Dynamic Susceptibility Contrast Method Research Articles

Quantitative perfusion mapping with induced transient hypoxia using BOLD MRI.

Gadolinium-based dynamic susceptibility contrast (DSC) is commonly used to characterize blood flow in patients with stroke and brain tumors. Unfortunately, gadolinium contrast administration has been associated with adverse reactions and long-term accumulation in tissues. In this work, we propose an alternative deoxygenation-based DSC (dDSC) method that uses a transient hypoxia gas paradigm to deliver a bolus of paramagnetic deoxygenated hemoglobin to the cerebral vasculature for perfusion imaging. Through traditional DSC tracer kinetic modeling, the MR signal change induced by this hypoxic bolus can be used to generate regional perfusion maps of cerebral blood flow, cerebral blood volume, and mean transit time. This gas paradigm and blood-oxygen-level-dependent (BOLD)-MRI were performed concurrently on a cohort of 66 healthy and chronically anemic subjects (age 23.5±9.7, female 64%). Our results showed reasonable global and regional agreement between dDSC and other flow techniques, such as phase contrast and arterial spin labeling. In this proof-of-concept study, we demonstrated the feasibility of using transient hypoxia to generate a contrast bolus that mimics the effect of gadolinium and yields reasonable perfusion estimates. Looking forward, optimization of the hypoxia boluses and measurement of the arterial-input function is necessary to improve the accuracy of dDSC. Additionally, a cross-validation study of dDSC and DSC in brain tumor and ischemic stroke subjects is warranted to evaluate the clinical diagnostic utility of this approach.

PROSEDUR PEMERIKSAAN MAGNETIC RESONANCE IMAGING (MRI) BRAIN PERFUSI DENGAN METODE ARTERIAL SPIN LABELING (ASL) PADA PASIEN TUMOR

Background : Examination procedure of Magnetic resonance imaging (MRI) Brain Perfusion in patient with tumor disease at Radiology Department of National Brain Hospital used the MR Perfusion sequence with the Dynamic Susceptibility Contrast (DSC) method with the addition of Arterial Spin Labeling (ASL) method which was also used to determine CBF values. Nevertheless CBF values can also be obtained from the use of the DSC method. The application of these two roles in patient with tumor disease certainly has their respective roles in providing accurate information for the diagnosis. The purpose of this study was to determine the role of the application of MR perfusion with the Arterial Spin Labeling (ASL) method and the Dynamic Susceptibility Contrast (DSC) method for the diagnosis of patient with tumor disease at Radiology Department of National Brain Hospital.
 Methods :The type of this research is qualitative with case study approach. The data were collected from March – April 2019 at at Radiology Department of National Brain Hospital by using observation method, interview with radiology specialist doctor, sending doctor, FGD, and documentation. Data obtained from the study were analyzed by making the transcript then reduced in the form of categorization table and open coding, presented in quote form and then can be drawn conclusion.
 Result : Brain perfusion MRI examination procedures in tumor patients begin with examination preparation, preparation of tools and materials, carry out the examination using the MRI Brain protocol with contrast and without contrast. The use of contrast uses the Dynamic Susceptibility Contrast (DSC) method and non-contrast use using the Arterial Spin Labeling (ASL) method where both complement each other to inform perfusion parameter values.
 Conclusion : The conclution of this study indicate still needed the application of both MR perfusion methods, namely the ASL method and the DSC method. The ASL method will provide additional information in the form of absolute values of Cerebral Blood Flow that are not affected by permeability, besides that the DSC method is able to provide Cerebral Blood Volume values that are used as a parameter of Perfusion MR evaluation.
 Keyword : ASL, DSC, Tumor, CBF

Application of histogram analysis for the evaluation of vascular permeability in glioma by the K2 parameter obtained with the dynamic susceptibility contrast method: Comparisons with Ktrans obtained with the dynamic contrast enhance method and cerebral blood volume

