chapter Bone Density (Densitometry) RADIOPHARMACY INDICATIONS Radionuclide Localization Quality Control Adult Dose Range Method of Administration

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1 _CH04_redo.qxd 12/3/07 3:47 PM Page 17 chapter 4 Bone Density (Densitometry) RADIOPHARMACY Radionuclide Single radionuclide: 125 I t 1/2 : 60.1 days Energies: kev Type: EC, x, γ, accelerator or: 241 Am (americium) t 1/2 : years Energies: 60 kev Type: α, γ, spontaneous fission product. Dual radionuclide: 153 Gd (gadolinium) t 1/2 : days Energies: 44, 100 kev (γ); 35, 70 kev (x-ray) Type: x, γ, neutron irradiation of 152 Gd Radiopharmaceutical N/A Localization N/A Quality Control Image phantom every day of use. Adult Dose Range N/A Method of Administration Exposure to, not administration by injection. INDICATIONS Detection of osteoporosis. Monitoring and evaluation of treatment programs for osteoporosis (e.g., estrogen, progesterone, testosterone replacement, calcitonin therapy, exercise, or pharmacologic interventions with vitamins). Evaluation of osteopenia (diminished bone tissue). Evaluation of effect of menopause and premature spontaneous menopause on bone density (for hormone therapy management). Evaluation for premenopausal oophorectomy. Evaluation of effect of steroid therapy on bone density. 17

2 _CH04_redo.qxd 12/3/07 3:47 PM Page 18 NUCLEAR MEDICINE TECHNOLOGY: Procedures and Quick Reference Evaluation of effect of Cushing s syndrome on bone density (and other endocrinopathies, e.g., prolactinoma, hyperparathyroidism, hyperthyroidism, and male hypogonadism). Detection and evaluation of pathologic fractures. Evaluation of effect of chronic renal disease on bone density. Evaluation of effect of gastrointestinal syndromes on bone density. Evaluation of effect of postgastrectomy and other malabsorption diseases on bone density. Evaluation of effect of long-term immobilization on bone density. Evaluation of bone density due to abnormal results on related studies. CONTRAINDICATIONS Dense vertebrae from degenerative disease, fracture, injury, or metastatic cancer should be excluded as area of interest. Nuclear medicine scan within 7 days of bone density scan. PATIENT PREPARATION Identify the patient. Verify doctor s order. Explain the procedure. Remove metal objects from person and/or pockets. EQUIPMENT Camera Rectilinear-style scanner Bone densitometer single or dual energy x-ray absorptiometry Computer Set-up Factory settings Collimator Collimated x-ray pencil beam PROCEDURE (TIME: ~30 60 MINUTES) SPA (single photon absorptiometry) is suggested in pediatric through adolescent patients because long bones are most metabolically active. It is useful in determining bone development in many childhood and pediatric diseases. There is also SEXA (single energy x-ray absorptiometry), which is more expensive but does not require replacement of the gamma source. Position patient s region of interest (ROI) under the scanner. The denser the bone, the more absorption of photons. Image patient s nondominant arm unless there is a known fracture to that extremity. Because of the low energy of 125I, it is used mainly on wrist or distal forearm studies. (The junction of the middle and distal third of the radius is the preferred site.) Most scanners have preprogrammed scan lengths and processing. Compare results with database table for that patient (usually contained in a software processing program). DPA (dual photon absorptiometry of gamma rays, 20- to 40-minute scan) or DEXA (dual energy x-ray absorptiometry, 2- to 5-minute scan) for other patients emphasizes lumbar spine and proximal femur at the hip. Position patient supine on imaging table; elevate legs at knees to flatten pelvis and lumbar spine against scanning table. Obtain scan of L1 L5, rectilinear fashion, with dual energy photon beam beneath table. Gamma or x-rays pass through patient and are picked up by detector on C-arm above the table. 18

