Low Perfusion Areas Research Articles

Comparison of image quality and radiation doses between rapid kV-switching and dual-source DECT techniques in the chest

PurposeTo compare image quality and radiation doses for chest DECT acquired with dual-source and rapid-kV switching techniques. Materials and methodsOur institutional Review Board approved retrospective study included 97 patients (54 men, 43 women; 63 ± 14 years) who underwent contrast-enhanced chest DECT with both single source, rapid kV-switching (SS-DECT) and dual source (DS-DECT) techniques per standard of care departmental protocols. Reconstructed images from both scanners had identical section thickness and section interval for virtual monoenergetic and material decomposition iodine (MDI) images. Two thoracic radiologists independently evaluated all DECT for findings, quality of images, perfusion defects (MDI), and presence of artifacts. Radiation dose descriptor, size-specific dose estimates (SSDE), was recorded. Data were analyzed with Wilcoxon Signed Rank and Cohen’s Kappa tests. ResultsThere were no significant differences in patient weight or SSDE for the two DECT techniques (p > 0.06). Both radiologists reported no difference in lesion and artifact evaluation on the virtual monoenergetic images from either technique (p > 0.05). However, SS-DECT (in 63–71/97 patients) had substantial artifactual heterogeneity in pulmonary perfusion on MDI images compared to none on DS-DECT (p < 0.001). ConclusionDespite identical patients and associated radiation doses, there were substantial differences in material decomposition iodine images generated from SS-DECT and DS-DECT techniques. Pulmonary heterogeneity on MDI images from SS-DECT leads to artifactual areas of low perfusion and can confound interpretation of true pulmonary perfusion.

The efficacy and safety of endovascular recanalization of occluded large cerebral arteries during the subacute phase of cerebral infarction: a case series report

BackgroundIntravenous tissue plasminogen activator with or without mechanical thrombectomy during the acute phase are approved therapies for ischaemic stroke. Due to the short treatment time window (<6 hours) and often...

Evaluation of a proper cutoff value on quantitative dual-energy perfusion CT for the assessment of acute pulmonary thromboembolism.

Background The cutoff value for assessing the severity of acute pulmonary thromboembolism (PTE) using relative volumetric evaluations of dual-energy perfusion computed tomography (DEpCT) is unclear. Purpose To determine the proper cutoff value for determining the severity of PTE using DEpCT volumetry. Material and Methods A total of 185 patients with venous thromboembolism were included in this study, of whom 61 were diagnosed with acute PTE. DEpCT images were three-dimensionally reconstructed at the following attenuation ranges: 1-2 HU (V2), 1-10 HU (V10), and 1-120 HU (V120). The ratios of low perfusion areas associated with each threshold range per V120 were also calculated, and the relative ratios were expressed as %V2 to %V10. These values were compared with factors indicating the severity of PTE, including the pulmonary arterial pressure, heart rate, CT angiographic obstruction index (CTOI), and right/left ventricular diameter ratio (RV/LV). Results The area under the curve (AUC) of %V2 was highest (0.783) among these values (95% confidence interval, 0.710-0.856) based on the presence of IPCs. The %V2 showed moderate correlations with CTOI (r = 0.36, P = 0.005) and RV/LV (r = 0.36, P = 0.004) in the patients with acute PTE. Conclusion Volumetric evaluations of DEpCT images using the lowest attenuation threshold range (1-2 HU) exhibit the best correlation with factors suggesting the severity of acute PTE.

Laser speckle contrast imaging identifies ischemic areas on gastric tube reconstructions following esophagectomy.

