**4. Positron emission tomography (PET)**

PET is an imaging procedure that identifies the presence of cancer by using an injection mixture of radioactive materials with sugar and observes how cells react to it. The cancer cells having the characteristics to grow faster than normal cells consume nutrients. When this happens, positrons are emitted. PET makes an image by detecting these positrons. Unlike X-ray, CT, and MRI, PET can detect cancer in the very early stages. However, it has low resolution. PET scanning is combined with other techniques, e.g., PET and CT scan, for further evaluation. Therefore, PET scans cannot be used to detect small-sized tumors in the breast (in the budding stages). But they can be used for identifying the presence of metastasis, spreading to other body parts or spreading to lymph nodes.

## **5. Breast cancer screening using ultra-wide band (UWB)**

In the last decade, the alternative technology which has been in focus of research is breast cancer detection using ultra-wide band (UWB) electromagnetic radiations, i.e., at microwave range. Microwaves provide higher and stronger contrast between healthy tissue and tumors, which supports in better tumor detection without the hazard of ionization effects. UWB microwave imaging can be done, either using microwave tomography or microwave radar imaging. The latter uses power distribution of scattered waves to distinguish between healthy and tumor-containing tissues.

Ultra-wide band (UWB) radio is no more an emergent technology, but rather the past two decades are full of experimentations with UWB for various research applications in wireless communications, radar, and medical fields.

Before the present millennia, UWB was confined totally in military applications. But, since 2002, Federal Communications Commission (FCC) has increasingly allowed the commercialization of UWB bandwidths. Federal Communications Commission (FCC) has standardized that the frequency for the UWB technique is from 3.1 to 10.6 GHz in America. However, in Europe, the frequencies include two parts: from 3.4 to 4.8 GHz and from 6 to 8.5 GHz. Applications of UWB radar in health and medicine include human body monitoring, remote sensing, and imaging. Unlikely with x-ray imaging, UWB radar uses non-ionizing electromagnetic waves which have been proved to be harmless to the human body. Additionally, the UWB radar has a very low-average power level, power efficiency, and robustness against noise. Thus, UWB is a cost-effective way of real-time human body imaging. Categorically, some other features of UWB are enumerated as follows.

**Penetrating through obstacles.** UWB uses RF pulses with high gain. Therefore, UWB can penetrate through walls. This makes UWB practicable for wide area presentations where obstacles are sure to be met. This uniqueness of UWB makes it feasible to image organs of the human body.

**High precision ranging at the centimeter level.** UWB provides an effectively precise ranging to the centimeter level because of highly short-pulse characteristics. The short UWB pulse has a very strong temporal and space-resolving capability, which is appropriate for the localization and detection in the medical diagnostic applications of tumors.

**Low electromagnetic radiation.** UWB also features low electromagnetic radiation because of low radiation power of the emitted pulse. According to the standards, these are less than −41.3 dBm in indoor communications. Again, the low-powered radiation effects the environment very less, which is ideal in medical diagnostic applications involving human body where organs are very close to each other.

**Low processing energy consumed.** As UWB utilizes very short-duration pulses, this permits the use of long-life battery-operated devices. These features are quite analogous with the wireless sensor network (WSN) nodes which essentially have to be operable under strict power control and high power efficiency.

UWB encompasses numerous utmost sought practical features for any electrical instrumentation used in medical applications. These features include noninvasiveness, low power, noncontact remote operation, biocompatibility, biological friendliness, environmental friendliness, detection, and localization. But in terms of tissue imaging, their physiological understandability by the users, high sensitivity (true-positive rate), and high specificity (truenegative rate), UWB requires more research. In this respect, the way human tissues behave with UWB waves emitted on them, i.e., their channel impulse response, is a very important aspect in the research of UWB applications in health monitoring and diagnostic systems.

#### **5.1. UWB microwave tomography**

**4. Positron emission tomography (PET)**

6 UWB Technology and its Applications

**Table 4.** Contrast among different breast cancer detection modalities [11].

other body parts or spreading to lymph nodes.

and tumor-containing tissues.

communications, radar, and medical fields.

