@inproceedings{discovery10052278,
            year = {2016},
           title = {Effects of the Collimator Magnification Factor in the Geometrical Calibration of SPECT Systems},
       publisher = {IEEE},
         journal = {2016 IEEE NUCLEAR SCIENCE SYMPOSIUM, MEDICAL IMAGING CONFERENCE AND ROOM-TEMPERATURE SEMICONDUCTOR DETECTOR WORKSHOP (NSS/MIC/RTSD)},
           month = {January},
          series = {IEEE Nuclear Science Symposium and Medical Imaging Conference},
       booktitle = {Proceedings of the 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD)},
            note = {This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.},
         address = {Strasbourg, France},
            issn = {1082-3654},
          author = {Salvado, D and Erlandsson, K and Hutton, BF},
        abstract = {In compact systems, precise measurement in the
projection space may be compromised due to minification.
The objective of this work is to investigate the impact of the
magnification factor in a model-based calibration procedure. This
has direct relevance to the geometrical calibration of the clinical
INSERT camera.
Projection data from three point sources were simulated for a
single pinhole collimator with magnification and single pinhole
and slit-slat collimators with minification, for 100 noise realizations
and 3 count levels. Model-based calibration was performed
to estimate geometric parameters and data corresponding to
a Derenzo phantom were simulated and reconstructed with
true and worst-case estimates for each collimator. Experimental
projection data were acquired with an INSERT prototype
camera and four 99mTc line sources in different locations within
the FoV. The collimator-CoR distance was varied in order to
obtain different minifications and model-based calibration was
performed.
The results from the simulations suggest that calibration is
less robust when minification is present, with higher biased
calibration parameters, which result in activity underestimation.
For experimental data, estimated parameters improved with a
higher magnification factor, in line with the simulation results.
However, some inconsistencies in the results suggest that there is
still room for improvements.
To conclude, geometric calibration of SPECT systems is more
sensitive to minification than magnification, which will impact
image quality.},
             url = {http://dx.doi.org/10.1109/NSSMIC.2016.8069589},
        keywords = {Science \& Technology, Technology, Physical Sciences, Life Sciences \& Biomedicine, Engineering, Electrical \& Electronic, Nuclear Science \& Technology, Physics, Applied, Radiology, Nuclear Medicine \& Medical Imaging, Engineering, Physics, geometrical calibration, minification, SPECT/MR, PINHOLE SPECT, RECONSTRUCTION}
}