Download NM 4203 Scanning & Imaging

NM 4203
Scanning & Imaging
Skeletal System
Anatomy & Physiology of Bone
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Normal cortical bone is water, organic matter (collagen, ground
substance, cellular elements) and inorganic matter (bone mineral)
Bone salt mineral (inorganic matters) is composed of calcium,
phosphate, and hydroxyl, carbonate, citrate, sodium, magnesium,
potassium, chloride and fluoride.
Crystalline lattice structure
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hydroxyapatite
Skeleton performs several functions:
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Support
Protection
Movement
Blood formation
Anatomy & physiology of Bone
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Bone is metabolically active tissue with
nutrients being exchanged between blood
and bone.
Main difference between bone and other
connective tissue is that it is calcified.
Anatomy &
Physiology of Bone
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Skeleton has two parts:
Axial: skull, spine and
thoracic girdle
 Appendicular: upper
extremities, pelvis and
lower extremities
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Gross Structure of Bone
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Skeletal system contains 206 bones
Tubular Bones
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Short Bones
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Wrist (carpals), ankle (tarsals), sesamoids
Flat Bones
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Humerus, radius, ulna, femur, tibia and fibula
Metacarpals, metatarsals, and phalanges
Ribs, sternum, scapulae, several skull bones
Irregular Bones
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Spine, pelvis, some bones in skull
Radiopharmaceuticals
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Can be analogs of calcium, hydroxyl
groups, or phosphates
First 99mTc phosphate complex for bone
imaging was introduced in 1971.
Most widely used: Technetium based
methylene diphosphonate (MDP)
18F FDG with PET imaging
Accumulation
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The mechanisms for bone accumulation of
imaging agents are not completely understood.
It is probably related to the exchange of the
phosphorus groups onto the calcium of
hydroxyapatite.
Calcium analogs or phosphate compounds have
a low concentration in blood and tissue.
99mTc phosphate will also show renal activity ~
these agents are excreted through the urinary
tract.
Kit Preparation
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Air should not be mixed into the kit vial
during preparation. This oxidation would
cause poor tagging.
If injected over 4 hours after preparation,
thyroid and gastric activity may be seen.
Patient Preparation
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No prep before exam
Following injection, they should be well
hydrated to help with clearance from soft
tissue.
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4-6 glasses of liquid is adequate
They should be encouraged to void frequently
to reduce radiation dose to bladder.
Common Reasons for
Bone Scanning
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Detection or follow-up of metastatic disease (breast,
prostate or lung cancer)
Differentiate between osteomyelitis and cellulitis
Determine bone viability (infarct or avascular necrosis
Evaluate fractures
Evaluate prosthetic joints for loosening or infection
Evaluate bone pain
Evaluate finding on CT or Radiograph
Increased alkaline phosphatase
Technique
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Inject 10 – 25 mCi of Technetium based
radiopharmaceutical (usually MDP)
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Acquire blood flow and pool if needed
Image 2-4 hours later
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Pt. should be well hydrated during the wait time to
help with soft-tissue clearance.
Pt. should void immediately prior to imaging
Spot views or whole-body imaging
SPECT may help improve lesion or fracture
localization
Three-Phase
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Blood Flow
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Blood Pool
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Static image obtained for 300,000-500,000 counts
Delay
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2-4 second images for 40-60 seconds
2-4 hours after injection (5 + hrs. for osteomyelitis of feet)
300,000-500,000 count static images
100,000 counts image should be done if 4th phase is needed
4th phase: acquired 24 hours later
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100,000 counts to compare to previous day
SPECT
Single Photon Emission Computed Tomography
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Pelvis, spine, TMJ, facial bones, knees
Detector to patient distance should be minimal
30-45 minutes
Single head camera 64X64 matrix
Newer cameras can use 128X128 matrix
Large number of views 120 – 128 in 360 degrees
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These parameters give very high counts and very high resolution
Reconstructed images include transverse, coronal and
sagittal slices
Instrumentation
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Anger scintillation camera
High-resolution collimator
Multiple, individual static images should be
taken for equal amounts of time.
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Allows for comparison of image densities.
Normal Scan
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Children: areas of growth (epiphyses) show intense
uptake
Adults:
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Increase in nasopharynx
Skull may be patchy
Maxillary or mandibular activity due to dental disease
Increase in lower cervical spine and knees due to degenerative
changes
Anterior view: prominent sternum, sc joints, ac joints, shoulders,
iliac crests and hips show increase in activity.
Posterior view: thoracic spine, si joints and tips of scapulae are
prominent
Any asymmetric activity is suspicious
Causes for Increased Activity
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Primary bone tumor
Metastatic Disease
Osteomyelitis
Trauma (fracture, postsurgical)
Loose prosthesis
Degenerative or arthritic changes
Osteoid osteoma
Paget’s Disease
Generalized increased bone activity
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Superscan
(no renal activity seen)
Hyperparathyroidism
Renal osteodystrophy
Diffuse metastases
Hematologic disorders
Poor scan
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Decreased cardiac output
Renal failure
Extravasation of radiopharmaceutical
during injection
Kit breakdown
Metastatic Disease
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30-50% of patients with metastases do not have pain
Tumors that are more likely to spread to bone: breast,
lung and prostate
Tumors with low rates of bone metastases: colon, cervix,
uterus, head and neck
Most metastases are seen in multiple areas. (exception is
single sternal lesion in breast cancer pt.)
