIV, manually assessed, with the predicted FIV calculated by the two software.ResultsThe values obtained showed that the mean core volumes calculated by Syngo.via and Icobrain did not exhibit any statistically significant differences with a p-value of 0.09. There is no statistically significant difference between the mean penumbra volumes calculated by the two software (p-value = 0.29). There is no statistically significant difference between the mean values of core and penumbra calculated by both software. Furthermore, both Icobrain and Syngo.via gave the same therapeutic indication. Correlation analysis indicated a slightly stronger correlation between the core volume calculated by Icobrain and the FIV (r = 0.98 vs r = 0.94). Both correlations were statistically significant (p = < 0.001).ConclusionThe evaluation of perfusion indices by automated systems may present a certain degree of variability between different software, although they agree on the final therapeutic stratification.

Microglia LILRB4 upregulation reduces brain damage after acute ischemic stroke by limiting CD8+ T cell recruitment

BackgroundLeukocyte immunoglobulin-like receptor B4 (LILRB4) plays a significant role in regulating immune responses. LILRB4 in microglia might influence the infiltration of peripheral T cells. However, whether and how LILRB4 expression aggravates brain damage after acute ischemic stroke remains unclear. This study investigates the role of LILRB4 in modulating the immune response and its potential protective effects against ischemic brain injury in mice.Methods and resultsMicroglia-specific LILRB4 conditional knockout (LILRB4-KO) and overexpression transgenic (LILRB4-TG) mice were constructed by a Cre-loxP system. Then, they were used to investigate the role of LILRB4 after ischemic stroke using a transient middle cerebral artery occlusion (tMCAO) mouse model. Spatial transcriptomics analysis revealed increased LILRB4 expression in the ischemic hemisphere. Single-cell RNA sequencing (scRNA-seq) identified microglia-cluster3, an ischemia-associated microglia subcluster with elevated LILRB4 expression in the ischemic brain. Flow cytometry and immunofluorescence staining showed increased CD8+ T cell infiltration into the brain in LILRB4-KO-tMCAO mice. Behavioral tests, cortical perfusion maps, and infarct size measurements indicated that LILRB4-KO-tMCAO mice had more severe functional deficits and larger infarct sizes compared to Control-tMCAO and LILRB4-TG-tMCAO mice. T cell migration assays demonstrated that LILRB4-KD microglia promoted CD8+ T cell recruitment and activation in vitro, which was mitigated by CCL2 inhibition and recombinant arginase-1 addition. The scRNA-seq and spatial transcriptomics identified CCL2 was predominantly secreted from activated microglia/macrophage and increased CCL2 expression in LILRB4-KD microglia, suggesting a chemokine-mediated mechanism of LILRB4.ConclusionLILRB4 in microglia plays a crucial role in modulating the post-stroke immune response by regulating CD8+ T cell infiltration and activation. Knockout of LILRB4 exacerbates ischemic brain injury by promoting CD8+ T cell recruitment. Overexpression of LILRB4, conversely, offers neuroprotection. These findings highlight the therapeutic potential of targeting LILRB4 and its downstream pathways to mitigate immune-mediated damage in ischemic stroke.

Post-Surgical Non-Invasive Wound Healing Monitoring in Oropharyngeal Mucosa.

Postoperative bleeding is the most significant complication of tonsillectomy. Regular monitoring of post-surgical wound healing in the pharynx is required. For this purpose, we propose endoscope-based non-invasive perfusion mapping and quantification. The combination of imaging photoplethysmography and image processing provides automated wound area selection and microcirculation characterization. In this feasibility study, we demonstrate the first results of the proposed approach to wound monitoring in clinical trial on eight patients after tonsillectomy. Combination of probe-based optical system and image processing algorithms can provide the valuable and consistent data on perfusion distribution. The quantitative microcirculation data obtained 1, 4, and 7 days after surgery are in good agreement with existing monitoring protocols.

