Radiographic capsule imaging: A potential new technology for colon cancer screening
A new technology, an ingestible imaging capsule emitting ultra-low dose radiation that generates data as it passes naturally through the colon, is described in an article published in the January issue of Abdominal Radiology. Acquired data are reconstructed into 2D and 3D images of the colonic lumen for interpretation by a radiologist or gastroenterologist. Its potential appeal to an individual is that the unpleasant process of emptying the colon is not required.
The system being developed by Check-Cap of Mount Carmel, Israel, consists of an X-ray
emitter, a short-lived radioisotope, and X-ray detectors connected to single-photon counting electronics. The X-ray source is collimated and rotated to form three beams that scan when the capsule moves inside the colon. A microprocessor inside the capsule transmits data to a lightweight recorder worn on the body. The recorder tracks the 3D position and orientation of the capsule within the body.
After a patient swallows the 34mm L x 11mm D capsule, a small amount (50-70 mL daily) of an iodine-based water soluble contrast agent is ingested three times daily with meals to enable the contrast agent to mix with the contents of the colon. The capsule emits low-dose X-ray photons through its three collimated beams that together scan a full slice of the colon every third of a
rotation. The imaging resolution achieved can detect non-diminutive polyps 6 mm in size and larger. In addition to the single-photon detection, dual energy (X-ray fluorescence and Compton backscattering) data are used to reconstruct the colon surface from within. Imaging data and capsule position data are stored in the external recorder for transfer to a workstation for image reconstruction.
Proprietary 2D and 3D reconstruction software combines the X-ray fluorescence and Compton backscatter data to estimate distances from the capsule to the colon wall. A 2D slice is created with each location for the capsule position, and from these slices, 3D images are reconstructed.
Two preclinical studies involving 138 volunteers ranging in age from 41 to 70 years have been conducted. With the exception of one capsule recovered from the cecum of the colon of a volunteer, all passed through the body intact. The average radiation dose was 0.04 mSv. Perry J. Pickhardt, MD, professor of radiology and chief of gastrointestinal imaging at the University of Wisconsin School of Medicine and Public Health in Madison, and coauthors reported that “the 3D images revealed the typical structure and contour of different colonic segments, such as the hepatic flexure and the triangular shape of the transverse colon. Polyps seen in several of the volunteers were subsequently validated by conventional colonoscopy.”
The first of two multi-center prospective clinical trials being conducted to evaluate the clinical performance, efficacy and safety of the capsule system in detecting patients with polypoid lesions compared with optical colonoscopy was launched in January. This study will recruit 50 patients at the Tel Aviv Sourasky Medical Center and at three other medical centers in Israel. It is being conducted in support of Check-Cap’s CE Mark submission. A similar clinical trial is expected to be launched in the United States in late 2017 or in 2018 in support of clearance by the U.S. Food and Drug Administration (FDA).
REFERENCE
- Kimchy Y, Litshitz R, Lewkowitz S, et al. Radiographic capsule-based system for non-cathartic colorectal cancer screening. Abdom Radiol. 2017 Published online January 4, 2017