Lasers in Photoacoustics
People are fighting many wars. Some last shorter, some longer, but they eventually end. War with diseases lasts forever and takes it‘s toll annually. War with cancer is the one, which probably takes the biggest number of casualties. In the year 2018, according to the WHO (World Health Organization) cancer caused about 9.6 mln. deaths. Globally, about 1 in 6 deaths is due to cancer. Three most common cancers are: lung, breast and colorectal (WHO). Breast cancer is the most commonly occurring cancer in women and the second most common cancer overall. There were over 2 million new breast cancer cases in 2018. Breast cancer alone caused 627 000 deaths.
There are many contributing factors that cause cancer: physical, chemical, and biological carcinogens.
The American cancer society believes that early identification is the the key for saving lives.
Finding breast cancer early and getting state-of-the-art cancer treatment are the most important strategies to prevent deaths from breast cancer. Breast cancer that’s found early, when it’s small and has not spread, is easier to treat successfully. Getting regular screening tests is the most reliable way to find breast cancer early.
American Cancer Society
There are wide range of conventional technologies for early diagnostics: X-ray, Ultrasound, MRI and etc. Each one has it‘s own advantages and (unfortunately) disadvantages. For instance, X-ray provides sufficient spatial resolution while maintaining comparatively low cost and simple infrastructure, but employs ionizing irradiation and does not work as well with breasts with considerable amount of glandular tissues. Ultrasound is safe, comparatively easy to use, has high resolution, but lacks sensitivity.
For breast cancer early diagnosis, X-ray mammography is the only technique found sensitive enough for screening. Unfortunately it has a low positive predictive value (PPV) with unnecessary secondary investigations including biopsies. False positives (incorrectly signalling the presence of disease) and false negatives (incorrectly signalling the absence of disease) create many issues at the physical, psychological and even economical levels.
To overcome, these drawbacks brand new technologies are being developed. One of these is Photoacoustic imaging. Photoacoustic imaging is one of the fastest-growing research areas of non-invasive, high-resolution and high-contrast visualization of both superficial and deep tissues.
Photoacoustic imaging employs the physical property of molecules to briefly heat up and cool down while absorbing a very short pulse of light of a certain wavelength.
Photoacoustic imaging employs the physical property of molecules to briefly heat up and cool down while absorbing a very short pulse of light of a certain wavelength. While heating up, the molecules expand and while cooling down, they contract. This creates an ultrasound wave which can be captured by ultrasound transducers enabling the ability to locate the origin of sound.
While heating up, the molecules expand and create an ultrasound wave which can be captured by ultrasound transducers enabling the ability to locate the origin of sound. The penetration of light into tissue depends on the tissue properties and the pulse energy of the light. Moreover, different chromophores in the tissue can absorb light of different wavelengths, thus giving functional visual information.
Even though the first photoacoustic image was generated almost two decades ago [Oraevsky et al 2001], due to it s potential in providing high specificity, contrast and image resolution, all at comparatively low cost, interest in Photoacoustic imaging is considered promising and gaining exceptional interest.
New start-ups and various EU funded projects have been raised over several years. One of these is PAMMOTH.
PAMMOTH (acronym of Photoacoustic Mammoscopy for evaluating screening-detected lesions in the breast) is an EU-funded consortium featuring synergy from universities and private companies among 9 members. The consortium is dedicated to creating new tools for early stage detection of breast cancer.
PAMMOTH’s objective is to develop, validate and begin exploitation of a dedicated breast imaging device for a significant impact in breast cancer diagnosis. The proposed device combines non-invasive 3D photoacoustic imaging and ultrasound imaging. The device will provide near real-time, full-breast, multimodal images to the radiologist. From the ultrasound mode, the radiologist will visualize anatomical features and extent of tumors, and from multiwavelength photoacoustics, she or he will see tumor vascularity. Quantitative spectroscopic photoacoustic images will be extracted off-line, providing the radiologist with information relating to tumor physiology and function such as angiogenesis and hypoxia.
For this project we needed customised solution, which was not available on the market among standard „of-the-shelf“ laser systems. We were glad to partner with EKSPLA to tailor their tunable wavelength laser system for this specific application. System delivered needed parameters as well as functionality, so we can keep on with project milestones.
prof. Dr. Srirang Manohar
Professor of Mult-modality medical imaging, Technical Medical Centre at the University of Twente.
In that project, Ekspla’s mission is to design and provide tunable wavelength laser sources for sample irradiation.
„For this project we needed customised solution, which was not available on the market among standard „of-the-shelf“ laser systems. „ – mentioned prof. Dr. Srirang Manohar, Professor of Mult-modality medical imaging, Technical Medical Centre at the University of Twente – „We were glad to partner with EKSPLA to tailor their tunable wavelength laser system for this specific application. System delivered needed parameters as well as functionality, so we can keep on with project milestones“.
„This laser system is unique because for this class of lasers, it has an OPO with the most energy per pulse in the world. Being delivered into many output channels it helps to ensure homogenous and efficient illumination of the breast and discover breast cancer at the very early stage while detecting typical vascularity of tumors.“ – explained Aldas Juronis, program manager at EKSPLA.
Utilizing many years of experience in the development and production of tunable wavelength, high energy lasers, EKSPLA introduced PhotoSonus series laser sources, which were designed to be used in advanced photoacoustic imaging systems. These laser sources have a wide wavelength range of 660 – 2300 nm, up to 250 mJ of pulse energy and the capability of fiber coupling of the output beam. This makes them the perfect choice for any photoacoustic imaging system for irradiating tissues and other materials.
This laser system is unique because it is one of the most energy producing OPOs in the world. Being delivered into many output channels, it helps to ensure homogenous and efficient illumination of the breast and discover breast cancer at the very early stage while detecting typical vascularity of tumor germ.
Program manager at EKSPLA
A unique, fast-wavelength switching option enables each laser pulse to have a different wavelength in almost any sequence. This is very useful while tracking changes in molecular properties within a short time period.
Photoacoustic imaging is proven to be very effective in diagnosing breast tumors, skin cancer, thyroid nodules, osteoarthritis and rheumatoid arthritis, early diagnosis of blood vessel disorders and many more. Photoacoustic imaging can also be used for visualization of non-living objects, such as nondestructive inspection of the internal structure and property changes of composite materials and food inspection.