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Write short notes on the
following: Blow-out fracture
Ossifying fibroma
Microcolon
Salter-Harris fracture
Technique of radioisotope scanning of
pulmonary embolism
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BLOW-OUT FRACTURE
Introduction
Aetiology
Incidence
Types
Clinical features
Imaging modalities
Complications
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INTRODUCTION
Blow-out fracture is defined as the fracture ofthe orbital wall with increase in intraorbital
pressure and soft tissue herniation.
It is usually the result of a direct blow to the
orbit. This results in a sudden increase in the
intraorbital pressure which in turn
causes decompression by fracture of one or
more of the bounding walls of the orbit.
Pure blowout fractures usually occurs in the
weakest parts where the wall is thin i.e the
floor, the medial wall or, occasionally, the roof.
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The orbit is a four-sided pyramidal spaceformed by seven bones
Lateral wall: zygoma, greater wing of sphenoid
Superior wall (Roof): orbital plate of the frontalbone, lesser wing of the sphenoid
Medial wall: ethmoid, lacrimal, maxilla and
sphenoid bones. There is a paper-thin bone,
lamina papyracea, between the orbit and theethmoids
Inferior wall (Floor): maxilla, zygoma, palatine
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BONY
ORBIT
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AETIOLOGY
Direct orbital blunt injury e.g via fists, elbows
Sports injury e.g via impact of squash ball,
baseball, tennis ball etc., all of which have
diameters greater than the orbital rim
Motor vehicle accidents
Facial trauma
INCIDENCEThe commonest group of patients are young men.
This is because blow-out fracture is usually due to
trauma, often of sporting origin.
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TYPES OF BLOW-OUT
FRACTURE Inferior blow-out fracture: It is the most common.
There is prolapse of orbital fat ( inferior rectus
muscle) into the maxillary sinus. In approximately
50% of cases, it is associated with fractures of the
medial wall Medial blow-out fracture: It is the second most
common type, occurring through the lamina
papyracea. Orbital fat and the medial rectus
muscle may prolapse into the ethmoid air cells. Superior blow-out fracture: Uncommon. Fractures
may involve the frontal sinus and/or the anterior
cranial fossa
Lateral blow-out fracture: It is rare and associatedwith significant craniofacial injuries
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CLINICAL FEATURES
Pain
Periorbital swelling
Temporary or permanent loss of vision
Limitation of range of ocular motion Subconjunctival haemorrhage
Facial asymmetry
Diplopia due to extra-ocular muscleentrapment
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IMAGING MODALITIES
Plain radiography
CT scan
MRI
Ultrasound
Angiography
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PLAIN RADIOGRAPHY
Views include OM, OF, lateral
Occipitomental (OM) view is the most suitable to assess
inferior orbital wall fractures. This may reveal discontinuity
within the orbital floor, air-fluid level or soft tissue density
within the maxillary sinus, a polypoid mass hanging from the
floor into the maxillary antrum (tear-drop sign). This polypoidmass consists of herniated orbital contents, periorbital fat and
inferior rectus muscle.
Occipitofrontal (OF) view better assesses medial orbital wall
fracture. Penetration of air from the ethmoidal sinus is seen
as lucency in the orbit (Orbital emphysema). Fluid may bealso seen in the ethmoidal sinus
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Plain skull radiograph (OM view) showing a mass projectingfrom the left orbital floor into the left maxillary sinus
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CT SCAN
Due to its good bony resolution and multi-slice properties, CTgives better localisation of fracture site by clearly defining
bone fragments, air and foreign body.
A hypodense discontinuity is seen within the hyperdense
orbital wall.
Associated findings include: presence of intra-orbital
haemorrhage, globe injury/rupture, extraocular muscle
entrapment and prolapse of orbital fat
CT may also reveal bleeding into the sinus, which, depending
on the duration, can be hyperdense (acute), isodense (sub-
acute) or hypodense (chronic)
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Coronal cranial CT image showing fracture of the right inferior
orbital wall with herniation of orbital contents into the right maxillary
sinus
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Coronal cranial CT image showing fractures of the left inferior
and medial orbital walls
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Cranial CT image (saggital reformat) demonstrating fracture of
the left inferior orbital wall with associated inferior rectus muscle
entrapment
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MRI
MRI gives excellent soft tissue resolution andmultiplanar images of the orbits.
