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? |
