Takayasu arteritis in Thailand: clinical and imaging features

International Journal of

cardiology International Journal of Cardiology 54 Suppl. (1996) SIOI-SII8

Takayasu arteritis in Thailand: clinical and imaging features Nitaya Suwanwelav", Chaliow Piyachon b "Depanmem of Radiology, Chulalongkorn University, Bangkok, Thai/and bDepartment of Radiology, Faculty of Medicine, Chiangmai University, Chiangmai, Thailand

Abstract

Purpose: To present and evaluate the clinical and imaging features of patients with Takyasu arteritis in Thailand. Materialsand methods: Clinical and angiographic findings were studied in 63 patients with Takayasu arteritis collected at Chulalongkorn Hospital Medical School, Bangkok. Imaging features including CT scan in 15 patients, magnetic resonance imaging in 14 patients and magnetic resonance angiography in ten patients were evaluated and compared to angiography. Results: Among 63 patients there were 43 females and 20 males with the ratio female to male 2.15:1. The most common age groups were in the third and fourth decades of life. The most common clinical findings were hypertension and absence or weakness of pulses. Elevated erythrocyte sedimentation rate was found in 50%. For angiography, the most common vessel affected was the abdominal aorta (20"10). The second and third most common sites were renal arteries (18.7%) and the subclavian arteries (14.3%). Coronary artery involvement was found in two out of eight patients. No pulmonary involvement was found in eight cases studied by pulmonary angiography. For classification of angiogram, the most common type of involvement (66.7%)was extensive involvement of the aorta and branches (type V of new classification established from International Conferences on Takayasu arteritis in Tokyo 1994). No patient was found to have only involvement of brachiocephalic branches or ascending aorta and brachiocephalic branches. CT scan showed calcification in the vessel walls (8/15 cases) which helped in diagnosis of the disease. Wall thickness, surrounding tissue, appearance of the vessel and intraluminal thrombus could be well seen. Magnetic resonance imaging added more detail in multiple planes and could demonstrate vascular flow. High detection rate of the lesions (94.8%) was found for the aorta. The study was less sensitive for smaller vessels. Magnetic resonance angiography showed better correlation of the findings of brachiocephalic arteries compared to angiography. Subclavian steal syndrome could be diagnosed. For renal arteries, MR angiography could correctly demonstrate occlusion of renal artery in six out of eight cases. In the other two cases only stenoses of the vessels were found on angiograms. One renal arterial stenosis on MR angiography was confirmed by angiography. Conclusion: Takayasu arteritis could be found in Thailand. Clinical features were almost the same as in reports from other countries. Various forms of arterial involvement were demonstrated by imaging modalities. Angiography remained the best method for detection and diagnosis of Takayasu arteritis in correlation with clinical and laboratory findings. Although CT scan, magnetic resonance imaging and magnetic resonance angiography were limited and less sensitive for detection of the lesions, they were useful as noninvasive modalities showing more details of intraluminal clot, vascular wall and surrounding tissue which could be correlated with pathological findings and pathogenesis of the disease. Our study suggests that MR imaging and MR angiography can be screening and diagnostic techniques for patients with suspected Takayasu arteritis. Keywords: Takayasu arteritis; Angiography; CT scan; MR imaging; MR angiography • Corresponding author, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand. Fax.: +66 2 2548757. 0167-5273/96/$15.00 © 1996 Elsevier Science Ireland Ltd. All rights reserved PII SOI67-5273(96)02644-7

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N. Suwanwela, C. Piyachon I International Journal of Cardiology 54 Suppl. (1996) SJOI-SI18

1. Introduction Takayasu arteritis, a primary non-specific inflammatory disease of elastic arteries of unknown etiology, was once thought to be common only in Japan. Now it is known that the disease is worldwide in distribution and affects all races [1]. The incidence is said to be high in the Orient. It is our purpose to present the up-to-date data of this disease in Thailand.

