What is CZT?

The principles of operation

CZT detectors are fabricated with very thin metalized electrode geometries deposited on the detector surfaces. These electrodes are then electrically biased creating a difference in electrical potential within the detector volume. When ionizing radiation interacts with the CZT crystal, a large number of pairs of electrons and holes are created in proportion to the energy of the incoming radiation.

The negatively charged electrons and positively charged holes then migrate to the oppositely charged electrodes where they are collected. The resulting charge pulse is then detected by the preamplifier, which produces a voltage pulse whose height is proportional to the incident energy of the incoming photon. The signal from the preamplifier is then fed into a shaping amplifier that converts the signal into a Gaussian pulse and amplifies it. The signal can then be fed into a standard counting system or Multi-Channel Analyzer (MCA) to generate the characteristic spectrum for the incoming photons. We usually couple the cadmium zinc telluride CZT-based detector to an ASIC (application specific integrated circuit) to reduce the size and cost of the readout electronics.

4D spectral-spatial CZT Gamma detectors create a step-change in the performance of diagnostic imaging systems including SPECT (Molecular Imaging), Bone Mineral Densitometry (BMD, DEXA), Surgical Probes and Colour Photon-Counting Computed Tomography (CT). The change is akin to moving from a black-and-white vacuum-tube television to a colour digital high-definition flat screen. Higher resolution means clearer, more detailed images which make the job of diagnosis easier, with higher accuracy and diagnostic confidence at earlier stages of heart disease, cancer, osteoporosis and, increasingly, dementia. The smaller size and weight of CZT detectors (compared to existing scintillator detectors) has created a market for more economical siting and improved portability of scanning equipment and new operating techniques, for example, lower tracer dose, faster scan times, earlier diagnosis and using multiple tracers in one examination.

The overall impact is increased patient safety and care, lower overall health care costs and increased efficiency in hospitals.

Kromek provides a way for medical device manufacturers to be part of this transformation sooner, integrate CZT gamma cameras into their SPECT systems and bring new products to market cost-effectively.