Characterization of a carbon nanotube x-ray source array for a multisource CBCT

Abstract

Preliminary results have shown replacing the conventional x-ray tube with a stack of narrowly collimated beams along the axial direction reduces scatter and improves the spatial uniformity and the CT number accuracy in CBCT. The purpose of this study was to evaluate a carbon nanotube (CNT) x-ray source array designed for a prototype multisource CBCT (ms-CBCT) for maxillofacial imaging. The CNT x-ray source array comprises 8 evenly distributed focal spots (“sources”), and 8 corresponding CNT cathodes and gate electrodes, with an inter-focal spot spacing of 12mm. A multisource collimator was designed to confine the radiation from each focal spot to a narrow cone beam covering a section of the object in the axial direction. The focal spot sizes (FSS) were measured using a pinhole camera setup following the IEC standard procedure. The radiation fields of the collimated beams were measured using a flat panel detector. The x-ray source cathode and tube currents were recorded, and radiation dose was measured with a dose meter. Preliminary 3D volumetric imaging of an anthropomorphic head phantom was conducted using the CNT source array. The targeted 15mA tube current was achieved from each focal spot at 110kVp. The measured FSS IEC nominal value was 0.7. The average x-ray cone angle of each collimated beam was 2.3°. The prototype CNT x-ray source array achieved the specifications for the oral and maxillofacial ms-CBCT scanner. Work is in progress to evaluate the imaging system.