Yilmaz M, Capa G, Durak H, Degirmenci B, Evren I, Sayit E, Uçan E S
Department of Nuclear Medicine, Dokuz Eylul University, School of Medicine, Izmir, Turkey.
Clin Nucl Med. 2001 Feb;26(2):109-13. doi: 10.1097/00003072-200102000-00003.
To evaluate clearance changes of Tc-99m DTPA aerosol in mismatched and matched pulmonary perfusion defects.
Twenty-one patients (14 women, 7 men; mean age, 51 +/- 14 years) with possible pulmonary embolism were included in the study. On the day after perfusion (Q) scintigraphy with 5 mCi Tc-99m MAA, radioaerosol inhalation scintigraphy was performed using 45 mCi Tc-99m DTPA. Immediately and 45 minutes after the inhalation, early and delayed inhalation images (EI and DI, respectively) were obtained. Group 1 included 11 patients with mismatched defects who had a high probability of pulmonary embolism according to the Q/EI scan results. Group 2 included 10 patients with matched defects who had a low probability of PE. Contralateral normal lungs of 7 patients in group 2 served as controls (group 3). In groups 1 and 2, regions of interest were drawn over the mismatched and matched perfusion defects where they were best visualized, and this region of interest was mirrored to the same region on EI and DI images. For the control group, this was done in the contralateral normal lung. Mean counts in each region of interest were used for quantitative analysis, and the percentage clearance ratio was calculated using the following formula: early counts - late counts/early counts x 100.
The average percentage clearances for the three groups were as follows: group 1, 37% +/- 10%; group 2, 21% +/- 4%; group 3, 24% +/- 7%. Differences between groups 1 and 3 were significant, as were those between groups 1 and 2 (P < 0.05). Patients with mismatched perfusion defects had increased DTPA clearance compared with the control group and those with matched defects.
Vascular occlusion may lead to impairment of the alveolar-capillary barrier and consequently an increase in the clearance of Tc-99m DTPA aerosol in embolized regions. Immediately after inhalation, Tc-99m DTPA imaging should be started in the projection where perfusion defects are best seen to avoid potential misinterpretation of pulmonary embolism.
评估锝-99m二乙三胺五醋酸（Tc-99m DTPA）气雾剂在不匹配和匹配的肺灌注缺损中的清除变化。
本研究纳入了21例可能患有肺栓塞的患者（14例女性，7例男性；平均年龄51±14岁）。在用5毫居里锝-99m大颗粒聚合白蛋白（Tc-99m MAA）进行灌注（Q）闪烁扫描后的第二天，使用45毫居里Tc-99m DTPA进行放射性气雾剂吸入闪烁扫描。吸入后立即及45分钟后，分别获得早期和延迟吸入图像（EI和DI）。第1组包括11例根据Q/EI扫描结果肺栓塞可能性高的不匹配缺损患者。第2组包括10例匹配缺损且肺栓塞可能性低的患者。第2组中7例患者的对侧正常肺作为对照组（第3组）。在第1组和第2组中，在不匹配和匹配的灌注缺损最清晰可见的区域绘制感兴趣区，并将该感兴趣区映射到EI和DI图像上的相同区域。对于对照组，在对侧正常肺中进行此操作。每个感兴趣区的平均计数用于定量分析，并使用以下公式计算清除率百分比：（早期计数-晚期计数）/早期计数×100。
三组的平均清除率百分比如下：第1组，37%±10%；第2组，21%±4%；第3组，24%±7%。第组和第3组之间以及第1组和第2组之间的差异均具有统计学意义（P<0.05）。与对照组和匹配缺损患者相比，不匹配灌注缺损患者的DTPA清除率增加。
血管阻塞可能导致肺泡-毛细血管屏障受损，从而使栓塞区域的锝-99m DTPA气雾剂清除率增加。吸入后应立即在灌注缺损最清晰可见的投照方向开始进行Tc-99m DTPA成像，以避免对肺栓塞的潜在误判。
