The Department of Electrical Engineering, Federal University of Petroleum Resources, Effurun, Delta State, Nigeria.
Med Phys. 2013 Nov;40(11):111910. doi: 10.1118/1.4824149.
Optical/acoustic radiation imaging (OARI) is a novel imaging modality being developed to interrogate the optical and mechanical properties of soft tissues. OARI uses acoustic radiation force to generate displacement in soft tissue. Optical images before and after the application of the force are used to generate displacement maps that provide information about the mechanical properties of the tissue under interrogation. Since the images are optical images, they also represent the optical properties of the tissue as well. In this paper, the authors present the first imaging probe that uses acoustic radiation force in conjunction with optical coherence tomography (OCT) to provide information about the optical and mechanical properties of tissues to assist in the diagnosis and staging of epithelial cancers, and in particular bladder cancer.
The OARI prototype probe consisted of an OCT probe encased in a plastic sheath, a miniaturized transducer glued to a plastic holder, both of which were encased in a 10 cm stainless steel tube with an inner diameter of 10 mm. The transducer delivered an acoustic intensity of 18 W/cm(2) and the OCT probe had a spatial resolution of approximately 10-20 μm. The tube was filled with deionized water for acoustic coupling and covered by a low density polyethylene cap. The OARI probe was characterized and tested on bladder wall phantoms. The phantoms possessed Young's moduli ranging from 10.2 to 12 kPa, mass density of 1.05 g/cm(3), acoustic attenuation coefficient of 0.66 dB/cm MHz, speed of sound of 1591 m/s, and optical scattering coefficient of 1.80 mm(-1). Finite element model (FEM) theoretical simulations were performed to assess the performance of the OARI probe.
The authors obtained displacements of 9.4, 8.7, and 3.4 μm for the 3%, 4%, and 5% bladder wall phantoms, respectively. This shows that the probe is capable of generating optical images, and also has the ability to generate and track displacements in tissue. This will provide information about the optical and mechanical properties of the tissue to assist in epithelial cancer detection. The corresponding theoretical FEM displacement was 5.8, 5.4, and 5.0 μm for the 3%, 4%, and 5% phantoms, respectively. Deviation between OARI displacement and FEM displacement is due to the resolution of the crosscorrelation algorithm used to track the displacement. To the authors' knowledge, this is the first probe that successfully combines OCT with a source of acoustic radiation force.
The OARI probe has the ability to provide information about the mechanical and optical properties of phantoms and soft tissue. This could prove useful in early epithelial cancer detection. Because the probe is 10 mm in diameter, it is currently only useful for skin and oral applications. The probe would have to be reduced in size to make it applicable for cancer detection in other internal sites. Future work will focus on utilizing phase-sensitive optical coherence elastography to obtain the resulting OARI displacements, improving the resolution of the probe, and enable physicians to better evaluate the mechanical properties of soft tissues.
光/声辐射成像（OARI）是一种新兴的成像方式，用于探测软组织的光学和机械特性。OARI 利用声辐射力在软组织中产生位移。在施加力前后使用光学图像生成位移图，提供有关被探测组织机械特性的信息。由于图像是光学图像，因此它们还代表组织的光学特性。在本文中，作者介绍了第一个使用声辐射力结合光学相干断层扫描（OCT）的成像探头，以提供有关组织光学和机械特性的信息，以协助上皮癌（特别是膀胱癌）的诊断和分期。
OARI 原型探头由 OCT 探头封装在塑料护套中，微型换能器胶合在塑料支架上，两者都封装在 10 毫米内径的 10 厘米不锈钢管中。换能器的声强为 18 W/cm²，OCT 探头的空间分辨率约为 10-20 μm。管内充满去离子水以实现声耦合，并覆盖低密度聚乙烯帽。OARI 探头在膀胱壁模型上进行了特性和测试。这些模型的杨氏模量范围为 10.2 至 12 kPa，质量密度为 1.05 g/cm³，声衰减系数为 0.66 dB/cm MHz，声速为 1591 m/s，光学散射系数为 1.80 mm⁻¹。进行了有限元模型（FEM）理论模拟，以评估 OARI 探头的性能。
作者分别获得了 3%、4%和 5%膀胱壁模型的 9.4、8.7 和 3.4 μm 的位移。这表明探头能够生成光学图像，并且还具有在组织中产生和跟踪位移的能力。这将提供有关组织光学和机械特性的信息，以协助上皮癌的检测。相应的理论 FEM 位移分别为 3%、4%和 5%模型的 5.8、5.4 和 5.0 μm。OARI 位移与 FEM 位移之间的偏差是由于用于跟踪位移的互相关算法的分辨率所致。据作者所知，这是第一个成功结合 OCT 和声辐射力源的探头。
OARI 探头具有提供有关模型和软组织的机械和光学特性信息的能力。这在早期上皮癌检测中可能很有用。由于探头的直径为 10 毫米，因此目前仅适用于皮肤和口腔应用。为了使其适用于其他内部部位的癌症检测，探头必须缩小尺寸。未来的工作将集中于利用相敏光学相干弹性成像来获得产生的 OARI 位移，提高探头的分辨率，并使医生能够更好地评估软组织的机械特性。
