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Harmonizing Hippocampal Segmentation: Validation and Consensus on AC-PC Axis

This project aims to validate and achieve consensus on the AC-PC (anterior commissure-posterior commissure) axis for harmonizing hippocampal segmentation. Empirical data and expert opinions are utilized in a Delphi method to make informed decisions. The project also evaluates segmentation variability and compares it to pathology. The results will contribute to the development of a standardized protocol for hippocampal segmentation.

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Harmonizing Hippocampal Segmentation: Validation and Consensus on AC-PC Axis

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  1. VII PMT meeting – Feb 29, 2012 • Agenda: • Axes check • Validation vs Pathology • Paper Publications • Congress presentations & Meetings

  2. Project method • Delphi is required to take all decisions based on experience + evidence • Empirical data on SUs taken on ACPC is fed to Delphi (external & internal landmarks) • Delphi decides on which SUs make up harmo hippo (internal landmarks) • Delphi decides that best segmentation is on hippo axis (10-5-1 in favour-neutral-against) • Empirical evidence collected that total hippo volume on ACPC = hippo axis

  3. 1. Delphi is required to take all decisions based on experience + evidence

  4. 2. Empirical data on SUs taken on ACPC is fed to Delphi (external & internal landmarks) 3. Delphi decides on which SUs make up harmo hippo (internal landmarks)

  5. 2. Empirical data on SUs taken on ACPC is fed to Delphi (external & internal landmarks) 3. Delphi decides on which SUs make up harmo hippo (internal landmarks)

  6. 4. Delphi decides that best segmentation is on hippo axis (10-5-1 in favour-neutral-against) Round 1: Which plane Round 2: Agree on hippo plane Rounds 3 and 4 converged on mean angle between R and L axes Fisher’s Binomial Fisher’s exact DATA SHOWN IN PARIS, JULY 2011 Hippo AC-PC same Disagree same Agree Delphi: www.hippocampal-protocol.net/SOPs/delphipanel.html , access with user: prova , pw: prova

  7. 5. Empirical evidence collected that total hippo volume on ACPC = hippo axis LA*= LA traced only 5 images oriented along ACPC line

  8. 1 tracer VARIABILITY EVALUATION GOLD STANDARD VALIDATION vs PATHOLOGY 5 expert tracers 20 naive tracers Training (tracing 20 hippos on 1.5T ADNI scans with each SU) (SAME on 3T ADNI scans) Local Protocol: Experimental set (1.5T ADNI): 2 x each of the 5 Scheltens’s atrophy score x 2 sides (SAME on 3T ADNI scans) (total for each rater: 40 hippos) Local Protocol: 1.5T 3D T1-weighted scans from (Bobinski et al., 2000) pathologically verified set (total for rater: 30 hippos) Delphi panel → harmonized prot Benchmark Harmonized hippos: 1.5T ADNI scans 2 x each of the 5 Scheltens’s atrophy score x 2 sides (SAME on 3T ADNI scans) (total for each rater: 40 hippos) Qualification (20 tracers) Qualification Harmonized Protocol: 1.5T 3D T1-weighted scans from (Bobinski et al., 2000) pathologically verified set (total for rater: 30 hippos) Harmonized Protocol: Experimental set (1.5T ADNI): 2 x each of the 5 Scheltens’s atrophy score x 2 sides (SAME on 3T ADNI scans) (total for each rater: 40 hippos) global and local 95% confidence intervals VALIDATION ON 1800 HIPPOCAMPI IN TOTAL Harmonized Protocol: 1.5T ADNI scans 2 sides x 5 Scheltens’s atrophy scores x 3 time points (0-12°month-24°month) x 3 scanners + retracing for timepoint 1 (SAME on 3T ADNI scans) (total for each rater: 240 hippos – including 40 hippos already traced) RM-ANOVA: test of protocol main effect RM-ANOVA: test of main effects side, trace-retrace, atrophy, time, scanner, rater The best 5 naive tracers RM-ANOVA: test of rater and rater by center terms

  9. Pros & Cons Accepting the consensus on hippo axes would: Practical Reduce partial volume effects and facilitate manual tracing (tracers and panelists’ subjective reports) Changing to AC-PC would: Practical Facilitate automatic preprocessing • Methodological • Violate general method of the project (decisional tree) • Interfere with the aim of the project (define gold standard as best possible accuracy) • Disregard and contradict the opinion of 20 international experts of hippocampus • Methodological • Contrast with the orientation on which evidence was gathered • Note that this contrast : • did not constitute a problem for 20 international hippo experts • did not correspond to quantitative evidence showing any impact on the HarmoProt

