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Task Equivalence for Model and Human-Observer Comparisons in SPECT Localization Studies

Lookup NU author(s): Dr Anando SenORCiD


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While mathematical model observers are intended for efficient assessment of medical imaging systems, their findings should be relevant for human observers as the primary clinical end users. We have investigated whether pursuing equivalence between the model and human-observer tasks can help ensure this goal. A localization receiver operating characteristic (LROC) study tested prostate lesion detection in simulated In-111 SPECT imaging with anthropomorphic phantoms. The test images were 2D slices extracted from reconstructed volumes. The iterative ordered sets expectation-maximization (OSEM) reconstruction algorithm was used with Gaussian postsmoothing. Variations in the number of iterations and the level of postfiltering defined the test strategies in the study. Human-observer performance was compared with that of a visual-search (VS) observer, a scanning channelized Hotelling observer, and a scanning channelized nonprewhitening (CNPW) observer. These model observers were applied with precise information about the target regions of interest (ROIs). ROI knowledge was a study variable for the human observers. In one study format, the humans read the SPECT image alone. With a dual-modality format, the SPECT image was presented alongside an anatomical image slice extracted from the density map of the phantom. Performance was scored by area under the LROC curve. The human observers performed significantly better with the dual-modality format, and correlation with the model observers was also improved. Given the human-observer data from the SPECT study format, the Pearson correlation coefficients for the model observers were 0.58 (VS), −0.12 (CH), and −0.23 (CNPW). The respective coefficients based on the human-observer data from the dual-modality study were 0.72, 0.27, and −0.11. These results point towards the continued development of the VS observer for enhancing task equivalence in model-observer studies.

Publication metadata

Author(s): Sen A, Kalantari F, Gifford HC

Publication type: Article

Publication status: Published

Journal: IEEE Transactions on Nuclear Science

Year: 2016

Volume: 63

Issue: 3

Pages: 1426-1434

Print publication date: 01/06/2016

Online publication date: 13/05/2016

Acceptance date: 07/03/2016

ISSN (print): 0018-9499

ISSN (electronic): 1558-1578

Publisher: IEEE


DOI: 10.1109/TNS.2016.2542042


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