Photoacoustic imaging with clinical, preclinical, and quantitative applications

Breathnach, Aedán
Photoacoustic (PA) imaging (PAI) is an emerging biomedical imaging modality that combines optical absorption contrast with ultrasonic resolution and imaging depth. Major research has been carried out into PAI in recent years, and as a result PAI is rapidly being established as a mainstream imaging modality in both biological research and clinical practice. In this thesis, three main areas of PAI application were studied: clinical, preclinical, and quantitative PAI. Handheld linear-array PAI was introduced to the clinic for breast and melanoma imaging applications. For the breast study, PAI using was assessed in terms of its ability to image the morphology and oxygenation status of breast lesions suspicious for cancer. PAI was found to image the morphology of superficial lesions with high contrast, while functional imaging found strong evidence of tumour hypoxia indicating malignancy. For the melanoma imaging study, PAI was applied to preoperatively measure lesion thickness of pigmented cutaneous lesions suspicious for melanoma. The PAI measured lesion thickness was found to corelate strongly with the histologically measured lesion thickness, indicating the efficacy of PAI in guiding biopsy depth and sample location. Additionally, PAI was found to be effective at imaging intradermal lesion growth which has important implications for melanoma staging. A method of correcting for the effects of spectral fluence attenuation on quantitative PA measurements was introduced in chapter 3. The method uses arteries as a known optical calibration standard to estimate optical fluence at nearby veins and to quantify venous blood oxygen saturation. The method was experimentally validated in coupled Monte-Carlo-PA simulations, phantom, and in vivo tests. Finally, the PA image contrast capabilities of novel gold nanostars (GNS) were tested in phantom and in vivo studies. The results showed the addition of a silica coating increased photothermal transfer and hence PAI contrast, while the in vivo study showed the strong photostability and low tissue clearance of the particles after GNS-mediated photothermal therapy in a mouse-tumour model.
NUI Galway
Publisher DOI
Attribution-NonCommercial-NoDerivs 3.0 Ireland