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A JAFROC study of nodule detection performance in CT images of a thorax acquired during PET/CT.

Thompson, J.D.; Wareing, A.; Szczepura, K.R.; Vinjamuri, S.; Hogg, P.


J.D. Thompson

A. Wareing

K.R. Szczepura

S. Vinjamuri

P. Hogg


Purpose - Two types of CT images (modalities) are acquired in PET/CT: for attenuation correction (AC) and diagnosis. The purpose of the study was to compare nodule detection and localization performance between these two modalities. Methods - CT images, using both modalities, of an anthropomorphic chest phantom containing zero or more simulated spherical nodules of 5, 8, 10 and 12 mm diameters and contrasts -800, -630 and 100 HU were acquired. An observer performance study using nine observers interpreting 45 normal (zero nodules) images and 47 abnormal images (1-3 nodules; average 1.26) was conducted using the free-response receiver operating characteristic (FROC) paradigm. Data were analysed using an R software package implemented jackknife alternative FROC (JAFROC) analysis. Both empirical areas under the equally weighted AFROC curve (wAFROC) and under the highest rating inferred ROC (HR-ROC) curve were used as figures of merit (FOM). To control the probability of Type I error test alpha was set at 0.05. Results - Nodule detection as measured by either FOM was significantly better on the diagnostic quality images (2nd modality), irrespective of the method of analysis, [reader averaged inter-modality wAFROC FOM difference = -0.07 (-0.11,-0.04); reader averaged inter-modality HR-ROC FOM difference = -0.05 (-0.09, -0.01)]. Conclusion - Nodule detection was statistically worse on images acquired for AC; suggesting that images acquired for AC should not be used to evaluate pulmonary pathology.


THOMPSON, J.D., WAREING, A., SZCZEPURA, K.R., VINJAMUN, S. and HOGG, P. 2017. A JAFROC study of nodule detection performance in CT images of a thorax acquired during PET/CT. Radiography [online], 23(3), pages 191-196. Available from:

Journal Article Type Article
Acceptance Date Mar 3, 2017
Online Publication Date Mar 22, 2017
Publication Date Aug 31, 2017
Deposit Date Apr 6, 2017
Publicly Available Date Mar 23, 2018
Journal Radiography
Print ISSN 1078-8174
Electronic ISSN 1532-2831
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 23
Issue 3
Pages 191-196
Keywords PET/CT; Nodule detection; JAFROC
Public URL


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