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Background: The no-reflow phenomenon refers to the absence of microvascular reperfusion despite macrovascular reperfusion. Aim: The aim of this analysis was to summarize the available clinical evidence on no-reflow in patients with acute ischemic stroke. Methods: A systematic literature review and a meta-analysis of clinical data on definition, rates, and impact of the no-reflow phenomenon after reperfusion therapy was carried out. A predefined research strategy was formulated according to the Population, Intervention, Comparison, and Outcome (PICO) model and was used to screen for articles in PubMed, MEDLINE, and Embase up to 8 September 2022. Whenever possible, quantitative data were summarized using a random-effects model. Results: Thirteen studies with a total of 719 patients were included in the final analysis. Most studies (n = 10/13) used variations of the Thrombolysis in Cerebral Infarction scale to evaluate macrovascular reperfusion, whereas microvascular reperfusion and no-reflow were mostly assessed on perfusion maps (n = 9/13). In one-third of stroke patients with successful macrovascular reperfusion (29%, 95% confidence interval (CI), 21–37%), the no-reflow phenomenon was observed. Pooled analysis showed that no-reflow was consistently associated with reduced rates of functional independence (odds ratio (OR), 0.21, 95% CI, 0.15–0.31). Conclusion: The definition of no-reflow varied substantially across studies, but it appears to be a common phenomenon. Some of the no-reflow cases may simply represent remaining vessel occlusions, and it remains unclear whether no-reflow is an epiphenomenon of the infarcted parenchyma or causes infarction. Future studies should focus on standardizing the definition of no-reflow with more consistent definitions of successful macrovascular reperfusion and experimental set-ups that could detect the causality of the observed findings. [ABSTRACT FROM AUTHOR]

Background: To clarify the value of computed tomography (CT) perfusion (CTP) imaging in diagnosing early cerebral infarction (CI). Materials and Methods: Totally 100 suspected early CI patients in our hospital from May 2019 to May 2022 were selected and divided into observation and control groups based on examination methods, with 50 patients per group. In control group, patients received plain scanning through 64 row multi-slice spiral CT. On this basis, patients in observation group received CTP in certain area. Comparison of detection rate between groups was conducted. The observation indicators of CI patients detected by CTP in observation group were recorded and analyzed, including the mean transit time (MTT) of the same blood volume, cerebral blood flow (CBF), cerebral blood volume (CBV), and time to peak (TTP). The satisfaction with examination in both groups was explored. Results: CTP presented higher detection accuracy than plain CT scanning (P < 0.05). TTP presented elevation and MTT, CBV and CBF presented depletion in CI position than those in other cerebral position (P < 0.05). TTP, MTT, CBV and CBF presented statistical significance between ischemic penumbra (IP) position and CI position (P < 0.05). The satisfaction degree was elevated in observation group relative to control group (P < 0.05). Conclusion: CTP in early CI has higher diagnostic value and accuracy and elevates patient satisfaction, helping reduce disability and mortality. Additionally, CTP has high maneuverability and flexibility, and can measure IP, reducing the degree of brain tissue damage in patients, and is worthy of clinical application. [ABSTRACT FROM AUTHOR]

Objectives: This study was aimed to quantitatively assess hyperperfusion using arterial spin labeling (ASL) to predict hemorrhagic transformation (HT) in acute ischemic stroke (AIS) patients. Methods: This study enrolled 98 AIS patients with anterior circulation large vessel occlusion within 24 h of symptom onset. ASL was performed before mechanical endovascular therapy. On pre-treatment ASL maps, a region with relative cerebral blood flow (CBF) ≥ 1.4 was defined as an area of hyperperfusion. The maximum CBF (CBFmax) of hyperperfusion was calculated for each patient. A non-contrast CT scan was performed during the subacute phase for the evaluation of HT. Good clinical outcome was defined as a 90-day modified Rankin scale score of 0–2. Results: The CBFmax of hyperperfusion (odds ratio, 1.023; 95% confidence interval [CI], 1.005–1.042; p = 0.012) was an independent risk factor for the status of HT. The CBFmax of hyperperfusion for HT showed an area under the curve of 0.735 (95% CI, 0.588–0.882) with optimal cutoff value, sensitivity, and specificity being 146.5 mL/100 g/min, 76.9%, and 69.6%, respectively. There was a statistically significant relationship between HT grades (from no HT to PH2) and CBFmax of hyperperfusion with a Spearman rank correlation of 0.446 (p = 0.001). In addition, low CBFmax of hyperperfusion were associated with good functional outcome (95% CI, 17.130–73.910; p = 0.002). Conclusions: High CBFmax of hyperperfusion was independently associated with subsequent HT and low CBFmax of hyperperfusion linked to good functional outcome. There was a positive correlation between HT grade and CBFmax. Clinical relevance statement: Arterial spin labeling is a noninvasive and contrast agent–independent technique, which is sensitive in detecting hyperperfusion. This study shows that the cerebral blood flow of hyperperfusion is associated with clinical prognosis, which will benefit more patients. Key Points: • Quantitative assessment of hyperperfusion using pre-treatment arterial spin labeling to predict hemorrhagic transformation and prognosis in acute ischemic stroke patients. • The maximum cerebral blood flow of hyperperfusion was associated with hemorrhagic transformation and clinical prognosis and higher maximum cerebral blood flow of hyperperfusion was associated with higher grade hemorrhagic transformation. • The maximum cerebral blood flow of hyperperfusion can predict hemorrhagic transformation which enables timely intervention to prevent parenchymal hematoma. [ABSTRACT FROM AUTHOR]

The reported incidence of persistent hypoperfusion despite complete recanalization as surrogate for impaired microvascular reperfusion (IMR) has varied widely among clinical studies, possibly due to differences in i) definition of complete recanalization, with only recent Thrombolysis in Cerebral Infarction (TICI) grading schemes allowing distinction between complete (TICI3) and partial recanalization with distal occlusions (TICI2c); ii) operational definition of IMR; and iii) consideration of potential alternative causes for hypoperfusion, notably carotid stenosis, re-occlusion and post-thrombectomy hemorrhage. We performed a systematic review to identify clinical studies that carried out brain perfusion imaging within 72 hrs post-thrombectomy for anterior circulation stroke and reported hypoperfusion rates separately for TICI3 and TICI2c grades. Authors were contacted if this data was missing. We identified eight eligible articles, altogether reporting 636 patients. The incidence of IMR after complete recanalization (i.e., TICI3) tended to decrease with the number of considered alternative causes of hypoperfusion: range 12.5–42.9%, 0–31.6% and 0–9.1% in articles that considered none, two or all three causes, respectively. No study reported the impact of IMR on functional outcome separately for TICI-3 patients. Based on this systematic review, IMR in true complete recanalization appears relatively rare, and reported incidence highly depends on definition used and consideration of confounding factors. [ABSTRACT FROM AUTHOR]

Aims In chronic coronary syndrome (CCS) patients with documented coronary artery disease (CAD), ischaemia detection by myocardial perfusion imaging (MPI) and an invasive approach are viable diagnostic strategies. We compared the diagnostic performance of quantitative flow ratio (QFR) with single-photon emission computed tomography (SPECT), positron emission tomography (PET), and cardiac magnetic resonance imaging (CMR) in patients with prior CAD [previous percutaneous coronary intervention (PCI) and/or myocardial infarction (MI)]. Methods and results This PACIFIC-2 sub-study evaluated 189 CCS patients with prior CAD for inclusion. Patients underwent SPECT, PET, and CMR followed by invasive coronary angiography with fractional flow reserve (FFR) measurements of all major coronary arteries (N = 567), except for vessels with a sub-total or chronic total occlusion. Quantitative flow ratio computation was attempted in 488 (86%) vessels with measured FFR available (FFR ≤0.80 defined haemodynamically significant CAD). Quantitative flow ratio analysis was successful in 334 (68%) vessels among 166 patients and demonstrated a higher accuracy (84%) and sensitivity (72%) compared with SPECT (66%, P < 0.001 and 46%, P = 0.001), PET (65%, P < 0.001 and 58%, P = 0.032), and CMR (72%, P < 0.001 and 33%, P < 0.001). The specificity of QFR (87%) was similar to that of CMR (83%, P = 0.123) but higher than that of SPECT (71%, P < 0.001) and PET (67%, P < 0.001). Lastly, QFR exhibited a higher area under the receiver operating characteristic curve (0.89) than SPECT (0.57, P < 0.001), PET (0.66, P < 0.001), and CMR (0.60, P < 0.001). Conclusion QFR correlated better with FFR in patients with prior CAD than MPI, as reflected in the higher diagnostic performance measures for detecting FFR-defined, vessel-specific, significant CAD. [ABSTRACT FROM AUTHOR]

