A helpful mnemonic to recall the causes of T2 hyperintense basal ganglia is:
N: neurodegenerative conditions
For a more detailed differential please see T2 hyperintense basal ganglia article.
The commonest causes of basal ganglia T2 hypointensity can be recalled using the following mnemonic:
Ch: childhood hypoxia
O: old age
M: multiple sclerosis
P: Parkinson's disease, more in globus pallidus
T2 mapping is a magnetic resonance imaging technique used to calculate the T2 times of a certain tissue and display them voxel-vice on a parametric map. It has been used for tissue characterization of the myocardium 1-5 and has been investigated for cartilage 6,7 and other tissues 4.
The T2 tim...
T2* mapping is a magnetic resonance imaging technique used to calculate the T2* time of tissue and display them voxel-vice on a parametric map. It is used for myocardial tissue characterization 1-4 and has been investigated for other tissues 5,6.
T2* mapping is usually based on gra...
T2 relaxation, also known as spin-spin relaxation or transverse relaxation, refers to the progressive dephasing of spinning dipoles resulting in decay in the magnetization in the transverse plane (Mxy). Following a radiofrequency pulse, this form of relaxation occurs with the time constant T2. T...
T2* decay refers to an exponential decrease in Mxy (i.e. signal strength) following the initial excitation pulse as a function of time constant T2*. A picture of the signal or free induction decay (FID) is shown on the right, occurring immediately after a 90o RF excitation pulse in a liquid pha...
T2 shine-through refers to high signal on DWI images that is not due to restricted diffusion, but rather to high T2 signal which 'shines through' to the DWI image. T2 shine through occurs because of long T2 decay time in some normal tissue.
This is most often seen with subacute infarctions due ...
T2 washout is a phenomenon encountered on diffusion weighted imaging (DWI) which results in DWI images (e.g. b = 1000) appearing normal despite abnormal ADC maps.
For the phenomenon to occur a particular combination of ADC and T2 signal intensity is required.
increased T2 signal
T2 weighted image (T2WI) is one of the basic pulse sequences in MRI. The sequence weighting highlights differences in the T2 relaxation time of tissues.
repetition time (TR): long
echo time (TE): long
flip angle: less important than with T1 weighting
The Tabar 5-tier grading system is used to classify mammographic lesions. This should not be confused with the Tabar classification of parenchymal patterns in breast imaging. It is a separate but translatable system to the BI-RADS classification system (please note that Tabar grade 3 ≠ BI-RADS 3...
Tabes dorsalis is a form of tertiary late neurosyphilis in which there is demyelination of the posterior columns of the spinal cord.
For a general discussion, and for links to other system specific manifestations, please refer to the article on syphilis.
Tachon syndrome is a rare systemic side effect of epidural or intra-articular corticosteroid injections.
Minutes after injection, patients may complain of 1:
acute low back pain
Treatment and prognosi...
Tachycardia induced cardiomyopathy (TIC) (or tachycardiomyopathy) is considered a reversible form of acquired cardiomyopathy where there is impaired left ventricular systolic dysfunction precipitated by a tachycardia or a tachyarrhythmia.
Typically there is an impairment left ventricular systol...
The tadpole sign, also known as the lollipop sign, refers to a characteristic morphology of post-traumatic bridging vein thrombosis with a rounded "head" and a tapering "tail". The finding demonstrates a high specificity for abusive head trauma, a sub-type of non-accidental injury, and should wa...
The taeniae coli are the three outer muscular bands of the colon. They sit on top of the inner circumferential layer and result in the classical appearance of the colon: the haustral markings are interrupted unlike the valvulae conniventes within the small bowel.
Tags on Radiopaedia.org allow authors to specify a little more about what the article is about and allows articles to be more completely related to articles that are similar.
Additionally, there are a number of 'official tags'.
cases: [articles only]
cases needed to illustrate art...
