Surface perception

JORDY VAN ZANDWIJK: In medical practise, there are multiple imaging techniques. You may be familiar with imaging modalities like CT and MRI, which can produce three-dimensional images, of volumes. Although nowadays, this is also possible with ultrasound, most devices provide the operator mainly with two-dimensional flat images.

Since the human body is, of course, a three-dimensional structure, it requires a strong spatial visualisation ability of the operator to interpret the two-dimensional images. We will show you some of the basic surface perception concepts that may help you in medical practise. This will be done on one of our ultrasound simulation stations, making it easier to understand how to interpret. Of course, to obtain the best insights in surface perception, hands on training is the most important tool to improve spatial visualisation ability. This ultrasound simulation programme trains your surface perception skills. It mimics the situation of a specific object in a phantom patient, the mannequin.

In this exercise, we see on the screen that there is a virtual arrow placed in the abdomen of our phantom. Our goal is to visualise the object, the arrow in this case, as indicated by the target image. Therefore, we have to figure out how to place the transducer on the patient, to obtain this cross section, thus training our spatial visualisation ability. What can be useful in training the surface perception, is to virtually overlay the cross sectional field produced by this transducer. We can clearly see that this is a sector shaped field, formed by a curvilinear, or curved transducer. Observing this gives us insights in where to place the transducer on the phantom, and how to rotate and tilt the transducer.

To distinguish left and right in your image, transducers usually have a marker that is also located on your screen. With the real transducer, you can also verify this by placing your own finger on one side of its surface.

Training with arrows pointing in several different directions, and with different target images, teaches you to use different approaches with the ultrasound transducer. It is also helpful to train on different or multiple objects, like a cone, or circles. You can see that for these assignments, you need to combine information of the ultrasound cross sectional field and the orientation of the object in the mannequin. By doing this, your surface perception skills are trained. It is likely you do not have immediate access to a simulation training programme like this. Nonetheless, in the final test of this week, we provide some questions about how to place the transducer on the phantom.

It may be harder to imagine this without the equipment, but we think it is still a good way to test your spatial visualisation ability.