Interpretation Method

The method of interpretation will undoubtedly affect reading time and probably diagnostic exam performance. Over the history of CTC, a wide range of software packages with varying capabilities have been used. In fact, software for CTC is still advancing rapidly and it is not uncommon to find that by time a peer-reviewed manuscript is in press, the software version used has been updated or is even no longer available. For this reason software platforms should be specified by vendor, version and other factors that can affect evaluation, such as: single vs dual monitor reading, mouse vs button control of navigation, automated vs manual fly-though. In the case of volume rendering, display parameters such as opacity and threshold should be reported in addition to standard window and grayscale level. For surface rendering displays, parameters such as threshold, contrast, lighting default settings should be reported. For both methods, it is important for investigators to report the field-of-view employed for scanning, and what if any zooming was employed during the interpretation of studies. Little head-to-head comparison has been made of these different viewing factors and the reporting of this data could assist in retrospective analysis of their affects (McFarland 2002).

Because it may affect reading time, the hardware platform upon which images are evaluated should also be specified. In particular, authors should report both the number of processors utilized in the display system and their clock speed. As cost analysis of CTC will be an important aspect of its evaluation, it is useful to separate interpretation time from the time needed to fill out research case report forms.

Many authors have used confidence scales to help in interpreting data (Pickhardt et al. 2004b). This is another source of variation between authors in how confidence scales and ROC curves are generated. We suggest that rating scales for any issues such as: a) quality of distension, b) residual fluid, c) residual solid stool, d) confidence that a polyp is present at particular size criteria, uses a four- or five-point scale with discrete verbal descriptors of each of the points.

When more than one reader's results are reported, clarify if the interpretations are independent or represent a consensus. Independent, multiple-observer studies are preferred. If reading time is reported, specify if this includes the time required to document the findings.

There should always be a retrospective analysis of the cause of false positive and false negative interpretations of CTC and CC, when those data are available.

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