PurposeThe “K2” value is a factor that represents the vascular permeability of tumors and can be calculated from datasets obtained with the dynamic susceptibility contrast (DSC) method. The purpose of the current study was to correlate K2 with Ktrans, which is a well-established permeability parameter obtained with the dynamic contrast enhance (DCE) method, and determine the usefulness of K2 for glioma grading with histogram analysis. MethodsThe subjects were 22 glioma patients (Grade II: 5, III: 6, IV: 11) who underwent DSC studies, including eight patients in which both DSC and DCE studies were performed on separate days within 10days. We performed histogram analysis of regions of interest of the tumors and acquired 20th percentile values for leakage-corrected cerebral blood volume (rCBV20%ile), K2 (K220%ile), and for patients who underwent a DCE study, Ktrans (Ktrans20%ile). We evaluated the correlation between K220%ile and Ktrans20%ile and the statistical difference between rCBV20%ile and K220%ile. ResultsWe found a statistically significant correlation between K220%ile and Ktrans20%ile (r=0.717, p<0.05). rCBV20%ile showed a significant difference between Grades II and III and between Grades II and IV, whereas K220%ile showed a statistically significant (p<0.05) difference between Grades II and IV and between Grades III and IV. ConclusionsThe K2 value calculated from the DSC dataset, which can be obtained with a short acquisition time, showed a correlation with Ktrans obtained with the DCE method and may be useful for glioma grading when analyzed with histogram analysis.

MRI of Perfusion: Principles and Clinical Applications.

The principle and clinical application of measurement of cerebral blood perfusion (CBP) using MRI are described. Purposes of measuring CBP using MRI are wide-ranging. Generally, it is used to diagnose cerebro-vascular disorders or brain tumors. There are two types of measuring methods. One is dynamic susceptibility contrast (DSC) method using a contrast agent as a tracer. Another is an arterial spin labeling (ASL) method using protons in arterial blood as an endogenous tracer, instead of bio-exogenous tracer. Basic theory of ASL method was published in the 1990s, recently, its clinical application has been spreading rapidly by the technological innovations. ASL method is attractive as a way to measure CBP because of its non-invasiveness (no radiation-exposure, not need intravenous injection or blood sampling), and the imaging time is about 5 minutes, thereby the measurement can be repeated. The analysis of DSC method has not been standardized, though various valuable parameters are provided. And the prerequisite of DSC method is uncertain in vivo. On the other hand, the result of ASL is affected by the post labeling delay, and limited to the arterial information.

Differentiation of high-grade and low-grade diffuse gliomas by intravoxel incoherent motion MR imaging.

Our aim was to assess the diagnostic performance of intravoxel incoherent motion (IVIM) MR imaging for differentiating high-grade gliomas (HGGs) from low-grade gliomas (LGGs). Forty-five patients with diffuse glioma (age 50.9 ± 20.4 y; 26 males, 19 females) were assessed with IVIM imaging using 13 b-values (0-1000 s/mm(2)) at 3T. The perfusion fraction (f), true diffusion coefficient (D), and pseudo-diffusion coefficient (D*) were calculated by fitting the bi-exponential model. The apparent diffusion coefficient (ADC) was obtained with 2 b-values (0 and 1000 s/mm(2)). Relative cerebral blood volume was measured by the dynamic susceptibility contrast method. Two observers independently measured D, ADC, D*, and f, and these measurements were compared between the LGG group (n = 16) and the HGG group (n = 29). Both D (1.26 ± 0.37 mm(2)/s in LGG, 0.94 ± 0.19 mm(2)/s in HGG; P < .001) and ADC (1.28 ± 0.35 mm(2)/s in LGG, 1.03 ± 0.19 mm(2)/s in HGG; P < .01) were lower in the HGG group. D was lower than ADC in the LGG (P < .05) and HGG groups (P < .0001). D* was not different between the groups. The f-values were significantly larger in HGG (17.5 ± 6.3%) than in LGG (5.8 ± 3.8%; P < .0001) and correlated with relative cerebral blood volume (r = 0.85; P < .0001). Receiver operating characteristic analyses showed areas under curve of 0.95 with f, 0.78 with D, 0.73 with ADC, and 0.60 with D*. IVIM imaging is useful in differentiating HGGs from LGGs.

