Dr.sushanta pal
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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
本回顾性研究纳入了16名因各类原因接受99m锝-高锝酸盐（technetium-99m pertechnetate）唾液闪烁显像（salivary scintigraphy）且显像报告正常的患者。我们选取了三种不同解剖位置的背景感兴趣区（Region of Interest，ROI）：(i) 一对锁骨上背景ROI；(ii) 脑内孤立的中央矩形背景ROI；(iii) 孤立的甲状腺上ROI。随后我们从唾液腺的时间-活性曲线（Time-Activity Curve，TAC）中计算得到两项关键半定量参数，即上升斜率（Us）与下降斜率（Ds）。针对上述每一组背景ROI，均可生成对应的个体TAC，并同步生成与每一条TAC匹配的像素直方图，进而确定该背景像素直方图的最小与最大像素计数。随后对上述各项变量开展对比分析。 本研究采用配备低能高分辨率平行孔准直器的双探头γ相机（Siemens）及配套数据分析系统，对静脉注射370 MBq 99m锝高锝酸钠的患者实施动态唾液腺闪烁显像。以每帧20秒的速率连续采集唾液腺前位图像[1,2]，总采集时长为50分钟。于注射显像剂后40分钟，经口给予2mL柠檬汁以刺激唾液腺分泌。我们选取注射后20分钟时计数最佳的图像帧，在每一侧唾液腺（腮腺及下颌下腺）上绘制ROI。随后针对每位患者，分别应用三组不同的背景ROI方案，针对每一组背景ROI，均可生成腮腺与下颌下腺各自的TAC。 本研究旨在评估不同解剖位置的背景ROI的最小、最大像素计数与衍生得到的半定量参数之间的相关性。上述两项半定量参数分别通过(a) 99m锝-高锝酸盐的摄取蓄积与(b) 刺激后的分泌排泄两个过程在唾液闪烁显像中进行评估。由此可见，背景计数的选取对于两项参数的计算均具有关键意义：在绘制ROI时，背景计数的过度减除或减除不足，均会错误地升高或降低唾液腺的清除率或分泌指数。本研究所需的半定量参数即上升斜率（Us）与下降斜率（Ds），均由经不同解剖位置背景校正后的唾液腺TAC计算得到。
