Purpose: The British and European guidelines for myocardial perfusion imaging state that tracer uptake may be semi-quantitatively classified as normal (100-70% maximal uptake), mildly reduced (69-50%), moderately reduced (49-30%), severely reduced (29-10%), or absent (9-0%). We propose a novel colour scale for simple, objective classification of hypoperfusion to correlate with these thresholds.
Method: The colour scale is white at 100% of maximal uptake to check normalisation, red from 99-70%, yellow from 69-50%, green from 49-30%, blue from 29-10% and black from 9-0% with a linear transition between each colour. Therefore, myocardium that is red is normal and yellow is mildly hypoperfused etc. The new scale (NEW) was evaluated against a the routinely used 'function' scale (FUNCTION) with a Cardiologist observer trial of 11 stress-rest studies.
Results: Observers classified studies as normal, reversible, fixed or mixed. The Kappa statistic for agreement was 0.40 for NEW and 0.30 for FUNCTION.
Conclusion: The results show that the new semi-quantitative scale could improve observer agreement in terms of ischaemic/infarcted/normal myocardium as well as classification of hypoperfusion and summed scores when compared to a typical manufacturers scale. The NEW scale in now routinely used in two Newcastle hospitals and undergone further audit against angiography.
Peace R. Nuclear medicine patients and radiation detectors at UK ports and airports. HSE Radiation Protection News, May 2007.
Dr. Richard Peace RVI Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
Regional Medical Physics Department, Newcastle General Hospital, Newcastle upon Tyne, NE4 6BE, UK.
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