Several features of the Lego bricks contribute to their success in the medical fields. First of all, the manufacture of each block is quite accurate and consistent,which really helps with the construction of any device that has a high requirement on precision. For those who are interested in how this is achieved, here is a video on the secrete of Lego making.
The second major feature of Lego is the modular nature of the toy and diverse pieces, which offer great flexibility in making devices in different shapes and dimensions. Even better, the Lego robot series provide electronic components and the ability to program different actions, enabling the researchers to add intelligent kinetic inputs in scenarios like simulating organic movements without the cost of complicated machinery. Third, the material of Lego bricks are great for medical imaging applications, such as ultrasound, MRI and CT. Lastly, there are many freely available software, including the official 'Lego Digital Designer' to help the design process.
Now let's take a look at a couple of the medical applications of the Lego bricks.
Image distortion correction
MRI can be subject to image distortion just like your regular cameras. It can greatly affect the measurements of brain volumes. Such distortions may come from different sources, but in short, they are the results of 'not-nicely-behaving' magnetic fields, which may largely be characteristic for each individual MRI scanner. By mapping these distortions using a phantom, we can recover the 'true' images. One solution applies one such phantom made of a bucket of Lego bricks. The Lego phantom is scanned inside an MRI scanner, and a correction field is produced by registering the distorted image to the digital model of the phantom. As a result, any upcoming scans are corrected with this pre-calculated correction field. The images below are taken from the article "Improved Precision in the Measurement of Longitudinal Global and Regional Volumetric Changes via a Novel MRI Gradient Distortion Characterization and Correction Techniques" by Fonov et al. (2010). The image on the left demonstrates the 3D distortion field while the one on the right shows the alignment of the distorted scan (in red) with the digital model (in green).
In some applications, such as brain surgeries, ultrasound images are spatially tracked to provide real-time updates of tissue deformation. As a result, there is a need to establish the spatial transformation between the 2D ultrasound image and the motion tracking device attached to the transducer so that the pixels in the 2D image can be accurately mapped to the 3D world. This procedure is called ultrasound calibration. Historically, such a calibration procedure has always been achieved through the use of a phantom. To obtain the most accurate construction, there have been a long list of different phantom designs and mathematical formulations. These calibration phantoms can be terribly tricky to manufacture, and may be quite expensive as well. Alternatively, phantoms made of Lego bricks can be used.
One solution was proposed by the Perk Lab at Queen's University. The lego bricks provide a frame for the fishing wires to form a Z-shape configuration. By matching the features of the wires shown in the US scans (typically as bright dots) and the known configurations, one can compute the calibration matrix.