  Purpose: Photon-counting computed tomography (PCCT) shows promise for medical
imaging in regards to material separation and imaging of multiple contrast
agents. However, many PCCT setups are under development and are not optimized
for specific contrast agents or use cases. Here, we demonstrate how
experimental system parameters may be varied in order to enhance performance
and we propose a set of recommendations to achieve this based on contrast
agent.
  Approach: A table-top PCCT system with a cadmium zinc telluride (CZT)
detector capable of separating six energy bins was used to image multiple
contrast agents in a small phantom. The contrast agents were separated and the
concentration was quantified using K-edge subtraction. To increase system
performance, we investigated three parameters: beam filter type and thickness,
projection acquisition time, and energy bin width. The results from the
parameters were compared based on PCCT signal and contrast to noise ratio (CNR)
or noise in K-edge images. The concentrations of the contrast agents were
quantified in K-edge images and compared to known concentrations.
  Results: The bench-top PCCT system was able to successfully quantify the
contrast agents through K-edge subtraction. Decreasing projection acquisition
time showed a decrease in K-edge CNR. However, it did not scale as the square
root of time. Filter type and bin width demonstrated a dependence on the
specific contrast agent.
  Conclusions: The presented bench-top system demonstrated the ability to
separate contrast agents using K-edge subtraction and accurately determine
contrast concentration in K-edge images. Specific parameters for future use
will be chosen based on contrast agent.
