Radiology in Head and Neck

Presenter : Kanato T

INTRODUCTION

Radiology is a continually evolving medical specialty

Since the discovery of x-rays.

Resulting in the numerous imaging modalities

One should bear in mind that most imaging techniques utilizing ionizing radiation, including plain films, computed tomography (CT) and nuclear medicine

Carry with them a lifetime risk of developing cancer.

Radiological Investigations

Useful To The ENT Surgeon X-rays

Ultrasound

CT

MRI

PET Scans

Barium Swallow

Angiography

Dacryocystography

Sialography

Orthopantomogram

X-ray photons

What Is an X-Ray? An x-ray is a discrete bundle of

electromagnetic energy called a photon. similar to other forms of electromagnetic

energy such as light, infrared, ultraviolet, radio waves, or gamma rays.

Having no electrical charge, x-rays are more penetrating than other types of ionizing radiation (such as alpha or beta particles) and are therefore useful for imaging the human body.

Image Appearance

Four basic densities:

1. Air is black or very dark.

2. fat is generally gray and darker than muscle or blood

3. Bone and calcium appear almost white.

4. Items that contain metal (such as prosthetic hips) and contrast agents also appear white.

The contrast agents are barium for gastrointestinal studies and iodine for most intravenously administered agents

Image clarityDepends on kVp, mA, Time (sec) If radiograph is too light Increase kVp (increase the

penetrating power or energy of the x-ray photons)

Increase mA (produce more photons)

Or to increase time (produce more x-ray photons)

If a radiograph is too dark (overexposed) decrease kVp, mA, or time

Conventional Radiology

Temporal Bone: Law’s View, Schullars view,

Stenver’s View, Transorbital View,

Submentovertical View.

Nose and Paranasal Sinuses: Water’s View,

Caldwell View, Lateral View, Right and Left

Oblique Views, Lateral and Occlusal Views of

Nasal Bone.

Neck: Lateral View and Anteroposterior

Views of Neck, Soft Tissue Lateral View

Nasopharynx, Submandibular Salivary Gland

Law’s View (Lateral view of

Mastoid)

In 1913, Dr Frederik Law described lateral

view of mastoid bone.

Sagittal plane of the skull is parallel to the flim

X ray beam is projected 15 degree

cephalocaudal.

Structures seen:

External auditory

canal (EAC)

(superimposed on

internal auditory

canal (IAC)),

mastoid air cells,

tegmen,

lateral sinus plate

temporomandibula

r joint.

Schullar’s view 1906, Dr Arthur Schuller, an Austrian

neuroradiologist, described an oblique view

of mastoid bone.

X-ray beam is projected 30° cephalocaudal

and prevents superimposition of two sides

of mastoid bones.

Structures seen: EAC superimposed on

IAC, mastoid air cells, tegmen, lateral sinus

plate, condyle of mandible, sinodural angle

and atticoantral region (key areas for

cholesteatoma and its erosion).

SCHULLER S VIEW

Clinical applications:

Extent of pneumatization, sclerotic mastoid, destruction of intercellular septa (mastoiditis),

location of sinus plate (position of sigmoid sinus) and

tegmen (roof of middle ear and floor of middle cranial fossa),

cholesteatoma and

longitudinal fracture of petrous pyramid.

Stenver’s view:

In 1917, Dr H. W. Stenver described Stenvers

view of temporal bone

Long axis of the petrous bone lies parallel to

the film.

Structures seen

Entire petrous pyramid,

arcuate eminence,

internal auditory meatus,

labyrinth with its vestibule,

Cochlea

and mastoid antrum

Stenver’s view:

Towne’s view: In 1926, Dr E. B. Town of England described

Towns view.

This is an anteroposterior view of skull with

30° tilt from above and in front.

It shows both petrous pyramids, which can be

compared.

Towne’s view

Structures seen: Both side temporal

bones,

arcuate eminence and superior

semicircular canal, mastoid antrum, IAC,

tympanic cavity, cochlea and EAC

Clinical applications: Acoustic neuroma

and apical petrositis.

Transorbital view:

This is an anteroposterior view of skull.

Orbitomeatal line is at right angles to the film.

X-ray beam passes through the orbit.

Structures seen: IAC, cochlea, labyrinth and both

petrous pyramids projected through the orbits.

