Thursday, August 2, 2012
I'm now on the fourth generation homemade ultrasound phantom. The recipe is pretty simple and low cost. I'm using store bought Knox gelatin, generic sugar-free psyllium fiber (Metamucil), and vein simulators (5mm Penrose drains). Before I link to the articles I used, I'm going to shoot the authors a quick email (The idea of using the above recipe is not my original idea). Right now I'm building the phantoms in cheap, flat food containers (ultra cheap tupperware clones). Each phantom is currently constructed of three "pours". Each pour uses the following recipe: 250-300cc's of boiling water 3 packets of Knox gelatin 1-2 tablespoons of sugar free psyllium fiber With the water at a boil, add the packets of Knox gelatin slowly. Some will probably clump up (This isn't a big deal. I'll go into that in a bit). While adding the gelatin, watch the boil, as it may boil over. Stir continuously. Once the gelatin is added, slowly add the psyllium fiber, again watching carefully and stirring continuously. If the mixture clumps a little bit, don't worry too much. If you are looking to create a relatively clear ultrasound phantom, pour the mixture into the mold (in my case, the cheap food storage container) through a strainer. This will catch most of the lumps. If you are looking to create a "Dirty" looking phantom, leave the clumps in. These clumps will sonographically appear as areas of varying tissue density. These inclusions mimic the appearance of real tissue. Our goal (at my hospital) is to create a better arm simulation for US guided IV insertion techniques. These inclusion bodies mimic scar tissue, varying tissue densities/types, and present a sonographic picture that is not as "cut and dried" as other vascular simulators. The cheap food containers that I am using hold 3-4 gelatin "pours". I have been using three pours for my prototypes. After each pour, I'm allowing the gelatin to firm up in the fridge for two hours, before pouring the next layer. After the first pour has firmed up, but before pouring the second pour, I'm putting down two penrose drains, filled with water/saline, to simulate vessels. One of the vessels I'm overfilling/pressurizing with 30% more fluid, to simulate an artery. My vessel simulators occasionally leak, so I'm not having tremendous success with the arterial simulation. Still, with the slight pressurization, the vessel does have a slightly different appearance when visualized sonographically. This is a practice, that once perfected, will enable students to differentiate between arteries and veins. I'm working on a method to create an automated pulse, so that the vessel is maintained under pressure and appears to pulsate.