PSA (prostate-specific antigen): less than 10-15 ng/mL =
likelyhood of positive bone scan with metastases is low.
Cold lesions: extremely aggressive tumor, decreased
blood supply, or significant marrow involvement.
Osteogenic Sarcoma
Osteosarcoma is a
bone-forming lesion
 Appearance varies
widely depending on
the vascularity and
aggressiveness of the
tumor.
 Increased activity is usually intense and often
patchy with photopenic areas.
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Ewing’s Sarcoma
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Relatively common bone tumor
Occurs mostly in pelvis or femur
Activity is intense and homogeneous.
Tumor is very vascular
40-50% of patient’s with Ewing’s sarcoma or
osteosarcoma develop metastases within 2
years. Follow-up bone scans are recommended.
Trauma
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Bone scan appearance of Fractures:
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Acute: 3-4 weeks~generalized diffuse increase around fracture
site
Subacute: 2-3 months~activity more localized and intense
Healing phase: longer period ~gradual decline in intensity
Early increase in activity is a result of hyperemia and
inflammation.
Repair begins within a few hours and reaches maximum
in 2-3 weeks.
Age: has been found to be a minor variable. However,
about 3 days are needed to detect occult hip fracture in
elderly patients.
Avascular Necrosis
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Involving the hip
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Usually due to trauma
Decrease in blood flow and
blood pool
Decreased activity on
delay images
MRI can also be done for this
Stress Fractures
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Not visualized for 7 to 10 days on radiograph.
Can be seen on a radionuclide bone scan about
24 hrs. after onset of pain.
Stress fractures: increased blood flow and
pool~delay tends to image as a focal hot spot.
Shin splints: normal blood flow and blood
pool~delay shows linear increased activity along
posteromedial tibial cortex.
Child Abuse
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Rib and thoracic spine fractures are a
strong indication of physical abuse.
Osteomyelitis, Cellulitis &
Septic Arthritis
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Radiopharmaceuticals:
99mTc –diphosphonate
67Ga citrate
111In labeled leukocytes
99mTc labeled leukocytes
Cellulitis: increased blood flow and blood pool, no focal
area of increase on delay.
Osteomyelitis: increased blood flow and blood pool, with
focal increased area on delay. Usually only on one side of
a joint.
Septic Arthritis: increased activity in all three phases.
Involved both sides of the joint.
Paget’s Disease
Intense increase in activity due to
increased regional blood flow.
 Usually conforms to the shape of the
involved bone.
 Notable expansion or
enlargement of the
bone.
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Reflex Sympathetic Dystrophy
(RSD)
Usually prior trauma, myocardial
infarction, or neurologic abnormality.
 Increased blood flow and
blood pool to affected limb,
increased asymmetric
periarticular activity around
all joints of hand or foot.
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Bone Marrow Imaging
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Radiopharmaceutical: 99mTc sulfur colloid
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Localizes in marrow because the particles are
phagocytized by RES cells in the marrow.
Intense liver and spleen activity must be
covered with a lead shield.
MRI usually done
Joint Imaging
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Evaluate inflammatory joint disease
Radiopharmaceuticals:
 99mTc
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pertechnetate
99mTc phosphate compounds (most sensitive
for knee or sacroiliac inflammatory disease)
Can detect disease before radiographs
Therapy of Painful Bone Metastases
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Lesions that are unresponsive to radiotherapy or
chemotherapy.
Usually men with prostate cancer
For pain management (not a cure)
Increase in pain 2-3 days after treatment and
can last several days.
Pain improvement starts at 7-20 days after
treatment and can last 3-6 months.
Routine bone scan is done first to ensure there
will be bone uptake.
Therapy of Painful Bone Metastases
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Radiopharmaceutical: Strontium-89 chloride (Metastron)
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Depresses the bone marrow and should not be used if leukocyte or
platelet count is low.
Typical dose is 40-60 uCi / kg : up to 4mCi
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Decays by beta-emission
Half-life 50.6 days
Slow 1-2 minute injection using plastic shielding
Should not be given to patients with life expectancy less than 3
months. Patients cannot be cremated in many states.
Cost : $3000 + (cost effective compared to radiation therapy,
chemotherapy, and analgesic pain medication
Therapy of Painful Bone Metastases
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Other Radiopharmaceuticals:
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Rhenium-186 HEDP ~not approved in the
U.S., but widely used in Europe
Samarium-153 EDPMT (Quadramet)
Short half-life of 46 hours
 In addition to beta emission, also has a gamma
emission that can be imaged
 Usually scanned 6 hrs after administered
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