Aims Clinical likelihood (CL) models are designed based on a reference of coronary stenosis in patients with suspected obstructive coronary artery disease. However, a reference standard for myocardial perfusion defects (MPDs) could be more appropriate. We aimed to investigate the ability of the 2019 European Society of Cardiology pre-test probability (ESC-PTP), the risk-factor-weighted (RF-CL) model, and coronary artery calcium score-weighted (CACS-CL) model to diagnose MPDs. Methods and results Symptomatic stable de novo chest pain patients (n = 3374) underwent coronary computed tomography angiography and subsequent myocardial perfusion imaging by single-photon emission computed tomography, positron emission tomography, or cardiac magnetic resonance. For all modalities, MPD was defined as coronary computed tomography angiography with suspected stenosis and stress-perfusion abnormality in ≥2 segments. The ESC-PTP was calculated based on age, sex, and symptom typicality, and the RF-CL and CACS-CL additionally included a number of risk factors and CACS. In total, 219/3374 (6.5%) patients had an MPD. Both the RF-CL and the CACS-CL classified substantially more patients to low CL (<5%) of obstructive coronary artery disease compared with the ESC-PTP (32.5 and 54.1 vs. 12.0%, P < 0.001) with preserved low prevalences of MPD (<2% for all models). Compared with the ESC-PTP [area under the receiver-operating characteristic curve (AUC) 0.74 (0.71–0.78)], the discrimination of having an MPD was higher for the CACS-CL model [AUC 0.88 (0.86–0.91), P < 0.001], while it was similar for the RF-CL model [AUC 0.73 (0.70–0.76), P = 0.32]. Conclusion Compared with basic CL models, the RF-CL and CACS-CL models improve down classification of patients to a very low-risk group with a low prevalence of MPD. [ABSTRACT FROM AUTHOR]

Background: Pituitary apoplexy (PA) is a rare clinical condition presenting with acute headache, visual disturbance, and disorientation. PA can cause strokes due to acute internal cervical artery occlusion (ICO), which is an extremely rare condition. Arterial spin labeling (ASL) on magnetic resonance imaging (MRI) is a popular technique, which is a quantitative perfusion imaging useful for the diagnosis of ischemia. We report a treatment with acute pseudo-ICO in which ASL on MRI was useful for the decision of surgery timing. Case Description: A 50-year-old male presented with a sudden headache and nausea. MRI and magnetic resonance angiography revealed a large pituitary tumor and left ICO. However, the left middle cerebral and anterior cerebral arteries were depicted due to a cross-flow through the anterior communicating artery. ASL on MRI showed decreased perfusion of the left hemisphere, suggesting acute ICO. As he had no neurological deficit, we treated him conservatively, following the guidelines. Two days after admission, he presented with sensory aphasia and incomplete right paralysis. Emergency head computed tomography revealed a low-density area in his left temporal lobe. We decided on emergency tumor decompression surgery to prevent ischemic progression. We performed endonasal transsphenoidal surgery. Postoperative MRI showed recanalization of the left internal carotid artery (ICA). His incomplete right paralysis improved immediately after surgery but remains mild sensory aphasia. Conclusion: ICO-related PA is a very rare occasion but there are few similar reports. Some cases of successful ICO treatment due to PA have been reported, but the question of whether emergency or elective surgery is better remains unanswered. Our case may have been no neurological deficit if we had decided to have surgery on admission. Hypoperfusion of the ICA area due to PA may be an adaptation of emergency surgery. Perfusion images like ASL could be a useful technique to decide on surgery or conservative treatment. [ABSTRACT FROM AUTHOR]

Background Flow diverter (FD) devices provide a safe and effective treatment option especially for wide-necked intracranial aneurysms. One of the main concerns in patients treated with FD devices is patency of arterial branches jailed by the stent. However, there are no longterm data from magnetic resonance perfusion (MRP) studies regarding jailed branches. In this study we aimed to reveal the MRP findings in patients with jailed middle cerebral artery (MCA) cortical branches during long-term follow-up after flow diversion. Methods Patients who underwent FD stent treatment for MCA aneurysms with a resulting jailed cortical branch were included. Follow-up clinical, angiographic, and MRP examination findings were recorded. Different MRP parameters were measured in the MCA territory regarding the jailed branches. Results Eighteen patients treated endovascularly with flow diversion for a total of 20 MCA aneurysms were included. At angiographic follow-up (median 35 months, range 7-95 months) complete occlusion was observed in 13 (65%) aneurysms and partial occlusion was observed in 6 (30%). The mean transit time (MTT) prolongation, MTT ratio, time-to peak (TTP) prolongation, and TTP ratio were 1.34, 1.20, 1.18, and 1.06 s, respectively, when compared with the contralateral side in the MCA territory. MTT, TTP, and cerebral blood volume values of the patients showed statistically significant differences compared with the contralateral side (P<0.05). Conclusions Flow diversion treatment of complex bifurcation aneurysms can be effective and safe. MRP examination may reveal perfusion changes in the territory vascularized via a jailed branch, and these changes are rarely accompanied by clinical findings. [ABSTRACT FROM AUTHOR]

Objective: We aimed to investigate to usability and feasibility of perfusion computerized tomography (PCT) in differentiating small cell lung cancer (SCLC) from non-small cell lung cancer (NSCLC). Methods: Between September 2013 and February 2022, 42 patients with a detected lung mass took part in the present study. All patients went through PCT examination, and data regarding permeability (PMB), blood flow (BF), and blood volume (BV) of the tumor were acquired. These parameters along with mass diameter of the tumors were compared in both cancer types. Results: Maximum tumor diameter was measured as 48 ± 11 mm in average in the SCLC cases and 49 ± 15 mm in the NSCLC cases (P = .892). There was a correlation at a moderate level between the tumor's maximal diameter and PMB (r = .49, P = .020). Regarding tumor PMB values, there was a meaningful variation between the 2 tumor groups (SCLC: 16.4 ± 3.6 mL/100 mL/min; NSCLC: 5.1 ± 2.8 mL/100 mL/min; P = .001). No further meaningful differences were observed among the BF- and BV-related comparisons. Conclusion: Among the perfusion parameters in lung PCT, PMB can be used to distinguish the NSCLC from SCLC in patients who were diagnosed with lung cancer. [ABSTRACT FROM AUTHOR]

Purpose: Dynamic chest radiography (DCR) is a novel imaging technique used to noninvasively evaluate pulmonary perfusion. However, the standard DCR protocol, which is roughly adapted to the patient's body size, occasionally causes over‐ or underexposure, which could influence clinical evaluation. Therefore, we proposed a refined protocol by increasing the number of patient body mass index (BMI) categories from three to seven groups and verified its usefulness by comparing the image sensitivity indicators (S‐values) and entrance surface doses (ESDs) of the conventional protocol with those of our refined protocol. Methods: This retrospective observational study included 388 datasets (standing position, 224; supine position, 164) for the conventional protocol (December 2019–April 2021) and 336 datasets (standing position, 233; supine position, 103) for the refined protocol (June–November 2021). The conventional protocol (BMI‐3 protocol) divided the patients into three BMI groups (BMI < 17, 17≤BMI < 25, and BMI ≥ 25 kg/m2), whereas the refined protocol (BMI‐7 protocol) divided the patients into seven BMI groups (BMI < 17, 17 ≤ BMI < 20, 20 ≤ BMI < 23, 23 ≤ BMI < 26, 26 ≤ BMI < 29, 29 ≤ BMI < 32, and BMI ≥ 32 kg/m2). The coefficients of variation (CVs) for the S‐values and ESDs acquired using the two protocols were compared. Results: The CVs of the S‐values in the BMI‐7 protocol group were significantly lower than those in the BMI‐3 protocol group for the standing (28.8% vs. 16.7%; p < 0.01) and supine (24.5% vs. 17.7%; p < 0.01) positions. The ESDs of patients scanned using the BMI‐7 protocol were significantly lower than those scanned using the BMI‐3 protocol in the standing (1.3 vs. 1.1 mGy; p < 0.01) and supine positions (2.5 vs. 1.6 mGy; p < 0.01), although the mean BMI of the two groups were similar. Conclusion: We introduced the BMI‐7 protocol and demonstrated its standardized image quality and reduced radiation exposure in patients undergoing DCR. [ABSTRACT FROM AUTHOR]