**5. Breast cancer screening using ultra-wide band (UWB)**

PET is an imaging procedure that identifies the presence of cancer by using an injection mixture of radioactive materials with sugar and observes how cells react to it. The cancer cells having the characteristics to grow faster than normal cells consume nutrients. When this happens, positrons are emitted. PET makes an image by detecting these positrons. Unlike X-ray, CT, and MRI, PET can detect cancer in the very early stages. However, it has low resolution. PET scanning is combined with other techniques, e.g., PET and CT scan, for further evaluation. Therefore, PET scans cannot be used to detect small-sized tumors in the breast (in the budding stages). But they can be used for identifying the presence of metastasis, spreading to

**Diagnostic procedure Sensitivity Specificity PPV Accuracy** Mammography 67.8% 75% 85.7% 70.2% Mammography and clinical examination 77.4% 72% 58.6% 75.6% Clinical examination 50.3% 92% 94% 63.6% Ultrasound 83% 34% 73.5% 67.8% Mammography and ultrasound 91.5% 23% 72.3% 70.2% Mammography, clinical examination, and ultrasound 93.2% 22% 72.4% 70.9% MRI 94.4% 26% 73.6% 72.9% Mammography, clinical examination, and MRI 99.4% 7% 70.1% 70.5%

In the last decade, the alternative technology which has been in focus of research is breast cancer detection using ultra-wide band (UWB) electromagnetic radiations, i.e., at microwave range. Microwaves provide higher and stronger contrast between healthy tissue and tumors, which supports in better tumor detection without the hazard of ionization effects. UWB microwave imaging can be done, either using microwave tomography or microwave radar imaging. The latter uses power distribution of scattered waves to distinguish between healthy

Ultra-wide band (UWB) radio is no more an emergent technology, but rather the past two decades are full of experimentations with UWB for various research applications in wireless

Before the present millennia, UWB was confined totally in military applications. But, since 2002, Federal Communications Commission (FCC) has increasingly allowed the commercialization of UWB bandwidths. Federal Communications Commission (FCC) has standardized The objective of microwave tomography is to use the inverse scattering method in finding the dielectric properties of the tissue under study. This gives a dielectric contrast of it. It produces a chart of permittivity and conductivity through inversion scattering.

In a microwave tomography breast cancer investigation system, the breast is lowered into a cylinder-shaped antenna system which covers the breast completely. Microwave measurements are then made with all possible combination of antennas, acting as both transmitter and receiver, respectively. Since the microwaves are spread, scattered, and reflected when they penetrate inside the tissue, the wave field becomes very complicated. The large amount of data generated from the extensive wave field is analyzed with a radical image reconstruction algorithm that constructs an image of the internal dielectric properties of the whole body part (tissue under examination). This detection technique depends highly on the dielectric and electromagnetic properties, which are the permittivity, conductivity, and electrical parameters of the cancerous tissue. These properties have been investigated to be much different than those of normal breast tissue [12].

Basically, the system comprises of two things: (1) transmitting and receiving antennas and (2) image reconstruction algorithm. In the measurements each antenna is operated as a transmitter as well as a receiver for every possible combination of antennas. To perform the measurements, a network analyzer with switch multiplexer module can be employed to automatically connect and disconnect transmitting and receiving antennas to the PNA. The low amount of radiated power (typically in milliwatts) is considered harmless for the patient and surrounding environment. In most of the research work, a 2D or two-dimensional image reconstruction algorithm has been used. This is most suitable for imaging 2D objects with dielectric properties that are constant in the z-direction which is taken perpendicular to the antenna plane. However, imaging a three-dimensional or 3D object, the accuracy of a 2D imaging technique is severely bounded. This means that effects would be generating in the z-axis but not being modeled using a 2D image reconstruction algorithm. Therefore, a 3D algorithm is required to accommodate all the effects. In the current systems to develop a clinical prototype, the most suitable designs consist of an antenna array where antennas are placed also outside the plane in a 3D pattern to get z-axis effects. This can be obtained by constructing a cylindrical antenna array. Together with a 3D reconstruction software, the potential for improved accuracy is optimized. However, this has significantly increased computational burden in the reconstruction algorithm.

