278 문일봉 곽종길 류영환 성호진 구은회 동경래 서론 1세시대라고불리는만큼현대의학은많이발전하였고건강에대한관심은높아지고있다. 건강이우리에게빼놓을수없는중요한요소가됨에따라건강검진및병변진단에쓰이는 CT 검사의사용빈도는증가하고있는추세이다 (Kim et al. 213). 그러나

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1 Journal of Radiation Industry 11 (4) : 277 ~ 281 (217) Technical Paper CT 팬텀영상에서관전압, 관전류변화에따른선량비교 문일봉 1 곽종길 2,3 류영환 4 성호진 5 구은회 6 동경래 1, * 1 광주보건대학교방사선과, 2 동신대학교보건의료학과, 3 KS 병원종합건진센터, 4 서울의료원영상의학과, 5 전남대학교병원영상의학과, 6 청주대학교방사선학과 Dose comparison according to the tube voltage, the tube current change in CT image Il-Bong Moon 1, Jong-Gil Kwak 2,3, Young-Hwan Ryu 4, Ho-Jin Sung 5, Eun-Hoe Goo 6 and Kyung-Rae Dong 1, * 1 Department of Radiological Technology, Gwangju Health University, 73, Bungmun-daero, 419 Beon-gil, Gwangsan-gu, Gwangju 62271, Republic of Korea 2 Department of Public Health and Medicine, Dongshin University Graduate School, 185, Geonjae-ro, Naju-si, Jeollanam-do 58245, Republic of Korea 3 Comprehensive medical examination center, KS Hospital, 22, Wangbeodeul-ro, Gwangsan-gu, Gwangju 62248, Republic of Korea 4 Department of Radiology, Seoul Medical Center, 156, Sinnae-ro, Jungnang-gu, Seoul 253, Republic of Korea 5 Department of Radiology, Chonnam National University Hospital, 42, Jebong-ro, Dong-gu, Gwangju 61469, Republic of Korea 6 Department of Radiological Science, Cheongju University, 298, Daeseong-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do 2853, Republic of Korea Abstract - Recently, as the phenomenon of radiation exposure gain high medical interest, an effort to reduce the dose of radioactivity resulted in the development of Auto Exposure Control Mode (AEC). In the study above, a test for efficiency and reliability of AEC, has been researched through the application of Rondo phantom and SIEMENS CT equipment used in C univeristy to ACE care KV and Care dose 4D. CTDIvol which Indicators of average radiation dose scan volume in units, The total dose values DLP, The Effective mas which value weighted according to each organ are measured to compare comparison by part when the tube current and tube voltage are manual (Fixed), when only the tube current are automatic (Care dose 4D), when the tube current and tube voltage are all automatical. The values of DLP has decreased in case of Neck, in care dose 4D 26.98%, Mixed 32.32%, in case of Chest, in care dose 4D 4.21%, Mixed 4.56% than Fixed. And the values has decreased equally in case of Abdomen, care dose 4D 45.23%, Mixed 45.23% than Fixed. When only the tube current are automatic, dose reduction is warranted, but when the tube current and tube voltage are all automatical, dose was slightly lower than what we expected. Key words : AEC, CTDIvol, DLP, Effective mas * Corresponding author: Kyung-Rae Dong, Tel , Fax , . krdong@hanmail.net 277

278 문일봉 곽종길 류영환 성호진 구은회 동경래 서론 1세시대라고불리는만큼현대의학은많이발전하였고건강에대한관심은높아지고있다. 건강이우리에게빼놓을수없는중요한요소가됨에따라건강검진및병변진단에쓰이는 CT 검사의사용빈도는증가하고있는추세이다 (Kim et al. 213).

