Accurate alignment of ¹⁸F-FDG-PET and intravascular ultrasound (IVUS) images of atherosclerotic plaques with precise histological information can increase image reliability

Objectives ¹⁸F-FDG-PET and IVUS have been widely used as representative atherosclerosis imaging tools. Accurate alignment of aorta image with the precise histological information is necessary to increase their image reliability, but the heterogeneity and cylinder structure make the alignment difficult. In this study, we compared PET, IVUS and histological images accurately aligned by referring spinal position and investigated the in vivo ¹⁸F-FDG distribution and the histological information (macrophage distribution and foamy macrophage invasion) based on the precise aorta segmentation, using WHHL rabbits. Moreover, we investigated cellular distribution of injected FDG by ³H-FDG micro ARG.

Methods Nineteen WHHL rabbits (7-13 months) were used. The PET, IVUS and histological images were selected by referring the same position of 3rd-7th thoracic spine for their alignment. After all PET and histological images were divided into four ROIs, PET signal was measured. The foamy macrophage was identified by macrophage size and the invasion level was scored as 0~IV based on the amount, using H&E and anti-macrophage immunohistochemical staining images. Furthermore, a micro ARG study with ³H-FDG injection was performed.

Results IVUS provided intimal lesion area but not identify the macrophage position. On the other hand, the PET signal was detected mainly on the macrophage rich lesions and increased along with the foamy macrophage score. The score IV lesion showed significantly higher PET signal than the score 0 lesion (55.7 ± 4.4 vs. 39.8 ± 6.0, P < 0.0001). Furthermore, micro ARG showed the ³H-FDG was mainly distributed in foamy macrophage area surrounding the lipid core.

Conclusions ¹⁸F-FDG-PET provided the macrophage distribution and also foamy macrophage invasion level in the atherosclerotic lesions