Blood Flow Maps Research Articles

Perfusion CT measurements in healthy cervical spinal cord: feasibility and repeatability of the study as well as interchangeability of the perfusion estimates using two commercially available software packages

Our purpose was to examine the feasibility and reproducibility of perfusion CT studies in the cervical spinal cord and the interchangeability of the values obtained by two post-processing methods. The perfusion CT studies of 40 patients with neck tumours were post-processed using two software packages (Software-1: deconvolution-based analysis with adiabatic tissue homogeneity approach and Software-2: maximum-slope-model with Patlak analysis). Eight patients were examined twice for assessing the reproducibility of the technique. Two neuroradiologists separately post-processed the images with two arterial input functions (AIFs): (1) the internal carotid artery (ICA) and (2) the vertebral artery (VA). Maps of blood flow (F) in ml/min/100 g, blood volume (V) in ml/100 g, mean transit time (MTT) in seconds (s) and permeability (PS) in ml/min/100 g were generated. The mean F, V, MTT and PS (Software-1) with VA-AIF and ICA-AIF were 8.93, 1.12, 16.3, 1.88 and 8.57, 1.19, 16.85 and 1.94, respectively. The reproducibility of the techniques was satisfactory, while the V and MTT values (in Software-1) and the F and V values (in Software-2) were dependent on the site of the AIF (p >or= 0.03 and p=0.02, respectively). The interobserver agreement was very good. The significant differences in measurements for a single patient (%) using Software-1/Software-2 were +/-120%/110%, 90%/80%, 180% and 250%/130% for F, V, MTT and PS, respectively. Only F and PS values in the healthy tissue seemed to be interchangeable. Our results were in essential agreement with those derived by invasive measurements in animals. The cervical spine perfusion CT studies are feasible and reproducible. The present knowledge has to be validated with studies in spinal cord tumours in order to decide the usefulness of the perfusion CT in this field.

Effect of vascular stenosis on perfusion‐weighted imaging; differences between calculation algorithms

To determine the most suitable postprocessing technique for magnetic resonance (MR) perfusion imaging in patients with vascular stenosis, by comparing the cerebral blood flow (CBF) maps of single photon emission tomography (SPECT) and perfusion MR imaging (MRI). In 15 consecutive patients (14 men and one woman, mean age 73.9 +/- 6.0 years) with stenosis of common carotid artery (CCA) or internal carotid artery (ICA) of more than 75%, both brain perfusion MRI and brain perfusion SPECT were performed. From perfusion MR images, CBF maps were calculated with the first moment, singular value decomposition (SVD), and block circulant SVD (b-SVD) methods, and CBF maps from each algorithm were compared with those from SPECT. The b-SVD method had the best correlation with SPECT (R = 0.814), followed by the first moment method (R = 0.776) and the SVD method (R = 0.723). The b-SVD method has the least mean difference with SPECT (0.118), the first moment method also had less difference (0.121), and the SVD had greatest mean difference (0.164). Our results suggest that in patients with vascular impairment the b-SVD method will be the technique of choice rather than SVD or first moment method.

Fast mapping of myocardial blood flow with MR first‐pass perfusion imaging

Accurate and fast quantification of myocardial blood flow (MBF) with MR first-pass perfusion imaging techniques on a pixel-by-pixel basis remains difficult due to relatively long calculation times and noise-sensitive algorithms. In this study, Zierler's central volume principle was used to develop an algorithm for the calculation of MBF with few assumptions on the shapes of residue curves. Simulation was performed to evaluate the accuracy of this algorithm in the determination of MBF. To examine our algorithm in vivo, studies were performed in nine normal dogs. Two first-pass perfusion imaging sessions were performed with the administration of the intravascular contrast agent Gadomer at rest and during dipyridamole-induced vasodilation. Radiolabeled microspheres were injected to measure MBF at the same time. MBF measurements in dogs using MR methods correlated well with the microsphere measurements (R2=0.96, slope=0.9), demonstrating a fair accuracy in the perfusion measurements at rest and during the vasodilation stress. In addition to its accuracy, this method can also be optimized to run relatively fast, providing potential for fast and accurate myocardial perfusion mapping in a clinical setting.

