Validation of an assessment tool for estimation of abdominal aortic aneurysm compression in diagnostic ultrasound

Ultrasound Transducer Pressure: An Unexplored Source of Abdominal Aortic Aneurysm Measurement Error

“…The previous in vitro study found that the applied transducer pressure, when measuring AAA diameter on a US phantom, varied significantly between sonographers (2000%), with no correlation to sonographer experience (Svendsen et al 2021). These findings support the present study's relevance and mandated development of a tool allowing for a clinical assessment and standardization of transducer pressure during abdominal US scans.…”

“…The principle of translating gel-pad deformation into applied transducer pressure was previously reported in an in vitro study (Svendsen et al 2021). In this clinical study, the gel-pad principle was investigated in a group of participants with AAA diameter below and above the repair threshold, and it was found that AAA compression caused by a firm transducer pressure led to a diameter error that would delay treatment in every tenth of the investigated participants with AAA and erroneously prolonged surveillance intervals.…”

“…The difference in gel-pad thickness (mm) in the AP direction during light versus firm transducer pressure was defined as the gel-pad deformation, and in this study, light transducer pressure was considered the diagnostic standard (gold standard). In line with the previous study (Svendsen et al 2021), a linear model fit of the gel-pad deformation was established with an estimated Young's modulus of 44.26 N/m 2 (r 2 = 0.98, Wald test, tdistribution: p < 0.0001, standard error [SE] = 2.84). Gel pad deformation was translated into applied transducer pressure, given that a 0.92-kPa increase in transducer pressure corresponded to a 1-mm gel-pad deformation.…”

“…The aortic image was acquired and the measurement performed in a cross-sectional plane, perpendicular to the aortic centerline based on symmetric circular imaging of the AAA. Development of the gel pad and correlation of gel-pad deformation with the applied transducer pressure have previously been described in detail (Svendsen et al 2021). The cross-sectional US image with the maximal anterior-to-posterior (AP) diameter, during maximal systole, was stored using vertebra and the cava vein as anatomic landmarks, per department clinical guidelines (Bredahl et al 2013).…”

“…In an experimental setup, Svendsen et al ( 2021) measured the applied transducer pressure during AAA diameter assessment on a US phantom and found that, among experienced vascular sonographers, the applied US transducer pressure varied between 0.52 and 12.45 kPa, representing a range in transducer pressure of more than 2000% (Svendsen et al 2021). In the same study, Svendsen et al (2021) reported that deformation of a standardized gel pad, interposed between the transducer and the AAA US phantom, could be translated into the applied transducer pressure in kilopascals. The applicability of the gel pad in a clinical context has never been tested, and so far, no other tool allows for measurement and standardization of applied transducer pressure during abdominal US scans.…”