The General Medical Council’s study of junior doctors trained at three different medical schools found some struggled with the simple arithmetic needed to calculate drug doses. Just one in six of the Warwick University-trained medics passed an eight-question test on prescribing. The report concluded: ‘There was a consistent thread of under-preparedness for prescribing.

However, in response to this, and feedback from medical students themselves, the Department has funded the development of new online training packages on prescribing, to complement existing training.

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If producing animation is becoming part of your responsibility, it would be good to understand at least the fundamentals that relate animation and health care. A recurring challenge, because it is so often necessary, is relating animation to gross anatomy. In order to clearly communicate a medical device or procedure, we almost always need to include the related anatomical structures. So a logical place to begin a discussion with your medical animation studio is about their anatomy model library.

All animations begin with a model. A computer artist constructs a surface defined by polygons that resembles the original object. The more polygons, the closer the model resembles reality. A complex model can contain thousands of polygons. It can take a considerable amount of time to construct an adequate model, so it represents a material portion of the cost.

An obvious question you can ask is “How complete is your anatomical model?” But what is the right answer for you? First of all a “complete” anatomical model can’t exist. It would include every capillary, lymphatic duct, nerve, all major and minor structural features, such as cancellous and cortical bone, along with the periosteum, articular cartilage… well you get the picture. It would be more productive to ask for sample models of the specific anatomical features that relate to your project. That is what could save you money and time.

Another common question is “How do you know your anatomy is accurate?” Again the answer is complicated, but interesting. Let me digress for a moment into the biological difficulty in defining “accurate” anatomy.

The degree of variation in “normal” human anatomy is surprising, even to many in healthcare. More than 20% of us lack the pyramidalis muscle that attaches the pubic bone to the linea alba. Eight percent of adults have an extra set or ribs (making it thirteen as in chimpanzees and gorillas.) The plantaris muscle has disappeared in 9% of the population. Surgeons harvest the long palmaris muscle (running from the elbow to the wrist) for reconstruction, but it is absent in 11% of their patients. Even cervical ribs (associated with reptiles) appear in a small portion of the human population.[1] New human muscles are discovered routinely.[2]

After all, we appear different from the outside, so it makes sense that each of us differs on the inside. These structural differences are not “defects” since in some cases anomalies present in roughly half the population. A recent study[3] to find out why repeated mistakes were being made in liver surgery found that there were vascular or celiac axis abnormalities in 43% of the dissections. In addition to variation in structure among individuals, anatomical features show dramatic change with age, disease, amount of body fat, and lifestyle.

What “accurate” means for you is determined by your consulting medical professionals. More often than not, we are required to modify “standard” models to match the experience of a specific surgeon. Further note that devices and tooling are normally modeled from your CAD files, and the anatomy must be modified to match the accurate (by definition) engineer’s CAD files.

Now that we have “accurate” and “complete models, let’s look at the issues involved with model animation. To animate the models, they must be deformed. Examples are skin retracting, muscle contracting, and joints flexing. For this to appear correct, the artist must construct the polygons specifically to accommodate the deformation, in the same way that a door must have its hinges located precisely to function. This activity is called rigging. For realistic soft tissue deformation, the animator’s skill is paramount. If the same anatomical structure is to be flexed in a different manner, the model must be reconstructed to accommodate the new motion. Producers are often surprised by the additional cost when they request a mid-course change to their tissue deformations.

Keep in mind that changing one model in a given production has a ripple effect. Say you have ten scenes involving the use of a special retractor. Changing the design of the retractor in scene one almost always mandates changes to scenes two through ten to accommodate the change in the retractor. This is compounded when the geometry or elasticity of soft tissue is involved.

In the animation process we next apply an image onto the skin of our model. This “texturing” relies on the artist’s skill and has a major effect on the “realism” of the animation. This is what makes tissue look like real tissue and bone look like real bone. Watch a medical animation closely to study how the texture changes with deformation and you can quickly determine the skill of the artist. When choosing a vendor be sure to look at examples of their textured models to see what you might expect in your project.

 Now that we have models and textures, we must add lighting, camera movement, and coordinate these with the model animation. The next is the “rendering” where each frame of the animation gets created, much like a motion picture. After rendering, there may be an additional “compositing” step to add background and text. All of these stages must be completed with expertise to have a successful project.

To sum it up, your project begins by defining an acceptable anatomical model for your region of interest and tooling. Then skilled artists reconstruct that model to meet the deformation requirements of your project. A texture map is applied that is designed to work with your deformations. The rest is straight foreword skilled animation procedure. Significant cost savings can be realized by beginning with a good anatomical model, but the biggest savings can be realized by minimizing the number of revisions during the production of your project and working with a studio experienced in your specialty.