This first-in-human study investigated the safety, tolerability, metabolism, pharmacokinetics, biodistribution, and radiation dosimetry of 68 Ga-bombesin antagonist 68 Ga-DOTA-4-amino-1-carboxymethylpiperidine-D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 . Methods: Five healthy men underwent dynamic whole-body PET/CT after an intravenous injection of BAY 86-7548 (138 6 5 MBq). Besides total radioactivity, plasma samples were analyzed by radio-high-performance liquid chromatography for metabolism of the tracer. Dosimetry was calculated using the OLINDA/EXM software. Results: Three radioactive plasma metabolites were detected. The proportion of unchanged BAY 86-7548 decreased from 92% 6 9% at 1 min after injection to 19% 6 2% at 65 min. The organs with the highest absorbed doses were the urinary bladder wall (0.62 mSv/MBq) and the pancreas (0.51 mSv/MBq). The mean effective dose was 0.051 mSv/MBq. BAY 86-7548 was well tolerated by all subjects. Conclusion: Intravenously injected BAY 86-7548 is safe, and rapid metabolism is demonstrated. A 150-MBq injection of BAY 86-7548 results in an effective dose of 7.7 mSv, which could be reduced to 5.7 mSv with frequent bladder voids.Key Words: dosimetry; 68 Ga; PET; pharmacokinetics; radiometabolism; whole-body distribution J Nucl Med 2013; 54:867-872 DOI: 10.2967/jnumed.112.114082 Prost ate cancer (PCa) is the second most common cancer in men globally (1) and the most common cancer in developed countries (2). However, conventional imaging techniques such as ultrasound, contrast-enhanced CT, or MR imaging have limited sensitivity and specificity for detecting primary, metastatic, and recurrent PCa (3). PET/CT plays an important role in the attempt to improve and individualize therapeutic approaches in oncology. The most widely used tracer, 18 F-FDG, shows a high excretion in the urinary bladder and demonstrates generally an unsatisfactory uptake in PCa, especially in the early phase (4,5). Tracers that depict lipid metabolism such as 11 C-choline and 11 C-acetate have already been applied for imaging PCa, but they accumulate also in prostatic hyperplasia, with overlapping uptake in benign and malignant intraprostatic lesions (6-8). Consequently, there is an urgent need for more PCa-specific tracers.Gastrin-releasing peptide receptors (GRPr) are highly overexpressed in a variety of human tumors including PCa (9). Preclinical data suggest the possibility of a high PCa-specific signal with radiolabeled bombesin analogs targeting GRPr (10). These analogs could potentially provide better and more specific diagnosis than 18 F-FDG or tracers such as 11 C-choline or 11 C-acetate.68 Ga-DOTA-4-amino-1-carboxymethylpiperidine-D-PheGln-Trp-Ala-Val-Gly-His-Sta-Leu-NH 2 (BAY 86-7548; also known as RM2) is a bombesin antagonist with high GRPr affinity. The purpose of this first-in-human study was to investigate the safety, tolerability, metabolism, pharmacokinetics, biodistribution, and radiation dosimetry of BAY 86-7548 in healthy volunteers receiving an intravenous injection of this a...

According to the comparison, using pCT for clinical EBRT planning and dose calculation in the three investigated types of pelvic cancers is feasible. Further studies are required to demonstrate the applicability to a larger cohort of patients.

Background and purpose: The clinical feasibility of synthetic computed tomography (sCT) images derived from magnetic resonance imaging (MRI) images for external beam radiation therapy (EBRT) planning have been studied and adopted into clinical use recently. This paper evaluates the dosimetric and positioning performance of a sCT approach for different pelvic cancers. Materials and methods: Seventy-five patients receiving EBRT at Turku University Hospital (Turku, Finland) were enrolled in the study. The sCT images were generated as part of a clinical MRI-simulation procedure. Dose calculation accuracy was assessed by comparing the sCT-based calculation with a CT-based calculation. In addition, we evaluated the patient position verification accuracy for both digitally reconstructed radiograph (DRR) and cone beam computed tomography (CBCT)-based image guidance using a subset of the cohort. Furthermore, the relevance of using continuous Hounsfield unit values was assessed. Results: The mean (standard deviation) relative dose difference in the planning target volume mean dose computed over various cancer groups was less than 0.2 (0.4)% between sCT and CT. Among all groups, the average minimum gamma-index pass-rates were better than 95% with a 2%/2mm gamma-criteria. The difference between sCT-and CT-DRR-based patient positioning was less than 0.3 (1.4) mm in all directions. The registrations of sCT to CBCT produced similar results as compared with CT to CBCT registrations. Conclusions: The use of sCT for clinical EBRT dose calculation and patient positioning in the investigated types of pelvic cancers was dosimetrically and geometrically accurate for clinical use.