내경동맥의협착및폐색의평가에있어서의비침습적인영상의학적검사방법들의비교연구 : CT 혈관조영술 (CTA), 유체속도강조자기공명혈관조영술 (TOF-MRA), 조영증강자기공명혈관조영술 (CE-MRA) 이준형 1 정태섭 1 이경열 2 서상현 1 목적 : 내경동맥의협착및폐색의진단에대해 CT혈관조영술 ( 이하 CTA), 유체속도강조자기공명혈관조영술 ( 이하 TOF-MRA), 조영증강자기공명혈관조영술 ( 이하 CE-MRA) 을비교하였다. 대상및방법 : 내경동맥의협착및폐색질환이의심되는증상이있거나, 건강검진상시행한색도플러초음파상내경동맥의협착이 50% 이상의심되는환자총 20명을대상으로시행하였다. 전향적으로 CTA, TOF-MRA, CE-MRA를함께시행하였으며, CTA를표준지표로하여세검사간의상관관계및민감도, 특이도, 양성예측도, 음성예측도, 정확도를측정하였다. 결과 : 세검사의협착도간의유의한차이는없었다 (p > 0.05). CTA와 TOF-MRA간의상관계수는 0.932, CE-MRA와의상관계수는 0.971로나타났다. 50% 이상의협착및폐색에대한 TOF-MRA의민감도, 특이도, 양성예측도, 음성예측도, 정확도는 83.3%, 87.5%, 71.4%, 93.3%, 86.4% 였으며, CE MRA는 83.3%, 93.8%, 83.3%, 93.8%, 90.9% 로나타났다. 결론 : 내경동맥의협착의평가에서 TOF-MRA와 CE-MRA는 CTA와높은상관관계를보였다. 서론뇌졸중은사망과기능손실의주요원인이되는심각한질병이며, 미국에서는매년약 700,000명의환자가새롭게뇌졸중을진단받거나재발하게되고, 매년약 163,000명이사망한다, 이중경동맥의죽상경화증으로인한뇌졸중의사례는약 20% 에달하게된다. 뇌혈관질환은한국인의사망원인순위에서도암에이어 2위를차지하고있으며, 이중 70% 이상이허혈성뇌졸중과연관된질환으로추정되고있다 (1). 따라서뇌혈관질환을일으킬수있는고혈관경화반 (plaque) 를발견할수있는영상기술들이발전하고있으며, 병변의발견과협착의정도는치료방향에도중요한역할을하기때문에여러가지영상의학적방법들이뇌혈 관질환의발견과평가에이용되고있다 (2, 3). 허혈성뇌졸중에서혈관평가의최적표준 (gold standard) 으로는디지털감산혈관조영술 (Digital Subtraction Angiography, 이하 DSA) 이사용되고있지만 DSA는침습적인검사방법으로위험이따르며, 비용과시간과혈관조영술이가능한의사등의많은자원을필요로한다. 비침습적인혈관평가의검사방법으로 CT혈관조영술 (Computed tomography angiography, 이하 CTA), 유체속도강조자기공명혈관촬영술 (Time of flight Magnetic Resonance Angiography, 이하 TOF-MRA), 조영증강자기공명혈관조영술 (Contrast enhanced MRA, 이하 CE-MRA) 등이사용되고있으며지금까지시행된여러연구들에서 CTA는 MRA와비교하여높은공간해상력, 혈류에대한낮은의존도, 혈관내외의정보제공등의장점이있는것으로알려져있다 (4, 5). 의료기기의발달 대한자기공명의과학회지 15:234-241(2011) 1 연세대학교의과대학강남세브란스병원영상의학과 2 연세대학교의과대학강남세브란스병원신경과접수 : 2011 년 6 월 14 일, 수정 : 2011 년 7 월 22 일, 채택 : 2011 년 10 월 25 일통신저자 : 서상현, (135-720) 서울특별시강남구언주로 712 번지, 강남세브란스병원영상의학과 Tel. (02) 2019-3510 Fax. (02) 3462-5472 E-mail: suhsh11@yuhs.ac - 234-
내경동맥의협착및폐색의평가에있어서의비침습적인영상의학적검사방법들의비교연구 로인해현대의학의추세는비침습적인검사방법의선호도가과거에비해서점차높아지고있으며 CTA, MRA와같은영상의학적검사방법들도나날이발전하고있다. CTA가가장 DSA에근접한영상을제공한다고하지만, MRA의비약적인발전과프로토콜에대한연구, 조영제의발전으로인해 MRA 영상의질도많이높아졌으며방사선에대한노출이없다는장점으로인해최근 MRA를뇌혈관평가의선별검사로사용하는비율이증가하고있다. 따라서본연구에서는 CTA, TOF-MRA, CE-MRA의뇌혈관평가에있어서의상관관계와, 그동안많은연구에서밝혀졌던대로 CTA가이들중가장진단적가치가높다는가정하에 CTA를표준지표로삼고각각의민감도, 특이도, 양성예측도, 음성예측도, 정확도를비교하여보았다대상과방법환자군 2010년 8월부터 2010년 10월까지내경동맥의협착및폐색질환이의심되는소견이있는환자 (n=17명) 과증상은없지만건강검진을위해시행한내경동맥의색도플러초음파검사상내경동맥의 50% 이상의협착이의심되는환자 (n=3) 을대상으로전향적으로시행되었다. 