Clinical applications: Acoustic neuroma and petrous pyramid.

TRANSEORBITAL PROJECTION:

Submentovertical view:

Vertex remains near the film and X-ray

beam is projected from the submental

area.

Structures seen:

External auditory

cannal,

Middle air cleft. ie.

mastoid cells, middle

ear & eustachian tube

Internal auditory

canal

sphenoid sinuses

nose and paranasal Sinuses

Water’s view (occipitomental view):

In 1914, Dr C. A. Waters and C. W. Waldron, two British radiologists, introduced the Waters view.

Nose and chin touch the film and X-ray beam is projected from occipital side.

Open mouth view shows sphenoid sinus. Petrous bones are projected below the maxillary sinuses.

Fractures of right and left nasal bones and

their lateral displacement can be seen.

Structures seen

Maxillary (seen best)

Frontal and sphenoid sinuses

zygoma, zygomatic arch

Nasal bones, frontal process of maxilla, superior orbital fissure

and infratemporalfossa.

Caldwell view (occipitofrontal

view): Eugene W. Caldwell, In 1903, described a

view of the paranasal sinuses that still bears

his name, “the Caldwell view”

Nose and forehead touch the film and X-ray

beam is projected 15–20° caudally.

Frontal and ethmoidal sinuses are seen well

in this view.

Structures seen Frontal, ethmoid and

maxillary sinuses,

Frontal process of

zygoma, zygomatic

process of frontal

bone

superior margins of

orbits, lamina

papyracea,

superior orbital

fissures.

Lateral view

Lateral side of the skull lies against

the flim and X ray beam is projected

perpendicular from other side.

Structures seen :

Anterior and posterior extents of

sphenoid, frontal and maxillary

sinuses, sella turcica,

Ethmoid sinuses, alveolar process,

condyle and neck of mandible.

Common radiologic abnormalities

Air-fluid levels suggest an acute

process

Opacification = secretions, polyps, etc.

Thickened mucosa : Suggests chronic

inflammation

Lateral views of nasal bones: To see fracture line, depression or elevation of

the fractures segment.

Lower part of nasal bones, which is thin,

fracture more frequently.

Groove for ethmoidal nerve and vessels may

look like fracture line

Occlusal view of nasal bone:

Film is held between

the teeth and X-ray

beam is projected

perpendicular to the

film.

It shows fracture line

and lateral

displacement of the

nasal pyramid clearly.

Neck, Larynx and PharynxLateral view of neck Structure seen: Outline of

base of tongue, vallecula,

hyoid bone, epiglottis and aryepiglottic folds, arytenoids,

false and true cords with ventricle in between them,

thyroid and cricoid cartilages, subglottic space

and trachea, prevertebralsoft tissues, cervical spines

and pretracheal soft tissues and thyroid.

Clinical applications:

Radio-opaque foreign bodies of larynx, pharynx and upper esophagus

Acute epiglottitis

Retropharyngeal abscess:

Position of tracheostomy tube and laryngeal stent

Laryngeal stenosis

Fractures of larynx and hyoid bone and their displacement

Compression of trachea by thyroid or retropharyngeal masses

Caries of cervical spine associated with retropharyngeal abscess

Osteophytes in cervical vertebrae and injuries of spine.

Chronic Retropharyngeal abscess

Secondary to TB

spine(Pott’s spine)

Erosion of cervical

vertebra

Treatment with

ATT

FB Cricopharynx with Acute

retropharyngeal abscess

Acute epiglottitis(Thumb sign)

Anteroposterior view of neck:

It helps in differentiating between a

foreign body of larynx and esophagus

(lateral view is also needed).

It shows compression or displacement

of trachea by lateral neck masses

such as thyroid swellings.

Round radio

opaque object

(Coin) in

Esophagus

Because the

esophagus is an

AP compressed

tubular structure.

Croup (acute laryngotracheobronchitis)

Steeple Sign

Soft tissue lateral view nasopharynx:

For soft tissue masses in the nasopharynx,

soft palate, roof and posterior wall of

nasopharynx.

Clinical applications:

Adenoids

Angiofibroma

Antrochoanal polyp

Foreign body nose and tumor.

