Purpose: Diffusion-weighted (DW) magnetic resonance (MR) imaging of the nerve roots and peripheral nerves has been reported. We applied a sequence similar to brain diffusion tensor (DT) tractography to such a technique and assessed its feasibility.
Methods: On a 1.5-T MR system, we acquired DW images in the axial plane using a single-shot echo-planar short tau inversion-recovery (STIR)-based sequence. Motion-probing gradients (MPGs) were applied in 6 directions with a b-value of 500 s/mm². For postprocessing, we performed maximum-intensity projection to reconstruct the images. We obtained cervical spine images from 3 volunteers and 8 patients and thoracolumbar spine images from 3 volunteers and 6 patients. On the source images of the cervical spine obtained from the volunteers, we compared the signal-to-noise ratios (SNRs) of the neural structures between images obtained applying MPG in 6 directions and in 3 directions. We visually assessed the nerve roots and proximal portions of the contiguous peripheral nerves in the images from volunteers and patients.
Results: The SNRs were significantly superior in the images obtained with the application of MPGs in 6 directions to those obtained with the application of MPGs in 3 directions (P<0.01). Visual assessment demonstrated the nerve roots as well as the nerve ganglia and the contiguous peripheral nerves up to 3 cm or more from the respective neural foramina in each subject. Image distortion was minimal.
Conclusions: Our technique provides neurographic images of the nerve roots and proximal portions of the contiguous peripheral nerves, and images obtained using our sequence applying MPGs in 6 directions are superior to those obtained in 3 directions.

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To clarify the magnetic resonance (MR) characteristics of primary uterine malignant lymphoma, we identified 4 patients with primary uterine lymphoma in the MR database of our institute from 1994 to 2005 and evaluated their clinical and MR findings for tumor extension, size, shape, and signal intensity, multinodular growth pattern, preservation of normal endometrium, and lymphadenopathy. In all 4 patients, tumors extended to the uterus and vagina or parametrium, and uterine tumors showed relatively homogeneous intensity on both T₁- and T₂-weighted MR imaging. Two patients showed multinodular tumor growth; three revealed pelvic lymphadenopathy; and none had intact endometrium or normal uterine zonal structure. Thus, large tumors with relatively homogeneous signal intensity seemed to be a specific MR finding of uterine lymphoma, and findings of multinodular growth were considered a possible characteristic suggesting the uterine involvement of malignant lymphoma.

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We evaluated the quality of dynamic magnetic resonance (MR) imaging of the temporomandibular joint (TMJ) in 20 normal volunteers with 40 TMJs. To confirm TMJ, we obtained static proton density weighted images (PDWI) before performing dynamic MR imaging with true-fast imaging in a steady-state precession (true-FISP) sequence. Four sequences of the first 10 volunteers were examined to determine the optimal sequence. The 4 sequences included the integrated parallel acquisition technique (iPAT) and/or fat saturation technique. The optimal sequence was then determined and performed in all 20 volunteers. The quality of imaging was evaluated, especially with respect to the conspicuity of the articular disk, mandibular condyle, articular eminence and lateral pterygoid muscle. One of 3 confidence levels was assigned for this evaluation. Neither iPAT nor fat saturation obtained the best quality imaging. Detection rates in the 20 volunteers were 83% for the articular disk, 95% for the mandibular condyle, 96% for the articular eminence and 7.5% for the lateral pterygoid muscle.
We recommend dynamic MR imaging of the TMJ with the true-FISP sequence using neither iPAT nor fat saturation. Nevertheless, dynamic MR imaging was inferior to static imaging in detecting the articular disk and still requires improvement.

