Coefficient of Absorption for Living tissues in Microwave Frequency

Range

BY MARYAM LIAQAT

Introduction

Dielectric properties are very important for diagnosis of living tissues and therapies as it produced a onsiderable Contrast for normal and malignant tissues as small as 4% for kidney and as highy as 577% for mammary glands thereffore in this article

Flat-ended coaxial probs are used

In 50-900MHz frequency range At 23-25 Celcius Temperature Network Analyzer used for measuring the parameters Kidney, liver, Lungs, mammary gland and muscles are under study

Flat-ended coaxial probs Diameter of prob must be 0.007m Fringes field are extended for measuements upto 0.5cm depth Size of cell not less than 1.5cm Using vector Newtwork Analyzer admittance calcultes

Vector Network Analyzer (VNA)

Reflection and transmission of electric networks measured at high frequencies using VNA due to following reasons

Work in Time-Domain Charaterizing Scattering Parameters Design based on conjugate Matching

Technique Perform Inverse-Fourier Transform Also known as Gain Phase meter

Amplitude Phase

Absoption CoefficientsTo calculate the absorption coefficients from this data

(-j)

**Microwave Power Absoprtion differences detween normal and malignant tissues by W.T. Jines et al, 1980

2E+008 4E+008 6E+008 8E+008 1E+0091.2E-004

1.4E-004

1.6E-004

1.8E-004

2E-004

2.2E-004

1.2E-004

1.4E-004

1.6E-004

1.8E-004

2E-004

2.2E-004N.Kideny M.Kidney

absoprtion coefficients

Frequency (MHz)

Abs

orpt

ion

coef

ficie

nts 2E-004

1.31E-004

1

f .r

2E-004

1.26E-004

1

.km f .r

9E+0083E+008 f

0E+000 3.33E+008 6.67E+008 1E+0095E-005

1E-004

1.5E-004

2E-004

1.2E-004

1.4E-004

1.6E-004

1.8E-004

2E-004N.Liver M.Liver

absoprtion coefficients

Frequency (MHz)

Abs

orpt

ion

coef

ficie

nts 1.73E-004

9.92E-005

1

f .r

2E-004

1.23E-004

1

.km f .r

9E+0083E+008 f

0E+000 3.33E+008 6.67E+008 1E+0091E-004

1.333333E-004

1.666667E-004

2E-004

1.2E-004

1.4E-004

1.6E-004

1.8E-004

2E-004

2.2E-004N.LungM.Lung

absoprtion coefficients

Frequency (MHz)

Abs

orpt

ion

coef

ficie

nts 1.95E-004

1.12E-004

1

f .r

2.08E-004

1.38E-004

1

.km f .r

9E+0083E+008 f

0E+000 3.33E+008 6.67E+008 1E+0092E-005

4E-005

6E-005

8E-005

1.5E-004

2E-004

2.5E-004

3E-004

3.5E-004N.MammaryM.Mammary

absoprtion coefficients

Frequency (MHz)

Abs

orpt

ion

coef

ficie

nts 6.12E-005

3.5E-005

1

f .r

3.33E-004

1.8E-004

1

.km f .r

9E+0083E+008 f

Microwave Induced Hyperthermia Cancer Therapy Technique Microwaves Trasmissted from one/number of Antennas Repeated Heating of tumor to over just 40 degree Celcius (about 108 °F for

an hour) Damage the cell membrane damage and cause destruction of tumor Heat effect is controlled by time, frquency and strength Focused heating isn’t allow the heating of srounding tissues Neck and Brain tumor in Children Side Effects can be reduced by increaing Radiation Doses and cytostatic

drugs

Principle of working Microwave Induced Hyperthermia

High-water Content Cancerous tissues Heated special-purpose antennas located adjacent used for source

radiation Number of antennas depend on size and location of tumor

Introduction of Article

Microwave Ablation (MWA) used to cure the malignancies and heptocellular (HCC) cancers of liver Use antennas for power For this Tissue dielectric properties at MW frequencies required Open-ended coaxial Probs are used for this charaterization Contrast between malignant , normal and cirrohtic liver tissues observed Dielctric properties catagrosied as

Narrowband dielectric properties (915MHz-2.45GHz) Wideband dielectric properties (0.5-20GHz)

Experimental setup and Data Acquisition

Open-ended coaxial probe of 3mm diameter Small aperture size Hermetic seal prevents fluid leakage into the aperture Sensing depth of the probe is 1 to 3 mm Vector network analyzer used At 915MHz frequency contrast of malignant liver tissue properties are 16% higher

than normal tissues At 2.45GHz it rises upto 43% for ex-vivo.

Thanks for

attention