1 / 25

MESA CT Reading Center, LA Biomedical Research Institute, Harbor-UCLA Medical Center

MESA CT Reading Center, LA Biomedical Research Institute, Harbor-UCLA Medical Center. Robert C. Detrano, MD, PhD, Director Nathan D. Wong, PhD, Co-Director Eloisa Romero, MD, General Supervisor Christopher Dailing, Data Systems Consultant Angel Solano, Data Manager

cfrost
Download Presentation

MESA CT Reading Center, LA Biomedical Research Institute, Harbor-UCLA Medical Center

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MESA CT Reading Center, LA Biomedical Research Institute, Harbor-UCLA Medical Center Robert C. Detrano, MD, PhD, Director Nathan D. Wong, PhD, Co-Director Eloisa Romero, MD, General Supervisor Christopher Dailing, Data Systems Consultant Angel Solano, Data Manager Agnes Papa, MD, Principal CT Reader

  2. Scans Received (MESA Exam 3 through present) Missing: Minn 1, Co 1, UCLA 1, NW 1

  3. Good News and Bad News • Good News: New Software • Bad News: Scanner Changes

  4. Reading Center Software • 1995 - October of 2004 Mayo Clinic Software • 2000, Mayo and then Image Analysis Inc. stopped support, maintenance and updating of software. • Software frozen in the form it had in 2000 and could not be corrected when errors or problems were discovered.

  5. Mayo Clinic Software • Errors in slice thickness affected several hundred scans from Columbia site. (9/11 problem) • Failures to adjust image attenuation costly in terms of rereads. • Mis-assignment of calcified lesions to the four main coronary branches. • Non-standard calculation of calcium mass. • Non-correctable errors in calcium mass and non-usable data. • User-unfriendly method for calculating aortic calcium • “Bombs” caused the software to stop functioning. • Missed many protocol violations.

  6. Rephot Imaging LLC Software • 11/2004 until present • Creating arterial regions, identifying lesions, calculating scores, volumes and volume scores identical to Mayo Software. • Standard and accurate mass calculation. • Maintenance Contract and Good Technical Support. Errors can be fixed. • User friendly aortic calcium determination.

  7. Validation Study • Same reader (Agnes Papa) read 295 MESA scans using Mayo and Rephot softwares with interval of two weeks. • Coordinating center chose list of scans randomly.

  8. Validation for Accuracy • Software calculated scores and volumes checked against hand calculated results showed exact agreement in six lesions . • Mass Check of known mass of calcium hydroxyapatite in calcium phantom (200 mg/cc plug) : 98% agreement.

  9. Validation for Backwards Compatibility Discordance: 2 of 295 cases Adjusted Score: Mayo Rephot Case 1 0 204 Case 2 16.82 0

  10. Adjusted Scores 5000 4500 4000 3500 Mayo Scores 3000 2500 2000 1500 1000 500 0 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Rephot Scores Validation for Backwards Compatibility R = 0.990

  11. Validation for Backwards Compatibility R = 0.996 MAYO mass = [1.22 (SE=0.006) X Rephot mass ] + 3.00 (SE=0.596).

  12. Independent Analysis and Evaluation • AGES study is doing its own validation study. • MESA CC has done independent analysis of our data.

  13. CC Independent Analysis

  14. CC Independent Analysis

  15. Further Analysis • IHA doing an independent validation on a separate data set. • Requests to redo from CC • IDNO Mayo Rephot Redo Rephot • 4018974 0 204.22 13.08 • 4022807 16.82 0 16.82 • 4017749 294.41 298.16 349

  16. Exam 3 Scanner ChangesNumber of ppt scan data lost • Johns Hopkins: Siemens VZ, 4 Channel MDCT  Toshiba 32  Toshiba 64 Aquillion November 2004 • Univ of Minnesota: Siemens VZ, 4 Channel  Siemens Sensation 16 channel • Columbia: GE Imatron C300  Siemens Sensation 64, March 2005

  17. Exam 3 Scanner ChangesColumbia • Increase in CAC higher than expected. • Scanner Protocol appropriate • Reason Uncertain. • Solution Uncertain

  18. Exam 3 Scanner Changes • Johns Hopkins: 49 ppts affected ( change results probably not usable) • Univ of Minnesota: (73 ppts affected: change results probably not usable) • Columbia: (129 ppts affected: change results probably not usable)

  19. Exam 3 Scanner Changes Columbia Table 1.3: Summary of Columbia Phantom Adjusted Agatston Scores by Exam and CT Scanner Used at Exam 3 3 Summary is based on N where at least one CAC>0 (i.e. we are describing distributions in those who change). According to Table 1, 112 participants in the Sensation Cardiac 64 group and 133 participants in the Imatron EBT group meet this criterion.

  20. Exam 3 Scanner Changes Columbia Dependent Variable: E3 - E1 Phantom Adjusted Agatston Difference a Covariates appearing in the model are evaluated at the following values: BASELINE CAC = 221.7301, AGE = 65.07, FASTING GLUCOSE (mg/dl) = 105.48 (and are also adjusted for categorical variables GENDER, RACE, and DIABETES STATUS).

  21. Exam 3 Scanner Changes Columbia- Potential causes: • Exam 1 error, including 9/11 over-correction - ruled out • Reading Software Problem - ruled out • Inappropriate Phantom attenuation correction – ruled out • Inappropriate mA, kVP, exposure time – ruled out • Blurring from different exposure times (100 vs. 220 msec) – unlikely to cause such a large difference • Other protocol/physical factors - ????

  22. Columbia Exam 3 – 1 difference. Proposed Approach • Special committee of experts including MESA radiologists, physicists and technologists, physicists and engineers from outside MESA. • Visit by expert to field site • Involvement of Siemens.

  23. Columbia Calcium Score Statistics – September 11, 2005 (N.D. Wong) n-sizes reflect no of scans (divide by 2 to get approx# of subjects) 1adjusted for scanner, pre-post 9/11 status, baseline score, age, LDL, SBP, diabetes, and smoking. 2 adjusted for baseline risk factors (and baseline score for Exam 2-3 mean) *p<0.05, ** p<0.01, ***p<0.001 compared to reference

  24. Validation for Backwards Compatibility Weekly Checks During first Month of Use MAYO mass = [1.22 (SE=0.006) X Rephot mass ] + 3.00 (SE=0.596).

  25. CC Independent Analysis

More Related