• Journal of the Korean Society of Radiology
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• v.11 no.5
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• pp.361-370
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• 2017

In the Brain MRI, RF Pulse is irradiated on the human body in order to acquire an image. At this time, a considerable part of the irradiated RF Pulse energy is absorbed as it is in our body. This will raise the temperature of the human body, but depending on the extent of exposure, it will affect the human body. The change of the SAR and the temperature of the head according to the change of the magnetic field strength is examined. And to investigate the difference in results depending on the use of dental implant. In the human head model, 64 MHz RF Pulse frequency generated from 1.5 T, 128 MHz RF Pulse frequency generated from 3.0 T, and 298 MHz RF Pulse frequency generated from 7.0 T send a frequency and experiment was performed using dental implant using the XFDTD program, we measured the SAR and body temperature changes around the head. The SAR value showed up to about 5800 times the difference at the RF Pulse frequency of 256 MHz, when with dental implant than without dental implant and as the frequency increased, the use of the dental implant increased difference in the SAR value. The change of the temperature of the head showed a temperature rise nearly 2 to 4 times when with dental implant than without dental implant. As the RF Pulse frequency increase, the SAR value increase, but the change of the temperature of the head decrease. Because of as the frequency increase, wavelength is smaller and the more the amount absorbed by the surface of the human. Physiological and biochemical studies of the human body ar necessary through studies of the presence of dental implant and the cause of reaction caused by change in the RF Pulse frequency.

• Investigative Magnetic Resonance Imaging
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• v.7 no.2
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• pp.124-131
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• 2003

Purpose : To reveal clinical usefulness of functional MRI (fMRI) using sensorymotor and language stimuli for demonstrating anatomic relationship between sensorimotor or language cortices and lesions in the planning of brain tumor surgery. Materials and Methods : This study included 12 right-handed patients with brain tumors in or around sensorimotor or language cortices. Eleven patients were evaluated with primary motor and sensory stimuli. Of these patients, six patients were also evaluated with language stimuli. One patient was evaluated with language stimuli only. For fMR imaging, a 1.5T scanner was used and the EPI BOLD technique was employed. For postprocessing image, the SPM99 program and a program made by our department was utilized. We evaluated whether sensorimotor and language stimuli activate sensorimotor and language cortices. And also, clinical efficacy of revealing anatomic relationship between cerebral cortices and lesions for planning neurosurgical operation were evaluated. Finally, we compared post-operative neurologic function with pre-operative neurologic function in same patients. Results : The fMRI examination was successful in identifying the functional cortices and depicting anatomic relationship between functional cortices and lesions in all patients. In nine patients of 11 patients with identified sensorimotor cortices, postoperative grade of manual motor test was not changed, compared with preoperative grade. Whereas postoperative improved than preoperative grade in one patient of remaining two patients, postoperative aggravated than preoperative grade in the other. This result was due to atherosclerotic lacunar infarction, regardless of tumor resection. Postoperative deficit of language function was not found in seven patients with identified language cortices. Conclusion : fMRI could be a helpful method for determining the best approach to neurosurgical treatment in patients with brain tumors in or around sensorimotor or language cortices.

• Investigative Magnetic Resonance Imaging
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• v.7 no.2
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• pp.100-107
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• 2003

Purpose : To assess the usefulness of cardiac MR imaging (MRI) in the diagnosis of acute myocardial infarction and in the assessment of myocardial viability in comparision with T1-201 SPECT. Materials and Methods : We retrospectively studied 17 patients who complained of chest pain and dyspnea with cardiac MRI . The patients were evaluated for the presence or absence of high signal intensity on T2-weighted image (T2wI), abnormal wall motion on 2D-FIESTA, perfusion defect on Gd-DTPA enhanced T1WI, and delayed myocardial enhancement on 15-minutes delay Gd-DTPA enhanced T1WI. The results were correlated with the images on T1-201 SPECT, taken at rest and stress, through which reversibility of perfusion defect was assessed. Results : Both cardiac MRI and T1-201 SPECT proved to be useful methods for diagnosing acute myocardial infarction. In order of decreasing correspondence, T2WI, T1-201 SPECT, delayed enhancement study, and wall motion images all showed significant statistical correlation with the clinical diagnosis of myocardial infarction. Perfusion MRI, on the other hand, showed no significant statistical difference was found between T1-201 SPECT and cardiac MRI. The results on T2WI showed high accordance with those on Tl-201 SPECT, while delayed myocardial enhancement and wall motion studies showed no agreement with Tl-201 SPECT. Conclusion : Cardiac MRI is useful method for diagnosis of acute myocardiac infarction. With respect to the assessment of myocardial viability, the results obtained on cardiac MRI showed high agreement with those on Tl-201 SPECT. However, further study is necessary at this point for standardization and establishment of the methods for assessing myocardial viability on cardiac MRI.

• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.173-179
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• 2009

Purpose: On the hypothesis that the acromion morphology is changed according to the its site, we identified the morphology of the acromion on the oblique slices of MRI and we investigated the association of the acromial shape with the clinical stages of rotator cuff disorder on the magnetic resonance (MR) images. In addition, we compared the acromion morphology on MRI and simple X-rays. Material and Methods: The MR images of seventy one patients with rotator cuff disorder and who underwent arthroscopic surgery were compared with that of a control group of sixteen patients who didn't have rotator cuff disorder on MRI. On three subsequent oblique sagittal slices from the lateral edge of the acromion (S1, S2 and S3), each acromion morphology on the MRI slices was classified according to Epstein et al: flat, curved or hooked. We investigated the changing parttern of the acromion shape and we compared the acromion shape on MRI and that on simple X-rays. We classified the rotator cuff tear by the severity: bursitis, partial thickness tear or full thickness tear. We investigated which acromial type on the MRI oblique slice was associated with the severity of rotator cuff disease. Results: Changes of the acromial shape occurred in 54 patients (76.1%). The most frequent pattern was that the types are same on S1 and S2 and different on S3 (22 cases, 31.0%). The acromial type on S1 and S2 was significantly associated with the severity of rotator cuff disorder (p=0.001 and 0.022), respectively. There was no reliability of the acromial shape on MRI and roentgenography (p>0.05) Conclusion: The type of acromion changed from lateral to medial. Among the three positions, the shape of the acromion on S1 and S2 had meaningful correlation with the clinical stage of rotator cuff disorder. There was no statistical correlation of the acromial shape between MRI and simple X-ray.

• Investigative Magnetic Resonance Imaging
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• v.17 no.2
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• pp.83-90
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• 2013

Purpose : To report our clinical experience with cardiac 3.0 T MRI in patients compared with 1.5 T using individually optimized imaging protocols. Materials and Methods: We retrospectively reviewed 30 consecutive patients and 20 consecutive patients who underwent 1.5 T and 3 T cardiac MRI within 10 months. A comparison study was performed by measuring the signal-to-noise ratio (SNR), the contrast-to-noise ratio (CNR) and the image quality (by grading each sequence on a 5-point scale, regarding the presence of artifacts). Results: In morphologic and viability studies, the use of 3.0 T provided increase of the baseline SNRs and CNRs, respectively (T1: SNR 29%, p < 0.001, CNR 37%, p < 0.001; T2-SPAIR: SNR 13%, p = 0.068, CNR 18%, p = 0.059; viability imaging: SNR 45%, p = 0.017, CNR 37%, p = 0.135) without significant impairment of the image quality (T1: $3.8{\pm}0.9$ vs. $3.9{\pm}0.7$, p = 0.438; T2-SPAIR: $3.8{\pm}0.9$ vs. $3.9{\pm}0.5$, p = 0.744; viability imaging: $4.5{\pm}0.8$ vs. $4.7{\pm}0.6$, p = 0.254). Although the image qualities of 3.0 T functional cine images were slightly lower than those of 1.5 T images ($3.6{\pm}0.7$ vs. $4.2{\pm}0.6$, p < 0.001), the mean SNR and CNR at 3.0 T were significantly improved (SNR 143% increase, CNR 108% increase, p < 0.001). With our imaging protocol for 3.0 T perfusion imaging, there was an insignificant decrease in the SNR (11% decrease, p = 0.172) and CNR (7% decrease, p = 0.638). However, the overall image quality was significantly improved ($4.6{\pm}0.5$ vs. $4.0{\pm}0.8$, p = 0.006). Conclusion: With our experience, 3.0 T MRI was shown to be feasible for the routine assessment of cardiac imaging.

• Progress in Medical Physics
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• v.15 no.2
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• pp.112-119
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• 2004

We tried to build human models based on medical images of live Korean, instead of using standard data of human body structures. Characteristics of mechanical structures of human bodies were obtained from medical images such as CT and MR images. For each constitutional part of mechanical structures CT images were analyzed in terms of gray levels and MR images were analyzed in terms of pulse sequence. Characteristic features of various mechanical structures were extracted from the analyses. Based on the characteristics of each structuring element we peformed image segmentation on CT and MR images. We delineated bones, muscles, ligaments and tendons from CT and MR images using image segmentation or manual drawing. For the image segmentation we compared the edge detection method, region growing method and intensity threshold method and applied an optimal compound of these methods for the best segmentation results. Segmented mechanical structures of the head/neck part were three dimensionally reconstructed.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.1
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• pp.81-87
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• 2012

