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Detection of arterial intimal lesions: An experimental study comparing ultrasonography and arteriography
Eur J Vasc Surg 6, 62-66 (1992)
Detection of Arterial Intimal Lesions: an Experimental Study Comparing Ultrasonography and Arteriography L. Stam, I. Dawson, A. B. B. van Rijn, T. J. A. Kuipers and P. J. Breslau Department of Surgery, Bronovo Hospital, The Hague, The Netherlands In an experimental study the diagnostic value of intra-operative ultrasonography in the detection of arterial intimal lesions was investigated. A human carotid artery was placed in a pulsatile circuit with a roller pump and tubes. Intimal lesions (1-5 ram) were created and ultrasonography and biplane arteriography were performed. The ultrasonograms and arteriograms obtained were interpreted by three observers, who were blind to the procedures performed and the results were compared to the macroscopic defects. The mean sensitivity between observers for ultrasonography was 84% with a specificity of 95.7%. For biplane arteriography the mean sensitivity was 42 % with a specificity of 94.5%. The differences between ultrasonography and biplane arteriography were statistically significant (p < 0.02). It is concludedfrom this in vitro study that ultrasonography provides more accurate information concerning intimal lesions of the arterial wall than biplane arteriography. Key Words: Diagnosis of arterial wall lesions; Intra-operative ultrasonography; Intra-operative arteriography.
Introduction
Methods
Small defects of arterial anastomoses might lead to early graft thrombosis. 1 Detection of these lesions is therefore of great clinical importance. Intra-operative u l t r a s o n o g r a p h y is a relatively n e w diagnostic m e t h o d 2 and its value has not yet b e e n fully established in vascular surgery. Contrast arteriography has b e e n the "gold s t a n d a r d " for the detection of intimal lesions at the site of an anastomosis, 3 but some studies have suggested that intra-operative u l t r a s o n o g r a p h y could give more anatomical information about the anastomoses than arteriograp h y . 4'5 Furthermore, u l t r a s o n o g r a p h y is non-invasive and no X-rays or contrast are required. To assess reproducibility and resolution of ultras o n o g r a p h y , it was c o m p a r e d in this s t u d y with contrast arteriography in an in vitro experiment.
A pulsatile circuit was created b y a roller p u m p and the tubes filled with saline. A h u m a n carotid artery with slight atherosclerosis but w i t h o u t calcified plaques (n = 11) was placed in the circuit. The pressure in the pulsatile circuit was 110/40 m m H g with a f r e q u e n c y of 50-60 pulsations per min and a flow of 140 cc per rain. Small controlled lesions were created in the carotid artery. There were two groups: (1) sutured defects (SD) (n = 18), a piece of intima of rectangular shape and a length of 1-5 m m was cut from the arteries and subsequently sutured to the arterial wall with 6.0 n y l o n w i t h o u t an arteriotomy; (2) intimal flaps (IF) (n = 9) were created with a sharp h o o k e d needle and b y clamping the artery. In principle there is no difference b e t w e e n a s u t u r e d defect and an intimal flap, except that with a s u t u r e d defect it was possible to determine its exact size beforehand. Biplane contrast arteriography of the carotid artery segment was p e r f o r m e d (Fig. 1). Eminos (type 90/40) X-ray apparatus was used in combination with a M I N H film in a Kodak MIN-R
Please address all correspondence to: L. Stam, Department of Surgery, Catharina Hospital, Michelangelolaan2, 5602ZA Eindhoven, The Netherlands. 0950-821X/92/010062+05$03.00/0© 1992Grune & Stratton Ltd.
