Diagnostic Imaging for Physical Therapists: Difference between revisions

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* [[Diagnostic Imaging of the Shoulder]]<sup></sup><sup></sup>
* [[Diagnostic Imaging of the Shoulder]]<sup></sup><sup></sup>
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== Radiograph (X-Ray)  ==
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'''''Radiography''''' is the use of X-rays to view non-uniformly composed material. In the medical field, radiography is used to diagnose or treat patients through the recording of images of the internal structure of the body. These images assess the presence or absence of disease, foreign objects, and structural damage or anomaly. The term x-ray refers to the radiation beam and x-ray particles, not to the film plate itself. X-ray films should be referred to as films, plain films, radiographs, or a plain film study when dialoging within the medical community.<ref name="Biederman">Biederman, R. E., Wilmarth, M. A., &amp; Editor, C. M. D. T. (n.d.). Diagnostic Imaging in Physical Therapy Avoiding the Pitfalls. Diagnostic Imaging.</ref>
'''Potential areas for film and/or processing errors:<ref name="Biederman" />'''
'''Heel effect '''– a source of visual error related to x-ray production, due to the fact that x-rays released by the machine are not uniform. There are two ends to an x-ray machine, a cathode end and anode end. The cathode end releases more photons than the anode end, which results in over-exposure of the film at the cathode end and under-exposure at the anode end. Due to this fact, technicians will position the patient on the table in a manner such that the thickest portion of the body region being studied is placed nearest the cathode end of the tube and the thinner end is placed near the anode end.
'''Artefact''' – An error in the perception of the visual image of the radiograph, usually seen as an abnormal finding or foreign body. Artifacts occur when the cassettes that house the x-ray film plates get exposed to finger prints or small debris.
'''Exposure''' – A measure of the amount of ionising radiation determined by 3 factors: time, x-ray energy, and the quantity of the x-ray photons. Exposure can be manipulated by the technician to highlight structures of interest. Over-penetration will tend to enhance bone visibility, while under-penetration will enhance soft tissue visibility.
'''Movement '''– A blurring in the image as a result of movement by the patient the moment the x-ray exposure is made.
'''Film processing''' – An error that occurs during the processing of the film can result in disturbances in the contrast, detail, or density of the image displayed.
'''Radiodensity''' is a representation of the relative tissue density, based on the appearance of the tone of the tissue (white, gray, or black). The following structures may be found on a medical radiograph (in order of increasing radiodensity):<ref name="Biederman" />
'''Air '''– black appearance, often seen in structures such as the lungs, bowels, trachea<br>'''Fat '''– dark grey appearance, often seen in structures such as thicker adipose tissue <br>'''Muscle, tendon, organ tissue '''– appears “neutral” or mid-grey<br>'''Bone''' – cancellous bone appears as light grey, while cortical bone appears as white<br>'''Contrast media''' - white appearance<br>'''Metal '''– white appearance, often seen in structures such as jewellery, dental fillings, or orthopaedic hardware
Caution to the radiograph viewer/interpreter – There is an inherent error that occurs when a 2-dimensional image is created to depict 3-dimensional structures that are often superimposed on one-another. Due to this fact, radiographic studies of specific body regions often include 3 or more views from different angles.
'''Four principle sources of radiographic error:<ref name="Biederman" />'''
#Enlargement occurs because the x-ray beams exit the machine in an expanding conical pattern (similar to a flashlight beam). As a result, objects placed closer to the beam source appear larger than objects placed further away from the beam source.
#Elongation is produced by the increased beam angle at the periphery of the x-ray beam cone. As a result of the increased beam angle, objects in the periphery of the x-ray beam appear smeared or spread compared to objects in the centre of the beam.
#Foreshortening is the opposite effect of elongation. This occurs when the body region to be studied is placed at an angle to the primary x-ray beam, resulting in the appearance of decreased length.
#Superimposition occurs because anatomic structures are often stacked on one another, forcing the x-ray beam to penetrate multiple structures before arriving at the film plate. Superimposition can create the appearance of increased density of structures, or the appearance of novel structures altogether.


