Temperature dependence of ultrasonic backscattered energy in images compensated for tissue motion

R. Martin Arthur, Jason W. Trobaugh, William L. Straube, Eduarde G. Moros, Suvimol Sangkatumvong

Research output: Contribution to journalConference article

4 Scopus citations

Abstract

Noninvasive temperature imaging would enhance the ability to uniformly heat tumors at therapeutic levels. Ultrasound is an attractive modality for this purpose. Previously, we predicted monotonic changes in ultrasonic backscattered energy (CBE) for certain sub wavelength scatterers. We measured CBE values similar to our predictions in bovine liver, turkey breast, and pork rib in ID. Those measurements were corrected manually for changes in the axial position of scatterers with temperature. To investigate the effect of temperature on CBE in 2D, we imaged 1-cm thick samples of bovine liver during heating in a water bath from 37 to 50°C. Images were formed by a Terason 2000 imager with a 7 MHz linear probe. Employing RF signals from the Terason 2000 (courtesy Teratech Corp.) permitted the use of cross-correlation as a similarity measure for automatic tracking of feature displacement as a function of temperature. Tissue motion across the specimen was non-uniform with typical total displacements of 0.5 to 1 mm in both axial and lateral directions. Tissue motion in 8 image regions was tracked from 37 to 50°C in 0.5°C steps. Motion compensated image regions were demodulated with the Hilbert transform and smoothed with a 3×3 running average filter before forming the backscattered energy at each pixel. Our measure of CBE compared means of both the positive and negative changes in the BE images. CBE changed monotonically by about 4 dB at 50°C from its value at 37°C. Relatively noise-free CBE curves from tissue volumes of less than 1 cm3 supports the use of CBE for temperature estimation. Motion in 3D will affect CBE values, but because beam width in elevation is larger than the lateral width, effects of motion in elevation on CBE may be less. Thus, we expect CBE to support temperature estimation in 3D. Furthermore, because CBE exploits inherent tissue inhomogeneities, extension to in vivo applications is a genuine prospect.

Original languageEnglish
Pages (from-to)990-993
Number of pages4
JournalProceedings of the IEEE Ultrasonics Symposium
Volume1
StatePublished - Dec 1 2003
Event2003 IEEE Ultrasonics Symposium - Proceedings - Honolulu, HI, United States
Duration: Oct 5 2003Oct 8 2003

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