• Journal of radiological science and technology
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• v.38 no.2
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• pp.115-120
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• 2015

To study the differences of focal liver lesion image detection at 3 minute, 10 minute and 15 minute time points on gadoxetic acid (GA)'s enhanced MR imaging with a flip angle (FA) of $30^{\circ}$ compared with a $11^{\circ}$. The subjects were 69 patients evaluated with GA enhanced MR imaging with 3.0T MR scanner. The patients are total 35(23 men and 7 women at the mean age of 60.4 years), hepatocellular carcinoma(23) and metastsis(12) except for normal, cyst and hemangioma. After GA was injected, FA $11^{\circ}$ and $30^{\circ}$ images were obtained at 3 minute, 10 minute and 15 minute time points respectively. After quantitative and qualitative assessment of each image was done, statistical analysis was performed by using the independent sample T-test. From both quantitative and qualitative assessment of 3 minute and 10 minute MR images after the injection of GA, FA $30^{\circ}$ images was found to be superior than FA $11^{\circ}$, but there were no statistical significance. However, at 15 minute time point, Statistically significant FA $30^{\circ}$ image(p<0.05) was better than FA $11^{\circ}$ therefore, the FA $30^{\circ}$ improves the focal liver lesion detection. FA $30^{\circ}$ of MR image can detect liver lesion more sensitively than the existing $FA11^{\circ}$ image after GA contrast enhancement at 15 minute time point.

• Investigative Magnetic Resonance Imaging
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• v.13 no.1
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• pp.31-39
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• 2009

Purpose : This study proposes the keyhole method in order to improve the time resolution of the proton resonance frequency(PRF) MR temperature monitoring technique. The values of Root Mean Square (RMS) error of measured temperature value and Signal-to-Noise Ratio(SNR) obtained from the keyhole and full phase encoded temperature images were compared. Materials and Methods : The PRF method combined with GRE sequence was used to get MR temperature images using a clinical 1.5T MR scanner. It was conducted on the tissue-mimic 2% agarose gel phantom and swine's hock tissue. A MR compatible coaxial slot antenna driven by microwave power generator at 2.45GHz was used to heat the object in the magnetic bore for 5 minutes followed by a sequential acquisition of MR raw data during 10 minutes of cooling period. The acquired raw data were transferred to PC after then the keyhole images were reconstructed by taking the central part of K-space data with 128, 64, 32 and 16 phase encoding lines while the remaining peripheral parts were taken from the 1st reference raw data. The RMS errors were compared with the 256 full encoded self-reference temperature image while the SNR values were compared with the zero filling images. Results : As phase encoding number at the center part on the keyhole temperature images decreased to 128, 64, 32 and 16, the RMS errors of the measured temperature increased to 0.538, 0.712, 0.768 and 0.845$^{\circ}C$, meanwhile SNR values were maintained as the phase encoding number of keyhole part is reduced. Conclusion : This study shows that the keyhole technique is successfully applied to temperature monitoring procedure to increases the temporal resolution by standardizing the matrix size, thus maintained the SNR values. In future, it is expected to implement the MR real time thermal imaging using keyhole method which is able to reduce the scan time with minimal thermal variations.

• Journal of Biomedical Engineering Research
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• v.31 no.2
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• pp.94-98
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• 2010

In magnetic resonance electrical impedance tomography (MREIT), a current-injection MR imaging method is adopted to produce a cross-sectional image of an electrical conductivity distribution in addition to MR images. The purpose of this study was to test the feasibility of MREIT for differentiating the canine lung parenchyma without and with pneumonia. Three normal healthy beagles and two mixed breed dogs with pneumonia were used. After attaching electrodes around the chest, we placed the dog inside our MR scanner. We injected as much as 30 mA current in a form of short pulses into the chest region. Reconstructed conductivity images of normal canine lungs exhibit a peculiar pattern of a relatively coarse salt and pepper noise. On the contrary, conductivity images of pneumonic canine lungs show significantly enhanced contrast of the lesions while the corresponding MR images show a little bit of contrast in the middle and caudal lung parenchyma due to the accumulation of pleural fluid. This preliminary study indicates that MREIT imaging of the chest may deliver unique new diagnostic information.

• Imaging Science in Dentistry
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• v.49 no.1
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• pp.53-58
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• 2019

Purpose: To present characteristic findings of Tc-99m hydroxymethylene diphosphonate (HMDP) scintigraphy, computed tomography (CT), and magnetic resonance (MR) imaging for osteonecrosis in the mandible, especially osteoradionecrosis(ORN) and medication-related osteonecrosis of the jaw(MRONJ). Materials and Methods: Thirteen patients with MRONJ and 7 patients with ORN in the mandible underwent Tc-99m HMDP scintigraphy, CT, and MR imaging (T1-weighted images[T1WI], T2-weighted images[T2WI], short inversion time inversion recovery images[STIR]), diffusion-weighted images[DWI], and apparent diffusion coefficient [ADC] mapping). The associations of scintigraphy, CT, and MR imaging findings with MRONJ and ORN were analyzed using the chi-square test with the Pearson exact test. Results: Thirteen patients with MRONJ and 7 patients with ORN in the mandible showed low signal intensity on T1WI and ADC mapping, high signal intensity on STIR and DWI, and increased uptake on scintigraphy. Periosteal bone proliferation on CT was observed in 69.2% of patients with MRONJ(9 of 13) versus 14.3% of patients with ORN(1 of 7)(P=0.019). Conclusion: This study presented characteristic imaging findings of MRONJ and ORN on scintigraphy, CT, and MR imaging. Our results suggest that CT can be effective for detecting MRONJ and ORN.

