Musculoskeletal

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Jan 24, 2016 | Posted by in NUCLEAR MEDICINE | Comments Off on Musculoskeletal
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Questions


Answers


1. What are the two main advantages of bone scintigraphy?


1. high sensitivity for cortical lesions, and ease of surveying the entire skeleton


2. What is the main disadvantage of bone scintigraphy?


2. The findings are often nonspecific.


3. Which two factors give skeletal scintigraphy its specificity?


3. the clinical context and the total body pattern


4. What class of radiopharmaceutical compound is most commonly used for skeletal scintigraphy?


4. 99mTc-diphosphonates


5. Why are 99mTc-diphosphonates superior to 99mTc-pyrophosphates for skeletal scintigraphy?


5. 99mTc-diphosphonates have faster clearance.


6. How are 99mTc-diphosphonates prepared?


6. Sodium pertechnetate (NaTcO4) from a 99Mo-generator is added to a vial with diphosphonate and stan-nous ion, Sn (II). The stannous ion reduces Tc, and the reduced Tc chelates to diphosphonate.


7. How does the introduction of oxygen into a vial of 99mTc-diphospho-nate affect the bone scan image?


7. The formation of colloidal Tc causes liver and spleen uptake; the formation of free Tc causes stomach and thyroid uptake.


8. What percentage of a 99mTc-diphosphonate dose localizes in bone?


8. 50%


9. How is 99mTc-diphosphonate that does not localize in bone cleared from the body?


9. glomerular filtration


10. What percentage of the dose is in the blood at two to three hours after injection?


10. 3% to 5%


11. Why does 99mTc-diphosphonate have an affinity for newly formed bone?


11. It has higher absorption to amorphous CaPO4 than to mature hydroxyapatite.


12. What two factors affect the degree of 99mTc-diphosphonate in bone?


12. bone formation and blood flow


13. What is the body’s critical organ for radiation dose in skeletal scintigraphy?


13. the bladder


14. How can a patient decrease the radiation dose from a bone scan?


14. The patient should void frequently.


15. How should a patient be prepared for a bone scan?


15. The patient should be well hydrated, should remove all metal objects (jewelry, coins, keys, etc.) before imaging, and should void immediately before the study and frequently after the procedure.


16. What is the usual adult dosage and route of administration of 99mTcdiphosphonates?


16. 20 mCi (740 MBq) intravenously


17. What special type of imaging should be performed with a bone scan for distinguishing suspected osteomyelitis from cellulitis?


17. dynamic blood flow and immediate images


18. When is delayed imaging performed for bone scanning?


18. at two to four hours after tracer injection


19. How many counts are typically obtained for spot bone scan images?


19. 600,000 counts of anterior chest for spot views and all other views for the same time


20. What types of collimators are used for bone scanning?


20. An all-purpose collimator is used for routine imaging; high-resolution, pinhole, or converging collimators are used for more detail.


21. How do bone scans of children and adolescents differ from bone scans of adults?


21. Epiphyseal uptake is present in bone scans of children and adolescents


22. How do neonatal bone scans differ from bone scans of children and adolescents?


22. There is diffusely decreased uptake in neonatal bone scans.


23. How can one tell if the kidneys have increased uptake on a bone scan?


23. The uptake will be more than the lumbar spine uptake.


24. What are four normal variants seen in the skull?


24. uneven or variable, hyperostosis frontalis interna, sphenoid uptake, and uptake between orbits


25. Why can joints show mild diffuse asymmetry?


25. because of handedness (right or left)


26. Which joints can normally show increased uptake?


26. sternomanubrial joint, sternal ossification centers, sacroiliac joints


27. What is the mechanism of increased bone scan uptake by a bone metastasis?


27. The growth of the tumor causes surrounding bony remodeling.


28. How much change in bone density is required to see a skeletal metastasis on plain radiography?


28. 30% to 50%


29. When can metastatic disease not cause the bone scan to be abnormal?


29. marrow-based lesion


30. Which imaging tests would be useful for marrow-based or lytic lesions?


30. MRI, 18F-FDG


31. What is the typical scintigraphic pattern of metastatic disease?


31. multiple focal lesions distributed randomly in the axial skeleton


32. Why can metastatic disease show a ring lesion on skeletal scintigraphy?


32. Uptake is in the reactive bone surrounding a large tumor; the tumor itself does not take up tracer.


33. How can the bone scan findings of osteomalacia and Cushing syndrome be distinguished from metastatic disease?


33. There is a predominance of rib lesions in osteomalacia and Cushing syndrome.


34. How can osteoarthritis be distinguished from skeletal metastases on a bone scan?


34. Osteoarthritis causes uptake that is limited to joints, commonly involving both sides of a joint.


35. How can trauma to the ribs be distinguished from skeletal metastases on a bone scan?


35. The lesions are aligned.


36. How can Paget disease be distinguished from skeletal metastases on a bone scan?


36. In Paget disease, uptake is characteristically intense and expansile, and it tracks along the length of a bone or hemipelvis.


