Pandey Prabodh Kumar, Gonzalez Gilberto, Cheong Frederick, Chen Ce-Belle, Bettiol Andrew A, Chen Yong, Xiang Liangzhong
Department of Radiological Sciences, University of California, Irvine, California 92697, USA.
Department of Radiation Oncology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Appl Phys Lett. 2024 Jan 29;124(5):053702. doi: 10.1063/5.0188650. Epub 2024 Feb 2.
Visualizing micro- and nano-scale biological entities requires high-resolution imaging and is conventionally achieved via optical microscopic techniques. Optical diffraction limits their resolution to ∼200 nm. This limit can be overcome by using ions with ∼1 MeV energy. Such ions penetrate through several micrometers in tissues, and their much shorter de Broglie wavelengths indicate that these ion beams can be focused to much shorter scales and hence can potentially facilitate higher resolution as compared to the optical techniques. Proton microscopy with ∼1 MeV protons has been shown to have reasonable inherent contrast between sub-cellular organelles. However, being a transmission-based modality, it is unsuitable for studies and cannot facilitate three-dimensional imaging from a single raster scan. Here, we propose proton-induced acoustic microscopy (PrAM), a technique based on pulsed proton irradiation and proton-induced acoustic signal collection. This technique is capable of label-free, super-resolution, 3D imaging with a single raster scan. Converting radiation energy into ultrasound enables PrAM with reflection mode detection, making it suitable for imaging and probing deeper than proton scanning transmission ion microscopy (STIM). Using a proton STIM image of HeLa cells, a coupled Monte Carlo+k-wave simulations-based feasibility study has been performed to demonstrate the capabilities of PrAM. We demonstrate that sub-50 nm lateral (depending upon the beam size and energy) and sub-micron axial resolution (based on acoustic detection bandwidth and proton beam pulse width) can be obtained using the proposed modality. By enabling visualization of biological phenomena at cellular and subcellular levels, this high-resolution microscopic technique enhances understanding of intricate cellular processes.
可视化微米和纳米尺度的生物实体需要高分辨率成像,传统上是通过光学显微镜技术实现的。光学衍射将其分辨率限制在约200纳米。使用能量约为1兆电子伏特的离子可以克服这一限制。这种离子能穿透组织中的几微米,其德布罗意波长要短得多,这表明与光学技术相比,这些离子束可以聚焦到更短的尺度,因此有可能实现更高的分辨率。已证明,使用能量约为1兆电子伏特的质子进行质子显微镜检查时,亚细胞器之间具有合理的固有对比度。然而,作为一种基于透射的成像方式,它不适用于某些研究,并且无法通过单次光栅扫描实现三维成像。在此,我们提出质子诱导声学显微镜(PrAM),这是一种基于脉冲质子辐照和质子诱导声学信号采集的技术。该技术能够通过单次光栅扫描实现无标记、超分辨率的三维成像。将辐射能量转换为超声波,使PrAM能够采用反射模式检测,使其适用于成像和探测比质子扫描透射离子显微镜(STIM)更深的区域。利用HeLa细胞的质子STIM图像,基于蒙特卡罗+k波耦合模拟进行了可行性研究,以证明PrAM的能力。我们证明,使用所提出的成像方式可以获得横向小于50纳米(取决于束尺寸和能量)和轴向亚微米分辨率(基于声学检测带宽和质子束脉冲宽度)。通过实现细胞和亚细胞水平生物现象的可视化,这种高分辨率显微镜技术增强了对复杂细胞过程的理解。