Possible Patient Early Diagnosis by Ultrasonic Noninvasive Estimation of Thermal Gradients into Tissues Based on Spectral Changes Modeling

Abstract

To achieve a precise noninvasive temperature estimation, inside patient tissues, would open promising research fields, because its clinic results would provide early-diagnosis tools. In fact, detecting changes of thermal origin in ultrasonic echo spectra could be useful as an early complementary indicator of infections, inflammations, or cancer. But the effective clinic applications to diagnosis of thermometry ultrasonic techniques, proposed previously, require additional research. Before their implementations with ultrasonic probes and real-time electronic and processing systems, rigorous analyses must be still made over transient echotraces acquired from well-controlled biological and computational phantoms, to improve resolutions and evaluate clinic limitations. It must be based on computing improved signal-processing algorithms emulating tissues responses. Some related parameters in echo-traces reflected by semiregular scattering tissues must be carefully quantified to get a precise processing protocols definition. In this paper, approaches for non-invasive spectral ultrasonic detection are analyzed. Extensions of author's innovations for ultrasonic thermometry are shown and applied to computationally modeled echotraces from scattered biological phantoms, attaining high resolution (better than 0.1°C). Computer methods are provided for viability evaluation of thermal estimation from echoes with distinct noise levels, difficult to be interpreted, and its effectiveness is evaluated as possible diagnosis tool in scattered tissues like liver.

A New High-Resolution Spectral Approach to Noninvasively Evaluate Wall Deformations in Arteries

“…In fact, one of the signal processing tools applied here is an adaptation of an algorithm included in a precise broadband ultrasonic estimation procedure intended for other previous author's applications in thermal characterization [ 26 , 33 ]. Some modifications are introduced in order to be properly applied in this arterial context, for the tracking of thickness alterations in artery walls.…”

Estimation of PSD Shifts for High-Resolution Metrology of Thickness Micro-Changes with Possible Applications in Vessel Walls and Biological Membrane Characterization

“…The measurement resolutions so attained are compared with those obtained, using the same piezoelectric transducer and similar electronic transceiver hypotheses, but applying conventional signal processing methods in time and frequency domains, for the extraction of spatial parameters from ultrasonic echoes received in laminar samples. Concretely, some estimation results from using conventional cross-correlation techniques (well-known as useful time-delay estimators [23,30,31]), and of applying advanced frequency-domain methods (specifically improved for our purpose [27]) are shown. They provide, in some options of the second group, high-resolution estimations as required for the here selected problems.…”

“…It is based on the use of a modified auto-regressive spectral analysis, for estimating spatial aspects from ultrasonic echoes. The procedure is based on improving and extending a technique proposed in [27] for a quite different medical objective (the estimation of thermal changes in biological tissues containing internal scatterers). This last technique was based on detecting changes in the frequency location of overtones related to echoes spectra acquired from tissues having a regular internal structure.…”

“…A two-way procedure is used with the radiation controlled by a pulsed high-voltage electronic driving [25], detection-matching-tuning circuits and other analogue electronics (decoupling, broadband amplifying and filtering circuits) [26]. The detected spectral echo-information is then processed using custom digital signal techniques [27]. In each new application, an efficient integration of the selected transducers with the interface and transceiver electronic sub-systems is required.…”

“…In the last case, the frequency spectral patterns can be successful processed [20,24], with promising further extensions, maybe making possible the detection of some tumors (such as in breast) in their early phases. Thus, neo-vascularizations could be detected from their related light thermal effects, due to increases of blood perfusion in the pre-tumor zone [27]. …”