Gastric tube reconstruction (GTR) is a high-risk surgical procedure with substantial perioperative morbidity. Compromised arterial blood supply and venous congestion are believed to be the main etiologic factors associated with early and late anastomotic complications. Identifying low blood perfusion areas may provide information on the risks of future anastomotic leakage and could be essential for improving surgical techniques. The aim of this study was to generate a method for gastric microvascular perfusion analysis using laser speckle contrast imaging (LSCI) and to test the hypothesis that LSCI is able to identify ischemic regions on GTRs.Patients requiring elective laparoscopy-assisted GTR participated in this single-center observational investigation. A method for intraoperative evaluation of blood perfusion and postoperative analysis was generated and validated for reproducibility. Laser speckle measurements were performed at 3 different time pointes, baseline (devascularized) stomach (T0), after GTR (T1), and GTR at 20° reverse Trendelenburg (T2).Blood perfusion analysis inter-rater reliability was high, with intraclass correlation coefficients for each time point approximating 1 (P < 0.0001). Baseline (T0) and GTR (T1) mean blood perfusion profiles were highest at the base of the stomach and then progressively declined towards significant ischemia at the most cranial point or anastomotic tip (P < 0.01). After GTR, a statistically significant improvement in mean blood perfusion was observed in the cranial gastric regions of interest (P < 0.05). A generalized significant decrease in mean blood perfusion was observed across all GTR regions of interest during 20° reverse Trendelenburg (P < 0.05).It was feasible to implement LSCI intraoperatively to produce blood perfusion assessments on intact and reconstructed whole stomachs. The analytical design presented in this study resulted in good reproducibility of gastric perfusion measurements between different investigators. LSCI provides spatial and temporal information on the location of adequate tissue perfusion and may thus be an important aid in optimizing surgical and anesthesiological procedures for strategically selecting anastomotic site in patients undergoing esophagectomy with GTR.

Mismatch of Low Perfusion and High Permeability Predicts Hemorrhagic Transformation Region in Acute Ischemic Stroke Patients Treated with Intra-arterial Thrombolysis.

This study sought to determine whether the permeability related parameter Ktrans, derived from computed tomography perfusion (CTP) imaging, can predict hemorrhagic transformation (HT) in patients with acute ischemic stroke who receive intra-arterial thrombolysis. Data from patients meeting the criterion were examined. CTP was performed and Ktrans maps were used to assess the permeability values in HT and non-HT regions. A receiver operating characteristic (ROC) curve was calculated, showing the sensitivity and specificity of Ktrans for predicting HT risk. Composite images were produced to illustrate the spatial correlations among perfusion, permeability changes and HT. This study examined 41 patients. Twenty-six patients had hemorrhagic infarction and 15 had parenchymal hemorrhage. The mean Ktrans value in HT regions was significantly lower than that in the non-HT regions (0.26 ± 0.21/min vs. 0.78 ± 0.64/min; P < 0.001). The ROC curve analysis identified an optimal cutoff value of 0.334/min for Ktrans to predict HT risk. Composite images suggested ischemic regions with low permeability, or the mismatch area of low perfusion and high permeability, more likely have HT. HT regions after intra-arterial thrombolysis had lower permeability values on Ktrans maps. The mismatch area of lower perfusion and higher permeability are more likely to develop HT.

Intratumor Heterogeneity of Perfusion and Diffusion in Clear-Cell Renal Cell Carcinoma: Correlation With Tumor Cellularity