Turn-table micro-CT scanner for dynamic perfusion imaging in mice: design, implementation, and evaluation

Objective.This study introduces a novel desktop micro-CT scanner designed for dynamic perfusion imaging in mice, aimed at enhancing preclinical imaging capabilities with high resolution and low radiation doses.Approach.The micro-CT system features a custom-built rotating table capable of both circular and helical scans, enabled by a small-bore slip ring for continuous rotation. Images were reconstructed with a temporal resolution of 3.125 s and an isotropic voxel size of 65µm, with potential for higher resolution scanning. The system's static performance was validated using standard quality assurance phantoms. Dynamic performance was assessed with a custom 3D-bioprinted tissue-mimetic phantom simulating single-compartment vascular flow. Flow measurements ranged from 1.51to 9 ml min-1, with perfusion metrics such as time-to-peak, mean transit time, and blood flow index calculated.In vivoexperiments involved mice with different genetic risk factors for Alzheimer's and cardiovascular diseases to showcase the system's capabilities for perfusion imaging.Main Results.The static performance validation confirmed that the system meets standard quality metrics, such as spatial resolution and uniformity. The dynamic evaluation with the 3D-bioprinted phantom demonstrated linearity in hemodynamic flow measurements and effective quantification of perfusion metrics.In vivoexperiments highlighted the system's potential to capture detailed perfusion maps of the brain, lungs, and kidneys. The observed differences in perfusion characteristics between genotypic mice illustrated the system's capability to detect physiological variations, though the small sample size precludes definitive conclusions.Significance.The turn-table micro-CT system represents a significant advancement in preclinical imaging, providing high-resolution, low-dose dynamic imaging for a range of biological and medical research applications. Future work will focus on improving temporal resolution, expanding spectral capabilities, and integrating deep learning techniques for enhanced image reconstruction and analysis.

Perfusion parameter map generation from TOF-MRA in stroke using generative adversarial networks

PurposeTo generate perfusion parameter maps from Time-of-flight magnetic resonance angiography (TOF-MRA) images using artificial intelligence to provide an alternative to traditional perfusion imaging techniques. Materials and methodsThis retrospective study included a total of 272 patients with cerebrovascular diseases; 200 with acute stroke (from 2010 to 2018), and 72 with steno-occlusive disease (from 2011 to 2014). For each patient the TOF MRA image and the corresponding Dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) were retrieved from the datasets. The authors propose an adapted generative adversarial network (GAN) architecture, 3D pix2pix GAN, that generates common perfusion maps (CBF, CBV, MTT, TTP, Tmax) from TOF-MRA images. The performance was evaluated by the structural similarity index measure (SSIM). For a subset of 20 patients from the acute stroke dataset, the Dice coefficient was calculated to measure the overlap between the generated and real hypoperfused lesions with a time-to-maximum (Tmax) > 6 s. ResultsThe GAN model exhibited high visual overlap and performance for all perfusion maps in both datasets: acute stroke (mean SSIM 0.88–0.92, mean PSNR 28.48–30.89, mean MAE 0.02–0.04 and mean NRMSE 0.14–0.37) and steno-occlusive disease patients (mean SSIM 0.83–0.98, mean PSNR 23.62–38.21, mean MAE 0.01–0.05 and mean NRMSE 0.03–0.15). For the overlap analysis for lesions with Tmax>6 s, the median Dice coefficient was 0.49. ConclusionOur AI model can successfully generate perfusion parameter maps from TOF-MRA images, paving the way for a non-invasive alternative for assessing cerebral hemodynamics in cerebrovascular disease patients. This method could impact the stratification of patients with cerebrovascular diseases. Our results warrant more extensive refinement and validation of the method.