Although the technique of microwave tomography for detection of cancers has a great potential, but still it is in the experimental stages. The clinical practice of it is still underway and has not been employed as a regular technique like other modalities discussed above. In some clinical studies, the capability to detect breast cancer tumors with microwaves has been shown. However, further clinical studies need to be undertaken in order to get a complete picture of the prospective for microwave imaging in practice. An important aspect related to breast cancer is that depending on the mixture between fatty and glandular tissues in the breast the distinction varies largely between individual patients.

coefficient and S12 or transmission coefficient) the design goal of a suitable ultra-wide band (UWB) transceiver for early breast tumor detection. Both of these scattering parameters can be treated as channel impulse response, depending if the communication system is using reflection or transmission of waves at the receiver end. The consideration was a heterogeneous breast model comprising skin, adipose, and glandular tissues as body (breast) channel with one layer of tumor. Due to dispersive nature of heterogeneous breast, S<sup>11</sup> and S12 varied with frequency. Modeling and simulations were performed for a 4.5 GHz center frequency UWB system. The backpropagated (reflected/scattered) signals showed approximately 63.3% higher amplitude than forward propagated signals for the breast channel with tumor. Analytical expressions were derived and formulated for S11 and S<sup>12</sup> scattering parameters and were simulated for UWB frequency band of 1–6 GHz as shown

Feasibility of the Detection of Breast Cancer Using Ultra-Wide Band (UWB) Technology…

http://dx.doi.org/10.5772/intechopen.79679

9

In these simulations, the following interpretations can be made readily:

**Figure 1.** Trends in reflection and transmission coefficients for normal breast [14].

**2.** Reflection and transmission coefficients show 180° out of phase at any frequency.

parameters are not constants but vary randomly as the frequency changes.

**3.** The dispersions are present in reflection and transmission coefficients. The scattering

**4.** The trends are highly nonlinear. This is because the breast tissue is a nonlinear channel.

**1.** The simulations were carried out from 1 to 6 GHz.

**5.** The concern of center frequency is very important.

in **Figures 1** and **2**.

#### **5.2. UWB radar imaging**

UWB microwave radar imaging rebuilds the image using the reflected wave from objects. This technique unlike microwave tomography reconstructs the scattering power distribution when microwaves are emitted on the breast and their reflected waves are analyzed. It works very much like a ground-penetrating radar (GPR). The origin dates back in 2001 by Hagness and Xu Li in Wisconsin University, USA [13]. In this context it therefore becomes very important to understand the behavior of human tissues as channel to propagate the UWB-emitted waves.

In this relevance, authors in [14] have developed an analytical body propagation model equation for human breast tissue in terms of scattering parameters toward (S11 or reflection Feasibility of the Detection of Breast Cancer Using Ultra-Wide Band (UWB) Technology… http://dx.doi.org/10.5772/intechopen.79679 9

**Figure 1.** Trends in reflection and transmission coefficients for normal breast [14].

penetrate inside the tissue, the wave field becomes very complicated. The large amount of data generated from the extensive wave field is analyzed with a radical image reconstruction algorithm that constructs an image of the internal dielectric properties of the whole body part (tissue under examination). This detection technique depends highly on the dielectric and electromagnetic properties, which are the permittivity, conductivity, and electrical parameters of the cancerous tissue. These properties have been investigated to be much different

