Imaging Techniques in Clinical Practice
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Questions and Answers

What is the most common reason for a Superscan in bone imaging?

  • Metastases from carcinoma of the prostate (correct)
  • Radiation therapy to the spine
  • Osteogenic Sarcoma
  • Normal skeletal activity
  • What is the main reason for minimal renal or bladder activity in bone imaging with 99mTc-MDP?

  • Accumulation of radionuclide in the metastases (correct)
  • Normal bladder function
  • Presence of osteogenic sarcoma
  • Radiation therapy defects
  • In the context of bone imaging, what do decreased activity in multiple contiguous vertebral bodies on a PET scan indicate?

  • Normal skeletal activity
  • Presence of prostate carcinoma metastases
  • Osteogenic sarcoma metastases
  • Radiation therapy effects (correct)
  • What is the radiographic feature seen in the proximal tibia of a teenager with Osteogenic Sarcoma?

    <p>Mottled sclerosis and periosteal reaction</p> Signup and view all the answers

    Which type of skeletal involvement is typically seen in a Superscan during bone imaging?

    <p>Involvement of entire axial and proximal appendicular skeleton</p> Signup and view all the answers

    Why would there be minimal bladder or renal activity identified in a bone scan?

    <p>Metastases have accumulated most of the radionuclide</p> Signup and view all the answers

    What is the primary cause of increased activity seen on a bone scan?

    <p>Osteogenic Sarcoma</p> Signup and view all the answers

    How can one differentiate between radiation therapy defects and metastases on a PET scan?

    <p>'Cold spots' indicate radiation therapy effects, not metastases</p> Signup and view all the answers

    In bone imaging, what does 'mottled sclerosis and periosteal reaction' suggest?

    <p>Presence of Osteogenic Sarcoma</p> Signup and view all the answers

    Why is it important to differentiate between radiation therapy defects and metastases in PET scans?

    <p>To prevent unnecessary treatment for metastases</p> Signup and view all the answers

    What is the reason for minimal renal or bladder activity identified in bone imaging with 99mTc-MDP?

    <p>Accumulation of radionuclide by osteoblastic metastases</p> Signup and view all the answers

    What is the predominant skeletal involvement seen in a Superscan during bone imaging?

    <p>Diffuse osteoblastic metastases</p> Signup and view all the answers

    Why does a patient with radiation therapy to the spine exhibit decreased activity in multiple contiguous vertebral bodies on a PET scan?

    <p>Normal skeletal activity response to radiation</p> Signup and view all the answers

    In bone imaging, what does mottled sclerosis and periosteal reaction suggest?

    <p>Osteogenic Sarcoma involvement</p> Signup and view all the answers

    What is the common outcome of a bone scan when a Superscan is observed?

    <p>'Overwhelming' skeletal uptake of radioisotope</p> Signup and view all the answers

    How can one differentiate a radiation therapy defect from metastases on a PET scan?

    <p>'Superscan' pattern suggests radiation therapy defect</p> Signup and view all the answers

    'Osteogenic Sarcoma' involves which feature based on the provided text?

    <p>'Mottled sclerosis and periosteal reaction'</p> Signup and view all the answers

    'Posterior fluorine-18 sodium fluoride positron emission tomography (PET) scan image' indicates involvement primarily in which region?

    <p>'Axial skeleton'</p> Signup and view all the answers

    'Sagittal and coronal PET/computed tomography scans of the spine' assist in identifying defects due to what cause?

    <p>'Radiation Therapy'</p> Signup and view all the answers

    In Superscan during bone imaging, there is involvement of the entire axial and proximal appendicular skeleton. Diffuse osteoblastic metastases are typically seen from carcinoma of the ______.

    <p>prostate</p> Signup and view all the answers

    Radiation therapy to the spine can result in decreased activity in multiple contiguous vertebral bodies on a PET scan, which may be mistaken for metastases. These defects are actually due to the radiation therapy, not the presence of ______.

    <p>metastases</p> Signup and view all the answers

    Osteogenic Sarcoma often presents with mottled sclerosis and periosteal reaction in the proximal ______ of a teenager.

    <p>tibia</p> Signup and view all the answers

    A bone scan can show increased activity in areas affected by Osteogenic Sarcoma, indicating the presence of ______.

    <p>tumor</p> Signup and view all the answers

    In bone imaging with 99mTc-MDP, minimal renal or bladder activity is identified because the metastases have accumulated most of the ______.

    <p>radionuclide</p> Signup and view all the answers

    Study Notes

    Bone Scanning

    • Bone scanning is widely used for evaluating various benign and malignant diseases affecting the skeletal system.
    • It provides an earlier diagnosis and detects more lesions than planar radiographic procedures.
    • The presence of a lesion on a bone scan is non-specific, but its monostotic or polyostotic status and anatomic distribution can provide important clues for differential diagnosis.

    Anatomy and Physiology

    • Bone is composed of an inorganic mineral phase of crystals bound to protein, largely collagen.
    • Normal bone is in a constant state of remodeling, which may be accelerated by pathologic conditions such as fractures, infections, bone tumors, or metastases.
    • The skeleton is composed of two parts: axial (skull, spine, and shoulder girdle) and appendicular (upper extremities, pelvis, and lower extremities).

    Radiopharmaceuticals

    • Bone-seeking radiopharmaceuticals are analogs of particular components of the mineral portion of bone, such as hydroxyapatite, calcium, hydroxyl groups, or phosphates.
    • The most widely used radiopharmaceuticals are technetium-labeled diphosphonates (99mTc-MDP), which distribute in the skeleton based on differences in regional perfusion and bone turnover.
    • Fluorine-18 sodium fluoride (18F-NaF) is a positron emission tomography (PET) imaging agent that has higher first-pass extraction efficiency and a more favorable bone-to-background tissue ratio than 99mTc-MDP.

