New quantitative method for bone tracer uptake of temporomandibular joint using Tc-99m MDP skull SPECT

Quantitative bone SPECT studies have several advantages over qualitative studies for evaluating a temporomandibular joint (TMJ), yet in certain cases additional images are still needed. Accordingly, the current study developed a new easy SPECT quantification method for the bone tracer uptake in a TMJ and evaluated its usefulness and inter-observer variability in patients with TMJ pain.

Sixty-six adult patients (11 males, 55 females) with a mean age of 31 years (range 22-79 years) suffering from TMJ pain were questioned regarding the history of their condition, and then subjected to an oromaxillofacial examination and bone SPECT. New quantitative data for TMJs (TMJ index) were calculated from a formula using TMJ and skull counts.

TMJs with spontaneous pain had higher TMJ indices than those without spontaneous pain (8.87 vs. 6.87, P = 0.032). TMJs with mouth-opening pain or palpatory pain also exhibited higher TMJ indices than those without such pains, although the differences were not statistically significant. Positive TMJs, according to a visual SPECT interpretation, had much higher TMJ indices than the negative ones (8.99 vs. 5.37, P < 0.001). The reference skull count, mean TMJ count and TMJ index obtained using the proposed TMJ quantification method demonstrated an excellent correlation based on two independent observers (r = 0.996, r = 0.993 and r = 0.989, respectively; P < 0.001).

The current results indicate that the proposed quantitative TMJ bone SPECT is easy to perform, plus the resulting TMJ index has a lower inter-observer variability, making it an effective TMJ evaluation method for patients with painful TMJs, and especially useful for serial studies.