2. Materials and methods Since our previous reports on Takayasu arteritis in Thailand in 1977 [2] and 1992 [3] more cases have been encountered. There are now 63 cases collected at Chulalongkom Hospital Medical School in Bangkok during 1971-1976 and 1985-1995 periods. The diagnosis of Takayasu arteritis was based on pathological findings after surgery or at postmortem examination in II patients. For the remaining patients, the diagnosis was established according to the clinical and angiographic findings. HLA typing was studied in the last cases and will be separately reported. Angiography was done in order to visualize the entire aorta and its major branches in all cases. CT scans, with pre- and post-administration of intravenous contrast were studied in 15 cases. Magnetic resonance imaging or MRI was carried out with a 1.5 T system (Signa, GE, USA) in 14 patients using spin-echo and gradient-echo techniques. Lately, magnetic resonance angiography or MR angiography was also performed in ten patients. The techniques of MR angiography for the aortic arch and branches were 3D time-of-flight using body coil and in some cases, 2D time-of-flight with anterior neck coil [4]. For subclavian arteries, 2D timeof-flight was used in sagittal plane. A technique of 2D time-of-flight with anterior neck coil was used for the neck vessels. For the abdominal aorta and renal arteries, the images were acquired with 3D phase-contrast MR angiography technique [5]. 3. Results 3.1. Age

The age distribution of the patients on admis-

sion was between 7 and 55 years and the prevalence was greatest in the third and fourth decades of life. Patients at the age of 40 and over in our series had a long history of illness for 10-20 years. 3.2. Sex

Among 63 patients, females were more frequently affected than males. There were 43 females and 20 males. The ratio of female to male was 2.15:1. All patients were Thai or Thai-Chinese origin. None of them were from the same family. 3.3. Clinical features

The clinical findings are summarized in Table 1. Hypertension was the most common finding, presented mainly with clinical symptoms of headache. Absence or weakness of pulses on the extremities, especially on the upper extremities was found in about half of the patients. Cerebrovascular disease with symptoms of weakness of the extremities, paralysis, vertigo, dizziness and syncope was the third common finding. Congestive heart failure was found in about 20% of the patients. Aortic regurgitation was presented in 6 out of 63 cases (9.5%). Other symptoms and signs such as visual disturbance, malaise, fever, weight loss, vascular bruit, abdominal mass and joint pain were found. 3.4. Laboratory findings

For blood tests, elevated erythrocyte sedimentation rate was present in 50% of the patients. Other tests such as VDRL, RA factor, Tuberculin test

Table I Clinical findings in Takayasu arteritis (63 cases) Findings

Cases

%

(n)

Hypertension Absence or weakness of pulses Cerebrovascular disease Congestive heart failure Aortic regurgitation Others

48 31

74.6 49.2

14

22.2 20.6 9.5 7.9

13

6 5

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Table 2 Summary of angiographic findings of vascular lesions in 63 pat ients with Takayasu arteritis Vessels

A 1. Aorta Ascending Arch Thoracic Abdominal

I 4 16

2. Branches of aortic arch Innominate Subclavian Rt . Lt. Common carotid Rt . Lt. Vertebral Rt. Lt.

5 5 2

5. Iliac artery

D

S

16 12 6 14

I I 12 20

2

6 16 7 5 6 6

5 9 1 2 5 4

2 4

8

2

5 6 3 7 7

I I

3. Visceral branches Celiac Superior mesenteric Inferior mesenteric 4. Renal artery

Total lesions

Findings

I 2 6

No .

%

17 19 41 86

4 4.4 9.6 20.2

6 24 37 17 14 12 II

1.4 5.6 8.7 4 3.3 2.8 2.5

13 4

13 19 10

4.4 2.3

II 13

44 35

10.5 8.2

10 9

2.3 2. 1

5 19 34

I

2 4

II

21

Lt.

2

4

IS

Rt . Rt.

3

3 4

3 4

Rt.

0

3

A, aneurysm; 0 , dilatation ; S, stenosis; 0 , occlusion ; I, irregular contour; Rt ., right; Lt., left.

Fig. I. Coronary angiograms in two patients. (a) Long stenotic segment of the left anterior descend ing branch in a 42-year-old male without symptoms and signs of coronary heart disease. (b) Segmental narrowing of two branches of the anterior descending coronary artery in another patient with chest discomfort.