Prolapsed orbital fat appears hyperintense on both
T1 and T2 sequences
The signal intensity of any associatedhaemorrhage varies depending on the duration of
the bleed
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T1-weighted coronal cranial MR image showing inferior
herniation of the right orbital fat
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ULTRASOUND This employs the use of a high-frequency ultrasonic
transducer to assess for possible complications of orbitalcontents
Vitreous haemorrhage is seen as internal echoes within the
posterior segment.
Retinal or choroid detachment is seen as a V-shaped
echogenicity in the posterior part of the eye .
A foreign body within the orbit is echogenic with/without
posterior acoustic shadow
ANGIOGRAPHY This includes conventional angiography, CTA or MRA
Useful in the assessment of the ophthalmic artery
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COMPLICATIONS
Subluxation/dislocation/rupture of the lens
Vitreous haemorrhage
Retinal or choroid detachment
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OSSIFYING FIBROMA
Introduction
Incidence
Clinical features
Imaging modalities
Radiological features
Complications
Differentials
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INTRODUCTION
Ossifying fibroma is a benign slow-growing centralbone tumour composed of bone that develops
within fibrous connective tissue.
It is also known as Osteofibrous Dysplasia (OFD)
or Jaffe-Campanacci Syndrome. The pathology comprises maturing cellular fibrous
spindle cells with osteoblastic activity producing
many calcific cartilaginous and bone densities
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INCIDENCE
It occurs commonly in the 2nd to 4th decade of life
M < F
Common locations include:
Lower extremity:
Tibia: seen in 90% of cases. There is
predilection for the anterior tibial cortex
Femur: Usually occurs in the diaphysis
Jaw: maxilla and mandible. Also known ascemento-ossifying fibromas
Frontal bone, ethmoid bone etc
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CLINICAL FEATURES
Pain (though usually painless)
Swelling
Facial asymmetry due to bone
expansion
Tooth displacement
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IMAGING MODALITIES
Plain radiography
CT scan
MRI
Radionuclide imaging
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PLAIN RADIOGRAPHY
It is seen as a well circumscribedlesion surrounded by a thin line of
lucency (fibrous capsule), which is in
turn surrounded by thin sclerotic rim ofreactive bone (osteoblastic rimming).
May present as eccentric ground-
glass lesion, resembling fibrousdysplasia
There is moderate expansion of intact
cortex
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CT SCAN
CT demonstrates a well circumscribedhomogeneous lesion with evidence of
intracortical hypodensity and
characteristic hyperdense band(osteoblastic rimming)
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Axial CT of the lower jaw (bone window) showing a circular
partially calcified lesion within the mandible. There are
internal ground-glass calcifications
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MRI
The lesion is hypointense on T1 and (with typicalcontrast enhancement) and iso- to hyperintense on
T2
RADIONUCLIDE IMAGING It shows intense focal uptake on 99mTc bone scan.
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COMPLICATIONS
Pathological fracture Limb bowing
Recurrence
TREATMENT/PROGNOSIS Ossifying fibroma tends to regress over time.
For locally aggressive lesions, surgical resection is
often curative
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DIFFERENTIALS
Fibrous dysplasia: Has no osteoblastic rimming Adamantinoma: May share a common origin with
ossifying fibroma. It is distinguished from ossifying
fibroma by presence of soft tissue extension,
intramedullary extension and periosteal reaction. Osteoid osteoma: Consists of 3 concentric parts
nidus, fibrovascular rim and surrounding reactive
sclerosis
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MICROCOLON
Definition
Aetiology
Clinical presentation
Imaging modalities
Radiological features
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DEFINITION
Microcolon is a radiological finding of small-calibre unused colon, seen in the neonate
on radiographic contrast enema
It signifies intestinal obstruction above the
colon and it is probably caused in utero by
lack of appropriate distension of the colon
with intramural content
There are no absolute standards for themeasurement of this condition.
