European Journal of Nuclear Medicine and Molecular Imaging Vol. 30, No. 8, August 2003 Abstract. The aim of this study was to describe the ana- tomical structures that show uptake of the somatostatin analogue octreotide in patients with thyroid-associated orbitopathy (TAO). The study population comprised a series of 20 TAO patients attending the out-patient thy- roid clinic and 12 patients presenting head or neck tu- mours. Scintigraphy was carried out with our newly de- veloped tracer, technetium-99m labelled EDDA-HY- NIC-TOC ( 99m Tc-TOC). Morphological imaging was done with either magnetic resonance imaging or X-ray computed tomography without contrast medium. Both imaging procedures were done within an interval of 3–4 weeks. For the image fusion procedure, specific external reference markers were used for each imaging modality. The markers were screwed onto a reference frame, which was held in place via a vacuum-fixed mouthpiece. The anatomical structure showing tracer uptake that was most frequently recognised was the lacrimal gland, fol- lowed by the retronasal area, cervical lymph structures, salivary glands, the anterior insertion points of the extra- ocular muscles and discrete areas of the neck extensor muscles. The lacrimal gland and the retronasal area showed the highest and most frequent uptake of 99m Tc- TOC in TAO patients, whereas such uptake did not occur in the retrobulbar space. In spite of knowledge of these results of image fusion, no changes in the involved struc- tures could be detected on morphological imaging. It is concluded that binding of 99m Tc-TOC is more frequently localised to the anterior compartment of the eye and to the neck. The previously used term “orbital” uptake should be abandoned and replaced by a descriptive term relating to the anatomically recognised structure showing tracer accumulation, i.e. the lacrimal gland. The uptake of octreotide by lymphoid and salivary glands opens a new field of investigation related to the physiology of somatostatin. Keywords: Octreotide – 99m Tc-EDDA-HYNIC-TOC – Thyroid-associated ophthalmopathy – Image fusion – Lacrimal gland Eur J Nucl Med Mol Imaging (2003) 30:1155–1159 DOI 10.1007/s00259-003-1207-0 Introduction Thyroid-associated ophthalmopathy (TAO) has been re- cognised as a clinical entity for more than 150 years [1]. The basic clinical picture of TAO has not changed since these initial descriptions. Morphological imaging tech- niques, e.g. computed tomography (CT) and magnetic resonance imaging (MRI), can document involvement of the extra-ocular muscles as well as anterior displacement of the lacrimal gland [2, 3]. Functional imaging methods using octreotide have suggested the involvement of im- munological mechanisms in the orbital region. Tracer uptake has been shown to be amenable to modulation by immunosuppressive therapy. In addition, probable in- volvement of the lacrimal gland has been described [4]. In spite of these results, several recent reviews have pointed out the need for further investigation into the pathophysiology of this disease [5]. Recent technical de- velopments have paved the way for a new analysis of this situation. The first improvement was the develop- ment of a technetium-99m labelled octreotide tracer [6]. The second improvement was the development of a The individual results of the first 18 patients with thyroid-associat- ed orbitopathy have been analysed as part of a doctoral thesis (H. Kainz, University of Innsbruck, 2002). Roy Moncayo ( ✉ ) Department of Nuclear Medicine, University Clinic, University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria e-mail: Roy.Moncayo@uibk.ac.at Short communication Image fusion analysis of 99m Tc-HYNIC-octreotide scintigraphy and CT/MRI in patients with thyroid-associated orbitopathy: the importance of the lacrimal gland Hartmann Kainz 1 , Reto Bale 2 , Eveline Donnemiller 1 , Michael Gabriel 1 , Peter Kovacs 2 , Clemens Decristoforo 1 , Roy Moncayo 1 1 Department of Nuclear Medicine, University Clinic, University of Innsbruck, Innsbruck, Austria 2 Department of Radiology I, University Clinic, University of Innsbruck, Austria Received: 18 February 2003 / Accepted: 28 March 2003 / Published online: 13 June 2003 © Springer-Verlag 2003