A critical need exists for early, accurate diagnosis of burn wound severity to help identify the course of treatment and outcome of the wound. Laser speckle imaging (LSI) is a promising blood perfusion imaging approach, but it does not account for changes in tissue optical properties that can occur with burn wounds, which are highly dynamic environments. Here, we studied optical property dynamics following burn injury and debridement and the associated impact on interpretation of LSI measurements of skin perfusion. We used spatial frequency domain imaging (SFDI) measurements of tissue optical properties to study the impact of burn-induced changes in these properties on LSI measurements. An established preclinical porcine model of burn injury was used (n = 8). SFDI and LSI data were collected from burn wounds of varying severity. SFDI measurements demonstrate that optical properties change in response to burn injury in a porcine model. We then apply theoretical modeling to demonstrate that the measured range of optical property changes can affect the interpretation of LSI measurements of blood flow, but this effect is minimal for most of the measured data. Collectively, our results indicate that, even with a dynamic burn wound environment, blood-flow measurements with LSI can serve as an appropriate strategy for accurate assessment of burn severity.

Background: The intravoxel incoherent motion (IVIM) model extracts both functional and structural information of a tissue using motion-sensitizing gradients.Objective: The Objective of the present work is to investigate the impact of signal to noise ratio (SNR) and physiologic conditions on the validity of IVIM parameters.Material and Methods: This study is a simulation study, modeling IVIM at a voxel, and also done 10,000 times for every single simulation. Complex noises with various standard deviations were added to signal in-silico to investigate SNR effects on output validity. Besides, some blood perfusion situations for different tissues were considered based on their physiological range to explore the impacts of blood fraction at each voxel on the validity of the IVIM outputs. Coefficient variation (CV) and bias of the estimations were computed to assess the validity of the IVIM parameters.Results: This study has shown that the validity of IVIM output parameters highly depends on measurement SNR and physiologic characteristics of the studied organ. Conclusion: IVIM imaging could be useful if imaging parameters are correctly selected for each specific organ, considering hardware limitations.

Abstract Background The effectiveness of surgical interventions, whether direct or indirect, for Moyamoya disease (MMD) remains controversial. This study aims to investigate CT perfusion (CTP) as an objective method to evaluate the outcomes of different surgical modalities for adult MMD. Methods The clinical and imaging data of 41 patients who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass and 43 who received encephaloduroarteriosynangiosis (EDAS) were retrospectively analyzed. Intra- and intergroup differences in the Modified Rankin Scale (mRS) score, the change in clinical symptoms, collateral grade, and CTP parameters pre- and postoperatively were compared. Results The overall level of the change in clinical symptoms in the STA-MCA group was higher than in the EDAS group (p

PurposeThe combined hyperpolarized (HP) 13 C pyruvate and urea MRI has provided a simultaneous assessment of glycolytic metabolism and tissue perfusion for improved cancer diagnosis and therapeutic evaluation in preclinical studies. This work aims to translate this dual-probe HP imaging technique to clinical research.MethodsA co-polarization system was developed where [1-13 C]pyruvic acid (PA) and [13 C, 15 N2 ]urea in water solution were homogeneously mixed and polarized on a 5T SPINlab system. Physical and chemical characterizations and toxicology studies of the combined probe were performed. Simultaneous metabolic and perfusion imaging was performed on a 3T clinical MR scanner by alternatively applying a multi-slice 2D spiral sequence for [1-13 C]pyruvate and its downstream metabolites and a 3D balanced steady-state free precession (bSSFP) sequence for [13 C, 15 N2 ]urea.ResultsThe combined PA/urea probe has a glass-formation ability similar to neat PA and can generate nearly 40% liquid-state 13 C polarization for both pyruvate and urea in 3-4 h. A standard operating procedure for routine on-site production was developed and validated to produce 40 mL injection product of approximately 150 mM pyruvate and 35 mM urea. The toxicology study demonstrated the safety profile of the combined probe. Dynamic metabolite-specific imaging of [1-13 C]pyruvate, [1-13 C]lactate, [1-13 C]alanine, and [13 C, 15 N2 ]urea was achieved with adequate spatial (2.6 mm × 2.6 mm) and temporal resolution (4.2 s), and urea images showed reduced off-resonance artifacts due to the JCN coupling.ConclusionThe reported technical development and translational studies will lead to the first-in-human dual-agent HP MRI study and mark the clinical translation of the first HP 13 C MRI probe after pyruvate.

The article discusses the road to the ISMRM OSIPI, a community-led initiative aimed at improving the reproducibility and harmonization of perfusion MRI. The initiative was launched in response to a survey sent out to members of the ISMRM Perfusion Study Group, which received strong interest and support from participants. The article outlines the mission and governance structure of OSIPI, as well as its specific aims and task forces. The results of the first roadmap are also shared, highlighting the resources produced by the initiative. With over 75 contributing volunteers, OSIPI is positioned to serve as a centralized platform for perfusion resources for researchers and clinicians. [Extracted from the article]

Acute ischemic stroke patients benefit from reperfusion in a short time-window after debut. Later treatment may be indicated if viable brain tissue is demonstrated and this outweighs the inherent risks of late reperfusion. Magnetic resonance imaging (MRI) with hyperpolarized [1-13C]pyruvate is an emerging technology that directly images metabolism. Here, we investigated its potential to detect viable tissue in ischemic stroke. Stroke was induced in pigs by intracerebral injection of endothelin 1. During ischemia, the rate constant of pyruvate-to-lactate conversion, kPL, was 52% larger in penumbra and 85% larger in the infarct compared to the contralateral hemisphere (P = 0.0001). Within the penumbra, the kPL was 50% higher in the regions that later infarcted compared to non-progressing regions (P = 0.026). After reperfusion, measures of pyruvate-to-lactate conversion were slightly decreased in the infarct compared to contralateral. In addition to metabolic imaging, we used hyperpolarized pyruvate for perfusion-weighted imaging. This was consistent with conventional imaging for assessment of infarct size and blood flow. Lastly, we confirmed the translatability of simultaneous assessment of metabolism and perfusion with hyperpolarized MRI in healthy volunteers. In conclusion, hyperpolarized [1-13C]pyruvate may aid penumbral characterization and increase access to reperfusion therapy for late presenting patients.

Abstract Critical limb ischemia is associated with high mortality and major amputations. Intra-arterial digital subtraction angiography (IADSA) has been the reference standard but has some shortcomings including the two-dimensional projection and the lack of tissue perfusion information. The aim of this exploratory study is to examine four-dimensional computed tomography (4DCT) angiography and perfusion imaging using low-volume intra-arterial contrast injections for an improved anatomic and hemodynamic assessment in patients with foot ulcers. Three patients underwent a low-volume (2 mL) intra-arterial contrast-enhanced 4DCT examination combined with a diagnostic IADSA. An automated assessment of blood flow and tissue perfusion from the 4DCT data was performed. Vascular structures and corresponding blood flows were successfully assessed and correlated well with the IADSA results. Perfusion values of the affected tissue were significantly higher compared to the unaffected tissue. The proposed 4DCT protocol combined with the minimal usage of contrast agent (2 mL) provides superior images compared to IADSA as three phases (arterial, perfusion, and venous) are captured. The obtained parameters could allow for an improved diagnosis of critical limb ischemia as both the proximal vasculature and the extent of the perfusion deficit in the microvasculature can be assessed. Relevance statement Intra-arterial 4DCT allows for assessing three phases (arterial, perfusion and venous) using minimal contrast (2 mL). This method could lead to an improved diagnosis of critical limb ischemia as both proximal vasculature and the extent of the perfusion deficit are assessed. Trial registration ISRCTN, ISRCTN95737449. Registered 14 March 2023—retrospectively registered, https://www.isrctn.com/ISRCTN95737449 Key points • Three phases (arterial, perfusion, and venous) are obtained from 2 mL intra-arterial 4DCT. • The obtained hemodynamic parameters correlated well with the IADSA findings. • 4DCT surpassed IADSA in terms of assessment of venous blood flow and inflammatory hyperperfusion. • The assessment of tissue perfusion could lead to optimizing the revascularization strategy. Graphical Abstract

