EXPERIMENTAL STUDY OF HEATING EFFECTS OF 27.12 MHz DIATHERMY UNIT ON CLAY MODELS FOR HYPERTHERMIA APPLICATIONS IN CANCER TREATMENT
Beena Roshini John William B.E., Anna University, India, 2005
PROJECT
Submitted in partial satisfaction of the requirements for the degree of
MASTER OF SCIENCE
in
ELECTRICAL AND ELECTRONIC ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
SUMMER 2009 EXPERIMENTAL STUDY OF HEATING EFFECTS OF 27.12 MHz DIATHERMY UNIT ON CLAY MODELS FOR HYPERTHERMIA APPLICATIONS IN CANCER TREATMENT
A Project
by
Beena Roshini John William
Approved by:
, Committee Chair Preetharn B. Kumar, Ph.D
, Committee Chair Russ Tatro ,MS EE
a g/11/h
Date
ii Student: Beena Roshini John William
I certify that the student have met the requirements for format contained in the University format manual, and that this Project is suitable for shelving in the Library and credit is to be awarded to this Project.
Dr. Preetham B. Kumar, Ph.D., Graduate Coordinator Date Department of Electrical and Electronic Engineering
iii I
Abstract
of
EXPERIMENTAL STUDY OF HEATING EFFECTS OF 27.12 MHz DIATHERMY UNIT ON CLAY MODELS FOR HYPERTHERMIA APPLICATIONS IN CANCER TREATMENT by
Beena Roshini John William
This project will focus on the experimental characterization of heating effects by 27.12 MHz Mettler Diathermy system on clay models for use in hyperthermia for cancer treatment. The project involves microwave applicators suitable for hyperthermia treatment of advanced cancer colli uteri in combination with ionizing radiation. The Mettler diathermy system is used to record the heating patterns in the dielectric lossy media. The eventual application of this study is to have variations in the diathermy unit using dielectric lossy materials which are very close to the biological tissue and observe its relation to the temperature rise in the dielectric media that is used.
This project mainly concentrates on the focusing ability of the diathermy system to target the tumor area with minimal effect to the healthy tissues. The clay models were used in this project to study the effect of radiation. The experiment was done for hardening and non hardening clay and the temperature was noted. The maximum temperature we achieved was with non hardening clay when the area was heated to 82.630 F
, Committee Chair Dr. Preetham B. Kumar, Ph.D.
iv ACKNOWLEDGEMENT
I would like to thank Dr. Preetham Kumar, Faculty Member, EEE department for his guidance, giving me the opportunity to take on this project and steering me in the right
direction. A special thanks for his support, and constructive feedback throughout the
course of fieldwork.
I would also like to acknowledge and thank Professor Russ Tatro, Faculty Member, EEE
department for being part of the review committee to help me finalize the project and
strengthen the foundation I designed the project on.
V TABLE OF CONTENTS PAGE
Acknowledgement...... iv List of Tables ...... vii List of Figures ...... viii
Chapter 1. INTRODUCTION...... 1 2. BACKGROUND RESEARCH ON MICROWAVE HYPERTHERMIA IN TREATMENT OF CANCER ...... 3
2.1 Types of hyperthermia ...... 3
2.1.1 Local Hyperthermia ...... 3
2.1.2 Regional Hyperthermia ...... 7
2.1.3 Whole Body Hyperthermia ...... 8
2.2 Applications and Benefits of Hyperthermia ...... 10
2.3 Risks of Hyperthermia ...... 12
2.4 Hyperthermia and Radiation ...... 14
3. DIELECTRIC MATERIAL AND DIATHERMY ...... 16
3.1 Dielectric Properties ...... 16
3.2 Dielectric Permittivity Spectrum ...... 17
3.3 Diathermy ...... 19
3.3.1 Dielectric Diathermy ...... 20
3.3.2 Inductive Diathermy ...... 20
3.4 Types of Diathermy ...... 21
vi 3.4.1 Short wave diathermy (SWD) ...... 21
3.4.1 (a) Features of Diathermy devices ...... 22
3.4.2 Microwave Diathermy ...... 25
3.4.2(a) Microwave absorption in the tissues ...... 26
3.5 Effect of hyperthermia in Tumor treatment and blood flow ...... 28
4. METTLER AUTOTHERM EQUIPMENT DESCRIPTION ...... 31
4.1 Mettler Autotherm equipment details ...... 32
4.2 Mettler in heat therapy...... 33
4.3 Advantages of Mettler Shortwave diathermy unit ...... 35
4.4 Safety Precautions while using Autotherm ...... 36
5. EXPERIMENTAL RESULTS WITH AUTOTHERM UNIT ...... 37
5.1 Measurements with the hardening clay medium ...... 37
5.1.1 Measurement with applicator on top of clay ...... 38
5.2 Measurements with clay using Reflector ...... 42
5.3 Measurements with the non hardening clay ...... 46
6. CONCLUSION...... 49
References ...... 51
Vii LIST OF TABLES
Table 3.1 Penetration depths of tissues with high and low water content ...... 26
Table 5. 1 Heating results with hardening clay medium (Applicator on top of the clay) ...... 38
Table 5. 2 Heating results with hardening clay medium (Applicator at D=1.5" top of the clay) ...... 40
Table 5. 3 Heating results with hardening clay medium (Applicator at D=2.5" top of the clay) ...... 41
Table 5. 4 Heating results with clay medium and reflector (Applicator on top of the clay)...... 43
Table 5. 5 Heating results with clay medium and reflector (Applicator at D=1.5" top of the clay) ...... 44
Table 5. 6 Heating results with clay medium and reflector (Applicator at D=2.5" top of the clay) ...... 45
Table 5. 7 Heating results with non hardening clay medium (Applicator on top of the clay)...... 46
Table 5. 8 Heating results with non hardening clay medium (Applicator at D= .5" top of the clay) ...... 46
Table 5. 9 Heating results with non hardening clay medium (Applicator at D=2.5" top of the clay) ...... 47
viii LIST OF FIGURES
Figure 2. 1 Scheme of a system for local hyperthermia ...... 4
Figure 2.2 Applicator types for local hyperthermia, such as (a) waveguide applicator; (b) spiral applicator; and (c) current sheet applicator ...... 5
Figure 2.3 Sigma-60 applicator (four dipole pairs) with treatment couch of BSD-2000 system for regional hyperthermia ...... 8
Figure 2.4 Schematic drawing of the Aquatherm system for whole-body hyperthermia .10
Figure 2.5 Density Measurements from stained tissues ...... 15
Figure 3. 1 Frequency response of dielectric mechanism ...... 18
Figure 3.2 Range of intensities of stray magnetic fields around the diathermy ...... 23
Figure 3.3 Range of intensities of stray electric fields around the diathermy cables ...... 24
Figure 3.4 Rate of microwave radiation depth in tissues ...... 27
Figure 4. 1 Mettler Autotherm Diathermy Unit ...... 31
Figure 4.2 Control Knobs on Mettler Diathermy Unit ...... 32
Figure 4.3 Patient Input Meter of Mettler Unit ...... 33
Figure 4.4 Relative absorption of RF power generated by the Autotherm equipment ... 34
Measurements with Hardening clay
Figure 5. 1 Graphical representation of Temperature distribution Vs Time (Applicator on top of the clay)...... 39
Figure 5. 2 Thermometer inside clay at a depth D=1.5 inches ...... 39
Figure 5. 3 Graphical representation of Temperature distribution Vs Time (Applicator at D=1.5" top of the clay) ...... 40
Figure 5.4 Thermometer inside clay at a depth D=2.5 inches ...... 41
ix Figure 5. 5 Graphical representation of Temperature distribution Vs Time (Applicator at D=2.5" top of the clay) ...... 42
Measurements with hardening clay and reflector
Figure 5. 6 Graphical representation of Temperature distribution Vs Time (Applicator on top of the clay)...... 43
Figure 5. 7 Graphical representation of Temperature distribution Vs Time (Applicator at D=1.5" top of the clay) ...... 44
Figure 5. 8 Graphical representation of Temperature distribution Vs Time (Applicator at D=2.5" top of the clay) ...... 45
Figure 5. 9 Comparison graph for the clay models temperature distribution Vs Time .... 47
x I
Chapter 1
INTRODUCTION
One of the leading causes of disease-related death in developed nations is cancer.
