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Arterial spin labeling (ASL) is a noninvasive imaging technique that labels the proton spins in arterial blood and uses them as endogenous tracers. Brain perfusion imaging with ASL is becoming increasingly common in clinical practice, and clinical applications of ASL for intracranial magnetic resonance angiography (MRA) have also been demonstrated. Unlike computed tomography (CT) angiography and cerebral angiography, ASL-based MRA does not require contrast agents. ASL-based MRA overcomes most of the disadvantages of time-of-flight (TOF) MRA. Several schemes have been developed for ASL-based MRA; the most common method has been pulsed ASL, but more recently pseudo-continuous ASL, which provides a higher signal-to-noise ratio (SNR), has been used more frequently. New methods that have been developed include direct intracranial labeling methods such as velocity-selective ASL and acceleration-selective ASL. MRA using an extremely short echo time (eg, silent MRA) or ultrashort echo-time (TE) MRA can suppress metal susceptibility artifacts and is ideal for patients with a metallic device implanted in a cerebral vessel. Vessel-selective 4D ASL MRA can provide digital subtraction angiography (DSA)-like images. This review highlights the principles, clinical applications, and characteristics of various ASL-based MRA techniques. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 2., (© 2023 International Society for Magnetic Resonance in Medicine.)

Purpose: Two major drawbacks of 4D-MR angiography based on superselective pseudo-continuous arterial spin labeling combined with CENTRA-keyhole and view-sharing (4D-S-PACK) are the low temporal resolution and long scanning time. We investigated the feasibility of increasing the temporal resolution and accelerating the scanning time on 4D-S-PACK by using CS-SENSE and PhyZiodynamics, a novel image-processing program that interpolates images between phases to generate new phases and reduces image noise., Methods: Seven healthy volunteers were scanned with a 3.0 T MR scanner to visualize the internal carotid artery (ICA) system. PhyZiodynamics is a novel image-processing that interpolates images between phases to generate new phases and reduces image noise, and by increasing temporal resolution using PhyZiodynamics, inflow dynamic data (reference) were acquired by changing the labeling durations (100-2000 msec, 31 phases) in 4D-S-PACK. From this set of data, we selected seven time intervals to calculate interpolated time points with up to 61 intervals using ×10 for the generation of interpolated phases with PhyZiodynamics. In the denoising process of PhyZiodynamics, we processed the none, low, medium, high noise reduction dataset images. The time intensity curve (TIC), the contrast-to-noise ratio (CNR) were evaluated. In accelerating with CS-SENSE for 4D-S-PACK, 4D-S-PACK were scanned different SENSE or CS-SENSE acceleration factors: SENSE3, CS3-6. Signal intensity (SI), CNR, were evaluated for accelerating the 4D-S-PACK. With regard to arterial vascular visualization, we evaluated the middle cerebral artery (MCA: M1-4 segments)., Results: In increasing temporal resolution, the TIC showed a similar trend between the reference dataset and the interpolated dataset. As the noise reduction weight increased, the CNR of the interpolated dataset were increased compared to that of the reference dataset. In accelerating 4D-S-PACK, the SI values of the SENSE3 dataset and CS dataset with CS3-6 were no significant differences. The image noise increased with the increase of acceleration factor, and the CNR decreased with the increase of acceleration factor. Significant differences in CNR were observed between acceleration factor of SENSE3 and CS6 for the M1-4 (P < 0.05). Visualization of small arteries (M4) became less reliable in CS5 or CS6 images. Significant differences were found for the scores of M2, M3 and M4 segments between SENSE3 and CS6., Conclusion: With PhyZiodynamics and CS-SENSE in 4D-S-PACK, we were able to shorten the scan time while improving the temporal resolution., (Copyright © 2023. Published by Elsevier Inc.)

