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A CT pulmonary angiogram, in this case showing pulmonary embolism of saddle-type, which becomes more radiolucent than the radiocontrast filled blood surrounding it (but it may be indistinguishable without radiocontrast). Contrast CT, or contrast-enhanced computed tomography (CECT), is X-ray computed tomography (CT) using radiocontrast.
Head CT showing periventricular white matter lesions. Leukoaraiosis is a particular abnormal change in appearance of white matter near the lateral ventricles. It is often seen in aged individuals, but sometimes in young adults. [1] [2] On MRI, leukoaraiosis changes appear as white matter hyperintensities (WMHs) in T2 FLAIR images.
Radiolucency or hypodensity indicates greater passage (greater transradiancy) to X-ray photons [1] and is the analogue of transparency and translucency with visible light. Materials that inhibit the passage of electromagnetic radiation are called radiodense or radiopaque , while those that allow radiation to pass more freely are referred to as ...
On CT scan, benign adenomas typically are of low radiodensity (due to fat content). A radiodensity equal to or below 10 Hounsfield units (HU) is considered diagnostic of an adenoma. [7] An adenoma also shows rapid radiocontrast washout (50% or more of the contrast medium washes out at 10 minutes). If the hormonal evaluation is negative and ...
Non-contrast-enhanced CT scans are the gold standard for diagnosing kidney stone disease. [69] They allow clinicians to estimate the size, volume, and density of stones, helping to guide further treatment; with size being especially important in predicting the time to spontaneous passage of a stone.
The Hounsfield unit (HU) scale is a linear transformation of the original linear attenuation coefficient measurement into one in which the radiodensity of distilled water at standard pressure and temperature is defined as 0 Hounsfield units (HU), while the radiodensity of air at STP is defined as −1000 HU.
The data can be corrected for self-absorption artefacts using an X-ray absorption-contrast CT scan of the same sample. If the solid-state chemistry of the sample is changing during the XRD-CT scan, then other data acquisition approaches can be employed that can improve the temporal resolution of the method, such as the interlaced approach [13] [14]
CT scan (computed tomography) of the brain (without any iodinated contrast), is the initial imaging choice because of its high speed, good accessibility in hospitals, high sensitivity in detecting brain injuries or brain diseases, thus helping to triage patients in emergency department in a timely manner and urgent neurosurgical intervention ...