Date post: | 15-Jul-2015 |
Category: |
Education |
Upload: | kanato-assumi |
View: | 1,010 times |
Download: | 2 times |
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