Background and Purpose: An accurate assessment of the hemodynamics of an intracranial dural AVF is necessary for treatment planning. We aimed to investigate the utility of 4D-MRA based on superselective pseudocontinuous arterial spin-labeling with CENTRA-keyhole and view-sharing (4D-S-PACK) for the vessel-selective visualization of intracranial dural AVFs., Materials and Methods: We retrospectively analyzed the images of 21 patients (12 men and 9 women; mean age, 62.2 [SD,19.2] years) with intracranial dural AVFs, each of whom was imaged with DSA, 4D-S-PACK, and nonselective 4D-MRA based on pseudocontinuous arterial spin-labeling combined with CENTRA-keyhole and view-sharing (4D-PACK). The shunt location, venous drainage patterns, feeding artery identification, and Borden classification were evaluated by 2 observers using both MRA methods on separate occasions. Vessel selectivity was evaluated on 4D-S-PACK., Results: Shunt locations were correctly evaluated in all 21 patients by both observers on both MRA methods. With 4D-S-PACK, observers 1 and 2 detected 76 (80.0%, P  < .001) and 73 (76.8%, P  < .001) feeding arteries of the 95 feeding arteries identified on DSA but only 39 (41.1%) and 46 (48.4%) feeding arteries with nonselective 4D-PACK, respectively. Both observers correctly identified 10 of the 11 patients with cortical venous reflux confirmed by DSA with both 4D-S-PACK and 4D-PACK (sensitivity = 90.9%, specificity = 90.9% for each method), and they made accurate Borden classifications in 20 of the 21 patients (95.2%) on both MRA methods. Of the 84 vessel territories examined, vessel selectivity was graded 3 or 4 in 73 (91.2%) and 66 (88.0%) territories by observers 1 and 2, respectively., Conclusions: 4D-S-PACK is useful for the identification of feeding arteries and accurate classifications of intracranial dural AVFs and can be a useful noninvasive clinical tool., (© 2022 by American Journal of Neuroradiology.)

Purpose: This study investigated the optimal labeling position and gradient moment for 4D-MR angiography based on superselective pseudo-continuous arterial spin labeling combined with CENTRA-keyhole and view-sharing (4D-S-PACK) for vessel-selective flow visualization of the internal carotid artery (ICA) and vertebrobasilar artery (VBA) systems., Methods: Seven healthy volunteers were scanned with a 3.0 T MR scanner. To visualize the ICA system, the labeling focus was placed in the right ICA at 55, 75 and 95 mm below the imaging slab. To visualize the VBA system, the labeling focus was placed in the basilar artery (BA), upper vertebral artery (VA upper), and lower vertebral artery (VA lower). Two sizes of labeling focus were created using gradient moments of 0.5 and 0.75 mT/m ms. The contrast-to-noise ratio (CNR) was measured in the middle cerebral artery (MCA) and posterior cerebral artery (PCA) branches., Results: CNRs increased as the distance between the center of the imaging slab and the labeling position decreased in all MCA segments. CNRs obtained with VA lower tended to be higher than those obtained with BA and VA upper in all PCA segments. Selective vessel visualization was achieved with the gradient moment of 0.75 mT/m ms for the ICA and VBA system., Conclusion: The optimal 4D-S-PACK gradient moment was found to be 0.75 mT/m ms for the ICA and VBA systems. When visualizing the ICA system, the labeling position should be placed as close as possible to the imaging slab. When visualizing the VBA system, the labeling position should be placed at VA lower ., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objectives: To evaluate the usefulness of 4D-MR angiography based on super-selective pseudo-continuous ASL combined with keyhole and view-sharing (4D-S-PACK) for vessel-selective visualization and to examine the ability of this technique to visualize brain arteriovenous malformations (AVMs)., Methods: In this retrospective study, 15 patients (ten men and five women, mean age 44.0 ± 16.9 years) with brain AVMs were enrolled. All patients were imaged with 4D-PACK (non-selective), 4D-S-PACK, and digital subtraction angiography (DSA). Observers evaluated vessel selectivity, identification of feeding arteries and venous drainage patterns, visualization scores, and contrast-to-noise ratio (CNR) for each AVM component. Measurements were compared between the MR methods., Results: Vessel selectivity was graded 4 in 43/45 (95.6%, observer 1) and 42/45 (93.3%, observer 2) territories and graded 3 in two (observer 1) and three (observer 2) territories. The sensitivity and specificity for identification of feeding arteries for both observers was 88.9% and 100% on 4D-PACK, and 100% and 100% on 4D-S-PACK, respectively. For venous drainage, the sensitivity and specificity was 100% on both methods for observer 1. The sensitivity and specificity for observer 2 was 94.4% and 83.3% on 4D-PACK, and 94.4% and 91.7% on 4D-S-PACK, respectively. The CNRs at the timepoint of 1600 ms were slightly lower in 4D-S-PACK than in 4D-PACK for all AVM components (Feeding artery, p = .02; nidus, p = .001; and draining artery, p = .02). The visualization scores for both observers were not significantly different between 4D-PACK and 4D-S-PACK for all components., Conclusions: 4D-S-PACK could be a useful non-invasive clinical tool for assessing hemodynamics in brain AVMs., Key Points: • The 4D-MR angiography based on super-selective pseudo-continuous arterial spin labeling combined with CENTRA-keyhole and view-sharing (4D-S-PACK) enabled excellent vessel selectivity. • The 4D-S-PACK enabled the perfect identification of feeding arteries of brain arteriovenous malformation (AVM). • 4D-S-PACK could be a non-invasive clinical tool for assessing hemodynamics in brain AVMs.

