Influences of RF Transmit Field (B₁+) of Un-shielded Birdcage Coil at 7 Tesla

Phil Heo(허필),Sun Young Chae(채선영),Julius Juhyun Chung(정주현),Jung Hee Lee(이정희) 대한전기학회 2014 정보 및 제어 심포지엄 논문집 Vol.2014 No.10

Despite the effect of radio frequency (RF) shield on the birdcage coil leading to degradation of RF signal sensitivity in the imaging region, RF shield has to be considered for preventing the electro-magnetic field interaction between RF coil and MR scanner. Although the RF shield decreases overall transverse magnetic field (B₁) and RF transmit (B₁+) sensitivity compared to un-shielded volume coil, optimal RF shield configuration and positioning are critical issues in small-animal MR scanner. In this study, we demonstrated that improper positioning of un-shield RF birdcage (BC) coil leads to inhomogeneous B₁ + distribution at 7 Tesla. The flip angle (FA) map and the S-parameter measurement of custom-built 8-leg BC coil were performed when rotating its coil by 5° in the azimuthally angle. The results clearly show that an inhomogeneous FA map was measured in all cases due to the coil-subject interaction and improper positioning of BC coil. The mean valuesfor reference angles at 55°, +100° and + 220° of BC coil were 56.9, 54.5 and 58.3, respectively. Standard deviation (SD) value of for reference angles at 55°, +100° and + 220° of BC coil were measured to be 2.5, 2.7 and 2.3. The differentiation of mean and SD value of rotating angles indicate inhomogeneity and their sensitivity of B₁+ field. The proper positioning of BC coil in the MR scanner is crucial in shielding RF in the small-animal MR scanner.

Computational Analysis of Overlapping Birdcage Coil for Artificial Circular-Polarized Mode in Magnetic Resonance Imaging

Phil Heo,Han-Joong Kim,Soobum Kim,Donghyuk Kim,Kyoung-Nam Kim 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.5

In this computational analysis-based study, we proposed an overlapping birdcage (BC) coil with a particular interval distance along the z-axis in order to provide an artificial circular-polarized (CP) magnetic flux (B1) field based on a linear-polarized (LP) B1 field given by two single-channel BC coils. Overlapping BC coils were spaced at a specific overlapping distance in the main magnetic field (B0) direction by two identical BC coils through electromagnetic (EM) calculations and compared with B1 field and pointing vector distribution for the non-overlapping region at 7 Tesla of 297.2 MHz. These results clearly show that, unlike the general method for generating the CP mode using the quadrature driving method, overlapping LP modes that are individually used do not form a perfect CP mode, but instead a quasi-CP mode, in the form of an elliptical-polarized (EP) mode.

A case of Stevens-Johnson syndrome with parotitis

( Eun Phil Heo ),( Chi Yeon Kim ),( Tae Jin Yoon ),( Tae Heung Kim ) 대한피부과학회 2000 초록집 Vol.38 No.10

모누두 종양 2 예

허은필(Eun Phil Heo),오지원(Chee Won Oh) 대한피부과학회 2002 대한피부과학회지 Vol.40 No.6

Tumor of the follicular infundibulum(TFI) is rare benign adnexal tumor origination, from the infundibular portion of hair follicle. Majority of the lesions have been solitary and not recognized clinically before biopsy. TFI can be classified as follows according to the clinical presentation of the tumor (1) solitary tumor, (2) eruptive tumors, (3) TFT associated with other lesions of Cowden`s disease, (4) TFT arising in nevus sebaceus, and (5) TFT-like changes in various tumors. We present clinicopathologic features of 2 casts of TFT. One was solitary form and the other was associated with nevus sebacens.

Acitretin 치료로 호전된 비호지킨 림프종과 병발한 사마귀양 표피이형성증 1 예

허은필(Eun Phil Heo),엄성희(Sung Hee Um),오지원(Chee Won Oh) 대한피부과학회 2002 대한피부과학회지 Vol.40 No.8

Epidermodysplasia verruciformis(EV) is a rare disease characterized by a unique susceptibility to widespread infection with human papilloma virus. It induces flat papular skin lesions, characterized by large vacuolated cells in the upper epithelial layers. We report a patient of EV in association with non-Hodgkins lymphoma(NHL) improved with systemic acitretin treatment. A 69-year-old man presented multiple red flat-topped papules and plaques on his face and upper extremities for 12 years. Past various therapeutic modalities including DPCP sensitization were entirely ineffective. Several years ago, NHL of cervical lymph node was diagnosed. With the treatments with chemotherapy and radiotherapy, he is now in remission state. His skin biopsy specimen showed extensive vacuolation of upper malpighian layer. Bleomycin IL trial showed no response. Only 1 week after oral acitretin administration, his lesions began to exfoliate and became much flatter. Acitretin was effective but not suitable for maintenance therapy.

Aggressive Digital Papillary Adenoma 1 예

허은필(Eun Phil Heo),김지연(Chi Yeon Kim),오지원(Chee Won Oh) 대한피부과학회 2002 대한피부과학회지 Vol.40 No.7

Aggressive digital papillary adenoma is a rare neoplasm of eccrine sweat gland origin. We report a case of aggressive digital papillary adenoma with literature reviews. Pathogenesis of this tumor is unclear but, according to his past history, possible induction by defoliants could not be ruled out. Several immunohistochemical studies were done to confirm tumoral origin and to evaluate histological potential of malignancy.

