title: Helical multidetector row quantitative computed tomography (QCT) precision.
abstract: OBJECTIVE
  The impact of varying image acquisition parameters on the precision of measurements using quantitative computed tomography is currently based on studies performed before the advent of helical image acquisition and multidetector-row scanners. The aim of this study was to evaluate helical multidetector-row quantitative computed tomography to determine the factors contributing to the overall precision of measurements on quantitative computed tomography conducted using current vintage computed tomographic (CT) scanners.
  
  
  METHODS
  The effects of CT protocol parameters (x-ray tube voltage and current, pitch, gantry rotation speed, detector configuration, table height, and reconstruction algorithm) and short-term scanner variation were examined on two commercially available quantitative CT (QCT) systems (ie, a combination of reference phantoms and analysis software) using seven multidetector-row CT scanners (available from a single vendor) operated in helical mode. Combined with simulated patient repositioning using three ex vivo spine specimens, precision (coefficient of variation) estimates were made on the basis of three scenarios: "best case," "routine case," and "worst case."
  
  
  RESULTS
  The overall best-case QCT precision was 1.4%, provided that no changes were permitted to the bone mineral density (BMD) scan protocol. Routine-case examination (with a BMD reference phantom in place) that permitted some variation in the x-ray tube current and table speed produced a precision of 1.8%. Without any constraints on the clinical QCT examinations, the worst-case precision was estimated at 3.6%.
  
  
  CONCLUSIONS
  Although small in appearance, these errors are for single time points and may increase substantially when monitoring changes through QCT measurements over several time points. This calls for increased caution and attention to detail whenever using helical multidetector-row quantitative computed tomography for the assessment of BMD change.
authors.affiliation: Radiation Oncology Centers of Southwest Florida, Bradenton, FL, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Bligh
authors.forename: Luc
authors.initials: L
authors.lastname: Bidaut
authors.forename: R Allen
authors.initials: RA
authors.lastname: White
authors.forename: William A
authors.initials: WA
authors.lastname: Murphy
authors.forename: Donna M
authors.initials: DM
authors.lastname: Stevens
authors.forename: Dianna D
authors.initials: DD
authors.lastname: Cody
mesh_terms: D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D036542:Tomography, Spiral Computed / Q000295:instrumentation* / Q000379:methods*