Even after thirty five+ years of research, the survival rate is still 50/50 as it was back in the 1970s [4].
Simply put, cancer is any malignant growth or tumor caused by uncontrolled cell division. Treatment varies from radiation to chemotherapy or surgery and in some cases even a combination of these. The prognosis and intensity of treatment depends on the type of cancer, how early it was diagnosed and presence of the malignancy in a person's body. Microwave hyperthermia, or heat treatment, is considered the fourth modality to treat cancer [1-8] the other three being surgery, chemotherapy and radiation.
Hyperthermia is used along with chemotherapy or radiation and has been found to significantly enhance the treatment efficacy of chemotherapy or radiation.
The principal here is to destroy cancerous cells by heating them to a 'healing-fever' temperature. For this we use a microwave hyperthermia system which consists of a transmitting antenna applicator. This mechanism delivers a microwave beam into the tumor volume, and maintains the temperature at 42° C. 2
For my project, I have focused on the development of a microwave hyperthermia system at 27.12 MHz. The treatment of tumors in the human body was simulated using clay models. Clay was chosen as it closely mimics the properties of human tissue or skin.
Two types of clay were used to compare the effectiveness of the study:
- Hardening clay with very less moisture content
- Non-hardening clay with high moisture content
We will be analyzing different properties of clay to study the effect of radiation on them.
Temperatures were monitored using precision thermometers so that measurements could be taken without harming the normal tissue or damaging the structure of the cancerous cells.
The first section of this report is an introduction to cancer and the treatments used.
Section two delves into research on hyperthermia for the treatment of cancer. We will also be discussing the benefits and applications of microwave hypothermia.
Section three explains the dielectric properties and the types of diathermy.
Section four looks at the Mettler Diathermy equipment details.
Section five is the experimental results that were obtained using the Autotherm unit. 3
Chapter 2
BACKGROUND RESEARCH ON MICROWAVE HYPERTHERMIA IN TREATMENT OF CANCER
Hyperthermia is a thermal therapy used for cancer in humans. The cancer cells are treated
under high temperatures which damages the proteins and structures within the cells.
Hyperthermia is an adjunctive therapy along with some cancer treatments like
radiotherapy and chemotherapy.
2.1 Types of hyperthermia
There are different kinds of hyperthermia that are under study
1. Local Hyperthermia
2. Regional Hyperthermia
3. Whole Body Hyperthermia
2.1.1 Local Hyperthermia
Local hyperthermia is a simple procedure of heating the cells affected with cancer using a heating element such as microwave, heating rods, antennas, ultra sound at
very high temperatures (up to 106 0 F). In this treatment the heat is applied to a small area
only. By applying high temperatures the cancerous cells are destroyed. Two factors play
a major role in this treatment. The temperature of the cell and the volume of area the 4
temperature is exposed to. The temperature used in local hyperthermia is 1060 F for a
period of 60 min [5].
Different types of applicators are used to treat local hyperthermia, namely waveguide, horn, spiral, current sheet and compact applicators. The Figure 2.1 shows the components
used in the hyperthermia system.
Figure 2. 1 Scheme of a system for local hyperthermia[3]
The electromagnetic coupling between the tissue and the applicator is done by a water
bolus. The temperature can be controlled in two ways, by positioning the applicator
or using a power generator. The types of applicators used are shown in Figure 2.2. 5
II 1 L-rl.J
A B
Figure 2.2 Applicator types for local hyperthermia, such as (a) waveguide applicator; (b)
spiral applicator; and (c) current sheet applicator [3]
The electromagnetic applicators have an emitting diameter of 15 cm at a frequency of
150-430 MHz and therapeutic depths below 3cm [5].
Depending on the tumor locations the local hyperthermia is further divided into
* External
* intraluminal or endocavitary
* Interstitial
* Radiofrequency ablation 6
External hyperthermia is mainly used to treat breast cancer and tumors that are on or below the skin. Heat is applied to the tumor externally using applicators which generates high frequency energy waves like microwave or ultrasound [11] [3].
Intraluminal or endocavitary and Interstitial hyperthermia is used to treat cancers near or within body cavities (oesophagus or rectum). In this treatment the cancerous area
is heated using a sterile probe which is then placed inside the cavity where the tumor is.
Interstitial hyperthermia used to treat tumors that are deep inside the body. It is
similar to intraluminal in which a probe or wire is placed within the tumor and heated
under higher temperatures than external hyperthermia. In this treatment the person is kept
under anesthesia. Both these techniques are suitable for tumors that are less than 5cm in
diameter. There are various antenna types that are available, microwave antennas,
ultrasound transducers, radio frequency electrodes, laser fibers and heat sources.
Endocavitary antennas are inserted in natural opening like cervix, oesophagus etc. The
antennas have dimensions in the range of centimeters [2].
Radiofrequency ablation (RFA) uses high-energy radio waves for treatment. This
is the most widely used local hyperthermia. A needle probe is placed into the tumor for
10 to 15 min which releases high frequency current that creates heat above 1220 F and
destroys the cancer cells within a certain area. Tumors in liver are treated with RFA.
