signs_Radiology

Michelangelo Merisi da Caravaggio or
Caravaggio (1573(1573)–1610(1610))


Bird-beak sign

Bird-beak sign is used to refer to the tapering of the inferior
oesophagus in achalasia. The same appearance (although it is
difficult to see the similarity) is also referred to as the rat-tail sign.



Bat wing 4th ventricle
Bat wing 4th ventricle sign refers to the morphology of the
fourth ventricle in the Joubert anomaly and related syndromes. The
absence of a vermis with apposed cerebellar hemispheres give the fourth
ventricle an appearance reminiscent of a bat with its wings outstretched.


Molar tooth sign
The molar tooth sign refers to the appearance of the midbrain in which
the elongated superior cerebellar peduncles give the midbrain an
appearance reminiscent of a molar or wisdom tooth.
It was initially described in Joubert syndrome and related disorders
(JSRD) 2, but is now recognised to occur in a number of other
conditions : renal anomalies, hepatic fibrosis and in syndromes with
ocular and digital malformations. 

Butterfly glioma
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A butterfly glioma refers to a high grade astrocytoma, usually a GBM (
WHO grade IV), which crosses the midline via the corpus callosum. Other
white matter commissures are also occasionally involved. The term butterfly
refers to the symmetric wing like extensions across the midline. 
Most frequently butterfly gliomas occur in the frontal lobes, crossing via the
genu of the corpus callosum, however posterior butterflies are also
encountered. 
Like all high grade gliomas the prognosis is dismal, and usually no attempt
at 'curative' resection is made.
Differential diagnoses
primary CNS lymphoma : especially in patients AIDS
cerebral toxoplasmosis : especially in patients AIDS
tumefactive MS
cerebral metastases (rare)
occasionally a leptomeningeal process which fills the quadrigeminal and
ambient cisterns can cause confusion

Honeycombing

Honeycombing refers to the computed tomographic (CT)
manifestation of diffuse pulmonary fibrosis. CT demonstrates
clustered cystic air spaces (between 0.3 - 1.0 cm in diameter),
which are usually subpleural. The walls of the cysts are well-defined
and often thick. Air-space consolidation in the presence of
pulmonary emphysema can mimic this appearance.



Air crescent sign


An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis,
semi-invasive aspergillosis or other processes that cause pulmonary necrosis. It usually heralds
recovery and is the result of increased granulocyte activity.
In angioinvasive fungal infection, the nodules are composed of infected haemorrhagic and infarcted
lung tissue. As the neutrophil count recovers and the patient mounts an immune response, peripheral
reabsorption of necrotic tissue causes the retraction of the infarcted centre and air fills the space in
between. This creates an air crescent within the nodules and is a good prognostic finding because it
marks the recovery phase of the infection. This sign is seen in approximately 50% of patients.
It should not to be confused with the Monod sign 2 which describes the air that surrounds an 
aspergilloma.  Unfortunately, the air around the fungal ball is also crescent shaped and the term
air crescent sign is often used interchangeably in that instance. Opinion as to the validity of this latter
use is controversial, but probably not worth losing too much sleep over.
Causes include 5:
aspergilloma : aka Monod sign
angioinvasive aspergillosis

hydatid cyst
other rare causes
pulmonary tuberculosis
Rasmussen aneurysm in a tuberculous cavity
pulmonary abscess
bronchogenic carcinoma
pulmonary haematoma
Pneumocystis carinii pneumonia (PCP)


Monod sign

Monod sign simply describes air that surrounds a mycetoma (most
commonly an aspergilloma) in a pre existing pulmonary cavity 1-3.
It should not be confused with the air crescent sign which is seen in
recovering angioinvasive aspergillosis 4. The air crescent sign heralds
improvement in the condition.
In practice it is likely that the term Monod sign will receive blank stares.
The air around the mycetoma is often crescent shaped and hence, the
term air crescent sign is used interchangeably by many to refer to both
pathological processes.


