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On the comparison of FROC curves in mammography CAD systems
KTH, School of Engineering Sciences (SCI), Physics.
2005 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 32, no 2, 412-417 p.Article in journal (Refereed) Published
Abstract [en]

We present a novel method for assessing the performance of computer-aided detection systems on unseen cases at a given sensitivity level. The sampling error introduced when training the system on a limited data set is captured as the uncertainty in determining the system threshold that would yield a certain predetermined sensitivity on unseen data sets. By estimating the distribution of system thresholds, we construct a confidence interval for the expected number of false positive markings per image at a given sensitivity. We present two alternative procedures for estimating the probability density functions needed for the construction of the confidence interval. The first is based on the common assumption of Poisson distributed number of false positive markings per image. This procedure also relies on the assumption of independence between false positives and sensitivity, an assumption that can be relaxed with the second procedure, which is nonparametric. The second procedure uses the bootstrap applied to the data generated in the leave-one-out construction of the FROC curve, and is a fast and robust way of obtaining the desired confidence interval. Standard FROC curve analysis does not account for the uncertainty in setting the system threshold, so this method should allow for a more fair comparison of different systems. The resulting confidence intervals are surprisingly wide. For our system a conventional FROC curve analysis yields 0.47 false positive markings per image at 90% sensitivity. The 90% confidence interval for the number of false positive markings per image is (0.28, 1.02) with the parametric procedure and (0.27, 1.04) with the nonparametric bootstrap. Due to its computational simplicity and its allowing more fair comparisons between systems, we propose this method as a complement to the traditionally presented FROC curves. (C) 2005 American Association of Physicists in Medicine.

Place, publisher, year, edition, pages
2005. Vol. 32, no 2, 412-417 p.
Keyword [en]
FROC; confidence interval; mammography; CAD; bootstrap; sampling error; system threshold estimation
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-5393DOI: 10.1118/1.1844433ISI: 000227420800015ScopusID: 2-s2.0-14644427741OAI: diva2:9749
QC 20100818Available from: 2006-03-03 Created: 2006-03-03 Last updated: 2011-11-07Bibliographically approved
In thesis
1. Computer-aided detection and novel mammography imaging techniques
Open this publication in new window or tab >>Computer-aided detection and novel mammography imaging techniques
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis presents techniques constructed to aid the radiologists in detecting breast cancer, the second largest cause of cancer deaths for western women. In the first part of the thesis, a computer-aided detection (CAD) system constructed for the detection of stellate lesions is presented. Different segmentation methods and an attempt to incorporate contra-lateral information are evaluated.

In the second part, a new method for evaluating such CAD systems is presented based on constructing credible regions for the number of false positive marks per image at a certain desired target sensitivity. This method shows that the resulting regions are rather wide and this explains some of the difficulties encountered by other researchers when trying to compare CAD algorithms on different data sets. In this part an attempt to model the clinical use of CAD as a second look is also made and it shows that applying CAD in sequence to the radiologist in a routine manner, without duly altering the decision criterion of the radiologist, might very well result in suboptimal operating points.

Finally, in the third part two dual-energy imaging methods optimized for contrast-enhanced imaging of breast tumors are presented. The first is based on applying an electronic threshold to a photon-counting digital detector to discriminate between high- and low-energy photons. This allows simultaneous acquisition of the high- and low-energy images. The second method is based on the geometry of a scanned multi-slit system and also allows single-shot contrast-enhanced dual-energy mammography by filtering the x-ray beam that reaches different detector lines differently.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006
Trita-FYS, ISSN 0280-316X ; 2006:06
computer-aided detection, FROC, mammography, optimal operating points, single-shot dual-energy imaging
National Category
Radiology, Nuclear Medicine and Medical Imaging
urn:nbn:se:kth:diva-3861 (URN)91-7178-274-5 (ISBN)
Public defence
2006-03-10, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00
QC 20100819Available from: 2006-03-03 Created: 2006-03-03 Last updated: 2010-08-19Bibliographically approved

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