Translational Development of Photon-counting CT Imaging

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.

Enrolled patients may be scanned on the investigational Photon Counting CT scanner. Conventional images also obtained for comparison using the same scanner at the same time.

18 and older patients who undergo the conventional CT scan and the photon counting CT (PCCT) scan. Patient's images on the conventional scanner provide internal control to compare to the PCCT images.

Enrolled patients will undergo the requested clinical diagnostic CT study on the investigational system using the standard detector, with or without IV and/or oral contrast as indicated and an limited scan of one body region using the PCCT detector. Both scans are able to be performed on the same scanner during the same examination.

Mean difference in relative image quality grading of CT images using Photon counting detectors vs. conventional detectors in group of patients with various clinical conditions. Scale name "Visual grading analysis (VGA)" . Expert radiologist observers compare the relative grades of the images from the PCCT to the grades of the same patient's reference images from conventional CT acquired at the same time. The visual grading scale incorporates technical factors in the acquisition and image display (such as contrast, noise and presence of artifacts and post processing). Grading is based on 5 point scale. 1- lowest image quality, 5- highest image quality. 5 is a better result. Scale as follows: 1 Images not usable- severe limitations for diagnostic use, 2 Limited -some loss of information, significant limitations for clinical use, 3 Adequate -moderate limitations for diagnostic use, 4 Good-minimal limitations for clinical use, 5 Excellent- no limitations for clinical diagnosis.

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

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