ASFNR recommendations for clinical performance of MR dynamic susceptibility contrast perfusion imaging of the brain.

MR perfusion imaging is becoming an increasingly common means of evaluating a variety of cerebral pathologies, including tumors and ischemia. In particular, there has been great interest in the use of MR perfusion imaging for both assessing brain tumor grade and for monitoring for tumor recurrence in previously treated patients. Of the various techniques devised for evaluating cerebral perfusion imaging, the dynamic susceptibility contrast method has been employed most widely among clinical MR imaging practitioners. However, when implementing DSC MR perfusion imaging in a contemporary radiology practice, a neuroradiologist is confronted with a large number of decisions. These include choices surrounding appropriate patient selection, scan-acquisition parameters, data-postprocessing methods, image interpretation, and reporting. Throughout the imaging literature, there is conflicting advice on these issues. In an effort to provide guidance to neuroradiologists struggling to implement DSC perfusion imaging in their MR imaging practice, the Clinical Practice Committee of the American Society of Functional Neuroradiology has provided the following recommendations. This guidance is based on review of the literature coupled with the practice experience of the authors. While the ASFNR acknowledges that alternate means of carrying out DSC perfusion imaging may yield clinically acceptable results, the following recommendations should provide a framework for achieving routine success in this complicated-but-rewarding aspect of neuroradiology MR imaging practice.

Defining the ischemic penumbra using magnetic resonance oxygen metabolic index.

Penumbral biomarkers promise to individualize treatment windows in acute ischemic stroke. We used a novel magnetic resonance imaging approach that measures oxygen metabolic index (OMI), a parameter closely related to positron emission tomography-derived cerebral metabolic rate of oxygen utilization (CMRO2), to derive a pair of ischemic thresholds: (1) an irreversible-injury threshold that differentiates ischemic core from penumbra and (2) a reversible-injury threshold that differentiates penumbra from tissue not-at-risk for infarction. Forty patients with acute ischemic stroke underwent magnetic resonance imaging at 3 time points after stroke onset: <4.5 hours (for OMI threshold derivation), 6 hours (to determine reperfusion status), and 1 month (for infarct probability determination). A dynamic susceptibility contrast method measured cerebral blood flow, and an asymmetrical spin echo sequence measured oxygen extraction fraction, to derive OMI (OMI=cerebral blood flow×oxygen extraction fraction). Putative ischemic threshold pairs were iteratively tested using a computation-intensive method to derive infarct probabilities in 3 tissue groups defined by the thresholds (core, penumbra, and not-at-risk tissue). An optimal threshold pair was chosen based on its ability to predict infarction in the core, reperfusion-dependent survival in the penumbra, and survival in not-at-risk tissue. The predictive abilities of the thresholds were then tested within the same cohort using a 10-fold cross-validation method. The optimal OMI ischemic thresholds were found to be 0.28 and 0.42 of normal values in the contralateral hemisphere. Using the 10-fold cross-validation method, median infarct probabilities were 90.6% for core, 89.7% for nonreperfused penumbra, 9.95% for reperfused penumbra, and 6.28% for not-at-risk tissue. OMI thresholds, derived using voxel-based, reperfusion-dependent infarct probabilities, delineated the ischemic penumbra with high predictive ability. These thresholds will require confirmation in an independent patient sample.

