Initial Characterization of Focal Bone Lesions with Conventional Radiographs or Computed Tomography: Diagnostic Performance and Interobserver Agreement Assessment

Abstract

Objectives: To ascertain the role of CT and conventional radiographs for the initial characterization of focal bone lesions. Methods: Images from 184 patients with confirmed bone tumors included in an ethics committee-approved study were retrospectively evaluated. The reference for benign-malignant distribution was based on histological analysis and long-term follow-up. Radiographs and CT features were analyzed by 2 independent musculoskeletal radiologists blinded to the final diagnosis. Lesion margins, periosteal reaction, cortical lysis, endosteal scalloping, presence of pathologic fracture, and lesion mineralization were evaluated. Results: The benign-malignant distribution in the study population was 68.5–31.5% (126 benign and 58 malignant). In the lesions that could be seen in both radiographs and CT, the performance of these methods for the benign-malignant differentiation was similar (accuracy varying from 72.8% to 76.5%). The interobserver agreement for the overall evaluation of lesion aggressiveness was considerably increased on CT compared to radiographs (Kappa of .63 vs .22). With conventional radiographs, 18 (9.7%) and 20 (10.8%) of the lesions evaluated were not seen respectively by readers 1 and 2. Among these unseen lesions, 50%–61.1% were located in the axial skeleton. Compared to radiographs, the number of lesions with cortical lysis and endosteal scalloping was 26–34% higher with CT. Conclusion: Although radiographs remain the primary imaging tool for lesions in the peripheral skeleton, CT should be performed for axial lesions. CT imaging can assess the extent of perilesional bone lysis more precisely than radiographs with a better evaluation of lesion fracture risk.

Initial Evaluation of Focal Bone Lesions: How Do We Do It?

“…However, radiographs have slightly better interobserver reproducibility than CT for assessing aggressiveness. 1 2…”

“…But in the axial skeleton (calvarium, spine, and pelvis), CT is preferred because ∼ 20% of focal bone lesions in these regions are poorly or not at all visible on radiographs. 1 Also, regardless of location, for lesions showing signs of aggressiveness on radiographs, complementary CT is recommended. It is more effective in assessing the extent of cortical destruction, which in turn correlates with the risk of fracture (percentage diameter involvement on the Mirels classification; Table 1 ).…”

“…Importantly, however, interobserver agreement in classifying periosteal reactions is mediocre on CT and radiographs (κ coefficient ∼ 0.4). 1 Moreover, some periosteal reactions may be nonspecific and do not follow the characteristics of aggressive or nonaggressive periosteal reaction types. Nonspecific periosteal reactions are not reliable criteria for differentiating benign and malignant lesions.…”

“…However, radiographs have slightly better interobserver reproducibility than CT for assessing aggressiveness. 1,2 But in the axial skeleton (calvarium, spine, and pelvis), CT is preferred because $ 20% of focal bone lesions in these regions are poorly or not at all visible on radiographs. 1 Also, regardless of location, for lesions showing signs of aggressiveness on radiographs, complementary CT is recommended.…”