Research On The Imaging System And Reconstruction Algorithm Of Photoacoutic And Thermoacoustic Tomography

Photoacoustic and thermoacoustic imaging based on photoacoustic effect, maps thedistribution of absorption within biological tissues by reconstructing image use of thecaptured ultrasonic signals. The ultrasound-mediated method, which takes theadvantages of both high resolution and contrast, has the potential biomedicalapplications, and is developing as an international hotspot research in the field ofmedical imaging.In the dissertation, the experimental system and reconstruction algorithm areperformed for photoacoustic and thermoacoustic imaging based on the prior work ofour research team. Several practical study tasks are presented, such as: anunit-element distributed photoacoustic imaging (PAI) system, a multi-element PAIsystem based on CTS-200 platform, a high-speed PAI system based on CTS-5000platform, a modified FBP (mFBP) algorithm with combination wavelet for highantinoise PAI, a microwave-induced thermoacoustic imaging (MITT) system, whosehardware system and software programme with LabVIEW and MATLAB languageare also designed and realized. These studies have built necessary theoretical andexperimental bases for further investigations of the early stage diagnosis of cancer, invivo monitoring of the tumour therapy, the cerebral structural and functional imagingof small animals and fast foreign body detection. The tasks are summarized asfollows:1. The design of unit-and multi-element PAI system is presented. The PCI-GPIBand PCI-1757UP are used as the hardware basic of modified unit-element PAIsystem, which is composed of a needle PVDF hydrophone, signal preamplifier,oscilloscope, tunable laser, stepping motor and personal computer. Based on theCTS-200 platform, a fast multi-element PAI system is designed, which iscomposed of an Nd: YAG laser, EUZ-PL23 transducer, multi-element lineartransducer array system (MLTAS), NI USB-5102, PCI-1730, custom-builtcontroller and personal computer. Based on the CTS-5000 platform, a modularinstrument of PCI-6541 is used as the hardware basic of high-speed PAI system, which is composed of a signal detecting module, data collecting and controllingmodule, data pre-processing module, OPO tunable laser, stepping motor andpersonal computer.2. The high antinoise mFBP photoacoustic reconstruction algorithm based onwavelet transform is developed, and successfully applied to PAl of simulatedphantom, in situ and in vivo tissue. The modified algorithm has much higherantinoise capacity, and can greatly improve the reconstruction image quality.3. The theoretical analysis and system design of MITT system is investigated. A fastMITT system based on a 320-element phase-controlled focus linear transducerarray, and successfully performed two-dimensional tissue thermoacousticimaging. The system with multi-element linear transducer array to capturethermoacoustic signals can avoid the full-view rotation of transducer, which canimprove the system stability and time-resolution. Using phase-controlled focustechnique to reconstruct the distribution of the microwave absorption, which canprovide higher image contrast and antinoise capacity.