Implementation of a Tc-99m and Ce-139 scanning line source for attenuationcorrection in SPECT using a dual opposing detector scintillation camera

Image degradation during single photon emission computed tomography (SPECT) due to attenuation and Compton scatter of photons can cause clinical image artifacts and will also result in inaccurate quantitative data. Therefore attenuation correction methods recently received wide interest. Transmissio n imaging can be performed to obtain the attenuation coefficients of a nonh omogeneous attenuating medium accurately. The aim of this study was firstly to evaluate the imaging characteristics of the scanning line source assemb ly. The results obtained with Tc-99m and Ce-139 were compared. Secondly the calculated attenuation coefficients were compared with known values from l iterature, using Tc-99m and Ce-139 as transmission sources. Lastly the meth od of acquiring simultaneous transmission and emission data was investigate d. This study shows that an attenuation coefficient map can be obtained usi ng a scanning line source for transmission imaging with a dual opposing det ector camera. The imaging characteristics of Tc-99m and Ce-139 as transmiss ion sources are similar. The resolution obtained with the Ce-139 line sourc e was poorer than that obtained with the Tc-99m line source. A linear relat ionship was found between CT numbers and attenuation coefficients for trans mission images using both Tc-99m and Ce-139 line sources. The attenuation c oefficient value for water was underestimated by 1% using the Tc-99m transm ission source and underestimated by 10% using Ce-139 as transmission source . This under-estimation of attenuation coefficient values was also obtained in the human study. A myocardial perfusion study processed without and wit h attenuation correction clearly demonstrated the effect of the attenuation correction in the inferior myocardial region. The potential of using a sca nning line source as transmission source with a dual opposing detector came ra has been demonstrated in this study. The transmission source, Ce-139 was successfully introduced in this investigation for simultaneous acquisition of transmission and emission data. (C) 2000 American Association of Physic ists in Medicine. [S0094-2405(00)01806-X].