Multidetector helical angio CT oblique reconstructions orthogonal to internal carotid artery for preoperative evaluation of stenosis. A prospective study of comparison with color Doppler US, digital subtraction angiography and intraoperative data.
OBJECTIVE
The recent introduction to clinical practice of multidetector helical angio CT (MHACT) has generated a new interest in the diagnosis of carotid artery atherosclerosis. In recent years there has been a redefinition of the indications to carotid artery endarterectomy; there is a tendency to appraise plaque morphology and composition, and not only stenosis degree. The aim of this prospective study is to analyze the validity of MHACT in the diagnosis of atheromasic stenosis of the carotid bifurcation, in comparison with US color Doppler (USCD), digital subtraction angiography (DSA) and intraoperative evidence (OP). Special emphasis is given to the analysis of plaque composition and to precise evaluation of the stenosis percentage computed as an area rate on oblique reconstructions performed exactly orthogonal to the axis of the vessel at the point of maximal stenosis.


METHODS
Twenty-seven carotid stenosis (in 24 patients) were preoperatively evaluated by USCD, MHACT, DSA. We calculated the stenosis degree with USCD, by the ECST method, both as a diameter rate and as a bidimensional value. By MHACT we computed the percentage of stenosis as an area rate, in an MPR oblique plane orthogonal to the vessel axis, at the point of maximal stenosis; by DSA we used NASCET and the common carotid artery method (CC). DSA measurements have been mathematically converted as area rate (NASCET2 and CC2). All the patients were operated on with the eversion technique (EEA); it was always possible to obtain an intact cylindrical specimen of the plaque and to perform a reliable and accurate evaluation of the degree of stenosis by sectioning and measuring it on the desk. We gave a score to the presence and amount of lipid and calcium components, and these data were compared to those obtained with the different diagnostic instruments.


RESULTS
Statistical analysis of the 7 data sets showed an important underestimate of the angiographical method (DSA), even if the measurements were carried on by a precision caliper. The mathematical conversion of a linear stenosis rate into an area rate gives these values more reliability, indicating, as for NASCET2, non statistically significant differences when compared to surgical evidence, notwithstanding a high standard deviation. The rates obtained by USCD (area rate) and MHACT proved to be very accurate with respect to surgical evidence. In this study there was no significant difference in the detection of various components (lipid and calcium) of the atheromasic lesion, by MHACT and surgical evidence (OP).


CONCLUSIONS
MHACT promises to be a very accurate instrument in the detection of plaque components and identification of the stenosis degree. It shows some limits in very calcific lesions and occasionally, in relevant cardiac failure, may be useless. Hence one feels the need to reassess the role of DSA, once considered the "gold standard", with more extensive prospective studies, including comparison with MHACT and USCD.
De Monti
M
M
Cardionephrovascular Department, San Paolo University Hospital, Milan, Italy. marco.demonti@tin.it
Ghilardi
G
G
Caverni
L
L
Ceriani
L
L
Soldi
S
S
Massaro
F
F
Buchbut
R
R
Gobatti
D
D
Scorza
R
R
D015901:Angiography, Digital Subtraction; D001161:Arteriosclerosis / Q000000981:diagnostic imaging* / Q000601:surgery; D002114:Calcinosis / Q000000981:diagnostic imaging; D002118:Calcium / Q000032:analysis; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D016893:Carotid Stenosis / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007432:Intraoperative Period; D008055:Lipids / Q000032:analysis; D011237:Predictive Value of Tests; D011300:Preoperative Care / Q000379:methods; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed / Q000295:instrumentation; D018615:Ultrasonography, Doppler, Color
D008055:Lipids; D002118:Calcium