Purpose: Four-dimensional magnetic resonance angiography (4D-MRA) based on super-selective pseudo-continuous arterial spin labeling, combined with Keyhole and View-sharing (4D-S-PACK) was introduced for scan-accelerated vessel-selective 4D-MRA. Label selectivity and visualization effectiveness were assessed., Methods: Nine healthy volunteers were included in the study. The label selectivity for the imaging of internal carotid artery (ICA) and external carotid artery (ECA) circulation was assessed qualitatively. The contrast-to-noise ratio (CNR) in 4D-S-PACK was measured in four middle cerebral artery (MCA) and superficial temporal artery (STA) segments and compared with that in contrast-inherent inflow-enhanced multi-phase angiography combined with the vessel-selective arterial spin labeling technique (CINEMA-select). Vessel-selective arterial visualization in 4D-S-PACK was assessed qualitatively in a patient with dural arteriovenous fistula and compared with digital subtraction angiography (DSA) and non-vessel selective 4D-PACK., Results: 4D-S-PACK vessel selectivity was judged to be at a clinically acceptable level in all cases except one ECA-targeted label. The CNR was significantly higher using 4D-S-PACK compared with CINEMA-select in MCA and STA peripheral segments (p < 0.001). In patient examination, territorial flow visualization in feeding artery and draining vein circulation on 4D-S-PACK were comparable with that on DSA and the identification of such responsible vessels was easier on 4D-S-PACK than on 4D-PACK., Conclusion: 4D-S-PACK showed high vessel-selectivity and higher visualization effectiveness compared with CINEMA-select. One clinical case was performed and ICA and ECA territorial flow was successfully visualized separately, suggesting clinical usefulness., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Purpose: To evaluate the performance of acceleration-selective arterial spin labeling (AccASL) MR angiography in the visualization of brain arteriovenous malformations (AVMs) in comparison with digital subtraction angiography (DSA) and time-of-flight (TOF) MR angiography., Methods: Twenty-one patients with brain AVM (mean age 31.1 ± 18.6 years; 11 males, 10 females) underwent TOF and AccASL MR angiography and DSA. Two neuroradiologists conducted an observer study for detection, nidus size, eloquence, venous drainage pattern, and Spetzler-Martin (SM) grade. The evaluations included the visualization of each AVM component with reference to DSA and assessments of contrast-to-noise ratio (CNR). The kappa statistic, repeated measures analysis of variance, Wilcoxon matched pairs test, and paired t test were used., Results: Both observers detected more AVMs with AccASL (95.2%, 90.5% for Observers 1 and 2) than with TOF (76.2% and 71.4%, respectively). The inter-modality agreement between AccASL and DSA was almost perfect for the eloquence, venous drainage pattern, and SM grade for Observer 1 and moderate for the venous drainage pattern and substantial for the eloquence and SM grade for Observer 2. The visualization scores were higher with AccASL than with TOF for the feeding artery (AccASL, 4.5 ± 1.0 vs. TOF, 3.9 ± 1.5, p = 0.0214), nidus (4.6 ± 1.1 vs. 3.2 ± 1.5, p = 0.0006), and draining vein (4.6 ± 1.0 vs. 2.2 ± 1.1, p < 0.0001), respectively. The CNRs in the nidus were higher in AccASL than in TOF (29.9 ± 16.7 vs. 20.8 ± 16.5, p = 0.0002), as in the draining vein (23.2 ± 13.0 vs. 12.6 ± 12.0, p = 0.0010), respectively., Conclusions: AccASL better visualized brain AVMs compared with TOF and was useful for grading without the use of contrast agents.