이 20명의환자들은내경동맥협착의증상이있거나의심되 었을때부터약 2일이내에 CTA를시행하였으며, CTA를시행한후 3일이내에 MRA(TOF-MRA, CE-MRA) 를시행하였다. CTA를시행한후 MRA를시행하기까지의평균지연기간은 1.2일이었다. 성별은여성이 9명, 남성이 11명이었으며, 연령분포는 55세에서 76세까지였고, 평균연령은 60.4세였다. 영상기법 CTA는 64채널컴퓨터단층촬영기 (Sensation 64, Simens medical system, Erlangen, Germany) 를이용하여시행하였으며 FOV 217 mm 217 mm, section thickness 1 mm, tube voltage 120 kv/207 mas, imaging time 22-23 seconds 이었으며, 조영제로는 Ultravist (Bayer-Schering, Berlin, Germany) 100 ml를 4-4.5 ml/sec 속도로정맥내주입하였다. 3D TOF-MRA와 CE-MRA는 1.5T 자기공명영상기 (Avanto, Simense medical system, Erlangen, Germany) 를이용하여시행하였으며, 3D TOF-MRA에서는 TR/TE = 24/7 msec, flip angle 25, image matrix 199 256, slice thickness 1.2 mm, slice/slab 44, imaging time 7 min 23 seconds, CE-MRA에서는 TR/TE = 3.1/1.1, flip angle 30, image matrix 192 256, slice/ slab 80, imaging time 20 seconds이었으며조영제로는 a b c Fig. 1. A 73-year-old male patient with headache and dizziness. (a) TOF-MRA (b) CE-MRA (c) CTA, These images show a low grade stenosis in right ICA. - 235-
이준형외 Dotarem (Guerbet SA, Paris, France) 을 0.1 mmol/kg 용량, 1-2 ml/sec 속도로정맥내주입하였다. 영상분석및통계양측내경동맥을평가하였으며, 범위는경동맥구부에서 supraclinoid 분절까지를포함하였다. 20명의환자군에서내경동맥을각각 20쌍의총 40개의혈관을 TOF-MRA, CE-MRA, CTA를이용하여평가하였다. 내경동맥의협착을 NASCET(North American Symptomatic Carotid Endarterectomy) criteria를적용하여평가한후 CTA를표준지표로삼고 TOF-MRA에서의수치와 CE- MRA의수치를각각대응표본 T 검정 (Paired T- test) 을통하여평균을비교하였고, Pearson 상관관계분석을통해 CTA 와 TOF-MRA, CTA와 CE-MRA간의상관관계를각각비교하였다. 모든통계학적분석은 SPSS version 12.0을사용하였으며신뢰구간은 95%(p < 0.05) 로정하였다. 또한, 6단계 ( 정상 : 1등급, 1-29% 협착 : 2등급, 30-49% 협착 : 3등급, 50-69% 협착 : 4등급, 70-99% 협착 : 5등급, 폐색 ) 로나누어서평가하였으며, 최근두개내혈관에있어서의중재적시술의적응증이 70% 의협착에서점차 50% 까지확대되고있는것을고려하여 (6) CTA에서 50% 이상의협착이있는경우를표준지표로정하여저등급과고등급협착, 완전폐색으로구분하여 TOF-MRA, CE-MRA의민감도, 특이도. 양성예측도및음성예측도, 정확도를평가하였다 (Fig. 1). 영상분석에있어서는 TOF-MRA, CE-MRA는 MIP (Maximun Intensity Projection) 영상을재구성하여사용하 였고, CTA는 Coronal and sagittal MIP 영상을사용하였다. MRA는 3D image를돌려가며각각의예에서가장협착이잘나타나는부위에서협착을측정하였으며, CTA의경우는 Coronal and sagittal 영상중에서협착이더잘나타나는부위에서협착을측정하였다. 협착의측정은 PACS (Picture Achieving communication system, Centricity radiology RA1000 workstation, GE health care) 의 electronic caliper를사용하였다. 영상의평가는 2명의영상의학과의사가시행하였으며, 먼저 1 명의영상의학과의사가협착을평가한뒤 2명의영상의학과의사가같이영상을보면서의견의일치를얻는과정을통하였다. 결과 CTA에서총 20명의환자군에서 20쌍의내경동맥을평가한결과 16명의환자의 24개의혈관에서병변이관찰되었으며모두경동맥구부의병변이었다. 