The document discusses laser ablation as a thermal therapy technique for tumor treatment, highlighting its mechanisms, applications, and the importance of temperature monitoring during procedures. It covers the use of fiber optic technology and Fiber Bragg Grating (FBG) sensors for real-time temperature measurement, emphasizing its advantages such as less invasiveness and reduced recovery time, along with challenges like equipment costs and the need for specialized training. Future advancements in nanotechnology and integrating innovative approaches hold promise for enhancing the efficacy of laser ablation treatments.

2. CONTENTS
 INTRODUCTION
 LITERATURE REVIEW
 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 is the 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 uses optical 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
 Laser interstitial 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 of the 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
 Ablation literally 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 LASER ABLATION 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 TEMPERATURE MONITORING
 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 THE LASER ABLATION SYSTEM WITH INTEGRATED
TEPERATURE MEASUREMENT CAPABILITY

11. DUAL CLAD FIBER OPTIC 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 ablation is 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 TUMOR TREATMENT 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 ABLATION FOR 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 is less 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 doctors and 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
 Nanotechnology along 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 ablation is 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.

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