Differentiation of osteolytic metastases and Schmorl's nodes in cancer patients using dual-energy CT: advantage of spectral CT imaging.

PURPOSE

To assess the reliability of dual-energy CT (DECT) spectral imaging for the differentiation of bone metastases (BMs) from Schmorl's nodes (SNs) in the vertebrae of cancer patients.

MATERIALS AND METHODS

In this retrospective study, 102 cancer patients who underwent DECT (GE spectral CT Discovery CT750 HD scanner) had 110 low density vertebral lesions. Each lesion was characterized as a BM or SN, based on the typical MRI or SPECT/PET-CT findings as well as size and number change in the 6 months follow-up. The means of 140 kVp polychromatic CT values, 40-140 keV monochromatic CT values, slopes (k) of the spectral curves, bone(water) and water(bone) densities of BMs and SNs were measured and compared with independent-samples t-test. The difference values of the two lesions and their respective normal bone tissue were calculated (normal density-lesion density) and compared using independent-samples t-test. ROC curves were used to compare the diagnostic efficacies of these measures in the identification of SNs and BMs.

RESULTS

110 lesions consisting of 69 BMs and 41 SNs were identified. The spectral curve patterns and slopes for BMs and SNs were different (p<0.05). The water(bone) density of BMs (1009.02 ± 59.25mg/cm(3)) was higher than that of SNs (892.00 ± 83.65 mg/cm(3)) (p<0.01) while the bone(water) density (43.57 ± 50.87 mg/cm(3)) was lower than that of SNs (174.60 ±94.61 mg/cm(3)) (p<0.01). The 40 keV CT value, k, bone(water) density and water(bone) density had a higher diagnostic efficacy for differentiating the two lesions than polychromatic CT value (p<0.05).

CONCLUSIONS

Dual-energy CT imaging is accurate enough for identification of osteolytic metastases and Schmorl's nodes.