Scintigraphic Imaging of Inflammation in the Aortic Wall Using ^99mTc-Pyrophosphate

The aim of this study was to develop and test a technique for scintigraphic examination of the thoracic aorta, which allows for visualizing foci of inflammation.

The study included 15 patients (median age - 61 [47; 73] years) with aortic dilatation more than 45 mm and thoracic aortic aneurysm who were candidates for surgical treatment. All patients underwent a chest scintigraphy with ^99mTc-pyrophosphate 48 h before surgery to identify foci of inflammation in the aortic wall. The new technique included intravenous administration of 370 MBq of a radiopharmaceutical (RP), registration of scintigrams at 3 and 6 h after injection of RP in a tomographic mode combined with X-ray computed tomography. After the image reconstruction, subtraction of the later scintigrams from the early ones was performed, followed by analysis of the final images. The results of scintigraphy were compared with the histological data obtained from intraoperative samples of resected aorta.

According to the results of this novel scintigraphic technique, artifacts from the radioactivity of the vascular blood pool were eliminated and pathological RP uptake was identified in 5 (33.3±1.5%) out of 15 examined patients. The "focus/vessel lumen" ratio averaged at 1.47 [1.30; 1.48]. Histological examination of resected aorta samples confirmed the presence of chronic inflammation in 4 (26.7±1.3%) out of 15 patients. Parameters of diagnostic efficiency were: sensitivity - 100%, specificity - 91%, diagnostic accuracy - 93%.

The method of scintigraphic diagnostics of inflammatory processes in the aorta using ^99mTc-pyrophosphate, supplemented by subtraction of the late from the early images, makes it possible to eliminate artifacts from the radioactivity of the aortic blood pool and to reveal the pathological RP accumulation indicating the areas of inflammation in the aortic wall.