Sir, in the online edition of the BDJ, Khosropanah et al. report (BDJ 2009; 207: E8) the results of an unusually designed study which assessed the efficacy of panoramic radiographs to detect carotid artery calcifications by determining the level of agreement between the radiographs and Doppler sonography (DS).1 The study design is odd and a reverse of usual clinical dental practice in that they referred for radiographs patients who had already had a physician obtained DS study. The authors determined that the level of agreement between the two imaging systems was weak and concluded that panoramic radiographs are not an accurate or reliable method for detecting carotid artery calcifications.

I am not surprised that there were numerous atheromas noted on DS that were not seen on the radiograph. This occurs in many patients because the imaging field of the panoramic radiograph frequently does not extend inferiorly enough to capture the individual's carotid artery bifurcation, and because the atheroma may not contain enough calcium for it to be evidenced on the radiograph.

Our group of researchers has published a study (identified by the authors but with inadequate detail) which more closely conforms to the real world practice of clinical dentistry and which determined the level of agreement between radiographs and DS.2 Specifically, we analysed the panoramic radiographs of 1,548 consecutively treated, neurologically asymptomatic dental patients who were 50 years or older. The radiographs of 65 patients (4.2%) showed at least one internal carotid artery (ICA) atheroma. Thirty-eight patients had bilateral lesions and 27 had unilateral lesions. DS evaluation of the 103 sides of the neck with a radiographically identified atheroma revealed that none of the ICAs were normal, 81 (79%) had less than 50% stenosis, 18 (17%) had 50 to 69% stenosis and four (4%) had 70% or greater stenosis. Four of the ICAs on the 27 sides without calcifications were deemed normal and 23 had less than 50% stenosis. These results substantiate the value of panoramic radiography, when used responsibly, to identify patients (15 [23%] of 65) with occult atheromas confirmed by DS as being haemodynamically significant (>50% levels of ICA stenosis) and categorising them at high risk of future stroke.

Dental and medical scientists when testing a hypothesis for validity should frame it such that it has clinical relevance. My research group which in 1981 was the first to observe atheromas on panoramic radiographs3 has steadfastly and adamantly stated in our 30+ publications that panoramic radiography is an inappropriate imaging system to screen patients for atheromas but should instead only be used to obtain images for dental need. Once obtained however these radiographs should then be comprehensively reviewed for evidence of atheromas. If and when an atheroma is noted on a radiograph, the patient should be referred to a physician for cardiovascular evaluation and possible confirmation of the atheroma by DS.

Lastly, the authors incorrectly stated that Ravon et al. in 20034 were the first to confirm by DS that the carotid-like calcifications seen on panoramic radiographs were in fact within the vessel. As far back as 1994, Friedlander and Baker documented this very fact and published their results in the Journal of the American Dental Association.5