Wednesday, February 18, 2009

Digital Imaging Protocols for Pediatric Echo


This was the explanation I was given, very early in my introduction to "digital echo", about why we record These Views in This Order. At the time, I was coming from a lab that did things proper: starting with the subcostal views. The only sense this new "parasternal images 1st" protocol made was that it supposedly made reading the studies easier.
How convenient.

For you.

Who is this protocol for anyhow?

I insist that the marriage of the image acquisition protocol with the ordered reviewing of said images is a potential liability. Always starting with the parasternal view is fine for most hearts— most hearts are nearly normal. The problem, in my opinion, with starting with the parasternal view is: it presumes that things are normal, or are nearly normal, or that I can at least make something up to look passably normal.

If things are not normal (this is what we're supposed to be particularly good with in Peds, isn't it?) this type of protocol presumes too much: that I already know enough about the heart to make some sense of the parasternal views. Try this on: what is the PLAX view for a patient with dextrocardia, DORV, and pulmonary atresia supposed to look like? How about HLHS? In order to record meaningful parasternal long axis views of these types of abnormal hearts, the sonographer has to either:

  • immediately recognize the pathology from this one clip
  • spend time scanning from subcostals and apicals first (in order to sort it out) then return to the "starting point"- the parasternal views.

The first option is not a fair predicament for most sonographers (including physicians), and the second- grossly inefficient.

The Images are for Physicians

Certainly, I appreciate that in order to report the anatomy, arrangement, size, and function of the examined heart some considerable structure is required. There must be images that support and document our conclusions. And, as we are increasingly moving towards structured reporting, the structure of the underlying, supporting images must also evolve. I have no problem with this, in fact, I embrace it. It's the "absence of evidence is not evidence of absence" philosophy, taken to it's logical conclusion. We don't want anyone to report anything that our images can't substantiate. The fact that physicians will determine and require a certain, precise collection of images is undisputed. They may choose and prefer to review them in any particular order. Bully for them.
Our obligation is to provide these images.

I simply prefer to do it in a manner that is most efficient for me.

The Protocol is for Sonographers

What is really needed to improve our exam consistency is a system that allows for the flexible acquisition of any prescribed (minimum) set of images. On a small scale, we are already doing this with stress echo, particularly with exercise stress echo: you grab what you can, when you can, and sort it out later. The order of collection is irrelevant, but the presentation of the images, in order, is everything. I can't tell you how many fetal echos I have done that would have been greatly improved by the ability to collect the images as I saw them, and then sort them into a logical arrangement later. Not to mention every "new blue" dextrocardia-aortic-atresia-single-ventricle-goat-wreck (Goat Rodeo + Train Wreck, contracted form), I have done since the inception of the current "parasternals 1st" protocol.

I am eager to see what the new Philips iE33's SmartExams are all about.

Lately, I have been tinkering about with a collection of image acquisition protocols suitable for pediatric echo.
In addition to providing a basis for building our own structured, protocol-driven exams, I believe these could also turn into a fairly useful teaching tool (I still need more descriptions/images though).