title: CT signal heterogeneity of abdominal aortic aneurysm as a possible predictive biomarker for expansion.
abstract: OBJECTIVE
  There is a need for prognostic biomarkers for risk assessment of small abdominal aortic aneurysm (AAA). Since CT textural analysis of tissue is a recognized feature of adverse biology and patient outcome in other diseases, we investigated it as a possible biomarker in small AAA.
  
  
  METHODS
  Fifty consecutive patients (46-men, 4-woman, median-age 75 y, range 56-85) with small AAA (3-5.5 cm) under surveillance undergoing serial ultrasound were prospectively recruited and assessed at baseline with CT texture analysis (CTTA) and 18F-Fluorodeoxyglucose positron emission tomography (18F-FDG-PET). We followed forty patients (36-men, 4-woman, median-age=74 y, range 60-85, participation rate=80% for 1 year. For each axial image, CTTA using the filtration-histogram technique was carried out using a software algorithm that selectively extracts texture features of different coarseness (fine, medium and coarse) and intensity variation. Standard-deviation (SD) and kurtosis (K) at each feature-scale were measured. The maximum standardized uptake value (SUVmax) of 18F-FDG in each axial image of the AAA was also measured with corrections for blood pool 18F-FDG activity to assess AAA metabolic activity. Specificity, sensitivity, and c-statistics were calculated with 95% confidence intervals for prediction of significant AAA expansion (≥2 mm) by CTTA measures before and after adjusting for clinical variables.
  
  
  RESULTS
  The median aneurysm expansion at 12 months was 2.0 mm, (IQR 0.0-4.0). Coarse texture SD correlated inversely with AAA SUVmax (rs=-0.456, P=0.003). Medium coarse texture K correlated significantly with future AAA expansion adjusted for baseline size (rs=0.343, P=0.030). AAA SUVmax correlated inversely with AAA expansion corrected for baseline size (rs=-0.383, P=0.015). Medium texture K was a strong predictor of significant AAA expansion (area under the Receiver-operating-characteristic (ROC) curve was 0.813) after adjusting for clinical variables.
  
  
  CONCLUSIONS
  We have shown evidence that CT signal heterogeneity measurements in small aortic aneurysm may be considered as a risk stratification tool in future prospective studies to identify aneurysms at risk of significant expansion. CT textural data appears to reflect AAA metabolism measured by PET.
authors: Institute of Nuclear Medicine, University College London, University College Hospital, 235 Euston Road, London NW1 2BU, England, UK.
authors: Carl W
authors: CW
authors: Kotze
authors: Division of Cardiovascular Medicine, Addenbrooke's Hospital, Box 110, ACCI, Hills Road, Cambridge CB2 2QQ, England, UK.
authors: James H F
authors: JHF
authors: Rudd
authors: Institute of Nuclear Medicine, University College London, University College Hospital, 235 Euston Road, London NW1 2BU, England, UK.
authors: Balaji
authors: B
authors: Ganeshan
authors: Institute of Nuclear Medicine, University College London, University College Hospital, 235 Euston Road, London NW1 2BU, England, UK.
authors: Leon J
authors: LJ
authors: Menezes
authors: Institute of Nuclear Medicine, University College London, University College Hospital, 235 Euston Road, London NW1 2BU, England, UK.
authors: Jocelyn
authors: J
authors: Brookes
authors: Institute of Nuclear Medicine, University College London, University College Hospital, 235 Euston Road, London NW1 2BU, England, UK.
authors: Obiekezie
authors: O
authors: Agu
authors: Department of Vascular Surgery, Brighton and Sussex University Hospital, Eastern Road, Brighton BN2 5BE, England, UK.
authors: Syed W
authors: SW
authors: Yusuf
authors: Institute of Nuclear Medicine, University College London, University College Hospital, 235 Euston Road, London NW1 2BU, England, UK. Electronic address: ashleygroves@nhs.net.
authors: Ashley M
authors: AM
authors: Groves
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000453:epidemiology; D018450:Disease Progression; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods; D064847:Multimodal Imaging; D015588:Observer Variation; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D018570:Risk Assessment; D014463:Ultrasonography
chemical_list: D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Abdominal aortic aneurysm; CT signal heterogeneity; Computed tomography texture analysis; Positron-emission tomography; Risk stratification