Prof. Hiro Yoshida, Ph.D.Director, 3D Imaging Research,Massachuessets General HospitalAssociate Professor of Radiology, Harvard Medical School
Prof. Andrea LaghiAssociate Professor of RadiologyUniversity of Rome “La Sapienza”Chairman Workshop CommitteeEuropean Society of Gastrointestinal and AbdominalRadiologySecretary of the European Society of OncologicImagingResearch and clinical expertise:CT ColonographyMDCT, MRI, Nuclear Medicine
Dr. Daniele ReggeChairman of Radiology DeptInstitute for Cancer research and treatmentCandiolo (Turin), ItalyFellow of theEuropean Society of Gastrointestinal andAbdominal RadiologyResearch and clinical expertise:CT Colonography CADOncologic imaging
CT Colonography CAD. Why and how to use it. Emanuele NeriDiagnostic and Interventional Radiology University of Pisa
BACKGROUND• WE ARE MISSING LESIONS Total n° of Reconcilable Detected Authors missed polyps retrospectively retrospectively (≥ 10 mm) Gluecker et al. 14 of 44 7 of 14 50 (%) AJR 2004 Doshi et al. 34 of 76 23 of 34 67.6 (%)Radiology 2007 Courtesy of Daniele Regge Department of Radiology Institute for Cancer Research and Treatment, Candiolo (Turin), Italy
Background: per-polyp analysis (from IMPACT study – JAMA 2009) PROSPECTIVE IMPACT CLASSIFICATION REVIEW Observer error n=58 CTC false negative > 6 mm CC polyps n=110 53% n =352 FNR = 31% Not reconcilable n=52 47% CTC false Observer error Lesion size negative N=58 N = 110 6-9 mm 85 43 > 10 mm 25 15 Courtesy of Daniele Regge Department of Radiology Institute for Cancer Research and Treatment, Candiolo (Turin), Italy
Background: per-polyp analysis (from IMPACT study – JAMA 2009) PROSPECTIVE IMPACT CLASSIFICATION REVIEW Observer error n=58 > 6 mm CC polyps CTC false negative 53% n =352 n=110 Not reconcilable FNR = 31% n=52 47% CTC false Observer error Lesion size negative N=58 N = 110 6-9 mm 85 43 74% > 10 mm 25 15 Courtesy of Daniele Regge Department of Radiology Institute for Cancer Research and Treatment, Candiolo (Turin), Italy
• ½ of misses are observer errors• ¾ of these are polyps in the 6-9 mm range• ¼ of 6-9 mm polyps are high risk adenomas (IMPACT-SCORE)
Rationale of using a CAD• It has been statistically proven that the radiologist may miss the recognition of some significant findings in the course of reading. The causes of these errors can be: reading method• Poor image quality• The high workload with consequent fatigue and lack of concentration• Small lesions and/or difficult to identify• Subjectivity of interpretation• No systematic research (by lung segment or by colon segment)• To reduce the number of false negatives may be used a double reading of the examination, but a waste of resources is often not sustainable.• A particular condition is the screening setting (cancer prevention)
CAD improves reader sensitivity Sensitivity Sensitivity CAD Authors P No CAD assisted reading Baker M.E. 81% 91% P=0,0152Radiology 2007Petrick N. et al. 45% 61% P<0,01Radiology 2008Mang T.G. et al. 76% 93% P<0,05Eur Radiol 2007
CAD for CTC have different performance Number of patients Sensitivity per polyp ≥ 10 mm FPs per patient Fecal tagging (Number of (%) polyps) Yoshida, Radiographics 2002 71 (35) 21/23 (91) 2 No Mani, JCAT 2004 41 (69) 10/12 (83) ND No Bogoni, Br J of Radiology 2005 62 (39) 10/10 (100) 8 NoSummers, Gastroenterology 2005 792 (173) 25/28 (89.3) 7.9 – 2.1 Yes Halligan, Clin Radiol 2006 25 (57) 9/10 (90) ND Yes Taylor, AJR 2006 25 (32) 11/12 (92) 13 No Taylor, Radiology 2006 20 (43) 9/9 (100) ND YesHalligan, Gastroenterology 2006 167 (142) 17/19 (89.5) 11.6 No Taylor, Radiology 2007 25 (69) 18/19 (95) 19 No Mang, Eur Radiology 2007 52 (55) 24/25 (96) 1.7 No Petrick, Radiology 2008 60 (24) 5/5 (100) ND Yes Summers, AJR 2008 104 (86) 43/47 (91.5) 9.6 Yes
How to use the CAD•first reader•concurrent reader•second reader
How to use the CAD in the radiological workflow• First reader • The CAD read, the radiologist trust in CAD prompts and ignore the rest of the exam• Concurrent reader • CAD prompts are shown during the radiologist reading• Second reader • CAD prompts are switched off during the radiologist reading and switched on after the first reading.
How to use the CAD in the radiological workflow• CAD first reader • Advantage: faster method (2-4 minutes) • Risk: CAD errors (false positive and false negatives) are validated by the radiologist
How to use the CAD in the radiological workflow• CAD concurrent reader • Advantage • the radiologist is aided in realtime • Disadvantage • CAD prompts may distract the radiologist interpretation (main risk is to increase the number of false positives). • Increases the reading time.
How to use the CAD in the radiological workflow• CAD second reader • Advantages • the radiologist is not distracted by the CAD prompts (less influenced by the CAD) • Disadvantages: • Increases the reading time.
E. Neri, S. Halligan, M. Hellstrom, P. Lefere, T. Mang, D. Regge, J. Stoker, S. Taylor, A. Laghi. 2nd ESGAR Consensus statement on CT Colonography. Eur Radiol 2012, in press
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