A Triphasic (or three phase) Bone Scan is a diagnostic tool used in nuclear medicine. It can be used for a variety of purposes, including the diagnosis of otherwise difficult to detect fractures and the diagnosis of infection and pain in the bone.
For many years it has also been used, somewhat controversially, as an objective tool for diagnosing Complex Regional Pain Syndrome Type 1 (CRPS).
How does a Triphasic Bone Scan work?
Prior to undergoing the scan, a patient is given an intravenous injection of a radioactive tracer substance that has a tendency to concentrate in bones. This substance is harmless to the patient. A Gamma Camera is then used to create images in three phases from the radiation given off by the tracer in the selected area of the body.
The first phase images are taken immediately and record blood flow through the selected area of bone.
The second phase images are usually taken a few minutes later and record blood pooling, which may indicate inflammation.
The third “delayed” phase images are usually taken at least two hours later. By then, much of the tracer substance will have been metabolised by the patient’s body. An analysis of the amount of the tracer remaining in the bones is therefore indicative of the rate of metabolism of tissue within the bones.
Can a Triphasic Bone Scan diagnose CRPS?
On a Triphasic Bone Scan, CRPS 1 often shows increased blood flow, blood pooling and delayed metabolism in the affected limb or limbs. However, reliance only on a Triphasic Bone Scan for the diagnosis of CRPS is controversial.
One area of controversy involves the role of the images taken during the blood flow and blood pooling phases. A number of studies* have been published in this regard, but their conclusions as to the relevance of these images for a diagnosis of CRPS varies considerably.
Other research challenges the lack of available data supporting the diagnostic value of the delayed metabolism phase.
In 2012, a paper** published in the British Journal of Anaesthesia looked “to re-evaluate the diagnostic performance of [Triphasic Bone Scanning], and to suggest new [Triphasic Bone Scanning] criteria based on the [Budapest Criteria].”
Noting that particular patterns in the three phases of the scan may be associated with a diagnosis of CRPS, the conclusion nevertheless was that the diagnostic value of a positive Triphasic Bone Scan “is low from the view point of the Budapest research criteria. Our findings suggest that a diagnosis of CRPS using the Budapest research criteria should be considered when decreased patterns…are observed during Phases I and II.”
In other words, the Budapest Criteria remain the ultimate diagnostic tool for CRPS and reliance should not be placed solely on the results of a Triphasic Bone Scan.
You may also be interested in the following articles:
* Davidoff G, Werner R, Cremer S, Jackson MD, Ventocilla C, Wolf L. Predictive value of the three-phase technetium bone scan in diagnosis of reflex sympathetic dystrophy syndrome.Arch Phys Med Rehabil. 1989;70:135–137.
* O’Donoghue JP, Powe JE, Mattar AG, Hurwitz GA, Laurin NR. Three-phase bone scintigraphy. Asymmetric patterns in the upper extremities of asymptomatic normals and reflex sympathetic dystrophy patients. Clin Nucl Med. 1993;18:829–836. doi: 10.1097/00003072-199310000-00002.
* Fournier RS, Holder LE. Reflex sympathetic dystrophy: diagnostic controversies. Semin Nucl Med. 1998;28:116–123. doi: 10.1016/S0001-2998(98)80022-6.
* Kozin F, Soin JS, Ryan LM, Carrera GF, Wortmann RL. Bone scintigraphy in the reflex sympathetic dystrophy syndrome. Radiology. 1981;138:437–443.
** Moon JY, Park SY, Kim YC, Lee SC, Nahm FS, Kim JH, Kim H, Oh SW. Analysis of patterns of three-phase bone scintigraphy for patients with complex regional pain syndrome diagnosed using the proposed research criteria (the ‘Budapest Criteria’). Volume 108, Issue 4 655-661.