Cynthia McCollough, Ph.D., director of Mayo Clinic's CT Clinical Innovation Center, explains how photon-counting computed tomography (CT) detectors work and why it is a better technology over conventional CT systems. She helped Siemens develop the Naeotom Alpha, the first photo-counting CT system to be approved by the FDA in the fall of 2021. She spoke to ITN at the Radiological Society of North America (RSNA) 2021 annual meeting.
Read more about the first commercial photon-counting scanner
The device uses the emerging CT technology of photon-counting detectors, which can measure each individual X-ray photon that passes through a patient's body, as opposed to current systems which use detectors that measure the total energy contained in many X-rays at once. By "counting" each individual X-ray photon, more detailed information about the patient can be obtained and used to create images with less information that is not useful, such as image noise.
Current CT technology uses a two-step conversion process to convert X-ray photons into visible light using a scintillator layer in the detector. Then, photo diode light sensors turn the visible light into a digital signal. Due to this intermediate step, important information about the energy of the X-rays is lost and no longer available to aid in diagnosis. Also, contrast is reduced and images are not as clear.
Photon-counting detectors use a single step of direct conversion of X-rays into electrical current, and skips the step of converting X-rays into visible light. This allows the energy thresholds of each pulse to be collected and binned based on different kilovolt (kV) energy levels. This creates data to improve contrast and enable dual-energy, spectral imaging. The direct conversion also helps improve image quality without information loss. This improves image sharpness and contrast.
Photon-counting detectors have already been used for several years in high-energy physics and nuclear imaging. However, these previously generation photon-counting detectors could not be used with a clinical CT scanner because they could not keep up with the high higher rate of photons reaching the detector. The detector on the Naeotom Alpha was designed for this increased speed.
Related Photon-counting CT Content:
Mayo Clinic Begins Use of Third-Generation Photon-counting CT Clinical Research Detector
VIDEO: New Advances in CT Imaging Technology — Interview with Cynthia McCollough, Ph.D.
VIDEO: Photon Counting Detectors Will be the Next Major Advance in Computed Tomography — Interview with Todd Villines, M.D.
Key Trends in Cardiac CT at SCCT 2020
GE Healthcare Pioneers Photon Counting CT with Prismatic Sensors Acquisition
Top Trend Takeaways in Radiology From RSNA 2020
NeuroLogica Joins Forces with Massachusetts General Hospital to Pilot Photon Counting CT at the Patient’s Point-Of-Care Using OmniTom Elite CT
VIDEO: Advances in Cardiac CT Imaging — Interview with David Bluemke, M.D.
