Uncertainty assessment of effective radiating area and beam non-uniformity ratio of ultrasound transducers determined according to IEC 61689:2007

Abstract

This work presents the uncertainties in the effective radiating area (A ER ) and beam non-uniformity ratio (R BN ) for ultrasound (US) transducers in the range of 1.0 MHz to 3.5 MHz, and for head diameters of 1.27 cm and 2.54 cm. Measurements were performed using the US pressure field mapping system developed at the Laboratory of Ultrasound located at the Brazilian National Metrology Institute, which provides national traceability for the assessed quantities. The calculation protocol was developed based on Standard IEC 61689:2007. The type A uncertainty was estimated from four repetitions of the full measurement procedure for determinations of A ER and R BN , and the type B uncertainty was estimated from mathematical models for both parameters, based on IEC 61689:2007 and the ISO 'Guide to the Expression of Uncertainty in Measurement'. The maximum combined expanded uncertainties (95% confidence level) were 6.8% for A ER and 14.9% for R BN .

Effective radiating area and beam non-uniformity ratio of ultrasound transducers at 5 MHz, according to IEC 61689:2007

“…That work is an extension to the one undertaken in the range of 1-3.5 MHz [2], which results are reproduced here for discussion. Besides, discussion about the main sources of uncertainty is also presented.…”

“…Concerning R BN , all values were less than 3.51. Additionally, the results presented expanded uncertainties were less than 6.8% for A ER and 14.9% for R BN [2].…”

“…In a previous work [2], A ER and R BN values were determined for two transducers (£ = 1.27 cm) with frequencies of 1.0 MHz and 2.25 MHz, and for two transducers (£ = 2.54 cm) with frequencies of 1.0 MHz and 3.5 MHz. They were mapped along the beam axis using steps of 0.1 cm to determine the position of the last maximum of pressure of the transducer beam (z N ).…”

“…In this present extended work, the A ER and R BN values were determined for two transducers (£ = 2.54 cm) with nominal frequency of 5.0 MHz, using the same procedure describe in [2]. Herein, the A ER average values were 4.66 cm 2 (expanded uncertainty = 0.18 cm 2 , or 3.9%) and 4.81 cm 2 (expanded uncertainty = 0.18 cm 2 , or 3.8%) and R BN average values were 2.39 (expanded uncertainty = 0.32, or 13.5%) and 2.52 (expanded uncertainty = 0.37 cm 2 , or 14.5%).…”

“…represent the quantity to be considered and ''(Type B)" or ''(Type A)" refer to the kind of uncertainty evaluated. Details about how each uncertainty was estimated, and about the derivation of A ER and R BN uncertainty models was calculated, are presented in [2].…”