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We combined diffusion-weighted (DWI) and short TI inversion recovery (STIR) imaging to evaluate the diagnostic capability of non-contrast magnetic resonance (MR) imaging to detect breast cancer. Seventy women patients underwent mammography and MR imaging with combined DWI (b factor: 1000) and STIR that revealed malignancy, and postoperative pathological examination confirmed breast cancer. Interpreted images were evaluated for sensitivity, false negative rate (FN), sensitivity by pT, and sensitivity by background density of the mammary gland. Of the 70 cases, 68 were diagnosed as cancer by DWI and STIR (sensitivity, 97% [68/70]; FN, 2.9% [2/70]). Sensitivities by pT were: pTis, 67% (4/6); pT1, 100% (33/33); and pT2-4, 100% (31/31). No significant differences were observed in sensitivity between pT1 and pT2-4 (P<0.001). Sensitivities by background density of mammary gland were: fatty/scattered fibroglandular tissue, 95% (20/21) and heterogeneous fibroglandular tissue/mostly fibroglandular tissue, 98% (48/49). No significant differences were observed (P<0.001). Two cases, an intraductal and an apocrine carcinoma, were incorrectly diagnosed by MR imaging.
Precise diagnosis of breast cancer is possible with combined DWI and STIR, even in non-contrast MR imaging, regardless of the diameter or background density of mammary gland. It is hoped that non-contrast MR imaging that combines DWI and STIR will become an established clinical screening method.

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Parallel imaging techniques have developed very rapidly, and realization of their full potential has required the design of magnetic resonance (MR) scanners with ever-increasing numbers of receiver channels (32 to 128). In particular, 1.5- and 3-Tesla fast MR imaging applications are now used in everyday clinical practice. Both strengths require maximum achievable signal-to-noise ratio (SNR) and multi-detector array coil optimization within the framework of the parallel imaging scheme for more advanced and faster clinical MR scanning. Preamplifiers are key components in the detector array coils and serve many functions beyond mere signal amplification. One critical function is to aid in the decoupling of individual coils, which is essential for optimal SNR and the performance of parallel imaging. To support a large number of detector array coils for parallel imaging, preamplifiers must be physically very small so that they may be tightly packed together to form an optimized detector array. The author herein reviews the state-of-the-art work reported by those skilled in the art to consider the rationale for determining how many channels are enough and how fast we can go. The paper explores the important and fundamental principles of RF array coils for MR imaging and reviews cutting-edge array coils, including those for transmit-SENSE or parallel transmission applications. The future of radiofrequency (RF) coil technology is also considered.

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The appropriate staging of malignant tumors is increasingly important as new therapeutic strategies develop. Because metastatic involvement of the liver in extrahepatic malignant disease may significantly change therapeutic approach, it is important to rule out such involvement with high confidence. Moreover, the differentiation between incidental benign lesions, such as hemangioma, focal nodular hyperplasia (FNH), or adenoma, is of high interest. Magnetic resonance (MR) imaging has proved reliable for diagnostic work-up of the liver. Liver-specific contrast agents have been especially helpful in detecting and precisely characterizing focal liver lesions, but the use of these agents has been limited because it has not been possible to perform both proper vascular phase and liver-specific phase within a reasonable time frame and in a single examination after a single injection of contrast agent. However, the hepatobiliary contrast agent gadolinium-ethoxybenzyl (Gd-EOB)-DTPA now allows combined dynamic imaging and hepatocyte-specific imaging in one examination. Gd-EOB-DTPA can be injected as a bolus and shows the enhancement characteristics and vascularity of liver lesions. In the delayed phase, which is acquired most appropriately 20 min after injection, Gd-EOB-DTPA is taken up selectively by functioning hepatocytes. Thus, malignant liver lesions, e.g. metastases, are spared from contrast uptake of the surrounding liver parenchyma. These lesions are hypointense in contrast to the surrounding bright liver. We review the current literature and present a practical approach to Gd-EOB-enhanced MR imaging using imaging examples of patients with liver metastases.

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Gerstmann-Sträussler-Scheinker syndrome (GSS syndrome) is a rare hereditary disorder caused by prion protein gene mutation. We present the case of a 31-year-old man, whose signs and symptoms gradually progressed from loss of attention while driving at onset to headache, dysarthria, night sweat, fatigue, and dysgraphia. Diffusion-weighted imaging (DWI) of the brain after admission showed high signal intensities in the bilateral caudate nuclei, bilateral thalami, and cerebral cortices that suggested transmissible spongiform encephalopathy. The patient was diagnosed with GSS syndrome on genetic study. Magnetic resonance (MR) imaging of the entire period of sickbed showed gradually changing signal intensities and cerebral atrophy. We present a series of images and discuss the reasons for the abnormal intensities in GSS syndrome that vary among reported cases.

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