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AETIOLOGY
Mnemonic: MI MCA
Meconium ileus/meconium peritonitis
Ileal/jejunal atresia
Megacystis-microcolon-hypoperistalsis
syndrome
Colonic atresia
Aganglionosis (Hirschsprungs
disease)
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CLINICAL PRESENTATION Abdominal distension
Bilous vomiting
Failure to pass meconium within 48hours
IMAGING MODALITIES Plain radiography
Contrast enema Ultrasound
CT scan
MCUG
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MECONIUM ILEUS
This is the obstruction of the small bowel in theterminal ileum from impacted meconium
It manifests within 48 hours of birth. Meconium is
normally evacuated within first 6 hours
Majority of infants with meconium ileus prove tohave cystic fibrosis. Approximately 20% of infants
with cystic fibrosis present with meconium ileus at
birth. It may also be seen with pancreatic atresia or
stenosis of the pancreatic duct
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MECONIUM ILEUS (CONTD)Plain Radiography:
Non-specific. May show dilated small bowel loops without air-fluid levels (fluid not present)
Bubbly/frothy appearance of the distended intestinal loops
Soap bubble appearance in right lower quadrant due to
admixture of gas with meconium
Contrast Enema
Multiple round/oval filling defects in distal ileum & colon
Functional microcolon (unused colon in antenatal obstruction)
Obstetric ultrasound
Echogenic bowel which can be dilated and thick-walled
Polyhydramnios
Fetal ascites
Intra-abdominal cysts
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MECONIUM ILEUS CONTD)
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MECONIUM PERITONITIS
This refers to sterile chemical peritonitis secondaryto perforation of bowel proximal to complete
obstruction that seals in utero due to inflammatory
response
Causes as for microcolon Plain radiography: intra-abdominal calcifications
Contrast enema: separation of bowel loops by fluid;
microcolon
Ultrasound: highly echogenic material throughoutthe abdomen in between bowel loops (snowstorm
appearance)
Obstetric ultrasound: as for meconium ileus
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MECONIUM PERITONITIS (CONTD)
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JEJUNAL/ILEAL ATRESIA
This is a congenital anomaly characterized by closure of thejejunum or ileum.
The aetiology is thought to be from an intrauterine ischaemic
injury to the developing gut
May be associated with malrotation, volvulus, gastroschisis,
omphalocele
Plain radiography: Triple bubble appearance (double bubble
of duodenal atresia + third bubble due to air in the proximal
jejunum). Multiple dilated small bowel loops proximal to the
atresia
Contrast enema: Typically shows microcolon
Obstetric ultrasound: Dilated proximal bowel loops, often >
7mm
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JEJUNAL/ILEAL ATRESIA (CONTD)
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COLONIC ATRESIA
Less common than jejunal/ileal atresia
Plain radiography: massive dilatation of colon
proximal to obstruction. Mottled pattern of gas +
feces proximal to point of atresia
Contrast enema: Functional microcolon. There may
be obstruction to retrograde flow of contrast
Ultrasound: dilated echogenic distal small bowel +
proximal colon (from retained meconium)
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COLONIC ATRESIA (CONTD)
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MEGACYSTIS-MICROCOLON-
HYPOPERISTALSIS SYNDROME
Also known as Berdon syndrome. M:F is 1:7 This is a functional obstruction of bladder + colon
characterized by enlarged urinary bladder, small colon and
markedly enlarged hydronephrotic kidneys with little
remaining parenchyma
The prognosis is lethal in most cases
Obstetric ultrasound: female sex; normal amount of amniotic
fluid in spite of dilated bladder; bilateral megaloureters
hydronephrosis
Contrast enema: microcolon with narrow rectum + sigmoid;
malrotation or foreshortening of small bowel
MCUG: Distended unobstructed bladder with poor/absent
muscular function
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HIRSCHSPRUNGS DISEASE
This is caused by absence of parasympatheticganglia in muscle & submucosal layers due to an
arrest of craniocaudal migration of neuroblasts
along the vagal trunks
Microcolon is seen in less than one-quarter ofpatients with total colonic Hirschsprungs disease
Plain radiography: multiple dilatation of bowel loops
Contrast enema: rectosigmoid calibre ratio less
than one, microcolon, delayed/disorderedevacuation of contrast from the colon, bowel
shortening
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HIRSCHSPRUNGS DISEASE
SALTER HARRIS
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SALTER-HARRIS
FRACTURE IntroductionAetiology
Incidence
Types
Clinical features
Imaging modalities
Complications
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AETIOLOGY
Sports injuries (one-third of cases) Child abuse
Injury from extreme cold (e.g frostbite)
Neurological disorders that result in sensory deficit or
muscular imbalance
Metabolic diseases e.g CRF, hormone disorders etc
INCIDENCE
Peak age is 12years M:F = 2:1
Upper extremity > Lower extremity (typically the distal radius)
Mechanism: 80% shearing force; 20% compression
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ANATOMY
The epiphyseal growth plate (where cartilagedevelops into bone) has four stages:
germinal/resting zone, proliferative zone,
hypertrophy zone, ossification zone.
Hypertrophy zone is weakest and therefore isdamaged by shearing forces that extend from there
into epiphysis or metaphysis during Salter Harris
fractures.
Major blood supply to growth plate and its germinallayer is from epiphysis.