BackgroundMagnetic resonance imaging (MRI) has the potential to noninvasively provide information about the tumor microenvironment. A correlation between arterial spin-labeled (ASL) MRI and tumor vasculature has been previously demonstrated; however, its correlation with tumor cellularity is unknown. We sought to assess intratumor heterogeneity of perfusion and diffusion in vivo in clear-cell renal cell carcinoma (ccRCC) using MRI and to correlate these findings with tumor vascularity and cellularity at histopathology. Patients and MethodsTwenty-three ccRCC patients underwent ASL and diffusion-weighted MRI before surgery after signing an informed consent in this prospective institutional review board–approved, HIPAA (Insurance Portability and Accountability Act)-compliant study. Quantitative ASL perfusion and diffusion were measured in 2 areas within the same tumor with high and low perfusion. Microvessel density (MVD) on CD31 and CD34 immunostains and tumor cellularity in anatomically coregistered tissue samples were correlated to MRI measurements (Spearman; P < .05 statistically significant). ResultsASL perfusion (P < .0001), CD31 MVD (P = .02), CD34 MVD (P = .04), and cellularity (P = .002) from high and low perfusion areas were significantly different across all tumors. There were positive correlations between tumor cellularity and CD31 MVD (ρ = 0.350, P = .021), CD31 and CD34 MVD (ρ = 0.838, P < .0001), ASL perfusion and cellularity (ρ = 0.406, P = .011), and ASL perfusion and CD31 MVD (ρ = 0.468, P = .003), and a negative correlation between tissue diffusion coefficient and cellularity (ρ = −0.316, P = .039). ConclusionTumor areas with high ASL perfusion exhibit higher cellularity and MVD compared to areas with low perfusion in the same tumor. A positive correlation between tumor vascularity and cellularity in ccRCC is newly reported. A negative correlation between tumor diffusion and cellularity is confirmed.

Precise Characterization of the Penumbra Revealed by MRI: A Modified Photothrombotic Stroke Model Study.

AimsTo precisely characterize the penumbra by MRI based on a modified photothrombotic stroke mouse model.MethodsThe proximal middle cerebral artery was occluded by a convenient laser system in conjunction with an intravenous injection of Rose Bengal in mice. And the suture MCAO model was performed in seven mice as a comparison of the reproducibility. One hour after occlusion, the penumbra was defined in six random photothrombotic stroke mice by mismatch between perfusion-weighted imaging and the apparent diffusion coefficient map on a home-made workstation. After imaging, three random mice of them were chosen to perform the reperfusion surgery. And the other three mice were sacrificed to stain for several potential penumbra markers, such as c-fos and heart shock protein 90. In the remaining mice, the evolution of the lesions was detected on the apparent diffusion coefficient map, diffusion-weighted imaging and T2-weighted imaging at 1, 3, 6, 12 and 24 hours. After evaluating the neurological deficit scores, the brains were sectioned and stained by triphenyltetrazolium chloride and Nissl.ResultsThe mice subjected to photothrombosis showed significant behavioral deficits. One hour after occlusion, the low perfusion areas on the perfusion-weighted imaging interlaced with the hypointense areas on the apparent diffusion coefficient map, demonstrating that the penumbra was located both surrounding and inside the lesions. This phenomenon was subsequently confirmed by the c-fos and heart shock protein 90 staining. The final T2-weighted images of the mice subjected to the reperfusion surgery were also consistent with the penumbra images at one hour. At early stages, the lesions were clearly identified on the apparent diffusion coefficient map; the volumes of the lesions on the diffusion-weighted imaging and T2-weighted imaging did not reach a maximum until 12 hours. The coefficient of variation (CV) of the final lesions in the photothrombotic stroke mice was 21.7% (0.08 of 0.37) on T2-weighted imaging and 27.8% (0.10 of 0.35) on triphenyltetrazolium chloride, representing a high reproducibility (n = 7). While the CV of the lesions in the MCAO stroke mice was only 70% (0.24 of 0.34, n = 4).ConclusionsThis study has provided a precise imaging definition of the penumbra based on a reproducible photothrombotic stroke mouse model.

Perfusion Intensity Correlates with Expression Levels of Psoriasis-Related Genes and Proteins

