Direct comparison between whole body PET and combined PET/CT 11C-Methionine imaging in early detection of skeletal metastatic lesions

Abstract

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Objectives: To evaluate the role of 11C-Methionine PET imaging in early detection of skeletal metastatic lesions. Also to evaluate the added value of combined PET-CT imaging in detection of bone metastasis over WB PET imaging (without attenuation correction). Methods: In this retrospective study we searched among 222 PET studies done for oncologic patients. All studies were performed with 11C-Methionine. 12 cases were found to fulfill the study inclusion criteria which includes; 1) The presence of suspicious bone metastasis, 2) All patients had both WB PET imaging and PET-CT imaging in the same setting. 3) All patients had a follow up Bone Scan or CT scan. For more easy interpretation; all suspected bone lesions were classified according to the degree of tracer uptake and shape of activity into high and low (or equivocal) possibility metastatic lesions. Results: 16 bone lesions were detected by PET-CT imaging. 11 bone lesions were detected by WB PET imaging. 8 out of the 16 lesions detected by PET-CT were classified as high possibility and 8 as low possibility. 4 out of the 8 high possibility PET/CT lesions (50% of high possibility lesions) were proved to be metastatic by follow up method. The remaining 4 high possibility and 7 out of the 8 low possibility PET/CT lesions (87.5% of low possibility lesions) were proved to be non metastatic. 6 out of the 11 lesions detected by WB PET were classified as high possibility, with 3 of them (50%) proved to be metastatic. 4 out of the 5 low possibility WB PET lesions (80%) proved to be non-metastatic. Conclusions: In our study the attenuation correction used with PET-CT showed a limited effect on improving the detection of skeletal lesions. Classification of WB PET or PET-CT lesions as high and low (or equivocal) possibility could improve the diagnosis of skeletal metastatic lesions.