A new study shows that positron emission tomography-computed tomography (PET-CT) can be performed in peripheral arteries “with strong reliability”, according to the investigators. They say also that their results may provide early evidence of possible links between calcification and inflammatory processes occurring within the lower limb arterial tree.
Atherosclerosis is linked with both inflammatory and microcalcification processes occurring at the vessel wall. Novel imaging techniques such as PET-CT have been developed to assess such processes using 18F-fluorodeoxyglucose (18F-FDG—inflammation) and 18F-sodium fluoride (18F-NaF—calcification). Such imaging has been predominantly undertaken within the coronary and carotid circulation, Mohammed Chowdhury, Division of Vascular & Endovascular Surgery, Addenbrooke’s Hospital, Cambridge University Hospital Trust, Cambridge, UK, said at the British Society of Endovascular Therapy Annual Meeting (BSET; 2–3 July, Walton Hall, UK).
This proof of concept study from Cambridge is the first to prospectively validate PET-CT analysis in peripheral arterial disease. The aims were to demonstrate proof of feasibility for lower limb arterial FDG and NaF molecular imaging using PET-CT analysis and determine the relationship between inflammation, microcalcification and macrocalcification within the peripheral arteries.
Eight patients (16 legs; five men, median age 74.5 years) with intermittent claudication underwent PET-CT analysis using the 18F-NaF and 18F-FDG tracers and standard protocols. For each scan, the lower limb arterial tree was examined from the aortic bifurcation to the ankle. The degree of arterial calcification was measured using a modified Agatston score. Atherosclerotic disease burden was analysed using Bollinger score assessment.
Overall the whole limb median TBR level for 18F NaF was 1.30 (0.98–1.73) and for 18F FDG was 1.42 (1.11–1.75). The median limb arterial calcification score was 1954.5 (1198–2216). Significant correlations were seen between FDG uptake and both NaF uptake and arterial calcification and there was an inverse relationship between NaF tracer uptake and arterial calcification (all p<0.05). Increasing burden of atherosclerosis was associated with lower NaF uptake and a higher arterial calcification (p<0.05).
Chowdhury told delegates that the study provided proof that PET-CT analyses can be performed in the lower limb arterial tree with strong reliability and early evidence of possible links between calcification and inflammation requiring further longitudinal evaluation. “These techniques have potential to inform about biology and risk, predict disease progression and restenosis risk and measure change in inflammation/calcification with therapy,” he said, and added, “Further studies are required to look at longer-term consequence of such findings with regard to atherosclerotic progression/development.”
The results of the feasibility study were published in Heart (2015;101:A114). The lead author is Patrick Coughlin with collaboration with James Rudd.