Tailgut duplication cysts, also known as retrorectal cystic hamartomas, are rare congenital lesions that are thought to arise from vestiges of the embryonic hindgut.
There is a recognized strong female predilection. While it can present at any age, presentation is usually at arou...
The tail sign has been described as being specific to Dandy-Walker malformation in fetal MRI.1
It is described as a linear T2 hypointensity in the inferior part of the vermis. Histologically, it corresponds to a thickness of the fourth ventricle roof that appears raised and dysplastic.1
Takayasu arteritis (TA), also known as idiopathic medial aortopathy or pulseless disease, is a granulomatous large vessel vasculitis that predominantly affects the aorta and its major branches. It may also affect the pulmonary arteries. The exact cause is not well known but the pathology is thou...
The Takeuchi procedure refers to a direct anastomosis of the anomalous left coronary artery from the pulmonary artery directly to the aorta was described in the 1970s and currently remains the procedure of choice.
An intrapulmonary aortocoronary tunnel or baffle was performed by Takeuchi prior ...
Takotsubo cardiomyopathy (TC) (a.k.a. apical ballooning syndrome) is a condition characterized by transient regional abnormal cardiac wall motion, not confined to a single coronary arterial territory. It has been described predominantly in postmenopausal women, often following exposure to sudden...
The talar beak sign is seen in cases of tarsal coalition, and refers to a superior projection of the distal aspect of the talus. It is most frequently encountered in talocalcaneal coalition. It is thought to result from abnormal biomechanic stresses at the talonavicular joint.
Talar body fractures are a subtype of talar fracture, subdivided into:
talar dome osteochondral fracture
posterior talar process fracture
lateral talar process fracture
The talar declination angle is drawn on the weightbearing lateral foot radiograph between the mid-talar axis and the supporting surface. It should usually measure approximately 21°.
If the first metatarsal axis is steep, the mid-talar axis approaches the horizontal and is projected above the fi...
There are many types of talar dislocation given its multiple articulations:
total talar dislocation
Talar fractures are an uncommon injury, accounting for <5% of all foot fractures. Recognition of the unique talar anatomy is important for correct diagnosis.
talar head fractures
talar neck fractures
talar body fractures
talar dome osteochondral fracture
Talar head fractures most commonly result from a compressive force with a plantar flexed foot.
Talar head fractures almost always involve the talonavicular joint, and associated dislocation/subluxation is common.
Two types of talar fractures are described 3:
compression fracture, o...
Talar neck fractures extend through the thinnest cross-sectional portion of the talus, just proximal to the talar head. They represent one of the most common types of talus fracture (~30-50%), along with chip and avulsion fractures of the talus (~40-49%). These fractures are commonly associated ...
Talc-induced lung disease comprises of a group of pathologies that can occur related to exposure to the mineral talc (hydrated magnesium silicate).
Four types of pulmonary disease secondary to talc exposure have been defined, these are:
talcosilicosis - associated with occupational exposure
Talcosis is a type of pneumoconiosis and can be prevalent in intravenous drug users. It is one of the four recognized types of talc-induced lung disease.
Talc (magnesium silicate) is used in the preparation of tablets intended for oral use, where it acts as a 'filler' and lubricant. ...
Talc pleurodesis is one of the chemical methods of pleurodesis which is a procedure performed to prevent recurrence of a pneumothorax or recurrent pleural effusion in benign or malignant conditions. It involves achieving an area of adhesion between the parietal and visceral layers of the pleura....
Talc (magnesium trisilicate) pulmonary embolism is a rare cause of non thrombotic pulmonary embolism. It tends to be more prevalent in patients with narcotic abuse.
Most patients are asymptomatic although dyspnea and persistent cough occur with severe talc exposure. Clini...
The talocalcaneal angle, also known as the kite angle, refers to the angle between lines drawn down the axis of the talus and calcaneus measured on a weight-bearing DP foot radiograph. This angle varies depending on the position of the calcaneus under the talus and the stiffness of the ligaments...
