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Amide proton transfer-weighted (APTw) MR imaging shows promise as a biomarker of brain tumor status. Currently used APTw MRI pulse sequences and protocols vary substantially among different institutes, and there are no agreed-on standards in the imaging community. Therefore, the results acquired from different research centers are difficult to compare, which hampers uniform clinical application and interpretation. This paper reviews current clinical APTw imaging approaches and provides a rationale for optimized APTw brain tumor imaging at 3 T, including specific recommendations for pulse sequences, acquisition protocols, and data processing methods. We expect that these consensus recommendations will become the first broadly accepted guidelines for APTw imaging of brain tumors on 3 T MRI systems from different vendors. This will allow more medical centers to use the same or comparable APTw MRI techniques for the detection, characterization, and monitoring of brain tumors, enabling multi-center trials in larger patient cohorts and, ultimately, routine clinical use., (© 2022 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Recent evidence suggests that presupplementary motor area (pre-SMA) and inferior frontal gyrus (IFG) play an important role in response inhibition. However, no study has investigated the relationship between these brain networks at resting-state and response inhibition in obsessive-compulsive disorder (OCD). We performed resting-state functional magnetic resonance imaging scans and then measured the response inhibition of 41 medication-free OCD patients and 49 healthy control (HC) participants by using the stop-signal task outside the scanner. We explored the differences between OCD and HC groups in the functional connectivity of pre-SMA and IFG associated with the ability of motor response inhibition. OCD patients showed a longer stop-signal reaction time (SSRT). Compared to HC, OCD patients exhibit different associations between the ability of motor response inhibition and the functional connectivity between pre-SMA and IFG, inferior parietal lobule, dorsal anterior cingulate cortex, insula, and anterior prefrontal cortex. Additional analysis to investigate the functional connectivity difference from the seed ROIs to the whole brain voxels revealed that, compared to HC, OCD exhibited greater functional connectivity between pre-SMA and IFG. Also, this functional connectivity was positively correlated with the SSRT score. These results provide additional insight into the characteristics of the resting-state functional connectivity of the regions belonging to the cortico-striato-thalamo-cortical circuit and the cingulo-opercular salience network, underlying the impaired motor response inhibition of OCD. In particular, we emphasize the importance of altered functional connectivity between pre-SMA and IFG for the pathophysiology of motor response inhibition in OCD., (© 2021 The Authors. Human Brain Mapping published by Wiley Periodicals LLC.)

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.)

Purpose: To evaluate the visualization of CSF dynamics using the novel method multi-spin echo acquisition cine imaging (MUSACI)., Methods: MUSACI is based on multi-echo volume isotropic turbo spin-echo acquisition (VISTA) with pulse gating. MUSACI images were acquired in 11 healthy volunteers (7 men, 4 women; age range, 24-46 y, mean age, 31.9 ± 5.51 y). We compared the CSF signal intensities (SIs) at multiple values of the effective echo time (TE eff ) at the lateral ventricle, the foramen of Monro, the third ventricle, and the fourth ventricle. We compared the CSF SI changes in MUSACI at multiple TE eff and the mean velocities in phase contrast (PC) at each trigger delay at the foramen of Monro, the third ventricle, and the fourth ventricle., Results: The anterograde CSF motion from the aqueduct to the fourth ventricle, the retrograde motion from the aqueduct to the third ventricle, and the retrograde motion from the foramen of Monro to the lateral ventricle were observed with MUSACI. The CSF SIs at each TE eff in the foramen of Monro, the third ventricle, and the fourth ventricle were significantly lower than that at each TE eff in the lateral ventricle (P < 0.05). The CSF SI in MUSACI changed with the TE eff , and the CSF movements were observed at each trigger delay in PC., Conclusion: MUSACI can provide both high-resolution anatomical detail of the CSF passageways and physiologic information regarding CSF dynamics in a single scan., (© 2018 International Society for Magnetic Resonance in Medicine.)