Detection of Arterial Intimal Lesions
63
Fig. 1. Arteriogram in one of two perpendicular directions. It shows two small defects in the contrast column (arrows). cassette. Thereafter, the part of the circuit with the carotid artery was placed in a basin filled with fluid for acoustic coupling. U l t r a s o n o g r a p h y was performed with a 7.5 M H z linear-array probe (Aloka Co., Ltd, SSD-280-LS). The artery was scanned in a longitudinal and transverse direction and the echo images photographed. Thereafter, the artery was d e t a c h e d from the circuit and o p e n e d on the contralateral side to the lesions in a longitudinal direction (Fig. 2). All lesions of the arterial wall were m e a s u r e d again and drawn schematically. Since an artery cannot be imaged by u l t r a s o n o g r a p h y over its entire length, the examination was split u p into several ultrasonograms and in total, 66 images obtained. The arteriograms were divided into c o r r e s p o n d i n g portions for comparison. The arteriograms and u l t r a s o u n d pictures were assessed by two experienced vascular surgeons and one vascular radiologist, w h o were blind to the procedures performed. Lesions were classified ,in four categories: (1) s m o o t h vessel wall, no lesion visible; (2) irregularity of vessel wall, possible lesion; (3) a certain, but small lesion occupying less than 20% of the vessel diameter; and (4) a definite lesion (Figs 3 and 4). Every observer d r e w the lesion, if present, on an outline of the artery and gave a n u m b e r according to the classification m e n t i o n e d above.
(
0
(L)
(
0
(2)
(5)
(4) Fig. 3. Drawing of the classification. (1) Smooth vessel wall, no lesion visible; (2) irregularity of vessel wall, possible lesion; (3) small lesion less than 20% of the vessel wall; (4) a definite lesion.
(1)
Fig. 2. A piece of intima (2mm) was sutured to the arterial wall (arrow). After arteriography and ultrasonography the artery was opened longitudinally to inspect the lesion.
(3)
(2)
(4)
Fig. 4. Composition of ultrasonograms showing the used classification. Eur J Vasc Surg Vol 6, January 1992
64
L. Stam et aL
Interobserver agreement was measured by kappa, 6 which is an observed agreement not accounted for by chance, divided by the potential agreement not accounted for by chance. Like a correlation coefficient, kappa varies from - 1 . 0 (complete disagreement) through 0 (chance agreement) to +1.0 (perfect agreement). The degree of agreement between the observers was tested for two definite types of lesions: no lesion visible or doubtful (categories 1 and 2) v s . definite small or large lesions (categories 3 and 4). In this way 2 x 2 tables were obtained and kappa, sensitivity and specificity were calculated. The differences between arteriography and ultrasonography were calculated by the McNemar chi-squared test.
Results
There were 66 segments assessed by three observers and 27 segments contained a lesion. The highest false positive results for ultrasonograms were 3/39 and for arteriograms 2/39 (Table 1). The false negative results for ultrasonography varied between 1/27 and 9/27, depending on the observer. The false negative results were high for arteriography with 10/27 to 23/27 in single arteriograms and 8/27 to 22/27 for biplane arteriograms. The interobserver agreement expressed as kappa was good with 0.61-0.78 for ultrasonography. The interobserver agreement for arteriograms however showed a wide range from 0.37 to 0.63, with a mean of 0.44 (Table 2). The percentages of sensitivity and specificity of the three observers are shown in Table 3. The sensitivity for ultrasonography ranges from 67.0-96.3% and the specificity from 89.7 to 100%. For biplanar arteriography the sensitivity ranged from 22.2 to 70.3% and the specificity from 86.2 to 100%.
Table 2. Interobserver agreement expressed in kappa Ultrasonogram
Arteriogram 1
Arteriogram 2
Observer 1/2
0.78
0.37
0.63
Observer 2/3
0.61
0.40
0.41
Observer 1/3
0.70
0.43
0.44
The differences between ultrasonography and arteriography in the detection of small lesions are statistically significant in favour of ultrasonography. The pvalue ranges from 0.02 for one observer to 0.005 and 0.003 for the other two observers. I f we consider the sutured defects (n = 18), it shows that by ultrasonography two observers were able to detect 94% of the lesions accurately but with biplanar arteriography only 33% of the lesions were correctly diagnosed. The other lesions (n = 9) were also correctly identified in 94% by ultrasonography but biplanar arteriography only detected 37.5% of them. In transverse section 23 of 27 lesions were photographed during ultrasonography and 93% of these were correctly recognised by two observers, with 87% for the third observer.
