The most common cancer diagnosed among the women is the breast cancer. The earliest and most common technology for the detection of breast cancer has many constraints. Patients who undergo this process are subjected to ionizing radiation. This ionizing radiation is harmful to people when exposed frequently. Since the density of the breast varies from person to person, false prediction might occur. The existing methodologies are costly and it does not reach the end users. Later, microwave imaging (MI) techniques are highly recommended in the context of safe and low-cost alternative mammographic approach for breast cancer diagnosis at a premature state. In order to develop the microwave imaging techniques lot of analysis has been made and implemented in laboratory. This literature is mainly focused on various techniques that are used to detect and treat this disease in early diagnosis: radiometry, radiography, digital mammography, endocrine therapy, space time beam forming, thermography, near-field microwave imaging, ultra-sound technique, tomography, microwave breast imaging system and microwave radar imaging.
In recent times, Microwave sensing has been widely used for detection of breast tumor cells. Planar printed monopole antennas have been recently considered for breast cancer imaging due to their simple structure, broadband property, relatively small size, and ease of fabrication. Employing a multi-static array has the advantage of avoiding the mechanical issues of a scanning antenna. Thus, the proposed prototype (microwave -based breast cancer detection) is designed eco-friendly with minimal cost with ease of reach. The main aim of this project is to design a sensor-based antenna for the detection of tumor in such a way that it is highly flexible, cost effective to fabricate, light weight and for detecting without any uncomfortable compressions.
Early stage breast cancer detection with ultra-wideband sensing is presented in [1]. Flexible textile antenna in body-worn applications is given in [2]. Microwave imaging in breast cancer detection is presented in [3-5]. An analysis on breast cancer has been discussed in [6] with the effective mammography undergone in women of 40-49 years. Microwave imaging using antenna arrays and dielectric properties has been given in [7-8]. With the dielectric ranges, diagnostic analysis with phantom models were presented in [9-11]. Flexible layers has been integrated in analysing breast cancer has been demonstrated in [12-18]. Diagnosis with multiple frequency as well as ultrawide band frequency range are all implemented. Dedicated positron emission tomography in breast cancer has been represented in [19]. Physical phantoms [20] and adaptable textile antenna design [21] were also presented.
The antenna is fabricated with a substrate and the conducting plane with resonating pattern sticked together with the feed line of 50 ohm impedance. The substrate used is a double-sided polyimide(lossy) which has relative permittivity as Ԑr=3.5 and electrical tangent as 0.0027(Const.fit). The dimension of the substrate is 20mm x 20mm x 0.085mm. The antenna designed is a printed monopole planar antenna which is composed on the polyimide substrate. The design of the monopole antenna is made of copper whose electrical conductivity is infinite and resistivity is zero.
Kapton is a polyimide film with a wide range of temperatures from -269 to 400 degree C. Kapton is a flexible printed circuit which is used in spacecrafts, satellites and for various applications. Kapton is regularly used as an insulator in having ultra - high vacuum environment due to its low out gassing rate. The kapton material is used as a biocompatible substrate with a thickness of 0.05 mm. The relative permittivity of the kapton material is 3.5 and conductivity of 1s/m. This is lossy material with electric tangent of 0.0027(Const.fit). A commercially available Kapton polyimide has been given in Fig 1.
Copper is used as a radiating element. The radiating element is printed on either side of the dielectric substrate. One side radiates EM radiation whereas the other side fully covers the bottom of the substrate acting as ground plane; hence it is called conductor backed coplanar waveguide (CPW), where the ground plane acts as third return conductor. The connector is connected to either side of the dielectric substrate at the feeding end. The proposed model of prototype has been presented in Fig.2. The parametric values for the proposed prototype have been given in Table 1. The parametric values have been derived from the basic empirical formulas.
Table 1 Parametric Values for Proposed Prototype
The surface current distribution for the proposed model has been given in Fig 3. The surface current on excitation gives 33.2 A/m at 5.5 GHz resonance. Fig 4 gives the reflection coefficient of the proposed prototype on simulation. Fig 5 gives the 3 dimensional radiation pattern of the prototype at 5.5 GHz.
As the proposed model has to be applied over body surface, SAR analysis is carried out at the acceptable ratio of 4.47/10 gram. The value cited is the maximum level measured in the body part studied over the stated volume or mass. The SAR analysis has been depicted in Fig 6.
Four identical monopole antennas are placed on the substrate constituting array model for exact diagnosis of can cancerogenous changes in breast tissue. The antenna prototypes are tilted to adapt to the cup shape of the breast model. Antenna 1 and Antenna 3 are diagonal to each other. In the same way Antenna 2 and Antenna 4 are diagonal to each other. The antennas 1 and 3 are rotated to 30 degree whereas the antennas 2 and 4 are rotated to -30 degree. The waveguide transmission port is feed to the copper material with dimension 5mm x 5mm.The electrical field in the boundaries around the antennas are reduced to zero(Et = 0). The placement of array of antenna before and after rotation has been given in Fig 7.
The array simulated with four antenna modules to analyze the reflection coefficient of the antenna and is given in Fig 8. The datasets generated and analyzed in the proposed prototype are given in graphical module and produced on reasonable request by the corresponding author.
Radiation pattern of the proposed prototype for port 1 has been given in Fig 9 in 3D as well as in polar chart. The maximum field effect with the prototype has been witnessed as 23.49 dB(V/m) with an efficiency of 78% at 5.5 GHz.
For analysis of the antenna with breast model for further implementation, the skin, breast tissue and tumor are represented in the form of brick in the proposed design. The biological characteristics of the breast tissue from the literature are as given below in Table 2
Table 2 Dielectric properties
Parameters
|
Electrical
Conductivity(S/m)
|
Electrical Permittivity
|
Skin
|
1.1
|
39
|
Breast tissues
|
0.59
|
4.49
|
Tumor
|
4
|
50
|
Skin phantom also known as tissue phantom, which are synthesized structures intended to accurately mimic desired properties of skin for experimental testing. Desired properties include electrical conductivity, permittivity and biological properties. These skin phantoms can be used for early stage testing of wearable medical devices to minimize animal, human and cadaver testing. Before real time testing in order to detect the tumor cells a tumor like substance is also added to the physical breast phantom. A phantom model has been given in Fig 10.
For our simulation process, brick shaped tissue layers are designed behind the prototype and tumor is also embedded within the layer as given in Fig 11. Then the designed prototype model with the added layers are all bent for better results, as the breast is curve shaped. The simulation model of bent layers of the prototype is depicted in Fig 12.
Fig 13 gives the reflection coefficient of the layered prototype and Fig 14 gives the radiation pattern with gain of 2.97 dBi. The further adaptation of this design is to create a wearable flexible antenna array be achieved by using a physical phantom.