Gallium scan

From Wikipedia, the free encyclopedia
  (Redirected from Gallium 67 scan)
Jump to: navigation, search
Gallium 67 scan
Medical diagnostics
ICD-10-PCS

C?1?LZZ (planar)

C?2?LZZ (tomographic)
ICD-9-CM 92.18
OPS-301 code 3-70c
MedlinePlus 003450

A gallium scan (also called "gallium imaging") is a type of nuclear medicine test that uses either a gallium-67 (67Ga) or gallium-68 (68Ga) radiopharmaceutical to obtain images of a specific type of tissue, or disease state of tissue. Gallium salts like gallium citrate and gallium nitrate are used. The form of salt is not important, since it is the freely dissolved gallium ion Ga3+ which is active.[1] Both 67Ga and 68Ga have similar uptake mechanisms.[2] The gamma emission of gallium 67 is imaged by a gamma camera, while the positron emission of gallium 68 scan is imaged by positron emission tomography (PET).

Gallium is taken up by tumors, inflammation, and both acute and chronic infection,[3][4] allowing these pathological processes to be imaged. Gallium is particularly useful in imaging osteomyelitis that involves the spine, and in imaging older and chronic infections that may be the cause of a fever of unknown origin.[5][6]

Mechanism[edit]

The body generally handles Ga3+ as though it were ferric iron (Fe-III), and thus the free isotope ion is bound (and concentrates) in areas of inflammation, such as an infection site, and also areas of rapid cell division.[7] Gallium (III) (Ga3+) binds to transferrin, leukocyte lactoferrin, bacterial siderophores, inflammatory proteins, and cell-membranes in neutrophils, both living and dead.[8]

Lactoferrin is contained within leukocytes. Gallium may bind to lactoferrin and be transported to sites of inflammation, or binds to lactoferrin released during bacterial phagocytosis at infection sites (and remains due to binding with macrophage receptors).[9] Ga-67 also attaches to the siderophore molecules of bacteria themselves, and for this reason can be used in leukopenic patients with bacterial infection (here it attaches directly to bacterial proteins, and leukocytes are not needed).[10] Uptake is thought to be associated with a range of tumour properties including transferring receptors, anaerobic tumor metabolism and tumor perfusion and vascular permeability.[11][12]

Medical uses[edit]

Gallium scan showing panda (A) and lambda (B) patterns, considered specific for sarcoidosis in the absence of histological confirmation.

In the past, the gallium scan was the gold standard for lymphoma staging, until it was replaced by positron emission tomography using fludeoxyglucose (FDG).[13][14] Gallium imaging is still used to image inflammation and chronic infections, and it still sometimes locates unsuspected tumors as it is taken up by many kinds of cancer cells in amounts that exceed those of normal tissues. Thus, an increased uptake of gallium-67 may indicate a new or old infection, an inflammatory focus from any cause, or a cancerous tumor.

It has been suggested that gallium imaging may become an obsolete technique, with indium leukocyte imaging and technetium antigranulocyte antibodies replacing it as a detection mechanism for infections. For detection of tumors, especially lymphomas, gallium imaging is still in use, but may be replaced by fludeoxyglucose PET imaging in the future.

In infections, the gallium scan has an advantage over indium leukocyte imaging (also called indium-111 white blood cell scan) in imaging osteomyelitis (bone infection) of the spine, lung infections and inflammation, and for chronic infections. In part this is because gallium binds to neutrophil membranes, even after neutrophil death. Indium leukocyte imaging is better for acute infections (where neutrophils are still rapidly and actively localizing to the infection), and also for osteomyelitis that does not involve the spine, and for abdominal and pelvic infections. Both the gallium scan and indium leukocyte imaging may be used to image fever of unknown origin (elevated temperature without an explanation). However, the indium leukocyte scan will image only the 25% of such cases which are caused by acute infections, while gallium will also localize to other sources of fever, such as chronic infections and tumors.[citation needed]

Common indications (specific uses) of gallium-67 imaging[edit]

  • Whole-body survey to localize source of fever in patients with fever of unknown origin.
  • Detection of pulmonary and mediastinal inflammation/infection, especially in the immunocompromised patient.
  • Evaluation and follow-up of active lymphocytic or granulomatous inflammatory processes such as sarcoidosis or tuberculosis.
  • Diagnosing vertebral osteomyelitis and/or disk space infection where Ga-67 is preferred over labeled leukocytes.
  • Diagnosis and follow-up of medical treatment of retroperitoneal fibrosis.
  • Evaluation and follow-up of drug-induced pulmonary toxicity (e.g. Bleomycin, Amiodarone)
  • Evaluation of patients who are not candidates for WBC scans (WBC count less than 6,000 and/or poor IV access).

Note that all of these conditions are also seen in PET scans using the less common positron-emitting isotope gallium-68, which has the same chemical characteristics as Ga-67. See gallium-68 generator.

Radiochemistry of gallium-67[edit]

Gallium-67 citrate is produced by a cyclotron. Charged particle bombardment of enriched Zn-68 is used to produce gallium-67. The gallium-67 is then complexed with citric acid to form gallium citrate. The half life of gallium-67 is 78 hours.[15] It decays by electron capture, then emits de-excitation gamma rays that are detected by a gamma camera.

