Post on 13-Apr-2017
transcript
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