• Korean Journal of Radiology
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• v.1 no.2
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• pp.91-97
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• 2000

Objective: To determine whether the time-intensity curves acquired by test and main dose contrast injections for MR angiography are similar. Materials and Methods: In 11 patients, repeated contrast-enhanced 2D-turbo-FLASH scans with 1-sec interval were obtained. Both test and main dose timeintensity curves were acquired from the abdominal aorta, and the parameters of time-intensity curves for the test and main boluses were compared. The parameters used were arterial and venous enhancement times, arterial peak enhancement time, arteriovenous circulation time, enhancement duration and enhancement expansion ratio. Results: Between the main and test boluses, arterial and venous enhancement times and arteriovenous circulation time showed statistically significant correlation (p < 0.01), with correlation coefficients of 0.95, 0.92 and 0.98 respectively. Although the enhancement duration was definitely greater than infusion time, reasonable measurement of the end enhancement point in the main bolus was impossible. Conclusion: Only arterial and venous enhancement times and arteriovenous circulation time of the main bolus could be predicted from the test-bolus results. The use of these reliable parameters would lead to improvements in the scan timing method for MR angiography.

• Journal of Korean Neurosurgical Society
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• v.47 no.3
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• pp.203-209
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• 2010

Objective : The purpose of study was to evaluate the feasibility of brain magnetic resonance (MR) images of the rat obtained using a 1.5T MR machine in several blood-brain barrier (BBB) experiments. Methods : Male Sprague-Dawley rats were used. MR images were obtained using a clinical 1.5T MR machine. A microcatheter was introduced via the femoral artery to the carotid artery. Normal saline (group 1, n = 4), clotted autologous blood (group 2, n = 4), triolein emulsion (group 3, n = 4), and oleic acid emulsion (group 4, n = 4) were infused into the carotid artery through a microcatheter. Conventional and diffusion-weighted images, the apparent coefficient map, perfusion-weighted images, and contrast-enhanced MR images were obtained. Brain tissue was obtained and triphenyltetrazolium chloride (TTC) staining was performed in group 2. Fluorescein isothiocyanate (FITC)-labeled dextran images and endothelial barrier antigen (EBA) studies were performed in group 4. Results : The MR images in group 1 were of good quality. The MR images in group 2 revealed typical findings of acute cerebral infarction. Perfusion defects were noted on the perfusion-weighted images. The MR images in group 3 showed vasogenic edema and contrast enhancement, representing vascular damage. The rats in group 4 had vasogenic edema on the MR images and leakage of dextran on the FITC-labeled dextran image, representing increased vascular permeability. The immune reaction was decreased on the EBA study. Conclusion : Clinical 1.5T MR images using a rat depicted many informative results in the present study. These results can be used in further researches of the BBB using combined clinical MR machines and immunohistochemical examinations.

• Investigative Magnetic Resonance Imaging
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• v.22 no.2
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• pp.131-134
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• 2018

Susceptibility-weighted imaging (SWI) is well known for detecting the presence of hemorrhagic transformation, microbleeds and the susceptibility of vessel signs in acute ischemic stroke. But in some cases, it can provide the tissue perfusion state as well. We describe a case of a patient with hyperacute ischemic infarction that had a slightly hypodense, patchy lesion at the left thalamus on the initial SWI, with a left proximal posterior cerebral artery occlusion on a magnetic resonance (MR) angiography and delayed time-to-peak on an MR perfusion performed two hours after symptom onset. No obvious abnormal signals at any intensity were found on the initial diffusion-weighted imaging (DWI). On a follow-up MR image (MRI), an acute ischemic infarction was seen on DWI, which is the same location as the lesion on SWI. The hypointensity on the initial SWI reflects the susceptibility artifact caused by an increased deoxyhemoglobin in the affected tissue and vessels, which reflects the hypoperfusion state due to decreasing arterial flow. It precedes the signal change on DWI that reflects a cytotoxic edema. This case highlights that, in some hyperacute stages of ischemic stroke, hypointensity on an SWI may be a finding before the hyperintensity is seen on a DWI.

• Proceedings of the KSMRM Conference
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• 1996.03a
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• pp.4-5
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• 1996

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 1999.02a
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• pp.10-10
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• 1999

• The Korean Journal of Nuclear Medicine
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• v.38 no.2
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• pp.205-208
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• 2004

The two major classes of magnetic resonance (MR) contrast agents are paramagnetic contrast agents, usually based on chelates of gadolinium generating T1 positive signal enhancement, and super-paramagnetic contrast agents that use mono- or polycrystalline iron oxide to generate strong T2 negative contrast in MR images. These paramagnetic or super-paramagnetic complexes are used to develop new contrast agents that can target the specific molecular marker of the cells or tan be activated to report on the physiological status or metabolic activity of biological systems. In molecular imaging science, MR imaging has emerged as a leading technique because it provides high-resolution three-dimension maps of the living subject. The future of molecular MR imaging is promising as advancements in hardware, contrast agents, and image acquisition methods coalesce to bring high resolution in vivo imaging to the biochemical sciences and to patient care.

• Korean Journal of Radiology
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• v.1 no.3
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• pp.142-151
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• 2000

Objective: To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time. Materials and Methods: Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods. Results: Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method. Conclusion: The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.

• Journal of the Korean Magnetic Resonance Society
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• v.5 no.2
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• pp.110-117
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• 2001

$^{19}$ F imaging of mice was carried out. For $^{19}$ F imaging, 5-flouro-uracil (5-FU) was injected into a mouse and in vivo detection of the catabolism of 5-FU to a-fluoro-P-alanine (FBAL) was carried out. The chemical shift selective (CHESS) imaging technique was employed. The 19F spectra and images give temporal and spatial information of the metabolism for 5-FU in mice.

• Proceedings of the KSMRM Conference
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• 1997.03a
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• pp.125-135
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• 1997

• Clinics in Shoulder and Elbow
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• v.18 no.4
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• pp.211-216
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• 2015

Background: Few studies have investigated magnetic resonance (MR) characteristics of traumatic posterosuperior rotator cuff tears involving the supraspinatus and infraspinatus. We hypothesized that traumatic rotator cuff tears may have MR characteristics distinguishable from those of non-traumatic tears. Methods: Preoperative MR arthrography and intraoperative tear size measurements were compared in 302 patients who underwent MR arthrography and subsequent arthroscopic rotator cuff repairs for traumatic (group T, 61 patients) or non-traumatic (group NT, 241 patients) tears. The inclusion criteria for both groups were posterosuperior full-thickness rotator cuff tear and age between 40 and 60 years. For group T, traumas were limited to accidental falls or slips, or sports injuries, motor vehicle accidents; injuries were associated with acute onset of pain followed by functional shoulder impairment; and time between injury and magnetic resonance imaging (MRI) was 6 weeks or less. Results: In group T, 72.1% of shoulders (44 patients) had tendon tears with blunt edges while 27.9% of shoulders (17 patients) had tears with tapering edges. In contrast, 21.2% of patients in group NT (51 patients) had blunt-edge tears, while 78.8% (190 patients) of tears had tapering edges. These results were statistically significant (p<0.001) and estimated odds ratio was 9.6. The size of tear did not vary significantly between groups. Conclusions: We found no exclusive MR characteristic to define traumatic tears. However, oblique coronal MRI of traumatic tears showed a significant tendency for abrupt and rough torn tendon edges and relatively consistent tendon thicknesses (without lateral tapering) compared to non-traumatic cuff tears.