ПЕРФУЗИОННАЯ КОМПЬЮТЕРНАЯ ТОМОГРАФИЯ – НОВЫЕ ГОРИЗОНТЫ В ДИАГНОСТИКЕ ЗАБОЛЕВАНИЙ ПОДЖЕЛУДОЧНОЙ ЖЕЛЕЗЫ

Abstract. Introduction. According to the World Health Organization, the most common disease of the pancreas is acute pancreatitis, which can lead to the development of pancreatic necrosis. In this regard, early diagnosis and assessment of the pancreatic necrosis risk development are of paramount importance for choosing adequate treatment approaches and improving outcomes for patients. Radiological research methods have become the “gold” standard in clinical practice for the primary diagnosis of pancreatic diseases. Contrast-enhanced computed tomography has traditionally been used to visualize the pancreas and assess the extent of inflammation and necrotic changes. However, standard computed tomography has limitations in assessing tissue perfusion, which is an important aspect of the pathophysiology of acute pancreatitis. Perfusion computed tomography of the pancreas has become a colossal breakthrough in radiation imaging, has become widespread as a method that allows the quantitative assessment of blood supply to the pancreas, including information about microcirculation, and it can be used for the early detection of ischemic changes that precede tissue necrosis in the pancreas. Aim. To study the capabilities of perfusion computed tomography and computed tomography angiography of the pancreas for evaluating the area of pancreatic necrosis in acute pancreatitis, with the aim of improving diagnosis and planning treatment measures to minimize the consequences and increase patient survival. Materials and Methods. A single-center examination was carried out on 42 patients (18 women, 24 men, mean age 38±2 years) with suspected acute pancreatitis. All patients underwent perfusion computed tomography within the first 3 days; over the next 3-5 days, computed tomography angiography of the pancreas was performed with bolus intravenous contrast to confirm the development of necrotic changes. Results and Discussion. After performing perfusion computed tomography within the first 3 days from the onset of symptoms, areas of ischemic damage to the pancreas tissue were identified in 16 (38.1%) out of 42 patients. After computed tomography angiography, the development of necrotic changes was confirmed in 7 patients (16.7%). The localization of the necrosis zone detected in computed tomography coincided with the ischemic zones on the color hemodynamic maps of perfusion computed tomography.

Assessment of Blood Flow Velocity in Retinal Vasculitis Using the Retinal Function Imager-A Pilot Study.

Background: This pilot study aimed to evaluate the Retinal Function Imager (RFI) for visualizing retinal vasculature and assessment of blood flow characteristics in patients with retinal vasculitis. The RFI is a non-invasive imaging device measuring the blood flow velocity (BFV) in secondary and tertiary retinal vessels using hemoglobin as an intrinsic motion-contrast agent. Methods: To test the feasibility of the RFI for patients with retinal vasculitis, capillary perfusion maps (nCPMs) were generated from 15 eyes of eight patients (five females; mean age: 49 ± 12 years) with a mean uveitis duration of 74 ± 85 months. Five of these patients had birdshot chorioretinopathy, and three had primarily non-occlusive venous retinal vasculitis of unknown origin. To reflect that the BFV may be more reduced in patients with prolonged disease, patients were classified into a short-term (uveitis duration: 8-15 months) and a long-term uveitis group (uveitis duration: 60-264 months). Data were compared with healthy controls (16 eyes of 11 patients; mean age 45 ± 12 years; 8 females). Results: The mean BFV in the controls was 3.79 ± 0.50 mm/s in the retinal arteries and 2.35 ± 0.44 mm/s in the retinal veins, which was significantly higher compared to the retinal vasculitis group. Patients revealed an arterial BFV of 2.75 ± 0.74 mm/s (p < 0.001) and a venous BFV of 1.75 ± 0.51 mm/s (p = 0.016). In the short-term group, a trend towards a decreased venular and arteriolar BFV was seen, while a significant reduction was observed in the long-term group. The patients' microvasculature anatomy revealed by the nCPMs appeared unevenly distributed and a lower number of blood vessels were seen, along with a lower degree of complexity of their branching patterns, when compared with controls. Conclusions: This study demonstrated a reduction in venular and arteriolar BFVs in patients with retinal vasculitis. BFV alterations were already observed in early disease stages and became more pronounced in progressed disease. Additionally, we showed that retinal microvasculature changes may be observed by nCPMs. Retinal imaging with the RFI may serve as a diagnostic and quantifying tool in retinal vasculitis.

