Purpose: To elucidate changes in the diffusion properties of muscle fiber between rest and active contraction.
Methods and Materials: In 10 healthy adult volunteers (4 men, 6 women), we obtained diffusion tensor (DT) images (b=500 s/mm²) of bilateral calves using a 1.5-tesla clinical magnetic resonance (MR) imager. We first simultaneously scanned both calves at rest, then obtained scans of bilateral calves with plantar flexion of the right ankle using the same imaging parameters. We measured fractional anisotropy (FA) and λ₁, λ₂, and λ₃ in the gastrocnemius medialis (GCM) and anterior tibialis (AT) muscles of both calves by seeding the region of interest at the thickest part, then calculated the right-to-left ratio of the FA and eigenvalues in each muscle and compared each ratio between rest and contraction by paired t-test.
Results: In the GCM, the FA ratio increased from 1.05 at rest to 1.17 after contraction, and contraction elevated the λ1 and 2 ratios from 0.99 in resting muscles to 1.06 (λ₁) and 1.07 (λ₂). In contrast, the AT showed a decrease of the λ₁ ratio from 0.99 at rest to 0.96 at elongation and of the λ₂ ratio, from and 1.01 at rest to 0.94 at elongation. Statistically significant differences were observed in the FA (P<0.05), λ1 and λ2 (P<0.01) in the GCM, and the λ1 and λ2 (P<0.05) in the AT.
Conclusion: The higher FA and λ₁ and λ₂ values of muscles at contraction than rest presumably reflect complicated changes, including microscopic morphological changes of the diffusion-restricting factor, focal temperature, and perfusion. We found that change in perfusion could affect the AT, and changes in focal perfusion and temperature could influence the GCM.

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Purpose: We examined the hypothesis that the fat-saturation pulse in a global off-resonance state caused by magnetic field (B₀) drift produced signal fluctuation in echo planar imaging (EPI) time series.
Methods: We performed 3 experiments using 2 types of phantoms, one of which was homemade and contained water and a well emulsified fat source.
Results: We found that B₀ drift was approximately +30 Hz in the first 30-min EPI time series and +15 Hz in the second series. We experimentally reproduced the signal fluctuations observed during actual measurement in an artificial global off-resonance state using a fat-saturation pulse, the frequency profile of which also affected the pattern of fluctuation.
Conclusion: These results are direct evidence that the fat-saturation pulse is a source of signal fluctuation in the presence of B₀ drift.

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Purpose: T₁-shortening of labyrinthine fluid on 3-dimensional fluid-attenuated inversion recovery (3D-FLAIR) has been reported in many inner ear disorders. Although semi-quantitative assessment by simple signal intensity ratio between cochlear fluid and brain tissue has been tried, its feasibility using a multi-channel phased-array head coil with an inherently inhomogenous sensitivity distribution has not been fully evaluated. We evaluated the feasibility of measuring simple signal intensity ratio by correlating rapid T₁ measurements using an inversion time (TI) scout sequence.
Materials and Methods: We evaluated 10 patients with Meniere's disease and 4 patients with sudden deafness. Nine of the patients with Meniere's disease received a unilateral intratympanic injection of Gd-DTPA; the tenth patient received bilateral injections. The 4 patients with sudden deafness received a double-dose intravenous injection. Magnetic resonance (MR) images were obtained 24 hours after intratympanic injections and 4 hours after intravenous injections at 3 tesla using a 32-channel head coil. We measured the ratio (CM ratio) between the signal intensity of the perilymph in the cochlea (C) and that of the medulla oblongata (M) and correlated it with the null-point inversion time (TI_null) obtained with the TI scout sequence. The TI scout consisted of 85 images obtained with TI values between 132.5 and 3087.5 ms at increments of 37.5 ms.
Results: The correlation coefficient between TI_null and the natural logarithm of the CM ratio was −0.88 (P<0.01). There was significant negative linear correlation.
Conclusions: Measurement of the simple signal intensity ratio between the cochlea and the medulla can be used for semi-quantitative analysis of 3D-FLAIR. The results of this study may facilitate clinical research of inner-ear disease using 3D-FLAIR.

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Purpose: We evaluated whether enhancement of the cochlear modiolus could be visualized 24 hours after intratympanic injection of gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) using a 3-dimensional real inversion recovery sequence combined with a 32-channel head coil at 3 tesla. Intratympanic injection of Gd-DTPA has been reported for visualizing endolymphatic hydrops in Meniere's disease, and its use has shown communication between the cochlear perilymph and cerebrospinal fluid in the internal auditory canal. Although the cochlear modiolus has been considered the route for this communication, this has not been confirmed through direct visualization of its enhancement.
Materials and Methods: We qualitatively and quantitatively evaluated the presence of contrast enhancement in the modiolus in 19 patients with clinically suspected endolymphatic hydrops or hearing loss who underwent imaging as described above.
Results: The contrast ratio (CR) between the cochlear modiolus and cerebellar white matter on the injected side was 1.09±1.23, and that on the non-injected side was −0.48±0.38 (P<0.01). In all subjects, the CR value was larger on the injected than non-injected side, and enhancement of the cochlear modiolus was also recognized visually.
Conclusions: Intratympanic Gd-DTPA can be administered to visualize enhancement of the cochlear modiolus and may thereby reveal its functional anatomy.

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One disadvantage of ultrasound (US)-guided cryoablation of breast cancer is the difficulty in visualizing the area behind the ice ball because of acoustic shadowing. We performed US-guided cryoablation with the patient in prone position inside the MR room. The lumpectomy specimen after cryoablation revealed dense fibrosis without residual viable cancer cells. The combination of needle insertion under US guidance with planning and verification using magnetic resonance imaging may be a feasible and promising treatment protocol.

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