Transcript Bone Physiology - Hussein Farghaly

SKELETAL RADIONUCLIDE
IMAGING
III
Dr. Hussein Farghaly
Nuclear Medicine Consultant
PSMMC
CONTENTS
• Bone and BM physiology & anatomy
• Bone scan
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Radiopharmaceutical,
preparation,
uptake and pharmacokinetics
dosimetry,
protocols,
• normal and altered distribution
• Clinical indication and Skeletal pathology
• Bone Marrow scan
Soft-tissue uptake in radionuclide musculoskeletal imaging
HOME WORK
CLINICAL USES OF SKELETAL SCINTIGRAPHY
Metastatic Disease
The evaluation of osseous metastatic disease is the most common use of skeletal scintigraphy.
Metastatic Disease, cont.
Patients may present with bone pain (50–80%) and elevated
alkaline phosphatase (77%) but these findings are nonspecific.
Bone scan may be used for staging, restaging, and monitoring
therapy effectiveness. T
The decision on which patients will need a bone scan depends on
factors such as the type and stage of tumor, history of pain, and
radiographic abnormalities.
Over 90% of osseous metastasis distribute to the red marrow. In
adults red marrow is found in the axial skeleton and the proximal
portions of the humeri and femurs.
Metastatic Disease, cont.
As the tumor enlarges, the cortex becomes involved. The body
responds by attempts at repair.
The Tc-99m MDP binds to these regions in areas of bone
deposition. Therefore, scans image the bone response to the tumor
and not the tumor itself.
Even a 5% bone turnover can be detected by bone scan.
Radiographs, on the other hand, require a minimum mineral loss
of a 50% before a lesion is visualized. MRI is more sensitive than
bone scan because signal changes in the marrow from the tumor
can be visualized directly. However whole body MRI is not
widely available and generally not practical at this time.
Metastatic Disease, cont.
Metastatic Disease in Specific Tumors
Prostate Carcinoma:
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Until the introduction of the prostate specific antigen (PSA) blood test, bone scan was
considered the most sensitive technique for detecting osseous metastasis.
Serum alkaline phosphates measurement detects only half the cases detected by
scintigraphy.
Radiographs may be normal 30% of the time.
The likelihood of an abnormal scintigram correlates with the clinical stage, Gleason score,
and PSA level.
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Incidence of bone metastasis
less than 5%
early stage I disease,
10% in stage II
20% in stage III
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In patients with PSA levels less than 10 ng/ml, bone metastases are rarely found (<1% of
the time). Skeletal scintigrams are still indicated for symptomatic patients and for
evaluation of suspicious areas seen radiographically.
With increasing PSA levels, the chance of detecting metastatic disease increases.
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• Breast Carcinoma:
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Mean survival is only 24 months among those with confirmed bone disease.
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Like prostate cancer, stage of disease correlates with the incidence of osseous
metastases on bone scan:
0.5% in stage I,
2–3% in stage II,
8% in stage III,
and 13% in stage IV.
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Bone scans are not generally performed in patients with stage I or II disease.
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Although skeletal scintigraphy has a high sensitivity for breast carcinoma, it may not
detect all lesions, such as those contained in the marrow or more lytic lesions.
• Lung Carcinoma
• There is no complete agreement on when to use skeletal
scintigraphy.
• Staging is generally done with CT, surgery (including
mediastinoscopy and video-assisted thoracoscopic surgery
• [VATS]), and increasingly with F-18 FDG PET.
• Skeletal scintigraphy is useful in a patient who develops pain
during or after treatment and helpful in planning radiation
therapy.
• However, it appears less useful in cases of local and mediastinal
invasion or with advanced disease where therapy will be
palliative.
• Solitary Lesions
• The chance that a solitary lesion is due to malignancy varies by
location .
• Focal rib uptake is likely due to fracture, whereas uptake
• extending along the rib is likely tumor.
• Common benign causes for a solitary focus of uptake :
arthritis and trauma.
benign bone lesions (enchondroma, osteoma, fibrous dysplasia)
osteomyelitis,
monostotic Paget’s
• Multiple focal lesions:
• Is the classic pattern of metastatic disease in the skeleton
• Although this typical pattern provides a high degree of
clinical certainty as to the diagnosis, several other
etiologies can also have multiple areas of uptake
These must be differentiated from osseous metastasis
Differential Diagnosis of Multiple Focal Lesions:
The key is to recognize the different features and patterns of these other etiologies.
