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A new era of image clarity: How can PCCT technology improve image quality?
With the rapid advancement of technology, the development of imaging medicine has also been constantly innovating.Among many technologies, photon counting computerized tomography (PCCT) is gradually becoming one of the important technologies for improving image quality.Unlike traditional energy integration detectors (EIDs), PCCT uses photon count detectors (PCDs) to register each photon's interactions individually.This innovation provides us with a new type of image detection capability and heralds a new vision for image diagnosis.
The advantage of PCCT is that it can improve the signal-to-noise ratio of the image, reduce the X-ray dose of the patient, improve spatial resolution, and even distinguish different contrast agents by using multiple energy intervals.According to the study, by January 2021, five clinical sites have used photon counting CT for imaging, and the U.S. Food and Drug Administration (FDA) has also approved the first clinically used PCCT system in September 2021.
The EID used in traditional CT can only measure the intensity of photons, which is equivalent to black and white photography, while PCD can record the energy of photons, which is similar to color photography.
Detection characteristics of PCCT
Discrete Energy Detection
The PCD can measure the resulting pulse amplitude based on the energy of each photon, which makes it feasible to filter unnecessary signals using low energy thresholds.By contrast, EID is not aware of the contribution of each photon and is therefore vulnerable to noise.
Image using PCD can provide higher signal-to-noise ratio and contrast than EID, which means that image quality can be increased at the same X-ray exposure level or lower patient X-ray dose to maintain images quality.
Multi-energy, spectral detection
PCD can set multiple energy thresholds to divide the energy of each photon.This is crucial for quantitatively judging the material composition of each pixel and for removing beam hardening artifacts.In addition, the advantage of this technology is that it can distinguish different contrast agents and further reduce the X-ray dose.
By using more than two energy thresholds, better material decomposition can be achieved and higher contrast and clarity can be demonstrated in the image.
Technical Challenges and Image Reconstruction
Although PCCT technology has several advantages, it faces challenges in its development.Especially for the requirements of materials and electronic equipment, coupled with performance under high data volume and counting rates, many obstacles have been created.For example, in a scan, hundreds of millions of photon interactions may be received per square millimeter, which requires the detector to have ultra-fast pulse resolution time.
Image reconstruction
Even if there are the above challenges, the data obtained by PCD can still be reconstructed using traditional CT reconstruction techniques.The use of multiple energy intervals opens up new reconstruction technology possibilities, such as reconstructing each energy interval independently to obtain different images.
Through material decomposition technology, the material composition of each pixel can be converted into a linear combination of known substances, further improving the image quality.
Future Outlook
At present, experimental PCDs are mainly based on semiconductor detectors, and the different materials of these detectors will affect their performance.With the advancement of technology, higher performance and more accurate photon counting systems may appear in the future, which will make PCCT technology play a more important role in imaging medicine.
Can we expect that PCCT technology will change our understanding of imaging quality in the near future and lead a new trend in imaging medicine?