MR evaluation of vessel size imaging of human gliomas: Validation by histopathology

To compare the vessel size and the cerebral blood volume in human gliomas with histopathology. Vessel size imaging (VSI) is a dynamic susceptibility contrast method for the assessment of the vessel size in normal and pathological tissue. Previous publications in rodents showed a satisfactory conformity with the vessel size derived from histopathology. To assess the clinical value, further, the progression-free interval was determined and correlated. Twenty-five gliomas (WHO grade °II [n = 10], °III [n = 3], °IV [n = 12]) were prospectively included and received a stereotaxic biopsy after VSI. The vessel size and the cerebral blood volume (CBV) were calculated in regions of interest at the tumor edge and correlated with the vessel size measured by histopathology. Both VSI and CBV showed a good correlation with the vessel size in histopathology (up to r = 0.84, P < 0.001, and r = 0.62, P < 0.001, respectively). Slope and offset of the linear regression (y = 0.77x + 0.36 μm) suggest that the size of normal capillaries is overestimated with VSI, while for grossly enlarged vessels an underestimation occurs. Both VSI and CBV were negatively correlated with the progression-free interval (r = -0.57, P = 0.008, and r = -0.50, P = 0.025, respectively). The correlation between VSI and vessel size from histopathology is in good accordance with the animal studies. The overestimation of small capillary sizes is also known from the animal trials. Vessel size and CBV showed similar results, both for the correlation with the histopathological vessel size and the progression-free interval.

Which is the best advanced MR imaging protocol for predicting recurrent metastatic brain tumor following gamma-knife radiosurgery: focused on perfusion method.

High spatial resolution of dynamic contrast-enhanced (DCE) MR imaging allows characterization of heterogenous tumor microenvironment. Our purpose was to determine which is the best advanced MR imaging protocol, focused on additional MR perfusion method, for predicting recurrent metastatic brain tumor following gamma-knife radiosurgery (GKRS). Seventy-two consecutive patients with post-GKRS metastatic brain tumor were enrolled. Two readers independently calculated the percentile histogram cutoffs for normalized cerebral blood volume (nCBV) from dynamic susceptibility contrast (DSC) imaging and initial area under the time signal-intensity curve (IAUC) from DCE imaging, respectively. Area under the receiver operating characteristic curve (AUC) and interreader agreement were assessed. For differentiating tumor recurrence from therapy effect, adding DCE imaging to diffusion-weighted imaging (DWI) significantly improved AUC from 0.79 to 0.95 for reader 1 and from 0.80 to 0.96 for reader 2, respectively. There was no significant difference of AUC between the combination of DWI with DSC imaging and the combination of DWI with DCE imaging for both readers. With the combination of DWI and DCE imaging, the sensitivity and specificity were 86.7 and 88.1% for reader 1 and 90.0 and 85.7% for reader 2, respectively. The intraclass correlation coefficient (ICC) between readers was highest for calculation of the 90th percentile histogram cutoffs for IAUC (ICC, 0.87). Adding perfusion MR imaging to DWI significantly improves the prediction of recurrent metastatic tumor; however, the diagnostic performance is not affected by selection of either DSC or DCE MR perfusion method.

Assesment of perfusion in glial tumors with arterial spin labeling; comparison with dynamic susceptibility contrast method

PurposeArterial spin labeling perfusion imaging (ASL-PI) is a non-invasive perfusion imaging method that can be used for evaluation and quantification of cerebral blood flow (CBF). Aim of our study was to evaluating the efficiency of ASL in histopathological grade estimation of glial tumors and comparing findings with dynamic susceptibility contrast perfusion imaging (DSC-PI) method. MethodsThis study involved 33 patients (20 high-grade and 13 low-grade gliomas). Multiphase multislice pulsed ASL MRI sequence and a first-passage gadopentetate dimeglumine T2*-weighted gradient-echo single-shot echo-planar sequence were acquired for all the patients. For each patient, perfusion relative signal intensity (rSI), CBF and relative CBF (rCBF) on ASL-PI and relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) values on DSC-PI were determined. The relative signal intensity of each tumor was determined as the maximal SI within the tumor divided by SI within symetric region in the contralateral hemisphere on ASL-PI. rCBV and rCBF were calculated by deconvolution of an arterial input function. Relative values of the lesions were obtained by dividing the values to the normal appearing symmetric region on the contralateral hemisphere. For statistical analysis, Mann–Whitney ranksum test was carried out. Receiver operating characteristic curve (ROC) analysis was performed to assess the relationship between the rCBF-ASL, rSI-ASL, rCBV and rCBF ratios and grade of gliomas. Their cut-off values permitting best discrimination was calculated. The correlation between rCBV, rCBF, rSI-ASL and rCBF-ASL and glioma grade was assessed using Spearman correlation analysis. ResultsThere was a statistically significant difference between low and high-grade tumors for all parameters. Correlation analyses revealed significant positive correlations between rCBV and rCBF-ASL (r=0.81, p<0.001). However correlation between rCBF and rCBF-ASL was weaker (r=0.64, p<0.001). ConclusionArterial spin labeling is an employable imaging technique for evaluating tumor perfusion non-invasively and may be useful in differentiating high and low grade gliomas.

