Oncology Publications
Title
The effects of field-of-view and patient size on CT numbers from cone-beam computed tomography.
Document Type
Article
Publication Date
10-21-2009
Journal
Physics in Medicine and Biology
Volume
54
Issue
20
First Page
6251
Last Page
6262
URL with Digital Object Identifier
http://dx.doi.org/10.1088/0031-9155/54/20/014
Abstract
Cone-beam computed tomography (CBCT) is used for patient alignment before treatment and is ideal for use in adaptive radiotherapy to account for tumor shrinkage, organ deformation and weight loss. However, CBCT images are prone to artifacts such as streaking and cupping effects, reducing image quality and CT number accuracy. Our goal was to determine the optimum combination of cone-beam imaging options to increase the accuracy of image CT numbers. Several phantoms with and without inserts of known relative electron densities were imaged using the Varian on-board imaging system. It was found that CT numbers are most influenced by the selection of field-of-view and are dependent on object size and filter type. Image acquisition in half-fan mode consistently produced more accurate CT numbers, regardless of phantom size. Values measured using full-fan mode can differ by up to 7% from planning CT values. No differences were found between CT numbers of all phantom images with low and standard dose modes.
