3D medical imaging turns a stack of scan slices into a three-dimensional model of the body that a radiologist or surgeon can rotate, cut through and measure. It is also called advanced visualisation, or 3D reconstruction. A CT or MRI scan is made of hundreds of flat slices. When doctors look at the slices one by one, they must imagine the shape in their heads. A 3D model shows the shape directly.
It works in three steps. First, the software stacks the slices into a block of tiny cubes called voxels, the 3D version of pixels. Each voxel holds a density value. Second, it separates the structures of interest, such as bone, blood vessels or a tumour. This is called segmentation, and AI models now do much of it. Third, it draws those structures on the screen as a solid model, with colours and shading. The doctor can turn the model, hide the bones to see the vessels, and measure lengths and widths in millimetres.
Say a vascular surgeon in Chennai is planning to repair an aortic aneurysm. The aorta is the body's largest artery, and an aneurysm is a bulge in the wall of an artery. The CT scan has 600 slices, each 0.6 millimetres thick. The software stacks them into a block of 512 × 512 × 600 voxels. An AI model separates the aorta from the bones around it. On the 3D model, the surgeon measures the bulge at 5.8 centimetres across. She also measures the healthy section of artery just above the bulge, where a stent graft will be fixed. A stent graft is a fabric-covered metal tube that is placed inside the artery. That section is 18 millimetres long. These two numbers decide which size of stent graft the hospital orders, before the operation.
3D models are used for more than measurement. A model of a broken pelvis can be printed on a 3D printer, so that the surgeon can hold it and plan the repair. An orthopaedic surgical robot uses a 3D model of the patient's knee to guide the cuts in a knee replacement. A surgical robot can show the model beside the live camera view. A model of one patient's body that is used to plan and test a treatment is sometimes called a digital twin.
3D medical imaging is part of the PACS and imaging AI platform, so the radiologist can open it from the same viewer. It is different from image reconstruction. Reconstruction turns the scanner's raw measurements into slices. 3D imaging starts from those finished slices and builds a model from them.