RT Journal Article
SR Electronic
T1 Lag correction for flat-panel cone-beam CT in SPECT/CT
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 492
OP 492
VO 52
IS supplement 1
A1 Jiong Wang
A1 Eberhard Hansis
A1 Peter van de Haar
A1 David Sowards-Emmerd
A1 Joerg Bredno
A1 Lingxiong Shao
YR 2011
UL http://jnm.snmjournals.org/content/52/supplement_1/492.abstract
AB 492 Objectives Recently, flat-panel Cone-Beam CT (CBCT) with offset-detector geometry has been introduced in SPECT/CT imaging systems to provide localization and attenuation correction. In flat-panel X-ray detectors, there exist multiple detector effects (array lag, scintillator afterglow and brightburn), collectively referred to as “lag”, which lead to a temporal delay between X-ray incidence and signal readout. Lag causes characteristic arc-shaped artifacts in reconstructed images, as well as other more subtle artifacts. Efficient software based lag correction is therefore essential for improving image quality in flat-panel CBCT applications. Methods In this contribution we study lag artifact reduction by temporal deconvolution using a multi-exponent lag model. For each frame of X-ray incidence, the fraction of signal that is distributed onto subsequent frames is theoretically calculated and compensated. The method is evaluated on phantom and patient studies acquired on the CBCT component of a Philips BrightView XCT system, performed after detector dynamic gain correction. Results Phantom studies show that lag artifacts, typically seen in reconstructed images of rotationally asymmetric objects and objects positioned off-centered from the rotation axis, are reduced on average by 75%. Out of 280 evaluated patient studies, image quality was improved by lag correction in 73% of cases, while in only 2% of cases, degraded image quality was observed with lag correction. Typical image quality improvements in patient studies are reduction of arc-shaped lag artifacts and better uniformity between left and right body regions. The patient case evaluation also reveals that lag correction can reduce shading artifacts that are observed between two attenuating objects. Conclusions The computerized lag correction method described in this work improves image quality in flat-panel CBCT by effectively reducing lag-induced reconstruction artifacts