We measured the sensitivity and specificity of several semi-quantitative methods of Datscan image analysis. Data were compared with a gold standard of clinical diagnosis made 3 years after presentation.
50 patients with clinical follow-up of at least three years post Datscan imaging were used in this study. Each image was first registered with a template created using a separate set of 30 datscan images acquired on age-matched, normal subjects. Several semi-quantitative methods of analysis were then applied to each image and ROC analysis used to determine the most accurate technique.
The most sensitive area to analyse was the putamen with best results obtained using data from the most affected hemisphere. The most robust method of calculation compared uptake in the subject with uptake in the same region of the normal template. Using this combination, a sensitivity of 87% and a specificity of 84% was achieved. However, these values were not as high as those derived using visual inspection of the images (sensitivity 90%, specificity 95%).
We conclude that quantification methods can achieve high values of specificity and sensitivity in the interpretation of Datscan images. However, the methods used did not improve on the results achievable by expert visual interpretation.
Dr Ian Driver, NGH 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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