Standardization of quantitative single photon emission computed tomography in control individuals and in patients with condylar hyperplasia

OBJECTIVES: The aim of the study was to evaluate the diagnostic accuracy of various single photon emission computed tomography (SPECT) quantitative methods in patients with condylar hyperplasia (CH) and to investigate whether normal condylar activity changes with age. PATIENTS AND METHODS: We analyzed the SPECT images of 33 patients with CH and those of 16 control individuals. Regions of interest (ROIs) were drawn on whole condyle, or fixed-size ROIs were drawn on both condyles and the clivus on the slice with higher activity [a two-dimensional (2D) approach] and on the summation of five adjacent transaxial slices [a three-dimensional (3D) approach]. A percentage difference between both condyles of above 10% or a cutoff value of 1.44 or 1.88 for abnormal condyle/clivus ratio was considered abnormal. RESULTS: Seventeen patients with active CH, 16 with inactive CH, and 16 control individuals were evaluated. The highest sensitivity and highest specificity were observed for the whole-condyle approach (88 and 87%, respectively), followed by the percentage 2D maximum condyle/total (82.4 and 81.3%, respectively). The condyle/clivus ratio yielded low sensitivity for both 2D and 3D approaches. No effect of age on condylar activity was demonstrated. No statistically significant difference in condyle/clivus ratio was evident between patients with active and those with inactive CH. CONCLUSION: Use of 2D maximum fixed-size ROI and percentual difference in condylar activity offers optimal diagnostic accuracy in patients with CH and should be encouraged in future studies. The condyle/clivus ratio offers suboptimal results and cannot, therefore, be recommended. No effect of age on normal condylar activity was demonstrated.