Purpose: Accurate measurement of cerebrospinal fluid (CSF) flow rate elucidates pathophysiological changes in the intracranial environment and is thus clinically useful. We investigated the feasibility of correlation coefficient (CC) analysis for extracting CSF lumens in the cerebral aqueduct and cervical subarachnoid space (SAS) to quantify CSF flow rate and net flow from data acquired by phase-contrast magnetic resonance imaging (PC-MRI).
Methods: First, in phantom studies on pulsatile flow using a 1.5-tesla MR imaging system, we investigated the accuracy of CC analysis and used a statistical approach to determine an optimal threshold value for extracting the CSF lumens (CC_min). Second, we performed phantom studies on constant flow with various flow rates to estimate the accuracy of low flow measurement by PC-MRI. Finally, in 6 healthy male volunteers aged 24±2 years, we estimated the CSF lumen areas, net flows, and peak flow rates in the cerebral aqueduct and cervical SAS using CC analysis with the optimal CC_min value determined in phantom studies. Three observers analyzed results to compare reproducibility of CC analysis with that of manual segmentation.
Results: The optimal CC_min value for CC analysis was 0.41 for a matrix measuring 256×256. The CSF lumen area extracted by CC analysis was 6.15±2.52 mm², and the net flow in the cerebral aqueduct was 0.74±0.38 mL/min; in the cervical SAS, lumen area was 135.60±17.94 mm² and net flow, 12.55±12.67 mL/min. The reproducibility of CSF lumen extraction was better by CC analysis than manual segmentation.
Conclusion: CC analysis offers a quick and reproducible method for segmenting CSF lumens and calculating CSF flow rate.

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Purpose: We compared the image quality of SPACE (sampling perfection with application optimized contrasts using different flip angle evolutions) and conventional 3D turbo spin echo (TSE) magnetic resonance cholangiopancreatography (MRCP) at 1.5 tesla with regard to difference in echo spacing.
Methods: Twenty healthy volunteers prospectively underwent navigator-triggered SPACE and 3D TSE MRCP at 1.5T with identical parameters, except for echo spacing. Quantitative analyses of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), relative contrast, and contour sharpness index of each segment of the pancreaticobiliary tree were compared using paired t-tests. Qualitative analyses on a 5-point scale (1, excellent; 5, poor) scored by 2 independent radiologists were compared using Wilcoxon signed-rank test.
Results: The SNR, CNR, and contour sharpness index of each segment were significantly better for the SPACE sequence than 3D TSE (P<0.05). Relative contrast and subjective image quality were not significantly different (P>0.05).
Conclusion: We verified SPACE MRCP quantitatively superior to conventional 3D TSE MRCP at 1.5T as a result of shortening of echo spacing.

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Purpose: We assessed errors in cerebral blood flow (CBF) obtained from our proposed reference-based method without using arterial input function (AIF) indices in dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI).
Materials and Methods: We calculated CBF and the referential tissue-related ratio (CBFratio) using numerical simulation and 3 nondeconvolution methods and a deconvolution method of block-circulant singular value decomposition (cSVD). We compared errors with and without simulated noise as parameters of mean transit time (MTT), AIF delay and temporal resolution, and clinical DSC-MRI maps.
Results: The errors in CBF obtained using maximum upslope (US) were smallest among the nondeconvolution methods and almost equivalent to errors in the cSVD method under practical imaging conditions. In addition, errors in the CBFratio obtained using reference-based US (Ref-US) referring to white matter were smallest, even compared to all errors in CBF and CBFratio. The Ref-US method introduced less error than the cSVD method, especially at low flow rates, was further robust against AIF noise and coarse temporal resolution, and was comparably robust against transit delay. In pixel-by-pixel correlations between absolute value maps for US and for cSVD-CBF in clinical DSC-MRI, those correlation coefficients (r) between the 2 maps were stable, r>0.9, despite variation in the slopes of the linear regression line, so the 2 CBFratio maps were visually well correlated in any case.
Conclusion: The Ref-US technique without AIF measurement can become a practical perfusion methodology for DSC-MRI in patients even with acute stroke because it balances robustness with systematic and random errors and it is simply performed.

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Purpose: Temporal evolution of the water apparent diffusion coefficients (ADC) parallel (ADC∥) and perpendicular (ADC⊥) to the human white matter tract following ischemia has not been investigated systematically. We attempted to quantify the evolution of ADC∥ and ADC⊥ and examine whether it can be interpreted by a model of ischemic edema.
Methods: We retrospectively selected 53 patients with ischemic lesions involving the posterior limb of the internal capsule (PLIC) and placed regions of interest in the right and left PLIC on ADC maps. We performed regression analysis of lesion-to-contralateral ratios of ADC∥ and ADC⊥ against the time (t=1-1600 h) from onset. We then fitted the estimated time courses of ADC∥ and ADC⊥ obtained from the analysis to a model of nerve tissue composed of cylinders (axons) and spheres corresponding to isotropic structures, particularly focal cytoplasmic swellings of glial cells and axons seen in ischemic white matter.
Results: The evolution of ADC⊥ and ADC∥ differed. The estimated time course of ADC∥ in μm²•ms^-1 was 0.64+0.88 exp (-0.24t) for 1<t<54 h and 0.00059t+0.61 for t≥54 h (contralateral normal value, 1.52). That of ADC⊥ was 0.19-0.063 exp (-0.24t) for 1<t<54 h and 0.00040t+0.17 for t≥54 h (normal value 0.22). The model fitted to these values showed that the volume of the cylinders decreased, that of the spheres increased, and extracellular volume changed little from one hour to approximately one day after stroke onset.
Conclusion: In the human PLIC, ADC∥ continued to decrease from one hour to a few days after stroke onset, and ADC⊥ tended to increase. The temporal evolution could be interpreted by progression of the focal cytoplasmic swelling of glial cells and axons previously observed in animal studies.

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Spinal atypical teratoid/rhabdoid tumor (AT/RT) is a rare, aggressive malignant neoplasm of the central nervous system usually seen in young children and infants. We present diffusion-weighted imaging (DWI) findings for an intradural extramedullary AT/RT in the cervical spine of a 6-year-old boy. High signal on DWI and low apparent diffusion coefficients may represent high cellularity of the tumor. These findings indicated a highly malignant tumor.

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The origin of patchy white matter hyperintensities commonly seen in the elderly on magnetic resonance (MR) images with long repetition time (TR) is still controversial. We describe MR findings in older patients in whom white matter hyperintensities were attenuated by compression of the cerebral hemisphere from a chronic subdural hematoma. These sequential MR findings substantiate the hypothesis that leukoaraiosis may arise when drainage of the bulk flow of brain interstitial fluid is disturbed.

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