A pinboard by
Nasim Abdollahi

Ph.D. Candidate, University of Manitoba


An Innovative Medical Imaging Technique for Monitoring Breast Cancer Treatment

The diagnosis and treatment of cancer has been a major focus of medical research for decades. As technology and methodologies advance, we continue to improve medical imaging practices by increasing the resolution and sensitivity of images, while attempting to make imaging techniques less harmful and more comfortable for patients. Microwave Tomography (MWT) is a low-cost, portable alternative to conventional imaging techniques such as magnetic resonance imaging (MRI), computed tomography (CT) and X-ray mammography. Using safe, non-ionizing radiation makes MWT ideal for the diagnosis of breast cancer and the monitoring of its treatment. We aim to design a pre-clinical procedure for breast cancer imaging which is an effective tool for monitoring tumour response to chemotherapy and radiation treatment. This imaging technology will provide us with valuable information for diagnosing the tumour type, and allow us to track changes in size during treatment. The goal is to push this emerging science forward, and contribute in making it a safe and affordable technology, clinically available in the near future.


A study of matching fluid loss in a biomedical microwave tomography system.

Abstract: Effective imaging of human tissue with microwave tomography systems requires a matching fluid to reduce the wave reflections at the tissue boundary. Further, in order to match the idealized mathematical model used for imaging with the complicated physical measurement environment, loss must be added to the matching fluid. Both too little and too much loss result in low-quality images, but due to the nonlinear nature of the imaging problem, the exact nature of loss-to-image quality cannot be predicted a priori. Possible optimal loss levels include a single, highly sensitive value, or a broad range of acceptable losses. Herein, the authors outline a process of determining an appropriate level of loss inside the matching fluid and attempt to determine the bounds for which the images are the highest quality.Our biomedical microwave tomography system is designed for 2D limb imaging, operating from 0.8 to 1.2 GHz. Our matching fluid consists of deionized water with various levels of loss introduced by the addition of table salt. Using two homogeneous tissue-mimicking phantoms, and eight different matching fluids of varying salt concentrations, the authors introduce quantitative image quality metrics based on L-norms, mean values, and standard deviations to test the tomography system and assess image quality. Images are generated with a balanced multiplicative regularized contrast source inversion algorithm. The authors further generate images of a human forearm which may be analyzed qualitatively.The image metrics for the phantoms support the claim that the worst images occur at the extremes of high and low salt concentrations. Importantly, the image metrics show that there exists a broad range of salt concentrations that result in high-quality images, not a single optimal value. In particular, 2.5-4.5 g of table salt per liter of deionized water provide the best reconstruction quality for simple phantoms. The authors argue that qualitatively, the human forearm data provide the best images at approximately the same salt concentrations.There exists a relatively large-range of matching fluid losses (i.e., salt concentrations) that provide similar image quality. In particular, it is not necessary to spend time highly optimizing the level of loss in the matching fluid.

Pub.: 08 Feb '13, Pinned: 31 Aug '17