Volumetric Imaging

3D volumetric data

Heart in Vesalius3D

3D data can be divided into two categories: surface models and volumetric data. Surface models are generally encountered in the design industry, where objects are described by their surfaces, for instance using polygons or parametric surfaces. In the medical markets data is volumetric, meaning that the inside of the data is also modeled using a discretely sampled 3D set.

Typically, volumetric data is described by a group of 2D image slices, stacked together to form a volume. These slices are often acquired by scanners, such as CT, MRI or Ultrasound, at regular intervals. Other techniques generate immediate volume data. For instance a 3D ultrasound uses sound waves just as a 2D ultrasound does, but instead of transmitting the waves straight through the tissue and organs and back again, it is emitted in various angles. This causes a three-dimensional view. 4D volumetric data shows movement using a compilation of 3D images. Movements like heart motion can be seen. In contrast to most existing rendering software, PS-Medtech developed advanced volumetric rendering technology that preserves full quality of the 3D visualizations during 3D interaction and is independent of the modality that generated the data.

Faster and better interpretation with volumetric imaging

‘Wouldn’t it be wonderful to visually hold a pulsating patient heart in your hands and analyze it inside and out, intuitively, faster and better? When needed, you can hand over the heart to a colleague who can be a continent away and at the same time all your students can see what you are doing –live’.

Instead of viewing a couple of images per patient, the physician has access to hundreds of slices or clouds of data when using volumetric imaging. The time spend on each patient, however, remains the same. The result is a faster and better interpretation of 3D images and improved medical care at lower cost.

In practice the 3D data set is reduced to a digestible format (often one or two slices, in 2D not 3D) which is used to show to other specialists (e.g. radiologist to surgeon). The richness of the original 3D dataset is lost because of that and the benefit to other specialists is lost too. Is it not very often that surgeons complain about not getting the right images?

Two handed interaction and live 3D rendering

When you pick up an apple, examine it for spots, peel and slice it, you are using both your hands. Doing it with one hand tied behind your back is extremely difficult. So why are 3D analyses performed with one hand tied behind the back?

When interaction with 3D volumetric images is required (e.g. medical 3D images) the computer system has to keep calculating (rendering) the correct image based on the actions of the user. Unfortunately the bigger the data sets the higher the required processing power of the computer system rendering the image. As a result the image quality drops and the movement of the image becomes scattered (drop in frame rate). True lifelike interactive volumetric imaging requires live rendering with a minimal frame rate and no perceived loss in image quality.
For applications that claim efficient analysis of 3D volumetric data both live rendering of 3D volumetric data combined with intuitive 3D navigation are essential.

PS-Medtech has created 3D workstations and the Vesalius 3D software to analyze and present volumetric 3D and 4D data.