Medical Imaging: Important Inventions in Photography
The Use of Medical Imaging (Photography)
My most recent post about the history of the camera and photography has inspired me to do some further probing about its implication for medicine and the diagnosis and treatment of diseases. I am not a doctor or a scientist, so I will approach my research, which is conducted solely on the internet, from a layperson perspective. My research is as a mean of educating myself about the different ways in which the technology of imaging (photography) may be linked and what are the medical applications over the years. This is what I've found out about the use of imaging (photography) in medicine.
Medical photography also called biomedical photography has been an important feature of medical documentation since the time of Vesalius and thus has a long history. However, the first application of photography to medicine appears in 1840, when Alfred Donné of Paris photographed sections of bones, teeth, and red blood cells using an instrument called the microscope-daguerreotype. Conventional medical photography apparently began in France when J. G. F. Baillarger photographed cretins (1851), which was followed by a Dr. Behrendt of Berlin photographing his orthopaedic cases in 1852, and in the same year by Dr. Hugh Welch Diamond photographing mental patients at the Surrey County Asylum in England.
During the American civil war 1861-1865, photographs of wounds were taken. The human retina was first photographed in 1885 by William Thomas Jackman and Webster. In 1927 Lovelace made a teaching film demonstrating the life of the mosquito. In 1929 Neuman made a time lapse film of living bacteria. Photography and computer are but two of the most useful tools in both teaching and practical application in investigating and treatment of diseases. Its difficult, if not impossible to think of what would happen without pictures and computers as tools in modern medicine.
X-rays and Radiography
Encarta Dictionary defines X-rays as electromagnetic radiation: a high-energy electromagnetic radiation that can penetrate solids and ionize gas. It has a wavelength between 0.01 and 10 nanometers, which is between gamma rays and ultraviolet light.
Radiography is the use of ionizing electromagnet radiation such as X-rays to view objects. Radiography started in 1895 with the discovery of X-rays. Röntgen discovered a new ray, which was called the Rontgen Ray, or X-Ray. Its medical use was discovered when Rontgen saw a picture of his wife's hand on a photographic plate formed due to X-rays. His wife's hand's photograph was the first ever photograph of a human body part using X-rays.
Although not technically radiographic techniques, imaging modalities such as Positron emission tomography (PET) and Magnetic resonance imaging (MRI) are sometimes grouped in radiography because the radiology department of hospitals handle all forms of imaging. Treatment using radiation is known as radiotherapy.
Diagnostic radiography involves the use of both ionising radiation and non-ionising radiation to create images for medical diagnoses. The predominant test is still the X-ray (the word X-ray is often used for both the test and the actual film or digital image).X-rays are the second most commonly used medical tests, after laboratory tests (blood and specimen tests). This application is known as diagnostic radiography. Since the body is made up of various substances with differing densities, X-rays can be used to reveal the internal structure of the body on film by highlighting these differences using attenuation, or the absorption of X-ray photons by the denser substances (like calcium-rich bones). Medical diagnostic radiography is undertaken by a specially trained professional called a diagnostic radiographer in the UK, or a radiologic technologist in the USA and radiologist in Canada.
To take an X-ray of the bones, short X-ray pulses are shot through a body with radiographic film behind. The bones absorb the most photons by the photoelectric process, because they are more electron-dense. The X-rays leave a latent image in the photographic film; when it is subsequently developed, the parts of the image corresponding to higher X-ray exposure are dark, leaving a white shadow of bones on the film.
To generate an image of the cardiovascular system, including the arteries and veins (angiography) an initial image is taken of the anatomical region of interest. A second image is then taken of the same region after iodinated contrast material has been injected into the blood vessels within this area. These two images are then digitally subtracted, leaving an image of only the iodinated contrast outlining the blood vessels. The radiologist or surgeon then compares the image obtained to normal anatomical images to determine if there is any damage or blockage of the vessel.
The detection of X-rays is based on various methods. The most commonly known methods are a photographic plate, X-ray film in a cassette, and rare earth screens. Regardless of what is "catching" the image, they are all categorized as "Image Receptors" (IR).
