• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.167-172
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• 1999

Purpose : To evaluate the detection rate of hyperacute intracerebral hemorrhage in echo planar imaging (EPI) and other MR sequences. materials and Methods : Intracerebral hemorrhage was experimentally induced in ten rats. EPI, fast spin-echo (FSE) T2 weighted images, fluid attenuated inversion recovery (FLAIR), spin-echo (SE) T1 weighted images and gradient echo (GE) T1 weight ed images of rat's brains were obtained 2 hours after onset of intracerebral hemorrhage. EPI and FSE T2 images were additionally obtained 30 min and 1 hour after onset of hemorrhage in 3 and 6 rat, repeatedly, For objective visual assessment, discrimination between the lesion and normal brain parenchyma was evaluated on various MR sequences by three radiologists. For quantitative assessment, contrast-to-noise ratio (CNR) was calculated fro hemorrhage-normal brain parenchyma. Statistical analysis was performed usning the Wilcoxon-Ranks test. Results : EPI, FLAIR, and FSE T2 images showed high signal intensity lesions. The lesion discrimination was easier on EPI than on other sequences, and also EPI showed higher signal intensity for the subjective visual assessment. In quantitative evaluation, CNR of the hemorrhagic lesion versus normal brain parenchyma were higher on EPI and FLAIR images (p<0.01). There was no difference in CNR between EPI and FLAIR (p>0.10). On MR images obtained 30 minutes and 1 hour after the onset of intracerebral hemorrhage, the lesion detection was feasible on both EPI and FSE T2 images showing high signal intensity. Conclusion : EPI showed higher detection rate as compared with other MR sequences and could be useful in early detection and evaluation of intracerebral hemorrhage.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.14 no.1
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• pp.35-42
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• 2010

A goal of Magnetic Resonance Imaging is reproducing a spatial map of the effective spin density from the measured Fourier coefficients of a specimen. The imaging procedure can be done by inverse Fourier transformation or backward fast Fourier transformation if the data are sampled on a regular grid in frequency space; however, it is still a challenging question how to reconstruct an image from a finite set of Fourier data on irregular points in k-space. In this paper, we describe some mathematical and numerical properties of imaging techniques from non-uniform MR data using the pseudo-inverse or the diagonal-inverse weight matrix. This note is written as an easy guide to readers interested in the non-uniform MRI techniques and it basically follows the ideas given in the paper by Greengard-Lee-Inati [10, 11].

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.40-40
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• 2003

The purpose of this study was to characterize focal hepatic lesions through pre and post ferucarbotran-enhanced T2 and T2＊-weighted imaging and to help differentiate benign and malignant lesions 대상 및 방법： Consecutive 34 patients with 52 hepatic lesions underwent MRI before and after intravenous bolus injection of ferucarbotran (Resovist Sobering, Berlin, Germany) for evaluation of focal hepatic lesions. Lesions included hemangiomas (n=17), metastases (n=12), cysts (n=10), hepatocellular carcinomas (n=8), dysplastic nodules (n=4), and focal fat deposit (n=1). T2-weighted fast spin echo (TR/TE： 4060/138) and gradient echo T2＊-weighted images(TR/TE： 140/5.3, FA = 90) were obtained according to the institutional routine imaging protocol. Lesional signal-intensity and lesion-to-liver contrast changes were measured by contrast-to-noise ratio (CNR) from region of interest.

• Korean Journal of Radiology
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• v.2 no.2
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• pp.63-67
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• 2001

Objective: Atrophy and a high T2 signal of the hippocampus are known to be the principal MR imaging findings of hippocampal sclerosis. The purpose of this study was to determine whether or not individual MRI findings correlate with surgical outcome in patients with this condition. Materials and Methods: Preoperative MR imaging findings in 57 consecutive patients with pathologically-proven hippocampal sclerosis who underwent anterior temporal lobectomy and were followed-up for 24 months or more were retrospectively reviewed, and the results were compared with the postsurgical outcome (Engel classification). The MR images included routine sagittal T1-weighted and axial T2-weighted spin-echo images, and oblique coronal T1-weighted 3D gradient-echo and T2-weighted 2D fast spin-echo images obtained on either a 1.5 T or 1.0 T unit. The images were visually evaluated by two neuroradiologists blinded to the outcome; their focus was the presence or absence of atrophy and a high T2 hippocampal signal. Results: Hippocampal atrophy was seen in 96% of cases (55/57) [100% (53/53) of the good outcome group (Engel class I and II), and 50% (2/4) of the poor outcome group (class III and IV)]. A high T2 hippocampal signal was seen in 61% of cases (35/57) [62% (33/53) of the good outcome group and 50% (2/4) of the poor outcome group]. All 35 patients with a high T2 signal had hippocampal atrophy. 'Normal' hippocampus, as revealed by MR imaging, occurred in 4% of patients (2/57), both of whom showed a poor outcome (Engel class III). The presence or absence of hippocampal atrophy correlated well with surgical outcome (p<0.01). High T2 signal intensity did not, however, significantly correlate with surgical outcome (p>0.05). Conclusion: Compared with a high T2 hippocampal signal, hippocampal atrophy is more common and correlates better with surgical outcome. For the prediction of this, it thus appears to be the more useful indicator.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.223-226
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• 1997

X-Ray Angiography has been gold standard for imaging of blood flow. However, patients have to take many risks such as catheterization procedure, iodine contrast agent and ionizing X-rays. MR Angiography has been suggested as a substitute for its non-hazard to patient. But the resolution and contrast was inferior to that of X-ray Angiography. Recently the resolution and the contrast have been much improved due to the development of fast imaging technique. Here we report some preliminary results of the MR Angiography we have implemented on 1 Tesla MRI unit.

