Comparative Prevalence of Incidentally Detected Lung Malignancies on CTAC for MPI

We read with interest the study published by Tung and Heyns.1 It echoes the sentiments we espoused in our findings.2 We, too, support thorough investigation of incidental findings on computed tomography for attenuation correction (CTAC) during myocardial perfusion imaging (MPI). In particular, we share concerns about lung malignancies discovered by this avenue. Interestingly, there were considerable similarities as well as significant differences in the respective patient cohorts. The age group was comparable. In both groups, there was a range of histologic types represented. On the other hand, we noted that the series of patients studied by Tung and Heyns1 was entirely male. Most surprisingly was the occurrence rate of malignancies being discovered incidentally on MPI. The frequency of malignancy of chest in the patients who underwent MPI in this series was 0.73% (8/1,098 patients). By contrast, we identified 10 primary thoracic cancers amongst 3,122 patients. This equates to 0.32%. This is less than half the frequency suggested by Tung and Heyns. We wonder if the CTAC settings (in terms of voltage, current, collimator, rotation time and pitch) were comparable. Other factors which determine spatial resolution on CT scan include field of view, pixel size, focal spot size, magnification, patient motion, kernel, slice thickness, detector size.3 We are at a loss to explain the difference in detection rates otherwise. Perhaps the authors can give suggestions on why our respective cohorts, and prevalences, differed so significantly.