• Investigative Magnetic Resonance Imaging
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• v.12 no.2
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• pp.123-130
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• 2008

Purpose : Motion effects in parallel magnetic resonance imaging (MRI) are investigated. Parallel MRI is known to be robust to motion due to its reduced acquisition time. However, if there are some involuntary motions such as heart or respiratory motions involved during the acquisition of the parallel MRI, motion artifacts would be even worse than those in conventional (non-parallel) MRI. In this paper, we defined several types of motions, and their effects in parallel MRI are investigated in comparisons with conventional MRI. Materials and Methods : In order to investigate motion effects in parallel MRI, 5 types of motions are considered. Type-1 and 2 are periodic motions with different amplitudes and periods. Type-3 and 4 are segment-based linear motions, where they are stationary during the segment. Type-5 is a uniform random motion. For the simulation, Cartesian and spiral grid based parallel and non-parallel (conventional) MRI are used. Results : Based on the motions defined, moving artifacts in the parallel and non-parallel MRI are investigated. From the simulation, non-parallel MRI shows smaller root mean square error (RMSE) values than the parallel MRI for the periodic (type-1 and 2) motions. Parallel MRI shows less motion artifacts for linear(type-3 and 4) motions where motions are reduced with shorter acquisition time. Similar motion artifacts are observed for the random motion (type-5). Conclusion : In this paper, we simulate the motion effects in parallel MRI. Parallel MRI is effective in the reduction of motion artifacts when motion is reduced by the shorter acquisition time. However, conventional MRI shows better image quality than the parallel MRI when fast periodic motions are involved.

• Journal of the Korean Society of Radiology
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• v.84 no.2
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• pp.345-360
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• 2023

In Korea, the number of institutions providing breast MRI, as well as the number of breast MRIs, has recently increased. However, MRI-guided procedures, including biopsy and needle localization, are rarely performed compared to ultrasound-guided or stereotactic biopsy. As breast MRI has high sensitivity but limited specificity, lesions detected only on MRI require pathologic confirmation through MRI-guided biopsy or surgical excision with MRI-guided needle localization. Thus, we aimed to review MRI-guided procedures, including their indications, techniques, procedural considerations, and limitations.

• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.523-530
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• 1999

자기공명영상 (MRI)기법은 최근에 그의 이용 분야가 식품공학 및 농학 분야까지 확대되고 있다. 이 연구에서는 MRI의 기본 원리를 알아보고 어떤 요인들이 자기공명영상의 명암을 결정하는지 알아 보았다. MRI를 이용하여 비파괴적인 방법으로 농축산물의 내부 구조 영상을 얻고 이로부터 토마토의 내부 공동, 감자의 공동병, 사과와 파파야의 멍, 버찌씨의 유무, 망고와 감자의 벌레에 의한 손상, 망고와 마늘의 내부 결함, 키위의 성숙도에 따른 변화, 그리고 소고기의 내부 구조 둥을 판별할 수 있음을 알아 보았으며 농축산물의 품질을 결정짓는 이러한 내부 요인들이 어떻게 자기공명영상을 형성하는지 알아 보았다. 대상 시료에 따라 적당한 자기공명영상 인자(TR과 TE)를 선택하여야 한다. 또한 특정 인자를 강조하기 위해서는 최적의 자기공명영상 인자를 선택하여야 한다.

• Investigative Magnetic Resonance Imaging
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• v.14 no.1
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• pp.41-46
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• 2010

Purpose : To evaluate the role of magnetic resonance imaging (MRI) in the diagnosis of papillary lesions of the breast. Materials and methods : Among 45 papillary lesions diagnosed at ultrasonography-guided core biopsy (USCB), 27 benign papillary lesions in 22 patients who underwent breast MRI were reviewed. The excsional biopsy was performed in 1-10 days after MRI was done. In MRI findings, lesions were considered suspicious if they show irregular, rim enhancement, or linear enhancement in morphologic evaluation, or washout enhancement pattern of delayed phase in dynamic enhancement characteristics. Diffusionweighted images were analyzed according to visibility of lesions. MRI findings were correlated with pathologic results at excisional biopsy. Results : At excisional biopsy, two lesions (9%) were diagnosed malignant in 22 benign papillary lesions without atypia by USCB and 4 (80%) were malignant in 5 benign papillary lesions with atypia by USCB. Among 18 lesions detected on MRI, 16 lesions showed suspicious findings on MRI, 11 lesions (69%) were diagnosed as benign and 5 (31%) were malignant. Among 12 lesions detected on diffusion weighted imaging, 10 lesions were diagnosed as benign and 2 were malignant. MRI findings were not significantly correlated with pathologic results at excisional biopsy. Conclusion : MRI findings were not useful to predict malignancy in benign papillary lesions diagnosed at USCB, because MRI findings of these were mostly suspicious (88.9%, 16/18). The benign papillary lesion should be included in the false positive lesion on breast MRI.