Talocalcaneal coalition is one of the two most common sub-types of tarsal coalition, the other being calcaneonavicular coalition. It accounts for 45% of all tarsal coalitions, and although all three facets of the talocalcaneal joint can be involved, the middle facet is most commonly involved.
The talocalcaneal joint, also called the clinical subtalar joint, is an important and complex joint in the hindfoot that allows articulation of the talus and calcaneus.
It comprises three articulations between talus and calcaneus 1:
anterior: head of talus with anterior facet o...
Talonavicular coalition is one of the less common subtypes of tarsal coalition, the most commons being talocalcaneal coalition and calcaneonavicular coalition. As with other forms of coalition it can be osseous, cartilaginous or fibrous.
Uni-or bilateral. Most patients ar...
The talonavicular coverage angle reflects the degree of, if any, talonavicular lateral subluxation. On DP weight-bearing foot radiographs, it is the angle between:
articular surface of the talar head
articular surface of the proximal navicular
Interpreting the talonavicular coverage angle:
Talonavicular dislocations are a rare injury, and is caused by forced extreme abduction or adduction of the forefoot. They are often associated with calcaneocuboid dislocation (often transient) and calcaneal fractures (and are then called transcalcaneal talonavicular dislocations).
The talonavicular joint is an important part of the Chopart joint between the talus of the hindfoot and the navicular of the midfoot.
The talonavicular joint primarily consists of the articulation between the head of the talus and the concavity produced by the posterior aspect of...
The talus is a tarsal bone in the hindfoot that articulates with the tibia, fibula, calcaneus, and navicular bones. It has no muscular attachments and around 60% of its surface is covered by articular cartilage.
The talus has been described as having three main components: head,...
Tamm-Horsfall proteins, also known as uromodulin, may be a cause of echogenic renal pyramids in a neonate.
Tamm-Horsfall proteins are physiologically excreted by the renal tubular epithelium. They are most often encountered on neonatal renal ultrasound, where the concentrated proteins in the re...
The "tam o' shanter" is a Scottish hat, named after the character in Robert Burns' 1 poem of the same name. The appearances of advanced Paget disease of the skull are similar in appearance to the hat.
Paget involvement of the skull, with widening of the diploic space and an overall enlargement...
The oncological agent tamoxifen has pro-oestrogenic changes on the endometrium resulting in abnormal growth with an increased prevalence of:
endometrial polyps: occurs in ~8-36% of women in treated 8
endometrial hyperplasia: occurs in ~1-20% of women treated ref
cystic endometrial atrophy
Tamoxifen is an important anti-estrogen agent used for the treatment of hormone receptor-positive breast cancer and it may induce reversible hepatic steatosis. This is usually transient and may occasionally be associated with hepatic dysfunction. It only rarely leads to cirrhosis 1.
A tangential calcium sign is a sign seen with an aortic aneurysm rupture. The calcified intimal rim is discontinuous and is seen to tangentially point away from the aneurysmal lumen. This sign is seen at the point of breach. There is associated retroperitoneal leakage.
Tangential views are useful to differentiate intracutaneous radiopaque particles in a tattoo from intraparenchymal microcalcifications.
Mammographic findings close to the skin such as masses, microcalcifications, skin dimpling or shaded areas always pose a problem of differential diagnosis.
The tangent sign is useful in helping to quantify supraspinatus muscle belly fatty atrophy with a positive sign implicated with a poorer outcome after supraspinatus tendon tear repair.
On a sagittal oblique plane, a line is drawn between the upper surface of the scapular spine and the upper sur...
Breast development occurs in two phases, one during fetal life and the second during puberty. In fetal life a rudimentary organ with simple ducts develop under maternal stimulus. During puberty, further complex branching of ducts and glandular tissue forms which is divided into five stages.
The Tanner-Whitehouse (TW) method is a way of assessing the bone age of children. There are several variations of this method, but all use a DP radiograph of the left hand and wrist to assess the relative maturity of the bones of the patient.
