Ultrasound research – Sometimes you win, sometimes you lose

Abstract

Since diagnostic ultrasound imaging became widely available in the 1970s, it has become an indispensable and essential diagnostic tool. Initially, it was acceptable to simply see a structure: eventually, the clinical utility grew alongside the technological advancements of the imaging itself. As new technology was added, we found new applications: new diagnostic uses and new prognostic measures. And we continue to do so. Yet, perhaps, unlike our predecessors, we need to demonstrate that any new ultrasound is not only efficacious (i.e. it works in a controlled setting) but also effective (i.e. it works in an uncontrolled setting under normal clinical conditions), while at the same time, it does not add unnecessary delays or costs to patient care. And as we introduce new techniques, these are compared with existing approaches and potentially allow us to abandon the old ways. An important part of this is documenting that different operators get the same results, in the same patients or when reviewing the same images. That is where clinical ultrasound research comes into its own.

In this issue of AJUM, we have an example of a new technique that looks very promising when applied to a heterogeneous group of real-world patients. Srigandan et al.¹ present real-world evidence of the application of attenuation imaging (ATI) to diagnose hepatic steatosis beyond hepatorenal index, which is an older technique. Ferraioli et al.² showed in 2019 that this ATI was very promising in a pilot study under carefully controlled conditions, and Srigandan et al.¹ found that when this was applied to their clinical cohort, in usual clinical practice, it also outperformed the hepatorenal index.

In another large clinical cohort, Piotto et al.³ present their data, suggesting that the pyloric muscle reference values used as part of the workup for hypertrophic pyloric stenosis may be outdated and, indeed, incorrect, which can lead to delays in diagnosis. The published reference values have not changed much in three decades, yet ultrasound techniques and imaging quality have surged ahead, so this is not surprising that measurement thresholds have changed. Their study is one of the largest in the literature, and they recommend a significantly lower threshold for diagnosis, which will lead to earlier diagnosis; since this is often diagnosed in the few months of life, early and correct diagnosis is essential.

Continuing the theme of measurement, Pedretti et al.⁴ present data about consistency, or inter-measurer reliability, of cervical length. They invited 244 ultrasound professionals (94% sonographers) to grade 50 randomly selected transabdominal images and found significant variation with poor agreement compared to that reported by transvaginal imaging. The message is clear – operators need to be well trained, test their reliability within themselves and across one another, and undergo regular audit and feedback processes. But how many departments do this? It is relatively common in tertiary teaching and research hospitals, but I daresay not so much in purely clinical practices. Audit and research can, and should, be part of daily clinical practice.

Just like the ultrasound pioneers of the past, many of us observe phenomena in our daily practice. We observe patterns of tissue characteristics, for example, or we might see abnormal but commonly occurring flow rates, or a cluster of abnormalities in specific patient cohorts. This is what drives scientific enquiry and discovery. In this issue of AJUM, Cowie et al.⁵ used a large mixed cohort of patients, athletes and non-athlete controls to identify factors that may contribute to the presence of diastolic flow in the left ventricular outflow tract, which is traditionally only thought to have flow in the systolic phase of the cardiac cycle. They found that diastolic flow in the outflow tract was more common in young people and was associated with slower heart rates and enhanced ventricular function. Without the unique makeup of this cohort, this may not have been achieved. And certainly, without the drive to understand this flow, it would not have been investigated at all.

Clinical ultrasound research is not always successful – sometimes you win and sometimes you lose. Yet, I would suggest that even when you lose, you win. Even when a research study has a negative or null outcome, our profession wins. We do need to keep reproducing the research that shows ultrasound is efficacious, effective and reliable whenever and wherever it is applied, because as we know it is very operator- and patient-dependent. It is not a simple blood test that is for sure!