Toshiaki Nitatori

Diffusion-weighted MR imaging with single-shot echo-planar imaging in the upper abdomen: preliminary clinical experience in 61 patients

AbstractBackground: To determine the potential ability of diffusion-weighted magnetic resonance (MR) imaging with single-shot echo-planar imaging (DW imaging) in the upper abdomen by apparent diffusion coefficient (ADC) and signal:intensity ratio (SIR) measurements. Methods: DW imaging was performed in 61 clinical patients. ADCs in the liver, pancreas, spleen, kidney, and different pathological conditions were calculated. Spleen-to-liver SIR and segmental intensity difference of the liver (SID) were also calculated. Results: The mean ADCs (mm2/s) were 2.28 × 10−3± 0.07 in the liver, 1.44 × 10−3± 0.05 in the spleen, 1.94 × 10−3± 0.19 in the pancreas, and 5.76 × 10−3± 0.06 in the kidney. The mean ADC of cirrhotic liver was 1.96 × 10−3± 0.62, which was lower than that of normal liver. Other pathologic conditions also showed ADCs different from those of normal tissues. All DW images showed significantly higher spleen-to-liver SIRs and SIDs than did T2-weighted images (p < 0.05). Conclusion: The mean ADCs obtained with DW imaging were different in each upper abdominal organ and with each pathologic condition. DW images showed better soft tissue contrast than did T2-weighted images with regard to SIR and CNR in depicting and characterizing upper abdominal disorders.

Breath-held MR cholangiopancreatography with half-averaged single shot hybrid rapid acquisition with relaxation enhancement sequence : Comparison of fast GRE and SE sequences

PURPOSE Our goal was to determine whether half-averaged single shot hybrid rapid acquisition with relaxation enhancement (single shot hybrid RARE) sequence can improve image quality, duct conspicuity, signal intensity ratio (SIR), and contrast-to-noise ratio (CNR) of MR cholangiopancreatography (MRCP) by comparing it with two other MRCP sequences: fast SE (FSE) and contrast-enhanced Fourier-acquired steady-state technique (CE-FAST). METHOD MRCP with three sequences was obtained in 46 people (10 volunteers, 36 patients with pancreatobiliary disease). Overall image quality and duct conspicuity were graded. SIR and CNR were also measured. RESULTS Overall image quality was graded excellent or good in all 46 patients (100%) with single shot hybrid RARE, in 38 of 46 (83%) with FSE, and in 5 of 46 (11%) with CE-FAST. Duct conspicuity was the best in single shot hybrid RARE statistically. SIR was the highest in FSE, while CNR was highest statistically in single shot hybrid RARE of three sequences. CONCLUSION Single shot hybrid RARE can provide consistently higher quality MRCP than FSE and CE-FAST because sequential images by single shot hybrid RARE minimize respiratory, bowel, and cardiac motion artifacts.

Comparison of MRI Sequences to Detect Ventriculitis

OBJECTIVE The ability of different MRI sequences to depict characteristic findings suggestive of ventriculitis was compared. CONCLUSION The study comprised 20 brain MRI studies in 13 patients who had a final diagnosis of ventriculitis. Both diffusion-weighted imaging and FLAIR imaging were equally and highly sensitive for detecting intraventricular debris and pus--the most common MRI finding suggestive of ventriculitis. FLAIR imaging was superior to contrast-enhanced T1-weighted imaging for depicting ventricular wall abnormalities--a less common finding that also is suggestive of ventriculitis.

Does increased water intake prevent disease progression in autosomal dominant polycystic kidney disease

…with tolvaptan at present not being available for clinical care, other options that lower AVP activity should be considered. An alternative might be to lower AVP concentration by increasing water intake. In a rat model for polycystic kidney disease, a 3.5 fold increased water intake reduced urinary osmolality, renal expression of the AVP V2 receptor and reduced kidney weight compared to normal water intake…

Directed Proximal Magnetic Resonance Coronary Angiography Compared With Conventional Contrast Coronary Angiography

Magnetic resonance coronary angiography in 36 patients with proximal 1-vessel disease within 1 week of contrast coronary angiography was performed and the time required to complete the study was 13.4 +/- 4.2 min 13.2 +/- 8.1 minutes for the right and left coronary arteries, respectively. The sensitivity, specificity, positive and negative predictive values, and accuracy of magnetic resonance coronary angiography were 100% for right cronary artery disease, and 83%, 98%, 94%, 94%, and 94%, respectively, for left coronary artery disease.

