RESUMO
OBJECTIVES: 99mTc-PSMA SPECT/CT is a cost effective alternative for 68Ga-PSMA PET/CT. The aim of this study was to directly compare these two techniques in patients with prostate cancer. METHODS: 28 man with prostate cancer were studied using 99mTc-PSMA SPECT/CT and 68Ga-PSMA PET/CT in a short time period (<60 days). No intervention was done between the studies. Whole body PET/CT was done 60 minutes after IV injection of 2 MBq/Kg of 68Ga-PSMA. 99mTc-PSMA kit (PSMA I+S) was used for SPECT/CT and whole body imaging was performed 4 hours after IV injection of 740 MBq of 99mTc-PSMA. Images were interpreted independently and the results of each imaging were recorded. RESULTS: The mean age of the patients was 64.7±9.6 years old and the mean time difference between two sets of images was 16.6±13.5 days. Abnormal uptake was seen in 25 (89.2%) patients by 68Ga-PSMA PET/CT and 20 (71.4%) patients with 99mTc-PSMA SPECT/CT. No patients with positive 99mTc-PSMA SPECT/CT had negative 68Ga-PSMA PET/CT. The mean number of detected lesions was 26.07±27.5 by 68Ga-PSMA PET/CT and 10.52±10.99 by 99mTc-PSMA SPECT/CT (P<0.001). Detection of lymph nodes and bone metastases were not significantly different between two sets of imaging (P>0.05), however 68Ga-PSMA PET/CT were more successful in detection of prostate bed lesions compared to 99mTc-PSMA scan. Interestingly, no patient with PSA level of >2.1 ng/ml had discordant result between two sets of images. CONCLUSION: 99mTc-PSMA SPECT/CT is as accurate as 68Ga-PSMA PET/CT in M staging, however 68Ga-PSMA PET/CT detected more lesions compared to 99mTc-PSMA SPECT/CT. Detection rate was not significantly different between two techniques in patients with PSA levels>2.1 ng/ml.
RESUMO
F-18 FDG is the most widely used tracer in molecular imaging and it is applied for many purposes mainly in malignant diseases. Incidental finding are common in FDG-PET/CT imaging and includes benign and malignant lesions. Among the rare tumors , adrenal oncocytomas are uncommon findings and incidental findings of thyroid malignancies are not rare. Oncocytoma is a rare adrenocortical tumor and majority of bulky adrenal tumors are benign with uncertain incident of malignancy. In this study, we are reporting a 37-year-old man with two incidental malignancies detected by FDG-PET-CT. He has no symptoms has no blood and hormonal abnormalities. The scan demonstrated intense heterogeneous FDG uptake within the bulky oval shaped lesion in the left adrenal gland. Accordingly, open adrenalectomy was performed and diagnosis of adrenocortical carcinoma oncocytic type was established. Furthermore, a focal FDG uptake was identified in the right thyroid lobe and histopathology findings were consistent with well-differentiated papillary thyroid cancer. FDG plays a great role in identifying primary rare lesions and also detection of incidental findings at unexpected sites.
