A new dynamic myocardial phantom for evaluation of SPECT and PET quantitation in systolic and diastolic conditions

We present a new dynamic myocardial phantom designed to evaluate SPECT and PET imaging in systolic and diastolic conditions. The phantom includes a thoracic attenuating media and the myocardial wall thickness varying during the scan can be performed. In this study the phantom was used with three different wall thickness characteristic of a systolic, end-diastolic and pathologic end-diastolic condition. The myocardium was filled with ^99mTc, ¹⁸F and Gd and imaged by SPECT, PET and MRI. SPECT attenuation correction was performed using a modified PET transmission. A bull´s eyes image was obtained for all data and wall ROI were then drawn for analysis. Using MRI as a reference, error from PET, SPECT and attenuation corrected SPECT were calculated. Systolic PET performances agree with MRI. Quantitation loss due to wall thickness reduction compared to the systole. Attenuation correction in SPECT leads to significant decrease of the error both in systole (from 29% to 14%) and diastole (35% to 22%). This is particularly sensitive for septum and inferior walls. SPECT residual errors (14% in systole and 22% in pathologic end-diastole) are likely caused by scatter, noise and depth dependant resolution effect. The results obtained with this dynamical phantom demonstrate the quantitation improvement achieved in SPECT with attenuation correction and also reinforce the need for variable resolution correction in addition to attenuation correction