P Shah Navas
Research Cell, Kerala State, IMA

Corresponding Author: Dr. P Shah Navas, Convener, Research Cell, Kerala State, IMA. TC 7/171, Kumaran Asan Nagar, Ulloor, MCPO, Trivandrum –695011. Phone: 9447169693. Email: drshahnavas@gmail.com

ABSTRACT

Introduction: When the x-rays pass through the body they are weakened by the many types and layers of tissues. Bone being denser, absorbs a greater amount of radiation and they appear more prominently (e.g. whiter) than soft tissue.

Objective: Review on X ray and other imaging techniques of bone.

Result: Bone x-rays are the fastest and easiest way for a physician to view and assess broken bones and joint and spine injuries, images for diagnosis and disease management and is particularly useful in emergency diagnosis and treatment.

Figure-1.-Tumor-calcification-around-the-elbow

Figure 1. Tumor calcification around the elbow

In 1895 W.C  Roentgen  invented roentgenograms, which today are simply referred to as x-rays or radiographs. Although x-rays have evolved over the years, the principle remains the same except that today’s techniques utilize only a fraction of the x-ray doses used in the early days of radiology. The x-ray technology is the ‘workhorse’ of  fundamental diagnostic imaging. Testing is fast, easy, and painless. When  the  x-rays  pass through  the body  they are weakened by the many types and layers of tissues. Bone being  denser, absorbs a greater amount of radiation and they appear more prominently (e.g. whiter) than soft tissue. The energy is directed into a film cassette placed behind the targeted body part, held  behind an intensifying phosphor screen.  The screen absorbs x-rays, gives out light and exposes the film, which is subsequently processed to form a final image in  much the same manner as a photographic film.

Figure-2.-Normal-X-ray-of-Elbow-AP-view

Figure 2. Normal X-ray of Elbow AP view

Bone X-ray (Radiography)

Conventional X-rays: Although x-rays   have evolved over the years, the principle  remains  the same  except  –  today’s  techniques utilize only a fraction of the x-ray dose required in the early days of  radiology. It encompasses a wide  range  of techniques and applications. However, in general, x­ ray imaging is broken into two major categories:

  1. Radiographic imaging where a “still image” is made of  a  bone or  organ  and  shown  on  film  or on a computer  screen. A radiograph  may be likened  to taking a picture with a 35 mm camera.
  2. Fluoroscopic imaging where a “movie” is made of an organ (for example, swallowing) and viewed on a TV monitor or computer screen. (fluoroscopy) Plain radiographs in orthopedics allow
  • assessment of  joint  space  narrowing,  sclerosis osteolysis
  • osteoarthritic degeneration  (osteophyte formation, subchondral cysts),
  • post-traumatic deformity, calcified loose joint bodies,
  • pericapsular calcifications, erosions, infections,
  • fractures, dislocations, and trauma imaging
  • osteochondritis dissecans, developmental dysplasias,
  • tumors and allied conditions
  • orthopedic implantation &  appliance position checking etc. X-ray images are maintained as hard film copy  (much  like a photographic  negative) or, more   likely, as  a digital  image that  is  stored electronically. These stored images are  easily accessible and are sometimes compared to current x -ray   images   for    diagnosis   and    disease management. The patient  may  be re positioned  for another  view  and  the process is  repeated. At  least two images (from different angles) will be taken and often   three  images  are  needed  if  the  problem  is 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.
  • The patient will be asked to wait until the technologist determines that the images are of high enough quality for the radiologist to read.

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, images for diagnosis and disease management and is particularly useful in emergency diagnosis and treatment.
  • X-ray equipment is relatively inexpensive and widely used  in all settings, making  it convenient for both patients and physicians. No radiation  remains in the body after an x-ray examination with usually with no side  effects.
  • An invaluable tool for quick  assessment or a better differential diagnosis in emergency room setting  to give a greater  diagnostic accuracy

Risks

  • There is always a slight chance of cancer from radiation. However, the benefit of an accurate diagnosis far outweighs  the risk.
  • During a single x-ray exposure, a patient is exposed to approximately 20 milliroentgens of radiation.  We are all exposed to approximately 100 milliroentgens of  radiation each year from sources like the ultraviolet rays  of the sun and small  traces of background radiation such as uranium, in the soil.
  • Women should always inform prior to X-ray exam if there is any possibility of pregnancy.

What are the limitations of X-rays?

Figure-3.-Digital-Radiograph--of-Skull-lateral-view

Figure 3. Digital Radiograph of Skull lateral view

While X-ray images are among the clearest, most detailed views of bone, they provide little information about the adjacent soft tissues. MRI scans are 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. MR I can also detect  a bone bruise  when no  crack  is visible on  x-ray  images. Ultrasound imaging, which uses sound waves instead of ionizing radiation. has also been useful for injuries around  joints and in evaluating the hips of  newborns, infants and children.

The Differences between MRI and  X-Rays

Figure-4.-MRI-Picture-of--Skull-lateral--view

Figure 4. MRI Picture of Skull lateral view

The main differences between an x-ray and an MRI are the images they produce. An x-ray clearly shows the contrast  between soft  tissue  and  bone  density. So it is often used to examine broken bones. An MRI image  shows  a  better  contrast between  different kinds of soft issue and produces detailed images of the brain and other tissues.

