Transmission imaging with a SPECT system and a collimated line source
- Univ. of Western Ontario, London (Canada)
Transmission images of high resolution are needed for brain SPECT quantitation to provide skull thickness, attenuation coefficients and anatomical correlation. Consequently, a technique to acquire transmission CT images with a SPECT system by using a collimated line source positioned at the focal line of a fan beam collimator (FBC) has been developed. Without a line source collimator (LSC) the transmission images have a longitudinal resolution (LR) characterized by the resolutions of the FBC (depth dependent, {approximately}8mm FWHM at 15cm) and the detector ({approximately}4mm). Computer simulations show that the LSC will improve the LR; for a high resolution LSC the contribution of the FBC to the system resolution is negligible, creating a system with a LR that is comparable to the detector resolution and is independent of object depth. The transverse resolution (TR) is characterized by the detector resolution and is independent of the FBC and the LSC. Based on the computer simulations a LSC was constructed with tantalum septa 10cm long, 0.05cm thick and spaced 0.10cm apart. At a 60cm focal length the LR and TR are better than 4.8mm, as measured with a lucite rod phantom. Transmission images of a human head with a signal to noise ratio of 15 were acquired in 42min with a 1100MBq Tc-99m source. The use of a SPECT detector with high count rate capabilities will allow a fourfold increase in source strength and a corresponding decrease in the acquisition time. The measured bone (0.24{plus_minus}0.01cm{sup -1}) and brain tissue (0.17{plus_minus}0.01cm{sup -1}) attenuation coefficients were within experimental error of the narrow beam values. This work shows that brain transmission images of high isotropic resolution can be obtained using a SPECT system, a FBC and an optimized LSC.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 197964
- 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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