title: Effect of beam hardening on arterial enhancement in thoracoabdominal CT angiography with increasing patient size: an in vitro and in vivo study.
abstract: OBJECTIVE
  To assess the effect of beam hardening on arterial enhancement in thoracoabdominal computed tomographic (CT) angiography in various body sizes in a phantom and in a clinical study.
  
  
  METHODS
  An abdominal aortic phantom was placed in three cylindrical water containers simulating a small, an intermediate, and a large patient (diameters of 22, 30, and 40 cm, respectively). CT scanning was performed at 80, 100, and 120 kVp, and aortic attenuation was assessed. In a HIPAA-compliant institutional review board-approved study with waiver of informed consent, thoracoabdominal aortic attenuation was assessed in 100 consecutive patients (75 men, 25 women; mean body weight (BW), 79 kg) undergoing thoracoabdominal 64-section CT angiography at 80 kVp. Overall aortic attenuation in patients grouped according to BW (small patients [n = 26], <70 kg; intermediate patients [n = 41], 70-85 kg; large patients [n = 33], >85 kg) was compared. Overall aortic attenuation was correlated with BW, height, body mass index (BMI), body surface area (BSA), and lateral diameter by using linear regression.
  
  
  RESULTS
  Comparison of the intermediate- and large-phantom groups relative to the small-phantom group indicated that mean aortic attenuation decreased by 9.7% and 13.4% at 80 kVp, 9.8% and 15.1% at 100 kVp, and 13.8% and 23.8% at 120 kVp, respectively (P < .001). In the clinical study, the overall aortic attenuation decreased by 11.3% and 20.0% in the intermediate- and large-patient groups relative to the small-patient group, respectively (P < .05). Overall aortic attenuation correlated well with BSA (R = -0.454), height (R = -0.421), and BW (R = -0.414), followed by lateral diameter (R = -0.291) and BMI (R = -0.211).
  
  
  CONCLUSIONS
  Beam hardening may substantially contribute to reduced arterial enhancement in larger patients undergoing thoracoabdominal CT angiography. The beam-hardening effect on arterial enhancement is more pronounced at higher tube voltages.
authors.affiliation: Institute of Diagnostic, Interventional and Pediatric Radiology, University Hospital Berne, University of Berne, Freiburgstrasse 10, CH-3010 Berne, Switzerland. sschindera@aol.com
authors.forename: Sebastian T
authors.initials: ST
authors.lastname: Schindera
authors.forename: Isabelle
authors.initials: I
authors.lastname: Tock
authors.forename: Daniele
authors.initials: D
authors.lastname: Marin
authors.forename: Rendon C
authors.initials: RC
authors.lastname: Nelson
authors.forename: Rainer
authors.initials: R
authors.lastname: Raupach
authors.forename: Marc
authors.initials: M
authors.lastname: Hagemeister
authors.forename: Gabriel
authors.initials: G
authors.lastname: von Allmen
authors.forename: Peter
authors.initials: P
authors.lastname: Vock
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Szucs-Farkas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000295:instrumentation / Q000379:methods*; D001014:Aortic Aneurysm / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001027:Aortography / Q000379:methods*; D049628:Body Size; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods; D013902:Radiography, Thoracic / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013909:Thorax / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*