Purpose: Guidelines state that DMSA renal scintigraphic images should be acquired for 5 minutes or 3000 kcounts; this guidance is expert opinion rather than evidence based. We compared renal scar detectability using low and high count images.
Materials/Methods: During normal clinical imaging we acquired images as 7 minute dynamics. These were then reformatted as 2 minute statics (without motion correction) ["low count"] and 7 minute statics (with motion correction) ["high count"]. The high count images were in keeping with guidelines. We selected 40 abnormal and 28 normal cases covering a spectrum of appearance from normal to obviously scarred. Three expert observers reported the high count images and their consensus opinion taken as the gold standard. Six observers then independently reported all images viewed in a random order. ROC curve analysis was used to assess the difference between the techniques. The number of images and observers gave the study adequate power to detect clinically important differences.
Results: The mean areas under the ROC curves were 0.930 and 0.913 for the high and low count images respectively. The mean difference was 0.0163; the 95% confidence interval was (-0.0382, 0.0707), i.e. this difference is not significant.
Conclusion: This study indicates that adequate scar detection in DMSA renal scintigraphy can be obtained with considerable lower counts than conventionally recommended. This implies that either imaging time or radiation dose could be significantly reduced. Either of these strategies has important benefits as this technique is typically used in young children.
Saha A, Lloyd JJ. Do Lower Count DMSA Renal Scans In Children Allow The Acquisition Of Diagnostic Quality Images? (Poster presentation) UK Radiological Congress 2007.
Dr. Jim Lloyd, RVI Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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