Page 11 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

8 CHAPTER 1 Introduction

the updated technics with the aim of high sensitivity and being less invasive for
patients.

1.6 Bioengineering assisted cancer imaging using
nonbiological components
Finding the optimal methods of cancer imaging is always received a great atten-
tion not only for diagnostic purpose but also for treatment. The optimal biomedical
imaging needs to have important criterion including less destruction of tissue and
invasiveness, accurate real-time monitoring, feasibility to detect over wide ranges of
tumors, and targeting ability. Size scales are varied from molecular to whole organ-
ism level.
The role of biological component in cancer diagnostic already discussed in Chap-
ter 2. Herein, the brief review of nonbiological systems in cancer imaging will be
reviewed. X-ray imaging technic is based on the ability of the targeted tissue to atten-
uate the irradiated X-ray leading to the formation of the image with different opacity.
Another imaging technic is magnetic resonance imaging (MRI) which is based on
the relaxation time of water in a magnetic field. In general, each compartment has
been surround by water and has a specific relaxation time. Different relaxation time
brings the opportunity to detect the compartments.
Ultrasound is longitudinal acoustic energy with the frequency above 20 kHz.
Irradiation of ultrasound cause particle displacement along with the wave propaga-
tion. Ultrasound imaging is based on the scattering, reflection, and shifts of acoustic
waves. Another application of ultrasound is thermal therapy which will be discussed
in the next topic of this chapter [44].
Another imaging technic is based on nonionizing electromagnetic radiation con-
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tain low photon energy from 1 to 3 × 10 Hz. One of the main differences between
the interaction of ionizing and nonionizing radiation with an atom is that ionizing
radiation cause removing of electron while nonionizing radiation cause electron
excitation and heat production.
The physical properties of imaging systems including resolution and sensitiv-
ity are different. The most sensitive imaging systems are nuclear medicine and
positron-emission tomography (PET). In PET, image is constructed based on the
detection of γ photons released from radionuclides during the annihilation of posi-
tron with electron. A positron annihilates with electrons leading the release of two
photons moving in the opposite directions. The photons will be detected using scin-
tillation crystals.
To increase the accuracy of detecting systems, hybrid imaging systems have been
introduced. For example, PET/CT which is the combination of the spatial resolution
of CT and metabolic sensitivity of PET.
The main obstacles in optical imaging are mainly related to the absorption and
scattering of light by untargeted tissues and fluids. To tackle the problem, smart
nanoparticle targeted to desired tumor is under investigation [45].