Abstract
Optical coherence elastography (OCE) has been proposed for a range of clinical applications. However, the majority of these studies have been performed using bulky, lab-based imaging systems. A compact, handheld imaging probe would accelerate clinical translation, however, to date, this had been inhibited by the slow scan rates of compact devices and the motion artifact induced by the user's hand. In this paper, we present a proof-of-concept, handheld quantitative micro-elastography (QME) probe capable of scanning a 6 × 6 × 1 mm volume of tissue in 3.4 seconds. This handheld probe is enabled by a novel QME acquisition protocol that incorporates a custom bidirectional scan pattern driving a microelectromechanical system (MEMS) scanner, synchronized with the sample deformation induced by an annular PZT actuator. The custom scan pattern reduces the total acquisition time and the time difference between B-scans used to generate displacement maps, minimizing the impact of motion artifact. We test the feasibility of the handheld QME probe on a tissue-mimicking silicone phantom, demonstrating comparable image quality to a bench-mounted setup. In addition, we present the first handheld QME scans performed on human breast tissue specimens. For each specimen, quantitative micro-elastograms are co-registered with, and validated by, histology, demonstrating the ability to distinguish stiff cancerous tissue from surrounding soft benign tissue.
Highlights
Using elastography to image the mechanical properties of tissue has the potential to aid in disease diagnosis and tissue characterization in a number of clinical applications [1,2,3]
2.3 Scan patterns we describe and compare the two scan patterns used to drive the microelectromechanical system (MEMS) mirror in the handheld probe: the standard unidirectional scan pattern and the custom bidirectional scan pattern. 2.3.1 Standard scan pattern The standard scan pattern is similar to that provided by the optical coherence tomography (OCT) probe manufacturer
The standard deviations in the mounted and custom scan pattern are much smaller than that in the standard scan pattern. This comparison demonstrates that the handheld images acquired with the custom scan pattern provide comparable image quality in both OCT images and micro-elastograms to the mounted scans, with minimal motion artifact observed
Summary
Using elastography to image the mechanical properties of tissue has the potential to aid in disease diagnosis and tissue characterization in a number of clinical applications [1,2,3]. Owing largely to the benefit of high resolution, rapid acquisition and the ability to generate 3D elastograms, the potential of OCE has been examined for a range of applications, e.g., in ophthalmology [8,9] and oncology [10,11]. OCE on skin was demonstrated in a quasi-handheld format where supporting apparatus was required to stabilize the probe [13]. A fully handheld probe would greatly facilitate the continued clinical development of OCE. There is no effective method to accurately and rapidly assess tumor on the microscale where it is often missed [19,20,21,22]
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