Downloaded 80 times
More Related Content
Similar to Laser ablation
Laser ablation
- 2. CONTENTS INTRODUCTION LITERATUREREVIEW LASER ABLATION HOW IS LASER ABLATION CARRIED OUT IMPORTANCE OF TEMPERATURE MONITORING LASER ABLATION SYSTEM LAYOUT DUAL CLAD FIBER OPTIC CABLE APPLICATION ADVANTAGES DISADVANTAGES FUTURE ADVANCEMENTS CONCLUSION REFERENCES
- 3. INTRODUCTION Cancer isthe second-leading cause of death globally accounting for 8.3 million deaths each year. Thermal ablation is generally classified into Radio-Frequency Ablation (RFA) Micro Wave Ablation (MWA) Laser Ablation (LA) Thermo-therapy can be effective for carcinomas, such as those in the liver, pancreas, kidneys and thyroid, to name the most relevant.
- 4. LA usesoptical fiber-based applicators to guide the laser beam into the tumor mass LITT allows more accurate and safe ablation of tumors located near high-risk sites. There are, however, limitations in LA too, mainly related to the control of the laser energy effect. Improvement in the therapy effectiveness can be obtained by careful monitoring of the induced temperature increase which is done through the fiber sensors based on Fiber Bragg Gratings (FBGs).
- 5. LITERATURE REVIEW Laserinterstitial thermal therapy (LITT) is a minimally invasive treatment modality for brain tumors that was first introduced by Bown in 1983 .The main limitations of this surgical technique where the inability to monitor or predict the extent of ablation, the inability to shape the ablation to conform to the tumor contour, and the lack of a cooling system. Commercial systems based on FOS were introduced for monitoring hyperthermal effects in the 1980s, later Vaguine and colleagues proposed a multi-probe optical sensors for MWA monitoring . In the late 1990s, Rao et al. fostered the use of FBGs for temperature monitoring during hyperthermia. They developed a novel system enclosing an FBG sensor array in a protective sleeve (diameter of 0.5 mm) to avoid measurement errors due to strain. The same group later tested an upgraded version of the system inside an MR scanner with a magnetic field of 4.7 T. The probe revealed a temperature resolution of 0.2 ºC and an accuracy of 0.8 ºC, for temperatures ranging from 25 ºC to 60 ºC.
- 6. One ofthe first applications of FBG for thermometry in LA was presented by Ding et al. in 2010, who developed a distributed FBG sensor with a length of 10 mm, encapsulated within a glass capillary, and used it to monitor temperature distribution in an ex vivo liver and in an in vivo mouse .The algorithm implemented was useful to dynamically control the temperature of the target at 43 ºC, and the temperature at the edge and outside the target at 38 ºC. Several studies have been carried out from 2012 to date by the group of Saccomandi and Schena, aiming to measure the temperature distribution in a pancreas undergoing LA, at different laser settings. They used non- encapsulated single-point FBGs of 10 mm length, and determined that FBGs do not experience any appreciable mechanical strain because of the relaxation of ex vivo tissue under its weight (error less than 1 ºC) . The same research group evaluated the influence of sensor length in the presence of a high thermal gradient. Recently, Liu et al. developed a laser applicator integrating FBG sensors for temperature measurement during LA. A double cladding fiber, i.e., a type of fiber commonly employed in the realization of high-power fiber lasers, has been exploited to combine laser beam delivery and sensing capability in the same fiber. The FBG showed response time of 50 ms.
- 7. LASER ABLATION Ablationliterally means “the removal of the body tissue”. Laser ablation is the process of removing material from a solid surface by irradiating it with laser beam, the material heated by the absorbed laser energy evaporates. Laser ablation is a hyperthermia based technique which uses laser optical fibers to deliver high energy laser radiation to the tissue. There are several laser types used in medicine for ablation, including argon, carbon dioxide (CO2), Nd:YAG, and others.