Abstract 181: MR Oxygen Metabolic Index (OMI) Thresholds for Delineating Core, Penumbra, and Oligemia in Acute Ischemic Stroke Patients

Background: PET cerebral oxygen metabolic rate (CMRO 2 ) provides a measure of tissue viability during acute ischemic stroke. Oxygen metabolic index (OMI), an MR-derived parameter closely related to CMRO 2 , was developed as a more accessible imaging approach for acute stroke patients. Methods: 38 acute ischemic stroke patients were imaged at 3.0 hours (tp1), 6.2 hours (tp2), and 1 month (tp3) after onset. Dynamic susceptibility contrast method measured CBF. An asymmetry spin echo sequence was used to calculate OEF; OMI=CBFxOEF. Co-registered voxels were normalized to the non-ischemic hemisphere. Two OMI thresholds to distinguish core from penumbra and penumbra from oligemia were derived by separating brain tissue into 4 groups: (1) tissue that died regardless of reperfusion ( core ); (2) tissue that died without reperfusion ( nonreperfused_penumbra ); (3) tissue that survived with reperfusion ( reperfused_penumbra ); and (4) tissue that survived regardless of reperfusion ( oligemia ). An exhaustive search method was used to determine an optimal pair of core/penumbra and penumbra/oligemia thresholds for each patient by minimizing the “average prediction error (APE)”, a metric averaging the differences for each tissue group’s actual infarct probability (IP) from the ideal IP (Table). The predictive abilities of the thresholds were tested in the same cohort using “leave-one-out” cross-validation, and the APE averaged across the population. Results: The core/penumbra OMI threshold and the penumbra/oligemia OMI threshold ranged from 0.21-0.22 and 0.41-0.43, respectively. The median IP’s [IQR] for the 4 tissue groups are shown (Table). The population averaged APE was 15% [5%, 24%]. Conclusions: OMI thresholds delineated the ischemic penumbra with high predictive ability: reperfused penumbra demonstrated low IP (6.79%), while non-reperfused penumbra demonstrated high IP (73.57%). These thresholds will require further testing in independent patient cohorts.

Abstract 2337: Apparent Diffusion Coefficient (ADC) Signal Maturation: Rates Of ADC Decline Depend On Severity Of Perfusion Deficit During Hyperacute Ischemic Stroke