Effect of Inducible Nitric Oxide Synthase on Cerebral Blood Flow after Experimental Traumatic Brain Injury in Mice

Inducible nitric oxide synthase (iNOS) has been suggested to play a complex role in the response to central nervous system insults such as traumatic brain injury (TBI) and cerebral ischemia. In the current study, we quantified maps of regional cerebral blood flow (CBF) using an arterial spin-labeling magnetic resonance imaging (MRI) technique, at 24 and 72 h after experimental TBI in iNOS knockout (KO) and wild-type (WT) mice. Our hypothesis was that iNOS would contribute to the level of CBF at 72 h after experimental TBI in mice. Comparing anatomical brain regions of interest (ROIs) at 24-h post controlled cortical impact (CCI), there were significant reductions in CBF in the hemisphere, cortex, and contusion-rich area of the cortex of injured animals versus naive, regardless of genotype. Regional assessment of CBF at 72 h after injury demonstrated that recovery of CBF was reduced in the ipsilateral hippocampus, thalamus, and amygdala/piriform cortex in iNOS KO versus WT mice by 26%, 15%, and 21%, respectively; this attenuated recovery was restricted to structures outside the contusion. These regions with reduced CBF in iNOS KO mice represented ROIs where CBF in the WT was either numerically or statistically greater than that seen in respective WT naive, suggesting a contribution of iNOS to delayed posttraumatic hyperemia. However, pixel analysis denoted that the contribution of iNOS to CBF at 72 h was not limited to hyperemia flows. In conclusion, iNOS plays a role in the recovery of CBF after CCI in mice. Questions remain if this effect represents a homeostatic component of CBF recovery, pathologic vasodilatation linked to inflammation, or NO-mediated facilitation of angiogenesis.

Arterial Spin-Labeling in Routine Clinical Practice, Part 1: Technique and Artifacts

The routine use of arterial spin-labeling (ASL) in a clinical population has led to the depiction of diverse brain pathologic features. Unique challenges in the acquisition, postprocessing, and analysis of cerebral blood flow (CBF) maps are encountered in such a population, and high-quality ASL CBF maps can be generated consistently with attention to quality control and with the use of a dedicated postprocessing pipeline. Familiarity with commonly encountered artifacts can help avoid pitfalls in the interpretation of CBF maps. The purpose of this review was to describe our experience with a heterogeneous collection of ASL perfusion cases with an emphasis on methodology and common artifacts encountered with the technique. In a period of 1 year, more than 3000 pulsed ASL cases were performed as a component of routine clinical brain MR evaluation at both 1.5 and 3T. These ASL studies were analyzed with respect to overall image quality and patterns of perfusion on final gray-scale DICOM images and color Joint Photographic Experts Group (JPEG) CBF maps, and common artifacts and their impact on final image quality were categorized.

Post traumatic brain perfusion SPECT analysis using reconstructed ROI maps of radioactive microsphere derived cerebral blood flow and statistical parametric mapping

BackgroundAssessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets.MethodsThe focal effects of moderate traumatic brain injury (TBI) on cerebral blood flow (CBF) by SPECT cerebral blood perfusion (CBP) imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM).ResultsA significant area of hypoperfusion (P < 0.01) was found as a response to the TBI. Statistical mapping of the reference microsphere CBF data confirms a focal decrease found with SPECT and SPM.ConclusionThe suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques.

Middle Cerebral Artery Infarcts Encompassing the Insula Are More Prone to Growth

Based on previous observations that infarcts encompassing the insula were linked to unfavorable clinical outcome, we hypothesized that insular damage was directly associated with worsened infarction in ischemic but potentially viable neighboring brain tissue. Using acute diffusion- and perfusion-weighted MRI within the first 12 hours of symptom onset and a follow-up MRI on day 5 or later, we calculated the percentage of mismatch lost (PML) in 61 consecutive patients with ischemic stroke within the middle cerebral artery territory. PML denoted the percentage of mismatch tissue between diffusion-weighted imaging and mean transit time maps that eventually underwent infarction. We explored the relationship between PML and insular location using a regression model. The median PML was 17.7% (interquartile range, 3.5% to 54.2%) in insular and 2.5% (0.0% to 12.7%) in noninsular infarcts (P<0.01). The PML correlated with the volume of abnormal regions on diffusion-weighted imaging (P<0.01), mean transit time (P<0.01), cerebral blood flow maps (P<0.01), and cerebral blood volume maps (P<0.01). A linear regression model with PML as response and with acute MRI volumes, age, and the site of vascular occlusion as covariates showed that insular involvement was an independent predictor of PML (P=0.01). The regression model predicted an approximately 3.2-fold increase in PML with insular involvement. Infarction of the insula is associated with increased conversion of ischemic but potentially viable neighboring tissues into infarction. The unfavorable tissue outcome in insular infarcts may not be a mere bystander effect from proximal middle cerebral artery occlusions.