- 8. HOW IS LASERABLATION Carried OUT? LA is performed by using a laser and a medium which transports the laser light inside the tissue. The laser, which consists of a power source, a lasing medium, and reflecting mirrors, provides a monochromatic light (the light is emitted at a specific wavelength), whose wavelength defines the properties of the laser and the interaction with biological tissue. The medium is usually a small diameter (0.2–0.8 mm) flexible optical fiber that transports the laser light inside deep organs. Prolonged exposure of tumor cells at temperatures ranging from 45 °C to 55 °C or short exposure at temperature higher than 60 °C causes irreversible cell damage. Typical light wavelengths used for cancer removal are 980 nm (diode laser) and 1064 nm (Nd:YAG laser), which guarantee optimal penetration depth of light into the tissue.
- 9. IMPORTANCE OF TEMPERATUREMONITORING The common goal of the thermal treatments is selective tumor removal without damaging healthy tissue. Therefore, it is important that the accurate localization of the tumor is achieved . The tumor damage depends on both temperature and exposure time, since both the exposure time and temperature contribute to cell death . As a consequence, temperature monitoring during the procedure facilitates more accurate assessment of the region affected by thermal damage, hence temperature feedback may be particularly beneficial for on-line adjustment of the treatment settings during the procedure.
- 10. LAYOUT OF THELASER ABLATION SYSTEM WITH INTEGRATED TEPERATURE MEASUREMENT CAPABILITY
- 11. DUAL CLAD FIBEROPTIC CABLE The probe is made out of the dual cladding fiber, similar to those high power fiber lasers. Inner cladding is used to guide the laser ablation beam and core the sensing signal The diameter of the inner cladding will be 400µm is likely to be used for most of the applications as a compromise between invasive impact and mechanical robustness. The fiber bragg grating acting as temperature sensors are inscribed in the fiber core .
- 13. FIBER BRAGG GRATING Fiber Bragg Grating (FBG) technology is one of the most popular choices for optical fiber sensors for strain or temperature measurements due to their simple manufacture. Fiber Bragg grating (FBG) sensors are the most popular approach for modern fiber-optic sensing. An FBG is a wavelength-selective notch filter that reflects a narrow spectrum around a single peak wavelength. When temperature variations are applied to the FBG structure, the FBG spectrum shifts with near- perfect constant sensitivity. Hence, the wavelength that corresponds to the maximum value of the reflected spectrum intensity, called the Bragg wavelength (λB) can be used to estimate the temperature.
- 14. APPLICATION Laser ablationis used in a variety of medical specialties including ophthalmology, general surgery, neurosurgery, ENT, dentistry, oral and maxillofacial surgery. Some of the most common procedures where laser ablation is used include tumor and lesion removal. In soft-tissue surgeries, the CO2 laser beam ablates and cauterizes simultaneously, making it the most practical and most common soft-tissue laser. Laser ablation can be used on benign and malignant lesions in various organs, which is called laser-induced interstitial thermotherapy. The main applications currently involve the reduction of benign thyroid nodules and destruction of primary and secondary malignant liver lesions. Laser ablation is also used to treat chronic venous insufficiency.
- 15. LASER TUMORTREATMENT IN ORAL AND MAXILLOFACIAL SURGERY Several types of laser are used in oral and maxillofacial surgery. Depending on the range of their wavelength and their concomitant absorption by biological chromophores, e.g., water and hemoglobin, the lasers are used for different clinical aspects. Fig : 1. Squamous cell carcinoma on the floor of the mouth. 2. One day after laser excision of a squamous cell carcinoma on the floor of the mouth. 3. Six month after laser ablation of a squamous cell carcinoma on the floor of the mouth.