Final diagnosis may depend on correlation with anatomical imaging.
Osteoarthritic changes:
Location: medial compartment of the knee, hand, and wrist (especially at the
base of the first metacarpal), shoulder and bones of the feet.
Bilateral: and on both sides of the joint.
Patella: The patella frequently shows increased uptake due to chondromalacia
and degenerative change.
Spine degenerative changes:
are more problematic because both metastasis and arthritic changes occur in the
same location. SPECT may localize a lesion to the pedicle that is the typical
location of metastasis. A bone scan lesion in the central vertebral body and disc
space, could be degenerative or malignant and may require short term follow up,
CT or even MRI.
Differential Diagnosis of Multiple Focal Lesions cont.:
• TRUMA:
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The findings of trauma can mimic the
appearance of metastasis. Patients should be
closely questioned for any history of trauma.
In the ribs, a vertical alignment of focal
abnormal uptake in several or successive ribs
is classic for trauma.
The nonrandom pattern is not expected in
metastatic disease.
A metastatic lesion tracks along the bone
rather than remaining focal.
Radiographic correlation may show the
cortical disruption or callous formation.
Because bone scan frequently detects fractures
not seen on radiographs, correlation with CT
or short-term follow-up bone scan may be
needed if no fracture is seen on the
radiograph. Persistently positive skeletal
Typical appearance of rib fractures. A, Posterior views of the chest reveal
activity from old trauma poses another
focal uptake in a vertical alignment in the right lower ribs and a recent left
interpretive problem.
nephrectomy with resection of some lower left ribs. B, A follow-up study 18
months later shows resolution of the right rib uptake as the fractures healed.
Differential Diagnosis of Multiple Focal Lesions cont.:
• A number of other etiologies can cause multifocal abnormalities:
-Infarctions in sickle cell anemia can cause multiple areas of increased and
decreased uptake.
- Cushing’s disease and osteomalacia, for example, frequently cause
disproportionate rib lesions as compared with other areas.
- Osteoporosis may result in dorsal kyphosis and classic fractures such as the
vertebral insufficiency fractures and the H-type fracture of the sacrum.
- Paget’s disease may be differentiated from metastasis by an expansion of
the bone and classic locations.
Flare Phenomenon
• Another potentially perplexing pattern is seen in some bone scans
done on patients undergoing cyclical chemotherapy.
• When a patient has a good response to chemotherapy, the bone
scan may paradoxically worsen, with a “flare” of increased
activity.
• To add to the confusion, these patients may experience increased
pain. If these lesions are followed radiographically, increased
sclerosis is seen over 2–6 months because this is an osteoblastic
response as the bone begins to heal.
• This is the same time frame that the bone scan typically shows
increased uptake. The flare phenomenon reinforces the fact that
tracer uptake is not in the tumor but rather in the surrounding
bone.
Superscan
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A superscan is intense symmetric activity in the bones with diminished renal and soft tissue
activity on a Tc99m diphosphonate bone scan
This appearance can result from a range of aetiological factors:
• diffuse metastatic disease
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prostatic carcinoma
breast cancer
transitional cell carcinoma (TCC)
multiple myeloma (some difference in opinion)
lymphoma
• patchy uptake nonetheless : look at skull and ribs
• tends to somewhat spare the distal skeleton
• metabolic bone diseases
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– renal osteodystrophy
– hyperparathyroidism 1 (often secondary hyperparathyroidism)
– osteomalacia
• will involve distal skeleton
• smoother uptake
myelofibrosis / myelosclerosis
mastocytosis
wide spread Paget's disease
Metastatic superscan
Renal osteodystrophy. A–B,The absence of soft tissue uptake is striking with an
appearance similar to the “superscan”seen in metastatic disease. The prominent rib end activity may
help differentiate the two etiologies. The native kidneys had failed,and a renal transplant is noted in the
right iliac fossa. C, Increased activity in the skull and sternum may be especially prominent. Note the
increased axial skeletal uptake and paucity of soft tissue background activity.
Superimposed appearances of metastatic and metabolic superscan
Differentiation between metastatic and metabolic superscan
HOME WORK