Background: Previous research revealed heterogeneity in the perfusion intensity within clinically homogenous-appearing plaques, without differences in erythema. In addition, an increased perfusion was found within the perilesional skin. This raises the question whether the heterogeneity in perfusion found both inside and outside a lesion influences the expression levels of genes and proteins involved in the pathogenesis of psoriasis. Objectives: To correlate the perfusion intensity to mRNA and protein expression of genes associated with the pathogenesis of psoriasis and to visualize the dynamics of the perfusion intensity over time using laser Doppler perfusion imaging. Methods: Fourteen patients with plaque psoriasis were included. The superficial microcirculation and clinical local scores (single usability metric, SUM, scores) were analysed in one representative lesion every 2 weeks. After 8 weeks 4 biopsies were taken, one from a highly perfused area (hotspot) and one from a low perfusion area (coldspot) of the lesional skin, one biopsy from the highly perfused perilesional skin and one from the distant uninvolved skin. Results: Statistically significant differences in mRNA and protein expression, including IL-17 and TBX21/T-Bet, were found between hotspots and coldspots, and between the highly perfused perilesional and the uninvolved skin. Hotspots tend to remain on the same location during 8 weeks of follow-up. Conclusions: Within homogenous-appearing psoriatic plaques, there are remarkable differences in mRNA and protein levels, which are correlated with the perfusion intensity and can be detected by using laser Doppler perfusion imaging. In addition, differences in mRNA and protein expression between the highly perfused perilesional skin and the uninvolved skin were found, indicating that several biological changes occur well before clinical changes become manifest.

Tumor Vascularity in Renal Masses: Correlation of Arterial Spin-Labeled and Dynamic Contrast-Enhanced Magnetic Resonance Imaging Assessments

BackgroundThe objective of this study was to investigate potential correlations between perfusion using arterial spin-labeled (ASL) magnetic resonance imaging (MRI) and dynamic contrast-enhanced (DCE) MRI-derived quantitative measures of vascularity in renal masses > 2 cm and to correlate these with microvessel density (MVD) in clear cell renal cell carcinoma (ccRCC). Patients and MethodsInformed written consent was obtained from all patients before imaging in this Health Insurance Portability and Accountability Act-compliant, institutional review board-approved, prospective study. Thirty-six consecutive patients scheduled for surgery of a known renal mass > 2 cm underwent 3T ASL and DCE MRI. ASL perfusion measures (PASL) of mean, peak, and low perfusion areas within the mass were correlated to DCE-derived volume transfer constant (Ktrans), rate constant (Kep), and fractional volume of the extravascular extracellular space (Ve) in the same locations using a region of interest analysis. MRI data were correlated to MVD measures in the same tumor regions in ccRCC. Spearman correlation was used to evaluate the correlation between PASL and DCE-derived measurements, and MVD. P < .05 was considered statistically significant. ResultsHistopathologic diagnosis was obtained in 36 patients (25 men; mean age 58 ± 12 years). PASL correlated with Ktrans (ρ = 0.48 and P = .0091 for the entire tumor and ρ = 0.43 and P = .03 for the high flow area, respectively) and Kep (ρ = 0.46 and P = .01 for the entire tumor and ρ = 0.52 and P = .008 for the high flow area, respectively). PASL (ρ = 0.66; P = .0002), Ktrans (ρ = 0.61; P = .001), and Kep (ρ = 0.64; P = .0006) also correlated with MVD in high and low perfusion areas in ccRCC. ConclusionPASL correlated with the DCE-derived measures of vascular permeability and flow, Ktrans and Kep, in renal masses > 2 cm in size. Both measures correlated to MVD in clear cell histology.

Intraoperative indocyanine green fluorescence angiography to predict wound complications in complex ventral hernia repair.

