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Medical Imaging

Image Reconstruction

V F Murphy Monday 26th May 2003

The Image Reconstruction Problem of xray absorption tomography in words X-rays pass through the subject body and interact to a certain extent with those features they pass. The detected X-ray on the other side of the subject contains information relating to every obstacle in the path, and not just to one. The reconstruction problem is to decode these muddled mixes of information into spatial information throughout the subject, by combining information from many paths through the subject. The filter used in Filtered Backprojection. Image artefacts of backprojection the filter corrects. The artefacts are equivalent to the Point Spread Function. The Fourier transform of this function is used.

The filter reduces low frequency information and enhances high frequency information, sharpening edges, and reducing blur. Image reconstruction problem re-cast as an algebraic problem The ray integral equation describes how the detected intensity is related to the attenuation co…

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Obtaining Images with MRI

V F Murphy Monday 26th May 2003

Slice Selection Slice selection is effected by two factors. The first is the bandwidth of the B1 RF pulse, and the second is the gradient throughout the field of view. The smaller the bandwidth [shorter the pulse], the thinner the slice selected. The FOV gradient (z axis) intersects at its null point with the slice selection pulse to find the origin of the slice. Slice selection occurs simultaneously with the B1 pulse. Spatial Encoding The spatial encoding of the selected slice is effected by means of encoding the x and y co-ordinates (anatomical long and short axis) in two different ways. Within the transduced signal there are aspects of frequency, phase, and amplitude. It is in fact these three parts which are used to transmit the information. Spatial encoding of short anatomical axis information is performed on the x axis using the phase encoding method. This involves post B1 RF pulse, which started precession in the given mode, the application of a magnetic field gradi…

The Development of Medical Imaging

Ron Stemple Thursday 1st January 1970

Medical imaging came to be at the turn of the twentieth century with the discovery of X-Rays and their power to penetrate the skin. Their short wave lengths and high energy allowed physicians to see broken bone, and chest X-Rays were used to in the early diagnosis of tuberculosis.

Computed Tomography, CT Scans, or CAT Scans Computed Axial Tomography were the second generation of X-Rays. Tomos is Greek for œslice or œsection , graphia is describing. As named it describes an image of a particular cross section of the body. The technology was invented by people independently in 1972. A British Engineer and a South African born physicist working at Tufts University in Massachusetts. The engineer, Godfrey Hounsfield of EMI Labs in Great Britain won the Nobel Prize and was knighted, but shares credit with Allen Cormack for the invention.

The first CT scanners were installed between 1974 and 1976 and were only for the head. Whole body scanners came very quickly however, a…

The Future of Medical Imaging

Ron Stemple Thursday 1st January 1970

Modern medical imaging has made invasive exploratory surgeries a thing of the past. The X-Ray portions of medical imaging are being phased out by technologies like MR angiography (MRA), CT angiography (CTA), and ultrasound angiography. These are way to detect blockages and plaque in blood vessels with. They also do away with the dyes that can cause anaphylactic shock in rare cases, and minor irritation in others. Conventional angiography will soon only be necessary as an aid for angioplasty surgery.

Magnetic Resonance work is closer to showing not only structure of system in the body, but function of these systems. Echo Planar Imaging or EPI can now show brain activity making it possible for early detection of strokes. Functional Magnetic Resonance (FMR) can show the workings of the myocardium or heart muscle. Other MR procedures can show the movements or coronary vessels, and make a movie like scene of a heart beating. These evolving technologies will begin to come faster as t…

EEG Applications in Modern Medicine

A J Michael Thursday 1st January 1970

Electroencephalography (EEG) or brain imaging has come a long way since its inception more than 100 years ago. English physician Richard Caton discovered the existence of electrical currents in 1875 and later in the 1920s, Hans Berger was the first who recorded brain activity and coined the word electroencephalogram to describe brain electric potentials in humans. Four types of brainwaves are recorded according to frequencies; alpha, beta, theta and delta. EEG is used primarily in studying the properties of cerebral and neural networks in neurosciences:Michel et al 2004

EEG is used primarily in studying the properties of cerebral and neural networks in neurosciences (Michel et al 2004). It is used to monitor the neurodevelopment and sleep patterns of infants in the intensive care unit and ultimately enable physicians to use this information to improve daily medical care (Scher 2004). In epilepsy, EEG in used to map brain areas and to receive localization information that will be …

The Birth of Medical Imaging

Ron Stemple Thursday 1st January 1970

Medical imaging was discovered just like many of histories greatest inventions, by accident in 1895. Physicist Wilhelm Roentgen was working with electron beams in a glass tube and noticed a fluorescent screen in the lab glowing when the beam was turned on. He found that even though his screen was covered with heavy black cardboard, waves of some type penetrated it. He put items between the screen and the tube, and found that he could see through or into items. The most famous being his wife ™s hand. He called his discovery X-rays (X standing for unknown). Roentgen placed a photographic plate behind the screen, and found the image of the bones in her hand and a ring on her finger could be captured on it just like the photographic processes of the day.

Even though the first X-Ray clearly showed the bones in the hand, the uses were not medical at first. Radiography at the time was considered akin to photography. Most of the equipment was owned by independent businessmen who opened up…