The TW2 (Tanner-Whitehouse 2) methods 1:
Tanycytes are one of the three types of ependymal cells, themselves a type of glial cell. They are found lining the floor of the third ventricle overlying the median eminence of the hypothalamus 1.
It is believed that these specialized cells are involved in the feedback mechanisms on the ante...
Tanycytic ependymomas are histological variants of ependymomas, usually found in the spinal cord 1. Their name reflects the morphological similarlity of these tumor cells to the tanycytes. They do not arise from tanycytes which are located primarily in the floor of the third ventricle.
Tardus parvus refers to a pattern of Doppler ultrasound spectral waveform resulting from arterial stenosis. The phenomenon is observed downstream to the site of stenosis, and is due to reduced magnitude of blood flow through the narrowed vessel during ventricular systole 7.
This characteristic ...
The target sign of choledocholithiasis is a finding seen on contrast-enhanced CT and comprises:
central density within the bile duct: stone
surrounding low density: bile or mucosa
There are many bull's eye signs, also referred to as target signs:
island of red bone marrow with central yellow marrow on MRI
peripheral plexiform neurofibromas on MRI
intussusception: see target sign of intussusception
choledocholithiasis: see target sign of choledocholithiasis
The target sign of intestinal intussusception, also known as the doughnut sign or bull's eye sign.
The appearance is generated by concentric alternating echogenic and hypoechoic bands. The echogenic bands are formed by mucosa and muscularis whereas the submucosa is responsible fo the hypoechoi...
The target sign of peripheral nerve sheath tumor (PNST) is a lesional pattern of T2 signal on MRI consisting of a central area of low intensity surrounded by a T2 hyperintense rim. It is most commonly associated with localized neurofibroma, having been shown to correspond histopathologically wit...
The target sign of pyloric stenosis is a sign seen due to hypertrophied hypoechoic muscle surrounding echogenic mucosa, seen in pyloric stenosis. This is likened to that of a target.
antral nipple sign
cervix sign of pyloric stenosis
shoulder sign of pyloric stenosis
The target sign of tuberculosis refers to the bull's eye appearance of some parenchymal tuberculomas involving the brain (see: CNS tuberculosis) and solid abdominal organs (see: hepatic and splenic tuberculosis) on cross-sectional imaging.
hypoechoic nodules ...
Tarlov cysts, also called perineural cysts, are CSF-filled dilatations of the nerve root sheath at the dorsal root ganglion (posterior nerve root sheath). These are type II spinal meningeal cysts that are, by definition, extradural but contain neural tissue.
Most Tarlov cysts are asymptomatic, ...
The tarsal bones are the seven bones of the foot excluding the metatarsals and phalanges. They are collectively known as the tarsus. The seven bones are:
There are several mnemonics for the tarsals.
Mnemonics of the tarsal bone are numerous and useful for memorizing the order and location of tarsal bones. They usually describe the position of the tarsal bones from superior to inferior, medial to lateral in a right foot:
The Cab in New Mexico Is Land Cruiser
The Cure of Nemaline Myopathy I...
Tarsal coalition describes the complete or partial union between two or more bones in the midfoot and hindfoot. Tarsal coalition refers to developmental fusion rather than fusion that is acquired secondary to conditions such as rheumatoid arthritis, trauma or post-surgical.
Tarsal fractures are fractures of the tarsal bones of the foot, which are further divided by anatomic site:
calcaneal fracture (most common)
calcaneal tuberosity avulsion fracture
talar head fracture
talar neck fracture
lateral talar (sno...
The tarsal plates of the eye are formed by dense fibrous tissue representing thickened extensions of the orbital septum, molded to the curvature of the eyeball. Each eye has a superior tarsal plate and an inferior tarsal plate.
The plates anchor the roots of the eyelashes and contain tarsal (M...
