Testbed for Quantitative Thermoacoustic Tomography

描述（由申请人提供）：我们建议开发一个测试平台，用于量化热声计算机断层扫描（TCT）信号强度作为电磁（EM）照明脉冲参数的函数。TCT图像是一种全新的对比机制：通过热膨胀将EM转换为声压。TCT压力由位于成像视场（FOV）外的超声换能器测量，但由视场内的热膨胀产生，热膨胀是由EM照明传播到视场内的短脉冲引起的。可以重建TCT压力，以提供与组织对EM能量的比吸收率（SAR）相关的图像。SAR是外加电场强度、|e|和组织固有特性的函数。定量TCT的目标是恢复与TCT系统应用的b| E|无关的组织固有特性。本提案的目标是量化TCT信号强度作为|E|的函数，以确保在体内可以鲁棒地产生强TCT信号。许多令人鼓舞的光声断层扫描（PAT）研究表明，在皮肤表面和血管内2-3厘米内取得了良好的效果，但只有一项深穿透射频（RF）照明的TCT临床试验被报道。我们将使用软件和硬件“试验台”设计，在受控的电磁环境下产生TCT压力信号，以实现以下具体目标：量化TCT声信号强度（以帕斯卡（Pa）为单位）与射频照明参数：简单测试模型和动物组织标本的峰值功率、载流子频率、极化和脉宽。软件试验台对几何上简单的幻影的分析计算将与硬件试验台的测量结果进行比较。2. 量化造影剂对TCT造影剂和信噪比的影响。我们将重点介绍用于超声的微泡和用于PAT的纳米颗粒。3. 修改试验台，使其成为台式TCT断层成像系统，用于离体成像。该试验台将旋转和平移试样，为层析成像重建提供圆柱形测量表面。

DESCRIPTION (provided by applicant): We propose to develop a testbed for quantifying thermoacoustic computerized tomography (TCT) signal strength as a function of electromagnetic (EM) illumination pulse parameters. TCT images a completely new contrast mechanism: conversion of EM to acoustic pressures via thermal expansion. TCT pressures are measured by ultrasound transducers located outside of the imaging field of view (FOV) but are generated by thermal expansion inside the FOV caused by the short burst of EM illumination propagated into the FOV. TCT pressures can be reconstructed to provide an image related to the tissue's specific absorption rate (SAR) of EM energy. SAR is a function of both applied electric field strength, |E|, and intrinsic tissue properties. The goal of quantitative TCT is to recover intrinsic tissue properties independent of |E| applied by the TCT system. The goal of this proposal is to quantify TCT signal strength as a function of |E| to ensure strong TCT signal can be generated robustly in vivo. Many encouraging photoacoustic tomography (PAT) studies show good results within 2-3 cm of the skin surface and intravascularly, but only one clinical trial of TCT with deeply penetrating radiofrequency (RF) illumination has been reported. We will use both software and hardware "testbeds" designed to generate TCT pressure signals under a controlled EM environment to achieve the following specific aims: 1. Quantify TCT acoustic signal strength in Pascals (Pa) vs. RF illumination parameters: peak power, carrier frequency, polarization and pulse width for simple test phantoms and animal tissue specimens. Analytical calculations for geometrically simple phantoms from the software testbed will be compared to measurements from the hardware testbed. 2. Quantify effect of contrast agents on TCT contrast and S/N. We will focus on microbubbles used in ultrasound and nanoparticles as used in PAT. 3. Modify the testbed to become a benchtop TCT tomography system for ex vivo imaging. This testbed will rotate and translate specimens, providing cylindrical measurement surfaces for tomographic reconstruction. PUBLIC HEALTH RELEVANCE: We will validate a completely new contrast mechanism for diagnostic medical imaging in soft tissues. Thermoacoustics may be a boon to applications for which current imaging techniques are woefully inadequate, such as prostate cancer imaging.