THE SKELETAL SYSTEM

Question 1

What are the primary components of the bone matrix?

Answer 1

1. Inorganic calcium hydroxyapatite (Ca10[PO4]6[OH]2) crystals
2. Organic matrix of collagen
3. Blood vessels

This physiological activity can be imaged with radioactive analogs of calcium, phosphate, or hydroxyl ions (OH–) that can localize to the bone, with areas of growth or repair resulting in increased turnover.

Question 2

How does nuclear medicine differ from conventional imaging methods like radiographs and CT?

Answer 2

Nuclear medicine techniques evaluate function in an organ or system, while conventional methods like radiographs and CT examine anatomical features.

Question 3

What is a bone scan and what radiopharmaceutical is commonly used in this procedure?

Answer 3

A bone scan is a nuclear medicine imaging technique that uses the radiopharmaceutical technetium-99m (Tc-99m) combined with a localizing carrier molecule like methylene diphosphonate (MDP).

Question 4

Why has the bone scan remained widely used despite advances in CT and MR imaging?

Answer 4

due to its high sensitivity for detecting disease, ability to image the entire skeleton, and reasonable cost.

Question 5

What advancements have improved the quality of scintigraphic images?

Answer 5

Advancements in camera detector technology, processing software, and the use of three-dimensional (3-D) single-photon emission computed tomography (SPECT) have improved scintigraphic image quality.

Question 6

How does CT correlation enhance the accuracy of a bone scan?

Answer 6

CT correlation helps explain the etiology of nonspecific abnormal activity seen in a bone scan by providing anatomical context, especially when fused with SPECT.

Question 7

What are the advantages of fluorine-18 fluorodeoxyglucose (F-18 FDG) PET/CT compared to traditional bone scans?

Answer 7

F-18 FDG PET/CT is superior in assessing many diseases, particularly cancer, and often complements the bone scan by providing additional functional and metabolic information.

Question 8

What is the role of fluorine-18 sodium fluoride (F-18 NaF) in bone imaging?

Answer 8

F-18 NaF is a highly sensitive bone-imaging radiopharmaceutical that provides faster imaging compared to Tc-99m MDP, though its uptake is not specific to benign or malignant processes.

Question 9

What are some examples of targeted radionuclide therapy for metastatic disease?

Answer 9

Bone-localizing beta-emitters:
* strontium-89 (Sr-89)
* samarium-153 (Sm-153)
* rhenium-186 (Rh-186)
* phosphorus-32 (P-32)

**Alpha-emitter: **
* radium-223 (Ra-223)

Question 10

What is dual-energy x-ray absorptiometry (DEXA) used for in bone imaging?

Answer 10

DEXA is used to measure bone density and assess osteoporosis.