Purpose: The purpose of this study was to assess the potential role of diffusion-weighted imaging (DWI) using low and high b-values to detect rectal cancer.
Methods: The subjects were 15 patients diagnosed endoscopically with rectal cancer (m in 1 patient, sm in 0, mp in 3, ss in 7, se in 1, a in 3) and 20 patients diagnosed endoscopically with colon cancer and no other lesions (control group). Magnetic resonance imaging was performed using a 1.5T system. DWI was performed in the axial plane using echo planar imaging sequence (repetition time/echo time 1200/66, field of view 306×350 mm, reconstruction matrix 156×256, pixel size 2.0×1.4×8.0 mm) and acquired with 2 b-values (50 and 800 s/mm²). Low and high b-value DW images were analyzed visually. A lesion was positive by detection of a focal area of high signal in the rectum in high b-value images. The apparent diffusion coefficient (ADC) values of areas of high signal in high b-value images were calculated from the low and high b-value images.
Results: High b-value images enabled visualization of all 15 rectal cancers. In the control group, 13 cases were classified as negative and 7 cases as positive for rectal cancer. Sensitivity for detection of rectal cancer was 100% (15/15), and specificity was 65% (13/20). The mean ADC values in 7 patients with false-positive lesions and in 15 patients with rectal cancer were 1.374×10^-3 mm²/s (standard deviation [SD]: 0.157) and 1.194×10^-3 mm²/s (SD: 0.152), respectively (P=0.026).
Conclusion: DWI with low and high b-values may be used to screen for rectal cancer.

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q-space diffusion analysis is a method to obtain the probability density function of the translational displacement of diffusing water molecules. Several quantities can be extracted from the function that indicate a characteristic of the water diffusion in tissue, e.g., the mean displacement of the diffusion, probability for zero displacement, and kurtosis of the function. These quantities are expected to give information about the microstructure of tissues in addition to that obtained from the apparent diffusion coefficient (ADC); however, this method requires high q (i.e., high b) values, which are undesirable in practical applications of the method using clinical magnetic resonance (MR) imaging equipment. We propose a method to obtain certain quantities that indicate a characteristic of the diffusion and that uses low q-value measurements. The quantities we can obtain are the moments of translational displacement, R; the n-th order moment is defined as the average of Rⁿ (n: integer). Kurtosis can also be calculated from the second and fourth moments. We tried to map the moments and kurtosis using clinical MR imaging equipment. We also estimated the inherent errors of the moments obtained. Our method requires precision in measuring spin echo signals and setting q values rather than using high q-value measurements. Although our results show that further error reductions are desired, our method is workable using ordinary clinical MR imaging equipment.

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Purpose: We explored appropriate scan timing for bone marrow imaging enhanced using superparamagnetic iron oxide (SPIO) and evaluated the usefulness of SPIO in differentiating metastasis and osteomyelitis in patients.
Methods: To determine the adequate scan timing after administration of SPIO, 5 healthy subjects were examined using a 1.5T magnetic resonance (MR) imaging scanner. Sagittal images of their lumbar spines were obtained using short-TI inversion recovery (STIR) sequence before and 3, 6, 9, 24, and 48 hours after intravenous injection of 8 μmol Fe/kg SPIO (ferucarbotran). MR signal intensities (SIs) were evaluated. Based on the results, 12 patients, five with bone metastasis and seven with vertebral osteomyelitis, were examined using the same procedure before and 3 hours after intravenous injection of ferucarbotran at the same dose. SIs of the bone metastases, osteomyelitis, and surrounding normal bone marrow were measured, and relative enhancement (RE) was calculated for each lesion.
Results: In the healthy volunteers, maximum reduction in signal was observed 3 to 24 hours (P<0.05) after administration of SPIO; thereafter and up to 48 hours, the SI gradually recovered. In the patients, the RE of the bone metastases was −12.2%, which was significantly higher than that in the osteomyelitis (−35.0%, P<0.001) and normal bone marrow (−46.6%, P<0.0005).
Conclusion: Maximum suppression of signal intensity in bone marrow was seen 3 hours after injection of ferucarbotran, the point at which ferucarbotran allows differentiation of bone metastasis from ostoemyelitis.

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Purpose: To investigate age-related changes in the locus ceruleus (LC) in healthy subjects using neuromelanin magnetic resonance (MR) imaging at 3 Tesla.
Methods: We examined 64 healthy volunteers (aged 23 to 80 years) using neuromelanin-sensitive T₁-weighted images and measured the contrast of areas of high signal intensity corresponding to the LC.
Results: A pair of punctate areas of high signal intensity that represented neuromelanin within the noradrenergic neurons of the LC was easily recognized in all subjects. The contrast ratio of the LC to the adjacent pontine tegmentum increased to the age of 40 to 59 years and gradually and significantly decreased in elderly subjects. This correlates well with pathologically proven age-related changes in neuromelanin content within the LC.
Conclusion: Age-related variance should be considered when determining the existence of abnormalities in the LC.

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A tetrahedral gradient diffusion sequence for body imaging for a 1.5T scanner was implemented, and we compared the quality of images acquired with the new technique and with the conventional orthogonal technique. Image quality was better using the tetrahedral technique in terms of signal homogeneity in the right liver lobe and signal loss artifact in the left lobe, and the technique was considered useful for magnetic resonance imaging in the upper abdomen.

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One diagnostic criterion for metabolic syndrome is obesity from the accumulation of visceral fat; others include abdominal circumference and area of visceral fat as measured by computed tomography (CT) at the umbilical level. We evaluated visceral fat using frequency-selective excitation magnetic resonance (MR) imaging SPAIR (spectral attenuation with inversion recovery) water suppression THRIVE (3D T₁-high resolution isotropic volume examination). Fifty of 70 slices with 2-mm interval were used to render and measure volume of visceral fat ranging within 10 cm of the umbilicus; the area of visceral fat at the umbilical level was also measured. Imaging was completed using breath hold within 14 s. Image processing was easier than using CT.

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Transient lesions at the splenium of the corpus callosum (SCC) have been reported after withdrawal of specific antiepileptic drugs (AED), though the pathophysiology of the lesions remains unclear. We examined and treated a schizophrenic patient who developed a transient SCC lesion after withdrawal of the AED, carbamazepine. Interestingly, the SCC lesion was accompanied by the onset of diabetes insipidus, a state of arginine-vasopressin (AVP) insufficiency. Because carbamazepine is shown to potentiate the effect of AVP, our case suggests that an insufficiency of AVP followed by withdrawal of AED could contribute to the pathogenesis of a transient SCC lesion.

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