PURPOSE: To investigate the applicability of the new three-dimensional overlapped reconstruction MR angiography (3-D ORMRA) technique in patients with hemifacial spasm and to compare the new 3-D reconstruction images with conventional MRA source images. MATERIALS AND METHODS: The study group comprised 27 patients with surgically proven hemifacial spasm. In all patients, conventional MRA source images and 3-D fast imaging employing steady-state acquisition (FIESTA) images were obtained prospectively. After 3-D MR angiographic images were obtained, the 3-D MRA and FIESTA images were overlapped at the workstation by using GE A/W 4.2 add/sub software. We analyzed the relationship between the offending vessels and root exit zone of the facial nerve using both 3-D ORMRA images and conventional MRA source images. RESULTS: In 25 of 27 patients, the offending vessel at the REZ of the facial nerve could be correctly identified on conventional MRA source images. In all patients, the presumed offending vessels depicted by the overlapped 3-D reconstruction MRA image corresponded well with the intraoperative findings. The 3-D reconstruction image showed more clear visualization of the spatial relationship between the offending vessels and the root exit zone of the facial nerve. CONCLUSION: The overlapped 3-D reconstruction MR angiography technique is very useful and informative in patients with hemifacial spasm, as compared with conventional MRA angiography technique.
Angiography ; Facial Nerve ; Hemifacial Spasm* ; Humans ; Prospective Studies

PURPOSE: To evaluate the mucoid degeneration (MD) of the anterior cruciate ligament (ACL) of the knee by correlation of MRI findings with pathology, in the patients with osteoarthritis (OA). MATERIALS AND METHODS: This study included 17 patients (mean 68.8 years old) who underwent preoperative MRI. In proton density-weighted sagittal and coronal images ACLs were evaluated for the thickness and signal intensity (SI). Total knee replacement arthroplasty was performed and the pathologic findings of ACL were evaluated. MD was classified as 3 grades according to the degenerated amount in microscopy. Thickness and SI was evaluated as normal or increased on MRI. RESULTS: All of the 4 patients who showed thickened ACL showed increased SI on MRI. All of the 8 patients with increased SI of the ACL on MRI had MD in the ACL. However, remained 9 patients also had MD, in spite of their normal thickness and SI on MRI. Calcification was seen in 5 patients. CONCLUSION: Eight cases who showed ACL thickening or increased SI on MRI were well correlated with MD, however, because the other nine cases who showed normal thickness and normal SI of ACL on MRI also showed MD in pathology, normal MRI finding should not exclude the possibility of MD of ACL.
Anterior Cruciate Ligament* ; Arthroplasty ; Arthroplasty, Replacement, Knee ; Humans ; Knee* ; Magnetic Resonance Imaging* ; Microscopy ; Osteoarthritis* ; Pathology ; Protons

PURPOSE: The purpose of the present study was to develop and optimize solenoid coil for animal- model in 3 T MRI system and investigate and compare with the birdcage coil concerning the image quality with the various parameters such as SNR and Q-factor. MATERIALS AND METHODS: Solenoid coil for animal-model was made on the acryl structure (diameter 4 cm, length 10 cm) 3 times-winding cooper tape of width 2 cm , thickness 0.05 cm and length 10 cm with 2 cm interval between winded tapes. Capacitors from 2 pF to 100 pF were used, and the solenoid coil was designed for receiver only coil. RESULTS: SNR of the developed solenoid was 985 in CuSO4 0.7 g/L and 995 in rat experiment. Q-factor was 84-89 in unloaded condition and 203-206 in loaded condition. CONCLUSION: The resolution of the image obtained from solenoid was relatively higher than that of the conventional birdcage coil. In addition, the homogeneity of RF field by coil simulation was significantly excellent. The present study demonstrated that the solenoid coil could be useful to obtain small animal images with better contrast, resolution, visibility than images from birdcage.
Animals* ; Magnetic Fields* ; Magnetic Resonance Imaging* ; Rats ; Wind