This treatment can be repeated for tumor recurrence, regrowth, or incomplete treatments
[4]. 7
2.1.2 Regional Hyperthermia
Regional Hyperthermia is used for a particular body organ such as legs, hands so they are popularly used for treatment of cancers such as sarcomas and melanomas. There are various approaches that are followed in regional hyperthermia, deep tissue, regional perfusion and Continuous Hyperthermic Peritonial Perfusion (CHPP). In Regional perfusion the blood supply goes to just a region of the body and the rest of the body is
isolated. The blood in that isolated part is pumped into a heating device and pumped back
into the area using pump oxygenator to heat it. Continuous hyperthermic Peritonial
Perfusion (CHPP) is one form of regional hyperthermia which is used to treat abdominal cavity (intestines and other digestive organs) with a temperature of 1080 F.
The drugs are injected into the cancerous cavity during treatment. And deep tissue hyperthermia is used for patients suffering from advanced tumors or recurrent tumors of the pelvis, cervical and bladder cancer. The tumors are treated with devices that can produce high energy waves directed to specific areas [4].
Regional hyperthermia uses the Sigma-60 applicator which is shown in the Figure 2.3 below. It consists of four dipole antenna pairs which form a ring around the patient.
These antenna pairs can be controlled in phase and amplitude. Dipole antennas are schematically shown (b) A novel multiantenna applicator Sigma-Eye (12 dipole pairs) mounted on the same treatment unit as shown in (a). The elliptical form is more comfortable for the patient 8
Figure 2.3 Sigma-60 applicator (four dipole pairs) with treatment couch of BSD-2000
system for regional hyperthermia [3]
The power distribution can be improved by increasing the antenna number and by adjusting its phase and amplitude.
2.1.3 Whole Body Hyperthermia
This is a very serious form of treatment given to people who have cancer spread throughout the body (metastatic cancer). Here also the treatment temperature is 108 0 F which is delivered by using thermal blankets or water baths [5]. It is always recommended to use temperatures below 1 10 F otherwise the normal tissues may also be affected. The major advantage of using heat as a source for treatment of cancer is that the 9 cancer cells are very sensitive to heat and are damaged when exposed to high temperatures [5].
Hyperthermia is one of the popularly used methods for the treatment of cancer yet it is very difficult to target the cancer cells. Some of the side effects of hyperthermia is that the normal cells also get affected. One source puts it thus: "It can be hypothesized that hypoxic cells in the center of a tumor are relatively radio resistant but thermo sensitive, whereas well-vascularized peripheral portions of the tumor are more sensitive to irradiation. This supports the use of combined radiation and heat; hyperthermia is especially effective against centrally located hypoxic cells, and irradiation eliminates the tumor cells in the periphery of the tumor, where heat would be less effective"[5].
The Aquatherm system is used for the whole body hyperthermia. It is an isolated moisture-saturated chamber. On the inner sides it has the water-steamed tubes (122 to
140 0 F) in which the patient is positioned. Long-wavelength infrared waves are emitted.
The cabin where the patient is positioned is a moisture saturated cabin with hot water tubes (600 C) inside. After a systemic temperature of 41.80 C has been achieved, the patient is thermally isolated with blankets. 10
Figure 2.4 Schematic drawing of the Aquatherm system for whole-body hyperthermia [3]
2.2 Applications and Benefits of Hyperthermia
Hyperthermia is used with radiation therapy to enhance the treatment of tumors; it is also used along with chemotherapy in which they use certain types of drugs to destroy cancer cells.
There are vast applications of the Hyperthermia in medical field. This is used as treatment for many diseases. Hyperthermia raises the temperature of the body above normal of 98.6 0 F in order to reduce the foreign organisms and sweat impurities in the system. Further it is observed that when compared to the body tissues, the invading foreign organisms cannot withstand if the temperature levels are increased beyond a certain point. So taking this as an advantage, the body temperature can be increased to certain level to kill the unwanted organisms, bacteria and virus, and also used vastly in treating cancer cells. The heat produced by hyperthermia helps in drawing out toxins, cleans clogged pores, kills harmful bacteria and viruses, increases circulation and II enhances the immune system. It is also used to heal the muscle aches, pains and injuries caused during accidents [ 14].
Hyperthermia is used in the treatment of upper and lower respiratory tract infections, bladder problems, urinary tract infections such as cystitis, bronchitis, pneumonia, sinusitis and other conditions of the lungs and body cavities, and also used as a modality for physical therapy. One of the main advantages of hyperthermia is that it is used to help the other forms of cancer treatment to work better. It is observed that the radiations and chemotherapy drugs will be effective if the temperature of the cancer cells are increased using the hyperthermia. Sometimes the temperature increase also destroys the tumors without surgery [4]. The viral diseases can be cured by hyperthermia. With controlled raise in temperature and heart rate, it can be used to treat several diseases ranging from upper respiratory infections to sexually transmitted diseases like AIDS. Due to overheating, the invading foreign organisms die before the heat harms the human tissues. The examples for these organisms are viruses such as rhinovirus which are responsible for one half of all respiratory infections, HIV (Human Immunodeficiency
Virus), and the microorganisms and bacteria that causes syphilis and gonorrhea [14] [4].
Hot baths are also helpful in the treatment of herpes simplex, herpes zoster
(shingles), and also the common cold and flu, as well as chronic fatigue syndrome.
Initially the treatment causes the situation to aggravate but later the condition starts to improve after a short time. Some laboratory researchers have proven that HIV is temperature sensitive and it can be inactivated with a gradual increase in temperature of the human body over its normal temperature of 98.6 0 F. Microwaves are also used to 12 induce the local hyperthermia by exposing the biological tissues to microwave radiations.
This induces the electric and magnetic fields with in the tissue and gives rise to ionic currents and molecular excitations that heat adjacent tissues [14].
Hyperthermia combined with radiation is effective in damaging the acidic and poorly oxygenated parts of the tumor and also damages the cells that are ready to divide.
Since it is difficult to achieve the same temperature through out the body, the whole body hyperthermia is not usually combined with radiation, where as it is more useful with chemotherapy and immunotherapy [1]. The mild hyperthermia which equals the temperature of a naturally high fever helps in naturally stimulating the immunological attacks against the tumor. Additionally, the moderate hyperthermia which can be achieved at a temperature of about 104-107 0 F is effective in damaging the tumor cells by making them more radiosensitive and also increasing the pore size so that large- molecule chemotherapeutic and immunotherapeutic agents like monoclonal antibodies and liposome-encapsulated drugs.
2.3 Risks of Hyperthermia
Hyperthermia is considered to be one of the safest and effective treatments for many conditions; however there are some side effects of hyperthermia [12]. These side effects are noticeable only if the temperature is raised above 106 0 F and usually are not recommended for people who have anemia, heart disease, diabetes, seizure disorders, tuberculosis, and women who are or may be pregnant. Sometimes the products such as 13
blood products, vaccines, pollens and benign forms of malaria which are used to induce
hyperthermia are not recommended [ 12].
