Gallium-67 scintigraphy

Gallium-67 is 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. 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: colon
• normal distribution is seen in the liver, bone marrow and spleen

Uses

• localization of source of fever in cases of fever of unknown origin (FUO)
• sarcoidosis
• tuberculosis
• retroperitoneal fibrosis
• bleomycin and amiodarone induced pulmonary toxicity
• spinal osteomyelitis
• bronchogenic carcinoma
• ulcerative colitis
• non-specific tumor imaging agent (used in lymphomas in the past, before advent of F-18 FDG PET-CT) 
• deep vein thrombosis
• interstitial nephritis
• pneumoconioses

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• has largely been replaced by 18-F FDG PET-CT imaging which has the advantage of earlier scan, better image quality, and SUV quantification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/disadvantages

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