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치과 방사선 검사에서 유효선량 평가

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치과 방사선 검사에서 유효선량 평가


― Evaluation of Effective Dose in Dental Radiography ―


고려대학교 보건과학대학 방사선학과 ․ 송호대학 방사선과1) ․ 연세대학교 치과대학병원2)


한수철 ․ 이보람 ․ 신귀순1) ․ 최종학 ․ 박혁2) ․ 박창서2) ․ 장계용2) ․ 김보람2) ․ 김유현



― 국문초록―


과학 기술의 발달로 인해 의료 방사선 장비 또한 첨단화 되고 있으며 정확한 진단과 치료를 할 수 있게 되어 의료의 질적 향상은 물론 양적인 면에서도 그 사용이 날로 증가하고 있는 추세이다. 특히 환자피폭선량에 대부분을 차지하는 CT(Computed Tomography) 촬영의 건수는 크게 증가하고 있다.


치과 방사선 검사의 경우 정확한 병변 진단을 위한 CT 및 CBCT(Cone Beam Computed Tomography) 의 도입으로 과거에 비해 환자는 많은 선량을 받게 되었다. 본 연구에서는 인체 팬텀과 TLD-100H를이용하여 치과 방사선 검사별 조직의 흡수선량을 측정하고 ICRP 60, 103에 따라 유효선량을 계산하였다. ICRP 60, 103에 따른 유효선량 값은 파노라마 검사의 경우 5.1μSv, 29.5μSv, 세팔로 검사의 경우11.2μSv, 14.4μSv,이며 CBCT는 상악골의 경우 53.7μSv, 209.6μSv, 하악골은 129μSv, 391.5μSv 그리고 CT에서는 상악골의 경우 93.3μSv, 139.5μSv이며 하악골은 282.7μSv, 489.7μSv로 평가 되었다. CBCT 검사의 경우 유효선량


은 CT 검사에 비해서는 적지만 파노라마 검사 및 세팔로 검사에 비해서는 높게 평가되었다.


중심단어 : 치과 방사선 촬영, 유효선량, 방사선 방어, ICRP 103, 선량 감소


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교신저자: 김유현, (136-703) 서울시 성북구 정릉3동

고려대학교 보건과학대학

TEL: 02-940-2823, FAX: 02-917-9074

E-mail: kyhyun@korea.ac.kr

방사선기술과학 Vol. 34, No. 1, 2011

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Ⅰ. 서 론

과학 기술의 발달로 인해 의료 방사선 장비 또한 첨단화 되고 있으며 정확한 진단과 치료를 할 수 있게 되어 의료의 질적 향상은 물론 양적인 면에서도 그 사용이 날로 증가하고 있는 추세이다. 특히 환자 피폭선량에대부분을 차지하는 CT(Computed Tomography) 장비수도 계속적으로 증가하고 있다. 건강 보험 심사 평가원에 따르면 CT장비의 증가 현황은 2007년에는 2030대, 2008년 2299대로 전년 대비 13.3% 증가하였으며2009년도에도 2008년도에 비해 5.9% 증가하였다1).

UCSF(캘리포니아대학 샌프라시스코) 방사선학과 레베카 스미스 빈드먼 박사는 “CT는 병변 진단에 있어 상당한 이득을 얻을 수 있는 반면 환자는 일반 X선 진단에 비해 상당히 많은 방사선에 노출되기에 향후 암 위험이우려된다고”고 말하였다2). 진단 방사선 검사 영역에서의 환자선량에 대한 관심은 계속적으로 증가하고 있다. UNSCEAR 2000 Report에 따르면, 치과방사선 검사는 다른 진단 방사선 검사에 비해 낮은 촬영 조건을 사용하고있지만 사용 빈도가 많은 검사 중 하나이며 ALARA(as low as reasonably achievable)원칙에 따라 최적화된 검사를 해야 한다고 하고 있다3).

