The Leeds Teaching Hospitals NHS Trust Is Grey the New Black? Image Display Optimisation & Consistency for Softcopy Reporting Mark Barnfield St James’s University Hospital, Leeds The Leeds Teaching Hospitals NHS Trust Softcopy Concerns… Softcopy more often becoming last component in the ‘Imaging chain’. In NMed chain can cost in excess of £300K – undertake well developed QA protocols. … however, workstation monitors relatively inexpensive ~£300 – possible weak link with little or no QA system employed. The Leeds Teaching Hospitals NHS Trust Image Quality Approach St James’s NMed Optimisation (currently qualitative) To improve presentation of radiological images and ensure that important image information is not lost during visual inspection. Consistency Images should appear similar on different displays or on the same display at different times. The Leeds Teaching Hospitals NHS Trust First step - Display Preparation Monitor Cleanliness Display quality is compromised by dust, fingerprints, ink, etc. Reduction in luminance. Possible misinterpretation. Needs cleaning on regular basis and on as-needed basis. Lint free cloth to reduce static. Never spray directly onto monitor. Manufacturer may recommend special cleaner for monitors coated with antireflective or antiglare coatings. The Leeds Teaching Hospitals NHS Trust The SMPTE Test Pattern Ref:Radiology 1985; 154: 519-527 Picture Boarder Uniformity Mid-band streaking Linearity & Geometric distortion Brightness & Contrast Resolution response Focus The Leeds Teaching Hospitals NHS Trust An Optimal Contrast Range Brightness & Contrast Adjustment 1. Set to ~50% and back off 2. Bring up until black just turns grey and back off fraction 3. Set to give reasonably bright white level but avoid loss of image definition The brightness and contrast of your monitor are adequately set if the inner 5% squares at both ends of gray scale are visible. The Leeds Teaching Hospitals NHS Trust Observations 17” Iiyama – Vision Master 403 Visual Geometric (Aspect ratio) distortion – squares rectangles Barrelling Also observed pincushion on my PC! Refresh vertical rate 66Hz - <72Hz some observers can perceive flicker and greater eye stain is possible. Known that nearly all parameters are dependent on position on screen - degrading from centre. The Leeds Teaching Hospitals NHS Trust DICOM Part14: (GSDF) Grey-Scale Standard Display Function The Consistent image Aims to mathematically define a display function for all image presentation systems. Aims for similarity in grey-scale perception between different display systems. Not a performance or image display standard. It does not define luminance range. The Leeds Teaching Hospitals NHS Trust Measuring Monitor Characteristic Curve Annex D - DICOM pt14 pp27-36 Background (20% of max lum) Target (10% area of screen) Photometer (Light-O-Meter 120 2 Luminance [cd/m ] P10 Std) Step target through greyscale range 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 Normalised Digital Driving Level 1 The Leeds Teaching Hospitals NHS Trust Curve Mapping Measured GSDF 2 Luminance [cd/m ] 120 100 80 60 40 20 0 0 0.2 0.4 0.6 0.8 Normalised Digital Driving Level 1 The Leeds Teaching Hospitals NHS Trust LUT set-up verification 5% & 95% contrast equally perceptible. Linear perception along the colour bar. The Leeds Teaching Hospitals NHS Trust Effect of brightness & contrast setting on display characteristic curves - PCs The Leeds Teaching Hospitals NHS Trust Reproducibility of monitor set-up using SMPTE test pattern NB. A – B done as consecutive measurements, C – D on separate occasions over a week. The Leeds Teaching Hospitals NHS Trust Proposed Frequency of QC Tests Weekly Monthly Monitor preparation Brightness & contrast adjustment Geometry Spatial resolution Quarterly Spatial uniformity Veiling glare The Leeds Teaching Hospitals NHS Trust Acknowledgements I would like to thank, Sarah Jervis for allowing the use of her SMPTE and DICOM 14 Matlab programs; David Brettle for guidance and technical support.