Bone scintigraphy

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Not to be confused with Dual-energy X-ray absorptiometry. Bone scintigraphy_sentence_0

Bone scintigraphy_table_infobox_0

Bone scintigraphyBone scintigraphy_header_cell_0_0_0
ICD-9-CMBone scintigraphy_header_cell_0_1_0 Bone scintigraphy_cell_0_1_1
OPS-301 codeBone scintigraphy_header_cell_0_2_0 Bone scintigraphy_cell_0_2_1
MedlinePlusBone scintigraphy_header_cell_0_3_0 Bone scintigraphy_cell_0_3_1

A bone scan or bone scintigraphy /sɪnˈtɪɡrəfi/ is a nuclear medicine imaging technique of the bone. Bone scintigraphy_sentence_1

It can help diagnose a number of bone conditions, including cancer of the bone or metastasis, location of bone inflammation and fractures (that may not be visible in traditional X-ray images), and bone infection (osteomyelitis). Bone scintigraphy_sentence_2

Nuclear medicine provides functional imaging and allows visualisation of bone metabolism or bone remodeling, which most other imaging techniques (such as X-ray computed tomography, CT) cannot. Bone scintigraphy_sentence_3

Bone scintigraphy competes with positron emission tomography (PET) for imaging of abnormal metabolism in bones, but is considerably less expensive. Bone scintigraphy_sentence_4

Bone scintigraphy has higher sensitivity but lower specificity than CT or MRI for diagnosis of scaphoid fractures following negative plain radiography. Bone scintigraphy_sentence_5

History Bone scintigraphy_section_0

Some of the earliest investigations into skeletal metabolism were carried out by George de Hevesy in the 1930s, using phosphorus-32 and by Charles Pecher in the 1940s. Bone scintigraphy_sentence_6

In the 1950s and 1960s calcium-45 was investigated, but as a beta emitter proved difficult to image. Bone scintigraphy_sentence_7

Imaging of positron and gamma emitters such as fluorine-18 and isotopes of strontium with rectilinear scanners was more useful. Bone scintigraphy_sentence_8

Use of technetium-99m (Tc) labelled phosphates, diphosphonates or similar agents, as in the modern technique, was first proposed in 1971. Bone scintigraphy_sentence_9

Principle Bone scintigraphy_section_1

The most common radiopharmaceutical for bone scintigraphy is Tc with methylene diphosphonate (MDP). Bone scintigraphy_sentence_10

Other bone radiopharmaceuticals include Tc with HDP, HMDP and DPD. Bone scintigraphy_sentence_11

MDP adsorbs onto the crystalline hydroxyapatite mineral of bone. Bone scintigraphy_sentence_12

Mineralisation occurs at osteoblasts, representing sites of bone growth, where MDP (and other diphosphates) "bind to the hydroxyapatite crystals in proportion to local blood flow and osteoblastic activity and are therefore markers of bone turnover and bone perfusion". Bone scintigraphy_sentence_13

The more active the bone turnover, the more radioactive material will be seen. Bone scintigraphy_sentence_14

Some tumors, fractures and infections show up as areas of increased uptake. Bone scintigraphy_sentence_15

Technique Bone scintigraphy_section_2

In a typical bone scan technique, the patient is injected (usually into a vein in the arm or hand, occasionally the foot) with up to 740 MBq of technetium-99m-MDP and then scanned with a gamma camera, which captures planar anterior and posterior or single photon emission computed tomography (SPECT) images. Bone scintigraphy_sentence_16

In order to view small lesions SPECT imaging technique may be preferred over planar scintigraphy. Bone scintigraphy_sentence_17

In a single phase protocol (skeletal imaging alone), which will primarily highlight osteoblasts, images are usually acquired 2–5 hours after the injection (after four hours 50–60% of the activity will be fixed to bones). Bone scintigraphy_sentence_18

A two or three phase protocol utilises additional scans at different points after the injection to obtain additional diagnostic information. Bone scintigraphy_sentence_19

A dynamic (i.e. multiple acquired frames) study immediately after the injection captures perfusion information. Bone scintigraphy_sentence_20

A second phase "blood pool" image following the perfusion (if carried out in a three phase technique) can help to diagnose inflammatory conditions or problems of blood supply. Bone scintigraphy_sentence_21

A typical effective dose obtained during a bone scan is 6.3 millisieverts (mSv). Bone scintigraphy_sentence_22

Bone scintigraphy_unordered_list_0

  • Bone scintigraphy_item_0_0
  • Bone scintigraphy_item_0_1

PET bone imaging Bone scintigraphy_section_3

Main article: PET for bone imaging Bone scintigraphy_sentence_23

Although bone scintigraphy generally refers to gamma camera imaging of Tc radiopharmaceuticals, imaging with positron emission tomography (PET) scanners is also possible, using fluorine-18 sodium fluoride ([F]NaF). Bone scintigraphy_sentence_24

For quantitative measurements, Tc-MDP has some advantages over [F]NaF. Bone scintigraphy_sentence_25

MDP renal clearance is not affected by urine flow rate and simplified data analysis can be employed which assumes steady state conditions. Bone scintigraphy_sentence_26

It has negligible tracer uptake in red blood cells, therefore correction for plasma to whole blood ratios is not required unlike [F]NaF. Bone scintigraphy_sentence_27

However, disadvantages include higher rates of protein binding (from 25% immediately after injection to 70% after 12 hours leading to the measurement of freely available MDP over time), and less diffusibility due to higher molecular weight than [F]NaF, leading to lower capillary permeability. Bone scintigraphy_sentence_28

There are several advantages of the PET technique, which are common to PET imaging in general, including improved spatial resolution and more developed attenuation correction techniques. Bone scintigraphy_sentence_29

Patient experience is improved as imaging can be started much more quickly following radiopharmaceutical injection (30-45 minutes, compared to 2-3 hours for MDP/HDP). Bone scintigraphy_sentence_30

[F]NaF PET is hampered by high demand for scanners, and limited tracer availability. Bone scintigraphy_sentence_31

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: scintigraphy.