Discussion
In a simple experiment the value of ultrasonography in the detection of small arterial intimal lesions was studied. These intimal lesions can develop during the performance of an anastomosis and by clamping the artery. As contrast arteriography is considered the "gold standard" for the detection of arterial wall defects, it was compared with ultrasonography. The results show a highly significant difference
Table 1. Results of interpretation of ultrasonograms and arteriograms (angiogram 1 + 2, means biplane angiography)
A. False positive results in 39 segments Ultrasonogram Observer 1 1
Arteriogram 1 + 2 2
Observer 2
3
1
Observer 3
0
0
B. False negative results in 27 segments Ultrasonogram Observer 1 1
Arteriograml 10
Arteriogram2 14
Arteriograml + 2 8
Observer 2
3
22
23
22
Observer 3
9
20
22
19
Eur J Vasc Surg Vol 6, January 1992
Detection of Arterial Intimal Lesions
65
Table 3. Percentages of sensitivity and specificity of the three observers for ultrasonograms and arteriograms in one direction (1), the perpendicular (2) and both directions
Ultrasonogram (%) Observer I
Arteriogram 1 (%)
Arteriogram 2 (%)
Arteriogram 1 + 2 (%)
Sens. 96.3
62.9
48.1
70.4
Spec. 97.4
92.3
94.8
86.2
p<0.016 Observer 2
Sens. 88.8
18.5
Spec. 89.7
97.4
14.8
22.2
100
97.4
p < 0.0026 Observer 3
Sens. 67.0 Spec. 100
25.9
18.5
100
33.3
100
100
p < 0.0046
Fig. 5. Ultrasonogram in transverse direction shows a sutured defect of the arterial wall. between both m e t h o d s in favour of ultrasonography, p < 0.02. A difference which is s u p p o r t e d by the good kappa values, 0.61-0.78, for the interobserver agreement in the assessment of ultrasonograms. It was also possible using u l t r a s o u n d to visualise a lesion in transverse section (Fig. 5), which gives i m p o r t a n t additional information about the size of a lesion and the degree of stenosis. In transverse section 87% of the lesions were correctly recognised. If we consider that the observers scored on pictures of the images and lacked the real-time component of ultrasonography, it is likely that the diagnostic reliability of u l t r a s o n o g r a p h y is e v e n better. Reviewing the literature, there is only one other study, p e r f o r m e d by Coelho et al., s but no information is given about interobserver variation, which has an important impact on the results. Ultrasound has several advantages and the images obtained were very reproducible. By scanning manoeuvres with the u l t r a s o u n d probe it is possible to depict a lesion very clearly. The high contrast between the echogenic arterial wall and blood, which is echolucent, makes it easy to recognise a p r o t r u d i n g intimal lesion. Also m o v e m e n t of the lesions in the
arterial wall, caused by flow and pulsation, make it easier to recognise lesions and measure their diameter. A limitation of u l t r a s o n o g r a p h y is that it requires a learning phase, before it can be p e r f o r m e d adequately. W h a t is the place of intra-operative ultrason o g r a p h y in reconstructive arterial surgery? O n the basis of this s t u d y u l t r a s o n o g r a p h y might be useful to visualise the a n a t o m y of the anastomoses and that part of the artery which was clamped. Used in this w a y u l t r a s o u n d could be quicker and safer than intraoperative arteriography which appears to be of limited value. 3 One exposure is often inadequate because of the difficulty in timing of the contrast injection and it is often not feasible to visualise the critical areas, which include both the reconstruction a n d the run-off of arteries. In this s t u d y biplane arteri o g r a p h y only detected 33-37.5% of small lesions (15 mm). The reason for this is the fact that an intimal
X-ray
[
X-ray
l Cassette
[
] Cassette
Fig. 6. Schematic representation of a contrast filled artery with an intimal lesion during arteriography. (a) The lesion will be visible on the arteriogram. (b) Superimposement of the contrast column impedes depiction of the intimal lesion. Eur J Vasc Surg Vol 6, January 1992
66
L. Stam et aL
flap is only seen if it is at the margin of the contrast column and if the contrast column is superimposed on the lesion, it is not recognisable (Fig. 6). The results of this study have shown that ultrasound is a valuable diagnostic method for the detection of small defects of the arterial wall. Ultrasound is significantly more sensitive than arteriography for the detection of intimal lesions. Furthermore it saves time and avoids exposure to X-rays. The results of our experimental study justify further investigation to confirm its value in reconstructive arterial surgery.
