The world’s first high resolution, 3D pictures of the flexibility of living tissues could lead to significant advances in disease detection, according to Brendan Kennedy and colleagues from the University of Western Australia.
Diseased tissues such as tumours give themselves away because they tend to be stiffer than surrounding healthy cells. Doctors can try to “feel” this variation in stiffness, but the new images produced at UWA promise a much higher resolution and more objective assessment of this property.
The team’s rapidly-acquired pictures of a lacerated finger are the first step towards clinical trials for the technique, the researchers say.
Imaging Tissue Mechanical Properties with Optical Coherence Elastography
Brendan F. Kennedy1, Robert A. McLaughlin1 and David D. Sampson1,2
1Optical+Biomedical Engineering Laboratory, School of Electrical, Electronic and Computer Engineering,
2Centre for Microscopy, Characterisation & Analysis, The University of Western Australia, 35 Stirling Highway, Crawley,
Western Australia 6009, Australia
Optical coherence elastography (OCE) is a biomedical imaging technique which measures tissue mechanical properties with microscopic resolution. In OCE, tissue response to mechanical perturbation is quantitatively imaged using optical coherence tomography.
In many instances, the mechanical properties of pathological tissue are very different to those of healthy tissue. For example, cancer is commonly detected by the increased stiffness of the tumour in comparison with the surrounding tissue. Manual palpation is routinely performed by physicians to ‘feel’ this variation in tissue mechanical properties. Although palpation is a vital tool, it is limited by its subjectivity and low resolution. Much research has focused on using the mechanical properties of tissue as a contrast mechanism to form images; a technique known as elastography . Elastography is performed by introducing mechanical excitation to tissue and measuring the resultant tissue displacement, which depends on its elasticity. Initial elastography research focused on using ultrasound and magnetic resonance imaging (MRI) as the underlying imaging modalities. More recently an optical technique has been developed, namely optical coherence elastography (OCE), which uses optical coherence tomography (OCT) as the underlying imaging modality [2,3]. The spatial resolution of OCE, determined by OCT, is typically 1-10 m; at least an order of magnitude higher than ultrasound- and MRI-based elastography techniques. OCT is an optical imaging technique, based on low-coherence interferometry, which is analogous to ultrasound, where backscattering of light waves from inside tissue is used to form images rather than echoes of sound waves.
II. RESULTS AND DISCUSSION
We present the world’s first in vivo OCE images, obtained from the human finger. To facilitate in vivo measurements, mechanical excitation and imaging were performed from the same side of the sample using a ring actuator. Mechanical excitation was introduced to skin and the resultant displacement and strain were measured using an OCT system. A photograph of a finger, showing a superficial laceration, is presented in Fig. 1(a). An OCT image of the same region of skin is presented in Fig. 1(b); the laceration appears on the right-hand side of this image. Mechanical excitation was introduced to the finger using a ring actuator probe. The displacement and local strain of the skin were measured using an OCT system. The displacement is significantly reduced in the region of the laceration, as can be seen in Fig. 1(c) and, as expected due to the increased stiffness of the laceration, so is the strain, presented in Fig. 1(d). We will present recent advances we have made, including the ability to perform high-speed, high resolution in vivo OCE imaging. This has allowed us to perform 3-dimensional OCE imaging for the first time. This is an important step towards future clinical trials.
REFERENCES J. F. Greenleaf, M. Fatemi, and M. Insana, “Selected methods for imaging elastic properties of biological tissues,” Annu. Rev. Biomed. Eng. 5(1), 57–78 (2003).  B. F. Kennedy, T. R. Hillman, R. A. McLaughlin, B. C. Quirk, and D. D. Sampson, “In vivo dynamic optical coherence elastography using a ring actuator,” Opt. Express 17(24), 21762–21772 (2009).  S. G. Adie, B. F. Kennedy, J. J. Armstrong, S. A. Alexandrov, and D. D. Sampson, “Audio frequency in vivo optical coherence elastography,” Phys. Med. Biol. 54, 3129–3139 (2009).
Brendan Kennedy firstname.lastname@example.org