Measurement of Distribution of Blood-flow Change in Exposed Cortex by Laser Speckle Flowgraphy

The change in the cortical blood flow of guinea pigs during auditory stimulation is measured by laser speckle flowgraphy (LSFG). Accuracy of LSFG depends on the number of the frames for the blood flow calculation. The blood-flow maps of rotating disks and cortical tissues are calculated from various numbers of frames of speckle pattern, and the influence of the statistical error and averaging effect on the results is evaluated to optimise the LSFG system. The blood-flow map obtained from successive 24-30 frames can appropriately identify the change in the blood flow caused by auditory stimulation.

Evidence Against a Perihemorrhagic Penumbra Provided by Perfusion Computed Tomography

Several recent studies analyzing perfusion changes in acute intracerebral hemorrhage fed the debate whether there is secondary ischemic tissue damage in the vicinity of intracerebral hemorrhage. We used perfusion CT to address this question. We examined 36 patients between 2001 and 2002 with acute intracerebral hemorrhage (within 24 hours after symptom onset). A subgroup of 8 patients was examined serially on day 1, between days 2 and 4, and after day 5. Nonenhanced CT images and maps of cerebral blood flow, cerebral blood volume, and time to peak were evaluated by region of interest analysis. In comparison to the contralateral hemisphere, perfusion values were clearly reduced around the hematoma (relative values: cerebral blood flow 0.51, cerebral blood volume 0.62, time to peak 1.7 seconds). There was no difference in size between the area of reduced perfusion and the area of edema (5.17 versus 5.75 cm(2), respectively) surrounding the hematoma. At time point 2, the edema grew significantly. In accordance with previous studies, we found reduced perfusion as well as edema surrounding acute intracerebral hemorrhage. Regarding ischemic tissue damage, we did not detect an initial mismatch between the perfusion deficit and the edema and therefore could not identify any tissue at risk of ischemia. We therefore interpret the reduced perfusion as a secondary phenomenon, ie, reduced oxygen demand of tissue damaged by pressure and clot components, not as the cause of any tissue damage associated with acute intracerebral hemorrhage.

Delineation and segmentation of cerebral tumors by mapping blood-brain barrier disruption with dynamic contrast-enhanced CT and tracer kinetics modeling–a feasibility study

Dynamic contrast-enhanced (DCE) imaging is a promising approach for in vivo assessment of tissue microcirculation. Twenty patients with clinical and routine computed tomography (CT) evidence of intracerebral neoplasm were examined with DCE-CT imaging. Using a distributed-parameter model for tracer kinetics modeling of DCE-CT data, voxel-level maps of cerebral blood flow (F), intravascular blood volume (vi) and intravascular mean transit time (t1) were generated. Permeability-surface area product (PS), extravascular extracellular blood volume (ve) and extraction ratio (E) maps were also calculated to reveal pathologic locations of tracer extravasation, which are indicative of disruptions in the blood-brain barrier (BBB). All maps were visually assessed for quality of tumor delineation and measurement of tumor extent by two radiologists. Kappa (kappa) coefficients and their 95% confidence intervals (CI) were calculated to determine the interobserver agreement for each DCE-CT map. There was a substantial agreement for the tumor delineation quality in the F, ve and t1 maps. The agreement for the quality of the tumor delineation was excellent for the vi, PS and E maps. Concerning the measurement of tumor extent, excellent and nearly excellent agreement was achieved only for E and PS maps, respectively. According to these results, we performed a segmentation of the cerebral tumors on the base of the E maps. The interobserver agreement for the tumor extent quantification based on manual segmentation of tumor in the E maps vs. the computer-assisted segmentation was excellent (kappa = 0.96, CI: 0.93-0.99). The interobserver agreement for the tumor extent quantification based on computer segmentation in the mean images and the E maps was substantial (kappa = 0.52, CI: 0.42-0.59). This study illustrates the diagnostic usefulness of parametric maps associated with BBB disruption on a physiology-based approach and highlights the feasibility for automatic segmentation of cerebral tumors.

