University of Twente Student Theses


Testing of Annular Illumination Probe for Photoacoutic Imaging of Radio-Frequency Ablation

Rascevska, E. (2019) Testing of Annular Illumination Probe for Photoacoutic Imaging of Radio-Frequency Ablation.

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Abstract:Majority of liver cancer patients are not eligible for liver resection. One of the most common therapeutic choices for non-resectable tumors is radio frequency ablation (RFA), however, it is associated with high recurrence rates. It is mainly originating from insufficient intra-operative feedback about the ablated tissue margins. Currently available imaging modalities are not capable to visualise or detect these margins in real-time with reasonable contrast, high sensitivity and in a cost effective way. Moreover, commonly used ultrasound imaging guidance for interventional procedures suffers from multiple artifacts and poor acoustics contrast for structures of interest, such as, blood vessels and tumor. Photoacoustic imaging is known to be highly sensitive to changes in optical properties resulting from chemical transformations in ablated tissue. Additionally, it offers high contrast to absorbing structures and objects, such as, blood vessels, hypervascularized tumors and metallic needles, making it interesting for applications in radiofrequency ablation. Herein, we present an interstitial illumination approach for deep tissue illumination with use of custom-made annular illumination probe to enable photoacoustics imaging of RFA in liver. In this proof of concept study we characterize this probe and investigate visualisation of an absorbing target, blood vessels, RFA needle and ablation lesions. Preliminary experiments conducted revealed feasibility of this imaging concept for needle guidance and visualisation of highly absorbing structures mimicking blood vessels and tumor in ex-vivo chicken breast and bovine liver tissues. Visualisation of RFA needle tines was feasible in tissue mimicking phantoms and ex-vivo tissue with low absorbance, tine visualisation in highly absorbing media remains challenging. For enabling intra-operative photoacoutic imaging of RFA in liver implementation of more suitable reconstruction algorithms, investigations of coatings for RFA needle and more homogeneous fluence distribution is needed.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:44 medicine
Programme:Biomedical Engineering MSc (66226)
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