Review: Prediction of Respiratory Motion - Prediction and Classification of Respiratory Motion - page 6

Chapter 2
Review: Prediction of Respiratory Motion
Radiation therapy is a cancer treatment method that employs high-energy radiation
beams to destroy cancer cells by damaging the ability of these cells to reproduce [ 1 ].
In external beam radiotherapy (EBRT), specific parts of the patient's body are
exposed to the radiation emanating from a treatment machine [ 1 - 3 ]. The X-ray
beams have to penetrate other body tissues to reach the target area during treatment
process. This leads to unnecessary irradiation of healthy tissues around the tumors.
Accordingly, prediction of respiratory motion is a very critical issue in EBRT.
Radiation technologies can consist of two major approaches: (1) tools for measuring
target position during radiotherapy [ 4 - 9 ], where patient-specific treatment param-
eters including acquisition of respiratory patterns, treatment simulation, and target
area planning are determined for treatment preparation, and (2) tracking-based
delivery systems [ 10 - 14 ], where the patient is placed under the linear accelerator
and radiation is delivered using real-time tracking methods under free breathing
conditions.
2.1 Tools for Measuring Target Position
During Radiotherapy
Measuring target position for treatment planning in radiotherapy is heavily
dependent on image processing and patient-specific interpretation methods for
medical data and images [ 15 - 25 ]. There exist several measuring tools for the
target position. Once the target is identified, it is easy to track this defined target in
most imaging modalities [ 26 ]. A number of medical imaging, such as radiographs,
fluoroscopy, computed tomography (CT), magnetic resonance imaging (MRI), and
optical imaging can provide real-time information in company with outstanding
visualization to improve the treatment results during beam delivery [ 23 ]. It is
difficult to detect the target directly in images. The fiducial markers are often
employed to act as surrogates for optical signal tracking.