Abstract Background This study provides a quantitative meta-analysis of pancreatic CT perfusion studies, investigating choice of study parameters, ability for quantitative discrimination of pancreatic diseases, and influence of acquisition and reconstruction parameters on reported results. Methods Based on a PubMed search with key terms ‘pancreas’ or ‘pancreatic,’ ‘dynamic’ or ‘perfusion,’ and ‘computed tomography’ or ‘CT,’ 491 articles published between 1982 and 2020 were screened for inclusion in the study. Inclusion criteria were: reported original data, human subjects, five or more datasets, measurements of pancreas or pancreatic pathologies, and reported quantitative perfusion parameters. Study parameters and reported quantitative measurements were extracted, and heterogeneity of study parameters and trends over time are analyzed. Pooled data were tested with weighted ANOVA and ANCOVA models for differences in perfusion results between normal pancreas, pancreatitis, PDAC (pancreatic ductal adenocarcinoma), and non-PDAC (e.g., neuroendocrine tumors, insulinomas) and based on study parameters. Results Reported acquisition parameters were heterogeneous, except for contrast agent amount and injection rate. Tube potential and slice thickness decreased, whereas tube current time product and scan coverage increased over time. Blood flow and blood volume showed significant differences between pathologies (both p

Background Perfusion deficits contribute to symptom severity, morbidity, and death in peripheral artery disease (PAD); however, no standard method for quantifying absolute measures of skeletal muscle perfusion exists. This study sought to preclinically test and clinically translate a positron emission tomography (PET) imaging approach using an atherosclerosis‐targeted radionuclide, fluorine‐18‐sodium fluoride (18F‐NaF), to quantify absolute perfusion in PAD. Methods and Results Eight Yorkshire pigs underwent unilateral femoral artery ligation and dynamic 18F‐NaF PET/computed tomography imaging on the day of and 2 weeks after occlusion. Following 2‐week imaging, calf muscles were harvested to quantify microvascular density. PET methodology was validated with microspheres in 4 additional pig studies and translated to patients with PAD (n=39) to quantify differences in calf perfusion across clinical symptoms/stages and perfusion responses in a case of revascularization. Associations between PET perfusion, ankle‐brachial index, toe‐brachial index, and toe pressure were assessed in relation to symptoms. 18F‐NaF PET/computed tomography quantified significant deficits in calf perfusion in pigs following arterial occlusion and perfusion recovery 2 weeks after occlusion that coincided with increased muscle microvascular density. Additional studies confirmed that PET‐derived perfusion measures agreed with microsphere‐derived perfusion measures. Translation of imaging methods demonstrated significant decreases in calf perfusion with increasing severity of PAD and quantified perfusion responses to revascularization. Perfusion measures were also significantly associated with symptom severity, whereas traditional hemodynamic measures were not. Conclusions 18F‐NaF PET imaging quantifies perfusion deficits that correspond to clinical stages of PAD and represents a novel perfusion imaging strategy that could be partnered with atherosclerosis‐targeted 18F‐NaF PET imaging using a single radioisotope injection. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03622359.

Stereotactic radiosurgery is an established focal treatment for brain metastases with high local control rates. An important side-effect of stereotactic radiosurgery is the development of radionecrosis. On conventional MR imaging, radionecrosis and tumour progression often have similar appearances, but have contrasting management approaches. Perfusion MR imaging is often used in the post-treatment setting in order to help distinguish between the two, but image interpretation can be fraught with challenges. Perfusion MR plays an established role in the baseline and post-treatment evaluation of primary brain tumours and a number of studies have concentrated on the value of perfusion imaging in brain metastases. Of the parameters generated, relative cerebral blood volume is the most widely used variable in terms of its clinical value in differentiating between radionecrosis and tumour progression. Although it has been suggested that the relative cerebral blood volume tends to be elevated in active metastatic disease following treatment with radiosurgery, but not with treatmentrelated changes, the literature available on interpretation of the ratios provided in the context of defining tumour progression is not consistent. This article aims to provide an overview of the role perfusion MRI plays in the assessment of brain metastases and introduces the rationale for the STARBEAM-X study (Study of assessment of radionecrosis in brain metastases using MR perfusion extra imaging), which will prospectively evaluate baseline perfusion imaging in brain metastases. We hope this will allow insight into the vascular appearance of metastases from different primary sites, and aid in the interpretation of post-treatment perfusion imaging. [ABSTRACT FROM AUTHOR]

Background: Single photon emission tomography (SPECT) can detect early changes in brain perfusion to support the diagnosis of dementia. Inflammation is a driver for dementia progression and measures of inflammation may further support dementia diagnosis. Objective: In this study, we assessed whether combining imaging with markers of inflammation improves prediction of the likelihood of Alzheimer's disease (AD). Methods: We analyzed 91 participants datasets (Institutional Ethics Approval 20/NW/0222). AD biomarkers and markers of inflammation were measured in cerebrospinal fluid. Statistical parametric mapping was used to quantify brain perfusion differences in perfusion SPECT images. Logistic regression models were trained to evaluate the ability of imaging and inflammation markers, both individually and combined, to predict AD. Results: Regional perfusion reduction in the precuneus and medial temporal regions predicted Aβ42 status. Increase in inflammation markers predicted tau and neurodegeneration. Matrix metalloproteneinase-10, a marker of blood-brain barrier regulation, was associated with perfusion reduction in the right temporal lobe. Adenosine deaminase, an enzyme involved in sleep homeostasis and inflammation, was the strongest predictor of neurodegeneration with an odds ratio of 10.3. The area under the receiver operator characteristic curve for the logistic regression model was 0.76 for imaging and 0.76 for inflammation. Combining inflammation and imaging markers yielded an area under the curve of 0.85. Conclusions: Study results showed that markers of brain perfusion imaging and markers of inflammation provide complementary information in AD evaluation. Inflammation markers better predict tau status while perfusion imaging measures represent amyloid status. Combining imaging and inflammation improves AD prediction. [ABSTRACT FROM AUTHOR]

Background and aims: Although treatment of ischemia-causing epicardial stenoses may improve symptoms of ischemia, current evidence does not suggest that revascularization improves survival. Conventional myocardial ischemia imaging does not uniquely identify diffuse atherosclerosis, microvascular dysfunction, or nonobstructive epicardial stenoses. We sought to evaluate the prognostic value of integrated myocardial flow reserve (iMFR), a novel noninvasive approach to distinguish the perfusion impact of focal atherosclerosis from diffuse coronary disease. Methods: This study analyzed a large single-center registry of consecutive patients clinically referred for rest-stress myocardial perfusion positron emission tomography. Cox proportional hazards modeling was used to assess the association of two previously reported and two novel perfusion measures with mortality risk: global stress myocardial blood flow (MBF); global myocardial flow reserve (MFR); and two metrics derived from iMFR analysis: the extents of focal and diffusely impaired perfusion. Results: In total, 6867 patients were included with a median follow-up of 3.4 years [1st–3rd quartiles, 1.9–5.0] and 1444 deaths (21%). Although all evaluated perfusion measures were independently associated with death, diffusely impaired perfusion extent (hazard ratio 2.65, 95%C.I. [2.37–2.97]) and global MFR (HR 2.29, 95%C.I. [2.08–2.52]) were consistently stronger predictors than stress MBF (HR 1.62, 95%C.I. [1.46–1.79]). Focally impaired perfusion extent (HR 1.09, 95%C.I. [1.03–1.16]) was only moderately related to mortality. Diffusely impaired perfusion extent remained a significant independent predictor of death when combined with global MFR (p < 0.0001), providing improved risk stratification (overall net reclassification improvement 0.246, 95%C.I. [0.183–0.310]). Conclusions: The extent of diffusely impaired perfusion is a strong independent and additive marker of mortality risk beyond traditional risk factors, standard perfusion imaging, and global MFR, while focally impaired perfusion is only moderately related to mortality. [ABSTRACT FROM AUTHOR]