    Technique

    • Planar scans are performed 2-4 hours after injection of the radiopharmaceutical, while single-photon emission computed tomography (SPECT) and PET/CT scans are performed 1-2 hours after injection.
    • A three-phase study is performed in patients suspected of having osteomyelitis or cellulitis, which includes a radionuclide angiogram, initial blood pool image, and routine images.
    • SPECT imaging is useful for detecting skeletal lesions in patients with specific regional complaints and may establish or better localize an abnormality suspected on routine planar images.

    Normal Scan

    • A normal scan varies in appearance between children and adults.
    • In children, areas of growth in the region of the epiphyses show intense radionuclide accumulation.
    • In adults, the quality of the bone scan can be related to age, and older patients may have a higher proportion of poor-quality scans.

    Clinical Applications

    • Bone scanning is useful for detecting and following skeletal metastases, differentiating between osteomyelitis and cellulitis, determining bone viability, and evaluating fractures difficult to assess on radiographs.
    • Whole-body bone scanning is able to survey the entire skeleton on a single study and can demonstrate metastatic lesions much earlier than radiography.
    • 18F-NaF PET imaging has higher sensitivity and specificity than 99mTc-MDP planar bone imaging for detecting skeletal metastases.### Tumors and Bone Metastases
    • Multiple myeloma is characterized by lytic lesions with decreased vascularity and low osteoblastic activity, making bone-seeking radiopharmaceuticals have a low sensitivity (50% false-negative rate)
    • 18F-fluorodeoxyglucose (FDG) has higher sensitivity for lytic lesions and early detection of marrow metastases
    • 80% of patients with known neoplasms and significant bone pain have metastases documented by bone scan
    • 30% to 50% of patients with metastases do not have bone pain, so it is recommended to scan patients with asymptomatic tumors that have a propensity to metastasize to bone (e.g., breast, lung, and prostate)

    Interpreting Bone Scans

    • A single lesion is often secondary to benign disease, especially in a rib
    • Multifocal areas of increased activity in noncontiguous ribs are likely metastatic disease
    • In the spine, multiple foci of linear activity in the vertebral bodies suggest osteoporotic fractures, while lesions extending into the posterior elements or involving the vertebral pedicle are likely metastatic
    • Distribution of lesions in multifocal metastatic disease: thorax and ribs (37%), spine (26%), pelvis (16%), limbs (15%), and skull (6%)

    Bone Metastases and Treatment Response

    • Follow-up bone scans to assess response in patients undergoing treatment for advanced breast and prostate cancer should be interpreted with caution
    • 18F-FDG measures tumor metabolism, which decreases with treatment success, while bone-seeking tracers may provide an indirect indication of tumor improvement through repair of adjacent bone
    • The "flare phenomenon" is a favorable response to chemotherapy, characterized by increased uptake at involved sites, which can give a false impression of new lesions

    Other Causes of Cold Lesions on Bone Scan

    • Localized overlying attenuation artifact caused by pacemaker, barium, etc.

    • Instrumentation artifact

    • Radiation therapy

    • Infarction

    • Early aseptic necrosis

    • Osseous metastases from neuroblastoma, renal cell carcinoma, thyroid carcinoma, anaplastic tumors, etc.

    • Generalized diseases such as primary or secondary hyperparathyroidism### Bone Scan Technique

    • 10 to 20 mCi (370 to 740 MBq) of technetium diphosphonate radiopharmaceutical is injected intravenously for routine planar scans.

    • Patient is imaged 2 to 4 hours later, with site of injection recorded.

    • Injection site should be distant from suspected osseous pathology to avoid false positives.

    • Even slight extravasation of isotope at injection site can cause a focus of increased soft-tissue activity.

    Normal Bone Scan

    • In children, areas of growth in the region of epiphyses show intense radionuclide accumulation.
    • In adults, quality of bone scan can be related to age, with older patients typically having poorer-quality scans.
    • Skull, sternum, sternoclavicular joints, acromioclavicular joints, shoulders, iliac crests, and hips are usually well-visualized.
    • Increased activity in knees is common in older patients due to arthritic changes.

    Clinical Applications

    • Detection and follow-up of skeletal metastases
    • Differentiation between osteomyelitis and cellulitis
    • Determination of bone viability: infarction or avascular necrosis
    • Evaluation of fractures difficult to assess on radiographs
    • Evaluation of bone pain in patients with normal or equivocal radiographs
    • Evaluation of the significance of an incidental skeletal finding on radiographs
    • Metastatic disease: 80% of patients with known neoplasms and significant bone pain have metastases documented by bone scan.

    Metastatic Disease

    • Single lesions are often secondary to benign disease, especially in ribs.
    • Multiple foci of increased activity in non-contiguous ribs suggest metastatic disease.
    • Lesions extending into posterior elements or involving vertebral pedicle are likely metastatic.
    • Regional distribution of lesions for common bone-seeking primary tumors: thorax and ribs (37%), spine (26%), pelvis (16%), limbs (15%), and skull (6%).
    • Follow-up bone scans to assess response in patients undergoing treatment for advanced breast and prostate cancer should be interpreted with caution.

    Superscan

    • Diffuse involvement of the skeleton by metastases can cause a superscan, characterized by decreased renal activity with diffusely increased activity throughout the axial skeleton.
    • A superscan can also be caused by metabolic conditions, such as primary or secondary hyperparathyroidism.
    • Increased activity primarily in the peripheral skeleton may be seen in hematologic disorders.

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    Description

    Explore the interpretation of fluorine-18 sodium fluoride positron emission tomography (PET) and PET/computed tomography (CT) scans in clinical scenarios. Understand how imaging findings can aid in the diagnosis and management of patients with metastatic disease.

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