Nuclear scintigraphy
- Aka a gamma scan or bone scan,
- It involves the use of radioisotopes attached to drugs that travel to a specific organ or tissue.
- The emitted gamma radiation is captured by gamma cameras, forming two-dimensional image
- Nuclear scintigraphy (bone scan) is a sensitive method for identifying areas of increased metabolic activity throughout the skeletal system. They are not specific for metastatic lesions, because this activity may be related to inflammation or infection.
Gallium-67 scintigraphy
- A photon-emitting radiotracer used for scintigraphy which is used in the form of various salts like citrate and nitrate
- Once administered, imaging may consist of planar (2 dimensional) , SPECT, and SPECT-CT acquisitions.
- Mechanism of action
- Once injected it binds to plasma proteins (especially transferrin and lactoferrin), and has a predilection to sites of inflammation. It binds to inflammatory proteins and thus it pools up at the sites of various inflammatory and granulomatous reactions.
- Radionuclide profile
- Emits a spectrum of gamma rays (93, 185, 288, 394 KeV energy)
- Half life is about 78 hours
- Critical organ: bone surfaces (ICRP 128)
- Normal distribution is seen in the liver, bone marrow and spleen
- Technique
- Given in IV form, dose is about 111-222 MBq (3-6 mCi)
- Imaging can be done at 24, 48, and 72 hours.
- Study may include planar, SPECT and SPECT-CT imaging
- Has largely been replaced by 18-F FDG PET-CT imaging which has the advantage of earlier scan, better image quality, and SUV quantification
- Advantages
- Better in evaluation of spinal infection than other tagged WBC radiotracers
- Gallium citrate usually shows a negative scan earlier than other radionuclide like technetium used in bone scanning
- Disadvantages
- Higher radiation dose than other WBC radiotracers
- Poor image quality
- Cannot differentiate between osteomyelitis and cellulitis
- Findings include increased uptake in the 2 adjacent VBs with loss of intervening disc.
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