ATTENUATION CORRECTED MYOCARDIAL PET USING POST INJECTION TRANSMISSION MEASUREMENT - INFLUENCE ON RELATIVE REGIONAL UPTAKE VALUES

Aim: Post injection transmission measurement (PIT) can be performed us ing rotating Ge-68/Ga-68 linesources. This study estimates attenuation coefficients, count densities and relative regional uptake values of PIT corrected cardiac PET (E-PIT) compared to routinely pre-injection transmission measurement (RT). Methods: A thorax-phantom with homogene ously filled myocardium or with simulated defects and six patients wit h advanced coronary artery disease were studied using ECAT Exact tomog raph (Siemens CTI) equipped with three rotating linesources. Transmiss ion was performed twice (PIT, RT), attenuation coefficients and emissi on data were analysed, the latter without attenuation correction (E-UK ), corrected with PIT (E-PIT) and with RT (E-RT) (count density, stand ard and relative uptake values). Results: Both in phantom and patient studies attenuation coefficients differed significantly between PIT an d FIT. Comparing E-PIT and E-RT, regional uptake values were different only in phantom simulation with myocardial radioactivity concentratio ns higher than 10 kBq x ml(-1). The image contrast between defects and remaining myocardium in the phantom studies or the standard and relat ive uptake values in patient studies did nor vary significantly. Concl usion: Under clinical conditions a post injection transmission measure ment does nor influence the accuracy of regional myocardial uptake val ues relevantly.