Complex ventral hernia repair (VHR) is associated with a greater than 30% wound complication rate. Perfusion mapping using indocyanine green fluorescence angiography (ICG-FA) has been demonstrated to predict skin and soft tissue necrosis in many reconstructive procedures; however, it has yet to be evaluated in VHR. Patients undergoing complex VHR involving component separation and/or extensive subcutaneous advancement flaps were included in a prospective, blinded study. Patients with active infection were excluded. ICG-FA was performed prior to incision and prior to closure, but the surgeon was not allowed to view it. An additional blinded surgeon documented wound complications and evaluated postoperative photographs. The operative ICG-FA was reviewed blinded, and investigators were then unblinded to determine its ability to predict wound complications. Fifteen consecutive patients were enrolled with mean age of 56.1 years and average BMI of 34.9, of which 60% were female. Most (73.3%) had prior hernia repairs (average of 1.8 prior repairs). Mean defect area was 210.4 cm2, mean OR time was 206 min, 66.6% of patients underwent concomitant panniculectomy, and 40% had component separation. Mean follow-up was 7 months. Two patients developed wound breakdown requiring reoperation, while 1 had significant fat necrosis and another a wound infection, requiring operative intervention. ICG-FA was objectively reviewed and predicted all 4 wound complications. Of the 12 patients without complications, 1 had an area of low perfusion on ICG-FA. This study found a sensitivity of 100% and specificity of 90.9% for predicting wound complications using ICG-FA. In complex VHR patients, subcutaneous perfusion mapping with ICG-FA is very sensitive and has the potential to reduce cost and improve patient quality of life by reducing wound complications and reoperation.

Optimization of arterial spin labeling MRI for quantitative tumor perfusion in a mouse xenograft model.

Perfusion is an important biomarker of tissue function and has been associated with tumor pathophysiology such as angiogenesis and hypoxia. Arterial spin labeling (ASL) MRI allows noninvasive and quantitative imaging of perfusion; however, the application in mouse xenograft tumor models has been challenging due to the low sensitivity and high perfusion heterogeneity. In this study, flow-sensitive alternating inversion recovery (FAIR) ASL was optimized for a mouse xenograft tumor. To assess the sensitivity and reliability for measuring low perfusion, the lumbar muscle was used as a reference region. By optimizing the number of averages and inversion times, muscle perfusion as low as 32.4 ± 4.8 (mean ± standard deviation) ml/100 g/min could be measured in 20 min at 7 T with a quantification error of 14.4 ± 9.1%. Applying the optimized protocol, heterogeneous perfusion ranging from 49.5 to 211.2 ml/100 g/min in a renal carcinoma was observed. To understand the relationship with tumor pathology, global and regional tumor perfusion was compared with histological staining of blood vessels (CD34), hypoxia (CAIX) and apoptosis (TUNEL). No correlation was observed when the global tumor perfusion was compared with these pathological parameters. Regional analysis shows that areas of high perfusion had low microvessel density, which was due to larger vessel area compared with areas of low perfusion. Nonetheless, these were not correlated with hypoxia or apoptosis. The results suggest that tumor perfusion may reflect certain aspect of angiogenesis, but its relationship with other pathologies needs further investigation.

SPECT cerebral perfusion imaging and its quantitative analysis for the assessment of stent implantation for cerebral artery stenosis

Objective To evaluate the role of SPECT cerebral perfusion imaging in assessing the stent implantation for cerebral artery stenosis. Methods A total of 35 patients (31 males, 4 females, average age (63.9±10.8) years) with cerebral artery stenosis confirmed by DSA for cerebral artery stent implantation were retrospectively analyzed. 99Tcm-ECD cerebral perfusion imaging was performed for all patients before and after stent implantation. The images were realigned and normalized by SPM 2.0 and then analyzed by Brain Search software for quantitative analysis. The brain was automatically separated to 210 functional areas according to Talarich map. The normalized averaged counts (NAC) of each area were calculated and compared with the data of 28 health controls(8 males, 20 females, average age (35.8±9.4) years). Less than 1.96s was defined as low perfusion lesions. The NAC values before and after stent implantation were compared for classifying improved from non-improved group. The mean number of lesions and Essen stroke risk score (ESRS) were analyzed between the two groups. The mean number of lesions and postoperative improvement rate of the internal carotid artery (ICA) occlusion and stenosis were compared. Paired rank sum test, two-sample t test, two-sample rank sum test and χ2 test were used for statistical analysis. Results In 35 patients with low perfusion areas, 20 were significantly improved after stent implantation. The mean number of lesions in the improved group(34.05±14.41) was significantly higher than that in the non-improved group (22.93±17.24; t=2.067, P 0.05). The mean number of the ICA occlusion lesions (34.36±14.31) was higher than that of the ICA stenosis lesions(31.35±16.37), but the difference was not statistically significant(t=0.498, P>0.05). The improvement rate of the ICA occlusion was higher than that of the ICA stenosis (7/11 vs 10/17), but the difference was not statistically significant(P>0.05). Conclusion SPECT cerebral perfusion imaging and its quantitative analysis can evaluate the low perfusion lesions before stent implantation and predict the perfusion improvement after stent implantation. Key words: Carotid stenosis; Stents; Tomography, emission-computed, single-photon; ECD