병변이없는 16개의혈관을제외한 24개의내경동맥의병변중 2등급협착이 10개, 3등급협착이 8개, 4등급협착이 1개, 5등급협착이 2개, 폐색이 3개였다. TOF-MRA와 CE-MRA의경우 3예에서폐색을모두진단하였으며, TOF-MRA는 30-49%, 50-69%, 70-99% 협착에서각각 1예에서 1-29%, 30-49%, 50-69% 협착으로과소평가하였고, 30-49% 협착 2예에서 50-69% 협착으로과대평가하였다. CE-MRA는 50-69%, 70-99% 협착각각 1예에서병변을 30-49%, 50-69% 협착으로과소평가하였고, 30-49% 협착 1예에서 50-69% 협착으로과대평가하였다 (Table 1). Table 1. Comparison of the Degree of ICA Stenosis with CT angiography, TOF-MRA and CE-MRA Degree of Stenosis Stenosis 1-29% 30-49% 50-69% 70-99% Occlusion CT angiography TOF-MRA 01-29% 9 1 0 0 0 30-49% 0 4 1 0 0 50-69% 0 2 0 1 0 70-99% 0 0 0 1 0 Occlusion 0 0 0 0 3 CT angiography CE-MRA 01-29% 9 0 0 0 0 30-49% 0 6 1 0 0 50-69% 0 1 0 1 0 70-99% 0 0 0 1 0 Occlusion 0 0 0 0 3 Note. TOF-MRA = Time of flight Magnetic Resonance Angiography CE-MRA = Contrast enhance MRA - 236-
내경동맥의협착및폐색의평가에있어서의비침습적인영상의학적검사방법들의비교연구 50% 이상의협착및폐색에대한 TOF-MRA의민감도, 특이도, 양성예측도, 음성예측도, 정확도는 83.3%, 87.5%, 71.4%, 93.3%, 86.4% 였으며, CE-MRA는 83.3%, 93.8%, 83.3%, 93.8%, 90.9% 로나타났다 (Tables 2, 3). McNemer test를사용하여두기법간의결과를비교하였으며, NPV에서는검정값이나오지않았지만나머지값들은통계적으로유의한차이는없는것으로나타났다 (p > 0.05). 대응표본 T 검정에서는 CTA와 TOF-MRA, CTA와 CE- MRA, TOF-MRA와 CE MRA의협착도간에유의한차이는없는것으로나타났다 (p > 0.05). CTA와 TOF-MRA간의상관계수는 0.932, CTA와 CE- MRA간의상관계수는 0.971로 CTA와 CE-MRA간의상관관계가더높은것으로나타났으나차이는없었다. 2개의예에서는 CTA에서는석회화경화반에의해내경동맥 Table 2. Comparison of 3-level Degree of ICA Stenosis with CT Angiography, TOF-MRA and CE-MRA Degree of Stenosis Stenosis Low High Occlusion CT angiography TOF-MRA Low 14 1 0 High 02 2 0 Occlusion 00 0 3 CT angiography CE-MRA Low 15 1 0 High 01 2 0 Occlusion 00 0 3 Note. TOF-MRA = Time of flight Magnetic Resonance Angiography CE-MRA = Contrast enhance MRA 의근위부에미세한협착을일으켰지만, TOF-MRA와 CE- MRA에서는관찰되지않았다 (Fig. 2). 고찰 CTA는 TOF-MRA나 CE-MRA에비해전반적으로질적으로우월한영상을제공한다고알려져있다 (5, 7). 하지만현재가장널리쓰이는표준지표는 DSA이므로 CTA를표준지표로삼아 TOF-MRA와 CE-MRA를비교한것은본연구에있어서의가장큰제한점이다. 그러나, 그동안발표된여러문헌들에서 MRA와비교하여 CTA가 DSA와의상관관계가높다고알려져있고, 공간해상력이높고, 혈류의흐름에의한영향이적으며, 더많은혈관내와혈관외의정보를제공한다고알려져있기때문에연구의목적에는부합할것으로생각된다 (4). 또한 CTA는비교적짧은영상획득시간및높은공간해상도로인하여두개내동맥병변의진단에효과적으로이용되어왔다. 그러나 CTA 영상을얻기위해서는신독성이있는조영제를사용해야하고방사선에노출된다는위험성이있다. 특히장기간추적검사를필요로하는환자들에게의방사선의축적에대한고려가필요하다 (8). 본연구에서는 CE-MRA가 TOF-MRA에비해서 CTA와의상관관계가더높게나타났지만 TOF-MRA 역시우수한상관관계를나타냈다. TOF-MRA역시영상의질을높이고인공물의영향을줄이기위해다양한시퀀스가개발되고있으며 CE- MRA에비해작은복셀사이즈도기여한것으로생각된다 (9, 10). 