Background: The main application of [18F] FDG‐PET (18FDG‐PET) and CT images in oncology is tumor identification and quantification. Combining PET and CT images to mine pulmonary perfusion information for functional lung avoidance radiation therapy (FLART) is desirable but remains challenging. Purpose: To develop a deep‐learning‐based (DL) method to combine 18FDG‐PET and CT images for producing pulmonary perfusion images (PPI). Methods: Pulmonary technetium‐99 m‐labeled macroaggregated albumin SPECT (PPISPECT), 18FDG‐PET, and CT images obtained from 53 patients were enrolled. CT and PPISPECT images were rigidly registered, and registration displacement was subsequently used to align 18FDG‐PET and PPISPECT images. The left/right lung was separated and rigidly registered again to improve the registration accuracy. A DL model based on 3D Unet architecture was constructed to directly combine multi‐modality 18FDG‐PET and CT images for producing PPI (PPIDLM). 3D Unet architecture was used as the basic architecture, and the input was expanded from a single‐channel to a dual‐channel to combine multi‐modality images. For comparative evaluation, 18FDG‐PET images were also used alone to generate PPIDLPET. Sixty‐seven samples were randomly selected for training and cross‐validation, and 36 were used for testing. The Spearman correlation coefficient (rs) and multi‐scale structural similarity index measure (MS‐SSIM) between PPIDLM/PPIDLPET and PPISPECT were computed to assess the statistical and perceptual image similarities. The Dice similarity coefficient (DSC) was calculated to determine the similarity between high‐/low‐ functional lung (HFL/LFL) volumes. Results: The voxel‐wise rs and MS‐SSIM of PPIDLM/PPIDLPET were 0.78 ± 0.04/0.57 ± 0.03, 0.93 ± 0.01/0.89 ± 0.01 for cross‐validation and 0.78 ± 0.11/0.55 ± 0.18, 0.93 ± 0.03/0.90 ± 0.04 for testing. PPIDLM/PPIDLPET achieved averaged DSC values of 0.78 ± 0.03/0.64 ± 0.02 for HFL and 0.83 ± 0.01/0.72 ± 0.03 for LFL in the training dataset and 0.77 ± 0.11/0.64 ± 0.12, 0.82 ± 0.05/0.72 ± 0.06 in the testing dataset. PPIDLM yielded a stronger correlation and higher MS‐SSIM with PPISPECT than PPIDLPET (p < 0.001). Conclusions: The DL‐based method integrates lung metabolic and anatomy information for producing PPI and significantly improved the accuracy over methods based on metabolic information alone. The generated PPIDLM can be applied for pulmonary perfusion volume segmentation, which is potentially beneficial for FLART treatment plan optimization. [ABSTRACT FROM AUTHOR]

A 58-year-old patient presented with a severe neurological deficit due to a stroke caused by an occlusion of the left internal carotid artery siphon. Standard treatment failed and neurosurgical consult was delayed. Because of a favorable perfusion imaging finding, microsurgical revascularization via an extra-intracranial bypass (left superficial temporal artery — left middle cerebral artery) was performed 36 hours after the onset of the symptoms. The outcome of the patient was favorable. The authors want to emphasize the need to actively seek patients with a severe neurological deficit and still viable brain tissue. The time window and treatment alternatives are discussed. [ABSTRACT FROM AUTHOR]

To explore the possibility of using a novel technique, CT perfusion imaging, to monitor the response to anti-tubercular therapy (ATT) in patients with intestinal tuberculosis. A prospective observational study was performed in adults with treatment naive-intestinal tuberculosis. Clinical, endoscopic, and conventional radiological findings of patients were compared at baseline and post-ATT. CT perfusion imaging was performed with recording of six perfusion parameters (blood flow, blood volume, mean transit time, time to peak, maximum peak intensity, and permeability/blood flow extraction). Twenty-two patients (13 women, 59%) with a median age of 25 years were recruited. The terminal ileum and ileocaecal junction were the most frequent sites of involvement (59%), with multiple segments of the intestine being involved in 16 patients (73%). Median duration of ATT was 6 months (range 6–10 months). Complete clinical response was observed in 22/22 (100%) patients, endoscopic response in 12/12 (100%) patients, and radiological response in 10/13 (76%) patients. There was a significant decrease in mean blood flow, blood volume, maximum peak intensity, and an increase in mean transit time and time to peak on follow-up CT perfusion imaging performed after 6 months of ATT. Significant alterations in CT perfusion parameters were demonstrated following treatment, consistent with a decline in inflammation and vascularity. CT perfusion imaging of the bowel is a novel means to assess the radiological response to ATT in intestinal tuberculosis, although at the cost of a higher dose of radiation exposure. • Treatment endpoints for intestinal tuberculosis are controversial. • Radiological resolution lags behind clinical; routine CT scan insufficient. • CT perfusion imaging measures vascularity of inflamed bowel segments and nodes. • Treatments leads to reduced CT parameters of blood flow and time to peak intensity. • Remains to be seen if this can help decision to stop therapy, and utility vs. PET-CT. [ABSTRACT FROM AUTHOR]

To evaluate different approaches for the effective assessment of pulmonary perfusion with a pseudo-continuous arterial spin labeled (pCASL) MRI. Four different approaches were evaluated: 1) Cardiac-triggered inferior vena cava (IVC) labeling; 2) IVC labeling with cardiac-triggered acquisition; 3) Right pulmonary artery (RPA) labeling with cardiac-triggered acquisition; and 4) Cardiac-triggered RPA labeling with background suppression (BGS). Each approach was evaluated in 5 healthy volunteers (n = 20) using coefficient of variation (COV) across averages. Approach 4 was also compared against a flow alternating inversion recovery (FAIR). The IVC labeling (Approach 1) achieved perfusion-weighted images of both lungs, although this approach was more sensitive to variations in heart rate. Cardiac-triggered acquisitions using IVC (Approach 2) and RPA (Approach 3) labeling improved signal consistencies, but were incompatible with BGS. The cardiac-triggered RPA labeling with BGS (Approach 4) achieved a COV of 0.34 ± 0.03 (p < 0.05 compared to IVC labeling approaches) and resulted in perfusion value of 434 ± 64 mL/100 g/min, which was comparable to 451 ± 181 mL/100 g/min measured by FAIR (p = 0.82). Pulmonary perfusion imaging using pCASL-MRI is highly sensitive to cardiac phase, and requires approaches to minimize flow-induced signal variations. Cardiac-triggered RPA labeling with BGS achieves reduced COV and enables robust pulmonary perfusion imaging. [ABSTRACT FROM AUTHOR]

The aging population challenges the health-care system with chronic diseases. Cerebrovascular diseases are important components of these chronic conditions. Stroke is the acute cessation of blood in the brain, which can lead to rapid tissue loss. Therefore, fast, accurate, and reliable automatic methods are required to facilitate stroke management. The performance of artificial intelligence (AI) methods is increasing in all domains. Vision tasks, including natural images and medical images, are particularly benefiting from the skills of AI models. The AI methods that can be applied to stroke imaging have a broad range, including classical machine learning tools such as support vector machines, random forests, logistic regression, and linear discriminant analysis, as well as deep learning models, such as convolutional neural networks, recurrent neural networks, autoencoders, and U-Net. Both tools can be applied to various aspects of stroke management, including time-to-event onset determination, stroke confirmation, large vessel occlusion detection, diffusion restriction, perfusion deficit, core and penumbra identification, affected region segmentation, and functional outcome prediction. While building these AI models, maximum care should be exercised in order to reduce bias and build generalizable models. One of the most important prerequisites for building unbiased models is collecting large, diverse, and quality data that reflects the underlying population well and splitting the training and testing parts in a way that both represent a similar distribution. Explainability and trustworthiness are other important properties of machine learning models that could be widely adopted in clinical practices. [ABSTRACT FROM AUTHOR]