Background: While it is known that a reduction of blood flow leads to a decrease in apparent diffusion coefficient (ADC), how ADC evolves as a function of time from ischemia onset is unclear. We evaluated ADC signal change in brain tissue with temporally stable hypoperfusion, examining the relationship between severity of hypoperfusion and the rate of ADC decline during acute ischemia. Methods: Ischemic stroke patients were sequentially imaged with diffusion-perfusion weighted imaging at &lt;4.5hr (tp1) and at 6hr (tp2) after stroke onset, to directly assess the temporal evolution of ADC. One month FLAIR provided the final infarct region. Registration aligned all images for each patient. Dynamic susceptibility contrast method allowed calculation of mean transit time (MTT). Hypoperfusion was defined as tissue with MTT &gt; 4sec + the contralateral median MTT. In tissue with stable hypoperfusion on tp1 and tp2, ADC regions of interest (ROIs) with normal or moderate reduction on tp1 were evaluated. To avoid capturing tp1 ADC voxels that had already maximally declined (floor effect, &lt;30 ×10 -5 mm 2 /s), ADC values &lt; 60 were excluded. To assess how ADC declined with varying degrees of hypoperfusion, tissue was divided into 6 MTT ranges: 3-6 (ROI1), 6-9 (ROI2), 9-12 (ROI3), 12-15 (ROI4), 15-18 (ROI5) and &gt;18 (ROI6) seconds. Paired t-tests compared tp1 and tp2 ROIs for each patient. Infarct probability based on tp3 FLAIR was computed for each ROI. Results: 43 patients were imaged at 2.9 (tp1) and 6.4 hrs (tp2) after stroke onset, of which 37 returned for 1 month FLAIR. The 6 ROIs with increasing MTT severity were found in 41, 27, 19, 12, 6, and 10 patients for ROI’s 1-6, respectively. ADC values for all ROIs were similar at tp1 (near normal), despite different tp1 MTT. For ROI1-3, ADC values did not decline between tp1 and tp2 or decreased mildly (ROI3, P=0.079). For severe hypoperfusion, ADC decreased significantly: ROI4 (p=0.006), ROI5 (P=0.038), and ROI6 (P=0.0001). Using linear regression to approximate the ADC decline, the slopes were significantly different from zero with ADC decay rates of -1.87×10 -5 mm 2 /s/hr (R=0.58), -2.86×10 -5 mm 2 /s/hr (R=0.65) and -4.51×10 -5 mm 2 /s /hr (R=0.82) for ROI4-6, respectively ( Figure ). The median infarct probabilities for the 6 ROI’s increased with increasing MTT severity: 16%, 53%, 57%, 87%, 100%, and 90% for ROI1-6, respectively. Conclusions: ADC remained normal after ischemic stroke in regions with stable, moderate hypoperfusion. In contrast, with stable, severe hypoperfusion (MTT&gt;12s), ADC decreased from 3-6 hours and the rate of decline was highly dependent on the degree of hypoperfusion.

Abstract 2636: Magnetic Resonance Oxygen Metabolic Index Distinguishes infarct from peri-infarct tissue better than ADC and PWI In hyperacute ischemic Stroke Patients

Background: Diffusion (DWI) and perfusion weighted imaging (PWI) have been extensively studied to delineate irreversibly-injured tissue (that will progress to infarct) from reversibly-injured tissue (that will remain viable). An MR-based method, oxygen metabolism index (MROMI), may provide relevant metabolic information critical for determining tissue viability. We compared the ability of hyperacute MROMI, mean transit time (MTT), and apparent diffusion coefficient (ADC) to distinguish brain tissue that infarcted one month later from an initially hypoperfused region that survived, and contralateral mirror brain regions. Methods: Ischemic stroke patients were imaged at &lt;4.5hr and at 1 month after stroke onset. Dynamic susceptibility contrast method measured cerebral blood flow (CBF) and MTT. An asymmetric spin echo sequence measured oxygen extraction fraction (OEF). MROMI=CBF x OEF. Co-registration and segmentation aligned images and separated gray from white matter, respectively. Hypoperfusion was defined as tissue with MTT &gt; 4sec + the contralateral median MTT. Three ROIs were defined: (1) ROI Infarct (final infarct as manually outlined on the 1month FLAIR); (2) ROI Peri (acutely hypoperfused, but not included in the final infarct); and (3) ROI Mirror (the contralateral mirror region of the ROI Infarct . Each patient’s ROIs were normalized (n) to the contralateral hemisphere as follows: nMTT= MTT-contralateral median MTT, nADC= ADC/contralateral median ADC, and nMROMI=MROMI/contralateral median MROMI. nMROMI was calculated in gray and white matter separately. The 3 ROI’s were compared for nMROMI, nMTT and nADC using the Kruskal-Wallis test with Dunn’s post-tests. Results: 25 patients were imaged at 2.9 ± 0.7 hrs and 1 month after stroke onset. Mean values for nMTT, nADC, and nMR-OMI were obtained for the 3 ROI’s (ROI Infarct ROI Peri and ROI Mirror ) for each patient. Significant differences were found between ROI Infarct and ROI Mirror (P&lt;0.001) for all three parameters (nMTT, nADC and nMROMI). However, only nMROMI demonstrated a significant difference between ROI Infarct and ROI Mirror (P&lt;0.05) ( Figure ). Both nMTT and nADC values in ROI Infarct varied greatly across patients and no significant differences between ROI Infarct and ROI Peri were found. Conclusions: Identifying tissue that would die from hypoperfused but survived tissue is challenging during acute ischemia. Our results have demonstrated that hyperacute MROMI show significant differences between these two regions, while MTT and ADC did not, likely due to high inter-individual variability using the latter parameters.