치과 방사선 검사에 있어 방사선 방어에 관한 연구를 위해 국내외에서는 진단참조준위를 정하여 선량 저감화의 노력을 하고 있다. 최적화된 진단참조준위 값을 권고함으로써 그 이상의 선량을 가지는 병원의 경우촬영기술 등을 조절함으로서 선량 감소의 노력을 할 수 있다. 진단참조준위 값을 정하기 위한 값으로써 ESD(Entrance Surface Dose), ESAK(Entrance Surface air kerma), DAP(Dose Area Product), DWP(Dose Width Product) 등을 사용하고 있으나 이 값들로는 방사선 위해에 대한 평가를 하기가 어렵다. 치과 방사선 검사로 인한 피폭에 의해 생길 수 있는 장해에 대한 평가를 위해서는 유효선량을 구하는 것이 타당하다.

치과 방사선 검사에 있어 세팔로 검사, 파노라마 검사, CBCT(Cone Beam Computed Tomography), CT를 ICRP(International Committee for Radioactivity Prevention) 60, 103 기준으로 유효선량을 계산하였다. ICRP 60과ICRP 103의 가장 큰 차이는 치과 방사선 검사에 있어 많은 부분이 포함되고 있는 침샘의 경우 조직가중계수가 ICRP 60에서는 제외 되었던 것이 ICRP 103에서는

0.015)로 포함됨으로서 과소평가 되었던 침샘에 대하여 평가 할 수 있게 되었다는 것이다.

따라서 본 연구에서는 치과 방사선검사 시 각 조직의 흡수선량을 측정하고 유효선량 값을 계산하여 비교 하였으며, 특히 최근 증가하고 있는 CBCT와 다른 치과 방사선 검사와의 유효선량을 비교함으로써 CBCT 검사의유용성에 대해 분석 하였다.

Ⅱ. 실험재료 및 방법

  1. 실험재료


치과 방사선 검사의 선량측정을 위해서 본 실험에 사용된 인체 팬텀은 인체의 조직과 유사한 조직 분포를 가지며 2.5 cm 두께의 10개의 절편(Fig. 1, levels 0-9)으로 구성된 Male ART Phantom(Fluke Biomedical Co.,USA))과 1/8″×1/8″×0.035″의 열 형광선량계 TLD-100H(HARSHAW Chemical Co., USA), TLD Reader 2800M(VICTOREEN Co. USA)를 이용 하였다. 세팔로 검사와 파노라마 검사 장비로는 CRANX3+CEPH (Soredex Co. Finland), CBCT 장비는 Ray Scan Symphony(

Ray Co, Korea), CT 장비는 HiSpeed ADVENTAGE(GE medical USA) 사용하였다.

  1. 실험방법


1) 유효선량 계산

본 실험에 사용하고자 하는 TLD의 교정을 위해 동일선량의 방사선으로 TLD에 조사 후 TLD reader기를 통해 각 TLD 소자의 전하량(nC)을 측정하여 교정정수(RCF, Reader Calibration factor)를 결정 하였다. 이때 선량측정은5 cc 전리함(Capintec. USA)과 미소전류계(Capintec.

MODEL 192. USA)를 이용하여 측정하였고 전 실험 과정을 통해 각 소자의 동일성을 유지하기 위해 각 소자의 ECC(Element Correction Coefficient) 구하여 보정하였다. 각 검사 별 조사 시 방사선에 노출시키기 전에TLD소자에 남아 있는 에너지를 방출시키기 위하여 oven을 이용하여 섭씨 240°에서 10분간 가열하고 난 후 선량 측정에 사용 하였다. 또한 선량측정 후 TLD reader기로 전하량 값을 측정하기 전에 TLD 내에서 생길 수 있는noise 제거를 위해 섭씨 135°에서 10초간 예열 하였다.

