DocumentCode :
3534878
Title :
Simple ROI cone-beam computed tomography
Author :
Maass, Clemens ; Knaup, Michael ; Sawall, Stefan ; Kachelriess, Marc
Author_Institution :
Inst. of Med. Phys. (IMP), Univ. of Erlangen-Nurnberg, Erlangen, Germany
fYear :
2010
fDate :
Oct. 30 2010-Nov. 6 2010
Firstpage :
3161
Lastpage :
3168
Abstract :
In classical x-ray CT the diameter of the field of measurement (FOM) must not fall below the transversal diameter of the patient or specimen. Thereby, the ratio of the the diameter of the FOM and the number of transversal detector elements typically defines the spatial resolution. We aim to improve the spatial resolution within a region of interest (ROI) by a factor of 10 to 100 while maintaining artifact-free CT image reconstruction inside and outside the ROI. Two novel methods are proposed for artifact-free reconstruction of the truncated ROI scan (data weighting method and data filtering method) and compared with the gold standard (data completion method) for this problem. First, an overview scan with low spatial resolution and a large FOM that exceeds the object transversally is performed. Second, a high resolution scan is performed where the scanner´s magnification is changed such that the FOM matches the ROI at the cost of laterally truncated projection data. The gold standard is forward projecting the low resolution scan on the rays missing in the high resolution scan. We propose the data filtering method, which uses the low resolution reconstruction and calculates a high frequency correction term from the high resolution scan, and the data weighting method, which reconstructs the truncated high resolution data and calculates a detruncation image from the low resolution data. The methods are compared using a simulation of the Forbild head phantom and a measurement of a spinal disk implant. The results of the data weighting method and the data completion method show the same image quality. The data filtering method yields inferior image quality because artifacts (partial volume effect, noise) of the overview scan propagate into the ROI reconstruction. Both new methods considerably outperform the data completion method regarding the computational load. The new ROI reconstruction methods are superior to the gold standard regarding the computational load. Compar- - ing the image quality with the gold standard, the data filtering method is inferior and the data weighting method yields equal quality.
Keywords :
computerised tomography; image reconstruction; medical image processing; phantoms; artifact-free CT image reconstruction; classical X-ray CT; computational loading; cone-beam computed tomography; data completion method; data filtering method; data weighting method; forbild head phantom; gold standard; high resolution scan; image detruncation; laterally truncated projection data; low resolution reconstruction; low resolution scan; spinal disk implant; transversal detector elements; Computed tomography; Detectors; Image reconstruction; Phantoms; Spatial resolution; Trajectory; Computed Tomography (CT); Region of interest imaging; spatial resolution;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE
Conference_Location :
Knoxville, TN
ISSN :
1095-7863
Print_ISBN :
978-1-4244-9106-3
Type :
conf
DOI :
10.1109/NSSMIC.2010.5874385
Filename :
5874385
Link To Document :
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