SCALE-PWI: A Pulse Sequence for Absolute Quantitative Cerebral Perfusion Imaging

The Bookend technique is a magnetic resonance imaging (MRI) dynamic susceptibility contrast method that provides reliable quantitative measurement of cerebral blood flow (CBF) and cerebral blood volume (CBV). The quantification is patient specific, is derived from a steady-state measurement of CBV, and is obtained from T(1) changes in the white matter and the blood pool after contrast agent injection. In the current implementation, the Bookend technique consists of three scanning steps requiring a cumulative scan time of 3 minutes 47 seconds, a well-trained technologist, and extra time for offline image reconstruction. We present an automation and acceleration of the multiscan Bookend protocol through a self-calibrating pulse sequence, namely Self-Calibrated Epi Perfusion-Weighted Imaging (SCALE-PWI). The SCALE-PWI is a single-shot echo-planar imaging pulse sequence with three modules and a total scan time of under 2 minutes. It provides the possibility of performing online, quantitative perfusion image reconstruction, which reduces the latency to obtain quantitative maps. A validation study in healthy volunteers (N=19) showed excellent agreement between SCALE-PWI and the conventional Bookend protocol (P>0.05 with Student's t-test, r=0.95/slope=0.98 for quantitative CBF, and r=0.91/slope=0.94 for quantitative CBV). A single MRI pulse sequence for absolute quantification of cerebral perfusion has been developed.

Contribution of perfusion-weighted magnetic resonance imaging in the differentiation of meningiomas and other extra-axial tumors: case reports and literature review

We present six cases of extra-axial lesions: three meningiomas [including one intraventricular and one cerebellopontine angle (CPA) meningioma], one dural metastasis, one CPA schwannoma and one choroid plexus papilloma which were chosen from a larger cohort of extra-axial tumors evaluated in our institution. Apart from conventional MR examinations, all the patients also underwent perfusion-weighted imaging (PWI) using dynamic susceptibility contrast method on a 1.5 T MR unit (contrast: 0.3 mmol/kg, rate 5 ml/s). Though the presented tumors showed very similar appearance on conventional MR images, they differed significantly in perfusion examinations. The article draws special attention to the usefulness of PWI in the differentiation of various extra-axial tumors and its contribution in reaching final correct diagnoses. Finding a dural lesion with low perfusion parameters strongly argues against the diagnosis of meningioma and should raise a suspicion of a dural metastasis. In cases of CPA tumors, a lesion with low relative cerebral blood volume values should be suspected to be schwannoma, allowing exclusion of meningioma to be made. In intraventricular tumors arising from choroid plexus, low perfusion parameters can exclude a diagnosis of meningioma. In our opinion, PWI as an easy and quick to perform functional technique should be incorporated into the MR protocol of all intracranial tumors including extra-axial neoplasms.