Purpose: A new sequence for intracranial MRA is developed, named enhanced acceleration-selective arterial spin labeling (eAccASL), to improve main artery visualization at middle cerebral artery (MCA). The aim of this study is to assess the visualization improvement using eAccASL, compared with the previously developed AccASL., Methods: eAccASL and AccASL were performed in 8 healthy volunteers and images were compared between the 2 sequences. One patient with Moyamoya disease was evaluated by eAccASL and time of flight. For the volunteer images, vessel visualization was assessed by measuring the contrast-to-noise ratio between MCA M1 to M4 and white matter and by counting the peripheral arteries. Venous artifact level was assessed by measuring the contrast-to-noise ratio between the confluence of the sinuses and white matter and by evaluating cortical vein visualization. For the patient images, qualitative assessment of peripheral and collateral vessel visualization was conducted., Results: In the MCA main trunk, higher arterial signal intensity, with reduced flow void, was observed in eAccASL compared with AccASL. Contrast-to-noise ratios of M1 to M3 for eAccASL were significantly higher than those of AccASL. There was no significant difference between AccASL and eAccASL for venous artifact., Conclusion: eAccASL could produce better MCA main trunk visualization compared with AccASL, while maintaining good venous signal suppression., (© 2018 International Society for Magnetic Resonance in Medicine.)

Objectives: To evaluate the performance of four-dimensional pseudo-continuous arterial spin labeling (4D-pCASL)-based angiography using CENTRA-keyhole and view sharing (4D-PACK) in the visualization of flow dynamics in distal cerebral arteries and leptomeningeal anastomosis (LMA) collaterals in moyamoya disease in comparison with contrast inherent inflow-enhanced multiphase angiography (CINEMA), with reference to digital subtraction angiography (DSA)., Methods: Thirty-two cerebral hemispheres from 19 patients with moyamoya disease (mean age, 29.7 ± 19.6 years; five males, 14 females) underwent both 4D-MR angiography and DSA. Qualitative evaluations included the visualization of anterograde middle cerebral artery (MCA) flow and retrograde flow via LMA collaterals with reference to DSA. Quantitative evaluations included assessments of the contrast-to-noise ratio (CNR) on these vessels. The linear mixed-effect model was used to compare the 4D-PACK and CINEMA methods., Results: The vessel visualization scores were significantly higher with 4D-PACK than with CINEMA in the visualization of anterograde flow for both Observer 1 (CINEMA, 3.53 ± 1.39; 4D-PACK, 4.53 ± 0.80; p < 0.0001) and Observer 2 (CINEMA, 3.50±1.39; 4D-PACK, 4.31 ± 0.86; p = 0.0009). The scores were higher with 4D-PACK than with CINEMA in the visualization of retrograde flow for both Observer 1 (CINEMA, 3.44 ± 1.05; 4D-PACK, 4.47 ± 0.88; p < 0.0001) and Observer 2 (CINEMA, 3.19 ± 1.20; 4D-PACK, 4.38 ± 0.91; p < 0.0001). The maximum CNR in the anterograde flow was higher in 4D-PACK (40.1 ± 16.1, p = 0.0001) than in CINEMA (27.0 ± 16.6). The maximum CNR in the retrograde flow was higher in 4D-PACK (36.1 ± 10.0, p < 0.0001) than in CINEMA (15.4 ± 8.0)., Conclusions: The 4D-PACK provided better visualization and higher CNRs in distal cerebral arteries and LMA collaterals compared with CINEMA in patients with this disease., Key Points: • The 4D-PACK enables good visualization of distal cerebral arteries in moyamoya disease. • The 4D-PACK enables direct visualization of leptomeningeal collateral vessels in moyamoya disease. • Vessel visualization by 4D-PACK can be useful in assessing cerebral hemodynamics.