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 assess the quantitative performance of three-dimensional (3D) fast spin-echo (FSE) Dixon amide proton transfer (APT) imaging of brain tumors compared with B 0 correction with separate mapping methods., Methods: Twenty-two patients with brain tumors (54.2 ± 18.7 years old, 12 males and 10 females) were scanned at 3 Tesla (T). Z-spectra were obtained at seven different frequency offsets at ±3.1 ppm, ± 3.5 ppm, ± 3.9 ppm, and -1560 ppm. The scan was repeated three times at +3.5 ppm with echo shifts for Dixon B 0 mapping. The APT image corrected by a three-point Dixon-type B 0 map from the same scan (3D-Dixon) or a separate B 0 map (2D-separate and 3D-separate), and an uncorrected APT image (3D-uncorrected) were generated. We compared the APT-weighted signals within a tumor obtained with each 3D method with those obtained with 2D-separate as a reference standard., Results: Excellent agreements and correlations with the 2D-separate were obtained by the 3D-Dixon method for both mean (ICC = 0.964, r = 0.93, P < 0.0001) and 90th-percentile (ICC = 0.972, r = 0.95, P < 0.0001) APT-weighted signals. These agreements and correlations for 3D-Dixon were better than those obtained by the 3D-uncorrected and 3D-separate methods., Conclusion: The 3D FSE Dixon APT method with intrinsic B 0 correction offers a quantitative performance that is similar to that of established two-dimensional (2D) methods. Magn Reson Med 77:2272-2279, 2017. © 2016 International Society for Magnetic Resonance in Medicine., (© 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.)

It has been hypothesized that increased flux through the pentose phosphate pathway (PPP) is required to support the metabolic demands of rapid malignant cell growth. Using orthotopic mouse models of human glioblastoma (GBM) and renal cell carcinoma metastatic to brain, we estimated the activity of the PPP relative to glycolysis by infusing [1,2-(13) C(2) ]glucose. The [3-(13) C]lactate/[2,3-(13) C(2) ]lactate ratio was similar for both the GBM and brain metastasis and their respective surrounding brains (GBM, 0.197 ± 0.011 and 0.195 ± 0.033, respectively (p = 1); metastasis: 0.126 and 0.119 ± 0.033, respectively). This suggests that the rate of glycolysis is significantly greater than the PPP flux in these tumors, and that the PPP flux into the lactate pool is similar in both tumors. Remarkably, (13) C-(13) C coupling was observed in molecules derived from Krebs cycle intermediates in both tumor types, denoting glucose oxidation. In the renal cell carcinoma, in contrast with GBM, (13) C multiplets of γ-aminobutyric acid (GABA) differed from its precursor glutamate, suggesting that GABA did not derive from a common glutamate precursor pool. In addition, the orthotopic renal tumor, the patient's primary renal mass and brain metastasis were all strongly immunopositive for the 67-kDa isoform of glutamate decarboxylase, as were 84% of tumors on a renal cell carcinoma tissue microarray of the same histology, suggesting that GABA synthesis is cell autonomous in at least a subset of renal cell carcinomas. Taken together, these data demonstrate that (13) C-labeled glucose can be used in orthotopic mouse models to study tumor metabolism in vivo and to ascertain new metabolic targets for cancer diagnosis and therapy., (Copyright © 2012 John Wiley & Sons, Ltd.)

The exchange of water molecules between the inner sphere of a paramagnetic chemical exchange saturation transfer (PARACEST) contrast agent and bulk water can shorten the bulk water T(2) through the T(2) -exchange (T(2ex) ) mechanism. The line-broadening T(2ex) effect is proportional to the agent concentration, the chemical shift of the exchanging water molecule, and is highly dependent on the water molecule exchange rate. A significant T(2ex) contribution to the bulk water linewidth can make the regions of agent uptake appear dark when imaging with conventional sequences like gradient-echo and fast spin-echo. The minimum echo times for these sequences (1-10 ms) are not fast enough to capture signal from the regions of shortened T(2) . This makes "Off" (saturation at -Δω) minus "On" (saturation at +Δω) imaging of PARACEST agents difficult, because the regions of uptake are dark in both images. It is shown here that the loss of bulk water signal due to T(2ex) can be reclaimed using the ultrashort echo times (<10 μs) achieved with the sweep imaging with Fourier transform pulse sequence. Modification of the sweep imaging with Fourier transform sequence for PARACEST imaging is first discussed, followed by parameter optimization using in vitro experiments. In vivo PARACEST studies comparing fast spin-echo to sweep imaging with Fourier transform were performed using EuDOTA-(gly) 4- uptake in healthy mouse kidneys. The results show that the negative contrast caused by T(2ex) can be overcome using the ultrashort echo time achieved with sweep imaging with Fourier transform, thereby enabling fast and sensitive in vivo PARACEST imaging., (Copyright © 2011 Wiley Periodicals, Inc.)

Purpose: the purpose of this study was to examine interhemispheric asymmetry in volume of the caudate nucleus and its age dependency., Methods: high-resolution T1-weighted brain magnetic resonance (MR) images were obtained for each subject using a 3-dimensional fast field-echo pulse sequence. The volumes of the bilateral caudate nuclei on MR images were measured using an automated method. Right-to-left comparison was made using paired t-test. Age-related change of right-to-left volume ratio (R/L ratio) was examined using Pearson's correlation coefficient., Results: fifty healthy right-handed Japanese male subjects (age 12 to 67 years, mean 39.6 years) were involved in this study. The volume of right caudate nucleus was larger than the left in 48 of 50 subjects (P < .001). R/L ratio increased with age (r= .420, P < .01)., Conclusions: our results confirmed the rightward volumetric asymmetry of caudate nucleus in right-handed individuals, and revealed that this asymmetry becomes notable with age.

