Inter- and intraobserver agreement in standard and ultra-fast single-photon emission computed tomography/computed tomography for the assessment of bone metastases.

Objective: To investigate inter- and intraobserver agreement using standard (std)-single-photon emission computed tomography/computed tomography (SPECT/CT) or ultra-fast acquisition (UF)-SPECT/CT as an add-on to planar whole-body bone scintigraphy (WB-BS) for the detection of bone metastases in patients with known cancer.
Methods: Images from patients (n = 104) participating in a prospective trial comparing SPECT/CT as an add-on to WB-BS with two different acquisition methods (std-SPECT/CT; 20 s per view, 32 views and UF-SPECT/CT; 16 views of 10 s per view) were included. The combinations of WB-BS with the two different SPECT/CT acquisition methods were independently evaluated by two experienced observers using a three-point scale (M0: no metastases, Me: equivocal for bone metastases and M1: bone metastases). The observers re-evaluated the scans 6 months later. Inter- and intraobserver agreement was calculated using linear weighted kappa.
Results: The linear weighted kappa for the interobserver agreement was 0.78 [95% confidence interval (CI) 0.61-0.94] for WB-BS with std-SPECT/CT and 0.84 (95% CI 0.67-1.00) for WB-BS with UF-SPECT/CT. Similar values were observed for the intraobserver agreement, in which the linear weighted kappa was 0.76 (95% CI 0.60-0.92) and 0.73 (95% CI 0.57-0.90) for std-SPECT/CT and UF-SPECT/CT, respectively.
Conclusion: Satisfactory inter- and intraobserver agreement was seen for both acquisition methods, emphasizing that the use of SPECT/CT as an add-on to WB-BS is a robust method for the detection of bone metastases even when conducted with a very short acquisition time.