2. BONE SCAN - Chest Imaging(2010)
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Transcript of 2. BONE SCAN - Chest Imaging(2010)
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BONE ISOTOPE SCAN
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Introduction
Bone scan is one of the most commonly
performed procedures in nuclear
medicine.
Bone scan often provides an earlier
diagnosis and demonstrates more lesions
than are found by radiographic
procedures.
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Sensitivity and Specificity
Bone scan is very sensitive study but it is
not specific.
Although findings on bone scan are non-
specific, its monostotic or polyostotic
status and anatomical distribution can
provide important clues to the differential
diagnosis.
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Radiopharmaceuticals
They are bone seeking agents.
They are labeled with Tc99m.
They are phosphate analogs. Most commonly used one is HDP
(Hydroxy Methylene Diphosphonates).
They are given intravenously.
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Mechanism of Localization
Phosphate groups bind to the hydroxyapatite
[Ca3(Po4)2] structure of bone tissue by a
mechanism called chemisorption.
The hydroxyapatite structure of the bone isexposed during bone remodeling. So, more
radiopharmaceutical will deposit in that region
giving hot area.
50-60% of injected dose localized on bone,
remain dose is cleared by kidneys.
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Whole body bone scan
This is the bony phase of bone scan.
Inject radiopharmaceutical and image in
2-4 hours.
When we say bone scan, we usually
mean whole body bone scan.
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Three Phase Bone Scan
It is done to see if there is soft tissue
hyperemia.
First phase is the perfusion phase or
vascular phase.
Second phase is the blood pooling phase
or soft tissue phase.
Third phase is the bony phase.
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First Phase
30-60 dynamic images are usually
obtained over 1 minute immediately after
injection.
This is radionuclide angiography and gives
an idea about the local vasculature. During
the first minute after injection, injected
dose is still intravascular.
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Perfusion
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Second Phase
Static image is obtained in 5 minutes after
dose injection.
Within 5 minutes post injection,
radiopharmaceutical moves from
intravascular space to extravascular space
(soft tissue). It gives idea about soft tissue
edema.
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Blood Pool
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Hyperemia
If there is focal increased activity in
the first and second phases,
hyperemia or acute inflammatoryprocess is present.
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Third Phase
It is the bony phase image obtained in
2-4 hours post injection.
It is the same as whole body bonescan.
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Clinical Applications
Malignancy
1- Primary bone cancer
2- Secondary metastatic bone disease
Osteomyelitis
Stress fractures
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Primary Bone Malignancy
(Sarcomas)
MRI provides more exact information
regarding tumor extent, particularly in soft
tissue. So, bone scan is not a diagnosis
image in primary bone tumors.
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Bone sarcomas-cont..
Bone scan is a staging and restaging
image in bone sarcomas. It is performed to
see if there is bone metastatic disease
(bone to bone).
40 50% of patients with either Ewings
sarcoma or osteosarcoma develop
osseous metastases within 2 years ofpresentation.
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Metastatic Bone Disease
Bone scan is an extremely important tool
in decision making during management of
cancer patients.
Any cancer potentially could cause bone
metastatic disease.
However, prostate, breast and lung
cancers have propensity to metastasize to
bone.
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Metastatic Bone Disease and
Bone Pain
About 80% of patients with known cancer
and bone pain have metastases
documented by bone scan.
30 50% of patients with metastatic bone
disease do not have bone pain.
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Metastatic Bone Disease and
Image Findings
The hallmark of metastatic bone
disease is multiple foci of increased
osteoblastic activity in bony skeleton.However, single lesion could be also
metastatic.
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Stress Fractures
It is often difficult to visualized on a plain
radiograph.
Fractures may be identified by bone scan
as early as 24 hours after occurrence.
3-phase bone scan is usually done.
There is hyperemia and osteoblastic
process (three phases are positive).
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Stress Fracture
Blood Pool
Anterior Posterior
Anterior Posterior Left Lat Right Lat
Left Lat Right Lat
2 hour delay
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Stress Fracture
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Acute Osteomyelitis
Early plain radiography signs of
osteomyelitis are non-specific.
3-phase bone scan is usually theprocedure of choice to differentiate
between osteomyelitis and cellulitis.
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Acute Osteomyelitis-cont..
If first and 2nd phases are positive
(hyperemia) with normal third phase,
diagnosis would be cellulitis. In acute osteomyelitis all 3-phases
are positive (hyperemia and
osteoblastic process in the bone).
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Perfusion
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Blood Pool
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Whole BodyBone Scan