As everyone knows, cancer is one of the greatest health enemies of mankind and became a major public health problem all over the world. Moreover, lung cancer is the most common global cancer leading to more than 1.3 million estimated deaths annually worldwide. Breast cancer is the most common cancer and the 2nd leading cause of death from in women in the US, Canada, and China. Therefore an instrument for the early diagnosis and monitoring of cancers in areas such as lung and breast is immensely important and necessary.
The cadmium zinc telluride (CZT) semiconductor is a kind of novel radiation detector that can provide detailed information about spatial position. Also, the energy resulting from interactions between the radiation and the CZT material can also be assessed giving this type of detector added value in disease evaluation. A great deal of work on CZT detectors has been done for breast CT scanning. Furthermore, the CZT detector is also a potential solution for problems in lung cancer CT evaluation where the lack of energy information and high radiation exposure are less than ideal. Since sub-millimetre spatial resolution is required for post-contrast thoracic CT assessment, and $100~\mu m$ or better is critical for breast CT, the investigation of spatial resolution for CZT detectors is essential.
In this thesis, the interactions within CZT detectors were analyzed. The influence of different configurations, including adjustment of anode size, gap size, detector thickness and bias voltage, were discussed. Next the methods to evaluate two kinds of signals (collected and transit signals), are provided in Chapter~2. In Chapter~3, an intensity difference method and an intensity ratio method for estimating the sub-pitch spatial resolution were described in detail. Finally, a detector spatial resolution between $10~\mu m$ and $20~\mu m$ was achieved using the collecting signal intensities ratio method and a $4~mm$ thick CZT detector with gap size of $g=50~\mu m$ and bias voltage of $V=300V$.
Future work should focus on the contributions from characteristic X-rays emitted from cadmium and tellurium atoms. Also, the work presented was only on pixelated arrays and further assessment of cross-strip electrode detectors could also be of benefit. Lastly based on simulations done in this thesis all photons were assumed to strike the cathode at 90 degrees.
Future work should also include non-orthogonal directions for photons. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21082 |
| Date | January 2017 |
| Creators | Li, Yike |
| Contributors | Wu, Xiaolin, Electrical and Computer Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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