The tarsal sinus (or sinus tarsi) is a cylindrical cavity located between the talus and calcaneus on the lateral aspect of the foot. MRI is the investigation of choice for evaluating the tarsal sinus structures.
The tarsal sinus is situated on the lateral side of the foot; distal...
The tarsal tunnel is a fibro-osseous canal found in the medial aspect of the ankle.
roof: flexor retinaculum
from the tip of the medial malleolus to the medial calcaneal process and plantar aponeurosis
floor: medial surfaces of the tibia, talus and calcaneus 1, 2
Tarsal tunnel syndrome refers to an entrapment neuropathy of the tibial nerve or of its branches within the tarsal tunnel. This condition is analogous to carpal tunnel syndrome.
The most common symptoms are pain and paresthesia in the toes, sole, or heel and the main find...
The tattoo sign is a feature given to describe dermal calcifications seen on mammography 1. The basis of this sign is that dermal calcifications maintain fixed relationships to one another that are reproducible with similar projections at different times. This is in contrast to intramammary calc...
Tauopathies are a heterogeneous group of neurodegenerative diseases characterized by abnormal metabolism of misfolded τ (tau) proteins leading to intracellular accumulation and formation of neurofibrillary tangles (NFT). These neurofibrillary tangles are deposited in the cytosol of neurons and g...
The tau sign represents the appearance of a persistent primitive trigeminal artery on the sagittal plane of an angiogram or on sagittal MRI images. It resembles the Greek letter τ, pronounced 'tau', and is equivalent to the modern day 'T' in the Latin alphabet.
The persistent trigeminal artery ...
Taussig-Bing anomaly is a rare congenital heart malformation and is one of the variants of double outlet right ventricle. It consists of transposition of the aorta to the right ventricle and malposition of the pulmonary artery with subpulmonary ventricular septal defect.
History and etymology
Taylor dysplasia is a type of focal cortical dysplasia and a common cause of refractory epilepsy. Under both the Palmini classification and the more recent Blumcke classification of focal cortical dysplasia, Taylor dysplasia is classified as type II.
For further discussion of the radiographic ...
Tay-Sachs disease is a hereditary neurodegenerative disorder resulting from excess storage of GM2 ganglioside within the lysosomes of cells.
The incidence of the disease is estimated to be 1 in 3,600 in Ashkenazi Jews with a carrier frequency of 1 in 30 and 1 in 360,000 in other ...
Tc-99m DMSA (2,3 dimercaptosuccinic acid) is a technetium radiopharmaceutical used in renal imaging to evaluate renal structure and morphology, particularly in pediatric imaging for detection of scarring and pyelonephritis. DMSA is an ideal agent for assessment of the renal cortex as it binds to...
Tc-99m DTPA (diethylene-triamine-pentaacetate) is one of the technetium radiopharmaceuticals used in renal imaging and primarily used to measure the glomerular filtration rate (GFR).
photon energy: 140 KeV
physical half-life: 6 hours
biological half-life: 2.5 hours
Tc-99m DTPA (diethylenetriamine-pentaacetic acid) (aerosol) is one of the technetium agents and is used in VQ imaging.
photon energy: 140 KeV
physical half life: 6 hours
biological half life: 1 hour
normal distribution: lungs
aerosol deposited in bronhoal...
Tc-99m HMPAO (hexamethylpropyleneamine oxime) labeled WBC is one of the technetium radiopharmaceuticals used in WBC imaging.
There are three potential radiochemical impurities in the 99mTc-HMPAO: a hydrophilic secondary complex, the free pertechnetate and the reduced 99mTc-hydrolyzate. 1The min...
Tc99m IDA (iminodiacetic acid) analogs are hepatobiliary agents in nuclear medicine, used in cholescintigraphy.
Tc99m-DISIDA: diisopropyl IDA, aka Hepatolite
Tc99m-Mebrofenin: trimethyl bromo IDA, aka Choletec
Tc99m-PIPIDA: paraisopropyl iminodiacetic acid
The use of IDA alon...
