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Year : 2012  |  Volume : 27  |  Issue : 1  |  Page : 42-44  

Extraosseous accumulation of bone scan tracer 99m Tc-methylene diphosphonate in a phlebolith

Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, Parel, Mumbai, India

Date of Web Publication15-Mar-2013

Correspondence Address:
Venkatesh Rangarajan
Department of Nuclear Medicine and Molecular Imaging, Tata Memorial Hospital, Parel, Mumbai, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-3919.108857

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Uptake in non-osseous, non-urologic tissues is occasionally found in the performance of bone scintigraphy. These uptakes reflect an atypical interaction between the radiopharmaceutical and the patient. Knowledge of the rare extraskeletal uptakes and their clinical relevance helps in better interpretation of bone scans. We report an unusual occurrence of extraosseous accumulation of 99m Tc-methylene diphosphonate in a phlebolith in bone scan, confirmed with the aid of photon emission computed tomography and computed tomography.

Keywords: Bone scan, extraosseous uptake, phlebolith, SPECT-CT, 99m Tc-methylene diphosphonate

How to cite this article:
Kulkarni M, Agrawal A, Zade A, Purandare N, Shah S, Rangarajan V. Extraosseous accumulation of bone scan tracer 99m Tc-methylene diphosphonate in a phlebolith. Indian J Nucl Med 2012;27:42-4

How to cite this URL:
Kulkarni M, Agrawal A, Zade A, Purandare N, Shah S, Rangarajan V. Extraosseous accumulation of bone scan tracer 99m Tc-methylene diphosphonate in a phlebolith. Indian J Nucl Med [serial online] 2012 [cited 2022 May 19];27:42-4. Available from:

   Introduction Top

Bone scintigraphy is an important modality for the examination of various pathological conditions of the skeletal system. Radionuclide bone imaging is quick, relatively inexpensive, widely available, and exquisitely sensitive and is invaluable in the diagnostic evaluation of numerous pathological conditions. The procedure is performed with 99m Technetium ( 99m Tc)-labeled diphosphonates. These compounds accumulate rapidly in bone, and by 2-6 h after injection, about 50% of the injected dose is in the skeletal system. [1] The extraosseous uptake is often an unexpected finding on the bone scan. [2] 99m Tc-methylene diphosphonate ( 99m Tc-MDP) imaging, customarily directed toward identifying altered skeletal metabolism, has been used extensively to image a variety of extraosseous lesions, especially heterotopic ossification [3] and metabolic, metastatic calcification. [4]

We report a rare case of accumulation of bone scintigraphy tracer in a phlebolith in a patient of adenocarcinoma of lung.

   Case Report Top

A 43-year-old female patient, known case of adenocarcinoma of right lung was referred for a 99m Tc-MDP bone scan with complaint of persistent low backache since 3 months. A whole body 99m Tc-MDP bone scan was performed. The scan showed abnormal, focal increased tracer uptake in left pelvic cavity, not localizing to any bone of the skeleton [[Figure 1]a and b, arrows]. All the bones of the axial and appendicular skeleton showed normal tracer uptake. The uptake was persistent even in post-void imaging done after adequate hydration, giving us a clue that it was not due to tracer hold up in the ureter. On single photon emission computed tomography and computed tomography (SPECT-CT) imaging, the focal tracer uptake localized to a small focus of calcification in the left pelvic cavity away from the ureter [[Figure 2], arrow]. An additional ultrasonography of the pelvis confirmed that there was no ureteric calculus [Figure 3]. Review of the patient's recent contrast-enhanced computed tomography revealed a phlebolith in left iliac vein (CT Hounsfield unit: 338). Thus, we concluded the extraosseous 99m Tc-MDP uptake was due to phlebolith in the left iliac vein.
Figure 1: Planar bone scan (a and b) of a 43-year-old female patient, a known case of adenocarcinoma of right lung. Focal, intense tracer uptake seen in left pelvic cavity (arrow)

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Figure 2: Correlative single photon emission computed tomography and computed tomography fusion imaging localized this uptake to a phlebolith in left iliac vein (arrow)

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Figure 3: Ultrasonography of the pelvis showing ureteric jets bilaterally (arrows), ruling out obstruction (calculus) in the ureter

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   Discussion Top

Bone scintigraphy is one of the most commonly performed scintigraphic procedures. 99m Tc-MDP, a bone scan tracer, has rapid blood clearance, excellent in vivo chemical stability, and a high bone-to-soft tissue ratio, which are ideal for bone imaging. Although 99m Tc-MDP is customarily used to evaluate skeletal pathological conditions, its excellent clearance from normal soft tissues allows the detection of abnormal extraskeletal 99m Tc-MDP accumulation. [5]