• Investigative Magnetic Resonance Imaging
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• v.12 no.2
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• pp.161-169
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• 2008

Purpose : The aim of this study was to evaluate the usefulness of MRI performed after excisional biopsy to diagnose residual cancer and additional lesions. Materials and Methods : A total of 16 patients who had breast cancer diagnosed by excisional biopsy underwent preoperative breast MRI between March 2005 and August 2007 were included. MRI findings were considered positive for residual cancer if focal, thick, or irregular rim enhancement or adjacent enhancing lesion was identified around the postoperative biopsy cavity. And additional lesions separated from biopsy cavity including multifocal, multicentric, or contralateral lesion were evaluated. We evaluated the diagnostic accuracy of MRI, comparing MRI with histopathologic finding, and the impact of MRI on surgical planning. Results : The sensitivity and specificity of MRI for detecting residual disease considering rim enhancement were 85.7%(6/7) and 55.6%(5/9). Additional lesions including multifocal, multicentric, or contralateral lesion were found in 6 patients. In 7 patients, results of MRI findings changed surgical treatment planning. Conclusion : The pattern of rim enhancement on MRI after excisional biopsy is not differential point to evaluate remnant lesion. But MRI has an important role to help the detection of multifocal or multicentric, or contralateral breast malignancies, resulting in beneficial change in surgical treatment planning.

• Journal of the Institute of Convergence Signal Processing
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• v.16 no.2
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• pp.50-55
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• 2015

The noise of MRI shooting is 100dB loud and has an intensive psychological and physiological influences on the human body. ECG signals were measured by experimental methods, while wearing earplugs for 15 minutes in the stable state. Then the ECG signals were measured for 30 minutes while listening to about 100dB of sound in a MRI equipment. In this study, the heart rate variability of men and women was analyzed according to the MRI noise stress level through the frequency analysis. As the MRI noise level is about 100dB, HRV analysis resulted in an imbalance between the sympathetic and parasympathetic. During the period from the resting state up to 10 minutes, the maximum stress state was shown. This study will encourage MRI workers to take interests in hearing protection for the patient and to make objective indicators about MRI noises.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.63-71
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• 2008

• Journal of the Korean Society of Radiology
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• v.82 no.5
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• pp.1218-1230
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• 2021

Purpose To compare the per-patient diagnostic performance of simulated abbreviated MRI (AMRI) to that of conventional MRI (CMRI) with full-sequence dynamic gadoxetic acid (GA) enhancement for early-stage hepatocellular carcinoma (HCC) screening in high-risk patients. Materials and Methods A total of 201 consecutive patients at high-risk for HCC, who underwent 3T liver MRI, were included in this retrospective study. The AMRI protocol comprised T2-weighted imaging, hepatobiliary phase imaging after GA injection, and diffusion-weighted imaging. For each patient, two AMRI and CMRI image sets were independently reviewed by two radiologists. Inter-reader agreement was assessed using Cohen's kappa value. A composite reference standard was used to determine the diagnostic performance of each image set for each reader. Results A total of 93 HCCs were detected in 79 patients. The inter-reader agreement was almost perfect for both image sets (κ = 0.839, 0.948). In AMRI, the per-patient sensitivity and negative predictive values (NPV) were 94.9% and 96.4%, respectively. In CMRI, the per-patient sensitivity and NPV were 96.2% and 97.5%, respectively. Conclusion AMRI, using only three sequences, had a comparable diagnostic performance to CMRI in screening early-stage HCC. AMRI could be an alternative HCC screening tool for high-risk HCC patients.

• Investigative Magnetic Resonance Imaging
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• v.12 no.2
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• pp.178-187
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• 2008

Purpose : To evaluate and compare the diagnostic accuracy of MRI and ultrasound(US) for estimation of invasion depth of gastric carcinoma by correlation with histopathologic findings in vitro and to find out the best MR pulse sequence for detection and accurate delineation of tumor. Materials and Methods : Resected specimen of total or subtotal gastrectomy from 53 patients with gastric carcinoma were done of imaging studies of MRI and US. And US was examined by using high frequency linear transducer for tumor invasion depth by a radiologist. In each case, both imaging findings of MRI and US were evaluated independently for tumor detection and invasion depth by consensus of two radiologists and were compared the diagnostic accuracy between two imaging modalities according to the histopathologic findings. MR imaging with five MR pulse sequences, spin echo T1 and in- and out-of phase gradient echo T1 weighted images, FSE and SSFSE T2 weighted images, were performed. Five MR pulse sequences were evaluated and compared on the point of detection and accurate distinction of tumor from surrounding normal tissue. Results : In EGC, diagnostic accuracy of US(77%) was superior than that of MRI(59%) but no statistically significant difference was noted between two imaging modalities(p=0.096). In AGC, both imaging modalities of MRI and US showed relatively high diagnostic accuracy as 97% and 84% respectively. Diagnostic accuracy of MRI was statistically better than that of US at the significant level(p<0.001). The best MR pulse sequence among five in each specimen was FSE T2WI(75.5%, 40/53) in both EGC and AGC. In AGC, FSE T2WI showed excellent imaging quality by showing very high ratio (93.5%, 29/31) of accurate delineation of tumor. Conclusion : MRI and US show relatively high diagnostic accuracy in the evaluation of tumor invasion depth of resected specimen in AGC. The most excellent pulse sequence of MRI for the evaluation of tumor invasion depth is FSE T2WI on the point of detection and accurate delineation of tumor in both EGC and AGC.

• Journal of the Korean Society of Radiology
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• v.84 no.6
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• pp.1220-1232
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• 2023

The prostate cancer diagnosis has traditionally been based on a systematic biopsy method in which tissue samples are randomly obtained from the prostate 10-12 sites. However, there are concerns as the method can fail to diagnose all prostate cancers or lead to over-detection of clinically insignificant cancers. MRI-guided prostate targeted biopsy has been proposed to address these shortcomings. This method involves identifying suspicious lesions using MRI and performing targeted biopsies under ultrasound or MRI guidance. We review the methods of MRI-based targeted biopsy and discuss recent guidelines and trends in prostate cancer diagnosis.