European Journal of Nuclear Medicine and Molecular Imaging Vol. 32, No. 4, April 2005 Abstract. Purpose. The β-adrenoceptor (β-AR) plays an important role in heart failure. Recently, the new tracer (S)-[ 11 C]CGP12388 has been developed. It displays ex- cellent properties for investigation of the cardiac β-ARs in vivo with positron emission tomography (PET). Fur- thermore, the simple production method allows its use in a routine clinical setting. The aim of this study was to in- vestigate whether decreased myocardial β-AR density in patients with idiopathic dilated cardiomyopathy (IDC) can be estimated using (S)-[ 11 C]CGP12388 PET. Methods. Myocardial β-AR density was investigated in six patients with IDC and six age-matched healthy con- trols, using (S)-[ 11 C]CGP12388 PET. Results. β-AR densities of 5.4±1.3 pmol/g (mean ± SD) were observed in patients; these values were significant- ly lower than those observed in healthy controls (8.4±1.5 pmol/g, p<0.005). Conclusion. This study indicates that PET with (S)- [ 11 C]CGP12388 is applicable for the measurement of myocardial β-AR density in patients. A highly signifi- cant reduction in β-AR density was found in patients with IDC compared with healthy controls. Keywords: Imaging – Beta-adrenergic receptors – Heart failure Eur J Nucl Med Mol Imaging (2005) 32:443–447 DOI 10.1007/s00259-004-1701-z Introduction The β-adrenoceptor (β-AR) plays an important role in heart failure and has been extensively studied in recent decades [1]. In vitro studies have shown downregulation of β-AR density in heart failure [2]. β-AR density is a direct reflection of contractility in the heart, and a decreased contractility is one of the hallmarks of heart failure. However, measurement of β-AR has until now been possible only through endomyocardial biopsy. This technique is invasive and is therefore accompanied by a certain incidence of complications, such as myocardial perforation. As a result, large-scale use of this technique and repeated sampling to provide longitudinal and re- gional assessment of myocardial β-ARs in humans are impossible. Therefore non-invasive methods would be useful to measure β-ARs in vivo. Positron emission tomography (PET) is an excellent non-invasive tool to investigate the regional distribution of myocardial β-ARs in vivo [3] and provides the possi- bility of performing repeated measurements [4]. Studies using PET and (S)-[ 11 C]CGP12177 have shown promis- ing results in agreement with those of in vitro studies [5]. (S)-[ 11 C]CGP12177 is produced from [ 11 C]phosgene and a (S)-diamine precursor. Several PET centres have re- ported high radiochemical yields, but unfortunately vari- able and usually very low specific activities. This trou- blesome and laborious radiolabelling via [ 11 C]phosgene is an important drawback to the application of (S)- [ 11 C]CGP12177 in clinical studies on a routine basis and prevents widespread use of this radioligand. As a potentially useful alternative, the radioligand (S)-[ 11 C]CGP12388 was developed in our institution for clinical PET [6–9]. In contrast to (S)-[ 11 C]CGP12177, (S)-[ 11 C]CGP12388 can easily be prepared from [ 11 C]ac- etone and the corresponding (S)-desisopropyl precursor, but it has comparable in vitro characteristics [8]. In rats, Philip H. Elsinga ( ✉ ) PET-center, Groningen University Hospital, P.O. Box 30001, 9700 RB Groningen, The Netherlands e-mail: p.h.elsinga@pet.azg.nl Tel.: +31-50-3613247, Fax: +31-50-3611687 Original article Myocardial β-adrenoceptor downregulation in idiopathic dilated cardiomyopathy measured in vivo with PET using the new radioligand (S)-[ 11 C]CGP12388 Richard M. de Jong 1 , Antoon T. M. Willemsen 2 , Riemer H. J. A. Slart 2 , Paul K. Blanksma 1 , Aren van Waarde 2 , Jan Hein Cornel 3 , Willem Vaalburg 2 , Dirk J. van Veldhuisen 1 , Philip H. Elsinga 2 1 Deparment of Cardiology, Groningen University Hospital, Groningen, The Netherlands 2 PET-center, Groningen University Hospital, RB Groningen, The Netherlands 3 Medical Center Alkmaar, The Netherlands Received: 6 July 2004 / Accepted: 9 September 2004 / Published online: 11 December 2004 © Springer-Verlag 2004