This is the second article on DSCT (the Siemens Definition - dual source CT) to be published this quarter (the first article is discussed here). This article by Achenbach et al in the European Journal of Radiology, describes the findings in 14 patients, who underwent DSCT without heart rate control. They however had stable heart rates and a normal creatinine level.
Of these fourteen patients, seven patients could be reconstructed at 70%. However of these, six had a heart rate below 68 (approximated from the graph, since a table was not provided) and one patient with a heart rate of around 65 (as seen in the graph) had the best phase at 40%. One patient with a heart rate of around 75 had the best reconstruction at 70%, whereas the rest of the patients above a heart rate of 70 had variable reconstruction phases between 25% and 65%.
We know that with single-source CT, if the heart rate is below 68, a good diastolic reconstruction phase is always obtained between 60-70%. We also know that for heart rates above 78, we almost always get good data sets with systolic reconstruction phases of between 25-45% (Figs. 1, 2). This is something we discovered when we started doing gated cardiac CTs in pediatric patients for Tetralogy of Fallot (Fig. 3).
If this is the case and in any case even with DSCT, if systolic reconstruction phases are still necessary for heart rates above 75, is the role for DSCT really confined to the "bad band" of 68-77? Even in these cases, with a judicious use of two-segment reconstruction and an appropriate reconstruction phase, decent datasets are obtainable in more than 90% of cases. DSCT though should yield consistently good datasets in all patients irrespective of the heart rate with better side and small branch visualization, though the extent to which the latter would happen needs to be quantified with more studies.
In fact, heart rate control is becoming less and less important in practice. We still beta-block every patient to get a heart rate below 65. But if this is not possible, we still scan the patient at whichever heart rate is finally achievable and we rarely if ever seem to have a problem. With this scenario and the fact that we get really good datasets for heart rates above 81 using a single source Sensation 64, the role for DSCT really needs to be understood in great detail. This being a preliminary study, with more and more experience and expertise, I guess, all these issues will get sorted out and the real strength of DSCT will become more apparent.