Acknowledgements We thank P. J. H. M. Kitslaar, M.D., and C. J. van der Linden, M.D., for their helpful remarks.
References t STEPTLL, FLINN R, et al. Technical defects as a cause of early graft failure after femorodistal bypass. Arch Surg 1987; 12: 599-604. 2 LANERJ. Intraoperative B-mode scanning. J Clin Ultrasound 1980; 8: 427-434. 3 COURBIERR, JAUSSERANJM, REGCIM. Detecting complications of direct arterial surgery. The role of intraoperative arteriography. Arch Surg 1977; 112: 1115-1118. 4 SIGEL B, MACHI J, ANDERSON KW, et al. Operative ultrasonic imaging of vascular defects. Semin Ultrasound CT MR 1985; 6: 85-91. 5 COELHOJCU, SIGELB, FLANIGANDP, et al. Detection of arterial defects by real-time ultrasound scanning during vascular surgery: an experimental study. J Surg Res 1980; 30: 535-543. 6 KORAN LM. The reliability of clinical methods, data and judgments. N Eng J Med 1975; 293: 642-646. 7 COE~HO JCU, SIGEL B, FLANIGANDP, et al. Arteriographic and ultrasonic evaluation of vascular clamp injuries using an in vitro human experimental model. Surg Gynecol Obstet 1982; 155: 506-512. 8 COELHO JCU, SIGEL B, FLANIGAN DP, et al. An experimental evaluation of arteriography and imaging ultrasonography in detecting arterial defects at operation. J Surg Res 1982; 32: 130-137. Accepted 7 May 1991
Eur J Vasc Surg Vol 6, January 1992
Detection of Arterial Intimal Lesions: an Experimental Study Comparing Ultrasonography and Arteriography L. Stam, I. Dawson, A. B. B. van Rijn, T. J. A. Kuipers and P. J. Breslau Department of Surgery, Bronovo Hospital, The Hague, The Netherlands In an experimental study the diagnostic value of intra-operative ultrasonography in the detection of arterial intimal lesions was investigated. A human carotid artery was placed in a pulsatile circuit with a roller pump and tubes. Intimal lesions (1-5 ram) were created and ultrasonography and biplane arteriography were performed. The ultrasonograms and arteriograms obtained were interpreted by three observers, who were blind to the procedures performed and the results were compared to the macroscopic defects. The mean sensitivity between observers for ultrasonography was 84% with a specificity of 95.7%. For biplane arteriography the mean sensitivity was 42 % with a specificity of 94.5%. The differences between ultrasonography and biplane arteriography were statistically significant (p < 0.02). It is concludedfrom this in vitro study that ultrasonography provides more accurate information concerning intimal lesions of the arterial wall than biplane arteriography. Key Words: Diagnosis of arterial wall lesions; Intra-operative ultrasonography; Intra-operative arteriography.
Introduction
Methods
Small defects of arterial anastomoses might lead to early graft thrombosis. 1 Detection of these lesions is therefore of great clinical importance. Intra-operative u l t r a s o n o g r a p h y is a relatively n e w diagnostic m e t h o d 2 and its value has not yet b e e n fully established in vascular surgery. Contrast arteriography has b e e n the "gold s t a n d a r d " for the detection of intimal lesions at the site of an anastomosis, 3 but some studies have suggested that intra-operative u l t r a s o n o g r a p h y could give more anatomical information about the anastomoses than arteriograp h y . 4'5 Furthermore, u l t r a s o n o g r a p h y is non-invasive and no X-rays or contrast are required. To assess reproducibility and resolution of ultras o n o g r a p h y , it was c o m p a r e d in this s t u d y with contrast arteriography in an in vitro experiment.
