FDA Approves First CT System Based On Photon Counting
September 30 saw the U.S. Food and Drug Administration (FDA) approve the Siemens Naeotom Alpha, the first CT scanner in the world that counts photons.
It is the biggest shift in CT technology for this workhorse radiology modality in years. According to both the FDA and CT experts, the development represents the start of a revolution in CT scanner technology.
Laurel Burk, PhD, assistant director of the Diagnostic X-ray Systems Team in the FDA’s Center for Devices and Radiological Health, said in a press release:
“Computed tomography is an important medical imaging tool that can aid in diagnosing disease, trauma or abnormality; planning and guiding interventional or therapeutic procedures, and monitoring the effectiveness of certain therapies. Today’s action represents the first major new technology for computed tomography imaging in nearly a decade and underscores the FDA’s efforts to encourage innovation in areas of scientific and diagnostic progress.”
This device uses the newly emerging photon-counting technology of CT detectors, which measures each individual X-ray photon passing through a patient’s body, but does not use the technology used in current devices, which measure the total energy of several photons at once.
Each photon in the X-ray can be counted in order to obtain detailed information about the patient, so that less unhelpful information, like image noise, is included in the images.
New photon-counting detectors offer advantages over conventional CT detectors because of their active detection layers. The current CT technique uses a scintillator layer within the detector to convert X-ray photons into visible light, and then photo diode sensors transform the visible light into digital signals. As a result, energy information about the X-rays is lost and can no longer aid in diagnosis, as well as contrast being reduced, leading to less clear images.
With photon-counting detectors, X-rays are directly converted into electrical current, so no visible light is needed to detect them. Based on different kilovolt (kV) energy levels, the thresholds of each pulse can be collected and binned as appropriate. The formula creates dual-energy, spectral imaging data, which improves contrast and sharpens images, and direct conversion assists with decreases in information loss and improves image quality.