Marion Adrien, Boutet Jérôme, Debourdeau Mathieu, Dinten Jean-Marc, Vray Didier
Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Université Lyon 1, France.
Annu Int Conf IEEE Eng Med Biol Soc. 2011;2011:7211-4. doi: 10.1109/IEMBS.2011.6091822.
During the last decade, a new modality called photoacoustic imaging has emerged. The increasing interest for this new modality is due to the fact that it combines advantages of ultrasound and optical imaging, i.e. the high contrast due to optical absorption and the low acoustic attenuation in biological tissues. It is thus possible to study vascularization because blood has high optical absorption coefficient. Papers in the literature often focus on applications and rarely discuss quantitative parameters. The goal of this paper is to provide quantitative elements to design an acquisition setup. By defining the targeted resolution and penetration depth, it is then possible to evaluate which kind of excitation and reception systems have to be used. First, we recall theoretical background related to photoacoustic effect before to describe the experiments based on a nanosecond laser at 1064 nm and 2.25-5 MHz transducers. Second, we present results about the relation linking fluence laser to signal amplitude and axial and lateral resolutions of our acquisition setup. We verify the linear relation between fluence and amplitude before to estimate axial resolution at 550 μm for a 2.25 MHz ultrasonic transducer. Concerning lateral resolution, we show that a reconstruction technique based on curvilinear acquisition of 30 lines improves it by a factor of 3 compared to a lateral displacement. Future works will include improvement of lateral resolution using probes, like in ultrasound imaging, instead of single-element transducers.
在过去十年中，一种名为光声成像的新模态出现了。对这种新模态的兴趣与日俱增，这是因为它结合了超声成像和光学成像的优点，即由于光吸收产生的高对比度以及生物组织中的低声衰减。因此，由于血液具有高光吸收系数，所以有可能研究血管生成。文献中的论文通常侧重于应用，很少讨论定量参数。本文的目的是提供定量要素以设计采集装置。通过定义目标分辨率和穿透深度，进而可以评估必须使用哪种激发和接收系统。首先，在描述基于1064 nm纳秒激光和2.25 - 5 MHz换能器的实验之前，我们回顾与光声效应相关的理论背景。其次，我们展示关于激光能量密度与信号幅度以及我们采集装置的轴向和横向分辨率之间关系的结果。在估计2.25 MHz超声换能器在550 μm处的轴向分辨率之前，我们验证了能量密度与幅度之间的线性关系。关于横向分辨率，我们表明与横向位移相比，基于30条线的曲线采集的重建技术将其提高了3倍。未来的工作将包括像在超声成像中那样，使用探头而非单元素换能器来提高横向分辨率。
