A CdZnTe-based automated Blood Counter for Quantitative Molecular Imaging

Abstract

Positron Emission Tomography (PET) and Single- Photon Emission Computed Tomography (SPECT) are well established molecular imaging modalities used in many fields of the biomedical sciences. They allow in vivo investigations of biological processes at the molecular level, and provide valuable information on the onset and progression of diseases. The images obtained are based on a measurable number of nuclear disintegrations and, as such, are inherently quantitative. However, the quantitative nature of these modalities is usually dismissed, largely because tools and methods dedicated to quantitative imaging are lacking. Accurate quantification in PET and SPECT typically requires frequent assessments of blood activity through indirect image-based estimations or direct sampling and measurements in a well-counter to obtain a time-activity curve that will feed pharmacokinetic models. These methods however can be inaccurate and error-prone. A new automated tool for the determination of blood activity as a function of time is presented. The device relies on a peristaltic pump for continuous blood withdrawal and can package blood samples in evacuated tubes at specific times for further analysis. The device uses a 20×20×15 mm³ Cadmium Zinc Telluride (CZT) detector, read by a custom-made preamplifier and a FPGA-based signal processing unit. A Graphical User Interface (GUI) offers a user-friendly interface with preselected parameters to perform an acquisition. This paper presents the overall design of the tool as well as preliminary results related to detector performance in terms of linearity, stability and sensitivity. The sensitivity is estimated at 0.9 cps/Bq/μL.