A recent expansion in the use of digital detectors in radiology has led to increasing interest in the use of quantitative metrics for assessing image quality. These metrics include detective quantum efficiency (DQE) and modulation transfer function (MTF). It has been suggested that this type of approach could supplement or even replace existing psycho-physical methods such as the manual scoring of contrast-detail and line-pair phantoms (Metz et al. 1994, Marshall 2006, Marshall 2007, IPEM 2010). However, quantitative methods have yet to find widespread application in routine quality assurance. One impediment to their widespread adoption is the difficulty in relating the results to those of the more familiar contrast-detail methods.
This study, which I completed as part of my part-time MSc in Medical Physics at University College London aimed to generate a model linking quantitative and psycho-physical methods and conduct an analysis of their relative reproducibility. I did this MSc from 2009-2011 as part of my medical physics training at Oxford Radcliffe Hospitals NHS Trust, and all the experimental work was conducted there, under the supervision of Mary Cocker.
This project is now complete and the project report is available.
Contrast Detail Phantom Study
I previously requested hospital physicists who have previously scored contrast-detail phantoms such as the Leeds Test Object TO.20 to score a selection of ten images (6 TO.20, 4 Huttner). The results are discussed in the project report, but you can download the anonymised data as an Excel 97/03 spreadsheet if you would like to use it for your own study.
The images which participants were asked to score are also available for download. The images are all in DICOM format and can be viewed with standard DICOM viewers. Full details of how to score the images are provided in a PDF documents in the ZIP file. Please do not send in results as this study is now complete.
IPEM Report 32 Part VI, Measurement of the Performance Characteristics of Diagnostic X-Ray Systems: Digital Imaging Systems, 2010.
Marshall N. W.,A comparison between objective and subjective image quality measurements for a full field digital mammography system, Phys. Med. Biol. 51, 2441-2463, 2006.
Marshall N. W., Early experience in the use of quantitative image quality measurements for the quality assurance of full field digital mammography x-ray systems, Phys. Med. Biol. 52, 5545-5568, 2010.
Metz C. E., Wagner R. F., Doi K., Brown D. G., Nishikawa R. M. and Myers K. J, Toward consensus on quantitative assessment of medical imaging systems, Med. Phys. 22, 1057-1061, 1994.