According to MedicineNet.com, ultrasound is high-frequency sound waves. Ultrasound waves can be bounced off of tissues using special devices. The echoes are then converted into a picture called a sonogram. Ultrasound imaging, referred to as ultrasonography, allows physicians and patients to get an inside view of soft tissues and body cavities, without using invasive techniques. Ultrasound is often used to examine a fetus during pregnancy. There is no convincing evidence for any danger from ultrasound during pregnancy.
3D ultrasound was first developed by Olaf von Ramm and Stephen Smith at Duke University in 1987.
Nuclear Medicine (CAT scan, CT, PET, MRI)
Widespread clinical use of Nuclear Medicine began in the early 1950s, as knowledge expanded about radionuclides, detection of radioactivity, and using certain radionuclides to trace biochemical processes. Pioneering works by Benedict Cassen in developing the first rectilinear scanner and Hal O. Anger's scintillation camera (Anger camera) broadened the newly emerging discipline of Nuclear Medicine into a full-fledged medical imaging specialty.
Computed tomography (CT) is a medical imaging method employing tomography created by computer processing. Digital geometry processing is used to generate a 3-D image of the inside of a person from a large series of two-dimensional X-ray images taken around a single axis of rotation.
The word "tomography" is derived from the Greek tomos (slice) and graphein (to write). Computed tomography was originally known as the "EMI scan" as it was developed at a research branch of EMI a company best known today for its music and recording business. It was later known as computed axial tomography (CAT or CT scan) and body section röntgenography.
Since its introduction in the 1970s, CT has become an important tool inmedical imaging to supplement X-rays andmedical ultrasonography. Although it is still quite expensive, it is the gold standard in the diagnosis of a large number of different diseases. It has more recently been used for preventive medicine or screening for disease, for example, CT colonography for patients with a high risk of colon cancer.
In clinical practice, Magnetic resonance imaging (MRI) is used to distinguish pathologic tissue (such as a brain tumour) from normal tissue. One advantage of an MRI scan is that it is believed to be harmless to the patient. It uses strong magnetic fields and non-ionizing radiation in the radio frequency range. Compare this toCT scans and traditional X-rays which involve doses of ionizing radiation and may increase the risk of malignancy, especially in a fetus.
Positron emission tomography (PET) is a nuclear medicine imaging technique which produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radiouclide (tracer), which is introduced into the body on a biologically active molecule. Images of tracer concentration in 3-dimensional space within the body are then reconstructed by computer analysis. In modern scanners, this reconstruction is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.
While some imaging scans such as CT and MRI isolate organic anatomic changes in the body, PET and Single photon emission computed tomography (SPECT are capable of detecting areas of molecular biology detail (even prior to anatomic change). PET scanning does this by using radiolabelled molecular probes that have different rates of uptake depending on the type and function of tissue involved. Changing of regional blood flow in various anatomic structures (as a measure of the injected positron emitter) can be visualized and relatively quantified with a PET scan. The disadvantage of PET and SPECT is possibility of unnecessary treatment of anatomic structures which may not be progressive, therefore subjecting patients to unnecessary procedures.
Medical research has been and continues to be an area of much growth as the scientific establishment seek to understand, and treat all kinds of diseases and cancer. The Kanzius machine is one of the latest invention under research for a cure for cancer. My focus has been on how imaging (photography) has evolved over the last two centuries. I have garnered a greater appreciation of the development of some great inventions (X-rays, radiography, ultrasound, CAT scan CT, MRI, PET & SPECT) as tools to be used in investigating and treatment of diseases. Like anything, there are disadvantages (e.g. exposure to radiation), but the benefits of these inventions far outweigh the negative.
I certainly cannot imagine a world without photography, imaging, computer or scientists who are motivated to conduct research to find better ways of treating all kinds of diseases.
Sources that I used in doing this research:
- History od Nuclear Medicine
- History of Radiology
- John Kanzius
- History of Nuclear Medicine
- History of Medical Diagnoses and Diagnostic Imaging
Radiologinfo.org - PET/CT
Online Encyclopedia - Use of Photography in Medicine
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