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28 Cards in this Set
- Front
- Back
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MRI
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MRI (magnetic resonance imaging)
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CT
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CT (computed Axial tomography)
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Scintigraphy
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Scintigraphy (bone scan)
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Image is formed using
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rotating thin beam(s) of ionizing radiation
Images of “slices” are reconstructed by computation |
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CT Indications
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Concussion evaluation
Masses, pneumonia, TB, emphysema, lung disease Trauma Cancer Diverticulitis Pancreatitis Appendicitis Aortic Aneurysm Bowel Obstruction Renal Stones |
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Sensitivity
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80-100 %
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Specificity
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50-80 %
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CT STRENGTHS
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Excellent for evaluation of small osteolytic lesions & nerve roots
Better than MRI when evaluating masses in the abdomen Can combine with angiography to identify aortic issues Cheaper than MRI Fast No issues with implanted metal devices |
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CT WEAKNESS
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Poor soft tissue resolution (MRI better)
Common SE: headaches (10-25%) Radiation Exposure (children are more sensitive to radiation and should be a consideration before ordering) Pregnant women, young children may have reaction to contrast agents Not as good as MRI at evaluating soft tissue swelling or infection of brain Expensive |
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The bottom line
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Gold Standard for calcifications
Method of choice for mass, metastatic and pleural disease Great for locating loose fragments in relationship to overlapping bony anatomy (crush injuries) CT myelogram - to visualize the nerve roots, spinal cord, size & shape of the canal Good for ER b/c it is fast & gives immediate results MRI is becoming more readily available making CT less needed. |
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“MRI” Image is formed by
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Also called “MRI” Image formed by transmitting and receiving radio waves inside a high magnetic field
Image “slices” reconstructed by computation The image formed is related to: ◦Scanner settings ◦Patient’s tissue hydrogen density |
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How MRI works
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A giant, extremely strong magnet that uses magnetic fields and radio waves to produce images of the body.
MRI scan utilizes the body’s 75% water composition. This water contains oxygen & hydrogen molecules. Hydrogen molecules have a natural magnetic spin, the MRI can change the alignment of the atoms' nuclei using the magnetic field & a radio-frequency wave burst. |
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The time is takes for the molecules to regain their natural alignment varies depending :
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on the type of tissue being scanned - thus giving us a computer generated map of the different tissues.
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MRI is good for evaluating
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soft tissues
◦Muscles ◦Nerves ◦Spinal cord ◦Ventricles of brain Good for evaluating stress fractures |
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MRI Indications
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Suspected neoplasm (primary or metastatic)
Radiculopathy Neurologic deficit High-impact trauma Suspected spinal infection Spinal stenosis Back pain in pt with cancer |
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MRI strengths
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Noninvasive
No ionizing radiation Good soft tissue resolution Multiplanar Best for identifying disc changes & evaluating extent of injury |
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MRI Weakness
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Expensive
Time consuming Need pt cooperation (anxiety) Affected by motion Cannot be performed with pacemaker, metallic foreign bodies |
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MRI Contraindications
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Patients who have a heart pacemaker may not have an MRI scan
Patients who have a metallic foreign body (metal sliver) in their eye, or who have an aneurysm clip in their brain, cannot have an MRI scan since the magnetic field may dislodge the metal Patients with severe claustrophobia may not be able to tolerate an MRI scan, Patients who have had metallic devices placed in their back (such as screws) can have an MRI scan, but the resolution of the scan is often severely hampered by the metal device and the spine is not well imaged. |
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MRI BOTTOM LINE
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Gold Standard for disc disease
2% bone marrow changes (x-ray is 40-50%) Inflammatory changes visible: 24 hrs (x-ray is 10-14 days) CT = also shows inflammatory changes within 24 hours MRI for internal trauma |
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CT or MRI
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CT images are tissue density related
◦Brightness and contrast will vary ◦Bone is brighter than fat MRI is not density related ◦Brightness and contrast will also vary ◦Bone is darker than other tissues |
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SCINTIGRAPHY IS
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Pt given radio nucleotides and pt emits gamma radiation
Allow us to visualize specific function about pt’s organs or body system Will appear as a Hot Spot or very bright when there is increased uptake within the tissue (soft or boney) is a functional test, which means it measures an aspect of bone metabolism or bone remodeling, which most other imaging techniques cannot. |
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SCITIGRAPHY ALSO IS
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is a nuclear scanning test to find certain abnormalities in bone that are triggering the bone's attempts to heal.
It is primarily used to help diagnose a number of conditions relating to bones, including: cancer of the bone or cancers that have spread (metastasized) to the bone, locating some sources of bone inflammation (e.g. bone pain such as lower back pain due to a fracture), the diagnosis of fractures that may not be visible in traditional X-ray images. |
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With SCINTIGRAPHY
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The more active the bone turnover, the more radioactive material will be seen.
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Scintigraphy indications
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Metastasis
Arthritides Occult fracture AVN (avascular necrosis) Unexplained bone pain Stress fracture Osteomyelitis (infection) Distribution of osteoblastic activity |
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Scintigraphy contraindications
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Highly sensitive for bone lesions
Good for metastatic lesions Good for identifying site of abnormality |
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Scintigraphy weakness
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Nonspecific
Need plain films for side by side comparison Expensive False negative scans in Multiple Myeloma Not good if pregnant Full bladder will interfere with pelvic bone studies |
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Scintigraphy bottom line
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Good for polyostotic conditions
Bone scan shows AVN in 72 hours (same as MRI), CT is in 45 hrs |
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Thermographic imaging / Thermography
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Infrared thermography, thermal imaging, and thermal video are examples of infrared imaging science. Thermal imaging cameras detect radiation in the infrared range (roughly 9000–14,000 nanometers or 9–14 μm) and produce images of that radiation, called thermograms.
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