Objective: Dynamic BOLD MRI with cuff compression, inducing ischemia and post-occlusive hyperemia in skeletal muscle, has been pointed out as a potential diagnostic tool to assess peripheral limb perfusion. The objective was to explore the robustness of this technique and its sensitivity to the occlusion duration. Materials and methods: BOLD images were acquired at 3 T in 14 healthy volunteers. T 2 ∗ -imaging with 5- and 1.5-min occlusions were acquired and several semi-quantitative BOLD parameters were derived from ROI-based T 2 ∗ -time curves. Differences in parameters from the two different occlusion durations were evaluated in the gastrocnemius and soleus muscles using non-parametrical tests. Intra- and inter-scan repeatability were evaluated with coefficient of variation. Results: Longer occlusion duration resulted in an increased hyperemic signal effect yielding significantly different values (p < 0.05) in gastrocnemius for all parameters describing the hyperemic response, and in soleus for two of these parameters. Specifically, 5-min occlusion yielded steeper hyperemic upslope in gastrocnemius (41.0%; p < 0.05) and soleus (59.7%; p = 0.03), shorter time to half peak in gastrocnemius (46.9%; p = 0.00008) and soleus (33.5%; p = 0.0003), and shorter time to peak in gastrocnemius (13.5%; p = 0.02). Coefficients of variation were lower than percentage differences that were found significant. Discussion: Findings show that the occlusion duration indeed influences the hyperemic response and thus should play a part in future methodological developments. [ABSTRACT FROM AUTHOR]

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Stroke is characterised as a cerebrovascular disease, which acts as the key factor of mortality and permanent disabilities. Ischaemic stroke is observed as a widespread stroke that results in tissue hypoxia. Hence, it is crucial to analyse the ischaemic stroke lesions for the accurate identification of the stroke in intensive care units. However, the recognition of ischaemic lesions is a difficult process due to their small resolution and poor image resolution. Various schemes have been suggested for stroke lesion identification, localisation, and detection, finding infarct cores and penumbras is of high interest. Artificial intelligence could be one of the promising technologies in all methods, which may accelerate stroke analysis and lead to improved patient recovery. This article provides a review of different articles related to ischaemic lesion deduction using Computed Tomography (CT) and CT perfusion imaging. This review article thus provides insight into methods, performance measures, and the key highlight of these models. Further, this review article provides the challenges encountered in the existing techniques. [ABSTRACT FROM AUTHOR]

Background: Splenic switch-off (SSO) is a marker of adequate adenosine-induced vasodilatation on cardiac magnetic resonance perfusion imaging. We evaluate the feasibility of quantitative assessment of SSO in myocardial positron emission tomography (PET) perfusion imaging using [15O]H2O. Methods: Thirty patients underwent [15O]H2O PET perfusion with adenosine stress. Time-activity curves, as averaged standardized uptake values (SUVavg), were extracted from dynamic PET for spleen and liver. Maximum SUVavg, stress and rest spleen-to-liver ratio (SLR), and the splenic activity concentration ratio (SAR) were computed. Optimal cut-off values for SSO assessment were estimated from receiver operating characteristics (ROC) curve for maximum SUVavg and SLR. Also, differences between coronary artery disease, myocardial ischemia, beta-blockers, and diabetes were assessed. Data are presented as median [interquartile range]. Results: In concordance with the SSO phenomenon, both the spleen maximum SUVavg and SLR were lower in adenosine stress when compared to rest perfusion (8.1 [6.5, 9.2] versus 16.4 [13.4, 19.0], p < 0.001) and (0.81 [0.63, 1.08] versus 1.86 [1.73, 2.06], p < 0.001), respectively. During adenosine stress, the SSO effect was most prominent 40–160 s after radiotracer injection. Cut-off values of 12.6 and 1.57 for maximum SUVavg and SLR, respectively, were found based on ROC analysis. No differences in SAR, SLRRest, or SLRStress were observed in patients with coronary artery disease, myocardial ischemia, or diabetes. Conclusions: SSO can be quantified from [15O]H2O PET perfusion and used as a marker for adequate adenosine-induced vasodilatation response. In contrary to other PET perfusion tracers, adenosine-induced SSO is time dependent with [15O]H2O. [ABSTRACT FROM AUTHOR]

Background: The effectiveness of surgical interventions, whether direct or indirect, for Moyamoya disease (MMD) remains controversial. This study aims to investigate CT perfusion (CTP) as an objective method to evaluate the outcomes of different surgical modalities for adult MMD. Methods: The clinical and imaging data of 41 patients who underwent superficial temporal artery-middle cerebral artery (STA-MCA) bypass and 43 who received encephaloduroarteriosynangiosis (EDAS) were retrospectively analyzed. Intra- and intergroup differences in the Modified Rankin Scale (mRS) score, the change in clinical symptoms, collateral grade, and CTP parameters pre- and postoperatively were compared. Results: The overall level of the change in clinical symptoms in the STA-MCA group was higher than in the EDAS group (p < 0.05). In the operative area, the relative cerebral blood flow (rCBF) was significantly higher whereas the relative time to peak (rTTP) and the relative mean transit time (rMTT) were significantly lower in the STA-MCA and EDAS groups postoperatively than preoperatively (all p < 0.05). In the ipsilateral frontal lobe and basal ganglia, the postoperative rCBF was significantly higher, and the rTTP was significantly lower than the preoperative in the STA-MCA group (all p < 0.05). The postoperative rCBF improvement was higher in each brain area for STA-MCA than in the EDAS group (all p < 0.05). Conclusion: Highlighting the utility of CTP, this study demonstrates its effectiveness in assessing postoperative cerebral hemodynamic changes in adult MMD patients. STA-MCA yielded a larger postoperative perfusion area and greater improvement compared to EDAS, suggesting CTP's potential to elucidate symptom variation between two surgical revascularization procedures. Critical relevance statement: We analyzed computed tomography perfusion parameters in pre- and postoperative adult Moyamoya disease patients undergoing superficial temporal artery-middle cerebral artery bypass and encephaloduroarteriosynangiosis. Our findings suggest computed tomography perfusion's potential in objectively elucidating symptom variations between these surgical revascularization approaches for MMD. Key points: • Postoperative perfusion improvement is only confined to the operative area after EDAS. • Besides the operative area, postoperative perfusion in the ipsilateral frontal lobe and basal ganglia was also improved after STA-MCA. • The degree of perfusion improvement in each brain area in the STA-MCA group was generally greater than that in the EDAS group. [ABSTRACT FROM AUTHOR]

Background and Purpose: To assess the feasibility of 3‐dimensional stereotactic surface projection (3D‐SSP) as applied to arterial spin labeling (ASL) in a clinical pilot study. Methods: A retrospective sample of 10 consecutive patients who underwent ASL as part of a clinically indicated MR examination was collected during this pilot study. Five additional subjects with normal cerebral perfusion served as a control group. Following voxel‐wise M0‐correction, cerebral blood flow (CBF) quantification, and stereotactic anatomic standardization, voxel‐wise CBF from an individual's ASL dataset was extracted to a set of predefined surface pixels (3D‐SSP). A normal database was created from averaging the extracted CBF datasets of the control group. Patients' datasets were compared individually with the normal database by calculating a Z‐score on a pixel‐by‐pixel basis and were displayed in 3D‐SSP views for visual inspection. Independent, two‐expert reader assessment, using a 3‐point scale, compared standard quantitative CBF images to the 3D‐SSP maps. Results: Patterns and severities of regionally reduced CBF were identified, by both independent readers, in the 3D‐SSP maps. Reader assessment demonstrated preference for 3D‐SSP over traditionally displayed standard quantitative CBF images in three of four evaluated imaging metrics (p =.026,.031, and.013, respectively); 3D‐SSP maps were never found to be inferior to the standard quantitative CBF images. Conclusions: Three‐dimensional SSP maps are feasible in a clinical population and enable quantitative data extraction and localization of perfusion abnormalities by means of stereotactic coordinates in a condensed display. The proposed method is a promising approach for interpreting cerebrovascular pathophysiology. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate morphologic perfusion patterns in transition zone prostate cancer in multiparametric MRI controlled by in-bore MRI-guided prostate biopsy. Methods: Two experienced radiologists evaluated MRI perfusion patterns in consensus from 321 biopsy cores from the transition zone in 141 patients. Transition zone cancer was present in 77 cores in 36 patients. Single early-phase perfusion images were evaluated separately for the presence of a transition zone prostate cancer (consensus tumor early perfusion). The proposed criteria for the perfusion pattern (asymmetry, signal strength, and homogeneity) were rated in consensus for each biopsy position in the presence of the T2w images including the markers of the biopsy trace. We analyzed receiver operating characteristic curves for the PI-RADSv2.1 score and the proposed perfusion pattern. Results: A logistic regression model with PI-RADSv2.1 and perfusion patterns in early perfusion imaging improved the model fit significantly compared to a model containing only PI-RADSv2.1 (Likelihood Ratio Test, LR = 14.5, p <.001). The AUC was 0.96 for the multiple regression model compared to 0.92 for the PI-RADSv2.1 alone. The evaluation of homogeneity in single early-enhancement images is not inferior compared to the conventional DCE parameter of PI-RADSv2.1 (AUC 0.84 versus 0.83). Conclusion: Morphologic perfusion patterns significantly improve the diagnostic performance of PI-RADSv2.1 in TZ prostate cancer. [ABSTRACT FROM AUTHOR]