• Korean Journal of Radiology
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• v.2 no.4
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• pp.183-191
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• 2001

Objective: To document the signal characteristics of intracerebral hemorrhage (ICH) at evolving stages on diffusion-weighted images (DWI) by comparison with conventional MR images. Materials and Methods: In our retrospective study, 38 patients with ICH underwent a set of imaging sequences that included DWI, T1-and T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR). In 33 and 10 patients, respectively, conventional and echo-planar T2^* gradient-echo images were also obtained. According to the time interval between symptom onset and initial MRI, five stages were categorized: hyperacute (n=6); acute (n=7); early subacute (n=7); late subacute (n=10); and chronic (n=8). We investigated the signal intensity and apparent diffusion coefficient (ADC) of ICH and compared the signal intensities of hematomas at DWI and on conventional MR images. Results: DWI showed that hematomas were hyperintense at the hyperacute and late subacute stages, and hypointense at the acute, early subacute and chronic stages. Invariably, focal hypointensity was observed within a hyperacute hematoma. At the hyperacute, acute and early subacute stages, hyperintense rims that corresponded with edema surrounding the hematoma were present. The mean ADC ratio was 0.73 at the hyperacute stage, 0.72 at the acute stage, 0.70 at the early subacute stage, 0.72 at the late subacute stage, and 2.56 at the chronic stage. Conclusion: DWI showed that the signal intensity of an ICH may be related to both its ADC value and the magnetic susceptibility effect. In patients with acute stroke, an understanding of the characteristic features of ICH seen at DWI can be helpful in both the characterization of intracranial hemorrhagic lesions and the differentiation of hemorrhage from ischemia.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.108-108
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• 2001

Purpose： To correlate the histological differentiation of hepatocellular carcinomas (HCCs) with finding on triple contrast-enhanced MR imaging using gadolinium-chelates, superparamganetic ire oxides (SPIO), and mangafodipir trisodium. Method： Ten patients with proven HCC underwent triple contrast-enhanced MRI befo surgical resection. Subjective ratings of the enhancement pattern and degree were compare with the histological grades determined on surgical specimen. Quantitative measurements signal-to-noise ratio (S/N) of the lesion and the lesion-to-liver contrast-to-noise ratio C/N on the enhanced MR images, and the degree of S/N and C/N changes between the unenhanced and enhanced images were also correlated with the histological grades.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.305-306
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• 1998

In this paper, we infer the onset of the brain infarction from the MR image using evaluate signal intensities on diffusion weighted and turbo spin echo T2-weighted and FLAIR images. Infarcts were divided into four stages (hyperacute, acute, subacute, chronic) depending on period of onset. DWI is useful for the detection of early ischemic infarct, and stages of ischemic infarctions can be estimated by evaluating CR(conspicuity ratio) and CNR(contrast to noise ratio) on DW, T2, FLAIR images Hyperacute infarcts were visualized DWI. Acute infarcts were visualialized both DWI and T2 Weighted image.

• Imaging Science in Dentistry
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• v.38 no.1
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• pp.57-62
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• 2008

The Warthin tumor is a benign neoplasm that occurs mostly in the parotid gland. The tumor frequently occurs in the tail of the parotid gland. A 75-year-old man was referred to Wonkwang dental hospital with a chief complaint of swelling on the right submandibular area. Numerous salivary stones were observed in the right submandibular gland on computed tomography (CT). And the two tumorous lesions were incidentally found in the parotid gland bilaterally. The tumorous lesions showed homogeneous enhancement on the CT and intermediate signal intensity on both T1- and T2-weighted magnetic resonance (MR) images. This tumorous lesions also showed contrast enhancement on fat suppressed T1 weighted MR images. We report common CT and MR features of this case of Warthin tumor in the parotid gland with literature review.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.4
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• pp.203-207
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• 2013

The appropriate handling of motion artifacts is essential for clinical diagnosis in magnetic resonance imaging (MRI). In many cases, motion is an inherent part of MR images because it is difficult to control during MR imaging. As the motion in the human body occur in a deformable manner, they are difficult to deal with. This paper proposes a novel detection method for periodically moving regions to produce MR images with less motion artifacts. When the data is acquired by the radial trajectory, the proposed method can extract the deformable region easily using the difference in the modulated sinograms, which have different periodic phase terms. The simulation results applied to the various cases confirmed the good performance of the proposed method.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.135-135
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• 2002

Purpose： To assess diagnostic accuracy of dynamic contrast enhanced MR mammography in differentiating between benign and malignant lesions. Materials and methods： Ninety-three patients with suspicious mammographic, sonographic or palpable findings underwent pre- or postoperative contrast-enhanced MR imaging of breast using three dimensional fast low-angle shot (3D FLASH) sequence (16/4 msec［repetition time / echo time］, 20 flip angle, 3mm slice thickness with no slice gap, 256 by 256 in-plane matrix) covering whole breasts. T1 weighted images were obtained before and after bolus administration of gadopentetate dimeglumine (0.15 mmol/kg). Subtraction images and time-signal intensity curves of region of interest were obtained sequentially and correlated with pathologic diagnoses of lesions.