Purpose: We assessed the utility of diffusion-weighted imaging (DWI) with relative signal intensity (rSI) statistical thresholding for delineating prostate cancer tumors.
Materials and Methods: Seventeen patients with prostate cancer underwent DWI before total prostatectomy. We measured standard deviation (SD) of the signal intensity (SI) of the lesser pelvic space at DWI, created rSI maps, displaying signal intensities with SDs of only >+3, >+3.5, >+4, or >+5, and assessed correlation between the proportion of cancerous area on the 4 different rSI maps and that on pathological slices.
Results: We could detect prostate cancer on rSI maps for all cases with SD >+3, but not 2 cases with SD >+3.5, five with SD >+4, and eight with SD >+5. The correlation coefficients (R) between the proportion of cancerous area on pathological examination and rSI maps were 0.7464 for SD >+3 (P=0.0006); 0.6469 for SD >+3.5 (P=0.0050); 0.6459 for SD >+4 (P=0.0051), and 0.4540 for SD >+5 (P=0.0671).
Conclusion: DWI-based rSI mapping may be used to delineate the extent of prostate cancer. We achieved best correlation between ratio of cancerous area of the lesser pelvic space on pathological examination and on rSI map using a threshold with SD >+3 of the SI.

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Purpose: Whole-heart 3-dimensional (3D) late-gadolinium-enhanced magnetic resonance (MR) imaging (WH-LGE) uses respiratory gating combined with acquisition of 3D data for the entire heart in a single scan, which permits reconstruction of any plane with high resolution. We investigated the optimal scan parameters and compared WH-LGE with the conventional scanning method.
Materials and Methods: We employed inversion recovery 3D fast field echo using a 1.5-tesla system and scan parameters: repetition time (TR), 6.6 ms; echo time (TE), 2.5 ms; number of segments, 2; parallel imaging factor, 1.8; matrix size, 128×256; field of view (FOV), 320×320 mm; and acquisition slice thickness, 3 mm (reconstruction slice thickness, 1.5 mm). Five healthy volunteers underwent scanning during free breathing with real-time motion correction, from which we determined optimal scan parameters. We then used those parameters to scan 25 patients with myocardial infarction to compare scan time and image quality between the WH-LGE and conventional 3D breath-holding methods (slice thickness, 10 mm; matrix size, 128×256).
Results: Results in volunteers showed optimal scan parameters of 12° flip angle, fat suppression turned off in combination, and interleaved ordering. In clinical cases, scan times did not differ significantly. Sharpness of the margins of normal myocardium at the apex of the heart and contrast between enhanced and nonenhanced myocardium improved significantly with WH-LGE.
Conclusion: WH-LGE yields high resolution images during free breathing and is considered useful for accurately estimating the area and transmural extent of myocardial infarction.

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Purpose: In magnetic resonance imaging of the brain, BLADE is used to compensate for head motion. The technique focuses mainly on acquisition of T₂-weighted or contrast-enhanced T₁-weighted images in adults; its utility for nonenhanced T₁-weighted imaging in children is not well established. We compared the quality of T₁-weighted fluid-attenuated inversion recovery brain imaging with BLADE (T₁-FLAIR-BLADE) to that of conventional spin-echo T₁-weighted imaging (T₁-SE) in pediatric patients who cannot stay still during MR imaging.
Materials and Methods: Our investigation included a volunteer study and a retrospective clinical study. Six healthy adult volunteers underwent scanning to compare the contrast of T₁-SE, T₁-weighted fluid-attenuated inversion recovery imaging (T₁-FLAIR), and T₁-FLAIR-BLADE at both 1.5 and 3 tesla. Comparison was based on scores assigned independently by 2 blinded observers and by calculated contrast-to-noise ratio. The clinical study included 20 children who underwent both T₁-SE and T₁-FLAIR-BLADE at either 1.5 (n=9) or 3 T (n=11). On each sequence, 2 blinded observers independently scored visualization of the cerebral gyri and contrast between gray and white matter. We compared scores between sequences separately for 1.5 and 3T using Wilcoxon signed-rank tests.
Results: At both 1.5 and 3T, contrast was better using T₁-FLAIR and T₁-FLAIR-BLADE than T₁-SE in volunteers, and overall scores were significantly higher with T₁-FLAIR-BLADE (P<0.05) than T₁-SE in the clinical study.
Conclusion: T₁-FLAIR-BLADE may be superior to T₁-SE in demonstrating brain structures in children who cannot stay still and may be used to supplement or replace T₁-SE when T₁-SE is insufficient for patient motion.

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Purpose: We aimed to show that correcting image distortion significantly affects brain volumetry using voxel-based morphometry (VBM) and to assess whether the processing of distortion correction reduces system dependency.
Materials and Methods: We obtained contiguous sagittal T₁-weighted images of the brain from 22 healthy participants using 1.5- and 3-tesla magnetic resonance (MR) scanners, preprocessed images using Statistical Parametric Mapping 5, and tested the relation between distortion correction and brain volume using VBM.
Results: Local brain volume significantly increased or decreased on corrected images compared with uncorrected images. In addition, the method used to correct image distortion for gradient nonlinearity produced fewer volumetric errors from MR system variation.
Conclusion: This is the first VBM study to show more precise volumetry using VBM with corrected images. These results indicate that multi-scanner or multi-site imaging trials require correction for distortion induced by gradient nonlinearity.

