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Editor's Notes

• #5: The skeleton is an active, constantly changing organ. Bone responds to injury and disease with increased turnover and attempts at self-repair. This physiological process can be imaged with a variety of radiotracers that localize to areas of bone formation.
• #6: Any nuclide with an atomic number greater than 83 is radioactive.
• #7: Matter is anything that has mass and occupies space. Matter is made from elements. Elements are made up of atoms. Atoms consists of sub-atomic particles: Proton and Neutron in Nucleus and electron outside the nucleus.
• #9: THE NEUTRON-TO-PROTON RATIO IN THE NUCLEUS DETERMINS THE STABILITY OF THE ATOM. At certain ratios, atoms may be unstable, a process known as spontaneous decay can occur as the atom attempts to regain stability.
• #10: Radiopharmaceuticals aka radioactive substance aka radiotracers.
• #11: The radionuclide should be carrier-free—that is, it is not contaminated by either stable radionuclides or other radionuclides of the same element. Carrier material can negatively influence bio-distribution and labeling efficiency. It should have high specific activity—that is, radioactivity per unit weigh (mCi/mg); milli curie per milligram
• #12: Maximum bone accumulation is reached 1 h after injection and the level remains practically constant up to 72 h. The blood clearance of these radiopharmaceuticals is high. Three hours after injection only 3% of the administered activity remains in the bloodstream. The peak of activity through the kidneys is reached after approximately 20 min. Within 1 h, with normal renal function, more than 30% of the unbound complex has undergone glomerular filtration.
• #13: Tc99m can be labelled with a variety of compounds called chelators, which stabilise the nuclide and direct it to the part of the body that needs to be imaged. For example, methyl diphosphonate (MDP) is taken up by osteoblasts and therefore Tc99m-MDP is used for bone scintigraphy.
• #20: The principal use of bone scintigraphy is in searching for metastatic disease as it has a high sensitivity for this purpose. Bone scintigraphy typically will demonstrate metastases weeks or months before plain rad Approximately 80% of patients with known malignancy and bone pain will have metastases documented by bone scintigraphy.
• #21: In the case of a diagnostic procedure in a patient who is known or suspected to be pregnant, a clinical decision is necessary to weigh the benefits against the possible harm of carrying out any procedure.
• #24: When evaluating bone scan images, the following points should be taken into consideration: – The bone scan is very sensitive for localisation of skeletal metastases or tumours, but the specificity is low. It must be interpreted in the light of all available information, especially patient history, physical examination, other test results and previous studies. – Symmetry in the representation of right and left sides of the skeleton and homogeneity of tracer uptake within bone structures are important normal features. Particular attention should be paid to left–right asymmetries
• #25: background activity of soft tissue
• #26: In children the bone scan is characterized by areas of uptake due to active growth in the epiphyseal regions. After fusion of the epiphyses these areas are no longer visible. Most intense: distal femur - proximal tibia - proximal humerus Also the order of relative occurence of osteosarcoma in children.
• #27: Though encountered in other pathologic conditions, it is often possible to distinguish metastatic disease from other entities by analyzing the pattern of distribution of the abnormalities. Metastatic disease occasionally manifests as a solitary abnormality, usually in the spine like in degenerative d/s. SPECT is used to differentiate.
• #34: Nuclear medicine studies will only be reliable a few days after the injury as the bone needs time to react to the insult to change in its vascular supply and to alter the metabolic turn over.
• #35: • occurs in normal bone that undergoes abnormal stress (insufficiency fractures occur with normal stress in bones that are weakened) • most common sites are the femoral neck and tibia. • typical pattern is oval area of increased uptake with long axis parallel to axis of bone
• #36: Acute phase of vascular compromise: no radiotracer is delivered to the bone tissue. At scintigraphy, the affected part of the bone appears as a photopenic defect. After revascularization: exuberant osteoblastic repair manifests as intense radiotracer uptake. Subsequently, when repair is complete, radiotracer uptake may return to baseline levels
• #38: A combination of focal hyperperfusion, focal hyperemia, and focally increased bone uptake is virtually diagnostic for osteomyelitis.
• #41: 99mTc-sulphur colloid is used, which localizes to marrow since it is phagocytosed by the native reticuloendothelial cells.
• #50: For hemophiliac patients, the cost associated with surgical synovectomy for prophylactic clotting factor replacement to prevent hemarthrosis perioperatively decreases the cost effectiveness of this approach. Radiosynovectomy for chronic synovitis and hemarthrosis: a noninvasive outpatient procedure requiring no posttreatment physical therapy and having limited side effects, a high success rate, and low cost.
• #55: Nonsteroidal anti-inflammatory drugs generally provide relief of mild to moderate bone pain initially, but their efficacy is limited by ceiling effects. Opioid analgesics also may provide adequate relief initially, but they are frequently associated with adverse effects that limit their utility. Patients develop tolerance and require dose escalation. Although chemotherapy or hormonal therapy may relieve pain, ultimately patients become refractory to these treatments.
• #56: chemotherapy, by contrast, the drug molecule must be taken up by the cell to be lethal. External beams irradiate all the tissues in their path, and chemotherapy targets all fast-growing cell populations.
• #57: Bone-marrow stem cells are very radiosensitive, and because of their close proximity to red marrow and the beta-emitting radioisotope localized to bone surface, suppression may occur.
• #59: In patients who have received or will receive another phosphonate-based therapy within 2 or 3 days of the radioisotope therapy, radiopharmaceutical use should be avoided because many phosphate-based therapies (such as pamidronate, a bisphosphonate) compete for the same binding sites in bone as do the radioisotopes, and this possibly may reduce the efficacy of both agents.