Objective: Bone scintigraphy (BS) has been the mainstay in evaluating patients with mandibular condylar hyperplasia (CH).
Both planar BS and single photon emission computed tomography (SPECT) have been used to determine cessation of
condylar hyperactivity before corrective surgery. The present study aimed to examine the utility of the relatively new single
photon emission computed tomography/computed tomography (SPECT/CT) technique for evaluation of CH.
Material and Method: Sixty-one mandibular Tc-99m methylene diphosphonate bone SPECT/CT studies were reviewed. Images were analyzed without and with fusion with anatomical CT. Condylar uptake were quantified and differences in uptake between the right and left condyles were determined by both maximum uptake and average uptake in the region of interes (ROI). Differences exceeding 10 percentage points indicated condylar hyperactivity.
Results: SPECT and SPECT/CT showed positivity in 34 and 31 examinations, respectively. Agreement between the two modalities was high, but was not perfect. SPECT was found to be more reproducible than SPECT/CT. Quantification using
maximum ROI counts was more reproducible than using average ROI counts.
Conclusion: No evidence was found to indicate superiority of SPECT/CT over simple SPECT for evaluation of condylar
hyperactivity in CH, as demonstrated by the lower intra-modality reproducibility and a trend towards lower sensitivity for detection of hyperactive condyles. Utilization of SPECT alone would further benefit in terms of reduction of patient radiation exposure which is a concern, especially in younger patients such as those with CH. When using quantification, maximum ROI counts should be used over average ROI counts.

Keywords: Condylar hyperplasia, Facial deformity, Facial asymmetry, Bone scintigraphy, Single photon emission computed tomography, Radionuclide imaging