Tiezhi Zhang PhD, Presenter: Nothing to Disclose

Xiaochao Xu PhD, Abstract Co-Author: Nothing to Disclose

Joshua Kim, Abstract Co-Author: Nothing to Disclose

Cone beam computed tomography (CBCT) is an important online imaging modality for image guided radiotherapy (IGRT). The image quality of CBCT is however significantly inferior to and radiation exposure is greatly larger than diagnostic CT system. The major problems of CBCT system include excessive scatter, inferior detector performance, data truncation, approximate cone reconstruction, etc. The inferior image quality hinders the implementation of advanced IGRT treatment techniques. We are developing a novel tetrahedron beam computed tomography (TBCT) system which can significantly improve image quality and thereby the precision of radiation treatments.

With a single axial rotation, the volumes enclosed by a cone (pyramid) and tetrahedron are exactly the same. Hence a volumetric CT scan can also be achieved by rotating a tetrahedron, which is formed by a linear x-ray source array and a linear detector array that are orthogonal to each other. In TBCT, scatter photons are mostly rejected due to the fan beam geometry. Image quality is further improved by the use of high quality solid-state CT detector. Approximate FDK cone reconstruction artifact can be mitigated using iterative image reconstruction algorithm.

A TBCT benchtop system has been developed with a 75 pixel carbon nanotube field emission x-ray tube and an in-house developed CT detector array. Iterative image reconstruction algorithm was developed. The system produced excellent CT images which is superior to that of commercial CBCT scanners and close to that of diagnostic CT scanners.

TBCT is able to produce image quality close to diagnostic CT scanners. Clinical implementation of TBCT in IGRT can improve the precision of radiation treatments. Due to its superior image quality and compact geometry, C-arm TBCT can also be used as low-cost, mobile diagnostic CT scanners.

The superior image quality of TBCT facilitates advanced IGRT techniques such as online, offline adaptive radiotherapy and dose painting.

Zhang, T, Xu, X, Kim, J, Tetrahedron-Beam Computed Tomography (TBCT): Next Generation Online Imaging System for Image-guided Radiotherapy.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11010005.html