The internal body temperature above 104 0 F compared to 98 0 F is always
harmful to the human life. If the temperature is raised to 106 0 F then brain starts loosing
its control and might die. Further if the temperature is above 113 0 F then muscles starts
to get rigid and might also lead to sudden death. Hence hyperthermia should be
implemented carefully and precisely as it can be life threatening like the other diseases
[16].
There are several other risks associated with hyperthermia. These include pain and
external burns. The high temperature can cause minor discomfort to significant pain,
blistering and actual burning of the skin. Some studies have suggested that for pregnant women, hyperthermia involves high risks in the form of birth defects called neural tube
defects in the babies. Further hyperthermia can cause miscarriage, high fever and heart
defects and abdominal wall defects for the new born infants. The risks involved with
whole body hyperthermia are more which includes cardiac and vascular disorders, diarrhea, nausea and vomiting. Extracorporeal systemic hyperthermia can cause frequent
persistent neurophites, abnormal blood coagulation, damages to liver and kidneys, and
brain hemorrhaging and seizures [ 16] [2] 14
2.4 Hyperthermia and Radiation
Hyperthermia along with radiation is proved to be very effective. Studies [8] reveal that when hyperthermia and radiation therapy treatments were combined the results were effective and better, the response rate for radiation alone was 35% and the response rate of hyperthermia and radiation was 75% [8]".
In Hyperthermia treatment the cancer cells are heated to several degrees above the body temperature and the cancer cells are killed, whereas in radiation therapy, high energy X rays are used to kill the tumor cells. The objective of combining hyperthermia and radiation is to kill the largest number of cancer cells possible. The patients are kept under external beam of radiation for several weeks. Hyperthermia treatment is given in the early course of radiation and only once a week. An ultra sound applicator is used to deliver the hyperthermia treatment.
One another important reason to combine hyperthermia and radiation is of the poorly oxygenated tumors. Many tumors are hypoxic and hence they are more resistant to radiation. Hence studies proved that hyperthermia along with megavoltage radiation may solve the oxygen problem. The figure below shows the number of tumor cell decrease when both the therapies are combined 15
* Tumor periphery 0 400 I S Tumor core 0Z 0 350 a 1o 300 r .2.0 250 .0 r .0 20D E C 150 CD 2 ISO .0 100
< 50
0 I I Control Hyp Rad Hyp+Rad
Figure 2.5 Density Measurements from stained tissues [10]
Another important effect is the thermo sensitization, it is observed when cells are overly hearted and irradiated under acid pH conditions [22]. The radio sensitization effect is quantified using the thermal enhancement ratio (TER).
TER = Radiation dose alone / radiation dose with tumor
It is defined as the ratio between minimal dose of radiation which is required to induce a biological effect and the dose required when radiotherapy and hyperthermia are combined [23]. 16
Chapter 3
DIELECTRIC MATERIAL AND DIATHERMY
3.1 Dielectric Properties
The scientists and engineers have been benefited by the discovery and the properties of the dielectric materials. As every dielectric has its own property and its own design.
These properties have helped them in getting valuable information which could help improve the quality of-an application or to design a manufacturing process. As the materials carry their own losses and own properties of frequency, different applications could emerge in various processing techniques such as industrial microwave processing for rubber, plastic and ceramic.
My main focus here is to get the dielectric properties of the human tissues so that it would help in getting the dielectric property of the human model pertaining to relative permeability and electrical conductivity of the system at the frequency of interest. Getting advanced data about the dielectric properties helps in calculating the absorption rate of the tissues and organs with respect to the electromagnetic waves and to get their respective current densities. The property that consists of the relative permittivity and the conductivity helps to find the wavelength and the penetration of the skin depth [ 17]. 17
The dielectric of the material is related to the capacitance as it denotes the dielectric between two parallel plates and its ability to store the energy. The dielectric is usually used to fill up the field instead of an insulator. If we take metal in place of a dielectric which is completely a conductor of electricity then the dielectric constant of that field would be zero. And the ability of the dielectric is how long it stores the charge and what kind of material it is.
3.2 Dielectric Permittivity Spectrum
The Dielectric permittivity spectrum has a wide range of frequencies. The response of the normal materials like vacuum, air, paper etc to the external fields depends mostly on the frequency of the field. Hence the polarization of the material does not respond to the applied field because of the frequency dependence. For this reason, the permittivity is treated as a complex function in this case. These dielectric properties are measured with dielectric spectroscopy. The Figure 3.1 below shows the frequency response of the dielectric mechanisms 18
Dipolar
12 15 10 MW IR V UV
Figure 3.1 Frequency response of dielectric mechanism [ 17]
There are different kinds of dielectric mechanisms; they are different from each other in the way the medium reacts to the applied field. The dielectric mechanism is divided into two main categories: relaxation and resonance processes. They have their own characteristic frequency, which is a reciprocal of time. The main categories are
* Electronic polarization
* Atomic polarization
* Dipole relaxation
* Ionic relaxation
* Dielectric relaxation 19
These are arranged according to the highest frequencies in order. Each dielectric mechanism has a characteristic "cutoff frequency." At high frequencies the contribution mostly comes from electronic polarization, so only free electrons can respond to electric field. This explains why metals are good optical reflectors [17].
3.3 Diathermy
Diathermy is a process to generate heat in the body tissues; the electric current is used
to transmit heat to the surfaces which increases the flow in the circulation of blood by using electrodes to transfer current. As the used frequency is high, proper care must be
taken to prevent healthy tissues from getting damaged. Diathermy is a controlled production of deep heating beneath the skin. Microwave diathermy and Radio or high
frequency waves are the two types of the diathermy devices. The Radio frequency
devices are operated at a frequency of 27.12 MHz and the microwave diathermy operates
at a frequency of 915 MHz and 2450 MHz. The microwave diathermy is used for
treatment up to wavelength of 12.25 cm and around the frequency of 2450 Hz. These waves are obtained by aerials or electrodes by a heating valve called magnetron [ 18].
Diathermy involves the heating of deep muscular tissues. When the heat is applied to the area, the metabolism of the area increases and the increase in the circulation of blood accelerates the repair of the tissues, the heat helps in the relaxation of the tissues by 20 reducing nerve fiber sensitivity and increasing the pain threshold. Diathermy has been classified into two different methods depending on the way they are applied
* Dielectric Diathermy
* Inductive Diathermy
3.3.1 Dielectric Diathermy
In dielectric diathermy, there is always a rapidly alternating voltage differential that is created between the two electrodes, thereby producing an alternating field between the electrodes. When two electrodes are placed either one on each side or both on the same side on the treatment surface of the body, an electric field penetrates into the tissues of the area of the body. The electric charges that are produced in the tissue molecules will align themselves with the rapidly changing electric field. So when the molecules move around, there is some alteration of the molecules thereby causing a friction and collision with the other molecules. This produces some amount of heat in the tissues. The electric field strength is determined by the difference in potential between the electrodes set by the unit power control. The electrodes are metal plates mounted in cushion enclosures.