MRI is still a relatively  new procedure when compared to x-ray. At this point, there are no known biological  hazards associated with the MRI. MRI is more  versatile than  x- ray also, as it can  be used to examine a wider variety  or medical  conditions. MRl does  have a few disadvantages though.  People w h o are claustrophobic  have difficulties  staying in  the enclosed area. Most patients are un comfortable staying  still during the exam, which can last up to 90 minutes.  Also, MRI machines usually have a weight limit of around 500 pounds and so obese people cannot he examined. Patients with  pacemakers or  other metal  objects in  their body usually can not  be examined  through  MRI either, due to the extremely powerful magnets used. MRI is much more expensive than other methods of examination also including x­ ray.

Digital Imaging

Figure-5.-Digital-X-rays

Figure 5. Digital X-rays

Digital imaging is still not a universal  tool in orthopedics. but more practices are recognizing its benefits and gradually implementing its technology despite some cost and reimbursement constraints. Digital imaging will eventually eliminate plain film to become the   universal   method. Whether their practices have “gone digital” or not, most orthopedists now agree that plain X-ray film images will one day become  obsolete. In  the meantime, all are  keeping an eye on  the  latest  technology to  prepare  for  the time  when  every  office  and  hospital uses  digital systems.  It cuts  costs significantly for  printing supplies, office space, and access to the digital images is instantaneous.

Figure-6.-The-radiologist-views-the-results-of-f1uoroscopic-examination-of-the-upper-GI-in-real-time-using-a-digital-acquisition

Figure 6. The radiologist views the results of f1uoroscopic examination of the upper GI in real time using a digital acquisition

Digital radiography is currently practiced through the use of three commercial approaches, two of which also depend on phosphor screens. The first phosphor based approach is to digitize the signal from a video camera  that is optically  coupled to  an x-ray image intensifier to provide an instant readout. The flat panel detector coated with   an  x-ray photoconductor such as a-Se provides one of the best ways  to realize  the benefits of digital radiography.

The a-Se method has potential  for use in fluoroscopy (real-time  interactive x-ray imaging) In fluoroscopy a video image on the monitor enables the radiologist to see  a  moving  x-ray  picture  of the  inside  of  the human body.

Digital (or computerized) imaging techniques carne  to x-ray  in the  1980s  when  analog  to digital (AID)  converters  and computers were also adapted to conventional  fluoroscopic image  intensifier/TV systems.  Many  of  the  fluoroscopic (“fluoro” for short)  x-ray procedures  described  herein have benefited greatly  from the  addition of  digital technology. Further, 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.

Figure-7.-The-digital-x-ray-image-from-the-fluoroscopic-GI-study-shows--a-normal-stomach

Figure 7. The digital x-ray image from the fluoroscopic GI study shows a normal stomach

Digital Radiography

Using a new adaptation of CCD (Charge Coupled Devices) imaging technology originally developed for  space  exploration,  x-ray images are captured  directly into digital  format. The new digital  x-ray (DR)  imaging  technology, similar to digital  photography, provides immediate image review and better image quality along with many advantages of  electronic  image distribution and storage. It requires 30 – 50% less radiation dose than conventional film  based radiographic methods. The new technology  saves time and money by eliminating waiting periods and saves costs on film processing logistics.  Several  types of   radiography  and fluoroscopy are available to image the anatomy  and function of a wide variety  of organs  and bones.

Tele-Radiology

The  x-ray  images  can be quickly   transmitted on  a number  of special  diagnostic reading monitors  and the images themselves can be analyzed by computer, viewed  at  distant  settings – The  digital   images  are stored  on  a bank  of servers and  printed  for a high resolution image of the digital x-ray on paper for hard copies. Special  picture  archiving technology  also allows the practice  to display  and store MRJ images on the same  viewing  network.

Future Potential

Over  the next ten to fifteen  years a large  majority  of conventional   (basic) x-ray  systems will  also   be upgraded to all digital technology.  In addition to digital fluoroscopic systems (described above), eventually, the majority of film cassette/film screen systems will be replaced by digital x-ray detectors. This technology is currently very  new  and  is now  available at  a handful of  sites  worldwide. An intermediate step called phosphor plate technology is currently available at hundreds of sites  around  the world. These  plates trap  the  x-ray  energy and  require  an intermediate 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 include:

  • Lower dosage x-rays  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 and sent  via a network to other workstations and computer monitors so that many people can share the information and assist in the diagnosis
  • Digital images can be archived onto compact optical disks or digital tape drives saving tremendously on  storage space and man power  needed for  a traditional  x-ray film library
  • Digital images may be retrieved from  an electronic archive for future  reference

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

End Note

Author Information

Dr. P Shah Navas, Convener, Research Cell,
Kerala State, IMA.  TC 7/171, Kumaran Asan Nagar, Ulloor, MCPO, Trivandrum – 695011.
Phone: 9447169693. Email: drshahnavas@gmail.com

Conflict of Interest: None declared

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