Memory impairment caused by cerebral hematoma in the left medial temporal lobe due to ruptured posterior cerebral artery aneurysm

BackgroundCognitive disorders, such as memory disturbances, are often observed following a subarachnoid hemorrhage. We present a very rare case where rupture of a posterior cerebral artery aneurysm caused restricted damage to the hippocampus unilaterally, and caused memory disturbances.Case presentationA 56-year-old, right-handed man, with a formal education history of 16 years and company employees was admitted to our hospital because of a consciousness disturbance. He was diagnosed as having a subarachnoid hemorrhage due to a left posterior cerebral artery dissecting aneurysm, and coil embolization was performed. Subsequently, he had neither motor paresis nor sensory disturbances, but he showed disorientation, and both retrograde and anterograde amnesia. Although immediate recall and remote memory were almost intact, his recent memory was moderately impaired. Both verbal and non-verbal memories were impaired. Brain computed tomography (CT) and magnetic resonance imaging (MRI) revealed a cerebral hematoma in the left temporal lobe involving the hippocampus and parahippocampal gyrus, and single-photon emission computed tomography (SPECT) demonstrated low perfusion areas in the left medial temporal lobe.ConclusionsWe suggest that the memory impairment was caused by local tissue destruction of Papez’s circuit in the dominant hemisphere due to the cerebral hematoma.

Volumetric evaluation of dual-energy perfusion CT by the presence of intrapulmonary clots using a 64-slice dual-source CT

Dual-energy perfusion CT (DEpCT) directly represents the iodine distribution in lung parenchyma and low perfusion areas caused by intrapulmonary clots (IPCs) are visualized as low attenuation areas. To evaluate if volumetric evaluation of DEpCT can be used as a predictor of right heart strain by the presence of IPCs. One hundred and ninety-six patients suspected of having acute pulmonary embolism (PE) underwent DEpCT using a 64-slice dual-source CT. DEpCT images were three-dimensionally reconstructed with four threshold ranges: 1-120 HU (V₁₂₀), 1-15 HU (V₁₅), 1-10 HU (V₁₀), and 1-5 HU (V₅). Each relative ratio per V₁₂₀ was expressed as the %V₁₅, %V₁₀, and %V₅. Volumetric data-sets were compared with D-dimer, pulmonary arterial (PA) pressure, right ventricular (RV) diameter, RV/left ventricular (RV/LV) diameter ratio, PA diameter, and PA/aorta (PA/Ao) diameter ratio. The areas under the ROC curves (AUCs) were examined for their relationship to the presence of IPCs. This study was approved by the local ethics committee. PA pressure and D-dimer were significantly higher in the patients who had IPCs. In the patients with IPCs, V₁₅, V₁₀, V₅, %V₁₅, %V₁₀, and %V₅ were also significantly higher than those without IPC (P ≤ 0.001). %V₅ had a better correlation with D-dimer (r = 0.30, P < 0.001) and RV/LV diameter ratio (r = 0.27, P < 0.001), and showed a higher AUC (0.73) than the other CT measurements. The volumetric evaluation by DEpCT had a correlation with D-dimer and RV/LV diameter ratio, and the relative ratio of volumetric CT measurements with a lower attenuation threshold might be recommended for the analysis of acute PE.

