Method for estimating average grey-level's measurement uncertainty from ultrasound images for non-invasive estimation of temperature in different tissue types

Abstract

The objective of this work is to assess, on metrological basis, the average grey-levels (AVGL) calculated from B-Mode images for estimating temperature variations non-invasively in different kinds of tissues. Thermal medicine includes several thermal therapies, being hyperthermia the most noted and well known. Recently, efforts have been made to understand the benefits of ultrasound hyperthermia at mild temperature levels, i.e., between 39 °C and 41 °C. Moreover, the best practices on ultrasound bio-effects research have been encouraged by recommending that temperature rise in the region of interest should be measured even when a thermal mechanism is not being tested. In this work, the average grey-levels (AVGL) calculated from B-Mode images were assessed for non-invasive temperature estimation in a porcine tissue sample containing two different tissue types, fat and muscle, with temperature varying from 35 °C to 41 °C. The sample was continuously imaged with an ultrasound scanner, and simultaneously the temperature was measured. The achieved results were assessed under the light of the measurement uncertainty in order to allow comparability among different ultrasound thermometry methods. The highest expanded uncertainty of estimating temperature variation using AVGL was determined as 0.68 °C.

Keywords: B-mode image; Fat tissue; Metrology; Muscle tissue; Non-invasive temperature estimation; Ultrasound; Uncertainty.