BackgroundSize of abdominal aortic aneurysm (AAA) does not account entirely for rate of expansion or risk of rupture. More accurate methods of risk stratification are needed. Textural analysis of aneurysm CT data (CTTA) provides one approach. CTTA measures heterogeneity within standard CT images. Greater heterogeneity in tumours corresponds with adverse pathological features such as hypoxia and neovascularisation, and predicts reduced survival. In this study, we prospectively tested CTTA in AAA, assessing its association with annual expansion and need for intervention. In addition, we assessed the correlation between CTTA and 18F-fluorodeoxyglucose (FDG) uptake on PET, a marker of AAA inflammation. MethodsPatients with small and medium AAA underwent contrast CT and FDG PET with usual surveillance. CTTA (TexRAD software) was used on CT images from the sac and shoulder of each aneurysm. Fine, medium, and coarse CT textures were quantified with histogram-based parameters (standard deviation [SD], kurtosis, and entropy). Non-parametric statistical testing was used to assess significant correlations. Findings63 patients with a mean AAA diameter of 4·3 cm (SD 0·7) were included. Median annual expansion was 0·1 cm (IQR 0–0·3), with 13 patients requiring surgery across a median follow-up of 2·3 years (1·9–3·3). Shoulder CTTA kurtosis for medium texture was positively correlated with annual AAA growth (r=0·338 p=0·027). Shoulder CTTA entropy was significantly higher in patients who went on to require surgery (unfiltered images p=0·035), suggesting more heterogeneity in these patients. There were significant correlations between CTTA parameters and PET standardised uptake value in both the sac and shoulder—positive correlations with SD (sac, unfiltered r=0·313, p=0·012; shoulder, fine textures r=0·270, p=0·033), and inverse correlations with kurtosis (sac, unfiltered r=−0·330, p=0·008; sac, fine textures r=−3·03, p=0·017; shoulder, fine textures r=−0·247, p=0·051). InterpretationOur findings suggest that CTTA analysis can provide useful prognostic information about AAA. CT heterogeneity might be correlated with corresponding AAA FDG PET signal. CTTA parameters can be derived from standard CT images, potentially providing a straightforward and cost-effective means of risk stratification. FundingNational Institute for Health Research, Higher Education Funding Council for England.
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