3.3.2 Inductive Diathermy
Unlike the dielectric diathermy, Inductive diathermy produces a reversing magnetic field.
In inductive coupled radio frequency diathermy, the high frequency current is generated through a coil, which produces the reversing magnetic field. The applicator has the coil 21 wound inside of it. The applicator is normally attached to the diathermy unit by an adjustable arm. It is positioned directly over or next to the area to be treated. The rapidly reversing magnetic field induces circulating currents and electric fields into the body tissues which help in producing heat in the tissues. The intensity of heating is determined by the average output power [ 19].
3.4 Types of Diathermy
3.4.1 Short wave diathermy (SWD)
Short wave Diathermy is a therapeutic elevation of temperature in the tissue by means of
oscillating electric current. Deep heat is applied to the body and the tissues. When the body is subjected to high intensity energy it will cause heating. The two parameters that
are involved in Short wave diathermy is frequency at 27.12 MHz and wavelength of
11.06 m. The two types of shortwave diathermy is
1. Continuous mode
2. Pulsed mode
In the continuous mode there is always a constant output. Hence the machine achieves heating of deeper modalities. It would be a consideration for the desired effect of a thermal response on the tissue that is to be treated. Studies reveal that it decreases
stiffness, increases tissue extensibility, improves blood flow to certain area and also decreases pain [9]. 22
Pulsed mode allows cooling between the pulses; it enhances the non-thermal effect of the radiofrequency energy. It facilitates tissue healing, decrease in inflammation and decrease in pain.
Therapeutic effects include
* Reduces pain and inflammation
* Increases the blood flow
* Reduces muscle spasm
* Increases enzymatic activities
* Increases metabolism
* Increases elasticity of connective tissue [9]
3.4.1(a) Features of Diathermy devices
A diathermy device consists of an electrode which is also known as an applicator, RF generator, and control console. The applicator applies RF energy to a certain portion of a patient's body that needs to be treated. Proper tuning and application is required. RF power is delivered from the generator to the applicator. The tissue temperature should be elevated to a range of 40-45° C such that it does not harm the patient. Continuous supervision and observation of the patient are required. The treatment time is usually 20-
30 minutes.
The applicator is usually of two types capacitor type and inductor type. In capacitive electrode, tissue heating is due to the RF electric field and in inductive 23 electrodes; heating is due to the eddy currents induced in tissue by the magnetic field.
There is some high intensity field around the cables. The radiation field close to the SWD applicator is of near field type. The Figure 3.2 and Figure 3.3 below show the range of intensities of electric and magnetic fields around the diathermy cables. The shaded area shows the magnetic field intensities around the cables of a shortwave diathermy device for various types of electrode and power settings [13].
4-.4
:t. AIM -O10mWICrO)
O"44.42 .I, .O.21' O.kA,'m (I 2),
OJ L. 2.'J __. 10 ' 0 :Din25 ke0 X35 e DIST*4 CE(mi
Figure 3.2 Range of intensities of stray magnetic fields around the diathermy [13]
The Figure 3.3 below shows the range of electric field intensities around cables of a short wave diathermy device for various types of electrodes and typical power settings 24
The intensities of the fields depend on various factors like electrode type and design, the power setting, the part of the patient and also the position placement of the electrode on
the area being treated. The intensity decreases with distance away from the electrodes
10000, 6000-
So.i,60bo-e
r .2 OSM0OSAPE.cm
100 -r 10t. :15 '20, C23 30 3! DISTAPICE.60n
Figure 3.3 Range of intensities of stray electric fields around the diathermy cables [13]
Shortwave diathermy has the following precautions or contraindications [20]
* Malignancy
* Sensory loss
* Metallic implants or foreign bodies
. Pregnancy
* Application over moist dressings
* Ischemic areas or arteriosclerosis 25
* Thromboangiitis obliterans
* Phlebitis
* Use extreme care with pediatric and geriatric patients
* Cardiac pacemakers
* Contact lenses
* Metal-containing intrauterine contraceptive devices
* Metal in contact with skin (e.g., watches, belt buckles, jewelry)
* Use over epiphyseal areas of developing bones
* Active menses
3.4.2 Microwave Diathermy
Microwave radiation is also used to heat tissue that is deep inside the body. Microwave
radiation is defined with the frequency 300 MHz - 300 GHz, which lies between radio
frequency and infrared radiation. It is used for superficial tumors with conventional
radiotherapy and chemotherapy. After a lot of research, studies reveal that 434 and 915
MHz microwave diathermy frequencies are the most effective. When Microwave
diathermy technique is induced in the tissue it can stimulate repair processes, increases
drug activities, relief from pain and removes toxic wastes. It also helps to reduce muscle and joint stiffness. 26
Microwave diathermy units operate at a frequency higher than shortwave
diathermy. Most microwave diathermy units usually operate at a frequency of 2.45 GHz
and reach a therapeutic value at 1.85 cm with skin temperature above 45 0 C. In addition
to the frequency of the wave the primary importance is the effectiveness of the device
and the variables that are considered when administering microwaves, time and power.
The table shows the average penetration depth of tissues with high and low water content
Frequency (MHz) Penetration depth (cn)
High water content tissues Low water content tissues
434 3.57 26.2 915 3.04 17.7 2450 1.70 11.1
Table 3.1 Penetration depths of tissues with high and low water content [3]
Since the water has high dielectric constant, the tissue with the high water content absorbs more energy. The higher the dielectric constant, the deeper will be the
penetration.
3.4.2(a) Microwave absorption in the tissues
The microwave absorption works on Grotthus Law which states that "When any radiation
meets the surface of a different medium it may either be reflected or penetrate. Those
radiations that do penetrate will only have an effect if they are absorbed; thus they will be
ineffective if they pass right through". 27
There is a considerable reflection at the air-skin boundary in the tissues; hence the percentage of radiation (at 2450 MHz) reflected varies according to the fat and skin thickness. It varies in the range from 50% to 75%. At all other frequencies in therapeutic use 60% to 70% of energy is reflected. The figure below shows the rate of heating in fat, muscle and bone with different depths in tissues at 2450 MHz.
