Dual-energy CT in colorectal cancers: beyond the density measurements.

I read with interest the article by Özdeniz et al. (1), on dual-source dual-energy computed tomography (DECT) to differentiate fecal matter from neoplasm. The study was well done and was based on density measurements in iodine maps and virtual unenhanced images. I would like to add a few points to the discussion. The main advantage of DECT is material decomposition and the relative iodine concentration can be measured in the iodine map images (2, 3). This is more objective compared with the visual analysis. In true mass lesions, because of iodine uptake, the relative iodine quantification (using region of interest) shows positive value (> 1 mg/ mL). In our example (Fig.), patient had a tumor in the descending colon, which showed increased iodine concentration (>1 mg/mL). However, fecal matter or bowel contents do not show increased iodine concentration. One of the limitations in this study was the small field of view (FOV), as the study was done using first generation dual-source DECT scanner. In second-generation (SOMATOM Definition Flash, Siemens Healthcare) and third-generation (SOMATOM Force, Siemens Healthcare) scanners (4), the FOV is 33 cm (Fig. c) and 35.6 cm, respectively (4). The third-generation scanner is sufficient for most small-sized patients. The limitation of FOV is not present in single-source DECT scanners. A summary of comparison between different DECT scanners is provided in the Table.