| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Letters to the Editor |
Department of Radiology, A. Gemelli Hospital, Catholic University of Sacred Heart, 1 A. Gemelli, 00168, Rome, Italy
e-mail: alescina{at}tin.it
I read with great interest the article by Dr Ouwendijk and colleagues, published in the September issue of Radiology (1), regarding a randomized controlled trial comparing contrast material–enhanced magnetic resonance (MR) angiography and multidetector computed tomographic (CT) angiography for imaging peripheral arterial disease (PAD). To my knowledge, this article represents the first published study results about the comparison of CT angiography versus MR angiography for PAD.
In the past, the diagnostic work-up in patients with PAD was based on a first-line noninvasive evaluation (Doppler sonography, ankle-brachial index, treadmill test) and on transcatheter digital subtraction angiography, which represented at the same time both the second-line examination necessary to select and plan the adequate treatment and the established reference standard. Recently, peripheral CT and MR angiography have been shown to be robust techniques able to provide a precise road map for treatment, thus replacing diagnostic digital subtraction angiography in most institutions.
Both CT angiography and MR angiography have relative and absolute contraindications; however, these techniques could be employed indifferently in most patients with PAD. Dr Ouwendijk and colleagues in their article conclude that CT angiography has some advantages over MR angiography because of the higher diagnostic costs of MR angiography; however, they have not demonstrated significant differences in clinical utility and patient outcomes.
The clinical stage in patients often corresponds to different localizations of the disease (2): Patients with claudication had steno-occlusive disease in the iliofemoral district more frequently, while the involvement of distal vessels (prevalent or associated with the proximal ones) is more frequently observed in patients with critical ischemia. Some studies have demonstrated that diagnostic performance for CT angiography and MR angiography is not constant along the segments of the peripheral arterial tree (3,4).
On the basis of these considerations, it would be interesting to analyze the results of Dr Ouwendijk and colleagues by stratifying patients according to clinical characteristics at presentation to highlight if in subgroups of subjects (ie, patients with claudication vs patients with critical limb ischemia), significant differences between CT angiography and MR angiography for diagnostic confidence and outcome can be found. Such differences, if demonstrated, may justify a preferential indication for CT angiography or MR angiography in the future according to the clinical presentation. However, in their study, Dr Ouwendijk and colleagues employed some clinical indexes of peripheral vascular disease, such as ankle-brachial index, maximum walking distance, and criteria according to Rutherford (5), mainly to report significant changes from baseline to follow-up rather than to stratify patients. Since the presence and degree of stenosis in each arterial segment was assessed in the study, a retrospective analysis to compare patients with proximal and distal lesions should also be possible.
I believe it may be very interesting for many readers to know if the authors have already performed or will perform such analyses and to know the eventual results.
 |
References |
|---|
 TOP References REFERENCE |
|---|
Department of Radiology, Erasmus MC Rotterdam, Dr Molewaterplein 50, Room 21-18, 3015 GE Rotterdam, the Netherlands
e-mail: m.hunink{at}erasmusmc.nl
Dr Cina suggests that we perform a subgroup analysis (patients with claudication vs patients with critical ischemia) to see if there are significant differences in outcomes between these subgroups.
Although interesting to explore, subgroup analysis was not warranted with our study sample size (1). According to our sample size calculation, we needed at least 66 patients per strategy to demonstrate a significant difference between the strategy costs of MR angiography and the strategy costs of CT angiography. Thus, for a subgroup analysis (claudication vs critical ischemia) we need at least 66 patients with critical ischemia per strategy. As stated in table 1, this was not the case.
We did, however, analyze the differences between the groups adjusted for potentially predictive baseline characteristics, including severity of disease (claudication vs critical ischemia), with multivariable linear and logistic regression. In the multivariable analysis, the ß coefficient of disease severity indicates whether disease severity influences the outcome. The difference in outcome between MR angiography and CT angiography, adjusted for covariates such as disease severity, is, however, the result of interest. The ß coefficient of disease severity was not statistically significant for all outcome measures except for the therapeutic confidence. This means that disease severity has a significant influence on the difference in therapeutic confidence between MR angiography and CT angiography. However, the difference in therapeutic confidence between MR angiography and CT angiography, adjusted for covariates including disease severity, was not significant.
|
REFERENCE |
|---|
|
TOPReferencesREFERENCE |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| RADIOLOGY | RADIOGRAPHICS | RSNA JOURNALS ONLINE |