Fat Muscle Bone 100 ,ii n
50
0 1 2 3 4 5 6
Figure 3.2 Rate of microwave radiation depth in tissues
The pattern above shows that the absorption of microwaves is less in Fat and absorption is higher in vascular muscle tissue and no absorption or very little absorption of microwaves in bone. The Microwave radiation penetrates into the tissue and subjects to refraction. The wave velocity decreases from air to skin and fat and then goes to the muscle. The heating of the tissues depends on two factors, microwave absorption and rate of transfer within and between the tissues. The major use of microwave therapy is for 28
heating muscle tissue to achieve an increase in intramuscular blood flow. It is effective for lesions in the superficial tissues, hence used in the treatment of traumatic and
rheumatic conditions affecting the tissues [20].
Contraindications of microwave diathermy
* Defective thermal sensation
* Defective arterial circulation
* Acute inflammation
* Recent hemorrhage
* Malignancy
* Implanted cardiac pacemakers
* Intrauterine devices when using a vaginal electrode
* Eyes and testes, due to poor heat dissipation
* Pregnant uterus
3.5 Effect of hyperthermia in Tumor treatment and blood flow
The main aim of hyperthermia is to destroy the tumor and cancer cells by heating them
beyond the cytotoxic threshold which is around 108.50 F. Sometimes hyperthermia alone
can be used to cure the cancer cells. But most of the times they are combined with other
type of anti-cancer methods like chemotherapy and radiotherapy. These combinations
will be more effective in killing the tumor and the cancer cells [22].
One of the main reasons to use hyperthermia in tumor treatment is that the tumor
tissues react more sensitively to the heat compared to the surrounding normal tissues. 29
There are several abnormalities in the functionality and vessel structure of the tissues.
Hence with the raise in temperature, the abnormalities increases and unable to react physiologically. With the increase in temperature the blood perfusion process decreases.
Due to this the blood flow decreases below the conditions of normothermia. As the tumor cannot dissipate the heat the body temperature rises above 104 0 F. The severity of the structural damage in the tissues will be very high compared to the normal tissues. The transportation of the metabolic product decreases with high temperature. The PH level inside the tumor cells decreases which is boon for hyperthermia implementation. With the decrease in microcirculation, the nutrients content in the tumor decrease. Further the protein contents decreases. These proteins play an important role in the structure of cells and the raise in temperature affects the basic structural design of the tissues [22].
There are a lot of variations of the blood flow inside the tumors. Even if it is a single tumor, there are different regions which make the blood flow uneven. With the increase in size of the tumors, the blood flow decreases. Hence the blood flow inside the tumor is less compared to the neighboring tissues. But it is found during the normothermic conditions, the blood flow in the small tumors will be more than the other tissues. Further it is found the tumor blood flow won't increase upon heating compared to the other tissues. Hence upon heating, the normal tissues dissipates lot of heat where as the tumors absorbs more heat and their temperature increases.
With increase in temperature of the tumors, the vascular tissues in the tumor get damaged. Due to this, the tumor gets acidic, hypoxic and deprived of nutrients. Due to the acidic conditions and other suitable environments, the chemotherapic drugs and 30 radiations are more effective on these tumors. Hence hyperthermia is usually combined with many other anti-tumor therapies like chemotherapy, radiotherapy for treating the cancer cells and tumors.
Hyperthermia damages the plasma membrane, nucleus of the cell and also the cytoskeleton (a cellular skeleton contained within cytoplasm). The cancer cells sometimes become highly resistible for the radiation therapy. These cells start to multiply and outplay the other cells and block the oxygen and nutrients from transporting to the non tumor cells. The radiation therapy requires oxygen for its effectiveness. Since the cancer cells have oxygen deficiency, the effect of radiation therapy will be retarded. The tumors are difficult to be removed during surgery. These tumors if not removed carefully, will leave the cancer cells which again start to multiply. When the temperature increases, the blood flow also increases. Hence hyperthermia is used to increase the tumor blood flow. With the increase in blood flow, the chemotherapy and radio therapy become effective enough to act upon the tumor cells. Hyperthermia also damages the acidic cancer cells which are formed by the poor blood flow. It kills these cells by dismantling and killing the cellular proteins which are essential part of their structure 31
Chapter 4
METTLER AUTOTHERM EQUIPMENT DESCRIPTION
In the project, all the measurements were taken using MettlerCAutotherm equipment. The Autotherm's unique induction field circuitry produces a short wave frequency of 27.12 MHz which can penetrate into muscle tissue with negligible heating in the fatty layer or bone [15]. In this project the Autotherm 300 shortwave diathermy was used shown in the Figure 4.1
4r
Figure 4. 1 Mettler Autotherm Diathermy Unit [21 ] 32
4.1 Mettler Autotherm equipment details
Mettler Autotherm 300 diathermy is capable of automatic tuning which ensures proper frequency response. It is portable with a roller caster base and light weight. The arm is made adjustable, so that it can reach all parts of the body with therapeutic deep heat. This equipment is mainly used where deep heat is required such as lower back, shoulder, hip and neck. This is very economical equipment and the treatment time is approximately 1-30 minutes.
It has two types of control that control all the treatment settings
a. a timer
b. a intensity control knob
Figure 4.2 Control Knobs on Mettler Diathermy Unit
The timer is one of the key elements in the autotherm. The timer switch is designed to be varied from 0 to 30 minutes. If a patient has to be treated for an exact 33 amount of time, this timer helps it to be accurate. There is also a power meter which displays the energy levels which is absorbed by the treatment surface. It monitors the current from the power supply. It indicates the enrgy dose absorbed by the patients. It does not have any units.
Figure 4.3 Patient Input Meter of Mettler Unit
The Equipment along with the cart will weight from 30 pounds. It is convenient, compact, as it is portable to the treatment rooms. A multi-joint arm, with their continuous or pulsed modes this equipment can produce gentle warming effects in applied areas.
4.2 Mettler in heat therapy
When deep heat therapy is required for any part of the body, Mettler autotherm is an effective tool. Mettler operates with short wave diathermy and is a safe heating equipment for subcutaneous body tissues. It generates an electromagnetic field between the equipment and the body such that it penetrates deep into muscle tissue, bringing soothing relief. Hence some sensitive areas of the body, back pain or spasm, bursitis, 34
chronic arthritis and other musculo-skeletal conditions can be treated effectively and comfortably [7].
The best heat therapy modality is shown in the figure below. It shows the relative
absorption of RF power generated by the Autotherm equipment in comparison with other
energy sources.
-Flit Muscle Bone IC I -Most microwave energy is absorbed in the subcutaneous fatty layer, -where it produces an undesirable heat buildup with little thera- Microwave peutic-value. Penetration into muscle tissue is less deep compared to shortwaves.
- L l c - .G " Muscle, Bone Shortwave: -Condenser pads mainly produce superficial heat with absorption CondenseiField in the fatty layer. Although heat penetrates throughthe'muscle With 2 opposite layer,-it also is generated in the bony tissue. I Pads
(Auto*Therm) °C Bone Shortwave: .- A Shortwave induction field creates very little heat in the fatty Induction laYer. 'Most of the heat is created in the muscle tissue,-where it haS Field-Helical the greatest therapeutic effect.