Mikrochirurgischer Beckenkammtransfer nach erfolgter Caldwell-Luc-Operation

The standard Caldwell-Luc procedure includes the removal of most of the maxillary sinus mucosa and the introduction of an inferior meatal antrostomy to promote sinus drainage. Pain, chronic relapsing inflammation and loss of volume are typical sequels of this procedure. Partial maxillary resection and iliac crest bone graft harvesting is a new concept and treatment option in such cases. The case of a 64-year-old woman who had previously undergone several unilateral sinus operations is presented. Fluorescein imaging was used to detect bone areas of low blood perfusion in the sinus walls. All affected bone and granulation tissue were removed. After resection, an iliac crest bone graft with vascular pedicle was performed to reconstruct the maxillary defect. Postoperative CT and scintigraphic imaging revealed a vital transplant. At the 10-month follow-up, no inflammation was observed and chronic pain was significantly reduced. The results clearly demonstrate that maxillary resection and iliac crest bone graft harvesting might be an option to treat severe cases of chronic sinusitis. Further prospective studies are necessary to confirm the advantages of this technique.

Chronically Epileptic Human and Rat Neocortex Display a Similar Resistance Against Spreading Depolarization In Vitro

Experimental and clinical evidence suggests that prolonged spreading depolarizations (SDs) are a promising target for therapeutic intervention in stroke because they recruit tissue at risk into necrosis by protracted intracellular calcium surge and massive glutamate release. Unfortunately, unlike SDs in healthy tissue, they are resistant to drugs such as N-methyl-d-aspartate-receptor antagonists. This drug resistance of SD in low perfusion areas may be due to the gradual rise of extracellular potassium before SD onset. Brain slices from patients undergoing surgery for intractable epilepsy allow for screening of drugs, targeting pharmacoresistant SDs under elevated potassium in human tissue. However, network changes associated with epilepsy may interfere with tissue susceptibility to SD. This could distort the results of pharmacological tests. We investigated the threshold for SD, induced by a gradual rise of potassium, in neocortex slices of patients with intractable epilepsy and of chronically epileptic rats as well as age-matched and younger control rats using combined extracellular potassium/field recordings and intrinsic optical imaging. Both age and epilepsy significantly increased the potassium threshold, which was similarly high in epileptic rat and human slices (23.6±2.4 mmol/L versus 22.3±2.8 mmol/L). Our results suggest that chronic epilepsy confers resistance against SD. This should be considered when human tissue is used for screening of neuroprotective drugs. The finding of similar potassium thresholds for SD in epileptic human and rat neocortex challenges previous speculations that the resistance of the human brain against SD is markedly higher than that of the rodent brain.

Effectiveness of magnetic resonance angiography in the evaluation of lung perfusion in constrictive bronchiolitis obliterans

Childhood constrictive bronchiolitis obliterans (CBO) is characterized clinically by the persistence of obstructive respiratory symptoms following a prolonged episode of lower respiratory viral infection. The diagnosis depends on the clinical, radiological and laboratory findings. Perfusion defects on scintigraphy may predict the severity. This report describes a 2-year-old girl who presented with a 15-day history of respiratory distress despite treatment. Auscultation of the lungs revealed prolonged expiration and bilateral crepitant rales. CXR revealed bilateral paracardiac infiltration. She improved with a treatment regimen of bronchodilators, systemic steroids and antibiotherapy; however, rales were detected again 10 days after discharge. HRCT of the lung revealed an oligaemic-mosaic pattern, more prominent in the left lung. The diagnosis of CBO was made on the basis of these clinical and radiological findings. Perfusion was normal in the right lung but diffusely decreased in the left lung on perfusion scintigraphy by Tc99m-MAA. Magnetic resonance (MR) angiography source images of the lungs revealed significant but not diffuse perfusion defects in the left lung, in contrast to radionuclide scintigraphy. There were areas of low perfusion in the right lung, which were not evident in radionuclide scintigraphy. The use of source images of MRI angiography of the lungs may be more sensitive and specific for the detection of perfusion defects in patients with CBO and may assist in determining the prognosis.

