Inglés Técnico I Diagnóstico por Imágenes Prof. Natalia SívoriWhat is Bone X-ray (Radiography)?

An x-ray (radiograph) is a noninvasive medical test that helps physicians diagnose and treat medical conditions. Imaging with x-rays involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body. X-rays are the oldest and most frequently used form of medical imaging.

A bone x-ray makes images of any bone in the body, including the hand, wrist, arm, foot, ankle, knee, leg or spine.

What are some common uses of the procedure?

A bone x-ray is used to:

diagnose broken bones or joint dislocation. demonstrate proper alignment and stabilization of bony fragments following treatment of a fracture. guide orthopedic surgery, such as spine repair/fusion, joint replacement and fracture reductions. look for injury, infection, arthritis, abnormal bone growths, bony changes seen in metabolic conditions. assist in the detection and diagnosis of bone cancer. locate foreign objects in soft tissues around or in bones.

How should I prepare?

Most bone x-rays require no special preparation.

You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, eye glasses and any metal objects or clothing that might interfere with the x-ray images.

Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby. See the Safety page for more information about pregnancy and x-rays.

What does the equipment look like?

The equipment typically used for bone x-rays consists of an x-ray tube suspended over a table on which the patient lies. A drawer under the table holds the x-ray film or image recording plate.

A portable x-ray machine is a compact apparatus that can be taken to the patient in a hospital bed or the emergency room. The x-ray tube is connected to a flexible arm that is extended over the patient while an x-ray film holder or image recording plate is placed beneath the patient.

How does the procedure work?

X-rays are a form of radiation like light or radio waves. X-rays pass through most objects, including the body. Once it is carefully aimed at the part of the body being examined, an x-ray machine produces a small burst of radiation that passes through the body, recording an image on photographic film or a special digital image recording plate.

Different parts of the body absorb the x-rays in varying degrees. Dense bone absorbs much of the radiation while soft tissue, such as muscle, fat and organs, allow more of the x-rays to pass through them. As a result, bones appear white on the x-ray, soft tissue shows up in shades of gray and air appears black.

Until recently, x-ray images were maintained as hard film copy (much like a photographic negative). Today, most images are digital files that are stored electronically. These stored images are easily accessible and are sometimes compared to current x-ray images for diagnosis and disease management.

How is the procedure performed?

Inglés Técnico I Diagnóstico por Imágenes Prof. Natalia Sívori

The technologist, an individual specially trained to perform radiology examinations, positions the patient on the x-ray table and places the x-ray film holder or digital recording plate under the table in the area of the body being imaged. When necessary, sandbags, pillows or other positioning devices will be used to help you maintain the proper position. A lead apron may be placed over your pelvic area or breasts when feasible to protect from radiation.

You must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image. The technologist will walk behind a wall or into the next room to activate the x-ray machine.

You may be repositioned for another view and the process is repeated. Two or three images (from different angles) will typically be taken around a joint (knee, elbow or wrist).

An x-ray may also be taken of the unaffected limb, or of a child's growth plate (where new bone is forming), for comparison purposes.

When the examination is complete, you will be asked to wait until the radiologist determines that all the necessary images have been obtained.

A bone x-ray examination is usually completed within five to 10 minutes.

What will I experience during and after the procedure?

A bone x-ray examination itself is a painless procedure.

You may experience discomfort from the cool temperature in the examination room. You may also find holding still in a particular position and lying on the hard examination table uncomfortable, especially if you are injured. The technologist will assist you in finding the most comfortable position possible that still ensures x-ray image quality.

Who interprets the results and how do I get them?

A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will discuss the results with you.

What are the benefits vs. risks?

Benefits

Bone x-rays are the fastest and easiest way for a physician to view and assess broken bones and joint and spine injuries.

X-ray equipment is relatively inexpensive and widely available in emergency rooms, physician offices, ambulatory care centers, nursing homes and other locations, making it convenient for both patients and physicians.

Because x-ray imaging is fast and easy, it is particularly useful in emergency diagnosis and treatment. No radiation remains in a patient's body after an x-ray examination. X-rays usually have no side effects in the diagnostic range.

Risks

There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk.

