Tc-99m pertechnetate is one of the technetium radiopharmaceuticals used in imaging of thyroid, colon, bladder and stomach.
photon energy: 140 keV
biological half-life: 6 hours
normal distribution: stomach, thyroid, salivary glands, (testicles)
Tc-99m sestamibi is one of the technetium radiopharmaceuticals.
photon energy: 140 KeV
physical half life: 6 hours
normal distribution: thyroid, parathyroid, heart
target organ: colon, kidneys, bladder, gallbladder
Uses, doses and timings
Teeth can be both primary and secondary, with the eruption of permanent teeth occurring over a long period between the ages of 6 and 24.
There are twenty deciduous (primary) teeth in young children, with ten per jaw and five in each quadrant, which consist of (distal to mesial):...
Telecanthus represents increased intercanthal distance. It is often used interchangeably with hypertelorism, referring to increased distance between the eye.
Causes and associations
trauma: naso-orbito-ethmoidal (NOE) fractures
sinus and orbital tumours
The temporal bone is situated on the sides and the base of the cranium and lateral to the temporal lobe of the cerebrum. The temporal bone is one of the most important calvarial and skull base bones. The temporal bone is very complex and consists of five parts:
A helpful mnemonic for remembering the complications of temporal bone fractures that may require early intervention is:
C: carotid artery injury
L: leakage of CSF
O: other intracranial complications, e.g. hematoma
N: nerve injury leading to complete facial paralysis
Temporal bone fractures are usually a sequela of blunt head injury, generally from severe trauma. Associated intracranial injuries, such as extra-axial haemorrhage, shear (or diffuse axonal) injury, and cerebral contusion are common. Early identification of temporal bone trauma is essential to m...
The temporal fossa is located in the temporal region and communicates inferiorly with infratemporal fossa deep to the zygomatic arch.
The temporal fossa is bounded by a few anatomical landmarks, anteriorly the frontal process of the zygomatic bone, superiorly and posteriorly the...
The temporalis muscle is one of the muscles of mastication. It is responsible for both closing the mouth and retraction (posterior fibres).
origin: temporal fossa between the infratemporal crest and inferior temporal line
insertion: coronoid process and ramus of mandible
The temporomandibular joint (TMJ) is an atypical synovial joint located between the condylar process of the mandible and the mandibular fossa and articular eminence of the temporal bone. It is divided into superior discotemporal space and inferior discomandibular space by the TMJ disc (or menisc...
The axiolateral temporomandibular view allows for visualisation of the articular tubercle, mandibular condyle and fossa and is thus useful to identify structural changes and displaced fractures, as well as assess excursion and joint spaces.
Clinical indications include trauma, the presence of ...
The temporomandibular joint (TMJ) disc (or meniscus) is made of fibrocartilage and divides the joint into two compartments.
The disc is composed of fibrocartilage, with crimped collagen, thought to better absorb impacts. It has a biconcave shape with a thicker periphery attached...
Temporomandibular joint dislocation represents the condyle of the mandible being abnormally displaced, with a loss of the normal articulation with the glenoid fossa.
Dislocations of the temporomandibular joint (TMJ) are common and occur in as many as 7% of the entire population, a...
Temporomandibular joint (TMJ) dysfunction is characterised by an abnormal relationship between the disc and the adjacent articular surfaces (condyle below with mandibular fossa and articular eminence above).
TMJ dysfunction is far more common in women (F:M 8:1).
Temporomandibular joint (TMJ) effusions are unusual in asymptomatic patients, and thus should trigger a careful search for underlying pathology. It usually precedes osteoarthritis of the TMJ. Effusions are seen in:
rheumatoid arthritis (RA)
Temporomandibular joint (TMJ) inflammation may occur as a result of an inflammatory arthropathy or secondary to TMJ dysfunction. Since the TMJ is a synovial joint, it is susceptible to inflammatory arthropathies that affect other joints.
rheumatoid arthritis (RA) : is by far the most common
Temporomandibular joint (TMJ) pathology encompasses three main entities:
temporomandibular joint dysfunction: relating to abnormal TMJ disc relationship to condyle and temporal bone, which can lead to osteoarthritis.
temporomandibular joint inflammation
temporomandibular joint trauma
The temporomandibular joint (TMJ) can be affected by trauma in a number of ways:
condylar process fractures
temporomandibular joint dislocation
fracture of the mandibular fossa
The temporozygomatic suture (or zygomaticotemporal suture) is between the zygomatic process of the temporal bone and the temporal process of the zygomatic bone.
It can mimic a zygoma fracture.
The tendinous ring, also known as the annulus of Zinn, is the common origin of the four rectus muscles (extraocular muscles).