각 검사 별 반복 조사 후 TLD reader기로 전하량 값을 얻어 식(1)을 이용하여 전하량(nC)을 조사선량(mR)으로 변환하였다. 측정값의 평균값(mR)을 흡수선량(μGy)값으로, 계산된 흡수선량 값은 공기 중에서 측정된 값이므로실제 조직에서의 흡수선량 값으로 바꾸어 주어야 한다.

그래서 식(2)와 같이 미국 표준연구소(National institute of science technology: NIST)에서 제시한 X선 에너지와 물질 종류에 따른 질량에너지 흡수계수값을 이용하여 조직에서의 흡수선량 값을 구하였다.

mR) =ECC × chargenc)/RCF························· (1)

․ X: exposure dose in air

․ RCF: reader calibration factor

․ ECC: element correction coefficient

tissue cGy) × 0.876 ×(μ en/ρ) tissue/(μ en/ρ) air············ (2)

․ Dtissue: Absorbed dose in tissue (cGy)

․ X: Exposure dose in air (mR)

․ (μ en/ρ) tissue : Mass absorption coefficient of tissue

․ (μ en/ρ) air : Mass absorption coefficient of air

치과 방사선 검사에서 유효선량 평가

이와 같이 계산된 흡수선량의 값에 방사선가중치를 곱하여 조직의 등가선량을 구하고 구해진 등가선량을 ICRP 60, 103에 의해 제시된 조직가중치를 적용한 총합으로 각 치과 검사 별 유효 선량 값을 식 (3)에 의해 계산하였다.

Effective doseE) =Σ× ························ (3)

․ WT: 조직하중계수 (Table 1)

․ HT: 조직등가선량

Table 1. Weighting factors for tissue in ICRP 60, 1034,5)

각 검사 별 Phantom에서 TLD 소자의 위치는 thyroid 2개, esophagus 1개, salivary gland 5개, brain 2개, bone marrow 8개, skin 5개, eyes 2개로 총 25개를 각 phantom의 level에 위치 시켰다6)(Table 2).

Fig. 1. Head & Neck phantom with 3×3 cm hole grid spacing and 5 mm hole diameter (levels 0-9)

2) 치과 방사선 검사 방법 및 검사 조건

아래 Table 3과 같이 실제 임상병원에서 검사되고 있는 성인 표준 남성 기준으로 각 검사방법에 따라 팬텀을 위치시켜 측정하였다. 아래 Fig. 2과 같이 팬텀을 환자와 동일한 자세로 위치 시켰다.

방사선기술과학 Vol. 34, No. 1, 2011

Fig. 2. Phantom position of dental radiography

Table 3. Exposure factors and method of dental radiography

이때 TLD의 측정 가능한 선량을 조사하기 위해서 검사법에 따라 세팔로 검사의 경우 mAs가 다른 검사에 비해 적은 값이기에 여러 번의 실험을 거쳐 20회 정도일 때 측정 가능한 선량 값을 얻을 수가 있었으면 다른검사의 경우 대부분이 100 mAs 이상으로 5회의 반복 촬영 후에 측정 가능한 선량 값을 얻을 수 가 있었다. 반복 검사 후 얻은 값을 반복 검사 횟수로 나누어 평균값을 구해 비교하였으며, CBCT 검사와 CT 검사의경우, 검사 부위를 상악골과 하악골 나누어 선량 값을 계산하였다.

Ⅲ. 결 과

각 검사 별 조직에서의 등가선량을 구하고 이를 바탕으로 ICRP 60, 103에 따른 조직가중계수를 고려하여 유효선량을 구하였다. 또한 구한 유효선량 값을 국외 연구자들에 의한 결과 값과 비교 하였다.