Visualization of cervical nerve roots and their distal nerve fibers by diffusion-weighted scanning using parallel imaging

Purpose: To report a technique developed for visualizing cervical nerve roots and distal nerve fibers using diffusion-weighted magnetic resonance imaging employing parallel imaging. Material and Methods: We performed maximum intensity projection for a stack of isotropic axial diffusion-weighted images obtained with parallel imaging applying a motion-probing gradient in six directions with a b-value of 500 s/mm2 in a preliminary series of 13 subjects. Results: This method worked well for visualizing the spinal cord and most of the nerve roots, the dorsal root ganglia, and proximal peripheral nerves. Conclusion: Although the technique remains limited in depicting the brachial plexus and distal nerves, the ability to visualize the proximal peripheral nervous system at the cervical level is promising.

Hybrid of opposite‐contrast MRA of the brain by combining time‐of‐flight and black‐blood sequences: Initial experience in major trunk stenoocclusive diseases

To assess the feasibility of a new MR angiography (MRA) technique named hybrid of opposite‐contrast MRA (HOP MRA) that combined the time‐of‐flight (TOF) MRA with a flow‐sensitive black‐blood (FSBB) sequence in the diagnosis of major trunk stenoocclusive diseases.

CT of calcified chronic aortic dissection simulating atherosclerotic aneurysm

Calcification along the outermost aspect of the aorta usually means atherosclerotic aneurysm. On occasion, however, this peripheral type calcification is seen in chronic aortic dissection and leads to a misdiagnosis. Conventional chest roentgenography and CT of 50 cases of chronic dissection proven by angiography were reviewed. Four of these cases (8%) showed calcification in the outermost wall of the affected portion of the aorta. Two cases were Stanford type A and the other two cases were type B. In type A cases chest roentgenography showed calcification in the wall of the dilated ascending aorta closely mimicking aneurysm. In type B cases, calcification was in the outer wall of a localized hump in the descending aorta. Computed tomography clearly demonstrated that this peripheral calcification was located in the outermost wall of the false lumen. Review of the pathologic literature shows sporadic reports of such phenomenon and a theory of endothelialization of the false lumen. It is presumed that the endothelialized false lumen may develop atheromatous changes much more rapidly than the true lumen since two of four cases showed calcification only in the wall of the false lumen with the intimal flap and the wall of the true lumen remaining noncalcified.

Demonstration of Spinal Cord and Nerve Root Abnormalities by Diffusion Neurography

Objective: Diffusion-weighted magnetic resonance imaging postprocessed by maximum-intensity projection reportedly demonstrates the nerve roots. We modified this technique using a fluid-attenuated inversion-recovery-based diffusion-tensor scan using parallel imaging and evaluated its feasibility in demonstrating spinal cord and nerve root abnormalities. Methods: We applied this technique to 18 patients with miscellaneous pathological conditions that included multiple sclerosis, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), neurofibromatosis (NF), schwannoma, cord injury, and tethered cord. The neurographic images were visually assessed regarding the lesion depiction. Results: In each subject, not only the cord but also the nerve roots were visualized. This technique demonstrated cord plaques of multiple sclerosis (5/6 cases), enlarged nerve roots in CIDP (3/3 cases), multiple neurogenic tumors in NF (3/3 cases), and schwannoma (1/1 case). It better demonstrated nerve root abnormalities of CIDP (3/3 cases) and NF (2/3 cases) than conventional magnetic resonance images. Conclusion: This technique can effectively demonstrate most of the cord and nerve root pathology.

Hybrid of opposite-contrast magnetic resonance angiography of the brain by combining time-of-flight and black blood sequences: its value in moyamoya disease.

Objective: We assessed the value of a new magnetic resonance angiography (MRA) technique named hybrid of opposite-contrast (HOP) MRA in the diagnosis of moyamoya disease. Methods: Using a dual-echo sequence, we obtained the first echo for time-of-flight (TOF) MRA followed by the second echo for black blood MRA. We then subtracted the black blood MRA data set from that of the TOF MRA followed by maximum-intensity projection. In 14 patients, we performed HOP MRA and compared the findings with those on 3-dimensional TOF MRA and MR images. The HOP MRA was also compared with a radionuclide perfusion study (7 patients). Results: The HOP MRA technique improved the demonstration of distal arteries in 13 patients. The findings in HOP MRA correlated with MR images in 9 patients as well as with the perfusion study in 6 patients. Conclusions: The HOP MRA technique demonstrated the distal arterial branches in moyamoya disease well and facilitated the perfusion assessment with MR imaging.