3 _CH04_redo.qxd 12/3/07 3:47 PM Page 19 Chapter 4 Bone Density (Densitometry) Obtain scan of proximal femur (hip area). Obtain scan of distal radius and/or wrist. Compare values to those of a database established for patient s characteristics (e.g., age, sex, race, and weight). NORMAL RESULTS Values obtained from scan or scans fall within normal limits listed in established database table. Results are compared with age-matched controls (Z score) or to a young normal population (T score) that represents the peak bone mass. This is expressed as percentages or standard deviations from the normal range. T score of greater (less negative) than 1.0 (<1 standard deviation below young normal controls) is normal. ABNORMAL RESULTS Values between 1.0 and 2.5 are evidence of osteopenia. Values of less (more negative) than 2.5 are osteoporosis. Values 10% lower than published mean for patient s age are considered mildly osteoporotic. Clinically significant osteopenia. Patients with vertebral values between 0.8 and 0.99 g/cm 2 have about a 20% predictability of spontaneous fracture. Patients with vertebral values between 0.62 and 0.8 g/cm 2 are more likely to have a spontaneous fracture. Patients with vertebral values < 0.62 g/cm 2 will be found to have already had at least one spontaneous fracture 100% of the time. ARTIFACTS Overlying metal objects will cause falsely elevated results. A dense vertebra from severe degenerative disease or fracture, injury, or metastatic cancer should not be used for analysis. Degenerative disease with severe facet sclerosis may result in artificially high values. A heavily calcified overlying aorta may result in artificially high values. Recent gastrointestinal barium studies may interfere because of attenuation of the photons by barium. For patients approaching 300 pounds, because of the weak strength of the photons, extra care may be needed to reduce soft-tissue attenuation. For patients over 300 pounds in weight, the average table weight limit, it may not be possible to do lower back/hip measurements. The alternative is to do distal forearm/wrist measurements. NOTE Usual analysis includes averaging anterior-posterior image values taken from the L2 L4 vertebrae. Studies include bone density (of trabecular and cortical bone), bone mineral content, percent fat, and lean body mass. The lifetime risk to women for hip fracture is 15%, compared with men, 5%. Vertebral fractures usually occur earlier and carry with them pain, decreased physical activity, and change in physical appearance, e.g., reduced height and dowager s hump or senile dorsal kyphosis. With the treatment available, the earlier the diagnosis of osteopenia or osteoporosis, the more likely the better outcome. SPA and SEXA work extremely well for pediatric patients in determining bone density and mineral content of the radius by comparing values with published normal tables. 19

4 _CH04_redo.qxd 12/3/07 3:47 PM Page 20 NUCLEAR MEDICINE TECHNOLOGY: Procedures and Quick Reference DEXA delivers improved precision (<1%) because of increased photon flux of x-rays (35 and 70 kev), greater stability, and constancy of the photon source and hence at present is considered the superior system for measuring bone density. Scan time is 4 minutes for lumbar spine with whole-body bone mineral content studies in minutes (multiple detectors). These systems can also perform ROI studies on any bone in the body, opening application possibilities to a wide variety of orthopedic and metabolic studies not easily accommodated by other modalities. DPA may soon surpass 1% precision as well because of refinements in equipment. Both deliver clinically useful data and both deliver low radiation exposure (1 2 mrem to the skin surface). If 153 Gd is used as the gamma source (44 and 100 kev), although the useful life might be up to 18 months, it is recommended that it be changed once a year. CT can also be used for single or dual photon technique. The scanner can be programmed or modified to accommodate either. The radiation exposure, however, is mrem per study. Some of the positions required are awkward to achieve. Drugs for osteoporosis: Estrogen therapy and Hormone therapy (e.g., Prempro ) Raloxifene (Evista ) Teriparatide (parathyroid hormone, Forteo ) Alendronate (Fosamax ) Risedronate (Actonel ) Calcitonin (Miacalcin, Calcimar, or Fortical ) Pamidronate (Aredia ) Ibandronate (Boniva ) Corticosteroids Etidronate (Didronel ) Sodium fluoride (Fluoritab, Karidium, Pharmaflur ) PATIENT HISTORY The patient should answer the following questions. Do you have a history or family history of cancer? Y N If so, what type and for how long? What is your age, height, and weight? Do you have a history of bone disease? Y N Is there a family history of osteoporosis or dowager s hump? Y N Do you have any breaks or fractures? Y N Have you had any recent surgery requiring metal or screws in back, Y N hip, legs, or arms? Have you had any recent trauma to arms, hips, or legs? Y N If so, where and when? Y N Are you on steroid therapy? Y N Are you taking calcium supplements? Y N (continued) 20

5 _CH04_redo.qxd 12/3/07 3:47 PM Page 21 Chapter 4 Bone Density (Densitometry) Are you taking Didronel or alendronic sodium (Fosamax ) or Y N any drug for osteoporosis? If so, for how long? Do you have any prostheses? Y N Have you had any recent barium studies? Y N Have you had any of the following diseases: rheumatoid arthritis, Y N lupus, hyperthyroidism, hypothyroidism, kidney disease, diabetes, Cushing s syndrome, Crohn s disease, colitis, gastrectomy? Are you physically inactive? Y N Have you had any recent related studies or scans? Y N Female patients: Are you pregnant or nursing? Y N When was your last menstrual cycle? Have you experienced a pregnancy? Y N Have you experienced menopause? Y N If so, at what age? Have you had your ovaries removed? Y N Have you had a hysterectomy? Y N Are you on any female hormone replacement therapy? Y N Other department-specific questions. Students Explain the relevancy of each of the above patient history questions to this particular scan. Can you think of others that would be helpful for the interpretation of this type of study? Suggested Readings Brener T, ed. Nursing 2007 Drug Handbook, 27th ed. Philadelphia: Lippincott Williams & Wilkins, Chohan N, ed. Nursing 99 Drug Handbook. Springhouse, PA: Springhouse, Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine, 2nd ed. St. Louis: Mosby, Mettler FA Jr, Guiberteau MJ. Essentials of Nuclear Medicine Imaging, 5th ed. Philadelphia: Saunders, Wilson MA. Textbook of Nuclear Medicine. Philadelphia: Lippincott-Raven,

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