Choanal atresia

Enlarged Adenoids

Submandibular salivary gland:

Radio-opaque calculus can be seen.

Barium Swallow

procedure used to examine upper

gastrointestinal tract,which include the

pharynx, esophagus, cardia of stomach.

The contrast used is barium sulfate.

TYPES OF CONTRAST STUDY

(i) SINGLE CONTRAST STUDY

(ii) DOUBLE CONTRAST STUDY

CONTRAINDICATION Suspected esophageal perforation.

Tracheo-esophageal fistula

If strong clincal suspicion of aspiration

or TEF,then omnipaque swallow

(iohexol) advised.

XRAY VIEW

SOFT TISSUE NECK,CHEST – AP &

LAT

NORMAL-AP /LAT VIEW - SCOUT

AP/LAT VIEW WITH BARIUM

EFT: Lateral view: Epiglottis (red arrow). Post cricoid impression (yellow arrows).

Cricopharyngeous impression (white arrow).RIGHT: AP-view: Small lateral pharyngeal pouches (arrows)

CA ESOPHAGUS

The stenotic segment is long giving a “rat-tail” appearanceBarium swallow shows mild dilatation of the esophagus with irregular stenotic lesion in the lower end of the esophagus “moth eaten appearance

ACHALASIA CARDIA

Bird beak appearance

Sialography

Radiologic examination of the salivary

glands

The submandibular and parotid glands

are investigated by this method

The sublingual gland is usually not

evaluated this way because of

difficulty in cannulation

Procedure

Obtain preliminary radiographs

Any condition that is visibe w/o contrast

Optimum technique obtained

2-3 min before procedure give lemon

Contrast media (iohexol) injected into

main duct

After procedure suck on lemon to clear

contrast

10 min after procedure take radiograph

Parotid Radiographs Set-Up

ORTHOPANTOMOGRAPHY

(tomography of the mandible) A pantomograph is a

panoramic radiograph machine.

It permits visualization of entire maxillary and mandibular dentition,

alveolar arches and contiguous structures on a single extraoralfilm

ULTRASOUND Ultrasound is sound within a frequency above

the upper limit of normal hearing.

Ultrasound images are formed from reflected

sound waves.

Sound waves are generated in short bursts by

the transducer (or probe)

and the sound energy that is reflected back is

collected at the point of origin (the transducer)

Transducer(probe)

Piezoelectric material is used to

produce sound wave

Usually lead zirconate titanate

The higher the frequency of the probe

the lesser the depth of penetration but

gives better spatial resolution.

In neck most of the structures of interest

are superficial and required a higher

frequency probe of greater than 7.5

MHz

Advantages

no known harmful effects and no contraindications.

High-resolution ultrasound is quick and accurate;

Further, it is relatively inexpensive compared to CT or MRI.

In addition to using echoes to generate images, we can analyze the returning echo frequencies. This Doppler analysis allows identification of moving blood as well as its direction and magnitude

Ultrasound appearance of

common abnormalities.Lymph Nodes

Normal lymphnode may be visualized by usg

in healthy subject, they are often not seen

due to their small size and similar echo-

texture with surrounding structure.

When apparent, lymph nodes are reactive,

inflammatory or neoplastic.

Retropharyngeal lymph nodes cannot be

seen with ultrasound.

Reactive lymph node.

(a) An oval-shaped,

low-reflective lymph

node with an

echogenic hilum

(arrow)

(b) Florid colour

Doppler flow to the

central hilum

consistent with a

benign reactive

lymph node

Squamous cell

carcinoma lymph

node metastasis.

An enlarged low

reflective mass with

an irregular border

(long arrow)

carotid artery (short

arrow)

Thyroid For ultrasound imaging thyroid disorder may be

considered into two groups

Nodular

Diffuse

Major role of usg in the assessment of disease

1. Detection of focal masses

2. Differentiation of multinodular goiter/hyperplasia from other nodular disease

3. To document the extent of a known thyroid malignancy;

4. Follow up to look for residual, recurrent or metastatic carcinoma;

5. Guidance for FNAC or fine needle aspiration for biopsy.

Salivary gland disease

Both the parotid and submandibular glands

are superficial and well sited for ultrasound

examination

Ultrasound accurately differentiates salivary

gland tumors from other lesions outside gland

Calculi larger than 2mm are detected by usg

And useful in defining location of calculi in

relation to the gland parenchyma

It detects the presence and extends of any

abscess formation.