A pulsatile circuit was created b y a roller p u m p and the tubes filled with saline. A h u m a n carotid artery with slight atherosclerosis but w i t h o u t calcified plaques (n = 11) was placed in the circuit. The pressure in the pulsatile circuit was 110/40 m m H g with a f r e q u e n c y of 50-60 pulsations per min and a flow of 140 cc per rain. Small controlled lesions were created in the carotid artery. There were two groups: (1) sutured defects (SD) (n = 18), a piece of intima of rectangular shape and a length of 1-5 m m was cut from the arteries and subsequently sutured to the arterial wall with 6.0 n y l o n w i t h o u t an arteriotomy; (2) intimal flaps (IF) (n = 9) were created with a sharp h o o k e d needle and b y clamping the artery. In principle there is no difference b e t w e e n a s u t u r e d defect and an intimal flap, except that with a s u t u r e d defect it was possible to determine its exact size beforehand. Biplane contrast arteriography of the carotid artery segment was p e r f o r m e d (Fig. 1). Eminos (type 90/40) X-ray apparatus was used in combination with a M I N H film in a Kodak MIN-R
Please address all correspondence to: L. Stam, Department of Surgery, Catharina Hospital, Michelangelolaan2, 5602ZA Eindhoven, The Netherlands. 0950-821X/92/010062+05$03.00/0© 1992Grune & Stratton Ltd.
Detection of Arterial Intimal Lesions
63
Fig. 1. Arteriogram in one of two perpendicular directions. It shows two small defects in the contrast column (arrows). cassette. Thereafter, the part of the circuit with the carotid artery was placed in a basin filled with fluid for acoustic coupling. U l t r a s o n o g r a p h y was performed with a 7.5 M H z linear-array probe (Aloka Co., Ltd, SSD-280-LS). The artery was scanned in a longitudinal and transverse direction and the echo images photographed. Thereafter, the artery was d e t a c h e d from the circuit and o p e n e d on the contralateral side to the lesions in a longitudinal direction (Fig. 2). All lesions of the arterial wall were m e a s u r e d again and drawn schematically. Since an artery cannot be imaged by u l t r a s o n o g r a p h y over its entire length, the examination was split u p into several ultrasonograms and in total, 66 images obtained. The arteriograms were divided into c o r r e s p o n d i n g portions for comparison. The arteriograms and u l t r a s o u n d pictures were assessed by two experienced vascular surgeons and one vascular radiologist, w h o were blind to the procedures performed. Lesions were classified ,in four categories: (1) s m o o t h vessel wall, no lesion visible; (2) irregularity of vessel wall, possible lesion; (3) a certain, but small lesion occupying less than 20% of the vessel diameter; and (4) a definite lesion (Figs 3 and 4). Every observer d r e w the lesion, if present, on an outline of the artery and gave a n u m b e r according to the classification m e n t i o n e d above.
(
0
(L)
(
0
(2)
(5)
(4) Fig. 3. Drawing of the classification. (1) Smooth vessel wall, no lesion visible; (2) irregularity of vessel wall, possible lesion; (3) small lesion less than 20% of the vessel wall; (4) a definite lesion.
(1)
Fig. 2. A piece of intima (2mm) was sutured to the arterial wall (arrow). After arteriography and ultrasonography the artery was opened longitudinally to inspect the lesion.
(3)
(2)
(4)
Fig. 4. Composition of ultrasonograms showing the used classification. Eur J Vasc Surg Vol 6, January 1992
64
L. Stam et aL
Interobserver agreement was measured by kappa, 6 which is an observed agreement not accounted for by chance, divided by the potential agreement not accounted for by chance. Like a correlation coefficient, kappa varies from - 1 . 0 (complete disagreement) through 0 (chance agreement) to +1.0 (perfect agreement). The degree of agreement between the observers was tested for two definite types of lesions: no lesion visible or doubtful (categories 1 and 2) v s . definite small or large lesions (categories 3 and 4). In this way 2 x 2 tables were obtained and kappa, sensitivity and specificity were calculated. The differences between arteriography and ultrasonography were calculated by the McNemar chi-squared test.