The current defacing method for keeping an anonymity of brain images damages the integrity of a precise brain analysis due to over removal, although it maintains the patients' privacy. A novel method has been developed to create an anonymous face model while keeping the voxel values of an image exactly the same as that of the original one. The method contains two steps: construction of a mockup brain template from ten normalized brain images and a substitution of the mockup brain to the brain image. A level set segmentation algorithm is applied to segment a scalp-skull apart from the whole brain volume. The segmented mockup brain is coregistered and normalized to the subject brain image to create an anonymous face model. The validity of this modification is tested through comparing the intensity of voxels inside a brain area from the mockup brain with the original brain image. The result shows that the intensity of voxels inside from the mockup brain is same as ones from an original brain image, while its anonymity is guaranteed.

• Journal of radiological science and technology
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• v.42 no.1
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• pp.39-46
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• 2019

This study conducted a comparative analysis of differences between cartesian trajectory in a linear rectangular coordinate system and MultiVane trajectory in a nonlinear rectangular coordinate system axial T1 and axial T2 images using an American College of Radiology(ACR) phantom. The phantom was placed at the center of the head coil and the top-to-bottom and left-to-right levels were adjusted by using a level. The experiment was performed according to the Phantom Test Guidance provided by the ACR, and sagittal localizer images were obtained. As shown in Figure 2, slices # 1 and # 11 were scanned after placing them at the center of a $45^{\circ}$ wedge shape, and a total of 11 slices were obtained. According to the evaluation results, the image intensity uniformity(IIU) was 93.34% for the cartesian trajectory, and 93.19% for the MultiVane trajectory, both of which fall under the normal range in the axial T1 image. The IIU for the cartesian trajectory was 0.15% higher than that for the MultiVane trajectory. In axial T2, the IIU was 96.44% for the cartesian trajectory, and 95.97% for the MultiVane trajectory, which fall under the normal range. The IIU for the cartesian trajectory was by 0.47% higher than that for the MultiVane trajectory. As a result, the cartesian technique was superior to the MultiVane technique in terms of the high-contrast spatial resolution, image intensity uniformity, and low-contrast object detectability.

• Investigative Magnetic Resonance Imaging
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• v.16 no.1
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• pp.67-75
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• 2012

Purpose : We studied enhanced method to view the vessels in the brain using Magnetic Resonance Angiography (MRA). Noticing that Maximum Intensity Projection (MIP) image is often used to evaluate the arteries of the neck and brain, we propose a new method for view brain vessels to stereo image in 3D space with more superior and more correct compared with conventional method. Materials and Methods: We use 3T Siemens Tim Trio MRI scanner with 4 channel head coil and get a 3D MRA brain data by fixing volunteers head and radiating Phase Contrast pulse sequence. MRA brain data is 3D rotated according to the view angle of each eyes. Optimal view angle (projection angle) is determined by the distance between eye and center of the data. Newly acquired MRA data are projected along with the projection line and display only the highest values. Each left and right view MIP image is integrated through anaglyph imaging method and optimal stereoscopic MIP image is acquired. Results: Result image shows that proposed method let enable to view MIP image at any direction of MRA data that is impossible to the conventional method. Moreover, considering disparity and distance from viewer to center of MRA data at spherical coordinates, we can get more realistic stereo image. In conclusion, we can get optimal stereoscopic images according to the position that viewers want to see and distance between viewer and MRA data. Conclusion: Proposed method overcome problems of conventional method that shows only specific projected image (z-axis projection) and give optimal depth information by converting mono MIP image to stereoscopic image considering viewers position. And can display any view of MRA data at spherical coordinates. If the optimization algorithm and parallel processing is applied, it may give useful medical information for diagnosis and treatment planning in real-time.

• Korean Journal of Cognitive Science
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• v.21 no.2
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• pp.359-386
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• 2010

In order to evaluate the domain-specific model and process-specific model of spatial and nonspatial working memory (WM), this study manipulated the memory load of the delayed response task and examined how the neural correlates of memory load effect was influenced by the stimulus domain (face and location) at the maintenance stage of WM using an event-related fMRI experiment. One or three face stimuli were presented as target stimuli and participants were asked to maintain the face itself (face WM) or the location of face stimuli (spatial WM). The results of recognition judgment accuracy showed no difference between face WM and spatial WM, and showed equivalent memory load effects of both WM. As a result of brian image analysis, memory load effect at maintenance stage showed that inferior, middle, and superior PFC were recruited by both face WM and spatial WM, and showed that VLPFC was the commonly activated area by both WM, supporting functional specialization of PFC by process components of WM. This study provides evidence for process-specific model in which maintenance of WM is associated with VLPFC.