Conventional MRI methods using T1-, T2-, diffusion-, perfusion-weighting, and functional imaging rely on characterizing the physical and functional properties of the tissue. In this review, we introduce an imaging modality based on measured the mechanical properties of soft tissue, namely magnetic resonance elastography (MRE). The use of palpation to identify the stiffness of tissue remains a fundamental diagnostic tool. MRE can quantify the stiffness of the tissue thereby providing a objective means to measure the mechanical properties. To accomplish a successful clinical setting using MRE, hardware and software techniques in the area of transducer, pulse sequence, and imaging processing algorithm need to be developed. Transducer, a mechanical vibrator, is the core of MRE application to make wave propagate invivo. For this reason, considerations of the frame of human body, pressure and friction of the interface, and high magnetic field of a MRI system needs to be taken into account when designing a transducer. Given that the wave propagates through human body effectively, developing an appropriate pulse sequence is another important issue in obtaining an optimal image. In this review paper, we introduce the technical aspects needed for MRE experiments and introduce several applications of this new field.
Elasticity Imaging Techniques* ; Friction ; Human Body ; Magnetic Fields ; Magnetic Resonance Imaging ; Palpation ; Transducers

The obstacles for cardiac imaging are motion artifacts due to cardiac motion, respiration, and blood flow, and low signal due to small tissue volume of heart. To overcome these obstacles, fast imaging technique with ECG gating is utilized. Cardiac exam using MRI comprises of morphology, ventricular function, myocardial perfusion, metabolism, and coronary artery morphology. During cardiac morphology evaluation, double and triple inversion recovery techniques are used to depict myocardial fluidity and soft tissue structure such as fat tissue, respectively. By checking the first-pass enhancement of myocardium using contrast-enhanced fast gradient echo technique, myocardial blood flow can be evaluated. In addition, delayed imaging in 10-15 minutes can inform myocardial destruction such as chronic myocardial infarction. Ventricular function including regional and global wall motion can be checked by fast gradient echo cine imaging in quantitative way. MRI is acknowledged to be practical for integrated cardiac evaluation technique except coronary angiography. Especially delay imaging is the greatest merit of MRI in myocardial viability evaluation.
Artifacts ; Coronary Angiography ; Coronary Vessels ; Electrocardiography ; Heart ; Magnetic Resonance Imaging* ; Metabolism ; Myocardial Infarction ; Myocardium ; Perfusion ; Respiration ; Ventricular Function

PURPOSE: In functional MRI(fMRI), the acoustic noise effects of gradient pulsing are analyzed with two different combinations of readout and phase-encoding gradients for sagittal-view images. MATERIALS AND METHODS: Series of sagittal-view EPI images for fMRI obtained from five healthy volunteers. In order to show the effect of gradient pulsing noise, this study was duplicated for the Y readout / Z phase-encoding gradients and the Z readout / Y phase-encoding gradients. The first 7 images were obtained with visual stimulation. This sequential paradigm without and with visual stimulation was repeated 4 times, and was followed by the last 7 images being obtained without visual stimulation. In order to compare the visual cortex activation according to the combination of readout and phase-encoding gradients, the number of activated pixels and the average intensities of the activated pixels were analyzed, where the total activation is defined by multiplying the number of activated pixels by the average intensities of the activated pixels. RESULTS: The experimental results show that the combination of Z readout and Y phase-encoding gradients produce larger visual cortex activation than the combination of Y readout and Z phase-encoding gradients when a sagittal-view fMRI is performed. CONCLUSION: This experiment result represents that visual cortex response can be affected by acoustic noise. Therefore, the combination of the Z readout and Y phase encoding gradients is efficient for sagittal view fMRI because it has less acoustic noise.
Acoustics* ; Angiography* ; Healthy Volunteers ; Magnetic Resonance Imaging* ; Noise* ; Photic Stimulation ; Visual Cortex

PURPOSE: To investigate the relativethe signal difference. Also this optimal angle increased as TR increased. The optimal flip angles varied along with [Gd] concentration such that high concentration allowed larger flip angle. The experiment revealed similar results and confirmed the results obtained from simulation. Both simulation and experimental results suggest that the optimization scheme of imaging parameters for maximum signal difference, which gives best vessel visualization, is very close to that for maximizing blood signal alone for short TR application of contrast enhanced MRA. CONCLUSION: To improve the vessel visualization, it is necessary to optimize the imaging parameters. The expected optimal flip angle is very close to Ernst angle. Higher [Gd] concentration and longer TR, if allowed, will give rise to higher blood signal.
Acoustics* ; Angiography* ; Healthy Volunteers ; Magnetic Resonance Imaging* ; Noise* ; Photic Stimulation ; Visual Cortex