Coffee-bean sign
The coffee-bean sign (also know as kidney bean sign and bent
inner tube sign 4 ) is a sign on an abdominal plain film of a sigmoid
volvulus although some authors have also used the term to refer to
closed loop small bowel obstructions.
This thick 'inner wall' represents the double wall thickness of
opposed loops of bowel, with thinner outer walls due single

thickness.


Miliary opacities


The term miliary opacities refers to innumerable small 1 - 4mm diameter nodules scattered widely throughout the lungs. 
It is useful to divide patients with pulmonary miliary opacities into those who are febrile and those who are not. Additionally
some miliary opacities are very dense, and these have a narrower differential (see multiple small hyperdense
pulmonary nodules). 
Afebrile
infection
tuberculosis (often febrile)
fungal (often febrile) Immunocompromised or elderly patients are most likely to be afebrile.
metastases
thyroid carcinoma
renal cell carcinoma
breast carcinoma
malignant melanoma
pancreatic neoplasms
osteosarcoma
trophoblastic disease
sarcoidosis
pneumoconioses
silicosis
coal workers pneumoconiosis
hypersensitivity pneumonitis
Langerhans cell histiocytosis (LCH)
multifocal micronodular pneumocyte hyperplasia (MMPH)
pulmonary alveolar proteinosis : small acinar opacities can mimic a miliary pattern 6

Febrile
Infections
tuberculosis
fungal
viral pneumonitis
nocardosis
salmonella
hypersensitivity pneumonitis (mild fever if any)
Etymology
The term miliary stems from millet seed, a term used to describe a group of small-seeded species of cereal crops or grains,
widely grown around the world for foodand fodder


onion skin periosteal reaction


Popcorn calcification
Popcorn calcification refers to the amorphous calcifications often with rings
and arcs (see rings and arcs calcification) that resemble kernels of popped
corn. This type of calcification is seen in:
chondroid lesions (e.g enchondroma, chondrosarcoma)
fibrous dysplasia
pulmonary hamartomas
degenerating fibroadenomas of the breast


Cotton wool appearance of bone
The cotton wool appearance is a plain film sign of Paget's disease  and
results from thickened, disorganized trabeculae which lead to areas of
sclerosis in a previously lucent area of bone - typically the skull. These

sclerotic patches are poorly defined and fluffy.
Other Paget's disease related signs
blade of grass sign
jigsaw pattern bone or mosaic pattern bone
picture frame vertebra
Tam O'Shanter sign
banana fracture


Linguine sign

After implantation of a silicone or saline breast implant, a
fibrous capsule (scar) forms around the implant shell. In an
intracapsular rupture the contents of the implant are contained
by the fibrous scar while the shell appears as a group of wavy
lines. This has been termed the "Linguine Sign" and has been
most commonly described with MR imaging. Here, the same
findings are seen on CT imaging in a patient with bilateral
ruptured saline implants.


Endometrioma


An endometrioma (also known as a chocolate cyst) is a
localised form of endometriosis (usually within the ovary). It
contains dark degenerated blood products following
repeated cyclical haemorrhage.
The cysts may be up to 20cm in size although they are
usually smaller (2 - 5cm).

Radiographic features
Ultrasound
There is acoustic enhancement with diffuse homogenous
low-level internal echoes as a result of the haemorrhagic
debris. This appearance occurs in 95% of cases and is
considered the classic finding on ultrasound examination.
Anechoic cysts may occurs, but they are rare.
Differential diagnoses
haemorrhage into an ovarian cyst
dermoid
cystic neoplasm
tuboovarian abscess


Cottage loaf sign

A cottage loaf sign occurs as a result of a right-sided
diaphragmatic rupture occurs with partial herniation of the liver
through the diaphragmatic defect.The herniated component is
separated by a waist at the diaphragm from the larger intraabdominal component. This shape is reminiscent of a cottage
loaf, a particular shape of bread in which larger and smaller
roughly spherical balls are squashed together, forming a
cottage shape