I have to admit this usually provokes a little irritation as clearly people think you just turn on an ultrasound machine, point it in the right direction and the jobs done. Sadly not. GE or Medison have yet to produce the “talking ultrasound machine” that comes up with the diagnosis like one of those machines that reads the future at a fair-ground. Becoming an expert at interpreting ultrasound images entails hours and hours of scanning and assiduously making sure you know the outcome for the patients you scan. That is the only way to learn. Practice and feedback – no different to anything else. I think it was Anders Ericsson at Florida State University who came up with the concept of the 10,000 hour rule to be excellent at something – this applies to ultrasound like any other practical skill. Experience matters. Read Matthew Syed’s book “Bounce – The Myth of Talent and the Power of Practice” for a readable account of this issue. As an ex Olympic athlete he should know. Real expertise comes from a combination of talent, purposeful practice and a combinatorial explosion whereby a chance coming together of events gives someone the opportunity to hone their skills and make the most of their ability. Most fellow say it takes them 2 years full time to start feeling at all confident.
Another common misconception is that if a measurement it taken using an ultrasound machine it must be correct. Again – not so as highlighted by an important paper last year by my colleague Anne Pexsters. In this paper Anne showed that when measuring the size of an embryo or gestation sac there are significant differences when this is carried out by two experienced operators. These differences are relatively small – but enough to change a scan result in early pregnancy from “not sure” to “a miscarriage”. So any cut-off values used to make a diagnosis using ultrasound have to build in a margin or error and take inter-observer variability into account. Similarly there are variations between different ultrasound machines and probes.
So remember – ultrasound is subjective. Someone once said “there are a million SLR cameras in the UK but only 10 people know how to use them” – it is not simply point and shoot. Well – ultrasound is not much different. Most machines do the same job, it is the person doing the scanning that makes the difference.
For those who are interested the reference for the paper by Anne Pexsters is: Intra- and inter-observer reproducibility of first trimester measurements between 6 and 9 weeks gestation. Pexsters A, Luts J, Van Schoubroeck D, Bottomley C, Van Calster B, Van Huffel S, Abdallah Y, D’Hooghe T, Lees C, Timmerman D, Bourne T. Ultrasound Obstet Gynecol. 2010 Oct;36(S1):7.
The paper can be seen here: http://www.ncbi.nlm.nih.gov/pubmed/21077156