title: Effect of Model-Based Iterative Reconstruction on CT Number Measurements Within Small (10-29 mm) Low-Attenuation Renal Masses.
abstract: OBJECTIVE
  The purpose of this study was to assess the effect of model-based iterative reconstruction (MBIR) on CT number measurements within small (10-29 mm) low-attenuation renal masses.
  
  
  METHODS
  One hundred 10- to 29-mm exophytic or endophytic low-attenuation renal lesions imaged with CT (unenhanced and nephrographic [100 seconds] phases, 120 kVp, variable mA, 2.5-mm slice thickness) were identified in 100 patients. The raw CT source data were prospectively reconstructed twice: once using Veo MBIR and once using a blend of 30% adaptive statistical iterative reconstruction (ASiR) and filtered back projection (FBP). Lesions were chosen to form four equal-sized (n = 25) groups stratified by lesion size (10-19 or 20-29 mm) and growth pattern (endophytic or exophytic). Attenuation (in HU) was measured using identical ROIs and compared with two-tailed t tests. The effects of patient diameter and lesion anatomy on attenuation discrepancies of 5 HU or more were assessed using binary logistic regression.
  
  
  RESULTS
  Mean MBIR attenuation was not significantly different than mean 30% ASiR/FBP attenuation in the overall study population (unenhanced phase, 17 ± 13 vs 17 ± 13 HU, p = 0.74; nephrographic phase, 31 ± 27 vs 30 ± 26 HU, p = 0.89) or in any subgroup (p = 0.63-0.95). Only lesion size predicted discrepancies of 5 HU or more (p = 0.008; odds ratio, 1.20 [95% CI, 1.05-1.34] per 1 mm decrease) (p = 0.19-0.98 for the other variables). Seven lesions had enhancement of 20 HU or more with only one reconstruction method (MBIR = 4; 30% ASiR = 3).
  
  
  CONCLUSIONS
  Veo MBIR has no significant or consistent effect on attenuation measurements within small (10-29 mm) low-attenuation renal masses and is therefore unlikely to change clinically accepted attenuation thresholds for renal mass characterization.
authors.affiliation: 1 Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr, B2-A209P, Ann Arbor, MI 48109.
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Shampain
authors.affiliation: 1 Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr, B2-A209P, Ann Arbor, MI 48109.|2 Michigan Radiology Quality Collaborative, Ann Arbor, MI.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Davenport
authors.affiliation: 1 Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr, B2-A209P, Ann Arbor, MI 48109.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Cohan
authors.affiliation: 1 Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr, B2-A209P, Ann Arbor, MI 48109.
authors.forename: Mitchell M
authors.initials: MM
authors.lastname: Goodsitt
authors.affiliation: 1 Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr, B2-A209P, Ann Arbor, MI 48109.
authors.forename: James H
authors.initials: JH
authors.lastname: Ellis
authors.affiliation: 1 Department of Radiology, University of Michigan Health System, 1500 E Medical Center Dr, B2-A209P, Ann Arbor, MI 48109.
authors.forename: Joel F
authors.initials: JF
authors.lastname: Platt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D007479:Iopamidol; D007674:Kidney Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007479:Iopamidol
keywords: CT; enhancement; model-based iterative reconstruction; pseudoenhancement; renal mass