• Progress in Medical Physics
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• v.23 no.3
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• pp.177-187
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• 2012

Magnetic resonance angiography (MRA) techniques are widely used in diagnosis of vascular disorders such as hemadostenosis and aneurism. Especially, phase contrast (PC) MRA technique, which is a typical non contrast-enhanced MRA technique, provides not only the anatomy of blood vessels but also flow velocity. In this study, we developed the 2- and 3-dimensional PC MRA pulse sequences for a low magnetic field MRI system. Vessel images were acquired using 2D and 3D PC MRA and the velocities of the blood flow were measured in the superior sagittal sinus, straight sinus and the confluence of the two. The 2D PC MRA provided the good quality of vascular images for large vessels but the poor quality for small ones. Although 3D PC MRA gave more improved visualization of small vessels than 2D PC MRA, the image quality was not enough to be used for diagnosis of the small vessels due to the low SNR and field homogeneity of the low field MRI system. The measured blood velocities were $25.46{\pm}0.73cm/sec$, $24.02{\pm}0.34cm/sec$ and $26.15{\pm}1.50cm/sec$ in the superior sagittal sinus, straight sinus and the confluence of the two, respectively, which showed good agreement with the previous experimental values. Thus, the developed PC MRA technique for low field MRI system is expected to provide the useful velocity information to diagnose the large brain vessels.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.2
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• pp.36-40
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• 1993

In order to improve complicated construction and complex control which are disadvantage of optimal PWM technique aimed at harmonic elimination method, this paper presented MRA(Model Reference Adaptive) PWM technique that gatmg signal of inverter is generated by comparing the reference signal with the induced feedback signal at the reference model of load. Design of controller is composed of microprocessor and analog circuit. MRA PWM technique used in the paper is able to compensate the degradation of voltage efficiency to be generated by the ratio of the output voltage to the DC supply voltage being low for using conventional sinusoidal PWM technique. When the trapezoidal signal is employed as the reference signal. the low order harmonics of line current can be reduced and the switching pattern is made by on-line computation using comparatively simple numerical analysis.

• Women's Health Nursing
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• v.1 no.1
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• pp.28-43
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• 1995

The relationship between perceived social support and adaptation to maternal role for first-time mothers was investigated in this descriptive correlational study. A nonprobable sample of 90 first-time mothers were selected, who had uncomplicated perinatal experiences and delivered healthy and term newborns as well. The data was collected during a home interview at 4-6weeks postpartum. The outcome of adaptations was defined as the level of sensitivity in parent-infant interactions and of the self confidence in infant care. The perception of social support in the primiparous was assessed by the NSSQ during the postpartum. The results obtained from this study are summarized as follows : 1. The mean score of the perceived total functional support was $116.6{\pm}37.5$ points (affective : 38.1 affirmative : 39.3, aid : 39.3), and the score of the total network support was $45.2{\pm}13.9$ points (size : 4.9, duration :19.8 frequency : 20.4). These scores tended to be slightly low. 2. The mean score of the self confidence on the infant care activity as the subjective aspect of the maternal role adaptation (MRA) was 56.5 points (86.9%), whereas that of the sensitivity of the mother-infant interaction of the MRA was 78.9 points (63.2%). 3. The subjective aspect of the MRA has showed a positive relation ship with the aid dimension of the functional support. And the objective aspect of the MRA also showed a positive relationship with the total functional support and the total network support. However the correlating degrees were slightly low. In conclusion, the primiparous mothers perceived that they had received a small amount of social support during the postpartum period, suggesting the need of various kinds of social support to promote the MRA for the primiparous.

