Purpose: Signal intensity and image contrast differ between postmortem magnetic resonance (PMMR) images and images acquired from the living body. We sought to achieve sufficient fat suppression with short-tau inversion recovery (STIR) PMMR imaging by optimizing inversion time (TI).Material and Methods: We subjected 37 deceased adult patients to PMMR imaging at 1.5 tesla 8 to 60 hours after confirmation of death and measured T₁ values of areas of subcutaneous fat with relaxation time maps. Rectal temperature (RT) measured immediately after PMMR ranged from 6 to 31°C. We used Pearson’s correlation coefficient to analyze the relationship between T₁ and relaxation time (RT). We compared STIR images from 4 cadavers acquired with a TI commonly used in the living body and another TI calculated from the linear regression of T₁ and RT.Results: T₁ values of subcutaneous fat ranged from 89.4 to 182.2 ms. There was a strong, positive, and significant correlation between T₁ and RT (r = 0.91, P < 0.0001). The regression expression for the relationship was T₁ = 2.6*RT + 90 at a field strength of 1.5T. The subcutaneous fat signal was suppressed more effectively with the optimized TI.Conclusion: The T₁ value of subcutaneous fat in PMMR correlates linearly with body temperature. Using this correlation to determine TI, fat suppression with PMMR STIR imaging can be easily improved.

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Purpose: We developed semi-quantitative methods to measure endolymphatic size on images obtained 4 hours after intravenous administration of single-dose gadolinium-based contrast medium (IV-SD-GBCM) and found little variation in results between observers. We used the methods to measure the size of the endolymph in healthy volunteers at various times after IV-SD-GBCM and attempted to determine the optimal timing for the evaluation.Methods: In 8 healthy male volunteers, we obtained heavily T₂-weighted 3-dimensional fluid-attenuated inversion recovery (hT₂W-3D-FLAIR) images 1.5, 3, 4.5, and 6 hours after IV-SD-GBCM as positive perilymph images (PPI) as well as acquiring positive endolymph images (PEI) and magnetic resonance cisternography (MRC). To evaluate the endolymph, we generated 2 kinds of processed images (HYDROPS-Mi2 and HYDROPS2-Mi2) by subtracting PEI or MRC from PPI as previously proposed. We semi-quantitatively measured the ratio of the area of the endolymph (%EL) to that of total lymph on the 2 kinds of generated images for the cochlea and vestibule according to the previously proposed method. We analyzed statistics to evaluate the change in %EL over time and used analysis of variance (ANOVA) for a 2 × 4 repeated-measures design to assess difference in image type. We adopted 5% as a significance level.Results: The %EL was significantly larger at 1.5 hours after IV-SD-GBCM than at 3, 4.5, and 6 hours in both the cochlea and vestibule for both kinds of generated images. Between 4.5 and 6 hours, the %EL plateaued for both the cochlea and vestibule, and the 2 kinds of generated images did not differ significantly.Conclusion: A delay of 1.5 hours after IV-SD-GBCM is not sufficient to evaluate endolymphatic size. The %EL plateaus between 4.5 and 6 hours. These data might be valuable for further clinical studies.

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Purpose: Routine clinical practice involves the application of diverse scanning parameters that can affect apparent diffusion coefficient (ADC) values. We evaluated interimager variability in ADC values with respect to their potential effect in clinical applications.Methods: In 7 healthy volunteers, we obtained diffusion-weighted (DW) images using routine clinical parameters and 1.5- (n = 9) and 3-tesla (n = 3) magnetic resonance (MR) imagers from 5 different vendors, performing 84 MR imaging studies. To evaluate the differences in ADC values among the imagers, vendors, and magnetic field strengths, we measured the mean pixel values of the frontal white matter and thalamus (gray matter) in both cerebral hemispheres of the 7 volunteers and used repeated-measures analysis of variance for multiple comparisons.Results: The laterality of ADC values in the bilateral structures ranged from one to 3% for the 12 imagers. Although the relative difference in ADC values of white matter was 7% for scanners yielding the highest and lowest mean ADC values (P < 0.01), it was within 2 to 4% for instruments from the same vendors. For gray matter, the interimager difference was 4 to 12%, even among the same vendors (P < 0.05). Among the 3T imagers, the difference for white and gray matter was approximately 3%.Conclusions: There were significant interimager differences in ADC values, especially with respect to gray matter. Taking into consideration the existing laterality, however, the differences among our 3T imagers may be acceptable despite the use of diverse scanning parameters. In routine clinical practice, the existing variability must be considered imager by imager.

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Purpose: We assessed the usefulness of apparent diffusion coefficients (ADCs) for solid renal tumor imaging using diffusion-weighted magnetic resonance imaging (DWI) at 3T.Methods: This retrospective study assessed ADCs of 31 patients with renal tumors that were imaged using preoperative DWI. DWI was performed with the b values of 50, 500, and 1000 s/mm², using a 3T magnetic resonance imaging (MRI) system (MAGNETOM Trio, 3T, Siemens Healthcare, Erlangen, Germany). The ADC map was calculated using the b values of 50 and 1000 s/mm². ADCs of the different tumors were compared according to the Tukey–Kramer test.Results: The tumors were diagnosed as clear cell renal cell carcinoma (RCC; n = 20), papillary RCC (n = 1), infiltrating urothelial carcinoma (UC) of the kidney (n = 4), cystic RCC (n = 1), poorly differentiated carcinoma (n = 1), and angiomyolipoma (AML; n = 4). The mean ADC of clear cell RCC was significantly higher than that of infiltrating UC of the kidney (1.423 vs. 0.931 × 10⁻³ mm²/s; P < 0.05), and the mean ADC of AML was significantly lower than that of clear cell RCC (0.674 vs. 1.423 × 10⁻³ mm²/s; P < 0.01).Conclusion: ADCs used in DWI at 3T may be useful for differentiation of different types of solid renal tumors.