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N. Suwanwela, C. Piyachon I International Journal of Cardiology 54 Suppl. (1996) SJ01-S118 New Clossincction of Angiogram in Takoyasu Arteritis Takoyasu Conference

In

1994

ij[j'~~~%

Type

AXhXA\/\ I

lIa

c(-) +

C(+) + P(+)

+

P(-)

+

JIb

JlI

N

V

c:

involved coronary ortery

P

involved pulmonary artery

Fig. 2. New classification of angiogram in Takayasu arteritis (International Conferences on Takayasu arteritis, Tokyo, 1994)

and C-reactive protein did not show any specificity. 3.5. Angiographic findings

The site frequencies and various forms of aortal and arterial involvement in Takayasu arteritis ranging from irregular contour, stenosis, occlusion, dilatation of the vessels and aneurysm are shown in Table 2. The most common vessel affected was the abdominal aorta, representing

Table 3 Involvement of vessels in Takayasu arteritis. Classification from International Conferences on Takayasu arteritis 1994;(63 cases) Cases

%

(n)

Type I Type IIa Type lIb Type III Type IV Type V

0 0 7

2 12 42"

0 0 11.1 3.2 19 66.7

Coronary angiography 8 cases (negative 6), (positive 2"); Pulmonary angiography 8 cases (negative 8) positive zero. "Same case.

20.2% of all lesions. The second most common sites were the renal arteries (18.7%). Both subclavian arteries were the third most commonly involved vessels (14.3%). The common carotid arteries were involved more frequently than the vertebral arteries. Coronary and pulmonary angiographies were studied in the last eight cases. Among these patients, 2 (25%) showed coronary arterial involvement. One patient had a long stenotic lesion in one vessel. Another patient had multiple lesions in two vessels (Fig. I). These two patients also had extensive involvement of the aorta and branches.

Fig. 3. CT scan showing calcification of the aortic wall (arrow head) and left renal artery (R) in a 28-year-old female. Angiogram is shown in Fig. 12.

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Fig. 4. Thrombus in an aortic arch aneurysm. (a) cr scan , thrombus is seen as filling defect (2] in enhanced scan . (b) Arch aortogram of the same case shows only the contrast filled lumen. (c) MR image in coronal plane shows the whole aneurysm , lumen, thrombus (A), wall, and surrounding tissue.

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Among the eight patients who underwent pulmonary angiography, no patient had pulmonary arterial involvement. 3.6. Classification of angiogram in Takayasu arteritis

According to the new classification established from the International Conferences on Takayasuarteritis in 1994(Fig. 2), 63 patients were classified based on angiographic findings (Table 3). The most common type (66.7%) was type V (entire aorta and branches). The second, third and fourth most common findings were type IV (abdominal aorta and branches) 19%, type lIb (ascending aorta, arch, thoracic aorta and branches of aortic arch) Il.l% and type III (thoraco-abdominal aorta and branches) 3.2%. No patient was found to have only involvement of the brachiocephalic branches (type I) or ascending aorta and brachiocephalic branches (type IIa). Two patients with involvement of the coronary arteries were in type V category. 3.7. Findings on computed tomography

Plain and enhanced CT scans were studied in IS patients. Calcification, appearance of the vessels, clot in the lumen, wall thickness and dissection of the wall were demonstrated. Calcification was found in eight cases while it was seen on plain roentgenogram of chest and abdomen in three cases. In most of the cases calcification was found in the aorta. In two cases, calcification was also seen in the renal arteries (Fig. 3). Stenosis and aneurysms of the aorta were found corresponding with the angiograms. More details for intraluminal clots and the lumen were demonstrated (Fig. 4). Dissection of the aortic wall was seen in one case. 3.8. Findings on Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA)

The findings on MRI performed in 14 patients were interpreted and compared with previous knowledge of angiographic findings of the aorta, branches of the aortic arch and branches of the abdominal aorta (Table 4). The appearance of the

large vessels such as dilatation, stenosis, occlusion, irregularity, aneurysm and wall thickness could be well seen in multiple planes (Fig. 5). Flow and clot could be demonstrated in aneurysm and aorta (Figs. 4, 6). Collateral circulation as an indirect sign of stenosis or occlusion was detected (Fig. 7). In one case dissection of the aortic wall was demonstrated. Aortic regurgitation was depicted by cine MR images with gradient-echo technique in one patient. MR angiography in ten cases added more information. These were done for the aortic arch, proximal brachiocephalic arteries and the renal arteries. The findings were compared to angiographic findings (Table 5). For the brachiocephalic arteries, the findings corresponded well with the angiograms (Fig. 8). In one patient, moderate stenosis of the subclavian artery was overestimated on MR angiogram (Fig. 9). In addition, flow in subclavian steal syndrome could be detected in four cases (Fig. 10) using twodimensional time-of-flight (2D TOF MRA) with different superior and inferior saturation pulses [6]. For visualization of renal arteries, phasecontrast magnetic resonance angiography was performed. Occlusion of the renal artery and renal artery stenosis in the proximal parts were demonstrated (Figs. II, 12). In two patients, severe stenosis of the renal arteries on angiograms was seen as occlusion on MR angiograms.