Doppler ultrasound measures blood

flow of vessels.

In Color Doppler flowing blood

appears either red or blue,

which depends upon the blood

direction, towards or away from the

transducer.

„ Power Doppler: It can demonstrate

tissue perfusion.

Applications of Ultrasound Differentiating cystic from solid masses

„Metastatic lymph nodes

„Tumor invasion of carotid vessels and internal jugular

vein.

„Tumors of parotid and submandibular salivary glands

„Salivary duct stones even less than 2 mm

„Detection and drainage of salivary gland abscess

under US guidance

„Masses of thyroid and parathyroid glands and US

guided fine needle biopsy

„ Neck lymphoma.

Computed tomography

In 1972 Godfrey Hounsfield of Great Britain invent CT.

Computed tomography (CT) is accomplished by passing a rotating fan beam of x-rays through the patient and measuring the transmission at thousands of points.

The data are handled by a computer that calculates exactly what the x-ray absorption was at any given spot in the patient.

Compared with plain x-rays, CT uses about 10 to 100 times more radiation

Computed tomography imaging

Imaging can be obtained in several planes.

In most cases the axial (transaxial) plane, usually parallel to the orbitomeatal or infraorbitomeatal plane, is used with the patient lying Supine

In addition, direct coronal imaging and even direct sagittal imaging can be performed.

In fact images can be reformatted in any plane or any angle

Different views of CT pns Coronal image

Axial image

Sagittal image

Computed tomography

Conventional CT scanners have traditionally operated in a step-and-shoot mode, defined by data acquisition and patient positioning phases

Helical CT is characterized by continuous patient transport through the gantry while a series of x-ray tube rotations simultaneously acquires volumetric data.

The evolution of multidetector CT scanners (MDCTs) has resulted from the combination of helical scanning with multislice data acquisition.

Computed tomography

In general, the basic four densities on

CT images are the same as those in

plain x-rays:

air is black,

fat is dark gray,

soft tissue is light gray,

bone or calcium and contrast agents

are white

CT image display

Hounsfield unit: value of CT number

Defined by the relationship between the

linear attenuation value of the material

being scanned and that of water.

Gas = -1000 HU

Water = 0 (zero) HU

Bone = +1000 HU

Fat = - 80 to -100 HU

CT image display The window level is simply the midpoint of the

densities chosen for display

For imaging of the soft tissues of the head and neck, a window level of approximately 40 to 70 HU is usually chosen, at a midpoint approximately equal to the density of muscle

For imaging bony structures such as paranasalsinuses and temporal bone, window levels from 0 to +400 HU and a very wide window width of 2000 to 4000 HU may be chosen

The terminology commonly used to describe

the above mentioned windows includes soft

tissue windows (window width of 250 to 400

HU) and bone windows (2000 to 4000 HU).

Soft tissue window CT image

Bone window CT image

Contrast CT:

Intravenous

contrast agents

allow identification

of rim

enhancement in

pathological lymph

nodes and

increase the

definition of

primary tumors.

Spiral CT

Helical or spiral CT scans a volume of

tissue and

provides better quality images than

the conventional CT.

It covers more than 300 cm tissue

during a single breathhold of 30

seconds

multidetector CT scanners

(MDCTs) MDCT can reduce scan time, permit

imaging with thinner collimation, or

both

Multidetector CT offers the additional

advantages of decreased contrast

load, reduced respiratory and cardiac

motion artifacts, and enhanced

multiplanar reconstruction capabilities.

CT angiography:

With intravenous bolus administration of iodinated contrast material.

permitted successful imaging of entire vascular distributions

CT angiography has become an important tool for assessment of the abdominal and iliac arteries and their branches, the thoracic aorta, the pulmonary arteries, and the extra- and intracranial carotid circulation.

Processing of volumetric data:

The volumetric data can be processed

to produce

Multiplanar images: Sagittal and

coronal

Three-dimensional (3D) images

Virtual endoscopy: Such as

laryngoscopy, bronchoscopy and

sinuscopy

3-D image reformatting

To evaluate bony Structure

Like fracture, tumour, exostosis, destructive lesions etc.