Comparison of arterial spin labeling and dynamic susceptibility-weighted contrast-enhanced MR imaging in brain gliomas

目的 探讨动脉质子自旋标记(ASL)与动态磁敏感对比增强(DSC)灌注技术用于脑胶质瘤分级的可行性.方法 经病理证实的28例脑胶质瘤患者,按世界卫生组织2000年规定的胶质瘤分级标准分为高级15例,低级13例.使用3.0 T MR扫描仪进行Q2TIPS的ASL检查和静脉团注钆喷替酸葡甲胺(Gd-DTPA)的DSC灌注检查.所得数据经两独立样本秩和检验分析,P＜0.05为差异有统计学意义;并用直线回归的方法分析两种灌注方法的相关性.结果 ASL法测得的脑胶质瘤血流量(TBF)/对侧脑白质相对血流量(CBF):高、低级别胶质瘤分别为(5.5±1.8)、(2.1±1.4),DSC法测得的值分别为(4.3±1.0)、(2.0±1.1),差异均有统计学意义(Z值分别为-3.824、-3.939,P＜0.01);ASL法测得的TBF/对侧半球CBF值,高、低级别胶质瘤分别为(2.2±0.8)、(0.8±0.5),DSC法测得的值分别为(2.1±0.8)、(1.0±0.6),差异均有统计学意义(Z值分别为-3.987、-3.386,P＜0.01);ASL法测得的TBF/对侧灰质CBF值,高、低级别胶质瘤分别为(1.7±0.6)、(0.7±0.5),DSC法测得值分别为(1.6±0.5)、(0.8±0.4),差异均有统计学意义(Z值分别为-3.894、-3.754,P＜0.01).两种方法测得的上述比值均密切相关(r分别为0.91、0.93、0.91,P＜0.01).结论 ASL可用于胶质瘤微血管灌注的评估,有助于区分低级别和高级别脑胶质瘤。

Window narrowing: a new method for standardized assessment of the tissue at risk-maximum of infarction in CT based brain perfusion maps

Background: Mapping of brain perfusion using bolus tracking methods is increasingly used to assess the amount and severity of cerebral ischemia in acute stroke. Using relative perfusionmaps, however, it is difficult to identify the tissue at risk-maximum (TARM) of infarction with sufficient reliability and reproducibility.Methods: We analysed 76 perfusion computed tomography (PCT) derived maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and time-to-peak (TTP) in 40 acute stroke patients using multidetector row technology and standard software (Somatom VolumeZoom, Siemens, Germany). 'Window narrowing' of the color maps was performed until color homogenisation of the contralateral unaffected hemisphere was reached. Tissue still depictable on the affected hemisphere after sufficient window narrowing was defined as the TARM. We analysed presence and size of the TARM on PCT maps, its relative perfusion values by comparison with contralateral, mirrored tissue, and its correlation with occurrence and final size of cerebral infarction on follow-up imaging.Results: An ischemic area was visible in 64, 58.9 and 72.6% on the conventional CBF, CBV and TTP maps, respectively. After window narrowing, a TARM was present in 56.8, 54.1 and 63.0% of slices comprising 11.9, 11.6 and 21.1% of the ipsilateral hemisphere (CBF, CBV and TTP), respectively. The relative perfusion values were 38.7 (CBF) and 43.0% (CBV) for the entire ischemic area and 11.3 (CBF) and 13.3% (CBV) for the TARM. Definite cerebral infarction was visible on 68.1% of the target slices comprising 23.7 ± 22.9% of the ipsilateral hemisphere. The size of the TARM correlated slightly better with the final infarction size (r=0.74–0.82) than the entire ischemic area (r=0.61–0.79). With respect to the occurrence of cerebral infarction, the presence of a TARM on CBF maps showed the best positive (97.9%) and negative (72.7%) predictability.Discussion: On PCT maps, window narrowing provides a standardized display of the TARM in peracute stroke. The severely reduced values of relative CBF and CBV suggest the TARM to indicate tissue most prone to infarction.

Identification of the penumbra and infarct core on hyperacute noncontrast and perfusion CT

To correlate the two types of early ischemic change on noncontrast CT (NCCT) (parenchymal hypoattenuation [PH] and isolated focal swelling [IFS]) with concurrent assessment of cerebral perfusion and to compare their rates of progression to infarction. We assessed cortical regions on NCCT for early ischemic change. Quantitative perfusion values were calculated for cortical regions from acute CT perfusion (CTP) maps of cerebral blood volume (CBV), blood flow (CBF), and mean transit time (MTT). Reperfusion and presence of infarction were determined from follow-up MRI. We studied 40 patients with sub-6 hour anterior circulation ischemic stroke; 19 received IV recombinant tissue plasminogen activator. Of the 202 regions acutely hypoperfused on CTP, 123 were normal on NCCT, 58 had PH, and 21 had IFS. Acute CBV was low in PH regions, and elevated in IFS regions. Acute CBF was reduced in IFS regions, but more so in PH regions. Progression to infarction occurred in virtually all PH regions, but IFS regions had much lower rates of infarction with major reperfusion. Acute CBV in hypoperfused normal NCCT regions ranged from reduced to elevated, with substantially differing risk of infarction. Isolated focal swelling identifies penumbral tissue and parenchymal hypoattenuation identifies infarct core. Although this has prognostic implications when assessing patient suitability for thrombolytic therapy, the majority of acutely hypoperfused regions appear normal on noncontrast CT. Perfusion CT can stratify the level of risk of subsequent infarction for normal-appearing regions on noncontrast CT.