The tendinous ring straddles the superior orbital fissure and through it (from superior to inferior) pass:
superior division of the oculomotor nerve (CN III)
The Tenon capsule, also known as fascia bulbi or bulbar sheath, functions as an extraocular muscle pulley. It also provides a socket which separates the globe from the surrounding fat and allows free movement. It merges posteriorly with the dural sheath of the optic nerve and extends anteriorly ...
The tensor tympani is a short muscle in the middle ear that arises from the superior surface of the cartilaginous part of the Eustachian tube, the greater wing of the sphenoid, and the petrous part of the temporal bone. It passes across the tympanic cavity and inserts into the upper end of the h...
The tensor veli palatini is one of the 5 paired muscles of the soft palate. It is triangular in shape and it's tendon wraps around the pulley of pterygoid hamulus to alter the shape of the soft palate.
origin: it has 3 sites of origin:
scaphoid fossa of the medial pterygoid plate
The tentorial angle is measured between a line connecting the nasion with the tuberculum sellae and the the angle of the straight sinus. Normally it should measure between 27° and 52°.
Abnormalities of the posterior fossa / base of skull can alter this. For example this angle is elevated in ach...
The tentorial nerve is the first branch of the ophthalmic division of the trigeminal nerve (CN Va) which is the dominate dural nerve supplying most of the supratentorial dura. It specifically supplies the falx, calvarial dura and superior surface of the tentorium.
Terson syndrome refers to vitreous haemorrhage associated with subarachnoid haemorrhage, however some authors include retinal haemorrhage as well. The syndrome is a poor prognostic marker in patients with subarachnoid haemorrhage.
Terson syndrome has been reported to occur in 13-5...
Third branchial cleft cysts are a very rare type of branchial cleft cysts. Although they are extremely rare, they remain the second most common congenital lesion of the posterior cervical region after cervical lymphatic malformations or cystic hygromas 3.
By definition, a t...
The thumb sign in epiglottitis is a manifestation of an oedematous and enlarged epiglottis which is seen on lateral soft-tissue radiograph of the neck, and it suggests a diagnosis of acute infectious epiglottitis. This is the radiographic corollary of the omega sign 1-3.
Thumb sign is...
Thymic cysts are cysts that occur within, or arise from, the thymus.
Thymic cysts are uncommon lesions and are estimated to account for approximately 1-3% of all anterior mediastinal masses 4. Approximately 50% of congenital thymic cysts are incidentally discovered during the firs...
The thyrocervical trunk is one of the 3 branches of the first part of the subclavian artery and gives of numerous branches to supply viscera of the neck, the brachial plexus, neck muscles and the scapular anastomosis.
The trunk arises lateral to the vertebral artery from the anterosuperior wall...
The thyroglossal duct is an epithelium-lined connection between the foramen caecum and the thyroid that develops during the descent of the thyroid. It usually involutes in the 8th-10th week of gestation.
The thyroglossal duct arises from foramen caecum located at the junction of...
Thyroglossal duct cysts (TGDC) are the most common congenital neck cyst. They are typically located in the midline and are the most common midline neck mass in young patients. They can be diagnosed with multiple imaging modalities, including ultrasound, CT, and MRI.
The thyrohyoid muscle is an infrahyoid muscle of the neck that is innervated by the ventral ramus of C1. The primary function of the thyrohyoid muscle is to depress and fix the hyoid bone and larynx though it may also raise the larynx when the hyoid bone is fixed.
origin: oblique line ...
Thyroid acropachy is an unusual presentation of autoimmune thyroid disease, (~1% of patients with Graves disease). It can occur in hyperthyroid, euthyroid, hypothyroid, or even post-treatment patients. It is almost always associated with thyroid ophthalmopathy.
The majority of pa...
Successful treatment of thyroid malignancies highly depends on accurate preoperative staging.
Ultrasound and ultrasound guided FNA or core biopsy remain the investigation of choice for diagnosing primary thyroid malignancies; CT and MRI are inferior to ultrasound for characterising thyroid nodu...
The thyroid cartilage is the largest of the cartilages of the larynx, with its superior pole sitting at the level of the C4 vertebrae.
The thyroid cartilage consists of two laminae that are fused anteriorly in the median plane to form the laryngeal prominence. Each laminae posses...
The thyroid gland is an endocrine organ in the neck which is completely enveloped by pretracheal fascia (middle-layer of the deep cervical fascia) and lies in the visceral space.
The thyroid extends from C5 to T1 and lies anterior to the thyroid and cricoid cartilages of the lar...
TIRADS is a risk stratification system for classifying thyroid lesions and was recently recognized in an American College of Radiology (ACR) white paper 1. Its use is being advocated similar to BIRADS category for breast lesions.
In 2017, a white paper 2 was released by the ACR committee on th...
Thyroid inferno refers to the colour Doppler appearance of the thyroid gland in active Graves disease (inclusive of variants such as Marine Lenhart syndrome), and consists of multiple small areas of colour flow seen diffusely throughout the gland representing increased vascularity and arterioven...
