Halo sign
Encyclopedia
In radiology
, the halo sign is a finding on ultrasound
that suggests the diagnosis of temporal arteritis
. The standard diagnostic test for temporal arteritis is biopsy
; however, ultrasound
and MRI show promise for replacing it.
The halo sign of temporal arteritis should not be confused with Deuel's halo sign, which is a sign of fetal
death.
The halo sign is also understood as a region of ground-glass attenuation surrounding a pulmonary nodule on an X-ray computed tomography (CT scan) of the chest. It can be associated with hemorrhagic nodules
, tumor
s, or inflammatory
processes, but is most commonly known as an early radiographic sign of invasive pulmonary infection by the fungus species Aspergillus
.
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...
, the halo sign is a finding on ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
that suggests the diagnosis of temporal arteritis
Temporal arteritis
Giant-cell arteritis or Horton disease is an inflammatory disease of blood vessels most commonly involving large and medium arteries of the head...
. The standard diagnostic test for temporal arteritis is biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
; however, ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
and MRI show promise for replacing it.
The halo sign of temporal arteritis should not be confused with Deuel's halo sign, which is a sign of fetal
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
death.
The halo sign is also understood as a region of ground-glass attenuation surrounding a pulmonary nodule on an X-ray computed tomography (CT scan) of the chest. It can be associated with hemorrhagic nodules
Nodule (medicine)
For use of the term nodule in dermatology, see Nodule In medicine, a nodule refers to a relatively hard, roughly spherical abnormal structure....
, tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s, or inflammatory
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
processes, but is most commonly known as an early radiographic sign of invasive pulmonary infection by the fungus species Aspergillus
Aspergillus
Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...
.