- 16. LASER ABLATIONFOR BENIGN THYROID NODULES The benign thyroid nodules are imaged and the probe along with the guide system are inserted at an appropriate location into the patient’s neck. Optical fibers deliver laser energy into the nodules and the removal of benign thyroid nodules is carried out. Absence of scars along the inserted area can be observed. LASER ABLATION FOR BRAIN TUMORS AND EPILEPSY Laser ablation is extensively used for the treatment of bone tumor and epilepsy. A minimally small incision is made on the scalp after the tumor is imaged through the MRI scanning and through the guide system the optical probe is made to reach the site where ablation is needed.
- 17. ADVANTAGES There isless bleeding, swelling, pain, or scarring. Operating time may be shorter. Laser surgery may mean less cutting and damage to healthy tissues (it can be less invasive). For example, with fiber optics, laser light can be directed to parts of the body through very small cuts (incisions) without having to make a large incision. More procedures may be done in outpatient settings. Healing time is often shorter.
- 18. DISADVANTAGES Fewer doctorsand nurses are trained to use lasers. Laser equipment costs a lot of money and is bulky compared with the usual surgical tools used. But advances in technology are slowly helping reduce their cost and size. Strict safety precautions must be followed in the operating room when lasers are used. For example, the entire surgical team and the patient must wear eye protection. The effects of some laser treatments may not last long, so they might need to be repeated. And sometimes the laser cannot remove all of the tumor in one treatment, so treatments may need to be repeated.
- 19. FUTURE ADVANCEMENTS Nanotechnologyalong with laser ablation holds a promise of effectively treating cancer and tumors without damage to the neighboring healthy tissues. Scientists are on their research on to introduce nanorods that consists of cancer killing genes. And after insertion the laser light is targeted only on the area where tumor is present. Researchers at the Institute of Electronic Structure and Laser (IESL) of the Foundation of Research and Technology – Hellas in collaboration with scientists from the Politecnico di Torino and Istituto Superiore Mario Boella (Italy), have created the first fiber Bragg gratings (FBGs) inside optical a bioresorbable optical fiber. The rising acceptance of innovative technologies is a key trend that has come to the fore for medical treatments. Adoption of tumor ablation practices and advancements in corresponding devices show exciting prospects for tumor treatment in the future.
- 20. CONCLUSION Laser ablationis a promising treatment that presents several advantages with respect to other thermal therapies, however, its effectiveness is strictly dependent on the probe radiation pattern with respect to the tumor shape and on the induced temperature increase distribution that, in turn, to be measured in real- time requires specific sensors not influenced by the laser radiation. The progress in targeting nanoparticles to tumor cells as well as the possibility to specifically tune the laser to the surface plasmon resonance frequency of the nanoparticles are paving the way for the advent of targeted heating. For the promise of this technology to be realized, new solutions, such as HTP tools, thermometry, and the advancement of nanotechnology in medicine, have to be further improved and translated for clinical use.
- 21. REFERENCES K. F.Chu and D. E. Dupuy, “Thermal ablation of tumours: Biological mechanisms and advances in therapy,” Nature Rev. Cancer, vol. 14, pp. 199–208, 2014. T. J. Vogl, V. Freier, N. E. Nour-Eldin, K. Eichler, S. Zangos, and N. N. Naguib, “Magnetic resonance-guided laser-induced interstitial thermotherapy of breast cancer liver metastases and other noncolorectal cancer liver metastases: An analysis of prognostic factors for long-term survival and progression-free survival,” Investigative Radiol., vol. 48, pp. 406–412, 2013. P. Tombesi, F. Di Vece, and S. Sartori, “Laser ablation for hepatic metastases from neuroendocrine tumors,” Amer. J. Roentgenology, vol. 204, 2015, Art. no. W732. W. Chen et al., “Performance assessment of FBG temperature sensors for laser ablation of tumors,” in Proc. IEEE Int. Symp. Med. Meas. Appl., 2015, pp. 324–328. D. Tosi, E. G. Macchi, and A. Cigada, “Fiber-optic temperature and pressure sensors applied to radiofrequency thermal ablation in liver phantom: Methodology and experimental measurements,” J. Sensors, vol. 2015, 2015, Art. no. 909012.
- 22.