1) 치과 검사별 등가선량 및 유효선량

모든 치과 검사에서 침샘에서 가장 많은 흡수선량이 나타났다. 침샘의 경우 ICRP 60에서는 조직하중계수의 저평가로 인해 침샘이 포함되는 방사선 진단 검사에서 유효선량이 낮게 평가 되었다. 그러나 ICRP 103에서침샘에 대한 조직하중계수가 0.01로 평가됨으로서 침샘의 방

사선 장해를 포함하는 선량 평가를 할 수 있다. CT 검사와 CBCT 검사 간의 부위 별 선량 비교를 보면 전체적으로 CT 검사에서의 조직등가선량이 CBCT 검사에 비해 높게 나타났다. 또한 CT 검사와 CBCT 검사에서상악골과 하악골의 많은 선량 차이를 볼 수 있다. 두 검사 모두 상

악골 촬영의 경우 갑상선이 포함되지 않으며 하악골 촬영의 경우 갑상선이 포함되어 하악골에서의 갑상선 선량이 상악골에서의 선량 보다 2배 이상 높게 측정되었다.

Table 4. Equivalent dose and effective dose according to dental radiography (μSv)

Table 5. Comparison of effective dose between the literature and this study (μSv)

Ⅳ. 고 찰

치과 방사선 검사에서 조직의 등가선량과 ICRP 60, 103를 이용한 유효선량을 비교하였으며. 계산한 유효선량을 기존의 연구 결과와 비교 분석 하였다. Ludlow5)의 ICRP 103을 통한 파노라마 검사와 세팔로 검사의유효선량 비교를 보면 파노라마 검사가 세팔로 검사에 비해 높은 선량을 보여 주고 있으면 본 연구의 연구 결과 또한 ICRP 103을 통해 얻은 파노라마 검사의 결과가 세팔로 검사의 결과에 비해 높은 선량을 나타내고있다. 그리고 CT 및 CBCT 검사의 유효선량에 관한 결과가 대부분이 하악골 검사가 상악골 검사에 비해 높은 선량 값을 나타내고 있었다. 기존의 연구 결과와의 분석을 통해 선량에 대한 경향 분석은 가능하나 측정된값에 대한 비교에는 어려움이 있었다. 기존의 연구자와 검사하는 장비부터 검사 조건까지 모두 다른 조건에서 측정 및 계산이 되었기에 선량 차이는 날 수 밖에 없었다(Table 5).

각 치과 방사선 검사는 다른 촬영 조건과 다른 진단 목적을 가지고 있다. 단순히 유효선량에 대한 비교는 무의미하다고 생각한다.

다만 각각 검사의 목적에 맞는 검사 방법을 사용함으로써 환자의 치아 병변의 진단에 유용한 검사 방법을 해야 한다. CBCT의 경우 CT가 가지고 있는 고가의 장비라는 점과 고선량이라는 점을 보완하기 위해 나온장비이다. CT 검사의 유효선량을 기준으로 CBCT 검사에서의 선량 감소를 분석하였다. ICRP 60을 적용한 선량 감소는 상악골 CBCT 검사의 경우 39.6 μSv(42%) 감소하였으며, 하악골의 경우 153.7 μSv(54%) 감소하였고 ICRP 103을 적용한 선량 감소는 상악골의 경우 73.1 μSv(25%) 감소하였으며, 하악골의 경우 98.2 μSv(20%) 감소하였다.

기존의 CT 검사에 비해 약 30% 선량감소율을 보였다. CBCT와 CT에서 하악골검사가 상악골검사에 비해 유효선량이 2배 이상의 선량 차이를 볼 수 있었다. 하악골 검사시 방사선 감수성이 예민한 갑상선의 포함으로인해 선량이 증가하는 것을 볼 수 있다. Kotstas14)는 CBCT에 있어 갑상선 및 경추 부분에 차폐체를 도입함으로써 유효선량 값이 30% 이상 감소효과를 보였으며, 방사선 진단 검사에서 시술자 및 환자에 대한 갑상선선량에 대한 감소 및