Purpose: The clinical condition of a brain abscess is a potentially life-threatening disease. The combination of MRI-based imaging, surgical therapy and microbiological analysis is critical for the treatment and convalescence of the individual patient. The aim of this study was to evaluate brain tissue oxygenation measured with dynamic susceptibility contrast perfusion weighted imaging (DSC-PWI) in patients with brain abscess and its potential benefit for a better understanding of the environment in and around brain abscesses. Methods: Using a local database, 34 patients (with 45 abscesses) with brain abscesses treated between January 2013 and March 2021 were retrospectively included in this study. DSC-PWI imaging and microbiological work-up were key inclusion criteria. These data were analysed regarding a correlation between DSC-PWI and microbiological result by quantifying brain tissue oxygenation in the abscess itself, the abscess capsula and the surrounding oedema and by using six different parameters (CBF, CBV, CMRO2, COV, CTH and OEF). Results: Relative cerebral blood flow (0.335 [0.18–0.613] vs. 0.81 [0.49–1.08], p = 0.015), relative cerebral blood volume (0.44 [0.203–0.72] vs. 0.87 [0.67–1.2], p = 0.018) and regional cerebral metabolic rate for oxygen (0.37 [0.208–0.695] vs. 0.82 [0.55–1.19], p = 0.022) were significantly lower in the oedema around abscesses without microbiological evidence of a specific bacteria in comparison with microbiological positive lesions. Conclusions: The results of this study indicate a relationship between brain tissue oxygenation status in DSC-PWI and microbiological/inflammatory status. These results may help to better understand the in vivo environment of brain abscesses and support future therapeutic decisions. [ABSTRACT FROM AUTHOR]

Background: A liver space-occupying lesion is a benign tumour that has grown to occupy a significant amount of the liver's normal tissue. Lesions that occupy space in the liver can be classified as either developmental, neoplastic, inflammatory, or other. Currently, there is no consensus on the optimal method for imaging the liver to identify these types of space-occupying lesions. Material and Methods: Following approval from our institution's ethical committee, we conducted this prospective study in accordance with our institution's informed consent criteria. 40 participants were analysed in a study conducted at the department of Radiodiagnosis, NRI Medical College & Hospital, Chinakakani, Guntur, and Andhra Pradesh between January 2022 to December 2022. Results: Hemangiomas are recognised from other benign liver lesions by a relative elevation in intralesional BF, ALP and HPI when compared with normal liver parenchyma, but BV, BF, PERM, ALP, PVP and HPI are all decreased due to the cystic content of these lesions. Conclusion: In addition to evaluating the efficacy of systemic or local tumour therapy, predicting the early response to anticancer medications, and monitoring the recurrence of tumours, liver CT perfusion imaging is a useful tool. [ABSTRACT FROM AUTHOR]

Purpose: Arterial spin labeling (ASL) acquisitions at multiple post‐labeling delays may provide more accurate quantification of cerebral blood flow (CBF), by fitting appropriate kinetic models and simultaneously estimating relevant parameters such as the arterial transit time (ATT) and arterial cerebral blood volume (aCBV). We evaluate the effects of denoising strategies on model fitting and parameter estimation when accounting for the dispersion of the label bolus through the vasculature in cerebrovascular disease. Methods: We analyzed multi‐delay ASL data from 17 cerebral small vessel disease patients (50 ± 9 y) and 13 healthy controls (52 ± 8 y), by fitting an extended kinetic model with or without bolus dispersion. We considered two denoising strategies: removal of structured noise sources by independent component analysis (ICA) of the control‐label image timeseries; and averaging the repetitions of the control‐label images prior to model fitting. Results: Modeling bolus dispersion improved estimation precision and impacted parameter values, but these effects strongly depended on whether repetitions were averaged before model fitting. In general, repetition averaging improved model fitting but adversely affected parameter values, particularly CBF and aCBV near arterial locations in patients. This suggests that using all repetitions allows better noise estimation at the earlier delays. In contrast, ICA denoising improved model fitting and estimation precision while leaving parameter values unaffected. Conclusion: Our results support the use of ICA denoising to improve model fitting to multi‐delay ASL and suggest that using all control‐label repetitions improves the estimation of macrovascular signal contributions and hence perfusion quantification near arterial locations. This is important when modeling flow dispersion in cerebrovascular pathology. [ABSTRACT FROM AUTHOR]

Background: The intravoxel incoherent motion (IVIM) model extracts both functional and structural information of a tissue using motion-sensitizing gradients. Objective: The Objective of the present work is to investigate the impact of signal to noise ratio (SNR) and physiologic conditions on the validity of IVIM parameters. Material and Methods: This study is a simulation study, modeling IVIM at a voxel, and also done 10,000 times for every single simulation. Complex noises with various standard deviations were added to signal in-silico to investigate SNR effects on output validity. Besides, some blood perfusion situations for different tissues were considered based on their physiological range to explore the impacts of blood fraction at each voxel on the validity of the IVIM outputs. Coefficient variation (CV) and bias of the estimations were computed to assess the validity of the IVIM parameters. Results: This study has shown that the validity of IVIM output parameters highly depends on measurement SNR and physiologic characteristics of the studied organ. Conclusion: IVIM imaging could be useful if imaging parameters are correctly selected for each specific organ, considering hardware limitations. [ABSTRACT FROM AUTHOR]

Type I Bipolar disorder (BD-I) is a neuropsychiatric disorder characterized by manic or mixed-featured episodes, impaired cognitive functioning, and persistent work and social functioning impairment. This study aimed to investigate withinsubject; (i) differences in brain perfusion using Single-photon emission computed tomography (SPECT) between manic and euthymic states in BD-I patients; (ii) explore potential associations between altered brain perfusion and cognitive status; and (iii) examine the relationship between cerebral perfusion and mania symptom ratings. Seventeen adult patients diagnosed with BD-I in a manic episode were recruited, and clinical assessments, cognitive tests, and brain perfusion studies were conducted at baseline (mania state) and a follow-up visit 6 months later. The results showed cognitive impairment during the manic episode, which persisted during the euthymic state at follow-up. However, no significant changes in brain perfusion were observed between the manic and euthymic states. During mania, trends toward decreased perfusion in the left cerebellum and right superior parietal lobule were noted. Additionally, trends indicated a higher perfusion imbalance in the left superior and middle frontal gyrus during mania and the right superior and middle frontal gyrus during euthymia. No significant correlations existed between brain perfusion, mania symptom ratings, and cognitive performance, indicating that symptomatology might represent more than neural hemodynamics. These findings suggest that cognitive impairment may persist in BD-I patients and highlight the need for therapeutic interventions targeting cognitive deficits. More extensive studies with extended follow-up periods are warranted further to investigate brain perfusion and cognitive functioning in BD-I patients. [ABSTRACT FROM AUTHOR]