2 278 문일봉 곽종길 류영환 성호진 구은회 동경래 서론 1세시대라고불리는만큼현대의학은많이발전하였고건강에대한관심은높아지고있다. 건강이우리에게빼놓을수없는중요한요소가됨에따라건강검진및병변진단에쓰이는 CT 검사의사용빈도는증가하고있는추세이다 (Kim et al. 213). 그러나이러한진단영역전산화단층촬영장치 (Computed tomography; CT) 의의료피폭에의해유도된발암이있을수있다는보고와몇년전원전사고로인한방사능유출에대해보고된내용들로인해일반인들의방사선에대한불안감과거부감이커지고의료피폭에대한신뢰성을의심하게되었다. 우리나라는방사선에대한두려움과공포만있을뿐이에대한경각심이적어과다한의료방사선피폭이이루어진다는지적이나오고있는상황이다. 최근 CT장비는시간단축과더넓은범위를검사할수있다는장점으로임상에서사용횟수가증가하고있지만, 검사를통한피폭선량이상당히높은수준이라병원에서환자에대한체계적인선량관리가민감한사항으로다뤄지고있다 (Moon et al. 217). 이러한동향에맞추어선량감소를위한노력으로환자의크기, 모양을고려해방사선량을자동적으로조절할수있는자동노출제어장치 (Auto Exposure Control mode; AEC) 가등장하였는데관전류를제어하는방법 (Automatic tube current modulation; ATCM) 과관전압을제어하는방법 (Automatic tube voltage selection; ATVS) 이있다. 수동노출방법은한번설정한관전류, 관전압으로변화없이일정한조건으로정해진범위를검사하는반면자동노출제어장치를사용하면인체의굵기등을센서로감지하여그에맞춘조건으로 X선을조사할수있다 (Bischoff et al. 29; Lee et al. 214; Ha et al. 215; Moon et al. 216). 이의일환으로저관전압방법이대두되고있으며, 일반적으로방사선선량은일정한관전류를유지한다면관전압의제곱에비례하므로적절한관전압의조절이환자의피폭선량에중요한인 자이다 (Abada et al. 26; Hausleiter 21). 하지만저관전압일수록피폭선량은줄어듦과동시에노이즈의증가라는치명적인약점을가지고있기때문에적절한관전압의사용이요구된다. 이에본연구는 ATVS, ATCM 사용을통해환자가받게되는선량값이수동설정으로촬영했을때선량에어떠한차이점이있는지알아보고자하였다. 재료및방법 1. 검사방법 CT 장비는광주에위치한일개종합병원에서사용되고있는 S사의 Somatom Definition Flash (Germany), 인체모형인 Rando phantom (Art-2x fluke biomedical, USA) 을 SIEMENS의 CARE kv, Care dose 4D를이용하여각부위별 (Neck, Chest, Abdomen) 관전압, 관전류자동조절기법의사용유무에따른선량변화를조사하였다 (Fig. 1). 2. 검사조건기본조사조건은 Neck의 care dose 4D 경우 mas 144, kvp 12, Fixed의경우 mas 2, kvp 12, Mixed의경우 mas 219, kvp 1이며 Pitch는 1., Slice는 5. mm, Rotation time은.5 sec FOV는 22 mm, Scan time은 4.15 sec로동일하게하였다. Chest의 care dose 4D 경우 mas 213 kvp 12, Fixed의경우 mas 22 kvp 12 Mixed의경우 mas 212, kvp 12이며 Pitch는 1., Slice는 3. mm, Rotation time은.5 sec FOV는 33 mm, Scan time은 5.35 sec로동일하게하였고 Abdomen의 care dose 4D 경우 mas 113, kvp 12, Fixed의경우 mas 21, kvp 12 Mixed의경우 mas 113, kvp 12이며 Pitch는.8, Slice는 3. mm, Rotation time은.5 sec FOV는 35 mm Scan time은 7.86 sec으로동일하게하였다 (Table 1). Fig. 1. Somatom Definition Flash and Rando phantom.