Helps immensely in planning reconstruction operation

3-D reconstruction of

ct-angiography 3- D

reconstruction of cervical vessels from CT volumetric data set obtained after administration of contrast material

Gives better result than MR angiography

Optimal slice thickness

3 mm or 5mm = Neck structure

2 mm = facial bone, sinunasal cavities

and orbit, laryngohypopharyngeal

region

0.8 – 1 mm = Temporal bone

Applications of CT, Extension of mucosal tumors of suprahyoid neck and metastatic

neck lymph nodes (ring enhancement)

„Postoperative neck

„Salivary gland tumors and metastatic neck lymph nodes

„Computed tomography sialography

Cervical lymphadenopathy

„Trauma, inflammation and cancer of larynx and laryngopharynx

with metastatic neck nodes

„Large or fixed thyroid tumors invading and compressing larynx,

laryngopharynx, trachea and mediastinum

„Paranasal sinuses prior to endoscopic sinus surgery, severe

nasal polyposis, tumors

„ Facial trauma

„Temporal bone and skull base tumors, semicircular canal fistulas,

cochlear implants.

Magnetic resonance imaging

Principle

The protons in the nuclei of hydrogen behave like small spinning bar magnets and align with a strong external magnetic field.

A radio frequency pulse knocks protons out of alignment, which release small amount of energy while gradually returning to their original position.

This energy is detected by sensitive coils, which are placed around patient.

Hydrogen atoms are abundantly present in body water and MRI can differentiate the water content of various tissues

Imaging protocols The rate of energy loss is designated as the

longitudinal (T1) and transverse (T2) relaxation times.

T1 represents the restoration of the longitudinal magnetization along the axis of the main magnetic field

T2 represents the decay time of the magnetization in the transverse plane.

Substances (e.g.,fluid) that have a long T1 will appear dark on T1-weighted images, whereas those with short T1 (fat) will display high signal intensity.

Imaging protocols

On T2-weighted images, a long T2

substance (fluid) will appear bright.

The commonly used pulse sequences

are T1-weighted (T1W), T2-weighted

(T2W), gadolinium-enhanced T1W, spin

(proton) density, fat-suppressed and

gradient echo imaging.

T1W: Because of high soft tissue discrimination, T1W images show exquisite anatomical details.

„T2W: The pathological lesions increase T2 de-phase times, which produce higher signal than surrounding normal tissue in T2W images.

The combination of T1W and T2W images is good for characterizing fluid containing structures, solid components and hemorrhage.

MRI head sagittal section T1-weighted

MRI head axial section T2-weighted

Gadolinium-enhanced T1W:

Intravenous gadolinium (used in T1W) reduces T1 relaxation time and enhances lesions, which appear as high signal intensity areas

Improved delineation of tumor margins relative to the lower signal of muscle, bone, vessel and globe.

Gadolinium enhancement is optimally used with specific fat suppression techniques.

Short-tau inversion recovery:

The STIR sequence suppresses high

signal intensity from fat (that turn fat

black) and fluid containing structures

remain high signal intensity.

In STIR, decreased signal-to-noise ratio

degrades the image.

Magnetic resonance angiography:

It uses specific sequences

and demonstrates flowing blood.

Different characteristics

(To quickly identify a T1WI: fat is white, CSF and vitreous are black, and nasal mucosa is low signal.)

(To quickly identify a T2WI: CSF, vitreous, and nasal mucosa are white. Fat is low to intermediate in signal.)

Different characteristics

To quickly identify a gadolinium-enhanced T1WI: nasal mucosa is white, fat is white, and CSF and vitreous are black

To quickly identify a STIR image(fat suppresion): fat is almost completely black; CSF, vitreous, and mucosa are white

ADVANTAGES

Superior soft tissue contrast resolution

than CT

No radiation exposure

Less image quality gets hampered by

the presence of dental fillings

DISADVANTAGES

Long image acquisition time

More chance of motion artifacts

Difficult to stage both primary tumour and neck nodal disease

Higher cost and less availability

Absolute contraindications to MRI include patients with cardiac pacemakers, cochlear implants, and ferromagnetic intracranial aneurysm clips.

Those patients at risk for metallic orbital foreign bodies should be screened with plain films or CT before MRI.

