Using an investigational CT scanner which uses a new type of detector to capture X-rays, (a photon counting CT detector), the goal of this experimental study is to compare conventional CT images to CT images using the photon counting detector in patients undergoing CT scans for clinically indicated reasons. The main question it aims to answer is whether the images produced using the new detectors are superior in quality. Participants will undergo the clinically indicated CT images and the photon counting detector CT images of a limited area during the same examination time.

NIH develops new imaging techniques as one of its priorities for accelerating science, including methods for non-invasive patient assessments. Computed tomographic (CT) imaging is a mainstay of diagnostic imaging. The latest major technological advance is photon counting CT (PCCT) which uses a new x-ray detector that measures x-ray penetration of the body and the energy of each x-ray photon. NIH Clinical Center will use a prototype Siemens PCCT CounT systems built for clinical investigational use. The scanner can perform standard CT and PCCT imaging. In this protocol, NIH patients already enrolled in a clinical research protocol and who are referred to Radiology for diagnostic CT as part of that research may be enrolled in this study of PCCT. The diagnostic CT scan requested by their medical care team will be performed on the CounT scanner, providing the clinically indicated imaging, along with a single abbreviated PCCT exam of an organ or body part to support PCCT feasibility of the PCCT to provide better images in several small groups of patients with selected medical conditions. The data will be used to characterize quality of the PCCT images and to develop testable hypotheses and new diagnostic applications using PCCT capabilities.

Current CT systems, such as the Siemens SOMATOM Flash, have two x-ray tubes, each paired with an x-ray detector that measures total x-ray penetration of the patient and uses that information to create the images. The CounT scanner is a modified version of the Flash in which one of the two standard detectors has been replaced with a PCCT detector. The two imaging modes for the CounT scanner are (i) standard detector study as in a Flash scanner and (ii) PCCT scan. The patient scan will thus include clinically indicated radiation exposure with the standard detector and research radiation over a limited field with the PCCT detector. The CounT system is sited at the Clinical Center under a CRADA (Cooperative research and development agreement) with Siemens Medical Solutions.

Compared to current scanners, PCCT is expected to offer four major advantages:

• lower radiation dose
• greater spatial resolution
• reduced imaging noise
• x-ray energy discrimination

As a translational development protocol, all imaging studies are open-label and data may be analyzed as they are collected.

• INCLUSION CRITERIA:
• NIH patients currently on an NIH research protocol who are referred to RAD&IS for CT examination as part of that research protocol
• 18 years old or greater
• Able to understand and sign informed consent

EXCLUSION CRITERIA:

• Studies that specifically require simultaneous dual source CT scan capability or where dual source CT scan is requested
• Studies ordered for an emergency indication
• Pregnant women. Subjects of child-bearing potential will undergo serum or urine pregnancy testing within 72 hours before examination. Post-menopausal and surgically sterilized subjects are automatically exempt from this testing
• Lactating women who are unable to stop breast feeding for 24 hours following the administration of contrast
• Body weight >500 lbs (227 kg) or a body circumference that prevents the study subject from lying flat in the scanner
• Patients who have undergone PCCT examination within the past year.
• Any contraindications that the research team identifies from the subject, RAD&IS CT questionnaires, and/or History and Assessment
• Employees or staff supervised by the Principal Investigator or an Associate will not be recruited to participate

11 patients could not be scanned on the PCCT investigational scanner after being enrolled due to scanner downtime.

24 hours unanticipated events related to the device are apparent at the time of scanning

Events related to the diagnostic CT component are not reported. Unexpected incidental findings may be visible on the diagnostic scan read immediately or possibly only visible only on the PCCT research images which would be reviewed within 24 hours.

The PCCT detector and investigational CT scanner itself were in development at the time of the trial. The detector and scanner platform has been developed by industry since this time. These results are not predictive of the performance of the FDA approved PCCT scanner which was approved in October 2021.