3 CT 에서관전압, 관전류변화에따른선량비교 279 Table 1. Comparison of CT Parameters by CT Scanner Care-4D a Fixed Mixed b Care-4D Fixed Mixed Care-4D Fixed Mixed mas kvp Pitch Slice (mm) Rotation time (sec) FOV (mm) Scan time (sec) a Care dose 4D (ma dose modulation), b Mixed : Care kv+care dose 4D 3. 측정방법관전류자동조절기법의사용유무에따라단위스캔부피내의평균방사선량을나타내는지표 CTDIvol 값과피사체에조사된모든영상에대한총선량값 DLP (Dose length product), 각각의장기들에피폭된방사선량에가중치가적용된값인유효선량 (Effective dose) 을측정하였다. CTDIvol은조직의평균조사선량을측정할수있도록하지만, DLP는일련의스캔에대한조사선량을측정할수있도록한다. 방사선에노출된체적의길이 ( 스캔길이 ) 와 CTDIvol을알수있다면, 아래와같은공식을이용해 DLP 를계산할수있다 (Eq. 1). DLP = CTDIvol * Scan length (1) Effective dose는 msv로나타내며방사선에의한확률적인위험요소를나타내고 DLP와컴퓨터시뮬레이션이나실제측정에서얻어진가중치 (Conversion Factor, f) 를곱함으로써예측할수있다. European Commission에보고된가중치값은아래와같다 (Table 2)(Heyer et al. 27). 결과각장비별로모두관전류자동조절기법을사용하였을때단위스캔부피내의평균방사선량을나타내는지표 CTDVol 값은 Care dose 4D, Fixed, Mixed 순으로 Neck 9.97, 13.66, 9.24가나왔고, Chest는 14.37, 15.1, 14.34, Abdomen은 7.68, 14.1, 7.68이나왔다. 피사체에조사된모든영상에대한총선량값 DLP (Dose length product) 는 Care dose 4D, Fixed, Mixed 순으로 Neck 287, 393, 266이나왔고 Chest는 546, 57, 544, Abdomen은 35, 639, 35 이나왔다. 유효선량 (Effective mas) 은 E=DLP * f의공식으로 Neck은 f값.54, Chest.17, Abdomen은.15를대입하여계산하였고그결과 Neck은 Care dose 4D, Fixed, Mixed 순으로각각 1.55, 2.12, 1.44가나왔고, Chest는각각 9.28, 9.69, 9.25, Abdomen은 5.25, 9.59, 5.25의값이나 Table 2. Effective Dose of European Commission Guideline (E= DLP * f) Region of body 왔다. 각조사방법으로선량감소를비교해봤을때 DLP (dose length product) 는 fixed를기준으로 Neck의경우 care dose 4D가 26.98%, Mixed가 32.32% 감소하였고, Chest의경우 care dose 4D가 4.21%, Mixed가 4.56% 감소하였고, Abdomen의경우 care dose 4D와 Mixed가 45.23% 로동일하게감소되었다 (Tables 3, 4)(Fig. 2). 고 Conversion factor. f (msv) Head.23 Neck.54 Chest.17 Abdomen.15 Pelvis.19 방사선검사및치료등방사선사용량이증가함에따라피폭선량의위험성이대두되고있다. 이에발맞추어환자의피폭선량을줄이는것에초점을맞춘소프트웨어적인측면의발전이이루어졌다. 그결과최근 CT에는모두관전류자동조절기법, 관전압자동조절기법시스템이개발되었으며, 이것은저피폭량으로보다정확한영상정보를얻는데있어기본요구조건이되었다. 관전류자동기법이선량이미치는영향을다룬 Moon의 CT 검사시관전류자동조절기법이선량에미치는영향연구에따르면 (Moon et al. 216) 관전류자동조절기법을사용했을때단위스캔부피내의평균방사선량을나타내는지표 CTDIVol 피사체에조사된모든영상의대한총선량값 DLP가 S사의경우 Neck 3.3%, Chest 25.5%, Abdomen 16% 감소, 유효선량은 S사의경우 Neck 47.5%, Chest 47.5, Abdomen 26.8% 로감소되었다고하였다. 또한이에따라자동노출제어장치를사용하면수동노출장치를사용했을때보다환자피폭을감소시키는것을알수있었으며영상품질에영향을끼칠거 찰

28 문일봉 곽종길 류영환 성호진 구은회 동경래 DLP 7 6 5 4 3 2 1 287 639 57 546 544 393 35 35 266 CTDIvol 16 14 12 1 8 6 4 2 9.97 14.37 15.1 14.34 13.66 14.1 9.24 7.68 7.68 12 1 9.28 9.69 9.25 9.

