Abstract
We report a case of accidental local 99mTc‐MDP uptake in left lung on bone scan without pulmonary parenchymal abnormality on SPECT/CT. The abnormal uptake disappeared on repeated bone scan and SPECT/CT after 3 days. It is speculated that the high radioactivity focus is a microthrombus in pulmonary artery.
Keywords: 99mTc‐MDP, bone scan, lung, microembolism, SPECT/CT
1. CASE REPORT
An 80‐year‐old man presented with low back pain 3 months ago and lumbar CT showed the first lumbar vertebral compression fracture. After conservative treatment, the symptoms did not relieve significantly. Recently, he complained of both lower extremities discomfort accompanied with walking difficulty and was admitted in hospital. Lumbar MRI showed spinal stenosis associated with the first lumbar vertebral compression fracture. Whole‐body bone scan was performed to rule out possible skeletal neoplasms. It was performed 2 h after intravenous administration of 25.0 mCi (925 MBq) 99mTc methylene diphosphonate (99mTc‐MDP) and showed increased radioactivity in the first lumbar vertebrae; additionally, a localized radioactivity focus was observed near the eighth posterior rib on the left side (Figure 1A, black arrow). To clarify the location and characteristics of the lesion, single photon emission computed tomography/computed tomography (SPECT/CT) was performed, and the lesion was found located in the left lung (Figure 1B, black arrow). However, there were no abnormalities in the corresponding pulmonary parenchymal site on CT (Figure 1C,D, red arrows). Medical history and physical examination revealed no history of cancer and pulmonary disorder, except serum D‐dimer was increased (433 ng/ml, normal 0‐225 ng/ml). To further explore the cause of pulmonary 99mTc‐MDP uptake, bone scan and SPECT/CT were repeated after 3 days and then the intrapulmonary high radioactivity lesion disappeared (Figure 1E–H). To re‐test the serum D‐dimer, it has returned to the normal range.
FIGURE 1.
Whole‐body bone scan showing a local 99mTc‐MDP uptake near the left eighth posterior rib (A, black arrow). Chest SPECT/CT showing the focus was in the left lung (B, black arrow), however, no abnormalities was found in the corresponding pulmonary parenchymal site (C, D, red arrows). The abnormal uptake disappeared on repeated bone scan (E) and SPECT/CT (F–H) 3 days later
2. DISCUSSION
99mTc‐MDP is a radioactive imaging agent for bone, however, extraosseous 99mTc‐MDP uptake could be found in neoplastic diseases. 1 In previous reports, 2 pulmonary diffuse 99mTc‐MDP uptake in bone scan was often seen in various types of calcifications, most of which were irreversible. In myelodysplastic syndrome, 99mTc‐MDP uptake in lungs was attributed to hypercalcemia, metastatic calcification, vasculitis, amyloidosis. 3 Yoon 4 reported an occasional multiple focal uptakes of 99mTc‐MDP in both lungs in a juvenile bone scan, which was assumed to be microembolism at pulmonary arterioles by blood clots trapping 99mTc‐MDP. 5 Additionally, there were several reports of 18F‐FDG high uptake in lungs without abnormality on CT, which were also speculated to be microembolism at pulmonary arterioles. 6 , 7 In this case, the patient had an isolated 99mTc‐MDP uptake in lung that disappeared after a few days; what's more, the increased D‐dimer at that time was supportive to the speculation that it was the microthrombus in the pulmonary arteriole.
3. CONCLUSION
Pulmonary arterial microembolization could be considered as a cause of isolated 99mTc‐MDP uptake in lungs without pulmonary abnormalities on CT, especially in those patients with D‐dimer increased. SPECT/CT is a dependable detection method to the isolated pulmonary focus of 99mTc‐MDP uptake, which might be difficult to be diagnosed by bone scan.
AUTHOR CONTRIBUTIONS
Yao Chen, Yu Ning and Xiaoji Liu involved in data collection, literature search, and manuscript preparation. Min Cai and Sijin Li involved in revision and review of manuscripts. All authors read and approved the final manuscript.
FUNDING INFORMATION
The study was supported by China Postdoctoral Science Foundation (No. 2020M670704) and Fundamental Research Program of Shanxi Province (No. 202103021224377).
CONFLICT OF INTEREST
The authors declare that there is no conflict of interest.
ETHICAL APPROVAL
The article describes a case report. Therefore, no additional permission from our Ethics Committee was required.
CONSENT
Written informed consent was obtained from the patient to publish this report in accordance with the journal's patient consent policy.
ACKNOWLEDGMENTS
The authors thank the patient for granting permission to publish this case imaging, and we appreciate all those who facilitated this work.
Chen Y, Ning Y, Liu X, Cai M, Li S. A case of accidental local pulmonary 99mTc‐MDP uptake on bone SPECT/CT . Clin Case Rep. 2022;10:e06656. doi: 10.1002/ccr3.6656
Yao Chen and Yu Ning contributed equally to this work.
Contributor Information
Min Cai, Email: c.m1113@163.com.
Sijin Li, Email: lisjnm123@163.com.
DATA AVAILABILITY STATEMENT
Data sharing is not applicable to this article as no new data were created or analyzed in this study.
REFERENCES
- 1. Zhang L, He Q, Zhou T, et al. Accurate characterization of (99m)Tc‐MDP uptake in extraosseous neoplasm mimicking bone metastasis on whole‐body bone scan: contribution of SPECT/CT. BMC Med Imaging. 2019;19:44. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Castaigne C, Martin P, Blocklet D. Lung, gastric, and soft tissue uptake of Tc‐99m MDP and Ga‐67 citrate associated with hypercalcemia. Clin Nucl Med. 2003;28:467‐471. [DOI] [PubMed] [Google Scholar]
- 3. Mogharrabi M, Javadi H, Assadi M. Bilateral lung 99mTc‐MDP uptake on the bone scintigraphy in the myelodysplastic syndromes (MDS). Clin Nucl Med. 2013;38:372‐374. [DOI] [PubMed] [Google Scholar]
- 4. Yoon SH, Song HS, Choi BH, Lee SJ, Yoon JK, An YS. Incidental multiple focal uptakes of Tc‐99m MDP in both lungs without lung parenchymal abnormality. Clin Nucl Med. 2011;36:221‐223. [DOI] [PubMed] [Google Scholar]
- 5. Zanglis A, Andreopoulos D, Baziotis N. Trapping of technetium‐99m albumin macroaggregate and other four radiopharmaceuticals by blood clots in vitro. Hell J Nucl Med. 2007;10:24‐25. [PubMed] [Google Scholar]
- 6. Farsad M, Ambrosini V, Nanni C, et al. Focal lung uptake of 18F‐fluorodeoxyglucose (18F‐FDG) without computed tomography findings. Nucl Med Commun. 2005;26:827‐830. [DOI] [PubMed] [Google Scholar]
- 7. Karantanis D, Subramaniam RM, Mullan BP, Peller PJ, Wiseman GA. Focal F‐18 fluoro‐deoxy‐glucose accumulation in the lung parenchyma in the absence of CT abnormality in PET/CT. J Comput Assist Tomogr. 2007;31:800‐805. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Data sharing is not applicable to this article as no new data were created or analyzed in this study.