Bone scan
Encyclopedia
A bone scan or bone scintigraphy is a nuclear scanning test to find certain abnormalities in bone which are triggering the bone's attempts to heal. It is primarily used to help diagnose a number of conditions relating to bones, including: cancer of the bone or cancers that have spread (metastasized) to the bone, locating some sources of bone inflammation (e.g. bone pain such as lower back pain due to a fracture), the diagnosis of fractures that may not be visible in traditional X-ray images, and the detection of damage to bones due to certain infections and other problems.
Nuclear medicine bone scans are one of a number of methods of bone imaging, all of which are used to visually detect bone
abnormalities. Such imaging studies include magnetic resonance imaging
(MRI), X-ray computed tomography
(CT) and in the case of 'bone scans' nuclear medicine
. However, a nuclear bone scan is a functional test, which means it measures an aspect of bone metabolism or Bone remodeling
, which most other imaging techniques cannot. The nuclear bone scan competes with the FDG-PET scan in seeing abnormal metabolism in bones, but it is considerably less expensive.
Nuclear bone scans are not to be confused with the completely different test often termed a "bone density scan," DEXA or DXA, which is a low exposure X-ray test measuring bone density to look for osteoporosis and other diseases where bones lose mass, without any bone re-building activity. The nuclear medicine scan technique is sensitive to areas of unusual bone re-building activity because the radiopharmaceutical is taken up by osteoblast
cells which build bone. The technique therefore is sensitive to fractures and bone reaction to infections and bone tumors, including tumor metastases to bones, because all these pathologies trigger bone osteoblast activity. The bone scan is not sensitive to osteoporosis
or multiple myeloma
in bones, and therefore other techniques must be used to assess bone abnormalities from these diseases.
such as 600 MBq
of technetium-99m-MDP and then scanned with a gamma camera
, a device sensitive to the radiation emitted by the injected material. Two-dimensional projections of scintigraphy
may be enough, but in order to view small lesions (less than 1 cm) especially in the spine, single photon emission computed tomography
(SPECT) imaging technique may be required. In the United States, most insurance companies require separate authorization for SPECT imaging.
About half of the radioactive material is localized by the bones. The more active the bone turnover, the more radioactive material will be seen. Some tumor
s, fractures
and infection
s show up as areas of increased uptake. Others can cause decreased uptake of radioactive material. Not all tumors are easily seen on the bone scan. Some lesions, especially lytic (destructive) ones, require positron emission tomography
(PET) for visualization.
About half of the radioactive material leaves the body through the kidney
s and bladder
in urine
. Anyone having a study should empty their bladder immediately before images are taken.
In evaluating for tumors, the patient is injected with the radioisotope and returns in 2-3 hours for imaging. Image acquisition takes from 30 to 70 minutes, depending if SPECT images are required. If the physician wants to evaluate for osteomyelitis
(bone infection) or fractures
, then a Three Phase Bone Scan is performed where 20-30 minutes of images (1st and 2nd Phases) are taken during the initial injection. The patient then returns in 2-3 hours for additional images (3rd Phase). Sometimes late images are taken at 24 hours after injection.
Pregnant
patients should consult with a physician
before consenting to radioactive injections.
Nuclear medicine bone scans are one of a number of methods of bone imaging, all of which are used to visually detect bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
abnormalities. Such imaging studies include magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI), X-ray computed tomography
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
(CT) and in the case of 'bone scans' nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
. However, a nuclear bone scan is a functional test, which means it measures an aspect of bone metabolism or Bone remodeling
Bone remodeling
Bone remodeling is a lifelong process where mature bone tissue is removed from the skeleton and new bone tissue is formed...
, which most other imaging techniques cannot. The nuclear bone scan competes with the FDG-PET scan in seeing abnormal metabolism in bones, but it is considerably less expensive.
Nuclear bone scans are not to be confused with the completely different test often termed a "bone density scan," DEXA or DXA, which is a low exposure X-ray test measuring bone density to look for osteoporosis and other diseases where bones lose mass, without any bone re-building activity. The nuclear medicine scan technique is sensitive to areas of unusual bone re-building activity because the radiopharmaceutical is taken up by osteoblast
Osteoblast
Osteoblasts are mononucleate cells that are responsible for bone formation; in essence, osteoblasts are specialized fibroblasts that in addition to fibroblastic products, express bone sialoprotein and osteocalcin.Osteoblasts produce a matrix of osteoid, which is composed mainly of Type I collagen...
cells which build bone. The technique therefore is sensitive to fractures and bone reaction to infections and bone tumors, including tumor metastases to bones, because all these pathologies trigger bone osteoblast activity. The bone scan is not sensitive to osteoporosis
Osteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...
or multiple myeloma
Multiple myeloma
Multiple myeloma , also known as plasma cell myeloma or Kahler's disease , is a cancer of plasma cells, a type of white blood cell normally responsible for the production of antibodies...
in bones, and therefore other techniques must be used to assess bone abnormalities from these diseases.
Technique
In the nuclear medicine technique, the patient is injected (usually into a vein in the arm or hand, occasionally the foot) with a small amount of radioactive materialTechnetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
such as 600 MBq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
of technetium-99m-MDP and then scanned with a gamma camera
Gamma camera
A gamma camera, also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy...
, a device sensitive to the radiation emitted by the injected material. Two-dimensional projections of scintigraphy
Scintigraphy
Scintigraphy is a form of diagnostic test used in nuclear medicine, wherein radioisotopes are taken internally, and the emitted radiation is captured by external detectors to form two-dimensional images...
may be enough, but in order to view small lesions (less than 1 cm) especially in the spine, single photon emission computed tomography
Single photon emission computed tomography
Single-photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera. However, it is able to provide true 3D information...
(SPECT) imaging technique may be required. In the United States, most insurance companies require separate authorization for SPECT imaging.
About half of the radioactive material is localized by the bones. The more active the bone turnover, the more radioactive material will be seen. Some tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
s, fractures
Bone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
and infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s show up as areas of increased uptake. Others can cause decreased uptake of radioactive material. Not all tumors are easily seen on the bone scan. Some lesions, especially lytic (destructive) ones, require positron emission tomography
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
(PET) for visualization.
About half of the radioactive material leaves the body through the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s and bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
in urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
. Anyone having a study should empty their bladder immediately before images are taken.
In evaluating for tumors, the patient is injected with the radioisotope and returns in 2-3 hours for imaging. Image acquisition takes from 30 to 70 minutes, depending if SPECT images are required. If the physician wants to evaluate for osteomyelitis
Osteomyelitis
Osteomyelitis simply means an infection of the bone or bone marrow...
(bone infection) or fractures
Bone fracture
A bone fracture is a medical condition in which there is a break in the continuity of the bone...
, then a Three Phase Bone Scan is performed where 20-30 minutes of images (1st and 2nd Phases) are taken during the initial injection. The patient then returns in 2-3 hours for additional images (3rd Phase). Sometimes late images are taken at 24 hours after injection.
Pregnant
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
patients should consult with a physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
before consenting to radioactive injections.