Visual grading analysis of digital neonatal chest phantom X-ray images:
Impact of detector type, dose and image processing on image quality
M. H. Smet
N. W. Marshall
Received: 28 July 2017 /Revised: 13 December 2017 / Accepted: 29 December 2017 /Published online: 19 February 2018
European Society of Radiology 2018
Objectives To evaluate the impact of digital detector, dose level and post-processing on neonatal chest phantom X-ray image
Methods A neonatal phantom was imaged using four different detectors: a CR powder phosphor (PIP), a CR needle phosphor
(NIP) and two wireless CsI DR detectors (DXD and DRX). Five different dose levels were studied for each detector and two post-
processing algorithms evaluated for each vendor. Three paediatric radiologists scored the images using European quality criteria
plus additional questions on vascular lines, noise and disease simulation. Visual grading characteristics and ordinal regression
statistics were used to evaluate the effect of detector type, post-processing and dose on VGA score (VGAS).
Results No significant differences were found between the NIP, DXD and CRX detectors (p>0.05) whereas the PIP detector had
significantly lower VGAS (p< 0.0001). Processing did not influence VGAS (p=0.819). Increasing dose resulted in significantly
higher VGAS (p<0.0001). Visual grading analysis (VGA) identified a detector air kerma/image (DAK/image) of ~2.4 μGy as an
ideal working point for NIP, DXD and DRX detectors.
Conclusions VGAS tracked IQ differences between detectors and dose levels but not image post-processing changes. VGA
showed a DAK/image value above which perceived IQ did not improve, potentially useful for commissioning.
• A VGA study detects IQ differences between detectors and dose levels.
• The NIP detector matched the VGAS of the CsI DR detectors.
• VGA data are useful in setting initial detector air kerma level.
• Differences in NNPS were consistent with changes in VGAS.
Keywords Newborn infant
Area under the VGC curves
CI Confidence interval
DAK Detector Air Kerma
DAP Dose Area Product
DQE Detector quantum efficiency
DRL Dose Reference Levels
DRX Needle crystal-based wireless CsI DR
DXD Needle crystal-based wireless CsI DR Agfa
ESAK Entrance Surface Air Kerma
FPDs Flat panel detectors
ICC Intra-class correlation coefficient
IQ Image quality
M2 Musica 2 Agfa
M3 Musica 3 Agfa
MTF Modulation transfer function
NICU Neonatal intensive care unit
NIP CR Needle crystal-based phosphor Image Plate
NNPS Normalized noise power spectrum
OR Odds ratio
* M. H. Smet
Department of Radiology, University Hospital Leuven, Herestraat,
49, 3000 – Leuven, Louvain, Belgium
Medical Imaging Research Center, Medical Physics and Quality
Assessment, Katholieke Universiteit Leuven, 3000 - Leuven,
European Radiology (2018) 28:2951–2959