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Diffusional kurtosis imaging (DKI) for clinical imaging involves time-consuming computation and demonstrates low robustness. Standard estimation of DKI parameters is based on an extension of Stejskal-Tanner’s signal model with squared b-value term and is a least-squares fitting problem. The use of numerical methods for computation requires time, and estimation of DKI parameters is noise sensitive and often produces noisy results, such as images with pepper noise.In this study, we propose general closed-form solutions for DKI parameters to avoid numerical computation for least-squares fitting, solutions that can be applied to diffusion weighted imaging (DWI) datasets with any number of b-values more than three. Solutions are obtained through stationary-point conditions of an objective function that are minimized for fitting. We use 3 techniques to extend the solutions to increase robustness—b-value-dependent weighting in fitting, removal of outliers, and addition of neighbor sampling. Based on synthetic datasets and clinical datasets that both consist of 6 b-value and 3 b-value datasets, we detail and compare the 3 methods including a method by Jensen et al. are compared and investigated in detail. The synthetic data consist of several combinations of DKI parameters and some Rician noise. In addition to visually assessing result images, we also performed quantitative evaluation using a range of estimated parameters, positive-definiteness of the objective function for fitting, and root-mean-square error including estimation bias from the true value (synthetic data only). Methods that added neighbor sampling outperformed others in terms of low errors and visual smoothness. Though the solution by our methodis to estimate DKI parameters in a single MPG direction, it can contribute to anisotropic analysis of diffusional kurtosis such as kurtosis tensor. More robust estimation is expected by combining techniques.

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We present a case of a 69-year-old man with primary hepatic carcinosarcoma who underwent computed tomography that revealed a hypervascular hepatic tumor with local dense calcification. Gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging revealed hyperintense lesions in the hepatobiliary phase that indicated hepatocellular carcinoma with bile production. The patient underwent right lobectomy, and the presence of a sarcoma component within the tumor on histopathology confirmed liver carcinosarcoma that included hepatocellular carcinoma. In cases with atypical images that resemble this case, the hyperintensity of a lesion in the hepatobiliary phase aids differential diagnosis.

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In 2 cases of Wernicke encephalopathy in which the initial symptom was double vision, the only abnormal finding on magnetic resonance (MR) imaging was abnormal enhancement of the mammillary bodies. The mammillary bodies are the region most vulnerable to abnormal enhancement. Because MR imaging with contrast enhancement can detect such abnormal enhancement at an early stage, it should be performed more often in patients with oculomotor disorders to avoid underdiagnosis of Wernicke encephalopathy.

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We compared visualization of corticomedullary differentiation between fast asymmetric spin echo (FASE) and steady-state free precession (SSFP) combined with spatially selective inversion recovery (IR) pulse and optimal inversion time (TI). Though the corticomedullary contrast ratio was higher in FASE than SSFP images, visualization of corticomedullary differentiation was significantly better in SSFP images than FASE images obtained with spatially selective IR pulses and optimal TI.

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Endolymphatic hydrops (EH) in Ménière’s disease is currently evaluated by 3-dimensional (3D)-real inversion recovery (IR) sequence after intratympanic (IT) administration of gadolinium (Gd) or by heavily T₂-weighted (hT₂W)-3D-fluid-attenuated IR (FLAIR) sequence after intravenous (IV) injection of Gd. Unilateral IT injection is usually performed. We employed a method in which we simultaneously administered contrast into one ear intravenously (IV side) and into the other ear both intravenously and intratympanically (IT + IV side) to evaluate EH in 10 patients with Ménière’s disease. We then compared a HYDROPS2 image obtained by subtracting magnetic resonance cisternography from hT₂W-3D-FLAIR with an image obtained by 3D-real IR and found that we could evaluate EH in all ears on the HYDROPS2 image but only in the IT + IV side on the 3D-real IR image.

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Purpose: We assessed the improved motion-sensitized driven equilibrium (iMSDE) technique for multiple contrast 3-dimensional vessel wall imaging at 3T.Methods: Carotid images were obtained using iMSDE combined with turbo field echo (iMSDE-TFE) and conventional double inversion-recovery turbo spin-echo (DIR-TSE) in 5 healthy adult subjects. The tissue signal-to-noise efficiency (SNR_eff), SNR divided by the square root of scan time, lumen-tissue contrast-to-noise efficiency (CNR_eff), CNR divided by the square root of scan time, and tissue signal intensity ratio (SIR) were measured in both techniques and compared.Results: The iMSDE-TFE had higher SNR_eff and CNR_eff (P < 0.01) and strong correlation in SIR (R = 0.92) compared to DIR-TSE.Conclusion: The iMSDE-TFE sequence is an efficient technique for vessel wall screening.

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