Depth in tissues (nun)
Figure 4.4 Relative absorption of RF power generated by the Autotherm equipment [21]
The Technical Specifications of Mettler Autotherm equipment are as follows
Weight: Unit: 30 pounds
Dimensions: 40 in (H) x 18 in (W) x 18 in (D), (100 cm (H) x 46 cm (W) x 46cm (D))
Input: 100-240 VAC, 50-60 Hz
Frequency: 27.12 MHz (Wavelength X= 11.06 meters)
RF output: Continuous mode 100 W Average Power, Pulsed mode 200 W Peak Power
Continuous mode: 100 Watts Average Power
Pulsed Mode: 200 Watts Peak Power 35
Pulse frequency: 10 Hz, 20 Hz, 50 Hz, 100 Hz, 400 Hz
Pulse duration: 65 Jis, 100 pts, 200 jts, 300 ps and 400 gs
Treatment time: 1-30 minutes [7].
4.3 Advantages of Mettler Shortwave diathermy unit
1. Light weight
2. Treatment arm is spring balanced for precise positioning and easy access to all
body areas.
3. Timer switch helps to calculate the accurate treatment lengths.
4. The Unit is always in tune with the help of patented self tuning circuitry
5. Shortwave diathermy (27.12 MHz) does not overheat the skin and increases the
temperature at a maximum depth of 1.6 cm below the skin surface
6. A single dosage intensity control regulates patient power demand.
7. Maximum portability
Shortwave diathermy is effective when deep heating of tissues in required. Some other
benefits include decreased joint stiffness, increased vasodilatation, muscle spasm relief
and reduced pain from ligamentous sprains and strains.
4.4 Safety precautions while using Autotherm
In this shortwave diathermy unit, there is a radio frequency field that exists around the
cables, which carries electrical energy from generator to the applicator head. There is
very little heating of the air that surrounds the cables. It absorbs little energy from the radio-frequency fields. But care has to be taken, as the heating can occur even if a 36 partially conductive material is located within the field produced by the cables. There can be various factors affecting the heating; even the output setting of the generator can also contribute to the heating. A very concentrated field exists when the cable is located near a grounded or conductive object, hence the cables should be positioned away from each other. When the Autotherm is turned on, the patient or the person who treats should avoid touching the equipment. Care must be taken that the applicator may not be immersed in any other fluid before implantation. Perform a thorough assessment of the equipment function before using it on the patient for treatment as it could lead to 37
Chapter 5
EXPERIMENTAL RESULTS WITH AUTOTHERM UNIT
The equipment used is the microwave applicator Auto-therm made by Mettler C)
and series of experiments were conducted. The first phase involves using lossy material
such as clay. The experiments to be conducted with the clay would be taken at different
levels. The temperature measurements were taken at different depths of the clays starting
at the surface, one and half inch below the surface and two and half inches below the
surface of the clay. These results will give us an insight about the duration required to
heat the deep human tissue.
All these measurements will be taken with utmost accuracy of the
instrument with the consideration of the time and intensity of the Mettler Diathermy
system. The measurements were taken on synthetic materials like hardening and non
hardening clay. These materials have dielectric properties close to human tissues.
5.1 Measurements with the hardening clay medium
The measurements were taken using hardening clay with and without reflectors to
study the effects at different depths, where the applicator is placed above the clay volume. Two types of measurements were taken, one with the clay and the Autotherm and the other with the clay and reflector. Clay was chosen as this can be the possible model that can be experimented with that is close to the human tissues with some water 38 content in it. The moisture content of the clay was not measured. In the future projects it is recommended to measure the moisture content as that might helpful in choosing the clay models that would simulate closer to human tissue. The measurements seemed very effective when the reflectors were used. The measurements were taken for different depths inside the clay.
5.1.1 Measurement with applicator on top of clay
The applicator was placed above the flat clay section. The stabilizing temperature was noted. The measurements were taken every 20 minutes, to see the accuracy in the
readings. The measurement was started at room temperature at around 70 0 F. The Table
5.1 below shows the readings when the applicator was kept on top of the clay
Time(min) Achieved Temp (0 F) 0 73.17 20 76.09 40 77.79 60 78.74 80 79.58 100 80.25 120 80.65
Table 5. 1 Heating results with hardening clay medium
(Applicator on top of the clay)
The graph was plotted for the above achieved temperature and time. The graph shows a gradual increase in temperature. 39
82
81
80
79
IL, EI78 vE 78 -7-- TBV1UATUFRF)
Ea 76
74
73
72 0 50 100 150 Time (min)
Figure 5. 1 Graphical representation of Temperature distribution Vs Time
(Applicator on top)
The experiment was repeated with different depths, applicator was placed D=1.5" from the top of the clay. The temperature went slightly higher when compared to the applicator on top of the clay. The Figure 5.2 shows the depth D= .5" from the surface of the clay
W,; _=
Figure 5. 2 Thermometer inside clay at a depth D=1.5 inches 40
Time(min) Achieved Temp (° F) 0 65.20 20 74.48 40 76.90 60 78.83 80 79.80 100 80.90 120 81.39
Table 5. 2 Heating results with hardening clay medium
(Applicator at D=1.5" top of the clay)
80 - A - - 0
70 -
60
2 50
i -| - Curmilative Term (FF) co 40 E I 30
20
1 0
0 0 20 40 60 80 100 120 140 Time (min)
Figure 5. 3 Graphical representation of Temperature distribution Vs Time
(Applicator at D=1.5" top of the clay)
The experiment was repeated for some more heat variation with the applicator at a depth
D= 2.5". There was a considerable increase in temperature as expected. The Figure 41 below shows the position in which the thermometer was placed at a D=2.5 inches form the surface of the clay
Figure 5.4 Thermometer inside clay at a depth D=2.5 inches
The Table below shows the achieved temperature with the setup of D=2.5 inches. The
temperature went to 82.40 0 F at 120 minutes.
Time(min) Achieved Temp (° F) 0 66.90 20 73.42 40 77.21 60 79.54 80 80.75 100 81.32 120 82.40
Table 5. 3 Heating results with hardening clay medium
(Applicator at D=2.5" top of the clay) 42
90
80
70 -
iz 60
e 50 50 -+- TENP6ERATiJRE( 0F) a.o 40 E i_ 30
20
10
0 0 50 100 150 Time ( min)
Figure 5. 5 Graphical representation of Temperature distribution Vs Time
(Applicator at D=2.5" top of the clay)
The same set of readings were repeated with the reflector with 3 different depths using the reflector
5.2 Measurements with clay using Reflector
The experiments were repeated using the reflector which will help in conserving the amount of power and the frequency used for radiation. The experiments were done on the clay with the reflector clamped along with the Mettler © Diathermy system. The aim of these experiments is to check the time it requires for the clay to get to the desired temperature using a reflector. The temperature measurements will be taken on the surface, one and half inch below the surface and two and half inches below the surface of 43 the clay. This part of the measurements was challenging. The reflector was kept at a 45 degree angle to the clay and the readings were taken with accuracy.
