Transurethral Shear Wave Elastography (TU-SWE) for Prostate Cancer Diagnosis

Lead Research Organisation: University College London
Department Name: Mechanical Engineering


Prostate Cancer (PCa) is the most common cancer in men in the UK. It is also the second cause of cancer death after lung cancer. It represents around 13% of all cases of cancer and accounts for 7% of all UK cancer deaths. The incidence of PCa increases with age, affecting mainly men over 50 years of age. Prostate carcinoma is often suspected when the serum Prostate-Specific Antigen (PSA) is elevated or an abnormal digital rectal examination is noted. However, PSA screening leads to a substantial number of unnecessary biopsies in patients with no or indolent cancer, who do not need immediate treatment. Despite the low specificity of PSA testing and the uncertainty after negative systematic biopsies, these techniques remain the standard for PCa diagnosis.

Current research is investigating whether modern imaging techniques can identify the site of the tumour. There are two main streams that are showing promising preliminary results: Magnetic Resonance Imaging (MRI) and Elastography techniques. MRI is showing promising results, particularly when using a multi-parametric approach (mpMRI), but its high cost and limited availability hold back its wider use, particularly in resource-poor parts of the world. Prostate Elastography is an emerging imaging modality, which consists of the evaluation of prostate stiffness. Analogous to the cellular processes of wound repair, it is generally believed that normal tissue stroma responds in an effort to repair damage due to carcinoma cell invasion. It has been concluded that the stromal reaction is also characterized by elevated collagen deposition. Since increasing collagen deposition leads to an increase in the tumour rigidity, this suggests that quantitative stiffness estimations may prove to be an effective biomarker for assessing PCa grade and identification of more aggressive cancers.

With regards to treatment options, radical surgery and whole-gland therapies remain controversial for treatment of localised prostate cancer due to the possibility of genitourinary and rectal side-effects as a consequence of damaging contiguous tissues. Focal therapies, such as High Intensity Focused Ultrasound (HIFU), Vascular Targeted Photodynamic Therapy, Radiofrequency Ablation and Cryotherapy are emerging as suitable methods for treating localised unifocal and multifocal cancer lesions in the prostate while reducing side-effects. However, their successful application would be benefited greatly by an intraoperative monitoring system. Despite the promising future, the final target is still usually the whole or half volume of the gland, mainly due to the uncertainty of the exact location and contour of the tumour and the treated area. In such focal ablation therapies, tissue stiffness undergoes a dramatic increase due to coagulative necrosis. This encourages further investigation of elastography as a method for monitoring thermal ablation in the prostate.

The aim of this study is to develop a system and prove the feasibility of using a Transurethral-Shear Wave Elastography (TU-SWE) approach for diagnosis and ablation monitoring of PCa. The applicants have demonstrated the proof-of-concept for the method using a scaled version of a novel disposable probe and the image reconstruction software. The next stage of the work will see the production of a TU-SWE medical prototype probe with its electronic control system following the same fabrication processes established for the proof-of-concept laboratory prototype. Improvement of the software for image reconstruction will include extending the model of wave propagation to a realistic 3D geometry and using machine learning to enhance the image resolution with data from a parallel clinical study.

This diagnostic and treatment monitoring tool will thus lead to earlier detection of prostate cancers and more efficacious and therefore cost-effective cancer treatments, saving the NHS time, resources and money.


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