최근발표되는몇몇연구결과들에서기존의 TOF-MRA가 CE-MRA에비해서정확성이떨어진다는연구결과와상반되는결과들이나오고있으며, 특히 50-70% 이상의고등급협착에서더욱차이가없거나오히려 TOF-MRA가더우수한성적을보인다는결과들이나오고있다 (4, 11, 12). 본연구에서는뚜렷한차이는없는것으로나타났다. CTA에서는석회화경화반에의한미세한협착이관찰되었지만, MRA에서발견되지않았던 2개의예는, MRA의비교적낮 Table 3. Diagnostic index of TOF-MRA and CE-MRA TOF-MRA Sensitivity Specificity PPV NPV Accuracy Low 87.5% 83.3% 93.3% 71.4% 86.4% High 66.7% 89.5% 50.0% 94.4% 86.4% Occlusion 100.0% 100.0% 100.0% 100.0% 100.0% High or occlusion 83.3% 87.5% 71.4% 93.3% 86.4% CE-MRA Low 93.8% 83.3% 93.8% 83.3% 90.9% High 66.7% 93.7% 66.7% 93.8% 89.5% Occlusion 100.0% 100.0% 100.0% 100.0% 100.0% High or occlusion 83.3% 93.8% 83.3% 93.8% 90.9% Note. TOF-MRA = Time of flight Magnetic Resonance Angiography CE-MRA = Contrast enhance MRA, PPV = Positive predictive value, NPV = Negative predictive value - 237-
이준형외 은공간해상력으로인해작은크기의석회화를발견하지못한것으로생각된다 (13). 또한경화반이혈류의감소에영향을미쳤다면 CE-MRA에서원위부의조영제의농도를감소시킨다 고알려져있지만 (14), 이예에서는원위부의신호감소도발견되지않았다. 따라서경화반의크기가작고, 혈류의흐름에미치는영향이미미했기때문으로생각된다. Fig. 2. A 64-year-old male non-symptomatic patient. (a) TOF-MRA shows no stenotic lesion or plaque. (b) CE-MRA shows no stenotic lesion or plaque. (c, d) CTA(C: coronal, D: sagittal) shows a small calcified plaque in the left proximal ICA with mild degree stenosis. a b c d - 238-
내경동맥의협착및폐색의평가에있어서의비침습적인영상의학적검사방법들의비교연구 본연구에서는 50% 이상의고등급협착과완전폐색의진단에 TOF-MRA와 CE-MRA는 TOF-MRA의양성예측도 (71.4%) 를제외하고는 83-94% 의높은민감도, 특이도, 음성예측도와정확도를보였다. 이는이전에발표되었던여러논문들과같은맥락의결과이다 (2, 7, 15, 16). TOF-MRA에서양성예측도가비교적낮게나타난것은 CE-MRA가 1개의저등급협착을고등급으로, 1개의고등급협착을저등급으로평가한반면에, TOF-MRA는 2개의저등급협착을고등급으로, 1개의고등급협착을저등급으로평가한것에영향을받은것으로생각된다. 특히평가의대상이된혈관들중 18개의혈관이정상소견이었기때문에병변이있는혈관의수가 22개로적고, 병변중에고등급협착이나폐색인병변이 6개였기때문에더욱영향을미쳤을것으로생각된다. 이것은평가의대상이되었던환자군의수가 20명으로비교적적은것과더불어본연구의제한점이지만, 그제한점을극복하기위해협착의정도를구간별로나누어서 NASCET criteria를적용하여수치화하여각수치간의상관관계를통계학적으로평가하였으며, TOF-MRA와 CE-MRA의민감도, 특이도, 양성예측도, 음성예측도, 정확도를구하기위해서다시 50% 협착을기준으로저등급, 고등급협착, 완전폐색으로나누어평가하였기때문에결과의신뢰도에는큰영향이없었을것으로생각된다. 또한가돌리늄함유조영제와관련하여신원성전신섬유증 (Nephrogenic systemic fibrosis, 이하 NSF) 에대한위험성이고려될수있으며이는자유가돌리늄이온 (Gd3+) 과연관되어있다고알려져있지만 (17, 18), 거대고리킬레이트는신체내로유리되는자유가돌리늄이온의양을최소화시키는것으로알려져있고, 현재까지거대고리제제인 Gd- DOTA(Dotarem) 의사용으로인해 NSF가발생하였다는명확한사례는없었다 (17, 19, 20). 결론적으로내경동맥의협착및폐색에있어서 MRA(TOF- MRA, CE-MRA) 는 CTA과대등한진단적가치를보였으며 CE-MRA가 TOF-MRA에비해약간더높은상관관계를보이는것으로나타났다. 