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

This study was aimed at quantifying the abdominal aortic aneurysm (AAA) compression phenomenon and assessing the use of a new tool to estimate transducer pressure in vivo. In this cross-sectional study, 47 participants with AAA and a median anterior-to-posterior (AP) AAA diameter of 46 mm (range: 30-76 mm) were included. The majority of the patients were overweight with body mass indexes >25 (33/47, 70%). A standardized ultrasound (US)-compatible gel pad, with a pre-defined thickness (15 mm) and mass (150 g), was interposed between the US transducer and participant to estimate the applied transducer pressure. A firm transducer pressure significantly lowered the median AP diameter from 46.1 mm (range: 29.7-76.3) to 39.4 mm (range: 21.7-67.5) (p = 0.001). The mean diameter bias between light and firm transducer pressure was 6.1 mm (95% confidence interval: 4.9-7.3). The applied transducer pressure varied significantly and could be measured by translating the deformation of a low-tech gel pad interposed between the US transducer and the participant.

Full-Volume Assessment of Abdominal Aortic Aneurysm by Improved-Field-of-View 3-D Ultrasound Performs Comparably to Computed Tomographic Angiography.

Three-dimensional ultrasound (US) of abdominal aortic aneurysms (AAAs) is limited by the field-of-view of the 3D-US transducer. To obtain an extended field-of-view (XFoV), two transducer navigation system-assisted US protocols have been developed: XFoV-2D and XFoV-3D. In this study, the XFoV US protocols were compared with the currently available 3D-US protocol with standard field-of-view (FoV-st) and the established gold standard, computed tomography angiography (CTA). A total of 65 patients with AAA were included, and AAA imaging was processed offline with prototype software. The novel XFoV-2D and XFoV-3D protocols allowed for assessment of full AAA volume in significantly more patients (45/65 [69%] and 43/65 [66%], respectively), compared with the current 3D-US standard, FoV-st (30/65 [46%] patients). The mean difference in AAA volume estimation between each XFoV US protocol and 3-D CTA differed significantly (XFoV-2D: 16.9 mL, XFoV-3D: 7.6 mL, p = 0.002), indicating that XFoV-3D agreed best with 3D-CTA. No significant difference was found in the variance of full AAA volume quantification between each XFoV US protocol and CTA (p = 0.49). It is concluded that the XFoV US protocols improved the generation of full AAA volumes compared with the currently available 3D-US technology, with AAA volume estimates comparable to CTA estimates.

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

The study investigated ultrasound (US) transducer push, tantamount to applied transducer pressure, during abdominal aortic aneurysm (AAA) US scanning in a simulated non-clinical setup. During an assessment of maximal AAA diameter on a three-dimensional print-based AAA phantom, US transducer push varied as much as 2000% (range: 0.52-12.45 kPa) amongst 16 experienced sonographers. The mean transducer push was 5.54 ± 3.91 kPa (CV = 0.71). Deformation of a standardized gel-pad allowed for transducer push calculation based on US images; Young's modulus of the gel-pad was estimated to 44,26 N/m2. The method is theoretically validated in a safe and non-clinical environment. Future investigations with the aim of clinical validation of the gel-pad principle on AAA patients are suggested, including the objectification of the magnitude of an eventual transducer push-related error during US AAA diameter measurement.