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.
A detailed analysis of the optical reflectivity of a monolithic, T-shaped surface relief grating structure is carried out. It is shown that by changing the groove depths and widths, the frequency-dependent reflectivity of the diffraction grating can be greatly modified to obtain various specific optical elements. The basic T-shaped grating structure is optimized for three specific applications: a perfect mirror with a wide maximal reflection plateau, a bandpass filter, and a dichroic beam splitter. These specific mirrors could be used to steer the propagation of bichromatic laser fields, in situations where multilayer dielectric mirrors cannot be applied due to their worse thermomechanical properties. Colored maps are presented to show the reflection dependency on the variation of several critical structure parameters. To check the accuracy of the numerical results, four independent methods are used: finite-difference time-domain, finite-difference frequency-domain, method of lines, and rigorous coupled-wave analysis. The results of the independent numerical methods agree very well with each other indicating their correctness.
It is shown that the classical and quantum mechanical description of first and second order nonlinear optical processes (including squeezing) are equivalent in the sense that in both cases an initial phase space distribution transforms in the same manner. We investigate in detail the degenerate three wave mixing, which is a third order process, and point out that the classical and quantum descriptions give essentially different results. This process yields three-pointed star states. It is pointed out that the efficiency of the star state in a three photon process is superior to that of a coherent state with two orders of magnitude.
Conference Committee Involvement (1)
Fluctuations and Noise in Photonics and Quantum Optics II
26 May 2004 | Maspalomas, Gran Canaria Island, Spain
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