방어 연구는 계속 진행 중이다. 예를 들어 C.P. Shortt15)에 의한 연구를 보면 신경 중재적 방사선 시술시 환자의 갑상선을 차폐함으로써 차폐를 하지 않고 시술 하였을 때보다 50%의 선량 감소 효과률을 보여 주고있다. 치과방사선 검사의 CBCT에서도 이와 같은 환자의 갑상선 차폐에 관한 연구가 필요하다. CBCT와 다른 구강 외 치과검사와의 선량의 차이를 보면 CBCT에서 ICRP 103을 적용한 상악골 검사의 경우, 세팔로검사에 비해 14배 정도 많았으며, 파노라마 검사에 비해 7배 정도 많았다. 그리고 하악골 검사의 경우는 상악골 검사 보다 더 많은 27배, 13배의 차이로 더 많은 선량 차이가 났다. 과거에 치과 방사선 검사에 있어CT의 도입은 정확한 치아 병변에

대한 판단을 할 수 있는 검사 법이였다. 하지만 CT 장비의 경우 고가의 장비이며 넓은 면적의 검사실을 확보해야 하는 등의 이유로 대학병원급 이상에만 설치되었다. CT검사의 단점을 보완하기 위한 CBCT 장비의도입으로 인해 CBCT의 검사건수는 급속도로 증가하였다. 건강 보험

심사 평가원에 따르면 2008년 대비 2009년에 개원한 치과의원의 수는 492곳이였으면 치과의원에 설치된 CBCT의 장비 수는 453대였다. 즉, 개원 하는 치과의원 대부분이 CBCT 장비를 도입하고 있었다. 2009년도개인치과의원에서의 CBCT 장비의 수는 10대 중 1곳에 설치되어 있는 실정이다1). CT와 CBCT 간의 선량을 비교 했을 때 CBCT로 인한 선량 감소 효과를 볼 수 있지만, 개인치과 병원에서 세팔로 검사와 파노라마검사만이 구강 외 검사였던 과거에 비해 CBCT 장비의 수 및 검사 건수에 대한 증가는 국내 치과의 대부분을 차지하고 있는 치과의원에

서의 환자피폭 선량을 증가 할 수밖에 없다. 또한 현재 CBCT에 대한 진단참조준위 및 안전 가이드라인에 대한 기준이 새워져 있지 않았으며, CBCT에 있어서 선량 감소에 대한 연구 또한 부족한 편이다.

Ⅴ. 결 론

치과 방사선 검사 별 조직등가선량과 유효선량을 구하였다. 구강 외 검사 간의 등가선량 및 유효선량 비교한 결과 CBCT 검사는 CT 검사에 비해 약 30% 이상의 선량 감소율이 나타나지만 파노라마 검사 및 세팔로검사에 비해서는 높은 선량을 나타냈다. 최근 들어 계속적으로 증가하고 있는 CBCT 검사의 진단참조준위 제시와 선량 감소 방안에 대한 연구가 필요하다.

감사의 글

본 연구는 교육과학기술부(과제번호: 2009-0071844) 지원으로 수행되었다.

참 고 문 헌

  1. Health insurance review & assessment service, state of medical equipment according to classification(2003-2010)

  2. Rebecca Smith-Bindman, MD; Jafi Lipson, MD; Ralph Marcus, BA; Kwang-Pyo Kim, PhD; Mahadevappa Mahesh, MS, PhD; Robert Gould, ScD; Amy Berrington de González, DPhil; Diana


L.Miglioretti, PhD: Radiation Dose Associated with common computed tomography examinations

and the associated life time Attributable risk of cancer Arch Intern Med. 169(22): 2078-2086, 2009

  1. United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and effect


of ionizing radiation. Report Vol. 1 UNSCEAR publications (2000)

  1. International Comission on Radiological Protection. 1990 Recommendations of the International


Commission on Radiological Protection. ICRP Publication 60. (Oxford: Pergamon Press) (1991)

  1. International Commission on Radiological Protection. The 2007 Recommendations of the ICRP,


ICRP Publication 103. Elsevier, 2008

  1. J.A. Roberts, N.A. Drage, J. Davies and D.W. Thomas: Effective dose from cone beam CT examinations in dentistry, Br J Radiol, 82(1), 35–40, 2009