• Journal of Oral Medicine and Pain
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• v.15 no.1
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• pp.61-68
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• 1991

The author studied the changes of subjective, objective symptoms and muscle activities with EM2 (myo-tronics Co., Seattle, USA) before and after MRA therapy. The 11 patients were treated with MRA and active range of motion, pain and mouth opening limitation were checked at each visit for 6-8 weeks. Electromyographic activities were measured in both anterior lobe of temporalis and middle fibers of masseter at the position in rest, clenching and mastication. The obtained results were as follows : 1. There were significant decrease in pain and mouth opening limitation and significant increase in active range of motion after MRA therapy. 2. The muscle activities tended to decrease in general, especially in the temporal and masseter muscles on clenching and in the masseter on mastication after MRA therapy. 3. There were no significant differences in muscle activities between affected and unaffected side, but there was significant differences in temporal muscle on clenching side after therapy. 4. There were no significant differences in active range of motion, pain and mouth opening limitation between acute and chronic groups. 5. There was more significant decrease in muscle activities of the affected side in acute group than those in chronic group.

• Journal of the Korean Society of Radiology
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• v.11 no.6
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• pp.493-500
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• 2017

In this study, data analysis has been conducted by INFINITT program to analyze the effect of signal to noise ratio(SNR) and contrast to noise ratio(CNR) of flow related enhancement(FRE) and computed tomography Angiography(CTA) on cerebrovascular diseases for qualitative evaluations. Based on the cerebrovascular image results achieved from 63 patients (January to April, 2017, at C University Hospital), we have selected 19 patients that performed both FRE-MRA and CTA. From the 19 patients, 2 were excluded due to artifacts from movements in the cerebrovascular image results. For the analysis conditions, we have set the 5 part (anterior cerebral artery, right and left Middle cerebral artery, right and left Posterior cerebral artery) as the interest area to evaluate the SNR and CNR, and the results were validated through Independence t Test. As a result, by averaging the SNR, and CNR values, the corresponding FRE-MRA achieved were: anterior cerebral artery ($1500.73{\pm}12.23/970.43{\pm}14.55$), right middle cerebral artery ($1470.16{\pm}11.46/919.44{\pm}13.29$), left middle cerebral artery ($1457.48{\pm}17.11/903.96{\pm}14.53$), right posterior cerebral artery ($1385.83{\pm}16.52/852.11{\pm}14.58$), left posterior cerebral artery ($1318.52{\pm}13.49/756.21{\pm}10.88$). by averaging the SNR, and CNR values, the corresponding CTA achieved were: anterior cerebral artery ($159.95{\pm}12.23/123.36{\pm}11.78$), right middle cerebral artery ($236.66{\pm}17.52/202.37{\pm}15.20$), left middle cerebral artery ($224.85{\pm}13.45/193.14{\pm}11.88$), right posterior cerebral artery ($183.65{\pm}13.47/151.44{\pm}11.48$), left posterior cerebral artery ($177.7{\pm}16.72/144.71{\pm}11.43$) (p < 0.05). In conclusion, MRA had high SNR and CNR value regardless of the cerebral infarction or cerebral hemorrhage observed in the 5 part of the brain. Although FRE-MRA consumed longer time, it proved to have less side effect of contrast media when compared to the CTA.

• Journal of Navigation and Port Research
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• v.26 no.2
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• pp.209-213
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• 2002

MRA(Multi-resolution analysis) algorithm by Wavelet and morphology with $3{\times}3$ SQ(square) SE(structure element) is efficient to remove ship's radar clutter progressively and enhances detecting performance. Smoothing efficiency of RMM (Recursive mathematical Morphology) is better than that of Morphology. So, to get a better result than that of old algorithms, this paper proposes a new MRA algorithm which uses Wavelet and Recursive mathematical Morphology with $3{\times}3$ RHR(rhombus) SE. Simulation result of the proposed algorithm shows that PSNR is 0.65~1.50db better than that of old method.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.98-98
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• 2003

We will present various MR findings of hyperacute ischemic stroke with our own experiences in the management of the patients according to the findings. 대상 및 방법： A total of 441 patients were underwent 'acute stroke MR' imaging protocol between Mar. 2001 and Jun. 2003. The protocol included initial T2-weighted image (WI), diffusion WI (DWI, b=2000), time-of-flight (TOF) MR angiography (MRA), and pefusion WI(PWI), and follow-up T2WI, DWI, TOF MRA, and neck vessel contrast-enhanced MRA obtained three to five days after the insult. Among them, we retrospectively reviewed the MR findings and clinical courses of 193 patients with anterior circulation territorial infarction. Those ICA and MCA lesions were divided into six and five groups respectively according to the level and mechanism of the occlusion. PWI findings can be another factor in the management planning.

• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.115-125
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• 2009

Purpose: The purpose of the study is to evaluate the usefulness of CT arthrography (CTA) by conducting a comparative study of CTA and MR arthrography (MRA) with the arthroscopic findings in the same patients. Materials and methods: Forty nine patients who suffered from shoulder disease underwent MRA and CTA concurrently. The sensitivity and specificity of CTA was evaluated, as compared to MRA, in the case of four types of shoulder pathological lesions. The accuracy of CTA was evaluated by analyzing the arthroscopic findings of thirty four patients. Results: Compared to MRA, CTA showed a sensitivity of 90% and a specificity of 100% for diagnosing supraspinatus tendon (SST) full thickness tear, and CTA showed a sensitivity of 100% and a specificity of 97.5% for making the diagnosis of superior labrum anterior to posterior (SLAP) lesion. For diagnosing partial articular side supraspinatus avulsion (PASTA) lesion, some studies have shown the usefulness of CTA with a sensitivity of 71.4% and a specificity of 97.7%. However, for diagnosing SST bursal side partial tear, the sensitivity of CTA was as low as 10%. CTA has been shown to be relatively accurate when the diagnoses were verified with the arthroscopic findings; diagnosing SST full thickness tear and SLAP lesion with CTA has shown an accuracy of 100% and87.5% respectively, and CTA showed 71.4% diagnostic accuracy for PASTA lesion. Conclusion: CTA was a useful tool and it was equivalent to MRA for the assessment of SST full thickness tear, SLAP lesion and PASTA lesion, but not bursal side partial tear. Thus, it may be used preferably to diagnose shoulder pathology and for follow up as an inexpensive tool after operation.

• Steel and Composite Structures
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• v.18 no.3
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• pp.757-773
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• 2015

This work attempts to implement multiple regression analysis (MRA) for modeling and predicting the shear buckling strength of a steel beam with corrugated web. It was recognized from theoretical and experimental results that the shear buckling strength of a steel beam with corrugated web is complicated and affected by several parameters. A model that predicts the shear strength of a steel beam with corrugated web with reasonable accuracy was sought. To that end, a total of 93 experimental data points were collected from different sources. Then mathematical models for the key response parameter (shear buckling strength of a steel beam with corrugated web) were established via MRA in terms of different input geometric, loading and materials parameters. Results indicate that, with a minimal processing of data, MRA could accurately predict the shear buckling strength of a steel beam with corrugated web within a 95% confidence interval, having an $R^2$ value of 0.93 and passing the F- and t-tests.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.275-280
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• 2003

The method of simultaneous data acquisition of arteries and veins(SAAV) was suggested to obtain MR angiography of arteries and veins at 0.3T low filed MRI system (Magfinder, AlLab. Korea). Two separated artery- and vein-images were put together using AVCM(Artery-Vein Color Mapping) algorithm and presented in the same image. In this study, artery- and vein-separated angiograms of volunteer's neck were obtained. Two dimensioal blood-enhanced images wre sequentially obtained using SAAV pulse sequence based on time-of-flight(TOF) method with flow compensation. Imaging parameters were TR/TE=70/12msec. FOV=230mm, slice thickness = 3mm, flip angle=90$^{\circ}$, matrix size=256${\times}$256${\times}$64mm. TSat TH/SPA=15/20mm, Ts_v=10msec and Ts_a=40ms. 3D MRA images were reconstructed using the maximum intensity projection(MIP) and the artery-vein color mapping(AVCM) algorithm. This study showed good possibility of clinical applications of MRA in 0.3T which provides valuable diagnostic information of clinical vascular diseases.