Vessel encoded arterial spin labeling with cerebral perfusion: preliminary study

Objective To evaluate a noninvasive vessel encoded imaging for selective mapping of the flow territories of the left and right internal carotid arteries and vertebral-basilar arteries. Methods Seven volunteers [(33.5±4.1) years ; 3 men, 4 women] and 6 patients [(55.2 ± 3.2) years; 2 men,4women] were given written informed consent approved by the institutional review board before participating in the study. A pseudo-continuous tagging pulse train is modified to encode all vessels of interest. The selectivity of this method was demonstrated. Regional perfusion imaging was developed on the same arterial spin labeling sequence. Perfusion-weighted images of the selectively labeled cerebral arteries were obtained by subtraction of the labeled from control images. The CBF values of hemisphere, white matter, and gray matter of volunteers were calculated. The vessel territories on patients were compared with DSA. The low perfusion areas were compared with high signal areas on T2-FLAIR. Results High SNR maps of left carotid, right carotid, and basilar territories were generated in 8 minutes of scan time. Cerebral blood flow 100 g-1 were in agreement with data in the literature. Vessel encoded imaging in patients had a good agreement with DSA. The low perfusion areas were larger than high signal areas on T2-FLAIR. Conclusion We present a new method capable of evaluating both quantitatively and qualitatively the individual brain-feeding arteries in vivo. Key words: Magnetic resonance imaging; Perfusion; Cerebral arteries

Ｌｅｐｔｏｍｅｎｉｎｇｅａｌ ｖｅｎｏｕｓ ｄｒａｉｎａｇｅを有するが，局所脳血流量検査で低灌流域を示さなかった硬膜動静脈瘻の検討

When dural arteriovenous fistula (DAVF) is associated with leptomeningeal venous drainage (LMVD), most cases have venous hypertension and concomitant venous congestion in the same areas due to reduced venous circulation. On the other hand, some cases in the DAVF with LMVD have no low-perfusion area. We studied this phenomenon. The subjects were 25 patients with DAVF. Of them, 16 cases had LMVD. Eleven had a low-perfusion area but 5 had no low-perfusion area. We analyzed this phenomenon in 5 cases. Two cases had anterior cranial fossa DAVF, 2 had tentorium DAVF, and 1 had transverse-sigmoid sinus DAVF. The characteristics of these DAVF are: 1) extra-sinusal type or pure leptomeningeal venous drainage, 2) low shunt flow, 3) existence of accessory route.

Image quality in CT perfusion imaging of the brain

The purpose of this study was to evaluate the impact of various iodine contrast concentrations on image quality in computed tomography (CT) perfusion studies. Twenty-one patients with suspicion of cerebral ischemia underwent perfusion CT using two different iodine contrast concentrations: 11 patients received iomeprol 300 (iodine concentration: 300 mg/ml ) while ten received the same volume of iomeprol 400 (iodine concentration: 400 mg/ml). Scan parameters were kept constant for both groups. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and time to peak (TTP) were calculated from two adjacent slices. Quantitative comparisons were based on measurements of the maximum enhancement [Hounsfield units (HU)] and signal-to-noise index (SNI) on CBF, CBV, and TTP images. Determinations of grey-to-white-matter delineation for each iodine concentration were performed by two blinded readers. Only data from the non-ischemic hemispheres were considered. Both maximum enhancement and SNI values were higher after iomeprol 400, resulting in significantly better image quality in areas of low perfusion. No noteworthy differences were found for normal values of CBF, CBV, and TTP. Qualitative assessment of grey/white matter contrast on CBF and CBV maps revealed better performance for iomeprol 400. For brain perfusion studies, highly concentrated contrast media such as iomeprol 400 is superior to iomeprol 300.