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Effect of computer-aided diagnosis on radiologist performance: Database development and work in progress
and pretest patient characteristics. T a k e - H o m e P o i n t : I) The diagnostic thinking efficacy of a test is affected by the nature of the diagnostic test, t h e specific study results, and the clinician's pretest evaluation of patient characteristics. 2) Clinicians are not necessarily Bayesian.
8-61 Colorectal Polyp Detection with 3D Spiral CT Colography: Technical Evaluation of CT Imaging Pro. tocol--Work in Progress Elizabeth G. McFarland, MD, Mallinckrodt Institute of Radiology, Saint Louis, MO, James A. Brink, MD, Dennis M. Balfe, MD, Jay P. Heiken, MD P u r p o s e : Spiral CT colography provides a 3D endoscopic evaluation of the mucosal surface of the colon for detection of polyps. Our work to date has investigated the image acquisition parameters best snited to detect clinically significant polyps, and b o t h identify and minimize 3D artifacts. M e t h o d s : To evaluate image acquisition parameters, an in-vitro colon p h a n t o m consisting of an air-filled, s m o o t h polyethylene tube was subanerged in a water bath and s c a n n e d at various orientations relative to the z-axis at 3ram collimation]pitch 1.67, and 5ram collimation/pitch 1.6 for all orientations. Scans were also performed with pitch of 1.0 and 2.0 (at 45 degrees). Image analysis was performed on coronal reformations (MPR) and 3D volume rendered (VR) images. Results: Rippling artifacts were demonstrated along the s m o o t h p h a n t o m colon wall with both the coronal 2D MPR and in the 3D VR images. The z-height of the artifact was influenced by pitch and the transverse width was influenced by the angle deviation from the z axis. C o n c l u s i o n : Evaluation of image acquisition parameters is important to both optimize detection of colorectal polyps and discriminate artifacts w h i c h can mimic mucosal folds.
8-62 Reader Accuracy with Monitor Display of Digitized Film Mammograms J. Jeffrey Carl,, MD, Bowman Gray School of Medicine, WinstorvSalem, NC P u r p o s e : To compare reader accuracy for detecting breast cancer with film and with monitor display of m a m m o g r a m s . M e t h o d s : Sixty m a m m o g r a p h y studies w e r e randomly selected from a population of w o m e n o n the basis of disease status as proven by biopsy or follow-up. Films w e r e digitized at 50/a (10 l p / m m ) resolution and were displayed on high-resolution (2,048"2,560) and 4uminosity (60-80 fL) monitors. The probability of breast cancer was rated by a board-certified radiologist without knowledge of patient history or prior studies. R e s u l t s : Sensitivity, specificity, and accuracy were 1.00, 0.51, and 0.65 for film and 0.94, 0.49, and 0.62 for monitor display. Correct decisions were similar (film 65% vs. monitor 62%, difference NS). ROC curves had to AUC of 0.97 (film) and 0.88 (monitor). The 8.7% larger AUC for film is not statistically significant (p 0.14). C o n c l u s i o n s : This study demonstrates the feasibility of interpreting digitized screening m a m m o g r a m s at a c o m p u t e r workstation. Diagnostic accuracy with monitor display of high-resolution (10 l p / m m ) digital m a m m o g r a m s is comparable to convention film display. The 8.7% greater accuracy with film, although not significant in this preliminary study, is consistent with the hypothesized results given greater reader experience and higher spatial resolution (> 13 l p / m m ) of film. L e a r n i n g Objectives: 1. Gain greater tmderstanding of h o w the m e t h o d of image presentation (film or monitor display) affects the detection of breast cancer with m a m m o g r a p h y . 2. Assess the impact of monitor display (soft copy) on the participant's practice of radiology. (l. Jeffrey Cart's activities are supported through a GE-AUR Research Award.)
8-63 Effect of Computer-Aided Diagnosis on Radiologist Performance: Database Development and Work in Progress Dulcy E. Wolverton, MD, UniversiOy of Chicago, Chicago, IL P u r p o s e : To evaluate t h e effect of c o m p u t e r aided diagnosis (CAD) detection s c h e m e s indicating potential m a m m o g r a p h i c lesions on the performance of radiologists with variable experience. M e t h o d s : A large m a m m o g r a p h i c database has been developed to be used in an observer study that includes 5 attending radiologists with variable m a m m o g r a p h i c experience (up to expert) and 5 radiology residents with training in mammography. These cases have been digitized and analyzed using CAD lesion-detection schemes. The CAD output indicating the locations of potential masses or clustered microcalcifications for each case as applicable will be presented to t h e observers in an ROC study. Results: The database consists of 240 screening m a m m o g r a p h i c examinations. Of these, 160 are normal and the remaining 80 are abnormal (50% malignant). The normal cases include a broad representative m i x of difficult cases w h i c h could provoke False-positive detections by both radiologists and CAD. The lesions in the database consist of 40 subtle mass lesions and 40 subtle clusters of microcalcifications. Characterization of these lesions and the preliminary CAD performance results will be presented. C o n c l u s i o n : Successful development of a difficult, b u t predominantly normal, m a m m o g r a p h i c database for use in a large observer study that will evaluate the utility of CAD using ROC methodology.