The effective radiation dose from this procedure depends on the part of the body being examined. For spine x-rays, the dose is about 1.5 mSv, which is about the same as the average person receives from background radiation in 6 months. For x-rays of extremities, the dose is about 0.001 mSv, which is about the same as the average person receives from background radiation in less than 1 day. See the Safety page for more information about radiation dose.

Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant.

Inglés Técnico I Diagnóstico por Imágenes Prof. Natalia SívoriSee the Safety page for more information about pregnancy and x-rays.

A Word About Minimizing Radiation Exposure

Special care is taken during x-ray examinations to use the lowest radiation dose possible while producing the best images for evaluation. National and international radiology protection councils continually review and update the technique standards used by radiology professionals.

State-of-the-art x-ray systems have tightly controlled x-ray beams with significant filtration and dose control methods to minimize stray or scatter radiation. This ensures that those parts of a patient's body not being imaged receive minimal radiation exposure.

What are the limitations of Bone X-ray (Radiography)?

While x-ray images are among the clearest, most detailed views of bone, they provide little information about muscles, tendons or joints.

An MRI may be more useful in identifying ligament tears and joint effusions in knee or shoulder injuries and in imaging the spine, because both the bones and the spinal cord can be evaluated. MRI can also detect a bone bruise when no crack is visible on x-ray images.

CT is being used widely to assess trauma patients in emergency departments. A CT scan can image complicated fractures, subtle fractures or dislocations. In elderly or patients with osteoporosis, a hip fracture may be clearly seen on a CT scan, while it may be barely seen, if at all, on a hip x-ray.

For suspected spine injury, 3-D reconstructed CT images can be made without additional radiation exposure to help the diagnosis and treatment of the individual patient's condition.

Ultrasound imaging, which uses sound waves instead of ionizing radiation to create diagnostic images, has also been useful for injuries around joints, and in evaluating the hips of children with congenital problems.

History of Medical Diagnosis and Diagnostic Imaging

Radiology began as a medical sub-specialty in first decade of the 1900's after the discovery of x-rays by Professor Roentgen. The development of radiology grew at a good pace until World War II. Extensive use of x-ray imaging during the second world war, and the advent of the digital computer and new imaging modalities like ultrasound and magnetic resonance imaging have combined to create an explosion of diagnostic imaging techniques in the past 25 years.

Milestones in Medical Diagnosis and Diagnostic Imaging

Film Cassettes

For the first fifty years of radiology, the primary examination involved creating an image by focusing x-rays through the body part of interest and directly onto a single piece of film inside a special cassette. In the earliest days, a head x-ray could require up to 11 minutes of exposure time. Now, modern x-rays images are made in milliseconds and the x-ray dose currently used is as little as 2% of what was used for that 11 minute head exam 100 years ago. Further, modern x-ray techniques (both analog film screen systems and digital systems, described below) have significantly more spatial resolution and contrast detail. This improved image quality allows the diagnosis of smaller pathology that could not be detected with older technology.

An x-ray system from the pioneering days.Patients still had to hold the cassettes themselves.

Fluorescent Screens

Inglés Técnico I Diagnóstico por Imágenes Prof. Natalia Sívori

The next development involved the use fluorescent screens and special glasses so the doctor could see x-ray images in real time. This caused the doctor to stare directly into the x-ray beam, creating unwanted exposure to radiation. In 1946, George Schoenander developed the film cassette changer which allowed a series of cassettes to be exposed at a movie frame rate of 1.5 cassettes per second. By 1953, this technique had been improved to allow frame rates up to 6 frames per second by using a special "cut film changer."

Contrast Medium

A major development along the way was the application of pharmaceutical contrast medium to help visualize organs and blood vessels with more clarity and image contrast. These contrast media agents (liquids also referred to as "dye") were fir st administered orally or via vascular injection between 1906 and 1912 and allowed doctors to see the blood vessels, digestive and gastro-intestinal systems, bile ducts and gall bladder for the first time.

Image Intensifier

In 1955, the x-ray image intensifier (also called I.I.) was developed and allowed the pick up and display of the x-ray movie using a TV (television) camera and monitor. By the 1960's, the fluorescent system (which had become quite complex with mirror optic systems to minimize patient and radiologist dose) was largely replaced by the image intensifier/TV combination. Together with the cut-film changer, the image Intensifier opened the way for a new radiologic sub-specialty know as angiography to blossom and allowed the routine imaging of blood vessels and the heart.