Results
There were 66 segments assessed by three observers and 27 segments contained a lesion. The highest false positive results for ultrasonograms were 3/39 and for arteriograms 2/39 (Table 1). The false negative results for ultrasonography varied between 1/27 and 9/27, depending on the observer. The false negative results were high for arteriography with 10/27 to 23/27 in single arteriograms and 8/27 to 22/27 for biplane arteriograms. The interobserver agreement expressed as kappa was good with 0.61-0.78 for ultrasonography. The interobserver agreement for arteriograms however showed a wide range from 0.37 to 0.63, with a mean of 0.44 (Table 2). The percentages of sensitivity and specificity of the three observers are shown in Table 3. The sensitivity for ultrasonography ranges from 67.0-96.3% and the specificity from 89.7 to 100%. For biplanar arteriography the sensitivity ranged from 22.2 to 70.3% and the specificity from 86.2 to 100%.
Table 2. Interobserver agreement expressed in kappa Ultrasonogram
Arteriogram 1
Arteriogram 2
Observer 1/2
0.78
0.37
0.63
Observer 2/3
0.61
0.40
0.41
Observer 1/3
0.70
0.43
0.44
The differences between ultrasonography and arteriography in the detection of small lesions are statistically significant in favour of ultrasonography. The pvalue ranges from 0.02 for one observer to 0.005 and 0.003 for the other two observers. I f we consider the sutured defects (n = 18), it shows that by ultrasonography two observers were able to detect 94% of the lesions accurately but with biplanar arteriography only 33% of the lesions were correctly diagnosed. The other lesions (n = 9) were also correctly identified in 94% by ultrasonography but biplanar arteriography only detected 37.5% of them. In transverse section 23 of 27 lesions were photographed during ultrasonography and 93% of these were correctly recognised by two observers, with 87% for the third observer.
Discussion
In a simple experiment the value of ultrasonography in the detection of small arterial intimal lesions was studied. These intimal lesions can develop during the performance of an anastomosis and by clamping the artery. As contrast arteriography is considered the "gold standard" for the detection of arterial wall defects, it was compared with ultrasonography. The results show a highly significant difference
Table 1. Results of interpretation of ultrasonograms and arteriograms (angiogram 1 + 2, means biplane angiography)
A. False positive results in 39 segments Ultrasonogram Observer 1 1
Arteriogram 1 + 2 2
Observer 2
3
1
Observer 3
0
0
B. False negative results in 27 segments Ultrasonogram Observer 1 1
Arteriograml 10
Arteriogram2 14
Arteriograml + 2 8
Observer 2
3
22
23
22
Observer 3
9
20
22
19
Eur J Vasc Surg Vol 6, January 1992
Detection of Arterial Intimal Lesions
65
Table 3. Percentages of sensitivity and specificity of the three observers for ultrasonograms and arteriograms in one direction (1), the perpendicular (2) and both directions
Ultrasonogram (%) Observer I
Arteriogram 1 (%)
Arteriogram 2 (%)
Arteriogram 1 + 2 (%)
Sens. 96.3
62.9
48.1
70.4
Spec. 97.4
92.3
94.8
86.2
p<0.016 Observer 2
Sens. 88.8
18.5
Spec. 89.7
97.4
14.8
22.2
100
97.4
p < 0.0026 Observer 3
Sens. 67.0 Spec. 100
25.9
18.5
100
33.3
100
100
p < 0.0046
Fig. 5. Ultrasonogram in transverse direction shows a sutured defect of the arterial wall. between both m e t h o d s in favour of ultrasonography, p < 0.02. A difference which is s u p p o r t e d by the good kappa values, 0.61-0.78, for the interobserver agreement in the assessment of ultrasonograms. It was also possible using u l t r a s o u n d to visualise a lesion in transverse section (Fig. 5), which gives i m p o r t a n t additional information about the size of a lesion and the degree of stenosis. In transverse section 87% of the lesions were correctly recognised. If we consider that the observers scored on pictures of the images and lacked the real-time component of