Basically, the system comprises of two things: (1) transmitting and receiving antennas and (2) image reconstruction algorithm. In the measurements each antenna is operated as a transmitter as well as a receiver for every possible combination of antennas. To perform the measurements, a network analyzer with switch multiplexer module can be employed to automatically connect and disconnect transmitting and receiving antennas to the PNA. The low amount of radiated power (typically in milliwatts) is considered harmless for the patient and surrounding environment. In most of the research work, a 2D or two-dimensional image reconstruction algorithm has been used. This is most suitable for imaging 2D objects with dielectric properties that are constant in the z-direction which is taken perpendicular to the antenna plane. However, imaging a three-dimensional or 3D object, the accuracy of a 2D imaging technique is severely bounded. This means that effects would be generating in the z-axis but not being modeled using a 2D image reconstruction algorithm. Therefore, a 3D algorithm is required to accommodate all the effects. In the current systems to develop a clinical prototype, the most suitable designs consist of an antenna array where antennas are placed also outside the plane in a 3D pattern to get z-axis effects. This can be obtained by constructing a cylindrical antenna array. Together with a 3D reconstruction software, the potential for improved accuracy is optimized. However, this

has significantly increased computational burden in the reconstruction algorithm.

breast the distinction varies largely between individual patients.

**5.2. UWB radar imaging**

waves.

Although the technique of microwave tomography for detection of cancers has a great potential, but still it is in the experimental stages. The clinical practice of it is still underway and has not been employed as a regular technique like other modalities discussed above. In some clinical studies, the capability to detect breast cancer tumors with microwaves has been shown. However, further clinical studies need to be undertaken in order to get a complete picture of the prospective for microwave imaging in practice. An important aspect related to breast cancer is that depending on the mixture between fatty and glandular tissues in the

UWB microwave radar imaging rebuilds the image using the reflected wave from objects. This technique unlike microwave tomography reconstructs the scattering power distribution when microwaves are emitted on the breast and their reflected waves are analyzed. It works very much like a ground-penetrating radar (GPR). The origin dates back in 2001 by Hagness and Xu Li in Wisconsin University, USA [13]. In this context it therefore becomes very important to understand the behavior of human tissues as channel to propagate the UWB-emitted

In this relevance, authors in [14] have developed an analytical body propagation model equation for human breast tissue in terms of scattering parameters toward (S11 or reflection

than those of normal breast tissue [12].

8 UWB Technology and its Applications

coefficient and S12 or transmission coefficient) the design goal of a suitable ultra-wide band (UWB) transceiver for early breast tumor detection. Both of these scattering parameters can be treated as channel impulse response, depending if the communication system is using reflection or transmission of waves at the receiver end. The consideration was a heterogeneous breast model comprising skin, adipose, and glandular tissues as body (breast) channel with one layer of tumor. Due to dispersive nature of heterogeneous breast, S<sup>11</sup> and S12 varied with frequency. Modeling and simulations were performed for a 4.5 GHz center frequency UWB system. The backpropagated (reflected/scattered) signals showed approximately 63.3% higher amplitude than forward propagated signals for the breast channel with tumor. Analytical expressions were derived and formulated for S11 and S<sup>12</sup> scattering parameters and were simulated for UWB frequency band of 1–6 GHz as shown in **Figures 1** and **2**.

In these simulations, the following interpretations can be made readily:


*6.1.1. Antenna engineering and receiver intelligence*

effective in the laboratory [19, 20].

**6.2. Breast phantoms**

**7. Conclusion**

In the antenna engineering part of the UWB research, researchers have mostly employed patch antenna with their many variants and arrays of them [15–18]. Researchers have also explored many beam-forming techniques to associate them with the antenna structures (adaptive antennas) so that information could be extracted from the received signal. Researchers have used different artificial intelligence tools like neural networks and support vector machines to classify the signals coming from cancer cells and normal cells, which have proved to be very

