A carbon nanotube field emission multipixel x-ray array source for microradiotherapy application.

The authors report a carbon nanotube (CNT) field emission multipixel x-ray array source for microradiotherapy for cancer research. The developed multipixel x-ray array source has 50 individually controllable pixels and it has several distinct advantages over other irradiation source including high-temporal resolution (millisecond level), the ability to electronically shape the form, and intensity distribution of the radiation fields. The x-ray array was generated by a CNT cathode array (5×10) chip with electron field emission. A dose rate on the order of >1.2 Gy∕min per x-ray pixel beam is achieved at the center of the irradiated volume. The measured dose rate is in good agreement with the Monte Carlo simulation result.

Improvement of Electron Field Emission in Patterned Carbon Nanotubes by High Temperature Hydrogen Plasma Treatment.

In this paper, we report a significant improvement of electron field emission property in patterned carbon nanotubes films by using a high temperature (650 °C) hydrogen plasma treatment. This treatment was found to greatly increase the emission current, emission uniformity and stability. The mechanism study showed that these enhanced properties are attributed to the lowering of the potential barrier and the creation of geometrical features through the removal of amorphous carbon, catalyst particles and the saturation of dangling bonds after such a hydrogen plasma treatment.

Fabrication and Characterization of Individually Controlled Multi-Pixel Carbon Nanotube Cathode Array Chip for Micro-RT Application for Cancer Research.

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 (micro-RT) system under development in our group for cancer research. The CNT field emission cathode array chip has up to 25 (5 × 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 SiO(2) 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.

A novel high resolution micro-radiotherapy system for small animal irradiation for cancer research.

Micro-radiotherapy (micro-RT) system is specially designed for small animal (cancer cell) irradiation for basic and translational cancer research. We use carbon nanotube (CNT) field emission technology to develop a novel micro-RT system for image-guided high precision irradiation that is similar to the state of the art radiotherapy which our cancer patients receive today at mouse scale. Through the field emission control of its individually addressable x-ray pixel beams the micro-RT system electronically shapes the radiation field and forms intensity modulation pattern. In this paper, we present the development of a carbon nanotube field emission cathode array chip--a key component for our novel micro-RT system. The prototype micro-RT CNT field emission cathode array chip has 5 x 5 individually addressable cathode pixels that are 1 mm in diameter and 2 mm in pitch. An individual CNT cathode pixel is predicted to generate a dose rate in the order of 100 cGy/min at the center of the irradiated mouse based on our Monte Carlo simulation. The temporal and spatial resolutions of the micro-RT system are expected to be approximately ms level and < 2 mm respectively.