Caméras hybrides TEMP-TDM et semi-quantification du 123I-FPCIT : évaluation de l’apport de la TDM

Abstract

Objectives Tomoscintigraphy of dopamine transporters with 123I-FP-CIT is nowadays essential to visualise impairment of nigro-striatal system for the diagnosis of parkinsonism and for the differential diagnosis of dementia. With the development of hybrid cameras (SPECT-CT), the CT contribution in nuclear neurology needs to be assessed in diagnostic and semi-quantification performances. The main purpose of our study is to compare attenuation correction using CT to attenuation correction using the linear algorithm of Chang. SPECT-CT with parallel collimation results were also weighed against fan beam collimation and the contribution of partial volume effect correction was studied in secondary objective. Materials and methods We used a trilinear phantom to define spatial resolution and an anthropomorphic striatal phantom to quantify the activity in striatal cavities. We compared the impact of attenuation and scatter correction on spatial resolution and semi-quantification in striatum. We performed the partial volume effect correction on reconstructed images according to the method of Rousset. Results Attenuation correction by CT did not improve significantly spatial resolution compared to the algorithm of Chang. The semi-quantification of 123I-FPCIT in striata was not significantly different according to the various CA, but was significantly improved with CT attenuation and scatter correction. Partial volume effect correction improved the quantification from 40 to 60% in the striatal structures, when the activity was superior in at least twice the background noise. Conclusion SPECT-CT hybrid cameras increase spatial resolution and improve semi-quantification of 123I-FPCIT because of CT attenuation and scatter correction. Another use of CT is the possibility of calibrating anatomic segmentation of striata for partial volume effect correction. Partial volume effect correction improves quantification and is essential for early diagnosis of nigro-striatal disease.