4 28 문일봉 곽종길 류영환 성호진 구은회 동경래 DLP CTDIvol Effective mas Care-4D Fixed Mixed Fig. 2. Comparison of DLP, CTDIvol and Effective mas by examination. Table 3. Comparison of Radiation by examination Care-4D a Fixed Mixed b Care-4D Fixed Mixed Care-4D Fixed Mixed CTDIvol DLP Effective mas a Care dose 4D (ma dose modulation), b Mixed : Care kv+care dose 4D Table 4. DLP reduction rate of Care-4D, Fixed and Mixed depending on the region DLP reduction ratio Fixed & Care dose Fixed & Mixed 라는예상과달리영상의잡음이증가하거나감소하는등의변화는보이지않았고영상품질은그대로유지한채선량만감소되었으므로 ACE 기법은영상품질의우수함을유지하면서불필요한피폭선량을감소하는데매우유용하며환자에게있어건강의질을높이고방사선피폭에대한불안감을줄여줄것이라고하였다 (Shin et al. 27; Seo 28; SIEMENS 29; Yoo et al. 21; Kim and Seoung 212; Lee et al. 214; Moon et al. 216). 본연구에서는 S사의 CT 검사시동일한조건하에 Rando phantom과최신 CT 장비를이용하여관전압과관전류의자동노출조절방법과수동 노출조절방법을사용했을때각부위별피폭선량과영상의차이를관찰하고임상에서의유용성을평가하였으며한번고정된값을바꿀수없어모든두께에같은량이조사되는수동조절기법에비해두께에따라자동으로다른선량을조절해주는자동조절기법에서의피폭선량이더낮을것이라는예상을하며실험을시작하였고연구결과 DLP의값은 Fixed를기준으로했을때 Neck의경우 care dose 4D 가 26.98%, Mixed가 32.32% 감소하였고, Chest의경우 care dose 4D가 4.21%, Mixed가 4.56% 감소하였고, Abdomen의경우 care dose 4D와 Mixed가 45.23% 로동일하게감소되었다. 그러나관전류자동조절기법 (Care dose 4D) 만사용했을때와관전류, 관전압을모두자동으로조절해주는자동조절기법을사용했을때의차이는예상보다미미하였고수동조절기구이용보다자동조절기구를이용시더낮은선량을나타내는것을확인할수있었다.