3.9. Treatment

In the majority of cases, medical treatments for hypertension, congestive heart failure, cerebrovascular disease and other symptoms were given. Corticosteroid and immunosuppressive drugs were also used. Percutaneous transluminal angioplasty has been performed in five patients. Dilatation has included five renal arteries and one left subclavian artery. All dilatations were with immediate improvement of the stenosis. Surgical procedures were done in 13 patients, including bypass surgery and grafts in seven, autorenal transplant in three, nephrectomy in two, and renal artery endaterectomy in one. In one patient a second operation was performed following aorta-aorta bypass graft occlusion. This patient

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Table 4 Summary of MRI and angiographic findings in patients with Takayasu arteritis (14 cases) MRI

Vessels

A

Angiography

0

S

0

Total lesions

A

0

S

0

Total lesions

I. Aorta Ascending Arch Thoracic Abdominal

6 I 4 2

3 5 5

3 2 5

6 7 12 12

6 I 4 2

3 5 5

3 4 5

6 7 14 12

Total lesions

13

13

10

37

13

13

12

39

2. Branches of aortic arch Innominate Subclavian Rt. Lt. Common carotid Rt. Lt. Rt. Vertebral Lt.

0 0 0 I

9

2

3. Visceral branches Celiac Superior mesenteric Inferior mesenteric 4. Renal artery

Rt. Lt.

5. Iliac artery

Rt. Lt.

Total lesions

I 4 9 3 I

I 5 I

2 2

Total lesions

2 3 2 I

4 2

8

2

20

I I 2

I 2 2

2 3

7 6 I 3

2

2

3

7

10

2

22

A, aneurysm; 0, dilatation; S, stenosis; 0, occlusion; I, irregular contour; Rt., right; Lt., left; MRI, magnetic resonance imaging.

died from reptured aortic aneurysm occuring below the graft.

India [8], 1.7:I in Israel [9], 2.9: I in China [10], 4.4:1 and 6.6:1 in Korea [11,12], 6.3:1 in Mexico [13],8:1,9.4:1 and 24.2:1 in Japan [14,15]. How-

4. Discussion

ever, in all reports, preponderance of females in Takayasu arteritis was evident. Regarding the age distribution, the youngest patient was 7 years old and the oldest patient was 55 years old. All patients aged over 40 years of age had a long history of illness for 10-20 years. The onset of the disease might be started quite earlier. The most common age groups in our study were in the third and fourth decades, which were almost

Since Takayasu arteritis was first reported in Thailand in 1967 [7] more cases have been diagnosed. Females were more affected than males, the ratio was now changed from 1.88: I in our previous report [3] to 2.15: I in this series. There is a wide range of female to male ratio in reports from various countries such as 1.6:1 in

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Fig. 5. MR images. (a) Fusiform dilatation of the abdominal aorta in coronal plane comparing to aortogram (b). (c) Sagittal plane MR image in another patient showing dilatation of the ascending aorta, stenosis and dilatation of the thoracic aorta in a 27-year-old female.

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Fig. 6. (a) MR image shows high signal intensity representing slow flow in the thoracic aorta on spin-echo Tt-weighted image above the stenosis (arrow). Aortogram of the same patient shows only stenosis and irregularity of the aorta (b).

the same as in reports from other countries [8,1O-14J. For the laboratory findings, elevated erythrocyte sedimentation rate was considered to be one of the guidelines for making clinical diagnosis of Takayasu arteritis [IJ. It was found to be elevated in 50% of our patients. The incidences in Japan, India, Korea were 72%, 66%, and 37-60010, respectively [8,11,12,14J. In Japan, patients were treated with adrenocorticosteroid when they revealed evidence of active arteritis which includes accelerated erythrocyte sedimentation rate [16J. There was no definite significant correlation with positive tuberculin reaction in our patients. Many previous authors have reported high positive rate of tuberculin reaction in patients with Takayasu arteritis [8,11,13,14,17-21]. On the other hand, many reports did not show any high

frequency of positive tuberculin test in these patients [22,23J. For clinical symptoms and signs, the most common findings in our series was hypertension (74.6%) followed by absence or weakness of pulses (49.2%). About one fourth of the patients had cerebrovascular symptoms and signs. Congestive heart failure was quite common in about one fifth of the patients. Aortic regurgitation was present in six out of 63 cases. Doppler echocardiography and cine MR images with gradient-echo technique were helpful in diagnosis of aortic regurgitation. Other clinical features including visual disturbances, joint symptoms and abdominal mass were observed. These features were about the same as in other reports [8,10,12,13,15J and correlated well with the angiographic findings. Total aortography was an important investiga-