Applications of MRI Tumors of nasopharynx, oropharynx, oral cavity

and tongue

„Extracapsular spread of tumor from nodes

„Perineural spread and extension beyond gland of salivary gland tumors

„Tumors of nose and paranasal sinuses: Distinguish between tumor and obstructed sinus secretions (hydrated fluid,viscous, desiccated);

Perineural spread to anterior cranial fossa, orbit, parapharyngeal space and pterygopalatinefossa and cribriform plate extension

„Lesions of IAC, facial nerve canal, and jugular foramen; acoustic schwannoma

„Skull base tumors

Radionuclide imaging

Intravenously administered

radiopharmaceuticals

such as technetium-99m (99mTc)-

pertechnetate concentrate selectively in

certain tissues and emit gamma

radiation detected by a gamma camera.

It provides two-dimensional display of

physiological and functional changes in

tissue

Technetium-99m (99mTc)-

pertechnetate scan:

In salivary gland imaging 99mTc pertechnetate

imaging may be useful for assessing salivary

gland function in autoimmune and

inflammatory disease of the salivary glands.

If obstructed, the degree of obstruction as well

as the follow-up of obstruction after treatment

can be assessed.

In evaluating neoplasms of the salivary glands

the findings of the 99mTcpertechnetate scan

are almost pathognomonic of Warthin's tumor

and oncocytoma.

Thyroid imaging

Most nuclear medicine imaging uses

various isotopes of iodine (131I and

123I), Technitium-99m pertechnetate

to determine thyroid function, identify

hot or cold nodules, or access extent

of thyroid masses and tumors.

1- 4 % of hot nodules – malignant

Upto 25 % of cold nodule – malignant

Positron emission tomography

The positron emission tomography provide a

means of identifying pathology based on

altered tissue metabolism.

Imagining technique relies on a radioactive

molecule(radiotracer) that decay with positron

emission.

The radiotracer is given intravenously to the

patient and is taken into cells.

Malignant cell trap more radiotracer compare

to non malignant cells.

The local radiotracer concentration can be

measured.

PET image lack anatomical details, which

can be overcome by combining with CT/MR

using software technique

Depending on the radiotracer used different

aspects of tissue metabolism can be

measured.

An analogue of glucose, 2-[18F] fluoro-2-

deoxy-D-glucose (FDG) which reflects

glucose metabolism is commonly use.

Positron Emission Tomography

Used for staging and evaluation of

recurrence for primary head and neck

tumors, detecting distant lymph node,

soft-tissue and skeletal metastases

More accurate than CT or MRI in

detecting residual or recurrent nodes

Highly reliable after 3 – 4 months of

end of treatment.

Indications of FDG with integrated PET/CT

SCC patients with

equivocal nodal disease following conventional assessment;

-suspicion of recurrent/residual disease.

Patients with occult primary tumors.

Post-treatment papillary and follicular thyroid cancer patients with elevated thyroglobulin and negative 131-I scan.

Patients with clinical suspicion of more disease than conventional assessment demonstrates.

Patients where resectability is in doubt.

Effect of radiation

The effects of radiation are usually classified into two categories, depending on the intensity of the radiation and the time period of exposure.

These electrons may damage DNA molecules directly or produce free radicals that can chemically damage genetic material; either effect may result in cell death or mutation

These categories are referred to as

1. stochastic effects

2. deterministic effects

Stochastic effects

The severity of stochastic effects is independent of the absorbed dose.

Under certain exposure conditions, the effects may or may not occur.

There is no threshold and the probability of having the effects is proportional to the dose absorbed.

Example: radiation induced cancer, genetic effect

Deterministic effects

severity of certain effects on human beings will increase with increasing doses.

There exists a certain level, the "threshold", below which the effect will be absent.

This kind of effects is called "deterministic effects“

Example: cataract, erythema, infertility etc.

References

Adam Grainger & Allison's Diagnostic Radiology 5th ed

Basic Radiology LANGE clinical science.

Scott-Brown’s Otorhinolaryngology, Head and Neck Surgery 7th edition.

Surgery of ear Glasscock Shambaugh 6th

edition.

Mohan Bansal Disease of Ear, Nose and Throat.

Head and Neck Imaging, Peter M. Som

Internet