Objectives: ASL is useful in evaluating tumour blood flow and in detecting hypervascular tumours. The purpose of this study was to assess the additive value of ASL to non-contrast and contrast-enhanced (NC/CE)-T1WI for diagnosing residual or recurrent meningiomas., Methods: This retrospective study included 25 postoperative patients (20 women, 5 men; median age, 65 [32-85] years) with and 25 gender- and age-matched postoperative patients without residual or recurrent meningiomas. ASL was performed using a pseudocontinuous method. Seven independent observers (two radiology residents, two general radiologists and three neuroradiologists) participated in two reading sessions consisting of only NC/CE-T1WI (first session) or NC/CE-T1WI with ASL (second session). We evaluated the sensitivity and diagnostic performance for the detection of residual or recurrent meningiomas. The diagnostic performance was assessed using a figure of merit (FOM) calculated via jackknife free-response receiver-operating characteristics. Statistical analysis was performed with paired t tests, with a significance level of p < .05., Results: The sensitivities were as follows (NC/CE-T1WI vs. NC/CE-T1WI with ASL): residents (62.1% vs. 70.7%), general radiologists (75.9% vs. 87.9%), neuroradiologists (97.7% vs. 100%) and all observers (81.3% vs. 88.2%). The FOMs were as follows (NC/CE-T1WI vs. NC/CE-T1WI with ASL): residents (0.76 vs. 0.83), general radiologists (0.83 vs. 0.93), neuroradiologists (0.95 vs. 0.99) and all observers (0.86 vs. 0.93). The addition of ASL significantly improved the diagnostic parameters for all observers except neuroradiologists (p <. 05)., Conclusions: ASL improved the detection rate of residual or recurrent meningiomas on NC/CE-T1WI among both radiology residents and general radiologists., Key Points: • ASL improved diagnostic performance for residual/recurrent meningioma compare to NC/CE-T1WI alone. • Diagnostic sensitivity was increased after adding ASL compared with NC/CE-T1WI. • FOM was increased after adding ASL compared with NC/CE-T1WI.

Purpose: 4D dynamic MR angiography (4D-MRA) using pseudo-continuous arterial spin labeling (pCASL), combined with Keyhole and View-sharing (4D-PACK) for scan acceleration, is introduced. Its validity for arterial inflow dynamics visualization was investigated through comparison with 4D-pCASL and contrast inherent inflow enhanced multiphase angiography (CINEMA)., Methods: Six healthy volunteers were included in the study. The arterial transit time (ATT) in 4D-PACK was measured at multiple regions in middle cerebral artery (MCA), and Pearson's correlation coefficient with ATT in 4D-pCASL was calculated. The contrast-to-noise ratio (CNR) in 4D-PACK was measured in four MCA segments and compared with that in 4D-pCASL and CINEMA. Arterial visualization in 4D-PACK was assessed qualitatively in patients with moyamoya disease and arteriovenous malformation by comparing with CINEMA., Results: 4D-PACK achieved a 36% scan time reduction compared with 4D-pCASL. The correlation coefficient for ATT measured by 4D-pCASL and 4D-PACK was greater than 0.96. The CNR was significantly higher using 4D-PACK compared with CINEMA in the M4 segment (P < 0.01). In patient examinations, the flow in the collateral artery or draining vein was better visualized in 4D-PACK compared with CINEMA., Conclusion: 4D-PACK accelerates 4D-pCASL, shows similar inflow dynamics as 4D-pCASL and shows better peripheral visualization compared with CINEMA. Magn Reson Med 80:719-725, 2018. © 2018 International Society for Magnetic Resonance in Medicine., (© 2018 International Society for Magnetic Resonance in Medicine.)