Damage to the blood supply causes healing
problems for Salter Harris fractures
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ANATOMY
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TYPES
Salter-Harris Fractures are categorized by the location of thefracture in one or more of the physis (epiphyseal plate),
epiphysis, and metaphysis.
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TYPE I (Slipped physis)
There is slip of epiphysis due to shearing forceseparating epiphysis from physis. The surrounding
bone is not involved.
Line of cleavage is confined to the physis
Seen in 6 8.5% of cases There is widening of the growth plate as well as
displacement of the epiphyseal ossification centre
Commonly seen in the phalanges and distal radius.
Slipped capital femoral epiphysis is a type I SHF Prognosis is favourable, irrespective of the location
It is treated by simple closed reduction and
immobilization
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TYPE I (CONTD)
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Salter Harris type I of distal radius
SLIPPED CAPITAL FEMORAL
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SLIPPED CAPITAL FEMORAL
EPIPHYSIS
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TYPE II (Above physis)
Shearing force splits the epiphyseal plate. The line of fracture passes across the epiphyseal
plate and extends through the metaphysis. This
separates a triangular metaphyseal fragment
known as Thurston Holland fragment (Corner sign) This type is the most common, seen in 73 75% of
cases.
Commonly seen in distal radius (33 50%), distal
tibia & fibula, phalanges. It is treated by closed reduction and immobilization
The prognosis is good and complications are
uncommon. However, it may result in minimal
shortening
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TYPE II (CONTD)
Salter Harris type II of the distal radius There is also a
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Salter Harris type II of the distal radius. There is also a
fracture of the distal ulna
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TYPE III (Lower than physis)
This is an intraarticular fracture, often occurringafter partial closure of physis
The line of fracture is vertically/obliquely through
the epiphysis and extending horizontally to
periphery of physis. Seen in 6.5 8% of cases.
Commonly seen in distal tibia, distal phalanx, rarely
distal femur
The prognosis is fair. This type damages theproliferative and resting zones of the growth plate
with fracture extending to articular surface of the
bone.
Treatment often requires surgery.
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TYPE III (CONTD)
Salter Harris type III of distal
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Salter Harris type III of distal
tibia
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TYPE IV (Through physis)
This is also an intraarticular fracture. The line of fracture passes directly through the
metaphysis, epiphyseal plate and through the
epiphysis
Seen in 10 12% of cases. Commonly seen in lateral condyle of humerus and
distal tibia
The prognosis is guarded. This type interferes with
the germinal layer and can cause premature focalfusion of involved bone thereby causing limb
shortening.
Treatment requires surgery in order to properly
realign the joint surface
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TYPE IV (CONTD)
Salter Harris t pe IV of the distal
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Salter Harris type IV of the distal
tibia
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TYPE V (Rammed physis)
This type is due to crush injury with injury to thevascular supply.
Crush injury does not displace the growth plate but
damages it by direct compression.
Commonly found in distal femur, proximal tibia,distal tibia
Seen in
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TYPE V (CONTD)
Salter Harris type V of right distal radius. There is a "sclerotic" band
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across the distal metaphysis of the right radius where the impaction has
taken place, and a small area of bulging on the ulnar aspect of the distal
radius
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CLINICAL FEATURES
Joint pain Joint swelling
Limited range of motion in joint
Point tenderness over the growth plate
IMAGING MODALITIES Plain radiography
CT scan MRI
Ultrasound
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PLAIN RADIOGRAPHY
This is the sole imaging method required in themajority of epiphyseal injuries.
AP and lateral views are usually required.
Comparison study of contralateral limb is also
done. The epiphyseal plate is originally radiolucent. So,
its fractures are not directly evident on plain x-rays.
Fractures through the bones appear as linear
radiolucency (area of discontinuity) within the bony
outlines
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CT SCAN
CT with its multiplanar reconstruction is required todemonstrate improved fracture anatomy for
potential surgical intervention
The fracture appears as linear hypodense area
within the hyperdense bony outline
MRI SCANThe fracture appears as focal hyperintense linear
area (line of cleavage) within a hypointense physis
on T1 and T2 images
CT scan of the right knee (volume rendering images)
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C sca o e g ee ( o u e e de g ages)
showing Salter-Harris type 2 supracondylar fracture of the
right femur
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ULTRASOUND
It is useful as ancillary imagingmodality in assessing joint effusion,
ligamental rupture, vascular injury etc
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COMPLICATIONS
Progressive angular deformity Limb length discrepancy from growth arrest
Articular incongruity from disruption of articular
surface
Bone infarction in metaphysis/epiphysis
TECHNIQUE OF RADIOISOTOPE
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SCANNING OF PULMONARY
EMBOLISM
Definition
Contraindications
Radiopharmaceuticals
Equipment
Patient preparation
Technique
Aftercare
Complications
DEFINITION
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DEFINITION
Radioisotope scanning of pulmonaryembolism is otherwise known as ventilation-
perfusion scintigraphy
It is a non-invasive technique for the
assessment of the distribution of pulmonary
blood flow and alveolar ventilation.