Effect of the Arterial Input Function on the Measured Perfusion Values and Infarct Volumetric in Acute Cerebral Ischemia Evaluated by Perfusion Computed Tomography

We sought to evaluate the accuracy of the perfusion computed tomography (PCT) deconvolution-based brain perfusion measurements and the lesions' (infarct and penumbra) volumetric with regard to arterial input function (AIF) selection in patients with acute stroke. Eighteen consecutive patients with symptoms of acute stroke underwent PCT at admission. Follow-up magnetic resonance imaging was obtained in all patients after 3.6 +/- 1.7 days (range, 1.5-6 days). PCT maps were generated focusing on the anterior cerebral artery (ACA) and branches of the middle cerebral artery (MCA) ipsilateral and contralateral to the ischemic lesion as AIFs. Infarct, penumbra, and total ischemic lesion were delineated on cerebral blood flow (CBF) maps. CBF, cerebral blood volume (CBV), and mean transit time (MTT) were calculated in the ischemic regions as provided by the 3 different AIFs, the normality test was applied for the obtained parameters, and the values were correlated (Pearson's correlation coefficient). Volumes of the ischemic regions (as obtained by the different AIFs) also were correlated and compared (paired t test) to the follow-up infarct volume. The CBF and CBV values obtained by the different AIFs in the infarct, penumbra, and total ischemic lesion were significantly correlated (r=0.94-0.96, P<or=0.01). Only in the infarct region calculated MTT values were correlated (r=0.88-0.91, P<0.05) between the different AIFs groups. High correlation coefficients (r=0.79-0.91, P<0.001) were observed between the admission PCT infarct and total ischemic volume and the MRI follow-up infarct volume. ACA as AIF provided the best correlations (r=0.91, P=0.0002) with the follow-up measurements. No statistically significant difference was found between the 3 different AIF-estimated admission total ischemic volumes and the follow-up infarct volume. The AIF selection in the ACA as well as in the ipsilateral (to the hypoperfused area) or contralateral branches of the MCA has no statistically significant impact on the calculation of the CBF, CBV values, and the volume estimation of the ischemic region in the acute stroke patients.

Correspondence of CT perfusion imaging to pathological manifestations in rabbit models of hyperacute cerebral infarction*

Correspondence of CT perfusion imaging to pathological manifestations in rabbit models of hyperacute cerebral infarction*

Cortical contusion induces trans-hemispheric reorganization of blood flow maps

Cerebral blood flow (CBF), a surrogate of neural activity in the identification of brain regions involved in specific functions, has been used in this report to trace the compensatory enhancement of activity in non-traumatized areas of the brain following a focal lesion. We have previously shown activation of CBF in the cortex contralateral to a focal contusion, 24 h after the event. The present report extends the characterization of this trans-hemispheric cortical blood flow activation by studying its time course and regional distribution from 4 days to 4 weeks post-trauma. Adult male Sprague–Dawley rats received a cortical impact through a 6.3 mm craniotomy under halothane anesthesia. CBF was measured with the quantitative autoradiographic 14C-Iodoantipyrine technique, in conscious animals, 4 days, 2 weeks and 4 weeks post-trauma. CBF was severely decreased at the site of impact where necrosis developed later, and it remained depressed in the surrounding areas throughout the observation period. Trans-hemispheric CBF enhancement was maximal at 4 days and it returned to control levels 28 days post-trauma. This phenomenon was present in all cortical regions symmetrical to the impact zone, but also in auditory, visual, entorhinal and insular cortex. These results suggest that the participation of the contralateral cortex in the recovery from unilateral brain trauma is not limited to the regions homologous to those that received the impact. The time course of CBF changes was found to be consistent with the recovery of motor function in this model.

