X-ray

Nicholas K. Birech

February, 2006

 

X-ray has come a long way since Wilhelm Conrad Rontgen first described a “new kind of ray” back in 1895.  The discovery that X-rays could be used to display the innermost workings of the human body on a photographic plate was of immediate interest to the medical community giving birth to radiology.  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.

 

The transmission and detection of X-rays lies at the heart of the following technologies:

 

  1. Radiography - Creation of images by exposing a photographic film or other image receptor to X-rays.  As the X-rays penetrate solid objects, they are weakened depending  on the object's composition, the resulting picture reveals the internal structure of the object.
  2. Angiography - Visualizing the inner opening of blood filled structures, including arteries, veins and the heart chambers using X-ray.  Since blood has the same radiodensity as the surrounding tissues, a radiocontrast agent (which absorbs X-rays) is added to the blood to make angiography visualization possible.

 

  1. Fluoroscopy - Obtaining real-time images 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.  Modern fluoroscopes couple the screen to an X-ray image intensifier and charged-coupled devices (CCD) video camera allowing the images to be played and recorded on a monitor.

 

  1. Mammography examination - It is a process of using low-dose X-rays to examine the human breast to look for different types of tumors and cysts.

 

Traditional film-based scanners are gradually being replaced by digital systems that are based primarily on caesium-iodide scintillators coupled to flat-panel detectors.  Some systems rely on charged-coupled devices (CCD) rather than flat panels.  With such digitalized systems, the data can be viewed, moved and stored without a single piece of film ever being exposed e.g. computer tomography (CT) and magnetic resonance imaging (MRI)

 

Medical uses

X-ray is commonly used in medical imaging.  X-rays are the second most common medical tests, after blood tests.  This is because bones and some organs (such as lungs) especially lend themselves to X-ray imaging.  It is a relatively low-cost investigation with high diagnostic yield.

 

The use of X-ray in medicine can be categorized into two broad areas

  1. Diagnosis: is concerned with the use of X-ray to aid in the diagnosis of disease.
  2. Radiation therapy: using X-ray radiation to treat diseases such as cancer.

 

Diagnosis

 X-ray is especially useful in the detection of pathology of the skeletal system, but is also useful for detecting some disease processes in soft tissue.

 

Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary edema, and the abdominal X-ray, which can detect ileus (blockage of the intestine), free air (from organ perforations) and free fluid (in ascites (accumulation of fluid the abdomen)).

In mammography X-ray is used to examine female breasts for breast cancer.  It’s also used in detection of gallstones and kidney stones and also in dental examination.  X-rays are also used in “real-time” procedures such as angiography or contrast studies of the hollow organs e.g. barium enema of the small or large intestine using fluoroscopy. 

 

Radiation Therapy

There is more to X-rays than imaging-they can also treat patients by killing cancerous tumors.  When X-rays interact with tissue, they release highly reactive radicals that break the double strands in DNA molecules and cause the rapidly dividing cancerous cells to die. But because X-rays kill both healthy and diseased tissue in equal measure, it is vital to minimize the radiation received by healthy organs and tissue surrounding the tumor.  The goal of radiotherapy is to find the precise location of a tumor using a CT scan-or other imaging technique-and then concentrate the X-rays on it to destroy the diseased tissue.

 

References and Links

 Medical Dictionary Online 

 http://www.online-medical-dictionary.org/X-Ray+Radiology,+Diagnostic.asp?q=X-Ray+Radiology%2C+Diagnostic

 

Yahoo Health directory 

http://dir.yahoo.com/Health/medicine/radiology/

 

BUBL LINK Catalogue of Internet Resources

http://bubl.ac.uk/Link/r/radiology.htm

 

The SRS Educational Resource

http://www.radiology.co.uk/srs-x/

 

RADIOLOGY SOCIETY OF NORTH AMERICA
http://www.rsna.org/
http://www.rsna.org/REG/publications/rg/afip/privateM/1996/0016/0005/1131/3.htm
http://www.scar.rad.washington.edu/RadAnatomy.html
http://eduserv.hscer.washington.edu/hubio553/totrad/SCAR/bonetips.html
 

X-ray General

http://www.geocities.com/HotSprings/1368/ 
http://www.scar.rad.washington.edu/radcourse/bonetips.html
http://www.americasdoctor.com/library_main.cfm?article=yes&id=20528&CATID=51&sessionid
http://my.webmd.com/content/asset/adam_test_skeletal_survey
http://my.webmd.com/content/asset/adam_test_x-ray

 

Wikipedia Articles 

http://en.wikipedia.org/wiki/Radiology

http://en.wikipedia.org/wiki/Diagnostic_radiology

http://en.wikipedia.org/wiki/Computed_tomography