Pulmonary Tc^99m-PSMA uptake in asymptomatic COVID-19 patient: incidental finding in SPECT/CT study

Abstract

Background

As there are comparative studies between ⁶⁸Ga-PSMA and ^99mTc-PSMA and spectrum of PSMA expression, this is the first case report that notifies distribution of ^99mTc-PSMA on COVID-19 pneumonia era on the literature.

Case presentation

An asymptomatic 70-Y-old male who is known case of prostate adenocarcinoma underwent initial staging. SPECT/CT of the chest region reveals bilateral peripheral multifocal ground glass opacities which shows ^99mTc-PSMA uptake. Diagnosis of corona virus was confirmed by positive RT-PCR.

Discussion

Unexclusive role of radiotracers in nuclear medicine has an importance for wide range of applications. Comparison between ⁶⁸Ga-PSMA and ^99mTc-PSMA in detection of metastatic disease in prostate cancer is also under evaluation.

Conclusions

This case implicates possible role of PSMA imaging in inflammation/infection process as well as necessity for lung review in hybrid imaging especially during this recent pandemic.

Background

A spectrum of PSMA expression in benign and malignant findings such as infectious/inflammatory process was reported [1]. There are few reports for ⁶⁸Ga-PSMA uptake in COVID-19 pneumonia [2]. But there is no previously reported case of ^99mTC-PSMA on COVID-19 as our knowledge. It is also decisive for nuclear medicine physician to know the other possible reasons of ^99mTC-PSMA uptake for the best interpretation.

Case presentation

A 70-Y-old male who have biopsy proven prostate adenocarcinoma with Gleason score of 6 (3 + 3) and PSA level 36 ng/ml underwent a ^99mTc-PSMA SPECT-CT for initial staging.

A dose of 20 mci (740 MBq) was injected intravenously, and 4 h later, whole-body images and thoracoabdominopelvic SPECT/CT images were performed using the Siemens Symbia Intevo SPECT/CT dual-head variable angle gamma camera.

SPECT/CT scan images revealed heterogeneous PSMA uptake in prostate lobes consistent with previously known malignancy. An incidental finding of multifocal, bilateral and peripheral ground-glass opacities in lungs with mild ^99mTC-PSMA uptake are noticed (Fig. 1). Otherwise, no abnormal PSMA avid lesions are seen throughout the body.

Fig. 1

a Whole-body 99mTc-PSMA study with faint uptake in the chest region as well as physiologic distribution of radiotracer. b SPECT reveals mild peripheral 99mTC-PSMA uptake in the lung fields. c CT shows multifocal, bilateral and peripheral ground-glass opacities in lungs. d Fused SPECT/CT shows the PSMA uptake is matched by ground-glass opacities in the lung (left lung COVID-related consolidation also shows the same uptake just it is not apparent in this cut due to respiratory motion misregistration)

Regarding viral outbreak, the first diagnosis is COVID-19 pneumonia. Although the patient had no any respiratory symptoms, RT-PCR was performed and the result was positive.

Discussion

Unexclusive role of radiotracers in nuclear medicine has an importance in wide range of applications. Not to misinterpret, every 99mTc-PSMA uptake in lung fields as metastasis in staging of a prostate adenocarcinoma is crucial. Comparison between 68Ga-PSMA and 99m Tc-PSMA in detection of metastatic disease in prostate cancer is still under evaluation [3, 4]. There are few case reports of incidental detection of COVID-19-associated pneumonia by different tracers on nuclear medicine examinations such as 68Ga-PSMA PET/CT, 18F-FDG PET/CT and thyroid scintigraphy [5,6,7,8].

Conclusion

This case implicates the possible role of PSMA imaging in active inflammatory/infectious process. This may be useful for evaluation of response to treatment of inflammatory disease. Also, as many COVID-19 patients are asymptomatic, it is necessary for nuclear medicine departments to review lung window filed in hybrid imaging even in unrelated pathologies.