Mr. Hamed Peikari Profile

Hamed Peikari

at Queen's Univ

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Proceedings Article | 2 March 2011 Paper

Improved validation platform for ultrasound-based monitoring of thermal ablation

Hamed Peikari, Andras Lasso, Gabor Fichtinger

Proceedings Volume 7964, 79641H (2011) https://doi.org/10.1117/12.878333

KEYWORDS: Tissues, Pathology, Ultrasonography, Image segmentation, Cancer, Image restoration, Visibility, Computer simulations, Algorithm development, Image registration

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PURPOSE: Thermal ablation is a popular method in local cancer management; however it is extremely challenging to predict thermal changes in vivo. Ultrasound could be a convenient and inexpensive imaging modality for real-time monitoring of the ablation, but the required advanced image processing algorithms need extensive validation. Our goal is to design and develop a reliable test-bed for validation of these monitoring algorithms. METHOD: We previously developed a test-bed, consisting of ablated tissue sample and fiducial lines embedded in tissue-mimicking gel.1 The gel block is imaged by ultrasound and sliced to acquire pathology images. Following fiducial localization in both image modalities, the pathology and US data were registered. Ground truth ablated region is retrieved from pathology images and compared to the result of the ultrasound-based processing in 3D space. We improved on this platform to resolve limitations that hindered its usage in a larger-scale validation study. A simulator for evaluating and optimizing different line fiducial structures was implemented, and a new fiducial line structure was proposed. RESULTS: The new proposed fiducial configuration outperforms the previous in terms of accuracy, fiducial visibility, and use of larger tissue samples. Simulation results show improvement in pose recovery accuracy using our proposed fiducial structure, reducing target registration error (TRE) by 34%. Inaccurate pixel spacing information and fiducial localization noise are the main sources of error in slice pose recovery. CONCLUSION: A new generation of test-bed was developed, with software that does not require lengthy manual data processing, and is easier to maintain and extend. Further experimental work is required to optimize phantom preparation and precise pixel spacing computation.

Proceedings Article | 24 February 2010 Paper

Validation platform for ultrasound-based monitoring of thermal ablation

Alexandra Pompeu-Robinson, James Gray, Joshua Marble, Hamed Peikari, Jena Hall, Paweena U-Thainual, Mohammad Aboofazeli, Andras Lasso, Gabor Fichtinger

Proceedings Volume 7625, 76250T (2010) https://doi.org/10.1117/12.844053

KEYWORDS: Pathology, Tissues, Ultrasonography, Image segmentation, Scanners, Visualization, Temperature metrology, Clouds, 3D image processing, Cancer

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PURPOSE: A ground-truth validation platform was developed to provide spatial correlation between ultrasound (US), temperature measurements and histopathology images to validate US based thermal ablation monitoring methods. METHOD: The test-bed apparatus consists of a container box with integrated fiducial lines. Tissue samples are suspended within the box using agar gel as the fixation medium. Following US imaging, the gel block is sliced and pathology images are acquired. Interactive software segments the fiducials as well as structures of interest in the pathology and US images. The software reconstructs the regions in 3D space and performs analysis and comparison of the features identified from both imaging modalities. RESULTS: The apparatus and software were constructed to meet technical requirements. Tissue samples were contoured, reconstructed and registered in the common coordinate system of fiducials. There was agreement between the sample shapes, but systematic shift of several millimeters was found between histopathology and US. This indicates that during pathology slicing shear forces tend to dislocate the fiducial lines. Softer fiducial lines and harder gel material can eliminate this problem. CONCLUSION: Viability of concept was presented. Despite our straightforward approach, further experimental work is required to optimize all materials and customize software.

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