A kinetic compartment model for evaluating salivary gland scintigraphies

The semi-quantitative analysis of salivary gland scintigraphy with (99m) Tc-pertechnetate has been used to evaluate salivary gland function. However, no objective parameters distinguishing abnormal from normal functions have been established thus far. We propose using a simple kinetic model applied to the four major salivary glands. This kinetic model is based on a two-compartment model and the assumption of first-order kinetics to characterize normal salivary gland function and other selected parameters to evaluate the normal function of salivary glands.

Thirty patients referred for (99m) Tc-pertechnetate thyroid scintigraphy were studied. Dynamic imaging of the head in a fixed anterior projection was performed after an intravenous bolus injection of 150 MBq (99m) Tc-pertechnetate using a gamma scintillation camera. After 30 min, lemon juice was orally administered through a syringe. Time activity curves were generated for each of the four major salivary glands (i.e. the right and left submandibular and right and left parotid glands). Excretion fractions (the fraction of mobilizable radioactivity after administering lemon juice) and the gland activity-to-thyroid activity ratio were calculated. The data were fitted to both a one- and two-phase uptake model.

The median uptake slope and maximal activity were significantly higher in the parotid glands than the submandibular glands (P<0·0001). The gland-to-thyroid ratio was higher in the parotid glands than the submandibular glands (P<0·0001), and the ejection fractions were higher in the parotid glands (P<0·0001). No difference was found in functional contributions of the parotid and submandibular glands.

Tracer accumulation can be represented by a one-phase simple uptake model. The background regions that have been previously recommended in the literature are acceptable.