MRI Signal Processing and Imaging - Capstone Project Example

Medical imaging and computerized image processing have been characterized by significant technological advancements over the last three decades. The advancement in these technologies has led to the development of more sophisticated and efficient imaging modalities that have significantly improved both diagnosis and treatment of various diseases. These technologies provide medical practitioners with the capability to obtain detailed information related to the anatomy, physiology, metabolic, and other useful information from the human body.

The most common imaging technologies include; Ultrasound, Computed Tomography ( CT scan), X-Rays, Magnetic Resonance Imaging (MRI), Single Photon Emission Computed Tomography (SPECT), and Positron Emission Tomography (PET). These technologies have undergone continuous advancement over the years and are currently characterized by complex instrumentation and the use of hi-tech computer technology for data collection and image reconstruction. Among these medical imaging technologies, Magnetic Resonance Imaging has become the most favorable and outstanding imaging technology for medical practitioners as well as researchers.

Since its inception in the early 1970s, Magnetic Resonance Imaging (MRI) has rapidly developed into an invaluable medical imaging technology.Magnetic Resonance Imaging is regarded as an invaluable medical imaging technology because of its ability to produce images of outstanding quality non-invasively with no adverse side effects such as exposure to X-ray radiation. MRI is a versatile imaging technology and is widely used to image soft tissues of the body. It is also the most preferred technology in other imaging applications such as observing blood flow, distinguishing the gray and white matter of the brain, and measuring cortical thickness among other diagnostic as well as medical research applications.

MRI is a tomographic imaging technique with the capability of generating both 2-D and 3-D images of a human body. 

Unlike X-Ray CT scan, MRI does not rely on transmission of external radiations to produce an image. MRI uses the natural magnetic properties of the human body to generate detailed images of the selected body part. This technology relies on selected nucleus within the body to generate an electromagnetic signal necessary for imaging. The preferred nucleus for MRI imaging is the hydrogen nucleus. The hydrogen nucleus is the preferred nucleus for imaging purposes because of the high hydrogen presence in water, body fluids and in body fat hence providing a reliable basis for imaging.

In addition, there is variation in density of hydrogen protons in the human tissues when the chemical composition of the tissues changes. Therefore, the difference in the MRI signal depends on the difference in the hydrogen nuclei within the body tissues and physiological structures. During an MRI scanning process, the human body is exposed to a strong magnetic field in the MRI scanner. The magnetic field aligns up all the hydrogen protons. Due to the uniform alignment of protons, a magnetic vector is formed along the axis of the scanner.

Radio waves are then introduced to the formed magnetic field at a predetermined frequency to deflect the alignment of the magnetic vector. This makes the hydrogen nuclei to form a rotating magnetic field that can be detected by the MRI scanner. When the radio wave is switched off, the magnetic field regains its initial alignment and a radio wave signal is produced. This signal is then collected by receiver coils placed at the parts of the body to be imaged. The intensity of this signal is plotted on a grey scale and later used for image construction.

The strength of the magnetic field and the frequency of the radio waves can be varied along the various sections of the body to obtain 2D images or 3D images. Since various body tissues have different relaxation times, different body tissues can be identified separately. For instance, the signal from the fat tissues can be removed to remain with the signal from abnormal tissues. A typical MRI examination involves a series of pulse sequences. The multiple pulse sequences allow the examination to emphasize particular tissues or abnormalities.

In spite of the outstanding imaging capability and the versatility of MRI, this technology is characterized by several limitations. For instance, loud noises are usually emitted from MRI coils during scanning. In addition, the MRI requires a long time to produce high quality images. An MRI brain scan takes about ten to fifteen minutes. Moreover, multiple scans are usually required hence extending the scanning period to almost an hour. During this scanning period, the patients are required to remain still.

This requirement can be extremely challenging to certain groups of people such as children, the elderly and patients experiencing great pain. It is also important to note that some subjects will experience claustrophobia during imaging because MRI bores are usually narrow enclosed spaces. Scanning time is also constrained by physiological factors that are related to the interaction between magnetic fields and the human body. Studies show that if the magnetic field is varied at very high rates, electric currents can be induced in the nervous system of the subject.

Such currents can cause nerve stimulation hence irritating the subject. Long scanning times increase imaging costs and reduce the availability of the equipment. Several studies have been carried on MRI imaging with the aim of minimizing its limitations. For instance, major improvements have been realized in the design of MRI hardware such as the RF coil and regulation of the magnetic field. These improvements have greatly enhanced the image quality and reduced the image acquisition time. Nevertheless, more research is still required in order to realize significant improvement in image quality as well as scan time. .2 Motivation MRI is an invaluable imaging technique to medical practitioners and medical researchers.