A first generation compact microbeam radiation therapy system based on carbon nanotube X-ray technology

Abstract

We have developed a compact microbeam radiation therapy device using carbon nanotube cathodes to create a linear array of narrow focal line segments on a tungsten anode and a custom collimator assembly to select a slice of the resulting wedge-shaped radiation pattern. Effective focal line width was measured to be 131 lm, resulting in a microbeam width of $300 lm. The instantaneous dose rate was projected to be 2 Gy/s at full-power. Peak to valley dose ratio was measured to be >17 when a 1.4 mm microbeam separation was employed. Finally, multiple microbeams were delivered to a mouse with beam paths verified through histology. V C 2013 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4826587] More than half of cancer patients in North America rely on radiation therapy (RT) as part of their treatment plan.

A preclinical microbeam facility with a conventional x‐ray tube

“…Also x‐ray tubes have been suggested as a microbeam source 20 . Hadsell et al 21 experimentally realized a preclinical setup with carbon nanotube x‐ray tubes and produced 300 μ m wide microbeams with a dose rate of 21.7 mGy/s per nanotube cathode. At a source to target distance of apparently 25.4 cm, a PVDR of 17 was measured for four 1.4 mm spaced beams at 1.27 mm depth in PMMA.…”

Physiologically gated microbeam radiation using a field emission x‐ray source array

“…A microbeam peak dose rate of 2 Gy/s and average dose rate of 1.4 Gy/min are measured in the first generation CNT microbeam irradiator. 18 The average dose rate is expected to be increased to 20 Gy/min in the second generation device, currently under construction, with improved anode thermal management. Targeted delivery of the microbeam to the brain tumor site in mouse has been demonstrated using a combined MRI and onboard x-ray projection imaging procedure.…”

“…The specially designed linear CNT x-ray source array, as described in previous publications, 18 consists of a linear CNT cathode which emits electrons under a bias extraction field, a gating electrode, an electrostatic focusing lens to focus the electron beam, and an opposing stationary tungsten anode. The electron beam is focused down to a narrow 0.145 × 160 mm focal track on the anode.…”

“…18,19 The device utilizes a specially designed CNT xray source array made of individual units with long and narrow focal tracks to deliver the radiation simultaneously from different directions, instead of from a single point, to the region of interest. 18 An external collimator is used to collimate the radiation into a microbeam of adjustable beam width. A higher dose rate is achieved by distributing the electron energy over the long focal tracks with increased heat capacity when compared to conventional microfocus x-ray tubes.…”

“…The mean energy is 60 keV and the HVL was determined to be 7.5 mm Al. 18 The intrinsically divergent radiation is collimated into microbeam using a motorized microbeam collimator placed between the x-ray window and the object, 65.2 mm below the focal spot on the anode. In the present system, parallel planes of microbeams are delivered by translating the object in the direction perpendicular to the microbeam plane in a step and shoot fashion.…”