Purpose: To evaluate cerebral blood flow (CBF) laterality derived from arterial spin labeling (ASL) in early-stage Parkinson's disease (PD) patients compared with those with advanced stages., Materials and Methods: Thirty-eight patients with PD (21 patients in early stages, 17 patients in advanced stages) were retrospectively studied. The CBF maps derived from 3T ASL data were co-registered to the corresponding 3DT1WI using SPM 12 software. Caudate nucleus (CN), putamen (PT), globus pallidus (GP), and thalamus (TH) were manually traced on the representative axial slices of 3DT1WI. CBF of the CN, PT, GP, and TH was measured using corresponding pixels on the co-registered CBF maps. A laterality index (LI) was calculated as the ratio of the contralateral CBF to primary affected side CBF. Each LI was compared between early and advanced stages of PD using the Mann-Whitney U-test. The LIs were also compared between each stage of PD., Results: In the CN, the LIs were significantly higher in early stages (mean LI ± SD, 95% confidence interval = 1.06 ± 0.14, 1.00-1.13) than in advanced stages (0.94 ± 0.14, 0.87-1.01; P < 0.05). We also observed a tendency toward decreased LIs with disease severity (1.10 ± 0.14, 0.99-1.21 for Hoehn and Yahr stage I; 1.04 ± 0.14, 0.92-1.12 for stage II; 0.96 ± 0.11, 0.89-1.10 for stage III; 0.93 ± 0.17, 0.81-1.05 for stage IV)., Conclusion: The evaluation of CBF laterality pattern in the CN using ASL may be useful for assessing the disease severity of PD patients., Level of Evidence: 3 J. MAGN. RESON. IMAGING 2017;45:1821-1826., (© 2016 International Society for Magnetic Resonance in Medicine.)

Purpose: A new approach for intracranial MR angiography (MRA) is introduced, using acceleration-selective arterial spin labeling (AccASL). The aim of this study was to investigate the arterial visualization and venous suppression using AccASL., Methods: Intracranial MRA images obtained by AccASL and time-of-flight (TOF) were compared in seven healthy volunteers and one patient with occlusion of the terminal portion of the left internal carotid artery. The volunteer images were assessed by measuring the contrast-to-noise ratio (CNR) between the middle cerebral artery (MCA) and white matter (WM) and between the confluence of sinuses and WM. Additionally, visualized peripheral arteries were counted and qualitative scoring of the MCA visualization and vein signal contamination was conducted., Results: The CNR at the M4 branch and the number of visualized arteries was significantly higher using AccASL compared with that in TOF (P < 0.05). In the qualitative comparison, the score for artery visualization was higher using AccASL (P < 0.05), while minimizing signal contamination by cortical veins. Additionally, in patient examination, the collateral flow visualization was better with AccASL., Conclusion: AccASL enables better efficiency for visualizing peripheral arteries compared with TOF, while suppressing cortical vein signal. Magn Reson Med 77:1996-2004, 2017. © 2016 International Society for Magnetic Resonance in Medicine., (© 2016 International Society for Magnetic Resonance in Medicine.)

