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1065-QQ04-08

Fabrication and Characterization of Individually Controlled Multi-Pixel Carbon Nanotube Cathode Array Chip for Micro-RT Application for Cancer Research Sigen Wang1,2, Zhijun Liu2, Lei An2, Otto Zhou2,3, and Sha Chang1 1 Department of Radiation Oncology, University of North Carolina, Chapel Hill, NC, 27599 2 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC, 27599 3 Curriculum of Applied and Materials Sciences, University of North Carolina, Chapel Hill, NC, 27599 ABSTRACT We report here the development of a new carbon nanotube (CNT) field emission multi-pixel cathode array chip, a vital component for the multi-pixel beam x-ray micro-radiotherapy (microRT) system under development in our group for cancer research. The CNT field emission cathode array chip has up to 25 (5 x 5) individually addressable cathode pixels, each 1 mm in diameter and with center-to-center distance of 2 mm. The fabrication is a two-step process: first a Cr/Cu electrical contact was fabricated on Si substrates with a 5 µm SiO2 dielectric layer using photolithography; and second the CNTs were selectively deposited on 1 mm-diameter predefined Cr/Cu contact dots by using a combined photolithography/electrophoresis deposition technique. The electron pixel beams produced from the multi-pixel array chips are uniform and individually controllable. Each pixel beam is expected to generate a dose rate in the order of 100 cGy/min based on our Monte Carlo simulations.

INTRODUCTION Today there are several types of small animal imaging systems commercially available including micro-CT, micro-MRI, and micro-CT-PET. However, the development of therapeutic tool for small animal models for cancer research, falls far behind. Currently there are a few groups working on development of micro-radiotherapy (micro-RT) systems using Ir-192 isotope [1] and conventional x-ray sources [2]. We have proposed a carbon nanotube (CNT) field emission based multi-pixel x-ray beam array micro-RT system. The key difference between ours and other micro-RT systems is that arbitrary shaped radiation field is formed by many individually controllable x-ray pixel beams in our system, while fixed-shaped radiation field of other systems is formed by mechanical collimation of a single broad beam. Intensity modulation and gated radiation that would be extremely difficult in other micro-RT systems [1, 2] can be achieved by electronic control in our micro-RT system. Once developed we will integrate the micro-RT system with the CNT field emission micro-CT already developed by our group to form a high resolution CT image-guided and intensity-modulated irradiation system at the mouse scale that is analogous to state of the art clinical image-guided radiotherapy system. CNT field emission technology has been successfully used by our group to develop new radiographic imaging devices to meet the current and future needs in both cancer biology research and clinical application [3-10]. We are applying the same CNT field emission technology to develop the