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Fig. 7. (a) MR image of an lS-year-old male showing collateral vessels (co) resulting from occlusion of the left renal artery (L). Occlusion of the right renal artery (R) is also seen. (b) Angiogram of the same patient demonstrates the same findings.

tion to confirm the diagnosis of Takayasu arteritis, since most of the patients did not have pathological specimens. The exact appearance and extent of vascular involvement could be demonstrated. More attention has been paid to coronary and pulmonary arteries because of these vesselsare frequently involved in Takayasu arteritis [24-28]. Angiographic findings were previously classified according to the extension of involvement by many authors including Ueno [29], and Nasu [30]. The new classification following the Tokyo International Conferences on Takayasu arteritis in 1994 was used in this study. This new classification will help to classify the angiographic findings in more detail including involvement of the pulmonary and coronary arteries. In this study, the most common angiographic findings were in type V which was the most extensive involvement. These findings were the same as in India, Mexico, Korea, and China, [8,10,12,13]. The second most common involvement was type IV. The majority of our patients (88.9% of cases) had involvement of the abdominal aorta (type III 3.2%, type IV 19%, type V 66.7%). No patient was found to be classified in type I or type IIa which was different from studies in Japan where the aortic arch and branches were much more involved [14,15,31]. Among the major branches of the aorta, the renal arteries were the most commonly involved (18.7%) in our series which was the same as in India and Israel [8,9]. In Japan, Korea, and China the subclavian arteries were more frequently involved [10,12,31]. However, for patients with hypertension from the study in Korea more renal arteries were involved [II]. In our study, dilatation of the ascending aorta was quite common and was the same as reported by others [32,33]. Aneurysm and dilatation of the aortic arch, thoracic and abdominal aorta were also commonly found. Of the total 424 lesions found in aortography of our 63 cases, stenosis of the arteries was the most common finding. Coronary angiographies were studied in eight cases and involvement of the coronary arteries was found in two cases. Long stenotic and multiple stenotic lesions were found. According to Matsubara [24], these were classified as type II (diffuse or focal coronary arteritis). The proximal and

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Table 5 Summary of MRA and angiographic findings in patients with Takayasu arteritis (ten cases)

A

Innominate Subclavian

Rt. Lt. Common carotid Rt. Lt. Rt. Vertebral Lt. Total lesions Renal

Total lesions

Angiography

MRA

Vessels

D

S

3 I I I I

Total lesions

A

D

S

I 2

I 2

3 I

6

I 2

3 3

3 I I I I

7 5 3

18

10

5

8

I 2

10

Rt. Lt.

0

2 I

0

Total lesions

I 2 3 I

6

2 I

I 2

3 3

4

7 3 3

18

2 I

9

3

6

9

5 4

A, aneurysm; D, dilatation; S, stenosis; 0, occlusion;I, irregular contour; Rt., right; Lt.,left; MRA, magnetic resonance angiography.

distal segments of the comary arteries were involved. One of these two patients had chest discomfort. The other patient did not have typical symptoms of coronary arterial involvement. The incidence of coronary involvement in previous reports was 9-25% [12,34,35J. Prospective study of coronary artery should be done since we know now that coronary artery can also be involved in this disease. Coronary angioplasty could help to relieve the ischemic symptom. For the pulmonary vessels, angiographies were done in eight cases. No pulmonary involvement was observed. Lung perfusion scans with Tc-99m human serum albumin were done in another two cases and were negative. In other studies, pulmonary arterial involvement in Takayasu arteritis was not uncommon [I0,12,24,31,34,36J. The pathohistologic characters of the pulmonary artery were similar to those of the systemic artery. Stenosisrecanalization, so-called blood vessels-in-blood vessels were found and these were not observed in the systemic arteries [25J. The changes in pulmonary artery causing pulmonary hypertension could cause morbidity and long-term mortality in this disease.