• Journal of Magnetics
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• v.18 no.4
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• pp.422-427
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• 2013

The aim of this study was to investigate effects of the number of acquisitions (NEX) on signal-to-noise (SNR) and artifacts in SENSE parallel imaging of magnetic resonance imaging (MRI). 3.0T MR System, 8 Channel sensitivity encoding (SENSE) head coils were used along with an in-vivo phantom. Reference sequence of 3D fast field echo (FFE) was consisted of NEX values of 2, 4, 6, 8, 10 and 12. The T2 turbo spin echo (TSE) sequence used for exams achieved SENSE factors of 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8 and 4.0. Exams were conducted five times for each SENSE factor to measure signal intensity of the object, the posterior phase-encode direction and frequency direction. And SNR was calculated using mean values. SENSE artifacts were identified as background signal intensity in the phase-encoded direction using MRIcro. It was found that SNR increased but SENSE artifacts reduced with NEX of 4, 8 and 12 when the NEX increased in reference scan. It is therefore concluded that image quality can be improved with NEX of 4, 8 and 12 for reference scanning.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.157-160
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• 1996

In this paper, reconstruction algorithms of spiral scan imaging which has been used for ultra fast magnetic resonance imaging have been reviewed, and some simulation results using two different algorithms are reported. Since the trajectory of the spiral scan in k-space is the spiral, reconstruction of the spiral scan is not as straight forward as that used in Fourier imaging technique where the sampling points are usually on the rectangular grids. Originally the reconstruction of the spiral scan imaging was based on the convolution backprojection algorithm modified with a shift term, however, some other reconstruction techniques have also been tried by remapping sampling points from spiral trajectory to Cartesian grids. Some experimental aspects of MR spiral scan imaging will also be addressed.

• Investigative Magnetic Resonance Imaging
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• v.7 no.1
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• pp.22-30
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• 2003

Purpose : The efficacy of magnetic resonance imaging for evaluating coronary artery disease has been reported. In this study, we evaluated the usefulness of breath-hold segmented K-space cine MR imaging for evaluating the patency of coronary artery bypass grafts (CABG). Materials and Method s : Thirty eight patients with a total of 92 CABGs (36 internal thoracic arteries and 56 saphenous vein grafts) were evaluated using segmented K-space cardiac-gated fast gradient echo sequence (2D-FASTCARD) MR imaging. MR magnitude images were evaluated from the hard copies by two independent observers. A graft was defined as patent if it was seen as a bright small round area on at least two consecutive images throughout the cardiac cycle at a position consistent with the expected location for that graft. Results : MR images were obtained successfully for 23 patients (61%). The sagittal planes were most helpful in visualizing the cross-section of sapheneous vein bypass graft to left circumflex artery branch, whereas the transverse planes were used for identification of internal mammary artery grafts to left anterior descending coronary artery or its branch and identification of saphenous vein grafts to right coronary artery. Forty five grafts were visible using this MR technique, while the grafts were not visible on seven saphenous vein grafts and two internal mammary artery grafts. In two patients showing symptoms of myocardial ischemia, one or two bypass grafts were not visible. Imaging, perpendicular plane to a CABG was important to visualize the flow inside the CABG with maximum sensitivity. Conclusion : Evaluation of patency of the bypass graft was clinically feasible by 2D-FASTCARD MR imaging, whereas any invisible bypass grafts should be further studied by contrast-enhanced MR angiography or by conventional angiography for confirmation of abnormalities.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.114-114
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• 2002

Purpose： To know the fate of Gadophrin-2-enhanced areas in hearts with acute reperfused myocardial infarction. Method： The left anterior descending branches of coronary arteries were occluded for 90 min and reperfused for 60 min in 15 rabbits. Then, Gadophrin-2 (0.05 mmol/kg) was injected via ear veins. Short-axial T1-weighted spin echo images and fast cine images were obtained 24 hours after injection of Gadophrin-2. After four weeks, short-axial cine MRI was performed and T1-weighted spin echo Images were obtained 5 min and 15 min after injection of Gd-DTPA (0.2 mmol/kg). The animals were sacrificed and short-axial slices of the specimen were stained with 1.5% triphenyltetrazolium chloride (TTC) solution.

• Journal of Digital Contents Society
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• v.11 no.4
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• pp.425-431
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• 2010

This study explored the effects and the effectiveness of the new method of 3D FIESTA by making quantitative comparison with the conventional 3D FSE method which is frequently employed on patients with sudden hearing loss in clinical settings. For this study, 3D FSE images acquired with 3.0T MR scanner and T2-weighted axial plane 3D FIESTA images were respectively taken from 40 patients diagnosed with Sensorineural Hearing Loss (SSHL). When obtaining those images, sagittal reconstructions oriented perpendicular to the nerve were performed in order to get sagittal images of both right and left internal auditory canal. The findings showed that both SNR and CNR were higher among the group to whom the 3D FIESTA method was applied than the group to whom the conventional 3D FSE method was applied.