Attenuation compensation in TC-99M SPECT brain imaging: Use of attenuation maps derived from tranmission versus emission data
- Univ. of Massachusetts Mecical Center, Worcester, MA (United States); and others
This study compares reconstructions of Tc-99m brain SPECT studies made using two methods of estimating the attenuation map: (1) transmission scanning, and (2) segmenting reconstructions of emission data and assigning attenuation coefficient values. A three-head SPECT system with fan beam collimators was used. Transmission scanning was performed using a line source at the focal line of a fan beam collimator right after the regular emission scan. The higher attenuation of the skull and the lower attenuation in the sinus cavities were identifiable despite the noise in the reconstructed transmission data due to: (1) the contamination of the transmission data by emission photons, (2) the maximum acquisition count rate imposed by the SPECT system, and (3) the clinical scanning time. Emission data were recorded using both photopeak and Compton scatter energy windows. Outlines of the head and the maxillary sinus could be obtained using only the Compton scatter reconstructions, whereas identifying the skull regions and the frontal sinus required the photopeak data as well. We placed appropriate linear attenuation coefficients in the soft tissue, bone, sinus and air regions (0.15,. 0.22, 0, and 0 cm{sup -1}) and blurred this attenuation map with a Gaussian kernel of about 0.2 cm standard deviation to obtain the attenuation map based on the emission data. Reconstructions were computed using the maximum likelihood expectation maximization algorithm with Siddon`s ray-tracing algorithm. Reconstructions based on the two attenuation maps were compared quantitatively on the patient data. The differences noted were quite small. These results imply that attenuation correction based on emission data alone may be adequate for Tc-99m SPECT brain imaging.
- OSTI ID:
- 198042
- Report Number(s):
- CONF-940605--
- Journal Information:
- Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: Suppl.5 Vol. 35; ISSN 0161-5505; ISSN JNMEAQ
- Country of Publication:
- United States
- Language:
- English
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