A look at Osirix

Volume renderings from high resolution CT-scans can show incredible detail

I was recently introduced to a program called Osirix. It’s a freeware program that runs on Mac and is used to view 2D medical data sets such as CT scans, PET scans, angiograms, MRIs and cone beam scans. What makes Osirix especially interesting is that it can take 2D data and convert it to 3D renderings. The 3D renderings produced can be manipulated, making it easier to visualize areas of interest. Images can be rotated, cropped and the opacity and colors representing tissues of different densities can be altered to make components of the scan more or less visible. These are just a few of the functionalities of the program, I’ve found it extremely useful for drawing. It can be difficult to find references that depict structures from certain angles, but using Osirix structures can be oriented in any position needed and unwanted tissue in the way can be edited out using filters and cropping. The program is used by doctors and other medical professionals. Anaplastologists, for example can use it to view patient CT data and determine the shape of bone to help plan the surgical placement of osseointegrated implants for implant-retained prostheses. The nice thing about Osirix is that images can be exported and further manipulated in programs such as Photoshop to assist in further planning of procedures and the development of prostheses and surgical guides.

Osirix takes series of 2D images like this CT slice and combines them to form volume renderings

Data sets are available online on the Dicom website, but if you have your own patient data and a Mac you can view it on your own computer. Haven’t you secretly always wanted to impress your relatives with a slideshow from your latest MRI?

New website almost finished!

Here’s a screen shot from the website I’m building. We were recently introduced to HTML and CSS (it joins French in the ranks of languages I have a marginal grasp of) and putting it to use building personal websites. Coding, I’m finding, requires a lot of patience and attention to detail. I’m always very pleasantly surprised and a little amazed when things actually work, it makes the 15 minutes of searching for the missing bracket feel worthwhile. It’s a little like “Where is Waldo” but less colorful and more frustrating. With no formal web design background I’ve tried to use common sense when it comes to esthetics, but more importantly it’s functional and easily navigated.

 

 

All lined up

I’ve always found contour line drawings a little daunting. When you can’t use shading to communicate form, the placement of each line extremely important and things like line weight need to be used carefully and correctly. There’s nowhere to hide in a line drawing. Our most recent assignment required three separate line drawings showing a figure, skeleton and our choice of organs. These drawings were then to be composited in photoshop. This assignment seemed deceptively simple at first glance. After a few sketches it became apparent that the assignment was going to be a lot more involved than initially anticipated, my first figure and skeleton came out lop-sided, and this became abundantly clear once they were in photoshop and refused to line up. Making sure that the anatomical landmarks on the figure aligned with those on the skeleton was challenging enough, but trying to get both sides symmetrical was an ordeal of it’s own. Anyone who’s ever draw a rib cage will sympathize. Rather than starting from scratch I Frankensteined together the parts of the drawings that I liked best, made sure everything that should align did, and printed off a copy. From that I traced the figure and the skeleton separately. This worked well, the new drawings were close to symmetrical but still varied slightly so it didn’t look like the image had just been flipped. From there it was relatively easy to place the organs based on descriptions and pictures describing where each organ is typically situated relative to the skeleton. Four rib cages and ten hours later I’m happy with how it turned out. It was also a good reminder of how difficult very simple looking line work can be to do well.

For all you aspiring phlebotomists

This “How-To” project demonstrates the proper way to perform a phlebotomy. This was a good opportunity to familiarize myself with Adobe Illustrator and the nefarious “pen tool”. I started with sketches in pencil that I scanned and then traced in Illustrator using pen tool primarily. I feel like I could have done more to accentuate the shapes by varying the line quality, but haven’t familiarized myself with that aspect of Illustrator yet. Perhaps that can be the focus of the next assignment we do with line in Illustrator.

Heart’s in the right place. The veins on the other hand…

Azygos Continuation - graphite

This was part of our third drawing assignment. Azygos continuation is a venous anomaly wherein the inferior vena cava doesn’t form. Instead the azygos vein forms from the merging of the common iliac veins. The hepatic veins drain directly into the right atrium and all the tributaries that would ordinarily flow into the inferior vena cava drain into the enlarged azygos vein. The azygos vein then empties into the superior vena cava.

The particular example of this anomaly that the assignment was based on was described in a paper from Anatomical Sciences International by Y. Tohno et al.. Part of the challenge of the assignment was interpreting what was described in the paper, there was a lot of work involved in figuring out the pattern of venous drainage and trying to make the proportions of the organs and veins accurate. Once the initial planning sketches were done the rendering was fairly simple albeit time consuming.

Lab and Studio

cadaver sketch - graphite

Prosected hand – graphite

My first (but far from last) exposure to the cadaver lab was during a figure drawing class. Here are some sketches from prosected specimens.

Shapely forms

I don’t think it would be an art class without a shape rendering exercise, so here it is;

Shapes, graphite

I think this is the first time I’ve drawn shapes without looking at a reference, in every previous shape assignment the focus has been on observating and accurately reproducing what you see. This is an interesting step away from observation. While observational drawing is still very important and is in many ways the ideal source to draw from, medical illustration requires that shapes be created realistically and believably even when direct observation is impossible. So much of what medical illustration deals with is microscopic or inaccessible so it becomes necessary to be able to imagine what forms look like without being able to actually see them. This assignment was a good introduction to drawing without seeing and trusting we can use the experience we have drawing observed shapes to render forms as we imagine them.