Each year, about 30% of all newly diagnosed cancer cases in women worldwide are breast cancers [1]. One of the most common techniques for breast cancer diagnosis is mammography. However, this technique provides limited functional information regarding breast tissue morphology. In cases of suspected malignancy invasive techniques such as biopsy are implemented.
In this work an optical deep tissue imaging technique called ultrasound optical tomography (UOT) which combines laser light and ultrasound is implemented for a non-invasive lesion (tumour) characterization in breast tissue.
The experiments were performed using 794 nm laser wavelength, 6 MHz ultrasound frequency and a narrowband spectral filter material, Tm3+:LiNbO3. The measurements were carried out in 5 cm thick agar phantoms using a range of tumor mimicking inclusions of 3 different sizes.
This work is the first deep tissue imaging demonstration using UOT at tissue relevant wavelengths. Current results indicate that the UOT technique can become an important and valuable tool for lesion characterization in breast tissue.
Ultrasound Optical Tomography (UOT) combines the high-resolution imaging capability of ultrasound with measurements of light absorption and scattering properties of human tissue. This non-invasive technique could distinguish between cancerous and non-cancerous lesions inside the breast tissue, follow tumor shrinkage during pre-operative treatment, or provide information on blood oxygenation levels. Recent measurements of phantoms mimicking the optical properties of breast tissue with various lesions indicated that the technique can probe 50 mm deep through the tissue. This work concentrates on developing the UOT setup in transmission mode and discusses its advantages, limitations, and possible improvements.
Optical imaging utilize light to analyze biological tissues in detail, non-invasively and without harmful radiation. Examples include ultrasound optical tomography and photoacoustic imaging; both use a limited number of wavelengths. Diffuse reflectance spectroscopy, another optical technique, covers a continuous wavelength range, but without generating an image. This study focuses on extended-wavelength DRS (450 to 1550nm) to compare healthy breast tissue with different subgroups of breast cancer. Analysis of 13 breast specimens with invasive ductal or lobular carcinoma reveals distinct optical profiles in tumor subgroups compared to healthy tissue. However, absorption and scattering patterns are similar among the tumor subgroups.
We propose a novel analytical time-domain model for migration of Raman scattered photons in inhomogeneous two-layer diffusive media. Based on this model, the methods for reconstruction of the Raman spectra of the two layers are developed, tested in simulations and validated on phantom measurements data.
Diffuse reflectance spectroscopy (DRS) with a fiber-optic contact probe is a cost-effective, rapid, and non-invasive optical method used to extract diagnosis information of tissue. By combining commercially available VIS- and NIR-spectrometers with various fiber-optic contact-probes, we have access to the full wavelength range from around 400 to 1600 nm. Using this flexible and portable spectroscopy system, we have acquired ex-vivo DRS-spectra from murine, porcine, and human liver tissue. For extracting the tissue optical properties from the measured spectra, we have employed and compared predictions from two models for light propagation in tissue, diffusion theory model (DT) and Monte Carlo simulations (MC).
The focus in this work is on the capacity of this DRS-technique in discriminating metastatic tumor tissue from normal liver tissue as well as in assessing and characterizing damage to non-malignant liver tissue induced by preoperative chemotherapy for colorectal liver metastases.
Diffuse reflectance spectroscopy (DRS) is a rapid, non-invasive optical method widely adopted to gain diagnostic information of tissue. The most flexible approach to this method is a fiber-optic contact-probe used with a spectroscopy system. A challenge of this method is that the external pressure brought by the probe can significantly affect the tissue optical properties as well as the light coupling into the probe, and thus influence the collected DRS-spectrum. In this study we investigate and characterize the effect of probe pressure on DRS-spectra obtained with a calibrated loaded-spring system used with a fiber optic probe in the range (400 − 1600) nm. A multilayer FE-model of the indentation is developed to get a better insight of the distribution of pressure and stresses inside the skin under indentation.
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