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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 ...
The external capsule is a series of white matter fiber tracts in the brain.These fibers run between the most lateral (toward the side of the head) segment of the lentiform nucleus (more specifically the putamen) and the claustrum.
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 genu is the bend, or flexure in the V of the internal capsule. It is formed by fibers from the corticobulbar tract.The fibers in this region are named the geniculate fibers that carry upper motor neurons from the motor cortex to cranial nerve nuclei that mainly govern muscle motion of the head and face.
A ring-enhancing lesion is an abnormal radiologic sign on MRI or CT scans obtained using radiocontrast.On the image, there is an area of decreased density (see radiodensity) surrounded by a bright rim from concentration of the enhancing contrast dye.
Identification of the dense artery sign is often based on subjective interpretation and false positives may occur. One study aiming to define criteria for the sign determined that measuring Hounsfield units on the CT scan could differentiate between the dense MCA sign associated with ischemic stroke and that caused by false positives. [8]
CT image showing extensive low attenuation in the right hemispheric white matter due to dilated Type 2 perivascular spaces Axial fat-suppressed T2-weighted MRI image in the same patient as above demonstrating extensive dilated Type 2 perivascular spaces in the right hemisphere Perivascular space is depicted in the inset box.
Fogging phenomenon in computerized tomography (CT) scanning of the head is vanishing signs of an infarct on the serial CT imaging in a patient with a recent stroke. [1] It is a reversal of the hypodensity on the CT after an acute ischemic stroke.