== Computerised Axial Tomography (CT Scan)  ==
== Computerised Axial Tomography (CT Scan)  ==
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#<sup></sup>
<u>'''Indications for CT Scans:'''</u>
 
#Traumatic injuries
#Degenerative conditions, such as stenosis and osteoarthritis when an MRI is contraindicated
#Post-operative conditions
#Neoplastic conditions
#Infectious processes
#Image guidance during injections, biopsy’s and aspirations
#Abnormalities of bony alignment, such as scoliosis
#Processes involving the spinal cord when MRI is contraindicated<ref>College, A. ACR – ASNR – ASSR – SPR PRACTICE GUIDELINE FOR THE PERFORMANCE OF COMPUTED TOMOGRAPHY ( CT ) OF THE SPINE. Diagnostic Imaging, 1-7. 2011</ref><sup></sup>
== Bone Scan  ==
== Bone Scan  ==


Revision as of 07:46, 1 October 2019

Original Editor - Rob Sigler, Michael Kecman and Daniel Alcorn as part of the The Jackson Clinics Residency Project

Top Contributors - Rob Sigler, Admin, Lucinda hampton, Kris Porter, Laura Ritchie, Kim Jackson, Rucha Gadgil, Daniel Alcorn, Naomi O'Reilly, Claire Knott, Robin Tacchetti, 127.0.0.1 and Tony Lowe

Diagnostic Imaging for Body Regions[edit | edit source]

Computerised Axial Tomography (CT Scan)[edit | edit source]

Computed Tomography (CT) is an imaging technique that takes multiple x-rays from different angles and creates cross-sectional images of a body part. Cross-sectional slices are typically 1-3 mm thick, depending upon the type and location of the tissue. CT scans are primarily used for bony pathologies, but can also be used for soft tissue dysfunction. CT scans are not as effective at detecting soft tissue pathology as MRIs because there is not enough differentiation in the x-ray absorption of injured and healthy tissue. Other benefits of CT scans are that they are fast, relatively inexpensive and often a good alternative to MRIs if an MRI is contraindicated.[1]

CT Scan of the Brain
CT Angiogram

Bone Scan[edit | edit source]

Bone scan is an imaging technique that uses a radioactive compound to identify areas of healing within the bone. Bone scans work by drawing blood from the patient and tagging it with a bone seeking radiopharmaceutical. This radioactive compound emits gamma radiation. The blood is then returned to the patient intravenously. As the body begins its metabolic activity at the site of the injury, the blood tagged by the radioactive compound is absorbed at the bone and the gamma radiation at the site of the injury can be detected with an external gamma camera. A bone scan can be beneficial in determining injury to the bone within the first 24-48 hours of injury or when the displacement is too small to be detected by an x-ray or CT scan.[1]

Indications for Bone Scans:

  1. Primary and metastatic bone neoplasms.
  2. Disease progression or response to therapy.
  3. Paget’s disease of bone.
  4. Stress and/or occult fractures.
  5. Trauma – accidental and non-accidental.
  6. Osteomyelitis.
  7. Musculoskeletal inflammation or infection.
  8. Bone viability (grafts, infarcts, osteonecrosis).
  9. Metabolic bone disease.
  10. Arthritides.
  11. Prosthetic joint loosening and infection.
  12. Pain of suspected musculoskeletal etiology.
  13. Myositis ossificans.
  14. Complex regional pain syndrome (CRPS 1). Reflex sympathetic dystrophy.
  15. Abnormal radiographic or laboratory findings.
  16. Distribution of osteoblastic activity prior to administration of therapeutic radio-pharmaceuticals for treating bone pain.[2]

References[edit | edit source]

  1. ↑ 1.0 1.1 Swain J, Bush K. Diagnostic Imaging for Physical Therapists. St. Louis: Saunders Elsevier; 2009
  2. ↑ College A. ACR PRACTICE GUIDELINE FOR THE PERFORMANCE OF ADULT AND PEDIATRIC SKELETAL SCINTIGRAPHY ( BONE SCAN ). North. 2007:1-5.



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