  10. Validation versus pathology 1 tracer Local Protocol: 1.5T 3D T1-weighted scans from (Bobinski et al., 2000) pathologically verified set (total for rater: 30 hippos) WHICH SAMPLE? Qualification on benchmark images (total for each rater: 40 hippos) Harmonized Protocol: 1.5T 3D T1-weighted scans from (Bobinski et al., 2000) pathologically verified set (total for rater: 30 hippos) RM-ANOVA: test of protocol main effect

  11. Paper Operationalization Alzheimer’s and Dementia

  12. Papers describing the project Survey of protocols (preliminary phase; published, JAD 2011) Operationalization (preliminary phase; to be completed) Delphi consensus (Brescia Team) Master tracers’ practice and reliability (Brescia Team) Development of certification platform (Duchesne and coll?) Validation data and Protocol definition (Brescia Team) Validation vs pathology (TBD)

  13. 1 tracer VARIABILITY EVALUATION GOLD STANDARD VALIDATION vs PATHOLOGY 5 expert tracers 20 naive tracers Training (tracing 20 hippos on 1.5T ADNI scans with each SU) (SAME on 3T ADNI scans) Local Protocol: Experimental set (1.5T ADNI): 2 x each of the 5 Scheltens’s atrophy score x 2 sides (SAME on 3T ADNI scans) (total for each rater: 40 hippos) Local Protocol: 1.5T 3D T1-weighted scans from (Bobinski et al., 2000) pathologically verified set (total for rater: 30 hippos) Delphi panel → harmonized prot Benchmark Harmonized hippos: 1.5T ADNI scans 2 x each of the 5 Scheltens’s atrophy score x 2 sides (SAME on 3T ADNI scans) (total for each rater: 40 hippos) Qualification (20 tracers) Qualification Harmonized Protocol: 1.5T 3D T1-weighted scans from (Bobinski et al., 2000) pathologically verified set (total for rater: 30 hippos) Harmonized Protocol: Experimental set (1.5T ADNI): 2 x each of the 5 Scheltens’s atrophy score x 2 sides (SAME on 3T ADNI scans) (total for each rater: 40 hippos) global and local 95% confidence intervals Harmonized Protocol: 1.5T ADNI scans 2 sides x 5 Scheltens’s atrophy scores x 3 time points (0-12°month-24°month) x 3 scanners + retracing for timepoint 1 (SAME on 3T ADNI scans) (total for each rater: 240 hippos – including 40 hippos already traced) RM-ANOVA: test of protocol main effect RM-ANOVA: test of main effects side, trace-retrace, atrophy, time, scanner, rater The best 5 naive tracers RM-ANOVA: test of rater and rater by center terms

  14. Congress presentations - AAN 2012, New Orleans Oral Presentation S04.003, April 24, Aging and Dementia: Therapeutic Interventions, 1.30 pm M Boccardi, M Bocchetta, L Apostolova, J Barnes, G Bartzokis, G Corbetta, C DeCarli, L DeToledo-Morrell, M Firbank, R Ganzola, L Gerritsen, W Henneman, R Killiany, N Malykhin, P Pasqualetti, J Pruessner, A Redolfi, N Robitaille, H Soininen, D Tolomeo, L Wang, C Watson, H Wolf, S Duchesne, CR Jack, GB Frisoni. Delphi consensus on landmarks for the manual segmentation of the hippocampus on MRI: preliminary results from the EADC-ADNI Harmonized Protocol working group. - AAIC 2012, Vancouver Abstract n. 26291, submitted to AAIC 2012 M Boccardi, M Bocchetta, A Redolfi, P Pasqualetti, R Ganzola, N Robitaille, S Duchesne, CR Jack, GB Frisoni and the EADC-ADNI Hippocampal Harmonization Group. Definition of Harmonized Protocol for Hippocampal Segmentation Abstract n. 26292, submitted to AIC 2012 M Boccardi, M Bocchetta, A Redolfi, P Pasqualetti, R Ganzola, N Robitaille, S Duchesne, CR Jack, GB Frisoni and the EADC-ADNI Hippocampal Harmonization Group. Definition of Harmonized Protocol for Hippocampal Segmentation

  15. SOPs periodical meetings AAN – April 24, 2012 AGENDA: 1. Delphi Paper; 2. Publication policy AAIC – July 2012 AGENDA: 1. Presentation of Harmonized Protocol; 2. Reliability figures

  16. GANTT

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