5 CT 에서관전압, 관전류변화에따른선량비교 281 결 본연구에서는수동조절장치와관전류자동장치그리고 관전압관전류자동장치에따라부위별로 CTDIvol, DLP, msv 를팬텀으로실험해알아보고자했다. 관전류자동조절 기구인 Care dose 4D 로 Neck 관찰시 CTDIVol 9.97, DLP 287, EmAs 1.55 의수치가나왔으며 fixed 로 Care dose 4D 로 Neck 관찰시 CTDIVol 13.66, DLP 393, EmAs 2.12 가 나왔다. Mixed (care kv+care dose 4D) 로 Neck 관찰시 CTDIVol 9.24, DLP 266, EmAs 1.44 의결과가나왔다. 관전 류자동조절만사용했을경우선행연구결과에서나왔듯이확실한차이로선량이감소하였다. 그러나관전류를자동으로조절하였을때현저한차이가난만큼관전압도자동으로조절하게되면더많은차이가날것이라고예상한것에비해관전류, 관전압을둘다자동으로조절했을때의선량감소율은비교적미미한차이를나타내었다. 사 This work was supported by the Nuclear Safety Research Program through the Korea Radiation Safety Foundation (KORSAFe) and the Nuclear Safety and Security Commission(NSSC), Republic of Korea(Grant No ). 론 사 참고문헌 Abada HT, Larchez C, Daoud B, Sigal-Cinqualbre A and Paul JF. 26. MDCT of the coronary arteries: feasibility of low-dose CT with ECG-pulsed tube current modulation to reduce radiation dose. Am. J. Roentgenol. 186(6): Bischoff B, Hein F, Meyer T, Hadamitzky M, Martinoff S, Schomig A and Hausleiter J. 29. Impact of a reduced tube voltage on CT angiography and radiation dose: results of the PROTECTION I study. JACC Cardiovasc. Imaging 2(8): Ha SM, Jung SH, Chang HJ, Park EA and Shim HJ Effects of Iterative Reconstruction Algorithm, Automatic Exposure Control on Image Quality, and Radiation Dose: Phantom Experiments with Coronary CT Angiography Protocols. Prog. Med. Phys. 26(1): Hausleiter J, Martinoff S, Hadamitzky M, Martuscelli E, Pschierer I, Feuchtner GM, Catalan-Sanz P, Czermak B, Meyer TS, Hein F, Bischoff B, Kuse M, Schömig A and Achenbach S. 21. Image quality and radiation exposure with a low tube voltage protocol for coronary CT angiography results of the PROTECTION II Trial. JACC Cardiovasc. Imaging 3(11): Heyer CM, Mohr PS, Lemburg SP, Peters SA and Nicolas V. 27. Image quality and radiation exposure at pulmonary CT angiography with 1- or 12-kVp protocol: prospective randomized study. Radiology 245(2): Huh JY, Bhum HN, Jung JB, Kim CG and Sun JB. 28. A Study on the Reduction of Radiation Dose When Examining Coronary Artery through CT Tube Current Modulation Employing 64VCT. J. Korea Soc. Comput. Tomogr. Technol. 1(1): Kim HJ, Moon IB, Han JB, Choi NG and Jang SJ Evaluation of Radiation Dose and Image Quality Between Manual and Automatic Exposure Control Mode According to Body Mass Index in Cardiac CT. J. Korea Cont. Assoc. 13(4): Kim YO and Seoung YH A Study on Various Automatic Exposure Control System in Multi-Detector Computed Tomography by Using Human Phantom. J. Korea Acad. Indus. Cooper. Soc. 13(4): Lee HJ, Kim HS, Lim KB, Kang SH and Lim JS The study on functions of Automatic and semi-automatic in Automatic Tube Voltage Selection software. J. Korea Soc. Comput. Tomogr. Technol. 16(2): Moon IB, Dong KR and Kim KC The Impact of the AEC Mode of Tube Current on the Dose at CT Scans. J. Radia. Ind. 1(2): Moon IB, Dong KR, Kim MH, Choi SH, Kweon DC and Goo EH Measurement of the Noise according to the Slice Thickness in MDCT. J. Radia. Ind. 11(3): Seo JY. 28. A study of appropriate expose condition in Chest CT for Care Dose 4D. J. Korea Soc. Comput. Tomogr. Technol. 1(1): Shin SB, Shin SK, Lee DK and Kim MC. 27. The choice optimal X-ray exposure factors in pediatric body CT. J. Korea Soc. Comput. Tomogr. Technol. 9(1): SIEMENS. 29. Dose Information - CT Essentials. Yoo HJ, Cheong SM and Suh DS. 21. Radiation Do se and Image Quality in Neck An giography : Comparison of Dual Source Computed T omography and Multi-detector Computed Tomography. J. Korea Soc. Comput. Tomogr. Technol. 12(2): Received: 5 November 217 Revised: 23 November 217 Revision accepted: 16 December 217

98 문일봉 신지윤 곽종길 장상현 류영환 동경래 서 론 연구대상및방법 컴퓨터단층촬영 (Computed tomography; CT) 검사는환자의진단과치료에도움을주는반면에방사선조사에따른위험을내포하고있다. 1990년대후반에등장한 MDCT (Multi-detector comp

98 문일봉 신지윤 곽종길 장상현 류영환 동경래 서 론 연구대상및방법 컴퓨터단층촬영 (Computed tomography; CT) 검사는환자의진단과치료에도움을주는반면에방사선조사에따른위험을내포하고있다. 1990년대후반에등장한 MDCT (Multi-detector comp Journal of Radiation Industry 12 (1) : 97 ~ 102 (2018) Technical Paper 복부팬텀영상에서장비별피폭선량및노이즈비교 문일봉 1 신지윤 1 곽종길 2,3 장상현 4 류영환 5 동경래 1, * 1 광주보건대학교방사선과, 2 동신대학교보건의료학과, 3 KS 병원종합건진센터, 4 구자성정형외과의원, 5 서울의료원영상의학과