CT Scan
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Introduction
In Computed Tomography, a source of X-rays is rotated around a plane of the body, being picked up by a series of detectors.
As a CT uses X rays, the greater the atomic number, the greater a molecule's ability to stop the CT. Bone is white, while air is black.
Uses
CT and the Brain
While imaging the brain, from white to black, other tissues include:
- extravascular blood
- an enhanced tumour
- fat
- brain
- cereberospinal fluid
CT can be used to detect:
- acute and subacute hemorrhages
- skull trauma
- shows scalp, skull, brain
- good for non-specifici neurological compliants
- useful for assessment of acute trauma, stroke, intracranial damage
- rules out and follows space-occupying lesions
contrast material
- useful for highlighting areas that blood pools, ie tumour
- don't use if you're looking for fresh blood, as it will obscure
- nephrotoxic, and some risk of allergic reaction
risks
- significant radiation exposure
- risks associated with contrast enhancement
- ' a single CT scan on a newborn girl has a 1:800 chance of causing a fatal cancer' - Nature editorial
Computed tomography (CT) is very useful in respirology becuase it avoid shadows. It is created by measuring attenuation coefficients of a 1cm thick axial beam in many projections.
Important uses of CT include:
- evaluation of pulmonary nodules/masses
- distinguishing pleural thickening from pleural fluid
- estimation the size of the heart
- identifying pericardial fluid or thickening
- identifying patterns of involvement in interstital lung disease
- detecting and defining cavities
- identifying intracavitary processes such as mycetomas or fluid
- quantifying the extent and distribution of COPD
- detecting and measuring mediastinal adenopathy or masses
- evaluating proximal clots in pulmonary arteries
Spiral CT scans are useful in detecting acute PE.
Risks
Contrast Nephro
2500 kids die yearly in North America from CT
amount from one scan equal to outskirts of Hiroshima
Mechanism of Action
Additional Resources
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