This is a retrospective study evaluating the bone mineral density (BMD) measurements derived from CT Colonography (CTC) datasets compared with bone mineral density measurements derived from DEXA in the same patients.

Two readers independently calculated BMD and T scores from 35 CTC datasets. All CT scans were performed on a 16 slice MDCT scanner (GE Healthcare) and DEXA measurements were obtained on a Hologic Discovery series A machine. CT bone density analysis was performed on a workstation using a specific bone mineral analysis package (Philips). The bone density measurements were obtained using 3 vertebral bodies from T12 to the L1 level. Density measurements were also obtained from fat and muscle structures to provide an internal reference from which the BMD T score and Z score are calculated. In total we assessed 35 patients of which 30 were males and 5 females, the mean age was 66 (age range 54-79).

35 patients were evaluated who underwent CTC and also had DEXA BMD measurements. There were 30 males and 5 females, with a mean age of 66 years (age range 54-79). There was a correlation of 0.41 (p<0.0001) and 0.39 (p<0.0001) for the CT and Dexa BMD reading per vertebral body level, and 0.5 (p<0.0001) and 0.51 (p<0.0001) for the CT and Dexa T score per vertebral body for reader 1 and 2 respectively. For the CT and Dexa BMD averaged for all vertebra there was a correlation of 0.66 (p<0.0001) and 0.61 (p<0.0001) for reader 1 and 2 respectively. The CT and Dexa T score average was 0.6 (p<0.0001) and 0.59 (p<0.0001) for reader 1 and 2 respectively. The mean Dexa and CT, for BMD and T values were 1.009, 90.9 and -0.78, -2.14 respectively. Kappa was 0.69 per vertebral level and 0.75 overall.

There was excellent agreement between the retrospectively derived BMD and T scores from the CTC data set and the patients BMD measurements and T scores generated from DEXA to assess patient’s osteoporosis status. The results were also reproducible with good interobserver agreement

In this study we used patients who underwent CTC as they would also be at risk for osteoporosis. We were able to identify patients with osteoporosis on CTC, as well as screen for colorectal cancer.