X-Ray

Ready to book online? Click here.

History

X-Rays were discovered in 1895 by a German physicist – Wilhelm Röntgen.

There was a lot of speculations in regards to the events that led to the discovery of the X-Rays, as Röntgen had requested for his lab records to be burned when he died. It is believed that in November 1895 he was studying the effects of passing an electrical current through gases at low pressure. He was using an electron discharge tube, which he had covered with black cardboard to block the distracting glow caused by electrons striking the tube’s glass walls. At one point he noticed that a fluorescent screen, that was more than a meter away from the tube, also started to glow. Röntgen then tried to block the tube with a variety of materials, such as aluminium and copper, but the mysterious rays were still capable of passing through. He labelled them “X”-Rays, for unknown and they were highly energetic electromagnetic radiation, capable of penetrating most solid objects. When Röntgen held a piece of lead in front of the electron discharge tube, it managed to block the rays, but, to his surprise, he saw his own flesh glowing around his bones on the fluorescent screen behind his hand. He then placed photographic film between his hand and the screen and captured the world’s first X-ray image.

Six weeks later, Röntgen published his work and mailed his colleagues a photograph of the bones of his wife’s hand, showing her wedding ring on her fourth finger. In this way an extraordinary discovery had been made: that the internal structures of the body could be made visible without the necessity of surgery.

By 1896 an X-Ray department had been set up at the Glasgow Royal Infirmary, one of the first radiology departments in the world. The head of the department, Dr John Macintyre, produced a number of remarkable x-rays: the first x-ray of a kidney stone; an x-ray showing a penny in the throat of a child, and an image of a frog’s legs in motion. In the same year Dr Hall-Edwards became one of the first people to use an x-ray to make a diagnosis – he discovered a needle embedded in a woman’s hand. Shortly after, an American physiologist used X-rays to trace food making its way through the digestive system.Bone, which contains calcium, does not let much radiation through and results in white images on the scan. The lungs, which are filled with air, allow nearly all x-rays to pass through the body resulting in a black image.
The public also embraced the new technology—even carnival barkers touted the wondrous rays that allowed viewing of one’s own skeleton in theatrical show. In the first twenty years following Roentgen’s discovery, X-Rays were used to treat soldiers in the battlefields, finding bone fractures and embedded bullets.

 

Physics

X-Rays are produced inside the x-ray tube, when electrons strike a metal target.

The electrons are accelerated from the heated filament and directed by a high voltage towards the metal target (usually tungsten). The collision of the accelerated electrons with the atoms and nuclei of the tungsten target results in production of X-Rays. X-rays and Gamma rays are electromagnetic radiation of exactly the same nature as light, but of much shorter wavelength. Wavelength of visible light is on the order of 6000 angstroms while the wavelength of X-Rays is in the range of 1 angstrom and that of gamma rays is 0.0001 angstrom.

This very short wavelength is what gives X- and Gamma rays their power to penetrate materials that light cannot. These electromagnetic waves are of a high energy level and can break chemical bonds in materials they penetrate. This makes it a type of ionizing radiation, and therefore harmful to living tissue. The breaking of chemical bonds in the living tissue may result in altered structure or a change in the function of cells. A very high radiation dose over a short amount of time causes radiation sickness, while lower doses can give an increased risk of radiation-induced cancer. In medical imaging this increased cancer risk is generally greatly outweighed by the benefits of the examination.

The beam produced at the tube, contains both low and high energy X-Rays. Low energy (also called soft) X-rays are completely absorbed by the body and do not contribute to the image while increasing the radiation dose. Therefore these rays are filtered out by the aluminium sheet to ensure only the higher energy rays reach the patient and an adequate image is produced, which also contributes to lowering the dose.

 

Medical Radiography

A radiograph is an image obtained by placing a part of the patient in front of an X-ray detector and then illuminating it with a short X-ray pulse. Calcium, which is contained in the bones in high quantities, has a relatively high atomic number and is able to efficiently absorb X-Rays. The X-Ray beam that is attenuated by the bones produces a shadow, making them visible on the radiographic image. Organs and tissues such as lungs (filled with air) also show up clearly on the X-Ray because of their very low attenuating properties, creating a shadow that is opposite to the one produced by bones. However, tissues with similar densities and biological composition that are located close to one another are hard to differentiate on the X-Ray.

Generally, radiographs assist in detection of skeletal pathologies as well as some disease processes in soft tissues. A good example would be a common chest X-Ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary oedema. Abdominal X-Ray can detect bowel obstructions, free air or fluid in the peritoneal space. Gallstones and kidney stones can also often be diagnosed with plain X-Ray imaging. When it comes to visualising soft tissues such as the brain or muscles, general X-Rays have very limited diagnostic value.

 

Risks

It has been recognised that frequent exposure to X-Rays could be harmful, and today special measures are taken to protect the patient and doctor. More than 100 years after Röntgen’s first X-ray experiments, Gerrit Kemerink, a medical physicist at the Maastricht University Medical Center in the Netherlands, discovered an X-ray machine from the 1890’s very similar to Röntgen’s original one and used it to X-ray a hand specimen from his hospital. He found that to acquire the image, the hand received a radiation dose 1500 times greater than today’s dosage – which explains why many people who were X-rayed or who worked with the original machines suffered from radiation burns and loss of hair. There was also a marked difference in the exposure time required: it took Kemerink 90 minutes to image the hand using the 19th-century machine, compared to 20 milliseconds using modern X-ray machines.

 

X-Ray Applications

Dentistry

Dental radiography is commonly used in the diagnoses of common oral problems, such as cavities. Specially adapted X-Ray machines are able to produce panoramic images of the entire jaw.

Cardiovascular Imaging (Angiography)

The basic principle of Angiography is subtraction of the acquired images. An initial image is taken of the anatomical region of interest, then a second image is taken of the same region after an iodinated contrast agent 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.

Computed tomography (CT scanning)

This is a medical imaging modality where tomographic images or slices of specific areas of the body are obtained from a large series of two-dimensional X-ray images taken in different directions. With a help of computer software these cross-sectional images can be combined into a three-dimensional image of the inside of the body and used for diagnostic and therapeutic purposes in various medical disciplines.

Fluoroscopy

An imaging technique commonly used by physicians or radiation therapists to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope. In its simplest form, a fluoroscope consists of an X-ray source and fluorescent screen between which a patient is placed. However, modern fluoroscopes couple the screen to an X-ray image intensifier and CCD video camera allowing the images to be recorded and played on a monitor. This method may use a contrast material. Examples include cardiac catheterization (to examine for coronary artery blockages) and barium swallow (to examine for oesophageal disorders).

Radiation Therapy

By the early 1900’s the damaging qualities of x-rays were shown to be very powerful in fighting cancers and skin diseases. The use of X-rays as a treatment is known as radiation therapy and is largely used for the management (including palliation) of cancer. It requires higher radiation energies than for imaging alone.

At EastMed Radiology we offer a comprehensive range of x-ray examinations:

  • Chest
  • Abdomen/Pelvis
  • Spine
  • Joints
  • Specific Regions

 

Ready to book online? Click here.

No charge for ACC
X-ray and Ultrasound

No charge for dating
& 3rd trimester
pregnancy scans

Complimentary CD with
images for 20 weeks
anatomy scan