Progress Report

April 25^th, 2006

A Roundup

• Experiments with two data distribution have been resumed
• MIUA deadline extended; completion due within a couple of days
• Transactions on Medical Imaging review is available and further work is needed
• BMVC paper submitted after the previous meeting; decision to be made within a couple of months

Specificity and Distribution Differences

• Learn about the robustness of the measure
• Observations were made which are worth discussing
• Some interesting behaviour noted when measuring Specificity for differing distribution types (level of dis/similarity)
• Outcome and conclusions based on repeated experiment, but nothing numerical to go by
• If the two distributions which we compre are similar or highly dissimilar, Specificity drops as we increase the sample size (synthetic set 'dummy')
• This is very much as expected (easier to find a nearby match)

Specificity and Distribution Differences - Ctd.

• The in-between scenario (distributions have partial overlap) seems to lead to shaky curves that do not necessarily go down in value
• This has an explanation, which probably justifies the use of more complicated measures than Specificity
• This is one case where kNN might be of use

Two Similar Data Distributions

Two Similar Data Distributions - Ctd.

Specificity goes down gradually, but not monotonically

Isolated Distributions

Isolated Distributions - Ctd.

The value of Specificity is rather shaky

Distant Distributions

Distant Distributions Specificity

The value of Specificity goes down

Distribution with a Pinnacle

Distribution with a Pinnacle - Ctd.

The value of Specificity wobbles

Dimensionality and Specificity

• Experiments involved:
  • arranging for the two distributions to have a few outliers and some obvious differences
  • then, investigating the effect of dimensionality on Specificity
• No clear conclusions comes to mind from the experiments, but there are interesting observations to be made
• In hindsight, we ought to have scaled the curves so that all heads (and maybe tails) are positioned at the same point in the plot

Distributions with Outliers

An example of a few outliers

Distributions with Outliers - Ctd.

Outliers in the distribution affect dimensionality and vice versa (dependence upon)

Studying the Effect of Gamma

Experiments were run to study the effect of gamma

kNN Approach in Distribution Similarity/Specificity

• Study the effect of changing k in a kNN approach
• Comparing two dissimilar yet partially overlapping distributions
• As expected, more neighbours give a more stable measure, especially when the number of samples is low

kNN Variation Studies

Poster Printing and Corrigenda

• Final poster had a coarse font resolution due to the printer or nature of the job delivered to it
• 2 previous printouts of the poster had fine-resolution fonts
• All PDF's were generated in the exact same way with pdflatex as the principal tool
• A few corrections:
  • One arrow needed reversing
  • A series of error bar was an accidental re-use of a plot before it has been corrected (for TMI and other subsequent submissions)

Other Tasks Pertaining to Experiments

• Ongoing work concentrates on normalisation
• The conceded submission to MICCAI 2006 (revolves around entropy but not normalisation) can be perceived as work in progress
• Unrelated: Experimental Plan for normalisation sent by E-mail
• It is an incomplete experimental plan for some of the remaining bits where we left off
• The remainder (assessment in 3-D) is reliant on data being processed and passed on

Paper-related Tasks

• BMVC augmented, submitted
• Made the changes which we had discussed
• MIUA is due shortly
• TMI changes to be made by late May
• Need to work on the thesis as well (while waiting for 3-D registrations to assess and investigating normalisation further)

MIUA Deadline

• The MIUA deadline is just 2 days away
• Sent an MIUA paper (PDF) that is quite polished early in the morning
• The current length length (5 pages) indicates that we aim for an oral presentation rather than a poster
• A rudimentary 1-page summary was sent as well, in PDF and LaTeX formats

TMI Submission and Review

• The reply seems positive
• Making sure we make the deadline (late May) will perhaps affect the possibility of inclusion in the special issue
• There is a clear need to deal with the argument that we cannot assess a model-based NRR method using a model-based approach
• Bill might have access to other groupwise registration results for this data

TMI Submission and Review - Ctd.

• There probably won't be enough time to re-run 10 instantiations
• Plenty of work would be involved
• Something more cursory may suffice
• Can also deal with the criticism directly, but support from some experiment/s would be valuable