The basic concept of 2D/3D/4D for many of us was introduced in high school geometry. Most of you will probably say to yourselves “I get it….2D – flat plane….3D – length, width, depth….and 4D – add in the element of time.” So your temptation is likely to stop reading and/or move on to something seemingly more interesting.
The advancement of 3D and 4D imaging technologies over the past decade does, however, represent a new era of diagnostic assessment, giving you the tools to visualize precise regions and identify/verify/document pathology more accurately. Additionally, these technologies are rapidly improving early diagnosis in the field of cardiology, emergency medicine, oncology, pediatrics, and sports medicine. In ultrasound, there is a dramatic progression beyond the traditional obstetric use.
2D flat images are stacked in sequence to produce 3D
3D and 4D imaging is simply a compilation of 2D (B-mode) images into a volume dataset. 3D imaging is achieved by “stacking” the “flat” 2D data into a master image block. You may sometimes hear the term “sequential plane imaging”, which gives you a sense of the “slices” of 2D data being gathered together.
The advantage of 3D imaging versus 2D relates to your ability to rotate the compiled volume dataset to achieve a visualization of optimal imaging planes. This goes beyond simply viewing a region through the orthogonal planes (axial/sagittal/coronal).
3D ultrasound image of gallbladder and liver vasculature using inversion-rendering techniques
Being able to see the off-axis planes that we are unable to obtain using conventional sonographic technologies is invaluable in the assessment of normal/abnormal anatomy and pathology.
With 4D technology, the 3D datasets are again “stacked” sequentially/chronologically in order to give you a dynamic visualization of what’s occurring over time.
3D and 4D imaging has become more widely available because microprocessor technology has advanced to the point where ultrasound devices can do the post-processing required in compiling the larger datasets of 3D imagery, and the even larger ones required in 4D, in a reasonable time frame.
Still, assessment and diagnosis can only be as good as the underlying data/scans. This will be discussed in our next Quick Concepts release, on 3D/4D acquisition tips.