Background: Heterogeneity of arterial transit time due to cerebral artery steno-occlusive lesions hampers accurate regional cerebral blood flow measurement by arterial spin labeling (ASL)., Purpose: To assess the feasibility of regional cerebral blood flow measurement by ASL with multiple-delay time sampling in patients with steno-occlusive diseases by comparing with positron emission tomography (PET), and to determine whether regional arterial transit time measured by this ASL technique is correlated with regional mean transit time, a PET index of perfusion pressure., Material and Methods: Sixteen patients with steno-occlusive diseases received both ASL and (15)O-PET. The mean regional cerebral blood flow measured by ASL and PET, regional arterial transit time by ASL, and regional mean transit time by PET were obtained by a region-of-interest analysis. Correlation between regional cerebral blood flow by ASL and that by PET, and correlation between regional arterial transit time by ASL and regional mean transit time by PET were tested using Pearson's correlation coefficient for both absolute and relative values. A multivariate regression analysis was performed to test whether regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling the effect of regional cerebral blood flow by ASL., Results: A significant positive correlation was found between regional cerebral blood flow by ASL and that by PET for both absolute (r = 0.520, P < 0.0001) and relative (r = 0.691, P < 0.0001) values. A significant positive correlation was found between regional arterial transit time by ASL and regional mean transit time by PET both for absolute (r = 0.369, P = 0.0002) and relative (r = 0.443, P < 0.0001) values. The regression analysis revealed that regional arterial transit time by ASL was a significant contributor in modeling regional mean transit time by PET after controlling regional cerebral blood flow by ASL (P = 0.0011)., Conclusion: The feasibility of regional cerebral blood flow measurement using ASL with multiple-delay time sampling was confirmed in patients with cerebral artery steno-occlusive diseases. Moreover, it was suggested that mapping of regional arterial transit time has the potential to detect hemodynamic impairment.

Introduction: Hemangioblastoma and metastatic tumors are the major differential diagnoses for the posterior fossa tumors in adults. Our purpose was to evaluate the efficacy of ASL in differentiating hemangioblastomas from metastatic brain tumors., Methods: A total of 19 patients including 5 with a hemangioblastomas and 14 with metastatic tumors (7 from lung cancer, 4 from breast cancer, 1 from RCC, 1 from gastric cancer, and 1 from unknown origin) were enrolled in this study. ASL was performed using a pulsed ASL method at a 3-T unit. aTBF was measured as a mean absolute blood flow value within a region of interest drawn in the tumor. In addition, rTBF was obtained by normalizing the aTBF by a blood flow measured in the normal-appearing cortical gray matter. The aTBF and rTBF values were compared between hemangioblastomas and metastatic tumors using Student's t test., Results: Both the aTBF and rTBF values were significantly higher in hemangioblastomas (mean aTBF ± SD = 437 ± 274 mL/100 g/min, mean rTBF ± SD = 7.96 ± 3.12) in comparison with metastatic brain tumors (mean aTBF ± SD = 125 ± 134 mL/100 g/min, mean rTBF ± SD = 2.98 ± 3.91; p < 0.05, respectively). However, a metastasis from RCC showed very high aTBF (559 mL/100 g/min) and rTBF (16.2)., Conclusion: Our results demonstrated that ASL provides useful information to differentiate between hemangioblastomas and metastatic brain tumors. Metastasis from RCC may mimic hemangioblastoma on ASL blood flow measurement.

Purpose: To test the feasibility of ultra-short echo time (UTE) MRI for assessment of regional pulmonary ventilation/perfusion in a standard 3 Tesla clinical MRI system., Materials and Methods: MRI of the lungs was conducted with an optimized three-dimensional UTE sequence in normal rats and in a rat model of pulmonary embolism (PE) induced by a blood clot. Changes in signal intensities (SIs) due to inhalation of molecular oxygen or intravenous (i.v.) injection of Gd, which represents the distribution of ventilation and perfusion, respectively, were assessed in the lung parenchyma., Results: The UTE MRI with a TE of 100 μs could detect and map the changes in SI of the lung parenchyma due to the inhalation of 100% oxygen or i.v. injection of Gd in normal rats. Reduced T1 resulting from oxygen inhalation was also quantified. These changes were not observed on the images that were obtained simultaneously with a conventional range of TE (2.3 ms). Furthermore, the method could delineate the embolized lesions where the lung ventilation and perfusion were mismatched in a rat model with PE., Conclusion: These results show the feasibility and diagnostic potential of UTE MRI for the assessment of pulmonary ventilation and perfusion which is essential for the evaluation of a variety of lung diseases., (Copyright © 2011 Wiley-Liss, Inc.)

