Lytic metastases in thoracolumbar spine: computer-aided detection at CT--preliminary study

To evaluate the sensitivity of a computer-aided detection (CAD) system for detection of lytic thoracolumbar spinal lesions at body CT, with results of manual lesion segmentation as the reference standard.

The study was HIPAA compliant and institutional review board approved; the institutional review board waived the need for informed consent. The CAD system segments the spine on CT images and searches for detections that match size, shape, location, and attenuation criteria. To reduce false-positive findings, 16 features for each detection were computed and fed to a classifier trained with manually segmented lesions. The data set consisted of CT studies of 50 patients (30 men, 20 women; range, 18-82 years; mean, 54.8 years) with 28 lesions. Studies were assigned to either a training (29 studies) or testing (21 studies) set. Sensitivities and false-positive rates (FPRs) for training and testing sets were calculated for these lesions, which were probable lytic metastases with areas 0.8 cm(2) or greater.

Training set sensitivity was 0.83 (10 of 12; 95% confidence interval: 0.51, 0.97), with an FPR of 7.4 per patient. Test set sensitivity was 0.94 (15 of 16; 95% confidence interval: 0.68, 1.00), with an FPR of 4.5 per patient. There was no significant difference between the CAD sensitivities of the training and test sets (P = .56). Of three false-negative findings, two were due to incomplete segmentation of the vertebral pedicle, and the third was rejected by the classifier. False-positive detections were most often attributable to veins that connect the basivertebral vein with the anterior venous plexus (106 [34%] of 310) and to low-attenuating disks (83 [27%] of 310).

This CAD system successfully identified probable lytic metastases in the thoracolumbar spine and generalized well to an independent testing set.