Review: Prediction of Respiratory Motion - Prediction and Classification of Respiratory Motion - page 8

Here, medical data come together with multiple angles, and a computer treats this
information to generate an image (referred to as ''cut''). The vision of body images
is similar to the vision of a sliced bread loaf. CT images are widely used for
diagnostic purposes, especially for diagnosing a variety of tumors including lung,
pancreas, liver, and other thoracic and abdominal tumors, because using CT
images can not only validate that tumors exist, but they also determine tumor
position and size to provide clear images for radiation treatment planning
[ 5 , 8 , 40 ]. X-ray computed tomography (CT) including computed axial tomogra-
phy (CAT) and cone beam CT (CBCT) uses rotating X-ray equipment with a
digital computer to produce a clear medical image for all types of tissues [ 41 ].
2.1.5 Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging method that uses the
property of nuclear magnetic resonance, instead of radiative delivery to the patient
to visualize the internal organs and tissues for diagnosis and therapy planning. MRI
aligns the protons in the water atoms within the patient using a strong magnetic
field. Then, a very sensitive radio antenna detects the resonance signal of the
protons that are activated by the electromagnetic pulse of the scanner [ 27 ]. In MRI,
the picture of body images looks similar to a ''cut'' in CT. MRI provides good
contrast between the different soft tissues compared with X-ray CT, so that it can
create a highly detailed image of the scanned body structures in the soft tissues [ 42 ].
The integrated and hybrid MRI modalities also proposed to improve the treatment
outcome [ 23 , 42 ].
2.1.6 Optical Imaging
Optical imaging is a non-invasive imaging method that takes photographs of
biological tissues or organs using visible, ultraviolet, and infrared wavelengths for
clinical diagnosis [ 43 ]. Unlike X-ray photons that penetrate the entire biological
tissue, optical photons interact with biological tissue medium by the property of
absorption and elastic scattering [ 44 ]. Advanced optical imaging modalities have
been recently developed, so they can provide cost-effective and much higher
resolution images than current CT and MRI images [ 43 ]. Optical imaging system
consisting of infrared cameras and external markers can also provide accurate
position of target tracking during the treatment process in real-time [ 45 ].