Automated detection of arterial input function in DSC perfusion MRI in a stroke rat model

Quantitative cerebral blood flow (CBF) estimation requires deconvolution of the tissue concentration time curves with an arterial input function (AIF). However, image-based determination of AIF in rodent is challenged due to limited spatial resolution. We evaluated the feasibility of quantitative analysis using automated AIF detection and compared the results with commonly applied semi-quantitative analysis. Permanent occlusion of bilateral or unilateral common carotid artery was used to induce cerebral ischemia in rats. The image using dynamic susceptibility contrast method was performed on a 3-T magnetic resonance scanner with a spin-echo echo-planar-image sequence (TR/TE = 700/80 ms, FOV = 41 mm, matrix = 64, 3 slices, SW = 2 mm), starting from 7 s prior to contrast injection (1.2 ml/kg) at four different time points. For quantitative analysis, CBF was calculated by the AIF which was obtained from 10 voxels with greatest contrast enhancement after deconvolution. For semi-quantitative analysis, relative CBF was estimated by the integral divided by the first moment of the relaxivity time curves. We observed if the AIFs obtained in the three different ROIs (whole brain, hemisphere without lesion and hemisphere with lesion) were similar, the CBF ratios (lesion/normal) between quantitative and semi-quantitative analyses might have a similar trend at different operative time points. If the AIFs were different, the CBF ratios might be different. We concluded that using local maximum one can define proper AIF without knowing the anatomical location of arteries in a stroke rat model.

Functional magnetic resonance imaging of alprazolam-induced changes in humans with familial alcoholism

This study sought to identify whether subjects with a family history (FH+) of alcoholism had changes in regional cerebral blood volume (rCBV) after an alprazolam challenge which distinguished them from subjects without a family history (FH−) of alcoholism using functional MRI (fMRI). Twelve FH+and eight FH−subjects were challenged with 1 mg of alprazolam or placebo in a double-blind crossover design. FMRI scans were obtained at baseline, 1 and 2 h after the challenge using the dynamic susceptibility contrast method with gadolinium. Mood scales, the Tufts Addiction Research Center Inventory-Morphine Benzedrine Group Scale and the drug liking scale, were administered every 30 min to assess drug effects. Global analysis of CBV showed a treatment by time decrease on alprazolam relative to placebo, but no effect by family history. The FH+ group showed rCBV decreases at 1 h in the left caudate and left inferior prefrontal region, while the FH−group showed rCBV decreases at 2 h in the right inferior prefrontal region and anterior cingulate in response to alprazolam relative to placebo. FH+subjects reported more mood enhancement with alprazolam. This fMRI technique detected global and regional CBV changes induced by alprazolam. The location and rate of alprazolam-induced rCBV changes differed between FH+and FH−subjects. These changes may be related to the increased mood enhancement found in subjects genetically predisposed to alcoholism.

Dynamic susceptibility contrast MRI of regional cerebral blood volume in Alzheimer's disease

The purpose of this study was to investigate the potential effectiveness of dynamic susceptibility contrast magnetic resonance imaging (MRI) to discriminate elderly patients with Alzheimer's disease from normal matched comparison subjects. Images of regional cerebral blood volume (CBV) were generated from echo-planar MRI with the dynamic susceptibility contrast method in 13 Alzheimer's disease patients and 13 comparison subjects group-matched on age and gender. Temporoparietal cerebral blood volume, expressed as a percentage of the cerebellum value, was reduced 17% bilaterally in the patients with Alzheimer's disease. Blood volume in sensorimotor regions was reduced only 8.5% in the patients. Discriminant function analysis based on left and right temporoparietal measures correctly classified 88.5% of the subjects as patients or comparison subjects. Temporoparietal CBV was reduced even in mildly affected Alzheimer's disease patients (Mini-Mental State scores > 24). Dynamic susceptibility contrast MRI of regional CBV is promising as a nonradioactive, potentially lower-cost alternative to other functional neuroimaging methods for evaluating Alzheimer's disease.