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Purpose: Radiolabelled somatostatin analogues targeting somatostatin receptors (SSR) are well established for combined positron emission tomography/computer tomography (PET/CT) imaging of neuroendocrine tumours (NET). [18F]SiTATE has recently been introduced showing high image quality, promising clinical performance and improved logistics compared to the clinical reference standard 68Ga-DOTA-TOC. Here we present the first dosimetry and optimal scan time analysis. Methods: Eight NET patients received a [18F]SiTATE-PET/CT (250 ± 66 MBq) with repeated emission scans (10, 30, 60, 120, 180 min after injection). Biodistribution in normal organs and SSR-positive tumour uptake were assessed. Dosimetry estimates for risk organs were determined using a combined linear-monoexponential model, and by applying 18F S-values and reference target masses for the ICRP89 adult male or female (OLINDA 2.0). Tumour-to-background ratios were compared quantitatively and visually between different scan times. Results: After 1 h, normal organs showed similar tracer uptake with only negligible changes until 3 h post-injection. In contrast, tracer uptake by tumours increased progressively for almost all types of metastases, thus increasing tumour-to-background ratios over time. Dosimetry resulted in a total effective dose of 0.015 ± 0.004 mSv/MBq. Visual evaluation revealed no clinically relevant discrepancies between later scan times, but image quality was rated highest in 60 and 120 min images. Conclusion: [18F]SiTATE-PET/CT in NET shows overall high tumour-to-background ratios from 60 to 180 min after injection and an effective dose comparable to 68Ga-labelled alternatives. For clinical use of [18F]SiTATE, the best compromise between image quality and tumour-to-background contrast is reached at 120 min, followed by 60 min after injection. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to identify prostate-specific antigen (PSA) threshold levels, as well as PSA velocity, progression rate and doubling time in relation to the detectability and localization of recurrent lesions with [F]fluorocholine (FC) PET/CT in patients after radical prostatectomy. Methods: The study group comprised 82 consecutive patients with biochemical relapse after radical prostatectomy. PSA levels measured at the time of imaging were correlated with the FC PET/CT detection rates in the entire group with PSA velocity (in 48 patients), with PSA doubling time (in 47 patients) and with PSA progression (in 29 patients). Results: FC PET/CT detected recurrent lesions in 51 of the 82 patients (62%). The median PSA value was significantly higher in PET-positive than in PET-negative patients (4.3 ng/ml vs. 1.0 ng/ml; p < 0.01). The optimal PSA threshold from ROC analysis for the detection of recurrent prostate cancer lesions was 1.74 ng/ml (AUC 0.818, 82% sensitivity, 74% specificity). Significant differences between PET-positive and PET-negative patients were found for median PSA velocity (6.4 vs. 1.1 ng/ml per year; p < 0.01) and PSA progression (5.0 vs. 0.3 ng/ml per year, p < 0.01) with corresponding optimal thresholds of 1.27 ng/ml per year and 1.28 ng/ml per year, respectively. The PSA doubling time suggested a threshold of 3.2 months, but this just failed to reach statistical significance ( p = 0.071). Conclusion: In a study cohort of patients with biochemical recurrence of prostate cancer after radical prostatectomy there emerged clear PSA thresholds for the presence of FC PET/CT-detectable lesions. [ABSTRACT FROM AUTHOR]

To compare the diagnostic impact of 68Ga-DOTA-TATE and 18F-DOPA PET in the diagnosis of well-differentiated metastatic neuroendocrine tumours (NET). PET/CT using both 68Ga-DOTA-TATE and 18F-DOPA was performed in 25 patients with histologically proven metastatic NET (nine gut, five pancreas, six lung, one paranasal sinus, four with unknown primary). Analyses of PET examinations were patient-based (pathological uptake: yes/no), and based on tumour regions (primary tumour if present and metastases of liver, lung, bones and lymph nodes). The results were compared with the results of contrast enhanced CT, and with plasma serotonin levels, which were available in 24 of the 25 patients. Patient-based sensitivities were 96% for 68Ga-DOTA-TATE PET and 56% for 18F-DOPA PET. 68Ga-DOTA-TATE PET delineated metastases in 54 of 55 positive metastatic tumour regions in contrast to 29 of 55 delineated by 18F-DOPA PET. Overall, 68Ga-DOTA-TATE was superior to 18F-DOPA in 13 patients (two patients showed fewer positive tumour regions with 18F-DOPA PET). The results were comparable in 12 patients. In 13 of 24 patients, plasma serotonin levels were elevated, and 11 of these 13 patients showed pathological uptake of 18F-DOPA. Of the 11 patients with normal levels of serotonin, 3 also showed positive 18F-DOPA uptake. In patients positive for 18F-DOPA uptake the maximum tumour SUVs were correlated with the levels of serotonin ( r=0.66, p=0.01). In this study 68Ga-DOTA-TATE PET proved clearly superior to 18F-DOPA PET for detection and staging of NET. 18F-DOPA uptake tended to be increased in those patients with elevated plasma serotonin. We conclude that 18F-DOPA PET should be employed in patients with NET with negative 68Ga-DOTA-TATE PET and elevated plasma serotonin. [ABSTRACT FROM AUTHOR]