A number of inflammatory conditions can affect the thyroid gland, which are commonly described as thyroiditides:
acute suppurative thyroiditis (AST)
subacute lymphocytic thyroiditis: silent thyroiditis or painless subacute thyroiditis
Thyroid lymphoma is rare, accounting for a minority of both thyroid malignancies and lymphoma in general.
The thyroid may be affected primarily or secondary to lymphoma elsewhere. This article is concerned with primary thyroid lymphoma.
Thyroid lymphoma accounts for <5% of thyr...
Thyroid malignancies are most commonly primary thyroid cancers but can rarely be metastatic deposits.
Thyroid malignancies can be categorised into the following key subtypes:
primary thyroid cancers
papillary thyroid carcinoma: 60-80% of carcinomas
A mnemonic for thyroidal mass differential diagnosis is:
C: colloid cyst
H: hyperplasia (parathyroid gland)
Thyroid scan (thyroid scintigraphy) is a nuclear medicine examination used to evaluate thyroid tissue.
functional status of a thyroid nodule
thyrotoxicosis: differential diagnosis
whole body scan for distant metastases
estimation of local residual thyro...
Thyroid-associated orbitopathy (TAO) is the most common cause of proptosis in adults and is most frequently associated with Graves disease.
On imaging, it is characterised by enlargement of the extraocular muscles' bellies (frequently: inferior rectus > medial rectus > superior rectus) sparing...
The thyroidea ima artery is an uncommon variant of the blood supply to the inferior aspect of the thyroid gland. It is reported in ~7.5% (range 1.5-12.2%) of individuals and can arise from:
right common carotid artery
internal thoracic artery
The thyroidea ...
Thyrotoxicosis is a hypermetabolic clinical syndrome caused by a pathological excess of circulating free T4 (thyroxine) and/or free T3 (triiodothyronine).
Although commonly done, thyrotoxicosis should not be confused nor synonymized with hyperthyroidism, the latter of which is a gr...
Tinnitus refers to a sensation of “sound in one ear or both ears, such as buzzing, ringing, or whistling, occurring without an external stimulus” 1. It can be subjective or objective.
It is thought that as many as 40 million people in the United States may have tinnitus. The repo...
Tobey-Ayer-Queckenstedt sign is used in the diagnosis of unilateral and bilateral lateral sinus thrombophlebitis. In cases where the lateral sinus is obstructed on one side, compression of the jugular vein on the intact side causes a rise in CSF pressure, whereas compression of the obstructed si...
Tolosa-Hunt syndrome (THS) is an idiopathic inflammatory condition that involves the cavernous sinus and orbital apex, and is essentially a clinical diagnosis of exclusion.
Clinically it refers to the presence of a painful ophthalmoplegia secondary to surrounding cavernou...
The tongue is a complex, principally muscular, structure that extends from the oral cavity to the oropharynx. It has important roles in speech, swallowing and taste.
The tongue has a tip, ventral surface, dorsal surface and root. The tongue is made of a midline lingual septum an...
Tonsillitis refers to inflammation of any of the tonsils and is one of the most common head and neck infections in adolescents and young adults.
Patients may present with a variety of symptoms including painful throat (may be unilateral), dysphagia, fevers, tender cervica...
Tonsilloliths, also known as tonsil (or tonsillar) stones or calculi, are clusters of calcifications that form in tonsillar crypts, within the tonsils or around them. Although they are uncommon and benign, they may be symptomatic (pain, halitosis, etc).
Small foci of calc...
Tornwaldt cyst (also spelled as a Thornwaldt cyst or Thornwald cyst) is a common incidental benign midline nasopharyngeal mucosal cyst.
The lesion is developmental and usually asymptomatic. In most cases it is found incidentally and as such age of diagnosis represents age of imagi...
Torticollis (wryneck) is a clinical finding of head tilt with or without rotational spinal malalignment. It is not a diagnosis in itself and there are a wide range of underlying conditions. It is most common in the paediatric age group.
Torticollis can be acute (<1 week) or chronic ...
Torus tubarius or cushion of the auditory canal is a mucosal elevation in the lateral aspect of the nasopharynx, formed by the underlying pharyngeal end of the cartilaginous portion of the Eustachian tube. The opening of the Eustachian tube is anterior to the torus tobarius. Immediately posterio...
The Towne projection is an fronto-occipital projection with the central ray angle laying 40 degrees cranially in the midline to the patient. The projection is used to visualize the petrous part of the pyramids, the dorsum sellae and the posterior clinoid processes, which are visible in the shad...
The trachea, known colloquially as the windpipe, connects the upper respiratory tract to the lungs via the tracheobronchial tree, enabling gas exchange.