8-64 MRCP Versus ERCP in Evaluating Patients with Suspected Biliary Obstruction--A Cost Effectiveness Trial (Work in Progress) Caroline Reinhold, MD, Montreal General Hospital, Montreal, PQ, Canada, A. Barkun, L. Joseph, Patrice M. Bret, MD, Mostafa Atri, MD, J. Barkun, G.M. Filed P u r p o s e : The aim of this study is to perform a patient o u t c o m e and a cost-effectiveness analysis on the routine use of magnetic resonance cholangiopancreatography (MRCP) vs. endoscopic retrograde cholangiopancreatography (ERCP) in the work-up of patients with suspected bile duct obstruction. M a t e r i a l s a n d M e t h o d s : A total of 600 patients with a clinical suspicion of bile duct obstruction will be randomized to undergo either MRCP or ERCP. Our primary objective is to perform a cost-effectiveness study with the major denominator of the cost-effectiveness ratio being the morbidity of the two groups~ Other secondary o u t c o m e measures will also be assessed for each group. In addition, we will attempt, by stratified analysis, to identify a group of patients w h o will benefit most from initiating the work-up for suspected bile duct obstruction with MRCP. All patients will be followed for a m i n i m u m of 6 months. Results: Over a 3 m o n t h period, 77 patients were referred for evaluation of bile duct obstruction at o u r institution. Of these, 35 patients were randomized to either ERCP or MRCP. Forty-two patients were excluded for the following reasons: 1) physician refusal, 2) patient refusal, and 3) m e t our previously defined exclusion criteria. C o n c l u s i o n : Our results are still too preliminary to draw any meaningful conclusion, We h o p e to demonstrate that MRCP is cost-effective in the evaluation o f patients with suspected bile duct obstruction.
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8-61 Colorectal Polyp Detection with 3D Spiral CT Colography: Technical Evaluation of CT Imaging Pro. tocol--Work in Progress Elizabeth G. McFarland, MD, Mallinckrodt Institute of Radiology, Saint Louis, MO, James A. Brink, MD, Dennis M. Balfe, MD, Jay P. Heiken, MD P u r p o s e : Spiral CT colography provides a 3D endoscopic evaluation of the mucosal surface of the colon for detection of polyps. Our work to date has investigated the image acquisition parameters best snited to detect clinically significant polyps, and b o t h identify and minimize 3D artifacts. M e t h o d s : To evaluate image acquisition parameters, an in-vitro colon p h a n t o m consisting of an air-filled, s m o o t h polyethylene tube was subanerged in a water bath and s c a n n e d at various orientations relative to the z-axis at 3ram collimation]pitch 1.67, and 5ram collimation/pitch 1.6 for all orientations. Scans were also performed with pitch of 1.0 and 2.0 (at 45 degrees). Image analysis was performed on coronal reformations (MPR) and 3D volume rendered (VR) images. Results: Rippling artifacts were demonstrated along the s m o o t h p h a n t o m colon wall with both the coronal 2D MPR and in the 3D VR images. The z-height of the artifact was influenced by pitch and the transverse width was influenced by the angle deviation from the z axis. C o n c l u s i o n : Evaluation of image acquisition parameters is important to both optimize detection of colorectal polyps and discriminate artifacts w h i c h can mimic mucosal folds.
