Catheter in use

This image was created for a grant proposal. We wanted to create an image that would show the ideal end result of our research. I made sure to include important elements, like a control interface for a two segment catheter and screen images from the type of mapping equipment we planned to use. Most of the elements of this picture were based on bits and pieces of pictures of EPs in the OR. I then made a drawing from each photograph and layered them together in this image. Still ignorant of vector graphics at the time this was all done in Paint.net at a reasonably large scale. The most interesting part for me was figuring out a way to manipulate the EKG screenshots so that they would appear at the correct angle to fit into the screens that I had drawn. A plugin for Paint.net allowed me to distort these images to fit after some trial and error. We ended up getting our grant, so I at least know that the picture didn't lose it for us!

Cathter PR

Over the years of working on this project I've had to generate a photographs of actual prototypes for use in university news magazines or journal publications. The one above is one of my favorites and also the least scientific. If the frame of this photo were expanded just a bit, my finger could be seen holding the tip of the catheter prototype to create this dramatic twisting bend. This photo was really taken for my own enjoyment and was never meant to be anything scientific. Never the less, it has been used as a background on websites, software interfaces and posters relating to the catheter. I guess it quickly conveys the fantasy of a very maneuverable catheter.

This image is a much more honest semi-scientific result. It is an overlay of the catheter being controlled with electrical current while reaching around obstacles placed on a flat board. One consequence of the overlay is that it is tough to tell which pieces of catheter belong to which element of the overlay, giving the illusion that the catheter has three segments. I was hoping to create this image by exposing the same piece of film multiple times while I steered the catheter around. This did not create the effect that I was looking for so I ended overlaying the different positions with varying levels of opacity to give the illusion of movement. This one has also been a surprisingly long lived image and I think it still represents clearly what we are trying to do.
And finally, the image that we put in the university engineering magazine. I really wanted to make a clean looking image for the magazine but unfortunately only had some dirty old foam board to use as a background. The catheter itself was also an older prototype which had degraded in appearance after sitting out in the open for too long. In photoshop, I cleaned up the background to give it a more uniform tone and fiddled with the white balance to return the catheter to a more healthy looking hue. I also rotated the dime so that it would look like I had actually been paying attention to little details like that while taking the picture! The coin-curl is the classic pose for a catheter PR photo and I couldn't resist trying to recreate it here even though this particular prototype was not capable of tightly enclosing the coin. Perhaps a quarter or a dollar coin would have been a better choice.

Catheter Cross Section

This image was created very early in the design phase for the catheter when I still had no idea how a real catheter was actual put together. This model was built in 3D using solidworks which I then tweaked the perspective on before recording a screenshot. I then traced the screenshot with black outlines of varying thickness, meant to emphasize the perspective. I wanted to use a 3D model as the basis for this image because it would take care of the shading on all of the many rounded surfaces for me.

Atrial Fibrillation

This is an animation that I made for use when introducing the motivation behind our catheter research. It is meant to explain the problem of atrial fibrillation and the method of intervention with an ablation catheter.

I don't really know how to use any animation software so each frame was made as a .png using Paint.net and warp functions to make the heart move. The frames were sequenced, repeated and assembled into movie files which I then edited together with movie maker. No one would be fooled into thinking we actually paid anyone to do this, but it was used in a local news story about our lab!

Early Liver Retractor Demo

This is another video that I made of an earlier prototype of the liver retractor. It does not include the write portion of the retractor which allows the fingers to be manipulated much more nimbly due to the reduced friction in the line back to the motor box. The steel wire that is controlling the movement of the retractor is wound around motors that are housed in the aluminum box in the background of the video. I used a braided metal hose from home depot to prevent kinking in the line guiding the pull wires back to the box.

Liver Retractor Demo

This is a video demonstration that I recorded for the retractor described in the previous two posts. You may notice that the "wrist" portion of the retractor is significantly shorter by the end of the video. This is because I broke the retractor while recording this demo and had to shorten it to get it working correctly. The shorter version functioned much better and allowed for a tighter bend in the wrist section.

The overall retractor worked fairly well, but unfortunately was not the ideal design for the purpose it was supposed to serve. I fell prey to the common problem of overestimating the scale at which the surgery took place. I had taken measurements and looked at videos and it seemed that the abdomen was a great cavernous space with room for a 5 inch long robot. During testing I realized that realistically, the "ledge" on the liver that I would be wrapping this retractor around was very narrow. A better approach would have been to think of the retractor as pushing the liver out of the way rather than lifting it up. A better design would have been more like a tent frame that supported the liver while staying out of the way of the surgeon operating on the stomach.

Liver Retractor Control

The first complaint that I got from the surgeon when I let him test the prototype retractor shown in the previous post was that the interface didn't make any sense. He moved the joysticks while watching the retractor, expecting it to imitate the motions of his fingers, while I had designed it so that the joysticks themselves were representations of the retractor fingers and the movements of the retractor would mimic the position of the joysticks.

The interface just wasn't set up for the kind of control that the surgeon wanted. He was correct though, the surgeon wouldn't be looking at the joysticks when he was working, he would be watching the retractor inside the patient. The interface would have to translate his hand motions into motions of the retractor. So I set out to make a new interface that would hide the joysticks and just focus on getting the surgeon's hand into a natural position.

This diagram shows a part of the new interface, the joysticks that control the finger portion of the retractor. It is shown upside down in an attempt to make the joysticks recognizable for what they are. The surgeons hand would wrap around the top (bottom in this diagram) of the shell containing the joysticks and his fingers would rest in a series of loops protruding from the shell. Each loop stem would pivot around a pin in a slot, allowing side to side and forward and backward motion. These motions would be transferred to tiny joysticks inside the shell which were wired to the motors that controlled the retractor. I tried to get at least the basic idea of this across in this section view which was drawn based on a CAD model I used to fabricate the shell.

However, I didn't show this diagram to the surgeon as that would have defeated the entire purpose of my redesign: to hide the joysticks so that he didn't have to think about them. When I let him control the retractor, it was much more intuitive for him. He did complain that the range of motion for each finger was too limited, but at least it was a step in the right direction!