Abstract
A method of scatter compensation has been developed that incorporates planar transmission measurements in the estimation of photopeak scatter in SPECT. Methods: The scatter distribution is first estimated by convolving the planar projections with a monoexponential scatter function. The number of scattered events that subsequently reach the detector as a proportion of total events (i.e., scatter fraction) is then determined for each point in the projections based on narrow-beam transmission values, obtained using an external source. The assumptions of the method were tested using 99mTc and 201Tl point and line sources. The quantitative and qualitative impact of transmission-dependent scatter correction was assessed in realistic phantom experiments simulating blood-pool, lung and myocardial perfusion studies. Results: The method accurately predicts the scatter distribution from 99mTc and 201Tl line sources in a phantom with variable density. Reconstructed counts are artificially enhanced in regions of high tissue density when scattered events are not removed from the projections prior to attenuation correction. Using convolution-subtraction with a constant scatter fraction (k = 0.4), scatter is underestimated in the heart and overestimated in the lungs, whereas transmission-dependent scatter correction enables activity to be quantified with ≥95% accuracy in heart and lung regions. Conclusion: We conclude that incorporating transmission data enables accurate scatter compensation in objects with nonuniform density.
| Original language | English |
|---|---|
| Pages (from-to) | 360-367 |
| Number of pages | 8 |
| Journal | Journal of Nuclear Medicine |
| Volume | 35 |
| Issue number | 2 |
| Publication status | Published - 1994 |
| Externally published | Yes |
Keywords
- attenuation correction
- Compton scattering
- quantitative SPECT
- transmission tomography