han.wen@nih.gov

The ultimate goal is to achieve near microscopic resolution in body CT scans in targeted areas in order to reduce invasive biopsy procedures. This trial specifically evaluates an add-on hybrid technology to whole-body CT scanners which can be readily disseminated to clinical scanners.

This trial included 8 patients suspected of lymphangioleiomyomatosis (LAM) (all female, age 33 to 64). Similar to the high sensitivity of surface coils in MRI due to their proximity to the body, in a CT scanner the proximity effect is exploited to overcome the resolution limit imposed by the x-ray focal spot penumbra. A surface panel detector insert (SDI) is placed in a foam frame on the scanner bed, in direct contact with the patient's body (Fig. 1). This minimizes the focal spot penumbra on the SDI. The SDI acquired data at 1000 Hz for 0.35 sec concurrent with the CT's own detector. The method was previously tested in phantoms with a photon-counting SDI of 100 µm pixels and 2048x256 matrix (Larsen et al., TOMOGRAPHY, 2:233-238, 2019). Axial-mode chest scans of 2 cm z length were performed. Data from the SDI and the CT's detector were combined in a prototype tomosynthesis software to produce a coronal image stack of 50 µm pixels and 0.1 mm slice spacing. System resolutions were measured by scanning tungsten wires.

Examples of structural details provided by the SDI hybrid scan (Fig.1) include bronchioles down to 0.6 mm diameter with walls of 0.15 to 0.35 mm thickness; air-filled lung cysts down to 1.1 mm size, some with walls down to 0.20 mm thickness; blood vessels down to 0.20 mm diameter; endplate micro fractures in thoracic vertebrae down to 0.10 mm scale. A first in vivo observation was made of a 0.35 mm diameter bronchiole that appears to terminate in a round cyst of 2.4 mm diameter with a distinct wall, offering clues to the mechanism of cyst formation in LAM. System resolutions and MTFs of scans with and without the SDI are summarized in Fig. 1.

Initial patient trial of an add-on surface detector in a whole-body CT scanner provided structural details in chest scans beyond the resolution limit of the scanner hardware. Current work focuses on data fusion methods for true 3D reconstruction.

Initial trial of an add-on surface detector to a whole-body CT scanner demonstrates structural details in the chest scans of patients with LAM beyond the resolution limit of the scanner.