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RADIOPHARMACEUTICALS
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RADIOPHARMACEUTICALS
Perfusion imaging This method demonstrates the distribution of lung
perfusion using a 99mTc (Technetium)-labelled
albumin tracer in the form of small particles. Adult
dose is about 40 000 - 200 000 particles The particles are of such a size (about 10 40m
in diameter) that they will be trapped in the
precapillary arterioles of the lung in their first
passage after intravenous injection. The injectedparticles occlude less than 0.5% of the vascular
bed.
After trapping in the lung, the particles are removed
by the reticuloendothelial system over several
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RADIOPHARMACEUTICALS (CONTD)
Ventilation imaging
81mKr (Krypton) gas: Optimal imaging agent. It
has a short T of 13s and gamma-energy of
190keV. Simultaneous dual isotope
ventilation and perfusion imaging is possiblebecause of different energy to 99mTc. However,
it is expensive and not readily available.
99mTc-Technegas: Similar diagnostic efficacy
to krypton. Simultaneous imaging notpossible. It is expensive.
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RADIOPHARMACEUTICALS (CONTD)
Ventilation imaging
99mTc-DTPA: Cheap and readily available.
Simultaneous imaging is not possible. Less
suitable in patients with COPD or chronic
asthma due to likelihood of clumping ofaerosol particles
133Xe (Xenon) gas: It has a long T of
5.25days and a gamma energy of 81keV.
Ventilation must precede perfusion studybecause low gamma-energy would be
swamped by scatter from 99mTc. Its images
are of poor quality.
Q
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EQUIPMENT
Gamma-camera Low-energy general purpose collimator
Gas-dispensing system and breathing circuit for
ventilation
PATIENT PREPARATION For ventilation, familiarization with breathing
equipment
A current CXR is required to assist with
interpretation.
TECHNIQUE
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TECHNIQUE
Perfusion scintigraphy This method demonstrates the distribution of lung
perfusion using a 99mTc-labelled albumin tracer inthe form of small particles.
The tracer is given intravenously in the supine,
semi-recumbent or sitting position The syringe is shaken to prevent particles settling.
A slow IV injection is given directly into a vein overabout 10s. The patient must remain in position for
2-3mins while the particles become fixed in thelungs
Imaging may begin immediately, preferrably in thesitting position
TECHNIQUE (CONTD)
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TECHNIQUE (CONTD)
Ventilation Scintigraphy If81mKr gas is used, simultaneous Q/V imaging
can be performed either by dual isotope
acquisition or swapping energy windows at each
patient position. The patient is positioned to obtain identical views
to the perfusion images and asked to breathe
normally through the mouthpiece
The air supply attached to the generator is turnedon and imaging commenced.
TECHNIQUE (CONTD)
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TECHNIQUE (CONTD)
Ventilation Scintigraphy
If99mTc-DTPA is used, this imaging is performed before theperfusion study.
99mTc-DTPA is drawn into a 5ml syringe with 2ml air, theninjected into the nebulizer and flushed through with air
The patient is positioned sitting with their back to the camera
The air supply is turned on to deliver a rate of 10L/min and anose-clip is placed in the patient, who is asked to breathenormally through the mouthpiece
After reaching a sufficient count rate, the air supply is turnedoff. The patient continues to breathe through the
mouthpiece for a further 15s The nose-clip is removed and the patient is given a mouth
wash, then imaging is commenced.
TECHNIQUE (CONTD)
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TECHNIQUE (CONTD)
The images taken include anterior, posterior, leftand right posterior obliques. These are preferred to
lateral views in order to avoid small defects in one
lung being obscured by counts shining through
from the opposite lung.
Characteristically, pulmonary embolism results in
severe reduction or total loss of perfusion to the
areas of lung supplied by the affected arteries,
while ventilation remains unchanged or shows only
a minor reduction.
AFTERCARE
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AFTERCARE
None
COMPLICATIONS Worsening of right heart failure in patients
with severe pulmonary hypertension
Risk of systemic embolisation in patientswith right-to-left cardiac shunt
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