Computed tomography or CT scan is now available and widely used. For Takayasu arteritis, this will add more information. Calcification could be identified in eight out of 15 patients studied by CT scan. It was helpful in the diagnosis of Takayasu arteritis. The appearance of the vessels such as stenosis, dilatation, aneurysm and intraluminal clots could be seen and confirmed by angiography in all cases. In one case, dissection of the aorta was demonstrated which could be a complication from cathetherization for angiography. Aneurysm and hematoma related to vascular rupture were also reported on CT scan [37,38J. The thickness of the aortic wall can be measured by a better technique of CT scan. Some authors were using this method for diagnosis and follow-up studies following steroid therapy [39J. Spiral CT angiography will improve the visualization of the blood vessels by three dimensional reconstruction of the arteries in multiple planes [4OJ. This procedure will be useful in the diagnosis of the disease and planning for surgery. Relationship to the adjacent structures and blood vessels can be assessed. Dynamic spiral CT scan can be used to show serial enhancement of the

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B

s

aortic wall which will be useful to correlate with pathological findings and pathogenesis of the disease in the wall [41]. Magnetic Resonance Imaging or MRI is a noninvasive modality to visualize the vessels. Fourteen cases of Takayasu arteritis were studied . Abnormalities of the arteries were demonstrated in different planes. In addition, flow, clot, wall thickening, dissection and collateral circulation could be demonstrated. Aortic regurgitation was clearly seen in cine MR. MRI was found to be most useful in detection of the abnormalities of the aorta. The detection rate comparing to angiography was 94.8% (37/39 lesions). It was less sensitive for smaller arteries. Only two out of20 various forms of the lesions at branches of the aortic arch were seen and only two out of 22 lesions of branches of the abdominal aorta were demonstrated. The pulmonary arteries could be well visualized. For the aorta, apart from the appearance of the vessels, abnormal flow in the aorta could be evaluated. Slow flow was found to be of high signal intensity on spin-echo images. It was sometimes difficult to discriminate intraluminal thrombus from slow flow. However, several techniques may be used to avoid this potential pitfall. In aneurysm, clot and flow in the residual lumen could be evaluated as well as the total aneurysm, the wall and tissues external to the aneurysm. These were similar to CT findings in axial planes. However, MRI could demonstrate more detail in sagittal and coronal planes and no contrast was used. These are advantages above angiography in which only the contrast filled lumens could be demonstrated. The difficulty on MRI study is we need to image the vessel at multiple different levels in one plane in order to visualize the whole vessel. Tortuosity of the vessels and lordosis of the spine cause more difficulty to visualize the whole vessel in one image and also cause difficulty in the diagnosis of vascular abnormality. Yamada Fig. 8. (a) Occlusion of the left subclavian artery with collateral vessels(arrow head) and occlusion of the right common carotid artery on MR angiogram, 3DTOF. (b) Arch aortogram shows the same findings. (c) MR angiogram of neck vessels, 2DTO F. also shows non-visualization of the right common carotid artery. B. brachiocephalic artery; Y, vertebral arte ry; C, common carotid artery ; S, left subclavian artery .

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Fig. 9. Stenosis of the right subclavian artery. (a) MR angiogram.. long stenotic lesion is seen (arrow head). (b) Only short stenotic segment is demonstrated on angiogram. C, right common carotid artery.

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Fig. 10. Occlusion of the left subclavian artery with subclavian steal syndrome. (a) MR image shows presence of signal void left vertebral artery (L). However, on MR angiogram with superior saturation pulse, the left vertebral artery is not seen (b). (c) MR angiogram with inferior saturation pulse shows the left vertebral artery (L) and the left subclavian artery (8) indicating reverse flow.

