3.4. Applications

Pixels: 2D elements in digital images (CT/MRI/X-ray). Each pixel represents a measured value at a specific (x, y) location in the scan. Voxels: Extension to 3D—volumetric pixels represent a small cube of material in the scanned object. Medical 3D data consists of stacked imaging slices, each with an array of voxels describing tissue properties.

In medical imaging, especially with technologies like CT (Computed Tomography) and MRI (Magnetic Resonance Imaging), the data starts as 2D images. Each small square in these images, known as a pixel, holds a specific measurement related to the scanned body part. For instance, it may record density or brightness at that location. When we move to 3D imaging, we transition from pixels to voxels, which are the 3D equivalent of pixels. A voxel represents a tiny cube of tissue, enabling the depiction of the entire volume of a scanned region. When these voxel values are stacked together, they form a complete 3D model of the anatomy.

Think of pixels like the individual tiles on a mosaic. Each tile (pixel) shows one piece of the picture, like a detail of an object. When we stack these tiles together in 3D using voxels, it’s similar to building a three-dimensional structure out of building blocks, where each block represents a slice of the object’s volume.

Scans: CT or MRI scanners generate DICOM image stacks. These are used to build 3D anatomical models by reconstructing regions using the values of the voxels (density, attenuation, etc.).

CT and MRI scanners capture slices of an object (like a loaf of bread), resulting in many 2D DICOM files that represent different cross-sections. Using these slices, we can reconstruct a full 3D model of the scanned anatomy by evaluating the density and attenuation (how much the tissue absorbs or reflects the scanning signal) properties of each voxel. This process forms a detailed representation that can be visualized and analyzed in three dimensions.

Imagine taking multiple slices of a loaf of bread. If each slice represents a cross-section of the loaf, when we put all these slices together, we can visualize the entire loaf again in three dimensions. In medical imaging, doctors can 'slice' through the body in similar fashion, creating a complete view of internal structures.

Applications: Patient-specific anatomical modelling, surgical planning, prosthetics, and 3D printed models for education/training. Medical imaging starts with DICOM files which are then segmented and converted into surface B-rep or solid (voxel/grid) models for analysis and physical replication.

The processed images from medical scans lead to practical applications, including creating detailed anatomical models tailored to individual patients, which can be very helpful for surgical planning. Surgeons can visualize intricate details of an anatomy before an operation, making it easier to prepare. Additionally, these models can also facilitate the design of prosthetics that fit perfectly based on the patient's anatomy. Finally, 3D printed models are increasingly being used for educational purposes and medical training, enabling students to learn on realistic replicas of human anatomy.

Consider how an architect uses blueprints to design a building—these blueprints contain specific dimensions and architectural features. Similarly, 3D anatomical models act as blueprints for surgeons, allowing them to plan operations precisely and customize prosthetic devices as per patient needs. In educational settings, just as students use physical models to learn concepts, future doctors train on 3D-printed anatomical models that replicate real human structures.

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