Scatterogram: a method for outlining the body during lymphoscintigraphy without using external flood source.

BACKGROUND

We evaluated the feasibility of outlining the body with scattered photons using a low dose intradermal injection of the radiotracer. PATIENTS AND METHODS.: Sixty breast cancer patients were included into the study. 30 minutes post radiotracer injection static lymphoscintigraphy images were acquired using low energy high resolution collimator in anterior and lateral views. For patients with 2-day protocol another set of images was taken 20 hours post-injection. Two photopeaks were used during imaging: 1-Tc-99m (130-150 keV) and 2- Scatter photons (60-120). The fusion image of these two images was constructed by NM-NM fusion workflow of the workstation. The usual body outline of the patients was also acquired in 20 cases using the external flood source without moving the patients from their positions.

RESULTS

The early (30 minute image) scatterograms of the patients clearly showed the contour of the body. The 20 hour scatterograms were not as high quality as the corresponding early images. The constructed overlaid images showed the location of the axillary sentinel nodes and the body contours clearly for early scatterograms but not the delayed (20 hour) ones. The processing of the images for the reconstruction of overlaid scatterograms took the mean time of 10±5 seconds.

CONCLUSIONS

Imaging the scattered photons is feasible for the intradermal low dose injection of the radiotracers in order to outline the body contour. This imaging method does not increase the radiation exposure of the patients or operators and does not extend the time of imaging either.