The trachea is a tube-shaped structure consisting of 15-to-20 D-shaped cartilage rings anterolaterally bridged by annular ligam...
The transverse cervical artery, also known as the cervicodorsal trunk, is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It is a short artery that bifurcates into the superficial and deep branches, both which course superficially and laterally acro...
The transverse cervical nerve, also known as the superficial cervical nerve, cutaneous cervical nerve or anterior cutaneous cervical nerve of the neck, is a cutaneous branch of the cervical plexus that innervates the skin covering the anterior cervical region.
The transverse muscle of the tongue is one of the 4 intrinsic muscles of the tongue which alters the shape of the tongue mass, being entirely confined to the tongue without an attachment outside the tongue (like the extrinsic muscles of the tongue).
The muscles fibres attach prox...
Transverse temporal bone fractures are orientated perpendicular to the long axis of the petrous temporal bone, with the line of force running roughly anterior to posterior. A more current classification of the extent of temporal bone fractures describes the integrity of the otic capsule rather t...
A trapdoor fracture is a fracture of the orbital floor where the inferiorly displaced blowout fracture recoils back to its original position and potentially entraps contents of the orbit. It is seen in children and young adults due to the elasticity of the orbital floor. These fractures may be s...
The trapezius muscle is a large, broad superficial muscle of the posterior neck and back. It gains its name from its diamond shape. Along with sternocleidomastoid muscle, it is invested by the superficial layer of the deep cervical fascia, which splits around it.
origin: superior nuch...
The triangles of the neck are surgically focussed divisions of the neck, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on imaging (see deep spaces of the neck).
The neck can be divided into anterior and posterior trian...
The trigeminal nerve is the fifth cranial nerve and its primary role is relaying sensory information from the face and head, although it does provide motor control to the muscles of mastication. It is both large and complicated and has multiple brainstem nuclei (sensory and motor) as well as man...
A mnemonic for remembering the names of the skull foramina that the division of the trigeminal nerve (CN V) pass through is:
Standing Room Only
standing: superior orbital fissure (ophthalmic division of trigeminal nerve)
room: foramen rotundum (maxillary division of trigeminal nerve...
Trigeminal neuralgia or tic douloureux corresponds to a clinical manifestation of sudden severe paroxysms of excruciating pain on one side of the face which usually lasts a few seconds to a few minutes, involving one or more branches of the trigeminal nerve (CN V). Vascular compression is the mo...
Trochlear apparatus calcification in the orbit is a common incidental finding on CT of the head, found in ~12.5% of patients. There is no association with diabetes mellitus but an association has been demonstrated with autoimmune disease and elevated ALP 1,2.
The true vocal cords are the thickened, free edge of the cricovocal membrane, the cricovocal ligament, lined by mucous membrane 1. Together they form part of the glottis, the V-shaped aperture through which air passes. Their primary role is in phonation where vibration of the adducted vocal cord...
A trumpeted internal acoustic meatus (IAM) is an indirect sign of an acoustic schwannoma and is useful in helping differentiating between one and other cerebellopontine angle entities, especially from a meningioma which typically does not extend into the meatus 1.
It is characterized by widenin...
Tuberculous cervical lymphadenitis, also known as scrofula and King's evil, continues to be seen in endemic areas and in the industrialised world particularly among the immunocompromised.
Tuberculous cervical lymphadenitis is the most common manifestation of extrapulmonary tubercu...
Tuberculous otomastoiditis is an uncommon form of acute otomastoiditis that occurs secondary to tuberculosis infection, although its frequency is increasing as a result of greater population of immunocompromised patients.
Classically it is described as presenting with
The tuberculum sellae is the ridged process of the sphenoid bone which forms the anterior wall of the sella turcica.
The tuberculum sellae forms the anterior wall of the sella turcica, which houses the pituitary gland. It is an elongated ridge located immediately poste...
The Tullio phenomenon describes the precipitation of vertigo and nystagmus by a loud noise.
The tympanic membrane and ossicular chain must be intact with a mobile footplate. It can be present in may situations
congenital syphilis, with a semicircular canal fistula
The tympanic membrane is a thin membrane that separates the external ear from the middle ear. It acts to transmit sound waves from air in the external auditory canal to the ossicles of the middle ear.
The malleus is the first bone in the ossicular chain that eventually sees the sound wave trans...
Tympanic membrane retraction usually occurs when a portion of the tympanic membrane becomes weakened and is pulled inwards by the negative pressure within the middle ear.
As the tympanic membrane is pulled inwards (medially), it can become draped over the ossicles, resulting in a va...
The tympanic part of the temporal bone is situated inferiorly to the squamous part and anteriorly to the mastoid part.
The tympanic part surrounds the external auditory meatus, forming the anterior wall, floor and some of the posterior wall of the bony external acoustic meatus. The lateral bord...