Xiaochao Xu PhD, Presenter: Nothing to Disclose

Derek Schulze, Abstract Co-Author: Nothing to Disclose

Joshua Kim, Abstract Co-Author: Nothing to Disclose

Tiezhi Zhang PhD, Abstract Co-Author: Nothing to Disclose

Cone-beam computed tomography (CBCT) is an important online imaging modality for image-guided radiotherapy (IGRT). However, the image quality of current CBCT systems is significantly inferior to that of diagnostic fan beam CT systems due to excessive scatter and suboptimal detector performance. In order to improve image quality, we are developing a novel Tetrahedron Beam Computed Tomography (TBCT) imaging system that will achieve similar diagnostic quality as helical CT scanners. A TBCT benchtop system is under development using a linear scan x-ray tube and a multi-row detector array.

The TBCT imaging system is comprised of a linear scan x-ray source and a linear discrete x-ray detector array. An x-ray tube with 75 carbon nanotube field emission cathodes is manufactured at XinRay Inc. The scanning range is 30 cm with 4 mm cathode spacing. A multi-row linear CT detector comprising 220 x 5 pixels is being built with Hamamatsu photodiode arrays and CdWO4 scintillation crystals. The system control and data collection are being implemented with an FPGA board for easy configuration and control. An FDK TBCT reconstruction algorithm has been developed. The axes of the linear x-ray tube and the detector array are aligned perpendicular to and within the rotation plane, respectively. The linear x-ray source and linear detector form a tetrahedral volume. The x-ray beams are narrowly collimated into fan beams and focused to the linear detector array. Multi-slot collimators are machined using a laser cutting technique.

The benchtop system will be completed within a few months. Due to its scatter rejection mechanism and the use of high-performance discrete x-ray detectors, TBCT image quality is expected to be comparable to that of diagnostic fan beam CT. However, due to the limited x-ray tube output, the scanning time needs to be prolonged.

TBCT would significantly improve online image quality. Clinical implementation of TBCT would improve the precision and reduce x-ray exposure in IGRT treatments. A higher power linear scan x-ray tube is needed in order to complete a scan within a clinically acceptable period.

 

Xu, X, Schulze, D, Kim, J, Zhang, T, Development of Tetrahedron Beam Computed Tomography Benchtop System.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8003372.html