Tc-99m labeled RBC is one of the technetium radiopharmaceuticals used in the assessment of GI bleeding.
photon energy: 140 KeV
physical half-life: 6 hours
normal distribution: heart, vessels, spleen
threshold for detection is 0.0...
Tc-99m MAA (macroaggregated albumin) is one of the technetium radiopharmaceuticals used in lung perfusion imaging.
photon energy: 140 KeV
physical half life: 6 hours
biological half life: 2-3 hours
normal distribution: lungs, liver, spleen, kidneys
Tc-99m MAG3 (mercaptoacetyltriglycine) is one of the technetium radiopharmaceuticals used in renal imaging. Due to favourable energy and dosimetric characteristics, MAG3 radiolabeled with technetium has replaced the iodide-131 Hippuran for the study of renal function (tubular secretion physiolog...
Tc-99m pertechnetate (Na+ 99mTc O4-) is one of the technetium radiopharmaceuticals used in imaging of thyroid, colon, bladder and stomach.
Technetium (99mTc) has eight oxidation states 6, from -1 to +7; specifically, the oxidation state of technetium in the pertechnetate anion (99mTcO4-) is +7....
Tc-99m sestamibi (sestamibi is a shortening of sesta-methoxyisobutylisonitrile) is one of the technetium radiopharmaceuticals.
photon energy: 140 KeV
physical half-life: 6 hours
normal distribution: thyroid, parathyroid, heart (myocardium)
Technetium-99m sulfur colloid is one of the technetium radiopharmaceuticals.
photon energy: 140 keV
physical half-life: 6 hours
bone marrow: 5%
target organ: liver, spleen
T-cell prolymphocytic leukemia (T-PLL) is a rare and unusual hematological malignancy.
It represents around 2% of all mature lymphocytic leukaemias in adults over the age of 30 1. It usually affects older adults with an average age at presentation being around 65 years. There may ...
The TDP-43 proteinopathies are a set of neurodegenerative disorders characterized pathologically by cytoplasmic inclusions composed of TDP-43. The pathology has been implicated in three major diseases:
amyotrophic lateral sclerosis (vast majority of cases)
frontotemporal lobar degeneration (sl...
A teardrop or teardrop sign is found in several regions of the body:
teardrop sign (ankle)
teardrop sign (intracapsular breast implant rupture)
teardrop sign (superior mesenteric vein)
extension teardrop fracture of the cervical spine
flexion teardrop fracture of the cervical spine
The ankle teardrop sign is one of the radiological signs of an ankle joint effusion. It represents the presence of excess fluid in the inferior part of the anterior compartment of the ankle.
The teardrop sign indicates an uncollapsed intracapsular breast implant rupture and is seen as a small focal invagination of the implant shell caused by a minimal concealed leak of droplets of silicone outside the shell where the two membranes contact each other. It is best appreciated by MRI.
The teardrop sign of the superior mesenteric vein is one of the important signs in the local staging of pancreatic adenocarcinoma. Its importance lies in its diagnostic, as well as prognostic, significance. This sign is used in assessing the resectability of pancreatic cancer.
Technetium 99m-methyl diphosphonate (99mTc MDP) is a radiotracer used in nuclear medicine especially for bone scans. Any disease process which results in extracellular fluid expansion will lead to accumulation of this tracer.
photon energy: 140 keV
physical half life: 6 h...
Technetium agents based on the technetium-99m (Tc-99m) radioisotope are frequently used agents in medical imaging. A radiopharmaceutical labeled with Tc-99m constitutes a coordination complex in which ligands bond to a central atom of Tc-99m by coordinate covalent bonds 4 .
The radioactive tech...
Masking is very important when viewing mammograms, especially with high-density breasts. It helps the adaptation of the eye to the luminance of the mammograms on the viewbox.
The technique of masking allows the comparative study of small areas of both breasts and is a featur...