내경동맥의병변을평가하기에는 TOF- MRA도 CE-MRA에비해크게부족하지않았지만, 일부추골동맥기시부의병변까지평가하기위해서는 CE-MRA가유용할것으로생각되었다. 비용-시간대비로 CTA가장점을갖고있지만, MRA에비해높은조영제부작용의빈도와방사선노출을고려할때, TOF-MRA와 CE-MRA를상호보완적으로사용하는것이보다안전하게내경동맥의협착을진단하는데있어서도움이될것이다. 참고문헌 1.2009 년사망원인통계결과. 통계청 : 2010.9.9, 2009 2.Randoux B, Marro B, Koskas F, Duyme M, Sahel M, Zouaoui A, et al. Carotid artery stenosis: prospective comparison of CT, three-dimensional gadolinium-enhanced MR, and conventional angiography. Radiology 2001;220:179-185 3.Mhlenbruch G, Das M, Mommertz G, Schaaf M, Langer S, Mahnken AH, et al. Comparison of dual-source CT angiography and MR angiography in preoperative evaluation of intraand extracranial vessels: a pilot study. Eur Radiol 2010;20:469-476 4.Babiarz LS, Romero JM, Murphy EK, Brobeck B, Schaefer PW, Gonzlez RG, et al. Contrast-enhanced MR angiography is not more accurate than unenhanced 2D time-of-flight MR angiography for determining > or = 70% internal carotid artery stenosis. AJNR Am J Neuroradiol 2009;30:761-768 5.Alvarez Linera J, Benito-Len J, Escribano J, Campollo J, Gesto R. Prospective evaluation of carotid artery stenosis: elliptic centric contrast-enhanced MR angiography and spiral CT angiography compared with digital subtraction angiography. A- JNR Am J Neuroradiol 2003;24:1012-1019 6.Sadikin C, Teng MM, Chen T, Luo C, Chang F, Lirng J, et al. The current role of 1.5T non-contrast 3D time-of-flight magnetic resonance angiography to detect intracranial steno-occlusive disease. Journal of the Formosan Medical Association 2007;106:691-699 7.Lell M, Fellner C, Baum U, Hothorn T, Steiner R, Lang W, et al. Evaluation of carotid artery stenosis with multisection CT and MR imaging: influence of imaging modality and postprocessing. AJNR Am J Neuroradiol 2007;28:104-110 8.Villablanca JP, Nael K, Habibi R, Nael A, Laub G, Finn JP. 3 T contrast-enhanced magnetic resonance angiography for evaluation of the intracranial arteries: comparison with time-offlight magnetic resonance angiography and multislice computed tomography angiography. Invest Radiol 2006;41:799-805 9. 장남규, 서정진, 정태웅, 정광우, 김재규, 강형근, 조기현. 뇌경색환자에서 Enhanced 3D-TOF 자기공명혈관조영술 : 고식적혈관조영술과의비교. 