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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, Amy; Szczepura, K.R.; Vinjamuri, S.; Hogg, P.


J.D. Thompson

Amy 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.

Journal Article Type Article
Publication Date Aug 31, 2017
Journal Radiography
Print ISSN 1078-8174
Electronic ISSN 1532-2831
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 23
Issue 3
Pages 191-196
Institution Citation 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:
Keywords PET/CT; Nodule detection; JAFROC


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