Spectral Differences In Ivus Radiofrequency (Rf) Data Between Normal And Aneurysmal Popliteal Artery Walls

Objective: Intravascular ultrasound (IVUS) backscattered data analysis has been utilized to evaluate the structure of atherosclerotic arteries in the clinical setting, but this technology has not been used to evaluate arterial wall changes associated with aneurysmal disease. The aim of this study was to compare spectral differences in IVUS backscattered data between normal and aneurysmal popliteal artery walls.
Methods: In vivo sequential raw IVUS data was collected from both normal and aneurysmal segments of popliteal arteries (N=4) from three patients (one with bilateral aneurysms). Popliteal artery aneurysm was defined as an arterial diameter 50% greater than an adjacent arterial segment. 240 normal and 234 aneurysmal regions of interest (ROI) of the medial component of arterial walls were selected. Corresponding time gain compensated raw IVUS RF data was analyzed using an autoregressive method to obtain the frequency spectrum of each ROI. Twelve parameters then characterized the frequency spectrum of each ROI. Two-sided t-tests were performed to compare spectral characteristics between normal and aneurysmal popliteal artery walls. A significance level of 0.05 was assumed for each test. Results are expressed as mean ± SEM.
Results: Eight spectral parameters were significantly significant between normal and aneurysmal popliteal arterial walls. A summary is shown in Table 1.
Conclusion: Statistically significant differences exist in IVUS spectral parameters between normal popliteal artery wall and popliteal artery aneurysm wall. Further evaluation of spectral parameters, including histopathologic correlation, is necessary. The use of IVUS-detected arterial wall alterations associated with aneurysmal degeneration may allow for the in vivo, early detection of vessel wall changes in the pre-aneurysmal state. Identification of arterial wall changes correlating with subsequent aneurysmal degeneration may have significant clinical implications such as determining adequate endograft “landing zone,” detecting “at-risk” arterial beds in patients with other aneurysmal disease, and defining aneurysms beyond current geometric definitions.