Methods: Images were acquired by varying a set of parameters: positions (antero-posterior (AP), posteroanterior (PA) and lateral), kilo-voltage peak (kVp) (66-90), source-to-image distance (SID) (150 to 200cm), broad focus and the use of a grid (grid in/out) to analyse the impact on E and image quality
(IQ). IQ was analysed applying two approaches: objective [contrast-to-noise-ratio/(CNR] and perceptual, using 5 observers. Monte-Carlo modelling was used for dose estimation. Cohen’s Kappa coefficient was used to calculate inter-observer-variability. The angle was measured using Cobb’s method on lateral
projections under different imaging conditions.
Results: PA promoted the lowest effective dose (0.013 mSv) compared to AP (0.048 mSv) and lateral (0.025 mSv). The exposure parameters that allowed lower dose were 200cm SID, 90 kVp, broad focus and grid out for paediatrics using an Agfa CR system. Thirty-seven images were assessed for IQ and
thirty-two were classified adequate. Cobb angle measurements varied between 16°±2.9 and 19.9°±0.9.
Conclusion: Cobb angle measurements can be performed using the lowest dose with a low contrast-tonoise ratio. The variation on measurements for this was ±2.9° and this is within the range of acceptable clinical error without impact on clinical diagnosis. Further work is recommended on improvement to
the sample size and a more robust perceptual IQ assessment protocol for observers.
|Title of host publication||OPTIMAX 2014 – radiation dose and image quality optimisation in medical imaging|
|Place of Publication||Lisbon, Portugal|
|Publication status||Published - 2015|
|Event||OPTIMAX 2014: radiation dose and image quality optimisation in medical imaging - Lisbon , Portugal|
Duration: 1 Aug 2014 → 31 Aug 2014
|Period||1/08/14 → 31/08/14|
- spinal curvature measurements
- effective dose
- image quality
- imaging phantom
- computed radiography