Synchronized Imaging Acquisition System with Video-rate Third-harmonic-generation Microscopy
Date Issued
2013
Date
2013
Author(s)
Li, Tse-Chung
Abstract
Complete blood count (CBC) is a routine examination conducted in hospitals. It has an essential function in diagnosing diseases. CBC requires drawing blood from patients, which is an invasive method. This medical procedure requires patients to wait for the test results. Thus, having an on-site measurement method for blood cell counts to avoid the invasive drawing of blood and real-time analysis to save waiting time is highly desired. Compared to other types of medical imaging, optical microscopy has superior performance on sub-cellular resolution (200 nm to 300 nm) in general. It also has high frame rate and high sensitivity. Combined with staining or labeling dye, molecular information can be visualized in a microscopic scale. These features make optical microscopy an indispensible diagnostic tool for observing sub-cellular morphology and cellular dynamics.
Nowadays, with the capability of sub-micron three-dimensional (3D) spatial resolution, nonlinear optical microscopies, such as two-photon fluorescence microscopy (2PFM) and harmonic generation microscopy (HGM), have been widely used for in vivo biological studies. Compared with 2PFM, HGM is a less invasive optical microscopic technique, which makes it more suitable for clinical applications. HGM can also be used to observe sub-cellular morphology without extra labeling. Thus, HGM is suitable for observing cellular dynamics in vivo. In terms of imaging acquisition, although 2PFM is an incoherent process, the sampled intensity will still be sufficiently high without synchronous sampling because of its high signal intensity. For harmonic generation microscopy, which has low signal intensity, synchronous sampling is necessary in high-speed scanning applications to obtain high-quality images.
In this thesis, based on the third harmonic generation (THG) microscope system in our laboratory, the synchronous imaging acquisition system was built using the coherent feature of the TGH to improve the SNR of the image. We replaced the commercial frame-grabber with a field-programmable gate array (FPGA). Taking the flexibility of the FPGA, we designed acquisition and transfer functions, such as a frame-grabber. By using the PLL in FPGA and with the help of the comparator, we synchronized the sampling clock with the laser pulse. On the other hand, basing on the MFC, we programmed a graphical user interface with two-channel 30Hz frame rate windows to display and restore the image. The interface could adjust FPGA parameters, such as frame rate and time delay. We also provided a different acquisition mode, which is called MAX mode, to prevent the low intensity induced by shot noise. Several basic image process functions are also provided.
With the aid of this synchronous imaging acquisition system, we can clearly observe the blood cells in human blood capillaries. We hope that for future clinical applications, the non-invasive automatic evaluation of speed and number of blood cells using the THG microscope system could be faster and more precise using this synchronous acquisition system.
Subjects
同步影像擷取
三倍頻
雷射
訊噪比
血液常規
顯微術
SDGs
Type
thesis
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