It is hypothesized that 99m Tc-MDP and its analogues bind to bone by adsorption to the surface of the hydroxyapatite crystal. [6] While in soft tissue, calcium localizes through a limited number of common pathways. These pathways result in uptake of 99m Tc-MDP through what is believed to be chemisorption of the radiopharmaceutical onto the surface of the calcium salts. [7]

Phleboliths are deposits which develop in the wall of a vein and are composed of calcium or lime. These are most commonly seen in the lower pelvis and sometime occur in large numbers. They are of no particular pathological significance. These are usually symptomless and are usually incidentally detected. They are often confused with ureteric stones when seen around the urinary bladder in the pelvic cavity. However, on plain radiographs, these can be distinguished from a calculus due to the presence of a translucent center and circular or oval shape. [8],[9],[10]

Bone scan tracer uptake in a phlebolith has been described in past. [11] Uptake in phlebolith is an example of tracer localization in dystrophic calcification. Dystrophic calcification occurs in patients with normal Ca 2 + and PO 4 levels and refers to Ca 2 + deposition in tissues secondary to histological disruption caused by trauma, ischemia, or cellular necrosis or in the enzymatic necrosis of fat. It is thought that calcium ion binds to phospholipids present in membrane bound vesicles, phosphatases generate phosphate groups which in turn bind to the calcium, and the cycle is repeated until local concentrations are elevated and crystals begin to form. Hyaline collagen degeneration, a consequence of tissue damage, is particularly associated with Ca 2 + deposition.Similar mechanism operates in other known causes of extraskeletal bone scan tracer uptake in tissue infarction, deep vein thrombosis, scars, and dermatomyositis. [12]

To conclude, we report a rare case of extraosseous uptake of bone scan tracer in a phlebolith. With growing use of integration of CT with SPECT, Nuclear Medicine physicians should become aware of such anatomical changes and variants so as to avoid misinterpretation. The awareness of the underlying pathophysiological basis of these changes and uptake of MDP in extraosseous soft tissue can significantly enhance the interpretation and diagnostic value of bone scintigraphy.

   References Top

1.Love C, Din AS, Tomas MB, Kalapparambath TP, Palestro CJ. Radionuclide bone imaging: An illustrative review. Radiographics 2003;23:341-58.  Back to cited text no. 1
2.Sood A, Seam RK, Sethi S, Gupta M. Diffuse hepatic and splenic Tc-99m MDP tracer uptake in case of multiple myeloma. Indian J Nucl Med 2010;25:70-2.  Back to cited text no. 2
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3.Muheim G, Donath A, Rossier AB. Serial scintigrams in the course of ectopic bone formation in paraplegic patients. Am J Roentgenol Radium Ther Nucl Med 1973;118:865-9.  Back to cited text no. 3
4.Choy D, Murray IP. Metastatic visceral calcification identified by bone scanning. Skeletal Radiol 1980;5:151-9.  Back to cited text no. 4
5.Subramanian G, McAfee JG, Blair RJ, Kallfelz FA, Thomas FD. Technetium-99m-methylene diphosphonate-A superior agent for skeletal imaging: Comparison with other technetium complexes. J Nucl Med 1975;16:744-55.  Back to cited text no. 5
6.Galasko CS. Mechanism of uptake of bone imaging isotopes by skeletal metastases. Clin Nucl Med 1980;5:565-8.  Back to cited text no. 6
7.Vallabhajosula S, Owunwanne A. Pathophysiology and mechanisms of radiopharmaceutical localization. In: Elgazzar A, editor. The Pathophysiologic Basis of Nuclear Medicine. Berlin, Germany: Springer-Verlag Berlin Heidelberg; 2006. p. 35.  Back to cited text no. 7
8.Rice RE. The plain film of the abdomen. In: Taveras JM, Ferrucci JT, editors. Radiology Diagnosis-Imaging-Intervention. Vol. 4, Philadelphia: Lippincott; 1992:ch. 3:5.  Back to cited text no. 8
9.Kim JC. Central lucency of pelvic phleboliths: Comparison of radiographs and noncontrast helical CT. Radiol 1998;207:363-7.  Back to cited text no. 9
10.Bell TV, Fenlon HM, Davison BD, Ahari HK, Hussain S. Unenhanced helical CT criteria to differentiate distal ureteral calculi from pelvic phleboliths. Eur Radiol 2005;15:65-70.  Back to cited text no. 10
11.Sohn MH, Jeong YJ, Lim ST, Kim DW, Jeong HJ, Yim CY. Tc-99m methylene diphosphonate uptake by numerous phleboliths in the lower extremity detected incidentally during bone scintigraphy. Clin Nucl Med 2010;35:289-92.  Back to cited text no. 11
12.Zuckier LS, Freeman LM. Nonosseous, nonurologic uptake on bone scintigraphy: Atlas and analysis. Semin Nucl Med 2010;40:242-56.  Back to cited text no. 12


  [Figure 1], [Figure 2], [Figure 3]


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