Abstract
Presently, breast cancer diagnostic methods are dominated by mammography. Although drawbacks of mammography are present including ionizing radiation and patient discomfort, not many alternatives are available. Ultrasound (US) is another method used in the diagnosis of breast cancer, commonly performed on women with dense breasts or in differentiating cysts from solid tumors. Handheld ultrasound (HHUS) and automated breast ultrasound (ABUS) are presently used to generate reflection images which do not contain quantitative information about the tissue. This limitation leads to a subjective interpretation from the sonographer. To rectify the subjective nature of ultrasound, ultrasound tomography (UST) systems have been developed to acquire both reflection and transmission UST (TUST) images. This allows for quantitative assessment of tissue sound speed (SS) and acoustic attenuation which can be used to evaluate the stiffness of the lesions. Another imaging modality being used to detect breast cancer is photoacoustic tomography (PAT). Utilizing much of the same hardware as ultrasound tomography, PAT receives acoustic waves generated from tissue chromophores that are optically excited by a high energy pulsed laser. This allows the user to ideally produce chromophore concentration maps or extract other tissue parameters through spectroscopic PAT. Here, several systems in the area of TUST and PAT are discussed along with their advantages and disadvantages in breast cancer diagnosis. This overview of available systems can provide a landscape of possible intersections and future refinements in cancer diagnosis.
Highlights
As of 2020, breast cancer has surpassed lung cancer as the most diagnosed cancer worldwide, reaching 2.3 million new cases [1]
Compared to the structural information gleaned from transmission UST (TUST), photoacoustic tomography (PAT) provides functional information through monitoring tissue endogenous contrast agent total concentration and the potential for oxygen saturation measurement
We believe the future of breast cancer diagnosis is in the intersection of these two modalities in the form of an ultrasound/photoacoustic tomography (USPAT) system
Summary
As of 2020, breast cancer has surpassed lung cancer as the most diagnosed cancer worldwide, reaching 2.3 million new cases [1]. Used less frequently for breast cancer diagnosis, another diagnostic imaging system is magnetic resonance imaging (MRI), which can provide a three-dimensional volumetric image of the breast without ionizing radiation It cannot be part of routine screening since it requires a contrast agent, is more time consuming, and expensive when compared to mammography and US [14]. PAT can provide functional and molecular information by capitalizing on the photoacoustic effect This phenomenon uses light to excite both endogenous and exogenous chromophores, which absorb that optical energy and undergo the process of thermal elastic expansion, where a portion of that energy is converted into acoustic pressure waves. We hope that presenting the advantages and disadvantages of these systems along with our perspective on the future of USPAT can provide the reader with a landscape of systems which can lead to intersections and future refinements for cancer diagnosis
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