Janne Johannes Nappi PhD, Presenter: Royalties, Hologic, Inc Royalties, MEDIAN Technologies

Daniele Regge MD, Abstract Co-Author: Nothing to Disclose

Radin Adi Nasirudin DIPLENG, Abstract Co-Author: Nothing to Disclose

Peter B. Noel PhD, Abstract Co-Author: Nothing to Disclose

Hiroyuki Yoshida PhD, Abstract Co-Author: Patent holder, Hologic, Inc Patent holder, MEDIAN Technologies

To develop computer-aided detection (CADe) of colorectal lesions for non-cathartic virtual monochromatic CT colonography (CTC).

Sixty-six patients were prepared for CTC by oral ingestion of 50 ml of iodinated contrast on the day before and two hours prior to dual-energy CT acquisition (SOMATOM Definition Flash, Siemens). The CT acquisitions were performed at 15 mAs for the 140 kVp scan and at 40 mAs for the 80 kVp scan. The dual-energy images were reconstructed by use of sinogram-affirmed iterative image reconstruction at 0.6–1.0 mm reconstruction intervals. Material decompositions were calculated from the dual-energy images to identify typical colon materials (air, fat, soft tissue, fecal tagging). Virtual monochromatic CTC images were reconstructed from the material-decomposition data at 125 keV to minimize image artifacts. A CADe system was designed to perform colon extraction, virtual bowel cleansing, and detection of soft-tissue lesions based on material-decomposition features and the virtual monochromatic images. A support-vector machine was used to reduce false-positive (FP) detections based on shape, texture, and material-decomposition features of the detected lesion candidates. For pilot evaluation, the per-lesion detection performance of CADe was estimated by use of the leave-one-patient-out method. Also the effective radiation dose of the CTC examination was assessed.

There were 22 colonoscopy-confirmed lesions ≥6 mm in size in 21 patients: 15 were ≥10 mm and 7 were 6–9 mm in size. The CADe system detected 96% of all lesions at 6.1 FPs per patient. For biopsy-confirmed advanced lesions (17 adenomas, serrated lesions, and carcinomas), the detection sensitivity was 100% at 6.1 FPs per patient. The average CT dose index by volume was 0.95 mGy and the effective dose was 0.75 mSv per CTC scan position (supine/prone/decubitus).

Material-decomposition features and virtual monochromatic images can be used to yield high CADe performance in the detection of significant lesions from non-cathartic CTC examinations.

A computer-assisted non-cathartic low-dose CTC examination could be used to provide high detection accuracy and high patient adherence while minimizing risks of colorectal screening.

Nappi, J, Regge, D, Nasirudin, R, Noel, P, Yoshida, H, Computer-aided Detection for Non-cathartic Low-dose Virtual Monochromatic CT Colonography.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14016518.html