대한방사선의학회지 2000;42:575-583 10.Atkinson D, Brant Zawadzki M, Gillan G, Purdy D, Laub G. Improved MR angiography: magnetization transfer suppression with variable flip angle excitation and increased resolution. Radiology 1994;190:890-894 11.Townsend TC, Saloner D, Pan XM, Rapp JH. Contrast material-enhanced MRA overestimates severity of carotid stenosis, compared with 3D time-of-flight MRA. J Vasc Surg 2003;38:36-40 12.DeMarco JK, Huston J, Bernstein MA. Evaluation of classic 2D time-of-flight MR angiography in the depiction of severe carotid stenosis. AJR Am J Roentgenol 2004;183:787-793 13.Rasanen HT, Manninen HI, Vanninen RL, Vainio P, Berg M, Saari T. Mild carotid artery atherosclerosis: assessment by 3-dimensional time-of-flight magnetic resonance angiography, with reference to intravascular ultrasound imaging and contrast angiography. Stroke 1999;30:827-833 14.Evans AJ, Richardson DB, Tien R, MacFall JR, Hedlund LW, Heinz ER, et al. Poststenotic signal loss in MR angiography: effects of echo time, flow compensation, and fractional echo. A- JNR Am J Neuroradiol 1993;14:721-729 15.Sardanelli F, Zandrino F, Parodi RC, De Caro G. MR angiography of internal carotid arteries: breath-hold Gd-enhanced 3D fast imaging with steady-state precession versus unenhanced - 239-
이준형외 2D and 3D time-of-flight techniques. J Comput Assist Tomogr 1999;23:208-215 16.Kramer H, Runge VM, Morelli JN, Williams KD, Naul LG, Nikolaou K, et al. Magnetic resonance angiography of the carotid arteries: comparison of unenhanced and contrast enhanced techniques. Eur Radiol 2011 17.Morcos SK. Nephrogenic systemic fibrosis following the administration of extracellular gadolinium based contrast agents: is the stability of the contrast agent molecule an important factor in the pathogenesis of this condition? Br J Radiol 2007;80: 73-76 18.Grobner T. Gadolinium--a specific trigger for the development of nephrogenic fibrosing dermopathy and nephrogenic systemic fibrosis? Nephrology, Dialysis, Transplantation 2006;21:1104-1108 19.Port M, Ide J, Medina C, Robic C, Sabatou M, Corot C. Efficiency, thermodynamic and kinetic stability of marketed gadolinium chelates and their possible clinical consequences: a critical review. Bio Metals 2008;21:469-490 20.Morcos SK. Extracellular gadolinium contrast agents: differences in stability. Eur J Radiol 2008;66:175-179 - 240-