The value and limitations of 11C-choline PET and PET/CT for the detection of prostate cancer remain controversial. The aim of this study was to investigate the diagnostic efficacy of 11C-choline PET and PET/CT in a large group of patients with suspected prostate cancer. Fifty-eight patients with clinical suspicion of prostate cancer underwent 11C-choline PET (25/58, Siemens ECAT Exact HR+) or PET/CT (33/58, Philips Gemini) scanning. On average, 500 MBq of 11C-choline was administered intravenously. Studies were interpreted by raters blinded to clinical information and other diagnostic procedures. Qualitative image analysis as well as semiquantitative SUV measurement was carried out. The reference standard was histopathological examination of resection specimens or biopsy. Prevalence of prostate cancer in this selected patient population was 63.8% (37/58). 11C-choline PET and PET/CT showed a sensitivity of 86.5% (32/37) and a specificity of 61.9% (13/21) in the detection of the primary malignancy. With regard to metastatic spread, PET showed a per-patient sensitivity of 81.8% (9/11) and produced no false positive findings. Based on our findings, differentiation between benign prostatic changes, such as benign prostatic hyperplasia or prostatitis, and prostate cancer is feasible in the majority of cases when image interpretation is primarily based on qualitative characteristics. SUVmax may serve as guidance. False positive findings may occur due to an overlap of 11C-choline uptake between benign and malignant processes. By providing functional information regarding both the primary malignancy and its metastases, 11C-choline PET may prove to be a useful method for staging prostate cancer. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate spiral multidetector computed tomography (MDCT) angiography using 64-slice technique in the detection of functionally relevant coronary artery stenoses (CAS). Thirty-eight patients (62±11 years, 28 men) with stable angina (26 with suspected and 12 with known coronary artery disease) were investigated using 64-slice MDCT angiography and gated myocardial perfusion SPECT (gated SPECT); a subgroup of 30 patients had additional invasive coronary angiography (ICA). Stenoses with luminal narrowing of ≥50% were defined as “significant” in MDCT angiography and ICA. MDCT angiography was compared with gated SPECT and the combination of gated SPECT plus ICA with respect to the detection of functionally relevant CAS. The sensitivity, specificity and negative and positive predictive values of MDCT angiography in detecting reversible perfusion defects on gated SPECT were 63%, 80%, 94% and 32%, respectively, in vessel-based analysis and 71%, 62%, 72% and 60%, respectively, in patient-based analysis. If only reversible perfusion defects on gated SPECT with CAS ≥50% on ICA were considered, the sensitivity, specificity and negative and positive predictive values were, respectively, 85%, 79%, 98% and 33% for vessel-based analysis and 85%, 59%, 83% and 61% for patient-based analysis. Sixty-four slice MDCT angiography failed to predict the functional relevance of CAS, but had a high negative predictive value in the exclusion of functionally relevant CAS in symptomatic patients. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the clinical benefit of combined [18F]FDG PET/CT in patients with malignant lymphoma as compared to separately performed PET and CT. Overall, 100 patients with Hodgkin’s disease (HD) or non-Hodgkin’s lymphoma (NHL) were included in this study. Co-registered PET/CT with [18F]FDG and contrast medium was performed in 50 consecutive patients with NHL ( n=38) or HD ( n=12) for initial staging (IS) ( n=12) or re-treatment staging (RS) ( n=38). Another 50 patients with NHL ( n=32) or HD ( n=18) underwent separate PET and CT investigations within a time frame of 10 days for IS ( n=22) or RS ( n=28). Lymphoma involvement was separately evaluated for seven different regions in each patient. Each patient had clinical follow-up evaluation for >6 months. PET and CT data were analysed separately as well as side-by-side or in fused mode. In the PET/CT group, region-based evaluation for lymphoma involvement suggested a sensitivity/specificity of 85%/91% for CT, 98%/99% for PET and 98%/99% for PET/CT. In the PET and CT group, region-based evaluation showed a sensitivity/specificity of 87%/80% for CT, 98%/99% for PET and 98%/100% for PET and CT read side by side. PET was superior to CT alone and was improved further by side-by-side reading of both examinations. However, no significant difference was observed between PET/CT and separate PET and CT imaging in patients with lymphoma. [ABSTRACT FROM AUTHOR]