Nuclear Medicine

Nuclear Medicine studies (also called radionuclide scanning) were first done in the 1950s using special gamma cameras. Nuclear medicine studies require the introduction of very low-level radioactive chemicals into the body. These radio nuclides are taken up by the organs in the body and then emit faint radiation signals which are measured or detected by the gamma camera.

Ultrasound Scanning

In the 1960's the principals of sonar (developed extensively during the second world war) were applied to diagnostic imaging. The process involves placing a small device called a transducer, against the skin of the patient near the region of interest, for example, the kidneys. This transducer produces a stream of inaudible, high frequency sound waves which penetrate into the body and bounce off the organs inside. The transducer detects sound waves as they bounce off or echo back from the internal structures and contours of the organs. These waves are received by the ultrasound machine and turned into live pictures with the use of computers and reconstruction software.

Digital Imaging Techniques

Digital imaging techniques were implemented in the 1970's with the first clinical use and acceptance of the Computed Tomography or CT scanner, invented by Godfrey Hounsfield. Analog to digital converters and computers were also adapted to conventional fluoroscopic image intensifier/TV systems in the 70's as well. Angiographic procedures for looking at the blood vessels in the brain, kidneys, arms and legs, and the blood vessels of the heart all have benefited tremendously from the adaptation of digital technology.

Over the next ten to fifteen years a large majority of conventional x-ray systems will also be upgraded to all digital technology. Eventually, all of the film cassette/film screen systems will be replaced by digital x-ray detectors. This technology i s currently works-in-progress and is only available at a handful of sites worldwide. An intermediate step called phosphor plate technology in currently available at hundreds of sites around the world. These plates trap the x-ray energy and require an in termediate processing step to release the stored information so it can be converted into a digital picture.

Benefits of digital technology to all x-ray systems:

less x-ray dose can often be used to achieve the same high quality picture as with film digital x-ray images can be enhanced and manipulated with computers digital images can be sent via network to other workstations and computer monitors so that many people can share

the information and assist in the diagnosis

Inglés Técnico I Diagnóstico por Imágenes Prof. Natalia Sívori digital images can be archived onto compact optical disk or digital tape drives saving tremendously on storage

space and manpower needed for a traditional x-ray film library digital images can be retrieved from an archive at any point in the future for reference.

Some modalities like mammography require extremely high resolution film to show the small breast cancers. Digital detectors capable of a similarly high resolution are under development and will hopefully be available in the future. However, digital imag ing is already being used in parallel to high resolution film in breast imaging and breast biopsy systems.

Computed Tomography (CT)

CT imaging (also called CAT scanning for Computed Axial Tomography) was invented in 1972 by Godfrey Hounsfield in England. Hounsfield used gamma rays (and later x-rays) and a detector mounted on a special rotating frame together with a digital compute r to create detailed cross sectional images of objects. Hounsfield's original CT scan took hours to acquire a single slice of image data and more than 24 hours to reconstruct this data into a single image. Today's state-of-the-art CT systems can acquire a single image in less than a second and reconstruct the image instantly.

The invention of CT was made possible by the digital computer. The basic algorithms involved in CT image reconstruction are based on theories proposed by the scientist Radon in the late 1700's. To honor his remarkable discovery, Hounsfield was awarde d the Nobel Prize and was granted Knighthood by the Royal Family of England. An original head-only CT scanner from 1974

Magnetic Resonance (MR)

MR principals were initially investigated in the 1950s showing that different materials resonated at different magnetic field strengths. Magnetic Resonance (MR) Imaging (also know as MRI) was initially researched in the early 1970s and the first MR im aging prototypes were tested on clinical patients in 1980. MR imaging was cleared for commercial, clinical availability by the Food and Drug Administration (FDA) in 1984 and its use throughout the U.S. has spread rapidly since.

Countless scientists have been involved in the innovation of magnetic resonance. The development of MR imaging is attributed to Paul Lauterbur and scientists at Thorn-EMI Laboratories, England, and Nottingham University, England.

Updated: December 30, 2008

Sources

http://www.imaginis.com/faq/history.asp

http://www.radiologyinfo.org/en/info.cfm?pg=bonerad