[42] concluded that MRI can clearly depict lesions of the aorta, proximal branches and pulmonary arteries but distal lesions were often not as clear. Recently, magnetic resonance angiography or MR angiography of the aortic arch, brachiocephalic arteries and renal arteries was performed in ten patients of Takayasu arteritis. In general, the origins of the carotid and vertebral arteries are not seen in routine cervical MR angiography using anterior neck or head coils in most patients [43]. With the techniques for aortic arch, using 3D timeof-flight and body coil, the origins and proximal branches could be clearly demonstrated. The findings correlated well with the angiographic findings. In one case, two separate stenotic lesions of

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Fig. II . (a) MR angiogram of renal arteries of a 19-year-old female showing stenosis of the right renal artery (arrow head) . (b) The same finding is demonstrated on aortogram (arrow head) .

the proximal left common carotid artery were seen on MR angiogram and confirmed by angiography. Subclavian steal was clearly demonstrated in four patients . The technique of inferior saturation pulse

was helpful in demonstrating the retrograde flow in the vertebral arteries. These patients did not have neurological deficit. For the subclavian arteries, 20 time-of-flight

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Fig. 12. Occlusion and dilatation of the proximal left renal artery (L), same case in Fig. 3. (a) MR angiogram. (b) Aortogram of the same patient. The right renal artery (R) is normal.

technique was used in sagittal plane. In most cases, there was good correlation with the angiographic findings. However, moderate stenosis of the subclavian artery was overestimated by MR angiography in one patient owing to loss of laminar flow and resultant intravoxel dephasing. Although MR angiography has been successful in evaluation of circulation in the head and neck, subclavian artery imaging is quite difficult because of artifacts from cardiac, respiratory motion and problems with stationary tissue suppression. For renal arteries, MR angiograms of ten patients using 3D phase-contrast aquisition were obtained and compared to conventional angiograms. In eight lesions of renal artery occlusion on MR angiography, six lesions had the same findings on angiography. For the other two lesions, only stenoses of the renal arteries were seen on angiograms. One lesion of renal arterial stenosis on MR angiography was confirmed by angiography. Reports of MR angiography in evaluation of renal artery stenosis were varied according to various techniques. Kim [44], using time-of-flight

technique, reported an overall sensitivity of 100% and specificity of 94% for detection of stenosis greater than 50% in diameter for the proximal renal arteries. Other reports including Debatin et al. [45] showed higher sensitivity (87%) and the same specificity (97%) in detection of renal stenosis by using phase-contrast sequences than TOF (sensitivity 53%, specificity 97%). MR angiography has a number of inherent pitfalls. The distal renal arteries and intrarenal vessels are not adequately visualized by current MR angiography techniques. Overgrading of stenosis may occur due to intravoxel dephasing resulting from turbulence at a stenosis. Undergrading of the stenotic lesions is due to inadequate resolution of existing MR angiographic techniques. Further MR angiographic techniques are required to improve vascular resolution. Grist [46] suggested using MR angiography in patients with suspected renovascular hypertension only if the patient is allergic to contrast, has renal insufficiency, believed to be at substantial risk of renal hypertension and for the evaluation of suspected azotemic renovascular disease. The main advantages of MR

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angiography are that it is non-invasive and can be performed without ionizing hazard or intravascular contrast. MR angiography techniques are usually well torelated. Failed examinations result most frequently from patient motion.

s. Conclusion Takayasu arteritis is a worldwide disease and can be found in Thailand. These patients came to the hospital with various signs and symptoms. Diagnosis could be made if we are aware of this disease. In this study of 63 patients, the most common age group was in the third and fourth decades of life. Females were more frequently affected than males with a ratio of 2.15:1. Various forms and sites of arterial involvement were demonstrated by angiographic studies. Extensive involvement of the arteries was found in the majority of the patients. The most common site of vascular involvement was the abdominal aorta. Stenosis of the arteries was the most frequent finding. Angiography remained the best method for detection and diagnosis of Takayasu arteritis in correlation with clinical and laboratory findings. Although CT scan and MRI were limited and less sensitive for the detection of the lesions, they were useful as noninvasive modalities. CT scan was very sensitive in detection of calcification which helped in the diagnosis of the disease. The details of aneurysm and changes in the arterial wall were better evaluated by CT scan and MRI. Dynamic flow could be assessed by MRI and MR angiography. MR angiography also added more details which correlated well with angiograms for the neck vessels. However, there are still pitfalls in MR angiographic studies for subclavian and renal arteries. Further dynamic contrast study using spiral CT scan or magnetic resonance imaging technique will be useful in the evaluation of the vessel wall correlating with pathological findings and to study pathogenesis of this disease. References [I] Sekiguchi M, Suzuki J. An overview of Takayasu arteritis. Heart Vessels 1992;Suppl. 7:6-10. [2] Piyachon C. Takayasu arteritis in Thailand. Aust Radiol 1977;21:350-361.

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