PURPOSE: To document the relative usefulness of true Fast-imaging steady-state precession(FISP) comparing to breath-hold turbo spin-echo(TSE), and half-Fourier single-shot turbo spin-echo(HASTE) as a fast T2-weighted sequence during hepatic MR imaging. MATERIALS AND METHODS: For 46 patients with 87 focal hepatic lesions(hepatocellular carcinoma, n=26; metastasis. n=5; cavernous hemangioma, n=37; cyst, n=19), we obtained MR imaging of the liver at 1.5T. True FISP, TSE with and without fat-suppresion(FS), and HASTE with and without FS images were obtained during one breath-hold. Images were compared on the basis of tumor detectability and lesion-to-liver contrast-to-noise ratio(CNR). Qualitative analysis of each imaging sequence was also performed in terms of hepatic contour, visibility of vascular landmarks and imaging artifacts. RESULTS: TSE-FS depicted more focal lesions(78/87, 90%) than other sequences(TSE, 75/87=86%;HASTE, 74/87=85%; HASTE-FS, 75/87=86%;true FISP,73/87=84%). However, there was no statistical significance between each sequence(p> .05). Using true FISP or HASTE, there was a statistically significant difference(p< .01) between the CNRs of solid tumors, crystal and hemangiomas. Additionally, true FISP sequence showed better hepatic contour, vascular landmarks and less artifacts comparing with TSE or HASTE regardless of FS(p< .001). CONCLUSION: True FISP sequence allows differentiation between solid tumors, hemangiomas and cystic lesions in terms of CNR, and provides better imaging quality than other fast T2-weighted MR sequences.
Artifacts ; Hemangioma ; Hemangioma, Cavernous ; Humans ; Liver* ; Magnetic Resonance Imaging* ; Neoplasm Metastasis

PURPOSE: To analyze the enhancement patterns of adenomyosis and evaluate the usefulness of dynamic MR imaging in detecting adenomyosis. MATERIALS AND METHODS: Dynamic MR imaging finding in 46 women with adenomyosis were analyzed retrospectively. Dynamic MR imaging was obtained in each patient. Fifteen consecutive FLASH images were obtained before, immediately after and 15, 30, 45, 90 second and 5 minute after bolus injection of Gd-DOTA. Signal intensities of adenomyosis and outer myometrium and standard deviations of image noise were measured using an electronic cursor. Contrast-to-noise ratio (C/N) of the lesion to outer myometrium were calculated as follows ; (signal intensity of outer myometrium-signal intensity of adenomyosis)/(standard deviation) of noise signal intensity. RESULTS: The mean signal intensity of adenomyosis was higher than surrounding outer myometrium before and immediately after contrast injection. On 15, 30, 45, 90 second, and 5 minute after injection the signal intensity of adenomyosis was lower than that of surrounding outer myometrium (p < 0.05). The mean C/N values between adenomyosis and surrounding myometrium on precontrast scan, immediate postcontrast, and 15, 30, 45, 90 second and 5 minute delayed images were 3.20, 5.03, 6.14, 6.87, 7.13, 7.78, 38.59, respectively. On T2-weighted images, the mean C/N value between adenomyosis and surrounding myometrium was 16.7. Mean C/N value between adenomyosis and surrounding myometrium on delayed images was significantly higher than those of other dynamic & T2-weighted images(p<0.05). CONCLUSION: Dynamic MR imaging is very useful in the evaluation of the enhancement pattern and especially in detection of adenomyosis because the mean C/N value between adenomyosis and surrounding myometrium on delayed images are higher than that of T2-weighted images.
Adenomyosis* ; Animals ; Female ; Humans ; Magnetic Resonance Imaging* ; Mice ; Myometrium ; Noise ; Retrospective Studies ; Uterus*

PURPOSE: To apply a distributed circuit theory, to develop a head-size transverse electromagnetic(TEM) resonator coil for a home-built 3T whole-body MRI system and to report an efficiency of the coil. MATERIALS AND METHODS: The dimension of TEM resonator with 16 cavity element, the diameter of copper rod was 0.63cm and its length was 13.75cm. As raw materials, the purity of copper rod was 98% and the dielectric constant of teflon was 2.08. RESULTS: The TEM head-size resonator with 16cavity elements exhibiting 9-mode resonances was robust to the surrounding influences owing to the self-shielding structure. The isolation of quadrature with a human brain was 364 and the ratio of Q(unloaded/Q(loaded) was 2.9. CONCLUSION: It was successfully demonstrated that the TEM head-size resonator with high Q factor can provide high quality MR images at 3T MRI system. Also, the TEM resonator coil has an advantage for a fine tune with length adjustment of each cavity elements. Thus, it is expected that the TEM resonator at 3T, even higher field could be used in the clinical and research studies in near future.
Brain ; Copper ; Head* ; Humans ; Magnetic Resonance Imaging* ; Polytetrafluoroethylene