Photon-Counting CT: High Resolution, Less Radiation

Abstract

Why Is This an Important Area of Interest? CT scanners play an essential role as medical imaging devices for screening, diagnosis, and monitoring of various health conditions. Photon-counting CT (PCCT) is an emerging medical technology that can improve image quality with less radiation exposure. Although Health Canada has licensed certain PCCT scanners for use, it remains unclear whether PCCT currently has a place in care. What Is the Technology? PCCT uses a semiconductor material to directly convert each incident photon into an electrical signal. The detector can quickly read out and “count” each individual photon. By directly detecting each X-ray photon and its energy level, PCCT scans can provide a clearer image. What Is the Potential Impact? PCCT is intended to function like conventional CT (i.e., scanning various anatomical structures for the purpose of screening, diagnosing, and monitoring health conditions). Any person requiring a CT scan could potentially be eligible for a PCCT scan. PCCT requires less time to complete a scan versus a conventional system. This could increase the number of CT scans a health care organization can conduct per day, if there are resources available to operationalize the additional capacity (e.g., health care personnel). We identified evidence that suggests, with a few exceptions, PCCT can provide similar or improved image quality and reduced image noise with often reduced radiation doses compared to conventional CT. It remains unclear whether this results in improvements in key health outcomes. The increased image quality may also increase incidental findings (e.g., incidentalomas), most of which are not clinically relevant. Compared to conventional CT, trends indicate higher or similar diagnostic confidence among clinicians and improved comfort for patients with PCCT. Trends also suggest PCCT may be valuable at improving the ability to diagnose or detect key markers of certain health conditions or diseases, especially for lung conditions. PCCT may offer particular benefits to children, people who require frequent CT scans, and people living with overweight or obesity. What Else Do We Need to Know? PCCT scanners cost 3 to 5 times more than conventional CT scanners. Additional clinical trials to investigate whether the higher resolution and lower radiation doses result in downstream improvements in key health outcomes are imperative to determine if the additional cost of PCCT scanners is justified. To comprehensively assess whether PCCT should be implemented for clinical use in Canada, additional information on certain implementation factors — such as training requirements and implications of dual-machine exposure, user perceptions, accessibility, and its overall place in care — is needed.