  2. F. Gijbels, R. Jacobs, R. Bogaerts, D. Debaveye, S. Verlinden and G. Sanderink: Dosimetry of


digital panoramic imaging. Part I. Patient exposure, Dentomaxillofac Radiol, 34(3), 145–149, 2005

  1. John B Ludlow, DDS, MS, Laura E, Davies-Ludlow, Bs and Stuart C. white, DDS, PhD: Patient risk related to common dental radiographic examination JADA, 139(9), 1237-1243, 2008

  2. Heiko visser, Tina Rodig and Klaus-Peter Hermann: Dose reduction by direct-digital cephalometric radiography: The angle orthodontist, 71(3), 159-163, 2001

  3. E. Hirsch, U. Wolf, Heinicke and M.A.G. Silva: Dosimetry of the cone beam computed tomography veraviewepocs 3D compared with the 3D Accuitomo in different fields of view,


Dentomaxillofac Radiol, 37(5), 268–273, 2008

  1. J.B. Ludlow, M. Ivanovic and C. Hill: Comparative dosimetry of dental CBCT devices and 64 slice CT for oral and maxillofacial radiology, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 106(1), 106–114, 2008

  2. M Loubele, R. Bogaerts, E.V. Dijck, R. Pauwels, S. Vanheusden and P. Suetens et al.: Comparison between effective radiation dose of CBCT and MSCT scanners for dentomaxillofacial applications, Eur J Radiol, 71(3), 461–468, 2009

  3. Lee JN, Han WJ, Kim EK: Absorbed and effective dose from newly developed cone beam computed tomography in Korea, korean academy of oral and maxillofacial radi‐ology, 37(2), 93-102, 2007

  4. Kostas Tsiklakis, Catherine Dontaa, Sophia Gavalaa, Kety Karayiannia, Vasiliki: Dose reduction


maxillofacial imaging using low dose Cone Beam CT Euopean Journal of Radiology, 56(3), 413-417, 2005

  1. C.P. Shortt, N.F. Fanning, L. Malone: Thyroid Dose During Neurointerventional Procedures: Dose Lead Shielding Reduce the Dose? Cardiovasc Intervent Radiol, 30(5), 922-927, 2007ꋯAbstract


 

Evaluation of Effective Dose in Dental Radiography

Su-Chul Han ․ Bo-Ram Lee ․ Gwi-Soon Shin1) ․ Jong Hak Choi ․

Chang-Seo Park2) ․ Hyok Park2) ․ Kye-yong Chang2) ․ Bo-Ram Kim2) ․ You-Hyun Kim

Department of Radiologic Science, College of Health Science, Korea University

1)Department of Radiologic Technology, SongHo Health College

2)Dental Hospital, College of Dentistry, Yonsei University

Along with the developments of science technology, up-to-date medical radiation equipments are

introduced. Those equipments has brought many progresses in diagnosing patients not only in the quantitative aspects but in the qualitative ones. Especially, in the case of dental radiography, patients can be exposed more than CT, cone beam computed tomography (CBCT). In this study, we used human phantom and TLD-100H to measure the organ dose in each dental radiography and computed the effective dose according to ICRP (International Committee for Radioactivity Prevention) 60, 103. We measured the effective dose to be 5.1 and 29.5μSv in the panoramic radiography and 11.2 and 14.4μSv in the cephalometric radiography respectively. We also executed the CBCT and CT test on the maxillaries and the mandibles and found the amounts of effective dose were 53.7, 209.6, 129, and 391.5μSv respectively in the CBCT and 93.3μ, 139.5, 282.7 and 489.7μSv in the CT test. Consequently, it was shown that the effective dose in the CBCT test was lower than one in the CT test, but was higher in both panoramic and cephalometric radiography.

Key Words : Dental radiography, Effective dose, ICRP 60, 103, Dose reduction
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