Time(min) Achieved Temp (° F) 0 71.41 20 74.12 40 75.46 60 76.05 80 77.08 100 78.10 120 79.07
Table 5. 4 Heating results with clay medium and reflector
(Applicator on top of the clay)
The temperature distribution was plotted for various time intervals. The graph shows that
the temperature went high at constant intervals.
80
79
78
77
I-- TeRmATUw-F)I E 75 E 0I.74
73
72
71 0 20 40 60 80 100 120 140 Time (min)
Figure 5. 6 Graphical representation of Temperature distribution Vs Time
(Applicator on top of the clay) 44
The applicator was kept at the depth of D= 1.5" with the reflector and the temperature was noted. The reflector seemed to be efficient as the temperature increased as expected
Time(min) Achieved Temp (° F) 0 69.59 20 73.62 40 76.82 60 78.88 80 80.47 100 81.61 120 82.69
Table 5. 5 Heating results with clay medium and reflector
(Applicator at D=1.5" top of the clay)
84
82
80
, 78 z/*/
0 - 76 -4- THfSERATUR7WF)| a. E E 74 -
72-
70 - ,
0 20 40 60 80 100 120 140 Time (min)
Figure 5. 7 Graphical representation of Temperature distribution Vs Time
(Applicator at D=1.5" top of the clay) 45
The same experiment was repeated for a depth of D=2.5" and surprisingly the temperature went higher than the previous readings. This is a good example to show that more the depth of the applicator inside the skin, more heat would be generated within the tissues and more number of tumor cells can be destroyed
Time(min) Achieved Temp (° F) 0 70.12 20 74.82 40 77.90 60 79.65 80 81.93 100 83.19 120 84.47
Table 5. 6 Heating results with clay medium and reflector
(Applicator at D=2.5" top of the clay)
70 4
60
I. 50 +- TleNMATURE(F)| 40 E 0 'An
0 20 40 60 80 100 120 140 Time (mIn)
Figure 5. 8 Graphical representation of Temperature distribution Vs Time
(Applicator at D=2.5" top of the clay) 46
5.3 Measurements with the non hardening clay
The non hardening clay was chosen to see if there can be a temperature increase if there was more moisture content. The readings were not as expected, however it was close and sometimes higher than temperature obtained from the hardening clay.
Three different set of measurements were taken depending on the applicator being placed, top of the clay 1.5" below the surface of the clay and 2.5" below the surface of the clay.
Time(min) Achieved Terp (° F) 0 74.5 20 76.18 40 77.50 60 78.01 80 78.15 100 79.53 120 80.12
Table 5. 7 Heating results with non hardening clay medium
(Applicator on top of the clay)
Time(min) Achieved Temp (° F) 0 71.89 20 73.15 40 76.85 60 77.15 80 78.62 100 79.45 120 81.58
Table 5. 8 Heating results with non hardening clay medium
(Applicator at D=1.5" of the clay) 47
Time(min) Achieved Temp (° F) 0 73.33 20 74.61 40 75.89 60 77.83 80 79.24 100 81.20 120 82.63
Table 5. 9 Heating results with non hardening clay medium
(Applicator at D=2.5" of the clay)
The Figure 5.9 shows the comparison chart for hardening and non hardening clay
Comparison chart for hardening and non hardening clay
90 - 84
80 -.- Temp (F0) Probe on the top with
70 - hardeningok .- 80clay SOf-Temp (F0) - Probe at D=1.5" with
- 60 78 hardening clay --.- Temp (F°) Probe at O=2.5" with 50@ ~ 76 -hardening ' He's clay
0 4D 40 - tY A/74Temp (F) Probe on the top with E K non hardening clay E a30 - 72 x Temp (F0) - Probe at D=1.5" with non hardening clay - 7 T0emp (F0)- Probe at D=2.5" with non 10 68 hardening clay
0 I I I 66 1 2 3 4 5 6 7 Time ( interval of 20 min )
Figure 5. 9 Comparison graph for the clay models temperature distribution Vs Time 48
The results were not as expected, however if we notice in Figure 5.9, when the depth of the applicator was at D=2.5" from the surface of the clay, the results seem to be higher.
These results helped to study the use of the diathermy system in the cancer treatment and also helped me understand the various aspects that can help in heating. The medium
(dielectric constant) and the depth at which the heating can take place play a major role in the cancer treatments 49
Chapter 6
CONCLUSION
The research throughout this project led to studying the effects of Hyperthermia on human body tissue. By observing materials that come close to the properties of human skin, we could study the temperature and the duration it took to damage or destroy the cancer cells.
Clay was selected to study the effects on human tissue as it comes close to simulating the effects of our treatment. This helped in observing the effects and intensity of radiation on human tissue.
Heat also appears to make cells more sensitive to radiation by preventing radiation- damaged cells from repairing themselves [23]. When used as an adjunct to chemotherapy, hyperthermia may potentiate the effects of some chemotherapeutic agents such as bleomycin, cisplatin, cyclophosphamide, melphalan, mitomycin C, and nitrosoureas [24].
In this project, I was able to position the system similar to the way actual diathermy process treatment is performed on the human body. The experiments were performed with a 27.12 MHz Mettler Diathermy machine. The duration and intensity of the system were constantly monitored during the experiments. 50
In order to study different scenarios, the experiments with clay were carried out under
different durations and varying depths. Temperatures were constantly monitored to study
the results. A reflector was also used in the project in order to reduce the amount of
power and duration used for the process of diathermy. Experiments were conducted at intervals of 20 minutes so that the process could be thoroughly studied using conditions
similar to the real world.
One of the difficulties that were faced during this project was with the non hardening
clay. The readings were expected to be higher than the hardening clay but the results
were lower than expected which was not satisfactory. A better temperature sensor is
recommended for the future projects. Our future projects should be to standardize the
temperature measurement, to make it easier to obtain temperature measurement. Also the
moisture content of the clay models was not measured. It is recommended to measure the
moisture content in the future projects
All these experiments were conducted with one aim -- to determine the temperature that
can be used to destroy and kill cancer cells during the diathermy process. The
experiments also focused on being as efficient and accurate as possible. This was all part
of the research to get an insight into the process of the effects on a real human tumor.
As we work towards a cure for cancer, this is an effort to make the treatment process more effective, accurate and successful. 51
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