Dr.sushanta pal
Description
In this retrospective study, 16 patients were included who had undergone 99mTc-pertechnetate salivary scintigraphy for various reasons but had normal salivary scintigraphy reports. Three different sets of background in different anatomical positions were chosen: (i) A pair of supraclavicular background ROI, (ii) an isolated central rectangular background ROI in brain, and (iii) an isolated suprathyroid ROI. We then calculated two important semi quantitative parameters, i.e., Us and Ds from the TAC of the salivary glands. Individual TAC was generated against each set of the above-mentioned backgrounds. Individual pixel histogram was also generated against each TAC. Minimum and maximum pixel count of the generated background pixel histograms was identified. Comparative studies were made among the afore-mentioned variables. Dynamic salivary gland scintigraphy was performed following the injection of 370 MBq99mTc sodiumpertechnetate with the gamma camera and data analysis system dual-head gamma camera (Siemens), equipped with low energy high-resolution parallel-hole collimator was used for imaging. Sequential anterior images of the salivary glands were obtained at 20 s per frame[1,2] for 50 min. Forty minutes after the injection of the tracer, 2 mL of lemon juice was administered orally for salivary glands stimulation. We selected the frame after 20 min with optimum counts, have drawn ROI on each of the salivary glands (parotid and submandibular). Then for each patient, we applied different sets of background ROIs. Against each set of background ROI, TAC for each of the parotid gland and submandibular glands were generated. We aimed to assess the correlation among the derived semi-quantitative parameters with minimum and maximum pixel count of background ROIs in different anatomical positions. These two parameters were assessed in during salivary scintigraphy through: (a) accumulation (uptake) of 99mTc-pertechnetate and (b) stimulated secretion (excretion) of 99mTc-pertechnetate. Thus, it is evident from the definition that the selection of background counts is of critical importance for calculating both the parameters and that over or under subtraction of the background counts while drawing the ROI would falsely elevate or reduce the clearance or secretion index of the salivary glands. The required semiquantitative parameters, i.e., upslope (Us) and downslope (Ds) were calculated from each timeactivity curve (TAC) derived from salivary scintigraphy following subtraction of backgrounds in different anatomical positions. I