chapter4

17

Bone Density(Densitometry)

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.

Radionuclide• Single radionuclide: 125I t1/2: 60.1 days

Energies: 23–31 keVType: EC, x, γ, accelerator

• or: 241Am (americium) t1/2: 432.7 yearsEnergies: 60 keVType: α, γ, spontaneous fission product.

• Dual radionuclide: 153Gd (gadolinium) t1/2:241.6 daysEnergies: 44, 100 keV (γ); 35, 70 keV (x-ray)Type: x, γ, neutron irradiation of 152Gd

Radiopharmaceutical• N/A

RADIOPHARMACY

INDICATIONS

• Detection of osteoporosis.• Monitoring and evaluation of treatment programs for osteoporosis (e.g., estrogen, progesterone, testos-

terone 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.

10766-04_CH04_redo.qxd 12/3/07 3:47 PM Page 17

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 beexcluded 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

PROCEDURE (TIME: ~30–60 MINUTES)

• SPA (single photon absorptiometry) is suggested in pediatric through adolescent patients becauselong bones are most metabolically active. It is useful in determining bone development in manychildhood and pediatric diseases. There is also SEXA (single energy x-ray absorptiometry), which ismore 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 junc-

tion of the middle and distal third of the radius is the preferred site.) Most scanners have pre-programmed scan lengths and processing.

• Compare results with database table for that patient (usually contained in a software processingprogram).

• 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 prox-imal 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.

Computer Set-up• Factory settings

Camera• Rectilinear-style scanner• Bone densitometer—single or dual energy

x-ray absorptiometry

Collimator• Collimated x-ray pencil beam

10766-04_CH04_redo.qxd 12/3/07 3:47 PM Page 18

• 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 deviationsfrom 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/cm2 have about a 20% predictability of

spontaneous fracture.• Patients with vertebral values between 0.62 and 0.8 g/cm2 are more likely to have a spontaneous

fracture.• Patients with vertebral values < 0.62 g/cm2 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, andchange in physical appearance, e.g., reduced height and “dowager’s hump” or senile dorsalkyphosis. 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 mineralcontent of the radius by comparing values with published normal tables.

19

Chapter 4 — Bone Density (Densitometry)

10766-04_CH04_redo.qxd 12/3/07 3:47 PM Page 19

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 supe-rior system for measuring bone density. Scan time is ∼4 minutes for lumbar spine with whole-bodybone mineral content studies in 10–20 minutes (multiple detectors). These systems can also performROI studies on any bone in the body, opening application possibilities to a wide variety oforthopedic and metabolic studies not easily accommodated by other modalities.

• DPA may soon surpass 1% precision as well because of refinements in equipment. Both deliver clin-ically useful data and both deliver low radiation exposure (1–2 mrem to the skin surface). If 153Gd isused as the gamma source (44 and 100 keV), although the useful life might be up to 18 months, itis recommended that it be changed once a year.

• CT can also be used for single or dual photon technique. The scanner can be programmed ormodified to accommodate either. The radiation exposure, however, is 250–1000 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 Nhip, 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)

10766-04_CH04_redo.qxd 12/3/07 3:47 PM Page 20

21

Chapter 4 — Bone Density (Densitometry)

Are you taking Didronel or alendronic sodium (Fosamax®) or Y Nany 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 Nlupus, 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.

StudentsExplain 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, 2006.Chohan N, ed. Nursing 99 Drug Handbook. Springhouse, PA: Springhouse, 1999.Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine, 2nd ed. St. Louis: Mosby, 1995.Mettler FA Jr, Guiberteau MJ. Essentials of Nuclear Medicine Imaging, 5th ed. Philadelphia: Saunders,

2006.Wilson MA. Textbook of Nuclear Medicine. Philadelphia: Lippincott-Raven, 1998.

10766-04_CH04_redo.qxd 12/3/07 3:47 PM Page 21

Notes

NUCLEAR MEDICINE TECHNOLOGY: Procedures and Quick Reference

22

10766-04_CH04_redo.qxd 12/3/07 3:47 PM Page 22