피하 T - 세포 림프종 1 예

허은필(Eun Phil Heo),이원섭(Won Sup Lee),오지원(Chee Won Oh) 대한피부과학회 2002 대한피부과학회지 Vol.40 No.5

Subcutancous panniculitie. T-cell lymphoma(SPTCL) is a rare subtype of peripheral T-call lymphoma that clinically and histologically mimies benign panniculids. It represents subeutaneous nodules prdominantly on extremities and turck and himophagoeytic syndromc almost leading to death. Recent reports suggest that cytophagic histocyde pammieulitis(CHP) and SPTCL may span a clinieopathologic spectrum in which there is a natural disease progression from CHP to SPTCL. We reprot a 41-year-old Korean man who prescnted with recurrent tender crythematous subeutancous mokules on the buttock and extremites for 13 years history. There was no hipatosplenomegaly or lymphadenopathy. Laboratory data revealed mild ancmia, lcukopinia, and clevated alanine transterase. Epstein-Barr virus(EBV) scrlolgical values evidenced chronic active infection. His skin biopsy spceimen showed lobular pammiculitis with atypical lymphohistiocytic inflammatory infiloates. The inflammatory infilltrates expressed CK45RO, CD3, CD4, CD8, and CD68, But CD20 and CD56 were negative. In situ hybridizstion studies for the EBV ginome showed megative finding. This case presints SPTCL that had eluded diagnosis for a long time. It also suggests the improtance of comtinued follow-up with repeated biopsy, in case of long course of recurrent tender crythematous nokules and histological lobular lymphocytic pammiculitis.

옴 환자의 임상적 양상에 대한 연구

허은필 ( Eun Phil Heo ),민준홍 ( Joon Hong Min ),최종원 ( Chong Won Choi ),이가영 ( Ga Young Lee ),박수홍 ( Soo Hong Park ),김원석 ( Won Serk Kim ),김계정 ( Kea Jeung Kim ) 대한피부과학회 2011 대한피부과학회지 Vol.49 No.10

Background: Scabies is an ectoparasite caused by the mite Sarcoptesscabiei var. hominis, an obligate human parasite. Although the incidence of scabies is decreased nowadays, it is not rare and it is difficult to diagnose without experience. Objective: We conducted this study to evaluate clinical aspects of patients diagnosed with scabies in the last 4 years. Methods: We evaluated 56 patients who were diagnosed with scabies with a skin biopsy or with the mineral oil test. Medical records and telephone-interviews were used for more information. Results: There were 56 scabies patients, 28 males and 28 females. The mean age of the patients was 54 (male; 44.4/ female; 62.9) and 39.3% of patients were over 65 years. The most common affected site was the groin; common cutaneous lesions were pruritic papules and burrow. There was no seasonal variation in occurrence. The majority of suspected routes of infection were unknown but, nosocomial infection and communal living were also major causes. On average, 102 days were required to confirm scabies, which suggests the difficulty in early diagnosis of scabies. Conclusion: We suggest that dermatologists should consider scabies infection in patients who show pruritis that does not improve with ordinary treatment. (Korean J Dermatol 2011;49(10):882∼886)

변동형 대차 구동방식의 지압 침대 개발 및 유효성 평가

허성필(Sung-Phil Heo),박세진(Se-Jin Park),안도현(Do-Hyun Ahn) 한국산업정보학회 2020 한국산업정보학회논문지 Vol.25 No.6

지압은 신체의 특정 부위에 압력을 가하는 치료행위로 주로 한의학 분야에서 통증 경감에 활용되어 왔다. 하지만 시술자의 역량, 경험, 체력에 따라 치료 효과가 달라지는 경우가 많아 표준화된 지압이 필요하며 관련하여 기구가 출시되고 있으나 주로 롤링 마사지 방식이어서 에너지 집중도가 떨어지며 부상의 위험성이 있었다. 따라서 본 연구에서는 변동형 대차를 기반으로 수직 지압을 제공하는 장치를 구현하였다. 장치의 지압력 유효성 확인을 위해 하중 실험 및 체압 분포, 만족도를 실험한 결과 지압봉은 150kg까지 버티며, 체압비는 0 % < x ≤ 5% 구간에서 비교품의 체압 비율에 비해 낮게 측정되었으며, 또한 주관적 만족도는 평균 2.11점의 높은 점수를 받았다. 따라서 수직 지압이 적용된 장치가 기존 제품과 비교하면 체압 분산에 효과가 있었으며 만족도가 높다고 볼 수 있었다. 향후 연구에서는 수직 지압 사용 그룹과 전문 치료사의 지압 그룹을 구성하여 개발 기기가 사람에 비해 균일한 지압을 제공하는지 비교 평가할 필요가 있다. The acupressure is a treatment that applies pressure to certain parts of the body and has been mainly used for pain relief in the field of oriental medicine. However, the treatment effect is often different depending on the practitioner"s ability, experience, and physical strength, so standardized acupressure is needed. In this regard, the equipment is being released, but this is mainly a rolling massage method, which reduces energy concentration and poses a risk of injury. Therefore, in this study, a device that provides vertical acupressure based on variable bogie (wheel truck) was implemented. As a result of experimenting with load and body pressure distribution and desirability to validate the device"s bearing pressure, the acupressure rod held up to 150kg, the body pressure ratio was measured lower than the body pressure ratio of the comparison item in section 0%<x≤ 5%, and the subjective satisfaction was also scored high by an average of 2.11 points. Thus, the device with vertical acupressure was more effective in dispersion of body pressure than conventional products and was more satisfying. In future studies, it is necessary to organize a group of vertical acupressure use and a group of professional therapists to assess whether the development device provides a uniform acupressure compared to humans.

내용기반 질의법을 이용한 디지털 오디오 콘텐츠 검색 시스템

허성필(Sung-Phil Heo),임우영(Woo-Young Lim),한평희(Pyong-Hee Han) 한국정보통신설비학회 2004 한국정보통신설비학회 학술대회 Vol.2004 No.1