Feasibility of the Detection of Breast Cancer Using Ultra-Wide Band (UWB) Technology…

http://dx.doi.org/10.5772/intechopen.79679

11

When coming to experimental investigation of UWB for breast cancer detection, another important aspect is the design and development of tissue/organ phantom under investigation. The results obtained on phantoms are expected to be obtained on real tissues. Therefore, phantom making is a research-oriented subject. UWB systems need realistic phantom model tailored to the biochemical as well as morphological features of the breast tissue. Existing breast phantoms are available both in solid and liquid structures [21]. Solid phantoms as compared to liquid phantoms have the ability to hold the desired geometrical shape, thickness, and inhomogeneity as that of multilayered tissues and can be fabricated with controlled electrical properties. The concept of a thin, solid tissue phantom along with its analytical model is a challenging task and has gained attention only in the recent past. After fabrication, extraction of information from such solid phantoms requires precise characterization with respect to changes in composition for different breast density characteristics. This could be done with proper analytical model or channel impulse response of the tissue phantoms. In [22] authors have contributed toward developing a numerical model for both normal and

This chapter has briefly discussed about the procedures of different breast cancer screening and detection including x-ray mammography, MRI, PET, and ultrasound. These are the techniques which are clinically being used commonly around the world. However, survey showed that these testing methods do not give a very good quality measures. In this regard UWB technology for early detection of breast cancers is discussed with their two important

Although many experimental researches have been conducted, but still the clinical translation of this research is not deployed. The clinical practice of UWB will definitely produce new problems which would rectify and improve the UWB technology for screening and detection of breast tumors. But still because of the advantages that UWB has promised to provide are surly to take it a long way and unbeatable competitor against x-ray mammography, MRI,

cancerous breast tissues using finite-difference frequency techniques.

methodologies, namely microwave tomography and UWB radars.

**Figure 2.** Trends in reflection and transmission coefficients for tumor-containing breast [14].

The simulation in **Figures 1** and **2** suggests that investigations along with the body propagation model can lead to more affirmative results to determine and predict the cancerous abnormalities in the breast. For example, at 4 GHz, the reflection coefficient of a normal breast tissue is reaching to 75%, but at the same, the frequency for a tumor-containing breast is reaching to 90%.

#### **6. Research areas in UWB breast cancer detection**

#### **6.1. Receiver design**

As discussed, screening and diagnostic testing for the presence of cancer is a probabilistic process; therefore, UWB should also have a percentage of accuracy, efficiency, and other associated probabilities. However, UWB for breast cancer detection is still not completely used for clinical testing. So, these probabilities haven't been determined yet. But it must be well understood that increasing the true-positive rate and true-negative rate is very much dependent on the accuracy of the received signal. This puts a good responsibility on the receiver to detect the signals correctly. Hence, receiver design is very important. In this regard, two things could be catered: (1) antenna engineering and (2) inducing intelligence in the receiver to separate and classify the signals coming from normal and cancerous breast.

#### *6.1.1. Antenna engineering and receiver intelligence*

In the antenna engineering part of the UWB research, researchers have mostly employed patch antenna with their many variants and arrays of them [15–18]. Researchers have also explored many beam-forming techniques to associate them with the antenna structures (adaptive antennas) so that information could be extracted from the received signal. Researchers have used different artificial intelligence tools like neural networks and support vector machines to classify the signals coming from cancer cells and normal cells, which have proved to be very effective in the laboratory [19, 20].

#### **6.2. Breast phantoms**

When coming to experimental investigation of UWB for breast cancer detection, another important aspect is the design and development of tissue/organ phantom under investigation. The results obtained on phantoms are expected to be obtained on real tissues. Therefore, phantom making is a research-oriented subject. UWB systems need realistic phantom model tailored to the biochemical as well as morphological features of the breast tissue. Existing breast phantoms are available both in solid and liquid structures [21]. Solid phantoms as compared to liquid phantoms have the ability to hold the desired geometrical shape, thickness, and inhomogeneity as that of multilayered tissues and can be fabricated with controlled electrical properties. The concept of a thin, solid tissue phantom along with its analytical model is a challenging task and has gained attention only in the recent past. After fabrication, extraction of information from such solid phantoms requires precise characterization with respect to changes in composition for different breast density characteristics. This could be done with proper analytical model or channel impulse response of the tissue phantoms. In [22] authors have contributed toward developing a numerical model for both normal and cancerous breast tissues using finite-difference frequency techniques.