ultrasonography, it is likely that the diagnostic reliability of u l t r a s o n o g r a p h y is e v e n better. Reviewing the literature, there is only one other study, p e r f o r m e d by Coelho et al., s but no information is given about interobserver variation, which has an important impact on the results. Ultrasound has several advantages and the images obtained were very reproducible. By scanning manoeuvres with the u l t r a s o u n d probe it is possible to depict a lesion very clearly. The high contrast between the echogenic arterial wall and blood, which is echolucent, makes it easy to recognise a p r o t r u d i n g intimal lesion. Also m o v e m e n t of the lesions in the
arterial wall, caused by flow and pulsation, make it easier to recognise lesions and measure their diameter. A limitation of u l t r a s o n o g r a p h y is that it requires a learning phase, before it can be p e r f o r m e d adequately. W h a t is the place of intra-operative ultrason o g r a p h y in reconstructive arterial surgery? O n the basis of this s t u d y u l t r a s o n o g r a p h y might be useful to visualise the a n a t o m y of the anastomoses and that part of the artery which was clamped. Used in this w a y u l t r a s o u n d could be quicker and safer than intraoperative arteriography which appears to be of limited value. 3 One exposure is often inadequate because of the difficulty in timing of the contrast injection and it is often not feasible to visualise the critical areas, which include both the reconstruction a n d the run-off of arteries. In this s t u d y biplane arteri o g r a p h y only detected 33-37.5% of small lesions (15 mm). The reason for this is the fact that an intimal
X-ray
[
X-ray
l Cassette
[
] Cassette
Fig. 6. Schematic representation of a contrast filled artery with an intimal lesion during arteriography. (a) The lesion will be visible on the arteriogram. (b) Superimposement of the contrast column impedes depiction of the intimal lesion. Eur J Vasc Surg Vol 6, January 1992
66
L. Stam et aL
flap is only seen if it is at the margin of the contrast column and if the contrast column is superimposed on the lesion, it is not recognisable (Fig. 6). The results of this study have shown that ultrasound is a valuable diagnostic method for the detection of small defects of the arterial wall. Ultrasound is significantly more sensitive than arteriography for the detection of intimal lesions. Furthermore it saves time and avoids exposure to X-rays. The results of our experimental study justify further investigation to confirm its value in reconstructive arterial surgery.
Acknowledgements We thank P. J. H. M. Kitslaar, M.D., and C. J. van der Linden, M.D., for their helpful remarks.
References t STEPTLL, FLINN R, et al. Technical defects as a cause of early graft failure after femorodistal bypass. Arch Surg 1987; 12: 599-604. 2 LANERJ. Intraoperative B-mode scanning. J Clin Ultrasound 1980; 8: 427-434. 3 COURBIERR, JAUSSERANJM, REGCIM. Detecting complications of direct arterial surgery. The role of intraoperative arteriography. Arch Surg 1977; 112: 1115-1118. 4 SIGEL B, MACHI J, ANDERSON KW, et al. Operative ultrasonic imaging of vascular defects. Semin Ultrasound CT MR 1985; 6: 85-91. 5 COELHOJCU, SIGELB, FLANIGANDP, et al. Detection of arterial defects by real-time ultrasound scanning during vascular surgery: an experimental study. J Surg Res 1980; 30: 535-543. 6 KORAN LM. The reliability of clinical methods, data and judgments. N Eng J Med 1975; 293: 642-646. 7 COE~HO JCU, SIGEL B, FLANIGANDP, et al. Arteriographic and ultrasonic evaluation of vascular clamp injuries using an in vitro human experimental model. Surg Gynecol Obstet 1982; 155: 506-512. 8 COELHO JCU, SIGEL B, FLANIGAN DP, et al. An experimental evaluation of arteriography and imaging ultrasonography in detecting arterial defects at operation. J Surg Res 1982; 32: 130-137. Accepted 7 May 1991
Eur J Vasc Surg Vol 6, January 1992