Gallium-67 photopeaks:

  • Energy Abundance
  • 93 keV 40%
  • 184 keV 20%
  • 300 keV 17%
  • 393 keV 5%

Technique[edit]

The main technique uses scintigraphy to produce two-dimensional images. After the tracer has been injected, images are taken by a gamma camera at 24, 48, and in some cases, 72, and 96 hours later[citation needed]. Each set of images takes 30–60 minutes, depending on the size of the area being imaged. The resulting image will have bright areas that collected large amounts of tracer, because inflammation is present or rapid cell division is occurring. Single photon emission computed tomography (SPECT) images may also be acquired. In some imaging centers, SPECT images may be combined with computed tomography scan using either fusion software or SPECT/CT hybrid cameras to superimpose both physiological image-information from the gallium scan, and anatomical information from the CT scan.

A common injection doses is around 150 megabecquerels.[16] Imaging should not usually be sooner than 24 hours - high background at this time produces false negatives. Forty-eight-hour whole body images are appropriate. Delayed imaging can be obtained even 1 week or longer after injection if bowel is confounding. SPECT can be performed as needed. Oral laxatives or enemas can be given before imaging to reduce bowel activity and reduce dose to large bowel; however, the usefulness of bowel preparation is controversial.[17]

10% to 25% of the dose of gallium-67 is excreted within 24 hours after injection (the majority of which is excreted through the kidneys). After 24 hours the principal excretory pathway is colon. The "target organ" (organ that receives the largest radiation dose in the average scan) is the colon (large bowel).

Areas where Ga-67 normally localizes include: liver (site of highest uptake), bone marrow, spleen, salivary glands, nasopharynx, lacrimal glands, breast uptake (especially in pregnant and lactating women), kidneys and bladder (in the first 24 hours - faint uptake can still be normal for up to 72 hours), mild diffuse lung uptake (at 24 hours or less)

See also[edit]

References[edit]

  1. ^ Treves, S. Ted (2014). Pediatric nuclear medicine and molecular imaging (4th ed.). Springer. p. 480. ISBN 9781461495512. 
  2. ^ Jain, Sanjay K. (2017). Imaging Infections: From Bench to Bedside. Springer. p. 34. ISBN 9783319545929. 
  3. ^ Verberne SJ and O. P. P. Temmerman (2017). 12 - Imaging of prosthetic joint infections - Arts, J.J. Chris. Management of Periprosthetic Joint Infections (PJIs). J. Geurts, Woodhead Publishing: 259-285.
  4. ^ Verberne SJ, Raijmakers PG, Temmerman OPP (2016). "The Accuracy of Imaging Techniques in the Assessment of Periprosthetic Hip Infection: A Systematic Review and Meta-Analysis." The Journal of Bone & Joint Surgery Am 98(19): 1638-1645.
  5. ^ Termaat, MF; Raijmakers, PG; Scholten, HJ; Bakker, FC; Patka, P; Haarman, HJ (November 2005). "The accuracy of diagnostic imaging for the assessment of chronic osteomyelitis: a systematic review and meta-analysis.". The Journal of bone and joint surgery. American volume. 87 (11): 2464–71. PMID 16264122. doi:10.2106/JBJS.D.02691. 
  6. ^ Becker, W. (October 1995). "The contribution of nuclear medicine to the patient with infection". European Journal of Nuclear Medicine. 22 (10): 1195–1211. doi:10.1007/BF00800606. 
  7. ^ Love, C; Palestro, CJ (June 2004). "Radionuclide imaging of infection.". Journal of nuclear medicine technology. 32 (2): 47–57; quiz 58–9. PMID 15175400. 
  8. ^ Tsan, MF (January 1985). "Mechanism of gallium-67 accumulation in inflammatory lesions.". Journal of Nuclear Medicine. 26 (1): 88–92. PMID 3880816. 
  9. ^ Greenberg, Alex M; Prein, Joachim (2007). Craniomaxillofacial reconstructive and corrective bone surgery principles of internal fixation using AO/ASIF technique. New York: Springer. p. 79. ISBN 9780387224275. 
  10. ^ Weiner, R.E. (1996). "The mechanism of 67Ga localization in malignant disease". Nuclear Medicine and Biology. 23 (6): 745–751. PMID 8940716. doi:10.1016/0969-8051(96)00119-9. 
  11. ^ Biersack, Hans-Jürgen; Freeman, Leonard M (2007). Clinical nuclear medicine. Berlin: Springer. p. 324. ISBN 978-3-540-28026-2. 
  12. ^ Hoffer, P (1980). "Gallium: mechanisms". Journal of nuclear medicine. 21 (3): 282–5. PMID 6988551. 
  13. ^ Bryan, R Nick (2010). Introduction to the science of medical imaging. Cambridge: Cambridge University Press. p. 200. ISBN 9780521747622. 
  14. ^ Bleeker-Rovers, C. P.; Vos, F. J.; van der Graaf, W. T. A.; Oyen, W. J. G. (16 June 2011). "Nuclear Medicine Imaging of Infection in Cancer Patients (With Emphasis on FDG-PET)". The Oncologist. 16 (7): 980–991. PMC 3228133 Freely accessible. doi:10.1634/theoncologist.2010-0421. 
  15. ^ IAEA (2009). Cyclotron produced radionuclides: physical characteristics and production methods (PDF). Vienna: International Atomic Energy Agency. p. 116. ISBN 9789201069085. 
  16. ^ "Notes for Guidance on the Clinical Administration of Radiopharmaceuticals and Use of Sealed Radioactive Sources" (PDF). Administration of Radioactive Substances Advisory Committee. January 2016. Retrieved 7 September 2016. 
  17. ^ "Society of Nuclear Medicine Procedure Guideline for Gallium Scintigraphy in Inflammation" (PDF). Society of Nuclear Medicine. 2 June 2004. Retrieved 7 September 2016. 
Retrieved from "https://en.wikipedia.org/w/index.php?title=Gallium_scan&oldid=790205752"