Cadmium Zinc Telluride Semiconductor Detectors Research Articles

A hybrid CZT-LaBr3:Ce Compton camera system for improving proton therapy imaging

This work aims to combine the Polaris-J cadmium zinc telluride semi-conductor detector with a LaBr3:Ce scintillation detector as a hybrid Compton camera that can produce high-quality prompt γ ray images. The LaBr3:Ce detectors (Saint-Gobain Crystals) have outstanding timing resolution (< 350 ps), great energy resolution (< 2.5 % at 1332 keV), and a higher maximum energy range. The goal is to use the strengths of the LaBr3:Ce detectors to offset some of the limitations of the Polaris-J detector.

Dual radioisotopes simultaneous SPECT of (99m)Tc-tetrofosmin and (123)I-BMIPP using a semiconductor detector.

The energy resolution of a cadmium-zinc-telluride (CZT) solid-state semiconductor detector is about 5%, and is superior to the resolution of the conventional Anger type detector which is 10%. Also, the window width of the high-energy part and of the low-energy part of a photo peak window can be changed separately. In this study, we used a semiconductor detector and examined the effects of changing energy window widths for (99m)Tc and (123)I simultaneous SPECT. The energy "centerline" for (99m)Tc was set at 140.5 keV and that for (123)I at 159.0 keV. For (99m)Tc, the "low-energy-window width" was set to values that varied from 3% to 10% of 140.5 keV and the "high-energy-window width" were independently set to values that varied from 3% to 6% of 140.5 keV. For (123)I, the "low energy-window-width" varied from 3% to 6% of 159.0 keV and the high-energy-window width from 3% to 10% of 159 keV. In this study we imaged the cardiac phantom, using single or dual radionuclide, changing energy window width, and comparing SPECT counts as well as crosstalk ratio. The contamination to the (123)I window from (99m)Tc (the crosstalk) was only 1% or less with cutoffs of 4% at lower part and 6% at upper part of 159KeV. On the other hand, the crosstalk from (123)I photons into the (99m)Tc window mostly exceeded 20%. Therefore, in order to suppress the rate of contamination to 20% or less, (99m)Tc window cutoffs were set at 3% in upper part and 7% at lower part of 140.5 KeV. The semiconductor detector improves separation accuracy of the acquisition inherently at dual radionuclide imaging. In, this phantom study we simulated dual radionuclide simultaneous SPECT by (99m)Tc-tetrofosmin and (123)I-BMIPP. We suggest that dual radionuclide simultaneous SPECT of (99)mTc and (123)I using a CZT semiconductor detector is possible employing the recommended windows.

Performance Test and Evaluation for Pixel CdZnTe Detector of Different Thickness

Cadmium zinc telluride (CZT) material is one of the preferred materials for the fabrication of X-ray and gamma-ray detector. In this paper, it is presented an experimental detector system based on pixellated CZT semiconductor detector. The aim of this study is to get the photon energy suitable for different thickness detector, different photon energy acts on pixel CdZnTe detector of different thickness. We can obtain the energy spectrum estimation, energy resolution and peak efficiency by the experiment and simulation with the radiation source of 241Am and 137Cs acting on pixel CdZnTe detector. From experiment results, it can be found that at the high energy of 662keV the thicker CdZnTe detector is high. The characteristic of detector is better at the low energy when the detector thickness is thinner.

Experiments and Evaluation Based Pixellated CZT Semiconductor Detector

Cadmium zinc telluride (CZT) material is one of the preferred materials for the fabrication of X-ray and gamma-ray detector. In this paper, it is presented an experimental detector system based on pixellated CZT semiconductor detector. At the same time, some research and design on the surface signal-readout method and the preamplifier circuitry is made. The signal coming from the CdZnTe material exposed to the radiation through the experiment is successfully required. The collection-efficiency between the electron and the hole in the anode is test when the different bias is applied in the pixellated CZT semiconductor detector. The parameter of the CZT detector and validate the responsive effect for the radiation is evaluated.The experiments and evaluation basis for the development of subsequent gamma spectrometer.

Photon counting spectral CT: improved material decomposition with K-edge-filtered x-rays

Photon counting spectral computed tomography (PCSCT) provides material selective CT imaging at a single CT scan and fixed tube voltage. The PCSCT data are acquired in several energy ranges (bins) arranged over the x-ray spectrum. The quasi-monoenergetic CT images are acquired in these energy bins and are used for material decomposition. The PCSCT exhibits inherent limitations when material decomposition is performed using energy bins. For effective material decomposition, the energy bins used for material decomposition should be sufficiently narrow and well separated. However, when narrow bins are used, a large fraction of the detected x-ray counts is lost and statistical noise is increased. Alternatively, the x-ray spectrum can be split into a few larger bins with no gap in between and all detected x-ray photons can be used for material decomposition. However, in this case the energy bins are too wide and not well separated, which results in suboptimal material decomposition. The above contradictory requirements can be resolved if the x-ray photons are physically removed from the regions of the energy spectrum between the energy bins. Such a selective removal can be performed using filtration of the x-ray beam by high-Z filter materials with appropriate positions of K-edge energies. The K-edge filtration of x-rays can, therefore, provide necessary gaps between the energy bins with no dose penalty to the patient. In the current work, we proposed using selective K-edge filtration of x-rays in PCSCT and performed the first experimental investigation of this approach. The PCSCT system included a cadmium zinc telluride semiconductor detector with 2 × 256 pixels and 1 × 1 mm2 pixel size, and five energy bins. The CT phantom had 14 cm diameter and included contrast elements of iodine, gold and calcifications with clinically relevant concentrations. The tube voltages of 60, 90 and 120 kVp were used. K-edge filters based on Ba (Ek = 37.44 keV) were used for a 60 kVp tube voltage and Gd (Ek = 50.24 keV) was used for the 90 and 120 kVp tube voltages, respectively. The material selective CT images were also acquired with conventional Al filtration for comparison. The half-value layers of x-ray beams after K-edge and Al filtration were matched. The mean entrance skin exposure was 280 mR for all tube voltages and filters. The contrast-to-noise ratio (CNR) in material-decomposed images was approximately 30%–50% higher when K-edge filters were used instead of Al filters. It was concluded that K-edge filtration of x-rays provides substantial improvement of the CNR in material-selective PCSCT. Further optimization of K-edge filter materials, tube voltages, detector technology and energy bin settings will provide even higher CNR in decomposed images.

Detective Quantum Efficiency [DQE(0)] of CZT Semiconductor Detectors for Digital Radiography

In this paper, the detective quantum efficiency (DQE) of cadmium zinc telluride (CZT) detector samples for digital radiography has been measured. Specifically, this study is aimed at investigating the zero-frequency DQE(0) under different X-ray tube and detector parameters. The experimental results of this study indicate that the DQE(0) of the CZT samples is strongly dependent upon the irradiation geometry. This is attributed to the incomplete charge collection process, which can be further improved by controlling the purity of the samples and the contact type.