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Purpose: We investigated the feasibility of performing chemical exchange saturation transfer (CEST) imaging using ytterbium-based paramagnetic CEST (PARACEST) agents on a clinical magnetic resonance (MR) scanner.
Materials and Methods: We prepared solutions of 3 different ytterbium-based PARACEST agents at concentrations of 5, 10, 20, and 50 mM at a pH of 7.4 and at a concentration of 50 mM at pHs of 3.0, 5.0, 7.4, and 9.5. We acquired images with a turbo spin echo technique using a quadrature head coil and a clinical 3.0-tesla MR system in accordance with the safety limits of the specific absorption rate (SAR). We acquired CEST images with presaturation offset frequencies from −5,000 Hz (−39.1 ppm) to 5,000 Hz (39.1 ppm) with an interval of 500 Hz (3.9 ppm) for each condition. We repeated each scan 3 times and then calculated the mean and standard deviations of the magnitude of the CEST effect at different concentrations and pH values for each agent. We used one-way analysis of variance and Tukey's honestly significant difference post hoc test to compare mean values of the magnitude of the CEST effect obtained at different concentrations and pH values. P<0.05 was considered significant.
Results: PARACEST agents showed a strong CEST effect at their specific presaturation offset frequencies. For each agent, the CEST effect showed significant concentration dependency (P<0.05), increasing with agent concentration, and significant pH dependency (P<0.05), with strong effect near physiological pH.
Conclusion: CEST imaging using ytterbium-based PARACEST agents might be feasible on a clinical MR scanner with further modifications, such as adjustments of the presaturation radiofrequency pulse and imaging protocols.

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Purpose: Visualization of endolymphatic hydrops (EH) in patients with Ménière's disease (MD) is now possible by heavily T₂-weighted 3-dimensional fluid-attenuated inversion recovery (hT₂W-3D-FLAIR) obtained 4 hours after intravenous (IV) administration of single dose gadolinium-based contrast medium (GBCM). Although maximum enhancement has been reported 4 hours after contrast administration in healthy volunteers, the timing of optimal enhancement in patients with MD is not reported. We investigated if that optimal timing is earlier or later than 4 hours.
Materials and Methods: We evaluated 10 consecutive patients with suspected MD whom we randomly divided into 2 groups. We obtained hT₂W-3D-FLAIR before GBCM administration and 10 min, 3.5 hours, and 4 hours after GBCM administration in Group A and before and 10 min, 4 hours, and 4.5 hours after GBCM administration in Group B. We compared signal intensity ratio (SIR) values of the perilymph and pons between 3.5 and 4 hours in Group A and between 4 and 4.5 hours in Group B and evaluated grades of EH at 3.5 and 4 hours in Group A and at 4 and 4.5 hours in Group B.
Results: SIR values did not differ significantly between 3.5 and 4 hours in Group A and between 4 and 4.5 hours in Group B. However, SIR values at 4 hours were significantly higher in Group A than Group B. Grades of EH agreed between 3.5 and 4 hours in Group A and between 4 and 4.5 hours in Group B.
Conclusion: The optimal timing of contrast enhancement in patients with suspected MD remains unclear, but evaluation of EH may be possible from 3.5 to 4.5 hours after contrast administration.

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Purpose: We evaluated concanavalin A (Con A)-induced acute hepatic injury in rats using an empirical mathematical model (EMM) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA).
Materials and Methods: We allocated 18 rats into 3 groups of six each and intravenously injected them with either 10 mg/kg body weight (BW) of Con A (Con A [10] group), 20 mg/kg BW of Con A (Con A [20] group), or a single dose of of saline (4 mL/kg BW, normal control group). We performed the DCE-MRI studies using Gd-EOB-DTPA (0.025 mmol Gd/kg; 0.1 mL/kg BW) as the contrast agent 24 hours after injection of Con A or saline. We then sampled blood, measured serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and calculated the rate of contrast uptake (α), rate of contrast washout (β), area under the curve (AUC), time to maximum relative enhancement (RE) (T_max), and elimination half-life of RE (T_1/2) from the time-signal intensity curves using the EMM.
Results: β values were significantly smaller in the Con A (10) and Con A (20) groups than the control group, but α did not differ significantly among the 3 groups. The AUC value was significantly greater in the Con A (10) group than controls, and the T_max and T_1/2 values were significantly greater in the Con A (20) group than controls. The β, T_max, and T_1/2 values correlated significantly with AST and ALT.
Conclusion: In conclusion, the EMM is useful for evaluating Con A-induced acute hepatic injury using DCE-MRI with Gd-EOB-DTPA.

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We present a case of focal medullary sponge kidney (MSK) that mimicked a renal tumor. Evaluation of a patient with history of macrohematuria revealed a left renal mass of 3-cm diameter. T₁-weighted magnetic resonance (MR) images revealed a mass of mixed intensity protruding toward the renal sinus. On fat-saturated T₂-weighted MR images, the lesion's remarkable hyperintensity suggested the presence of an aggregation of tiny cysts. On diffusion-weighted MR images, the mass also demonstrated high intensity, and its apparent diffusion coefficient was partly decreased (1.12×10⁻³ mm²/s). On computed tomography, precontrast images revealed no calcification in the mass. Although slight enhancement was seen in the corticomedullary phase, thick and dense streaks of contrast radiating peripherally were identified in the mass in the excretory phase. Focal MSK was diagnosed. We discuss the potential of MR imaging for diagnosing focal MSK.

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Microscopically, ovarian malignant Brenner tumor shows components of malignant transitional cell tumor intermixed with benign and borderline elements. We report a case of this tumor with components that transition from benign to malignant on diffusion-weighted images (DWI) and in histologic findings. The benign component showed low signal intensity on T₂-weighted images, whereas the malignant component showed high signal intensity on T₂-weighted images and high signal intensity on DWI with low apparent diffusion coefficient (ADC) value.

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