Assessing bone metastases is often beyond the scope of plain - film radiography, and nuclear imaging in particular with bone scintigraphy has proved the mainstay for detection of bony disease for over 40 years. Bone scanning with 99mTechnetium - labeled diphosphonates relies on the detection of pathological osteoblastic response elicited from malignant cells. This technique offers the advantage of whole body examination, low cost, availability and high sensitivity. However, it suffers from relative low specificity. The addition of single-photon emission computed tomography (SPECT) to bone scintigraphy has markedly improved the diagnostic benefit. Although the accuracy of SPECT is significantly higher than that of planar scintigraphy, there is still room for improvement of anatomic localization and morphological characterization, a limitation that has currently been mainly overcome with the upcoming of combined SPECT-CT (computed tomography).Positron emission tomography (PET), a modality with higher spatial resolution than that of SPECT can be particularly helpful in detecting small lesions. Moreover, PET imaging using various specific radiotracers has the advantage of detecting malignant disease in both bone and soft tissues. It is highly sensitive mainly in detecting early bone marrow as well as for diagnosing lytic bony metastases and can be also reliably used to monitor therapy response. In this review, we present the current role of SPECT and PET in the imaging of skeletal metastases from prostate cancer.

272 Objectives The diagnostic potential of PET/CT imaging with BAY1075553 ((2RS,4S)-2-[18F]Fluoro-4-phosphonomethyl-pentanedioic acid), a novel PET tracer with potential to bind with prostate-specific membrane antigen (PSMA), is compared to 18F - Fluorcholine (FCH) in prostate cancer. Methods 12 patients (9 primary staging, 3 Re-staging) with proven prostate cancer were included into this study. The mean PSA in the primary staging and restaging groups was 21.5± 12 ng/ml and 73.6 ± 33 ng/ml, respectively. The median Gleason score was of 8 in both groups. Acquisition started 30 seconds post intravenous injection of 300 MBq with dynamic PET images in the pelvic region during 12 minutes Static semi - whole body was performed immediately after the dynamic acquisition. Radical prostatectomy and ePLND was performed in the primary staging patients. Results In the prostate gland, there was a correlation between detected lesions by means of both imaging modalities and histopathological results. The mean SUVmax in the prostate gland was higher on FCH PET (6.95±1.6) than that on BAY1075553 PET (5.6±2.4), p=ns. FCH PET was able to detect a higher number of positive LNs compared to BAY1075553 PET. There was a correlation between both modalities in the detection of bone metastases, however, BAY1075553 could not detect a bone-marrow metastasis found in 1 patient. Furthermore, degenerative bone lesions showed intensive uptake of BAY1075553. Conclusions PET/CT using BAY1075553 was able to detect prostate cancer in patients with primary and advanced disease. However, PET/CT using FCH showed superior results compared to BAY1075553 in particular with respect to detection of LN and bone-marrow metastases

1913 Objectives To evaluate the potential of 18F fluoromethylcholine (FCH) PET/CT in the assessment of suspected recurrent prostate cancer in patients with biochemical evidence of recurrence and to correlate its diagnostic accuracy with PSA levels. Methods This study included 240 prostate cancer patients at PSA relapse after initial treatment who had undergone FCH PET/CT for the evaluation of recurrent disease. The mean PSA level was 41.2±319.5 ng/ml. Hormonal treatment(HT) was performed in 151(63%) cases after initial treatment. Imaging was performed on an integrated PET/CT system. Acquisition started 1 minute post intravenous injection of FCH (4Mbq/kg/bw) with dynamic PET images in the pelvic. Static acquisition from thigh to the base of skull was performed 10 min post injection, respectively. The final diagnosis of positive PET lesions was based on histopathological findings or a consensus based on clinical findings, additional imaging modalities and follow-up imaging modalities with a mean time interval of 5.3 months. Results FCH PET/CT was able to correctly detect malignant lesions in 160(66%) patients. The mean PSA level at the time of imaging was 60.3±389.0 ng/ml in patients with positive FCH PET/CT compared to 2.3±3.5 ng/ml in patients with negative FCH PET/CT studies (P=0.06). Although the finding does not reach statistical significance;however, there is a clear trend toward higher PSA levels with positive FCH results. FCH PET/CT were positive in 90.8% of patients with PSA levels ≥4.0 ng/ml while it was 42.9% in patients with PSA levels Conclusions Our data suggest that FCH PET/CT can reliably detect recurrent disease in prostate cancer patients especially in case of PSA level ≥2.5 ng/ml