8-62 Reader Accuracy with Monitor Display of Digitized Film Mammograms J. Jeffrey Carl,, MD, Bowman Gray School of Medicine, WinstorvSalem, NC P u r p o s e : To compare reader accuracy for detecting breast cancer with film and with monitor display of m a m m o g r a m s . M e t h o d s : Sixty m a m m o g r a p h y studies w e r e randomly selected from a population of w o m e n o n the basis of disease status as proven by biopsy or follow-up. Films w e r e digitized at 50/a (10 l p / m m ) resolution and were displayed on high-resolution (2,048"2,560) and 4uminosity (60-80 fL) monitors. The probability of breast cancer was rated by a board-certified radiologist without knowledge of patient history or prior studies. R e s u l t s : Sensitivity, specificity, and accuracy were 1.00, 0.51, and 0.65 for film and 0.94, 0.49, and 0.62 for monitor display. Correct decisions were similar (film 65% vs. monitor 62%, difference NS). ROC curves had to AUC of 0.97 (film) and 0.88 (monitor). The 8.7% larger AUC for film is not statistically significant (p 0.14). C o n c l u s i o n s : This study demonstrates the feasibility of interpreting digitized screening m a m m o g r a m s at a c o m p u t e r workstation. Diagnostic accuracy with monitor display of high-resolution (10 l p / m m ) digital m a m m o g r a m s is comparable to convention film display. The 8.7% greater accuracy with film, although not significant in this preliminary study, is consistent with the hypothesized results given greater reader experience and higher spatial resolution (> 13 l p / m m ) of film. L e a r n i n g Objectives: 1. Gain greater tmderstanding of h o w the m e t h o d of image presentation (film or monitor display) affects the detection of breast cancer with m a m m o g r a p h y . 2. Assess the impact of monitor display (soft copy) on the participant's practice of radiology. (l. Jeffrey Cart's activities are supported through a GE-AUR Research Award.)
8-63 Effect of Computer-Aided Diagnosis on Radiologist Performance: Database Development and Work in Progress Dulcy E. Wolverton, MD, UniversiOy of Chicago, Chicago, IL P u r p o s e : To evaluate t h e effect of c o m p u t e r aided diagnosis (CAD) detection s c h e m e s indicating potential m a m m o g r a p h i c lesions on the performance of radiologists with variable experience. M e t h o d s : A large m a m m o g r a p h i c database has been developed to be used in an observer study that includes 5 attending radiologists with variable m a m m o g r a p h i c experience (up to expert) and 5 radiology residents with training in mammography. These cases have been digitized and analyzed using CAD lesion-detection schemes. The CAD output indicating the locations of potential masses or clustered microcalcifications for each case as applicable will be presented to t h e observers in an ROC study. Results: The database consists of 240 screening m a m m o g r a p h i c examinations. Of these, 160 are normal and the remaining 80 are abnormal (50% malignant). The normal cases include a broad representative m i x of difficult cases w h i c h could provoke False-positive detections by both radiologists and CAD. The lesions in the database consist of 40 subtle mass lesions and 40 subtle clusters of microcalcifications. Characterization of these lesions and the preliminary CAD performance results will be presented. C o n c l u s i o n : Successful development of a difficult, b u t predominantly normal, m a m m o g r a p h i c database for use in a large observer study that will evaluate the utility of CAD using ROC methodology.
8-64 MRCP Versus ERCP in Evaluating Patients with Suspected Biliary Obstruction--A Cost Effectiveness Trial (Work in Progress) Caroline Reinhold, MD, Montreal General Hospital, Montreal, PQ, Canada, A. Barkun, L. Joseph, Patrice M. Bret, MD, Mostafa Atri, MD, J. Barkun, G.M. Filed P u r p o s e : The aim of this study is to perform a patient o u t c o m e and a cost-effectiveness analysis on the routine use of magnetic resonance cholangiopancreatography (MRCP) vs. endoscopic retrograde cholangiopancreatography (ERCP) in the work-up of patients with suspected bile duct obstruction. M a t e r i a l s a n d M e t h o d s : A total of 600 patients with a clinical suspicion of bile duct obstruction will be randomized to undergo either MRCP or ERCP. Our primary objective is to perform a cost-effectiveness study with the major denominator of the cost-effectiveness ratio being the morbidity of the two groups~ Other secondary o u t c o m e measures will also be assessed for each group. In addition, we will attempt, by stratified analysis, to identify a group of patients w h o will benefit most from initiating the work-up for suspected bile duct obstruction with MRCP. All patients will be followed for a m i n i m u m of 6 months. Results: Over a 3 m o n t h period, 77 patients were referred for evaluation of bile duct obstruction at o u r institution. Of these, 35 patients were randomized to either ERCP or MRCP. Forty-two patients were excluded for the following reasons: 1) physician refusal, 2) patient refusal, and 3) m e t our previously defined exclusion criteria. C o n c l u s i o n : Our results are still too preliminary to draw any meaningful conclusion, We h o p e to demonstrate that MRCP is cost-effective in the evaluation o f patients with suspected bile duct obstruction.
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