Aug 3, 2013 — Mutual Information for Image Registration — Mutual information is an important concept for medical imaging, because it is so prominently used in image registration.  Let’s set up a typical registration problem.  Here we have two pictures of something that you see everyday, a dancing pickle! I’ve... Read more

Aug 3, 2013 — Multidimensional Scaling (MDS) — Multidimensional scaling (MDS) is a way to reduce the dimensionality of data to visualize it.  We basically want to project our (likely highly dimensional) data into a lower dimensional space and preserve the distances between points.  The first time that... Read more

Jul 31, 2013 — Imputation of Missing Values — In a perfect world, my data is absolutely perfect, and I’ve collected every feature or metric for every person, to be fed cleanly into some model.  Now let’s recognize the obvious reality that having complete data is rarely the case.... Read more

Jul 29, 2013 — Self Organizing Maps (SOM) — The goal of the** Self Organizing Maps** (SOM) is to use unsupervised machine learning to represent complex data in a low (e.g, 2D) dimensional space.  They are actually types of artificial neural networks (ANNs), meaning that we are going to... Read more