Assessment of myocardial microvascular dysfunction in patients with different stages of diabetes mellitus: An adenosine stress perfusion cardiac magnetic resonance study

PurposeTo examine myocardial perfusion and T1 mapping indicesin individuals with type 2 diabetes mellitus (T2DM) at various stages of glycemic control and whether uncontrolled glycemic levels would worsen myocardial microvascular function. MethodCardiac magnetic resonance examinations were performed on 114 T2DM patients without obstructive coronary artery disease and 55 matched controls. Participants were further divided into four subgroups: Q1 (control); Q2 (prediabetes); Q3 (controlled T2DM) and Q4 (uncontrolled T2DM). The correlation between glycosylated hemoglobin (HbA1c) levels and myocardial perfusion parameters was evaluated. ResultsGlobal myocardial perfusion reserve index (MPRI) was significantly reduced in the Q3 and Q4 subgroups compared to the Q1 or Q2 subgroup (all P<0.001). Compared with the Q1 subgroup, global stress T1 reactivity (stress ΔT1) was significantly reduced in the Q3 and Q4 subgroups (P=0.004 and < 0.001, respectively), but elevated in the Q2 subgroup (P=0.018). Global extracellular volume (ECV) was considerably higher in the Q2 subgroup and gradually rose in the Q3 and Q4 subgroups compared to the Q1 subgroup (P=0.011, 0.001, and 0.007, respectively). HbA1c levels correlated negatively with global MPRI and stress ΔT1, but positively with global ECV (β = -1.993, P<0.001; β = -0.180, P<0.001; and β = 0.127, P<0.001, respectively). ConclusionsGlobal stress ΔT1 reduced in T2DM patients but rose in prediabetes patients. Compared to MPRI, the ECV parameter can indicate diabetes-induced coronary microvascular dysfunction earlier and persists throughout the disorder. Myocardial perfusion and T1 mapping at stress can be used to detect early signs of microvascular dysfunction and subclinical risk factors in patients with T2DM.

Perfusion MRI in Cerebral Venous and Sinus Thrombosis.

Cerebral venous and sinus thrombosis (CVST) leads to perfusion abnormality in the brain. Our aim was to assess perfusion abnormalities in the center and periphery of the parenchymal lesion in CVST patients and correlate with the clinical outcome. Dynamic susceptibility contrast (DSC) perfusion imaging was performed in patients with CVST. Relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), and mean transit time (MTT) values were obtained in the center and periphery of the parenchymal lesion. A total of 30 consecutive patients of CVST were included in the study. Parenchymal lesion was present in 21 (70%) patients. In rest 9, perfusion map was showing some abnormality although conventional MRI was normal. Mean rCBV and MTT were increasing from periphery of the lesion to the center (rCBV 69.93 ± 29.79 at periphery (PL2) to 92.49 ± 32.07 at center of the lesion and 69.19 ± 25.52 at normal appearing contralateral brain parenchyma (NABP). MTT 11.83 ± 3.76 at periphery (PL2) to 15.27 ± 5.49 at center of the lesion and 10.63 ± 3.37 at NABP). rCBV and MTT from abnormal perfusion areas from 9 patients without parenchymal abnormalities are 92.89 ± 17.76 and 15.92 ± 3.66 respectively. There is an increasing trend of MTT and rCBV from periphery to center of the parenchymal lesion. MTT is the most consistent parameter to be abnormal in patients of CVST even in patients without parenchymal lesion. Residual neurological deficit was found in patients with increased rCBV and having large hemorrhagic infarct.