The availability of computing power has defined the features of ultrasound scanners since their inception.
@XOIIO, it’s actually a fair label as time is considerred one of the “D“s.
@Nullo, Crazy ole Wiki. “real time instead of offering a delayed image” That was true In the 70’s when ultrasound was just getting off the ground, you got a 2D image a while after the picture was ‘snapped’ as it took some time for the computing hardware at that time to assemble the image from collected data.
But that hasn’t been the case for a long time. Available affordable computers are orders of magnitude more powerful these days. For a couple decades ultrasounds have been full-motion 2D, in realtime (“3D”). (Plus sound, for echocardiograms you can hear the bloodflow in the part of the heart being scanned – fantastic! If you have a murmur or regurgitation you can hear that and see the cause. The sound isn’t from a microphone either, it’s reconstructed from doppler information in the waves bouncing back from the portion of the heart being scanned.)
In the newest fancier ultrasound systems, the computing resources are powerful enough to provide a representation of depth, 3D, in realtime, so spatial depth is the new 4th D added recently.
Back in the 70’s I worked as a electronics repair guy on peripherals to ultrasound machines and saw the nascent technolgy being used mostly for pre-natal at that time. Computing power was very expensive as each manufacturer built their own processors out of discrete logic. The imaging process borrowed a lot from the maths and methods used for phased array radar systems. Jaw-dropping engineering to my mind.
Only coincidentally, recently someone near and dear became a cardiac ultrasound tech and I had fun following the training and continue to pick up some of the trade rags out of curiosity to see what’s new. (Being a handy guinea pig, I’ve been practice-scanned according to all the common non-invasive cardiac and vascular ultrasound protocals.)
Computing power is now so cheap, compact and powerful (hey! youtube on my phone!) GE has a 3D unit (2D in realtime) that fits in your hand.