Simple Summary: Glioblastomas are brain tumors with a poor prognosis, and early tumor progression occurs often. Therefore, patients are closely monitored with regular MRI scans, usually at 2–3 month intervals. However, there is no evidence for this strategy, and it is not known if patients benefit from this approach. Furthermore, effects from the treatment sometimes mimic tumor progression (pseudoprogression). Pseudoprogession can cause uncertainty and makes decision making about continuing or stopping treatment difficult. This study evaluated how often standard scheduled MRI scans influenced treatment decisions and how often MRI scans caused uncertainty. Standard scheduled follow-up MRI scans rarely led to treatment consequences (<10%). However, many MRI scans caused diagnostic uncertainty (>25%). When scans were made at unscheduled timepoints, e.g., in patients with new or worsening symptoms, they had more consequences. Our results do not support the current pragmatic follow-up strategy and suggest a more tailored follow-up approach for glioblastoma patients. MRI is the gold standard for treatment response assessments for glioblastoma. However, there is no consensus regarding the optimal interval for MRI follow-up during standard treatment. Moreover, a reliable assessment of treatment response is hindered by the occurrence of pseudoprogression. It is unknown if a radiological follow-up strategy at 2–3 month intervals actually benefits patients and how it influences clinical decision making about the continuation or discontinuation of treatment. This study assessed the consequences of scheduled follow-up scans post-chemoradiotherapy (post-CCRT), after three cycles of adjuvant chemotherapy [TMZ3/6], and after the completion of treatment [TMZ6/6]), and of unscheduled scans on treatment decisions during standard concomitant and adjuvant treatment in glioblastoma patients. Additionally, we evaluated how often follow-up scans resulted in diagnostic uncertainty (tumor progression versus pseudoprogression), and whether perfusion MRI improved clinical decision making. Scheduled follow-up scans during standard treatment in glioblastoma patients rarely resulted in an early termination of treatment (2.3% post-CCRT, 3.2% TMZ3/6, and 7.8% TMZ6/6), but introduced diagnostic uncertainty in 27.7% of cases. Unscheduled scans resulted in more major treatment consequences (30%; p < 0.001). Perfusion MRI caused less diagnostic uncertainty (p = 0.021) but did not influence treatment consequences (p = 0.871). This study does not support the current pragmatic follow-up strategy and suggests a more tailored follow-up approach. [ABSTRACT FROM AUTHOR]

Background Increased renin angiotensin aldosterone system (RAAS) activity may contribute to excess cardiovascular disease in people with HIV (PWH). We investigated how RAAS blockade may improve myocardial perfusion, injury, and function among well-treated PWH. Methods Forty PWH, on stable ART, without known heart disease were randomized to eplerenone 50 mg PO BID (n = 20) or identical placebo (n = 20) for 12 months. The primary endpoints were (1) myocardial perfusion assessed by coronary flow reserve (CFR) on cardiac PET or stress myocardial blood flow (sMBF) on cardiac MRI or (2) myocardial inflammation by extracellular mass index (ECM i) on cardiac MRI. Results Beneficial effects on myocardial perfusion were seen for sMBF by cardiac MRI (mean [SD]: 0.09 [0.56] vs −0.53 [0.68] mL/min/g; P =.03) but not CFR by cardiac PET (0.01 [0.64] vs −0.07 [0.48]; P =.72, eplerenone vs placebo). Eplerenone improved parameters of myocardial function on cardiac MRI including left ventricular end diastolic volume (−13 [28] vs 10 [26] mL; P =.03) and global circumferential strain (GCS; median [interquartile range 25th–75th]: −1.3% [−2.9%–1.0%] vs 2.3% [−0.4%–4.1%]; P =.03), eplerenone versus placebo respectively. On cardiac MRI, improvement in sMBF related to improvement in global circumferential strain (ρ = −0.65, P =.057) among those treated with eplerenone. Selecting for those with impaired myocardial perfusion (CFR <2.5 and/or sMBF <1.8), there was a treatment effect of eplerenone versus placebo to improve CFR (0.28 [0.27] vs −0.05 [0.36]; P =.04). Eplerenone prevented a small increase in troponin (0.00 [−0.13–0.00] vs 0.00 [0.00–0.74] ng/L; P =.03) without effects on ECM i (0.9 [−2.3–4.3] vs −0.7 [−2.2–−0.1] g/m2; P =.38). CD4+ T-cell count (127 [−38–286] vs −6 [−168–53] cells/μL; P =.02) increased in the eplerenone- versus placebo-treated groups. Conclusions RAAS blockade with eplerenone benefitted key indices and prevented worsening of myocardial perfusion, injury, and function among PWH with subclinical cardiac disease when compared with placebo. Clinical Trials Registration NCT02740179 (https://clinicaltrials.gov/ct2/show/NCT02740179?term=NCT02740179&draw=2&rank=1). [ABSTRACT FROM AUTHOR]

Objective: To explore the correlation between brain CT perfusion imaging features and cognitive function in patients with depression. Methods: 90 depression patients admitted to our hospital from January 2020 to January 2023 were selected as the study subjects and divided into an observation group. Additionally, 90 healthy volunteers who came to our hospital for physical examination during the same period were selected as the control group. Collect brain CT perfusion imaging data from all subjects, analyze the characteristics of brain CT perfusion imaging in patients with depression, and establish a receiver operating characteristic (ROC) curve to analyze the diagnostic efficacy of brain CT perfusion imaging in depression. Subsequently, cognitive function assessments were conducted on both the observation and control groups, including Connection detection (TMT), Visual Regeneration Test (VRT), Speech fluency test (VF), Digit span test (DST), and Digit Symbol (SDMT), And analyze the correlation between brain CT perfusion imaging and cognitive function in depression. Results: There was no significant difference in the CT values of rCBV, CBF, MTT, TIP, right occipital lobe, left occipital lobe, right temporal lobe, left temporal lobe, right parietal lobe, and left parietal lobe between the observation group and the control group (P>0.05). The CT values of the right frontal lobe and left frontal lobe between the observation group and the control group were significantly different, and the observation group was significantly lower than the control group (P<0.05); 90 patients with depression were evaluated by the Hamilton Depression Scale (HAMD) and their scores were all greater than 20 points, indicating the presence of depressive symptoms. There was no significant difference in the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value between brain CT perfusion imaging and HAMD score in diagnosing depression (P>0.05). The area under the curve of brain CT perfusion imaging was 83.89, the optimal diagnostic coloring limit was 82.53%, and the area under the curve of HAMD score was 84.26, The optimal diagnostic coloring threshold is 87.57%; There was no significant difference (P>0.05) between the observation group and the control group in the number of pen connections, number of connection errors, and visual regeneration test results. However, there was a significant difference (P<0.05) between the observation group and the control group in connection, speech fluency, number breadth, and number symbol test results; The Spearman correlation analysis results showed that there was no significant correlation between the number of line connections, line errors, visual regeneration, and brain CT perfusion parameters (P>0.05). Line connections, speech fluency, number span, and number symbols were negatively correlated with rCBV, CBF, MTT, TIP, right occipital lobe, left occipital lobe, right temporal lobe, left temporal lobe, right parietal lobe, and left parietal lobe CT values (P>0.05), while line connections were negatively correlated with right frontal lobe and left frontal lobe CT values (P<0.05). There is a positive correlation between speech fluency, numerical breadth, and numerical symbols with CT values in the right and left frontal lobes (P<0.05). Conclusion: There are differences in brain CT perfusion imaging between patients with depression and the healthy population, with the most significant differences in the right and left frontal lobes. This suggests that there may be changes in brain frontal lobe function in patients with depression. In addition, there is a significant correlation between brain frontal lobe function and cognitive function changes in patients with depression. [ABSTRACT FROM AUTHOR]

Cerebral abscesses are uncommon space occupying lesions; they are associated with high morbidity and mortality, though are potentially treatable. Patients often present with nonspecific symptoms and may have few clinical signs. Routine clinical imaging may not give a definite diagnosis, as the findings can be indistinguishable from those of other intracranial mass lesions. We review the role of advanced MR techniques to characterise brain abscesses and discuss the role of imaging in monitoring their response to the treatment. [ABSTRACT FROM AUTHOR]