내경동맥의협착및폐색의평가에있어서의비침습적인영상의학적검사방법들의비교연구 J. Korean Soc. Magn. Reson. Med. 15:234-241(2011) Comparison of Non-invasive Imaging Studies in the Evaluation of Carotid Artery Stenosis and Occlusion: CT Angiography, Time-of-Flight MR Angiography and Contrast-Enhanced MR Angiography Junhyung Lee 1, Tae-Sub Chung 1, Kyung-Yul Lee 2, Sang Hyun Suh 1 1 Department of Radiology, Gangnam Severance Hospital, Yonsei University College of Medicine 2 Department of Neurology, Gangnam Severance Hospital, Yonsei University College of Medicine Purpose : We compared non-invasive imaging studies of CTA, TOF-MRA and CE-MRA to evaluate detecting internal carotid artery stenosis and occlusion. Materials and Methods : We enrolled 20 patients with clinically suspected internal carotid artery stenosis and occlusion, or asymptomatic patient with more than 50% stenosis suspected on color Doppler ultrasonography for regular check-up. Prospectively, CTA, TOF-MRA and CE-MRA were performed, and sensitivity, specificity, positive predictive value, negative predictive value and accuracy of TOF-MRA and CE- MRA using CTA as a reference standard for detecting more than 50% stenosis were evaluated, and correlations of measured percent stenosis between 3 imaging studies were also evaluated. Results : No significant difference was found between 3 imaging studies in measuring stenosis(p>0.05). Correlation coefficient was 0.932 between CTA and TOF-MRA, and 0.971 between CTA and CE-MRA. TOF-MRA had 83.3% sensitivity, 87.5% specificity, 71.4% positive predictive value, 93.3% negative predictive value and 86.4% accuracy for detecting more than 50% stenosis and occlusion. CE-MRA had 83.3% sensitivity, 93.8% specificity, 83.3% positive predictive value, 93.8% negative predictive value and 90.9% accuracy. Conclusion : TOF-MRA and CE-MRA provided high correlations in the evaluation of internal carotid artery stenosis and occlusion. Index words : Carotid artery stenosis Computed tomography angiography (CTA) Magnetic resonance angiography (MRA) Address reprint requests to : Sang Hyun Suh, M.D., Department of Radiology, Gangnam Severance Hospital, 712 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea. Tel. 82-2-2019-3510 Fax. 82-2-3462-5472 E-mail: suhsh11@yuhs.ac - 241-