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成像了一种全新的对比机制：通过热膨胀将EM转换为声压。TCT压力是由位于成像视场(FOV)之外的超声换能器测量的，但由于传播到FOV中的电磁照射的短脉冲导致FOV内部的热膨胀而产生。TCT压力可以重建，以提供与组织对EM能量的特定吸收率(SAR)相关的图像。SAR既是外加电场强度|E|的函数，也是组织固有属性的函数。定量TCT的目标是恢复与TCT系统应用的|E|无关的固有组织特性。该方案的目标是将TCT信号强度量化为|E|的函数，以确保在活体内可以稳健地产生强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厘米范围内取得了良好的效果，但只有一次深度穿透射频(RF)照射的TCT临床试验报告。我们将使用在受控电磁环境下产生TCT压力信号的软件和硬件“试验台”来实现以下具体目标：1.对于简单的测试模体和动物组织标本，量化TCT声信号强度(以帕斯卡为单位)与RF照明参数：峰值功率、载波频率、偏振和脉冲宽度。软件试验台对几何简单模型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对比度和S/N的影响。我们将重点关注超声中使用的微泡和纳米粒子在PAT中的应用。3.将试验床改装为台式TCT断层扫描系统，用于体外成像。该试验台将旋转和平移试件，为层析重建提供圆柱形测量面。 公共卫生相关性：我们将验证一种全新的软组织诊断医学成像对比机制。热声学对目前成像技术严重不足的应用可能是一种福音，例如前列腺癌成像。

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.