Nonuniform disruption of lung architecture is usually assessed by CT, which carries potential radiation risk. Here we report our use of a three-dimensional ultrashort echo time MR method to image the lungs of normal mice at different positive end-expiratory pressures in a 3-T clinical MR system. The ultrashort echo time sequence in conjunction with a projection acquisition of the free induction decay could reduce the echo time to 100 μsec and provide a more inherent MR signal intensity from the lung parenchyma, which is usually invisible due to its short T*(2) in conventional MRI methods. The signal intensity and T*(2) was reduced as the positive end-expiratory pressure became higher. Further, these parameters were highly correlated to the changes in lung volume (% lung expansion). The results indicated that the MR signal acquired at ultrashort echo time in the lung parenchyma represents interstitial tissue density including blood. The capability of acquiring sufficient MR signal would have implications for the direct assessment of parenchymal architecture in the lung. Therefore, ultrashort echo time imaging may have the potential to assist detection of early and localized pathological destruction of lung tissue architecture observed in various pulmonary disorders such as emphysema without incurring the risks of radiation exposure., (Copyright © 2010 Wiley-Liss, Inc.)

Continuous maturation of cerebral white matter (WM) in the postadolescent period is not fully understood. To elucidate the time course and location of possible postadolescent maturational changes in cerebral WM, we studied 60 healthy male subjects who were in their second to seventh decade using diffusion-weighted imaging. Mean diffusivity (MD) in subcortical WM was measured in 78 cortical regions in each subject's brain using an automated method. Regression analysis was used to model the age-related change in MD by either a linear or a quadratic function in each region. Age-related changes in subcortical MD were best modeled by either a linear function or a quadratic function in 27 regions including language-related regions, visual or multimodal areas in the bilateral occipital and temporal lobes, limbic areas including the bilateral parahippocampal gyri, and the bilateral postcentral and left precentral gyri. In these regions, the MD rapidly decreased until middle age and thereafter reached a plateau. Our results revealed microstructural changes in local subcortical WM and suggests a continuing maturational process in postoadolescent periods.

Background: The inconsistency of previous reports examining cognitive function in obsessive-compulsive disorder (OCD) suggests its heterogeneity. In this study, we examined the effect of illness duration on cognitive function in OCD., Methods: We examined the cognitive function of 32 OCD patients and 16 healthy volunteers by neuropsychological tests and functional magnetic resonance imaging while they performed the Stroop and N-back tasks to assess attention and nonverbal memory. The patients were divided into two groups by illness duration: a short-term group (n=17, 5.5+/-3.1 years) and a long-term group (n=15, 20.3+/-6.1 years). Statistical analysis was performed to determine the differences between these two groups and the normal control group (n=16)., Results: The long-term group showed attention deficit and nonverbal memory dysfunction on the neuropsychological tests. In contrast, on functional magnetic resonance imaging, the short-term group showed weaker activation of the right caudate during the Stroop task and stronger activation of the right dorso-lateral prefrontal cortex during the N-back task than the long-term and normal control groups., Conclusions: The results suggested that abnormal brain activation occurs in the early phase of OCD and that the long-term persistence of OCD might involve a decline in cognitive function.

Previous studies have shown that diffusion-weighted imaging (DWI) is useful for detecting microstructural degradation of neuronal tissue in neurodegenerative diseases. Mapping of cortical degeneration by DWI is potentially useful, but is extremely difficult, mainly because of the partial volume effect resulting from the surrounding cerebrospinal fluid (CSF). In this study a novel method to map and display the cortical damage in neurodegenerative diseases using DWI is proposed. Instead of measuring the cortical diffusivity, the diffusivity of white matter directly beneath the cortex, where neuronal fibers enter or exit the overlying cortex, was measured and mapped onto the cortical surface. The map was viewed in a form of three-dimensional (3D) rendering. Patients with Alzheimer's disease (AD) showed cortical damage in the temporal and parietal cortices, and a patient with frontotemporal dementia showed damage in the frontal lobe, consistent with the typical topographical distribution of histopathological cortical damage in each of these diseases. The results suggest that subcortical diffusivity closely reflects cortical damage, and that the current mapping technique is a promising tool for evaluating neurodegenerative diseases., (2005 Wiley-Liss, Inc)