title: High-Pitch Dual-Source MDCT for Imaging of the Thoracoabdominal Aorta: Relationships Among Radiation Dose, Noise, Pitch, and Body Size in a Phantom Experiment and Clinical Study.
abstract: OBJECTIVE
  The purpose of this study was to investigate, both in a phantom experiment and a within-patient clinical study the relationships among radiation dose, image noise, pitch, and body size in MDCT angiography of the thoracoabdominal aorta, with the use of high-pitch dual-source and standard-pitch single-source acquisitions.
  
  
  METHODS
  A proprietary tapered phantom consisting of four ultrahigh-molecular-weight polyethylene cylinders was used to mimic the body size ranges (small, medium, large, and extra large) of patients in the United States. The phantom was imaged using both standard-pitch (0.8) and various high-pitch (range, 2.0-3.2 [in increments of 0.4]) settings. Standard-pitch and high-pitch acquisitions were also performed in 45 patients (27 men, 18 women; mean age, 67.6 years).
  
  
  RESULTS
  At standard pitch, the volume CT dose index (CTDIvol) increased with phantom size, in a logistic sigmoid relationship. At high-pitch settings, the CTDIvol increased gradually in relation to phantom size, up to a threshold (denoted by tCTDI[pitch] ≈ 48.3-7.5 pitch), which linearly decreased (R(2) = 0.99) with pitch (maximum CTDIvol output at pitch [maxCTDI(pitch)] ≈ 18.9-3.9 pitch). A linear decrease in the size-specific dose estimate (SSDE) was observed beyond phantom size thresholds (tSSDE[pitch] ≈ 47.6-8.6 pitch) linearly decreasing (R(2) = 0.98) with pitch (maximum SSDE output at pitch [maxSSDE(pitch)] ≈ 15.5-1.3 pitch). Image noise was statistically significantly lower at standard pitch than at high-pitch settings (p = 0.01). In patients, statistically significant differences were noted between standard and high-pitch settings in the mean CTDIvol(10.8 ± 2.6 and 8.3 ± 0.7 mGy, respectively), SSDE (11.3 ± 2.1 and 8.8 ± 1.5 mGy, respectively), and noise (9.7 ± 2.2 and 14 ± 4.2, respectively) (p < .0001, for all comparisons).
  
  
  CONCLUSIONS
  Lower radiation dose levels achieved with the use of a high-pitch technique reflect limitations in tube output occurring for medium to large body sizes, with an associated exponential increase in noise. The standard- and high-pitch techniques yield similar radiation dose levels for small body sizes.
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808 Erwin Rd, Durham, NC 27710.
authors.forename: Achille
authors.initials: A
authors.lastname: Mileto
authors.affiliation: 2 Siemens Healthcare USA Inc., Malvern, PA.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Ramirez-Giraldo
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808 Erwin Rd, Durham, NC 27710.
authors.forename: Rendon C
authors.initials: RC
authors.lastname: Nelson
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808 Erwin Rd, Durham, NC 27710.
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Hurwitz
authors.affiliation: 3 Carl E. Ravin Advanced Imaging Laboratories, Duke University Medical Center, Durham, NC.
authors.forename: Kingshuk Roy
authors.initials: KR
authors.lastname: Choudhury
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808 Erwin Rd, Durham, NC 27710.
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Seaman
authors.affiliation: 1 Department of Radiology, Duke University Medical Center, Box 3808 Erwin Rd, Durham, NC 27710.
authors.forename: Daniele
authors.initials: D
authors.lastname: Marin
mesh_terms: D000368:Aged; D001011:Aorta / Q000528:radiation effects*; D001027:Aortography / Q000379:methods*; D049628:Body Size; D005260:Female; D006801:Humans; D008297:Male; D061330:Multidetector Computed Tomography / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D012189:Retrospective Studies
keywords: MDCT; dual source; high pitch; noise; radiation dose