Microsphere maps of regional blood flow and regional ventilation

Systematically mapped samples cut from lungs previously labeled with intravascular and aerosol microspheres can be used to create high-resolution maps of regional perfusion and regional ventilation. With multiple radioactive or fluorescent microsphere labels available, this methodology can compare regional flow responses to different interventions without partial volume effects or registration errors that complicate interpretation of in vivo imaging measurements. Microsphere blood flow maps examined at different levels of spatial resolution have revealed that regional flow heterogeneity increases progressively down to an acinar level of scale. This pattern of scale-dependent heterogeneity is characteristic of a fractal distribution network, and it suggests that the anatomic configuration of the pulmonary vascular tree is the primary determinant of high-resolution regional flow heterogeneity. At approximately 2-cm(3) resolution, the large-scale gravitational gradients of blood flow per unit weight of alveolar tissue account for <5% of the overall flow heterogeneity. Furthermore, regional blood flow per gram of alveolar tissue remains relatively constant with different body positions, gravitational stresses, and exercise. Regional alveolar ventilation is accurately represented by the deposition of inhaled 1.0-microm fluorescent microsphere aerosols, at least down to the approximately 2-cm(3) level of scale. Analysis of these ventilation maps has revealed the same scale-dependent property of regional alveolar ventilation heterogeneity, with a strong correlation between ventilation and blood flow maintained at all levels of scale. The ventilation-perfusion (VA/Q) distributions obtained from microsphere flow maps of normal animals agree with simultaneously acquired multiple inert-gas elimination technique VA/Q distributions, but they underestimate gas-exchange impairment in diffuse lung injury.

Quantification of cerebral blood flow by flow-sensitive alternating inversion recovery exempting separate T1 measurement in healthy volunteers

The feasibility of the mapping of quantitative cerebral blood flow (CBF) named flow-sensitive alternating inversion recovery exempting separate T1 measurement (FAIREST) is still controversial. This study aimed to evaluate the reliability of FAIREST in the measurement of regional CBF (rCBF) in healthy volunteers. Eighteen healthy volunteers underwent magnetic resonance (MR) scanning with the sequence of FAIREST. While they were at rest, rCBF values were obtained in various brain regions of interest (ROIs). The same scheme was repeated on every subject after two weeks. Statistical analysis was made to determine the effect of location, scan and side on the measurement of rCBF. The mean CBF values were (122+/-28) ml x (100 g)(-1) x min(-1) and (43+/-10) ml x (100 g)(-1) x min(-1) in the gray and white matter respectively. There was significant main effect of location (t=-12.5, P<0.01), but no significant effect of side. Paired t-test of ROIs in the same slice showed no significant difference in most sites between two scans, except in the gray matter of the bilateral frontal lobes (t=2.18-2.34, P <0.05). However, the rCBF values of the same structure obtained from different slices showed a significant difference (t=-3.49, P<0.01). FAIREST is a reliable technique in the measurement of rCBF, but different imaging slice may affect the agreement of rCBF across the scans.

Cardiac Nociception

Cardiac Nociception

Comparison between coated vs. uncoated suture middle cerebral artery occlusion in the rat as assessed by perfusion/diffusion weighted imaging

Differences among models in the temporal evolution of ischemia after middle cerebral artery occlusion (MCAO) in rats may considerably influence the results of experimental treatment studies. Using diffusion and perfusion imaging, we compared the spatiotemporal evolution of ischemia in Sprague-Dawley rats after permanent MCAO (pMCAO) with different types of sutures. Male Sprague-Dawley rats were randomly assigned to pMCAO produced with either 4-0 silicone coated ( n = 8), or 3-0 uncoated monofilaments ( n = 8). Serial determination of quantitative cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) maps were performed up to 3 h after pMCAO. Lesion volumes were calculated by using previously validated thresholds and correlated with infarct volume corrected for edema defined by 2,3,5-triphenyltetrazolium chloride (TTC) staining at 24 h after MCAO. The ADC/CBF-defined mismatch volume in the 4-0 coated suture model was present significantly longer (up to 120 min) compared to the uncoated 3-0 suture model (30 min). The TTC-derived infarct volume was significantly larger in the coated model (290.3 ± 32.8 mm 3) relative to the uncoated model (252.3 ± 34.6 mm 3). This study demonstrates that the type of suture may significantly influence the spatiotemporal evolution of the ADC/CBF-mismatch as well as the final infarct volume. These inter-model variations must be taken into account when assessing new therapeutic approaches on ischemic lesion evolution in the rat MCAO model.