The purpose of this study was to determine whether arterial spin labelling (ASL) at 3-T MR imaging can be used to discriminate individuals with Alzheimer's disease (AD) from cognitively normal subjects. Twenty AD patients and 23 cognitively normal control subjects were studied using ASL on a 3-T MR imager. Absolute regional cerebral blood flow (rCBF) maps were calculated. In addition, normalized rCBF maps were obtained using CBF in the sensorimotor cortex for normalization. A voxel-wise comparison of these rCBF maps between the AD and control groups was performed using the two-sample t test. Individuals with AD were discriminated from control subjects based on mean rCBF values within a region-of-interest defined by the t test, and the discriminating performance was evaluated by the receiver operating characteristic (ROC) analysis. Comparisons of both absolute and normalized rCBF maps revealed areas of significant hypoperfusion caused by the effects of AD in the bilateral precunei and posterior cingulate gyri. ROC analyses resulted in area under the curve (AUC) values of 0.861 to 0.877 for absolute and 0.910 to 0.932 for normalized rCBF. Our results suggest that ASL at 3-T MR imaging can be used to help discriminate individuals with AD from normal subjects.

Purpose: Pulsed arterial spin labeling (PASL) is a magnetic resonance (MR) method for measuring cerebral blood flow. Although several validation studies for PASL in animals and humans have been reported, no reports have detailed the fundamental study of PASL using a flow phantom. We compared the true and theoretical flow rates in a flow phantom to confirm the analytical validity of quantitative perfusion imaging with Q2TIPS sequence., Methods: We built a flow phantom consisting of a 40-mm diameter plastic syringe filled with plastic beads and small plastic tubes 4 mm in diameter. Gd-DTPA-doped 8L water solution (0.1 mM) was circulated between the syringe and a tank through a plastic tube by a constant flow pump while the flow rate was adjusted between 0 and 2.61 cm/s. Q2TIPS sequence parameters were TI(1)=50 ms and TI(2)=1400 ms. Five imaging slices of 50 subtraction images were acquired sequentially in a distal-to-proximal direction using a single-shot echo planar imaging (EPI) technique. The theoretical flow rate calculated based upon the previously reported kinetic model for Q2TIPS was compared with the true flow rate., Results: A good linear relationship was observed between the theoretical, F', and true flow rates, F, in a flow rate range of 1.43 to 1.95 cm/s (F'=1.024*F-1.915, R(2)=0.902). The ratio of theoretical to true flow rate was 92 (+/-) 4%., Conclusion: Flow rate was quantified with reasonable accuracy when the entire amount of labeled bolus within the phantom could be recovered. Our experiment confirmed the analytical validity of Q2TIPS and suggested that blood flow measurement may be feasible using the Q2TIPS pulse sequence and kinetic model of the PASL equation.

Background and Purpose: In Moyamoya disease, the relationship between cerebral hemodynamics and angiographic findings has not been fully evaluated. The purpose of this study is to evaluate hemodynamics in Moyamoya disease with perfusion-weighted MR imaging (PWI) and cerebral angiography., Methods: Twenty patients with Moyamoya disease were the subjects. Mean transit time (MTT) derived from PWI was calculated in the medial frontal lobes, the posterior frontal lobes, the occipital lobes, and the basal ganglia. From the angiographies, we classified the degrees of internal carotid artery (ICA) and posterior cerebral artery (PCA) stenoses as well as the degrees of Moyamoya vessels and leptomeningeal anastomosis (LMA). MTT in each region was compared with the angiographic findings., Results: MTT positively correlated with the degree of ICA stenosis in the medial frontal (P < .01), posterior frontal (P < .001), and occipital (P < .001) lobes, as well as in the basal ganglia (P < .001). MTT correlated with the degree of PCA stenosis in the medial frontal (P < .001), posterior frontal (P < .001), and occipital (P < .001) lobes, as well as in the basal ganglia (P < .001). MTT correlated with the degree of Moyamoya vessels in the medial frontal (P < .05) and posterior frontal (P < .01) lobes. A multivariate analysis revealed that ICA and PCA stenoses and Moyamoya vessels were independent factors that prolonged MTT., Conclusion: Both ICA and PCA stenoses may influence overall cerebral perfusion in Moyamoya disease. The development of Moyamoya vessels may indicate hemodynamic impairment.