Development of external fiducial markers for image registration in small animal SPECT/CT

An image registration technique that can be used to register microCT and microSPECT images acquired with a high-resolution dual-modality SPECT/CT small animal imaging system is being developed. External fiducial markers containing droplets of the K₂HPO₄ (visible in CT)-^99mTc-pertechnetate (visible in SPECT) solution dispersed in narrow-gauge polyethylene tubing were placed on the object prior to imaging. According to phantom measurements, the optimum concentrations of the marker solution were found to be 250 mg/mL for K₂HPO₄ and approximately 6-8 mCi/mL for ^99mTc-pertechnetate. These concentrations were applied for a marker used to register mouse heart phantom images, and were easily visualized in both microSPECT and microCT images.