Image-based assessment of spinal trabecular bone structure from high-resolution CT images

The goal of this study was to assess whether a high-resolution CT measure o f trabecular bone structure can enhance the discrimination between subjects with or without a vertebral fracture and having overall low hip or spine b one mineral density (BMD) by dual-energy Xray absorptiometry (DXA). Sixty-o ne women with low BMD by DXA (T-score <-2.5 at hip or spine) were examined. Twenty women had sustained a Vertebral fracture. Quantitative CT (QCT) BMD and high-resolution CT spinal scans were performed on a whole-body CT scan ner. For the high-resolution images (0.31 mm pixel, 1.5 mm thick slice), tr abecular bone was segmented from marrow using an adaptive threshold, region growth and skeletonization step. From the processed image we measured the apparent trabecular bone fraction (BV/TV), apparent trabecular thickness (I .Th) and apparent trabecular spacing (I.Sp). We also assessed the connectiv ity of the marrow space using region growing to derive a mean (HA) and maxi mum (H-M) hole size. Despite the fact that the study population was presele cted to have a low BMD by DXA, QCT BMD was highly associated with (p <0.005 ) with fracture status. All structural parameters were correlated (r simila r to 0.64 to 0.79) with BMD with p <0.003 and showed significant difference s between the fracture and non-fracture group. However, except for HAI this difference did not remain significant after adjustment for BMD. When BMD a nd then HA was entered into a paired linear regression model to predict fra cture outcome, HA contributed with p = 0.03 and BMD with p = 0.86. ROC anal ysis was applied and showed that H-A, BMD, I.Th and I.Sp discriminated the two groups with areas of 0.76, 0.75, 0.71 and 0.68, respectively. These fin dings suggest that an assessment of vertebral trabecular structure from hig h-resolution CT images is useful in discriminating subjects with vertebral fractures and potentially useful for predicting future fractures.