37. What are four clues to the diagnosis of a superscan?


37. good bone-to-soft-tissue uptake, absent or faint kidney uptake, increased axial-to-appendicular uptake ratio, and findings on plain radiographs


38. What is a “flare phenomenon”?


38. increased uptake following chemo-therapy due to healing of bone after regression of metastases


39. How long does it usually take for flare phenomena to normalize?


39. six months


40. Which five tumors commonly metastasize to bone?


40. tumors of the prostate, breast, lung, kidney, and thyroid


41. What is the mechanism of cold lesions on a bone scan?


41. loss of blood flow or complete destruction of bone


42. What tumors tend to cause no bone reaction on a bone scan?


42. multiple myeloma


43. What is the usual cause of positive lesions on a bone scan in a patient with multiple myeloma?


43. pathologic fractures


44. What is the sensitivity of an increased alkaline phosphatase scan for skeletal metastases from prostate cancer?


44. 50%


45. What is the sensitivity of plain radiographs for skeletal metastases from prostate cancer?


45. 70%


46. What percentage of stage I prostate cancer patients have skeletal metastases on a bone scan?


46. 5%


47. What percentage of stage I breast cancer patients have skeletal metastases on a bone scan?


47. 3% to 5%


48. How does mastectomy affect the bone scan?


48. asymmetry of rib uptake


49. What is the significance of sternal bone scan uptake ipsilateral to a primary breast cancer?


49. It indicates local invasion from metastases to inframammary nodes.


50. How does the typical distribution of metastatic disease from lung cancer differ from metastatic disease from breast or prostate cancer?


50. Appendicular involvement is more common.


51. What nonmetastatic finding is commonly seen on the bone scans of patients with lung cancer?


51. hypertrophic pulmonary osteoarthropathy


52. What is the typical location of skeletal metastases of neuroblastomas?


52. metaphysis adjacent to the epiphy-seal growth plate


53. What percentage of primary neuroblastomas take up the tracer on bone scanning?


53. 30% to 50%


54. What are the usual age groups affected by osteoid osteoma?


54. adolescents and young adults


55. What is the typical uptake of most benign tumors of bone?


55. mildly increased uptake


56. What types of benign bone tumors can have increased uptake?


56. osteoblastomas and osteoid osteomas


57. When do enchondromas have markedly increased uptake?


57. when they are complicated by fracture


58. What percentage of fractures are visualized on a bone scan by 24 hours?


58. 80%


59. What percentage of fractures in patients under age 65 are visualized on a bone scan by 72 hours?


59. 95%


60. When is fracture sensitivity maximal on bone scans in patients over age 65?


60. at more than seven days


61. What percentage of nondisplaced uncomplicated fractures is normal at one year?


61. 60% to 80%


62. What percentage of nondisplaced uncomplicated fractures is normal at three years?


62. 95%


63. How long does it take for complicated or displaced fractures to return to normal on a bone scan?


63. They are positive indefinitely.


64. How does a craniotomy site present on a bone scan?


64. ring pattern that persists for months


65. How does rib resection during a thoracotomy affect a bone scan?


65. It causes rib uptake from periosteal reaction.


66. What do intercalary bone grafts look like on a bone scan?


66. uptake at bone ends that gradually fill in as the graft revitalizes


67. What do pedicle bone grafts look like on a bone scan?


67. diffuse immediate uptake


68. How does radiotherapy affect bone scan uptake at the site of radiation?


68. It initially causes mildly increased uptake, with persistently decreased uptake within 6 to 12 months in the geometric pattern of a radiation port.


69. What is the typical appearance of stress fractures?


69. oval or fusiform uptake that is parallel to the long axis of the bone


70. What is the typical appearance of shin splints?


70. diffuse uptake along greater than one-third of the bone length of the mid- to distal tibia without focal uptake


71. What is the prognostic difference between stress fractures and shin splints?


71. Stress fractures are predictive of further injury without relief of stress, while shin splints are not predictive of further injury.


72. What is the appearance of rhabdomyolysis on a bone scan?


72. localization of tracer in damaged skeletal muscle corresponding to the muscle group that was overexercised


73. When is the maximum bone scan uptake with rhabdomyolysis?


73. one week


74. What is the appearance of newly infarcted bone on a bone scan?


74. a cold lesion


75. What imaging technique should be used to detect the osteonecrosis of Legg-Calvé-Perthes disease on a bone scan?


75. pinhole collimation


76. What is the typical finding of LeggCalvé-Perthes disease on a bone scan done early in the course of the disease?


76. a lentiform photon-deficient area in the upper outer femoral head


77. What is the typical finding of LeggCalvé-Perthes disease on a bone scan done in the middle of the course of the disease?


77. uptake at the margin of a photon-deficient area in the upper outer femoral head


78. What is the typical finding of LeggCalvé-Perthes disease on a bone scan done late in the course of the disease?


78. increased uptake in the femoral head


79. What is the typical finding of steroid-induced osteonecrosis on a bone scan?