To image something which moves, you must remain still. To image something which is still, you must move.
If you think on this long enough, the point is self-evident and requires no explanation. Or, just see some examples below.
We are pretty well adapted to seeing three dimensions at a time. Thus when imaging a moving structure like the heart, we hold the probe in a fixed position to obtain standard views. This allows us to focus on the movement, and cardiac presets optimize temporal resolution at the expense of spatial resolution. We are then seeing two spatial dimensions and one temporal dimension (heart moving in time).
D Shaped Left Ventricle from Sinai EM Ultrasound on Vimeo.
It is very difficult to appreciate the anatomy and function of the heart, for example, when the probe is moving.
In contrast, imaging the right upper quadrant for fluid in Morison’s pouch requires a slow fan through the liver, diaphragm, and kidney. This allows us to appreciate the entire potential space where fluid can collect. Abdominal imaging is optimized for spatial resolution at the expense of temporal resolution, so be sure to move the probe slowly. Fanning through the entire structure of interest will often reveal pathology which was missed with a single-plane scan. Small gallstones, small amounts of peritoneal or pleural fluid, saccular aneurysms, and other maladies can fool a novice sonographer who isn’t thorough. In this case we are seeing three spatial dimensions.
FAST1 RUQ pos from Sinai EM Ultrasound on Vimeo.
So, keep your audience in mind when you are creating scans. Should you fan through the static anatomy, or let the movement of the structures speak for themselves?
Hopefully you are using ultrasound to guide your insertion of central venous catheters. Once they are in, you still have to suture them at some point. Straight suture needles are often used to secure arterial and venous catheters to the skin. These types of suture needles have been demonstrated to be more dangerous than curved or blunt suture needles, with up to seven times higher rate of injury for health care workers. By utilizing the plastic needle sheath present in most central venous line kits as a “thimble,” counter pressure and skin puncture may be achieved without bringing the fingers near the sharp end of the suture. Here’s an image from Bret Nelson’s article on the technique.
