European Journal of Nuclear Medicine Vol. 29, No. 12, December 2002 Abstract. The diagnosis of Parkinson’s disease is based on clinical features with pathological verification. How- ever, autopsy has been found to confirm a specialist di- agnosis in only about 75% of cases. Especially early in the course of the disease, the clinical diagnosis can be difficult. Imaging of presynaptic dopamine transporters (DAT receptors) has provided a possible diagnostic probe in the evaluation of Parkinson’s disease. The co- caine analogue [ 123 I]-2-β-carboxymethoxy-3-β(4-iodo- phenyl)tropane ([ 123 I]-β-CIT) is one of several radioli- gands that have been developed for single-photon emis- sion tomography (SPET). The purpose of this study was to evaluate the impact of [ 123 I]-β-CIT SPET on the diag- nosis and clinical management of patients with a prima- ry, tentative diagnosis of parkinsonism. We undertook a retrospective evaluation of the clinical records of 90 con- secutive patients referred to [ 123 I]-β-CIT SPET from the neurological department, Bispebjerg Hospital. In 58 sub- jects the scans revealed altered tracer uptake consistent with Parkinson’s disease, progressive supranuclear palsy and multiple system atrophy. A significant change in the management or treatment because of the scan was found in 25 patients (28%). The sensitivity of the examination was 97% and the specificity 83%. In conclusion, a sig- nificant clinical impact of DAT receptor SPET imaging was found. DAT receptor imaging is a useful diagnostic probe in patients with a possible diagnosis of parkinson- ism. Keywords: Single-photon emission tomography – Dopa- mine transporter – Parkinson’s disease – Differential di- agnosis Eur J Nucl Med (2002) 29:1623–1629 DOI 10.1007/s00259-002-0938-7 Introduction Parkinson’s disease (PD) is a neurodegenerative progres- sive disease. The age of onset is usually between 50 and 79 years, and the prevalence in the age group over 65 years is about 1.6% [1]. The diagnosis of idiopathic PD is based on clinical findings. A definite diagnosis is pro- vided by neuropathological microscopy showing neuro- nal cell loss in substantia nigra and Lewy bodies in some of the remaining neurones. A patient with the clinical features of parkinsonism (i.e. rigidity, bradykinesia and tremor) that respond well to dopaminergic medication has a probable clinical diag- nosis of PD [2]. Parkinsonism, however, can also be found in a number of other diseases, e.g. “parkinsonism plus” [(multiple system atrophy (MSA), corticobasal de- generation (CBD) and progressive supranuclear palsy (PSP)], and essential tremor. Secondary parkinsonism can be induced by vascular events, hydrocephalus, drugs, infection, trauma or toxins [3]. Clinically it can be difficult to distinguish between these different forms of parkinsonism [4]. Some clinico- pathological studies have shown that autopsy confirms a specialist diagnosis in only 76% of cases [5, 6]. A cor- rect clinical diagnosis, however, is important for ade- quate treatment and prognosis. Especially the emergence of possible neuroprotective drugs [7] has prompted a search for early markers of PD [8]. Imaging of presynaptic dopamine transporters (DAT receptors) has provided a possible diagnostic probe in the evaluation of PD. The cocaine analogue [ 123 I]-2-β- carboxymethoxy-3β(4-iodophenyl)tropane ([ 123 I]-β-CIT) is one of several radioligands that have been developed for single-photon emission tomography (SPET). [ 123 I]-β- CIT has been shown to have high affinity for DAT recep- tors in the striatum [9]. A number of studies have shown a correlation between [ 123 I]-β-CIT uptake in the striatum and symptom severity (UPDRS, H&Y) [10, 11] and age [12]. Studies of hemiparkinsonian patients [13] have shown possible pre-symptomatic changes, in accordance with the 50%–80% loss of nigral neurones preceding Annemette Løkkegaard ( ✉ ) Department of Neurology, Bispebjerg Hospital, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark e-mail: alokkegaard@hotmail.com Tel.: +45-35-313573 Original article Clinical impact of diagnostic SPET investigations with a dopamine re-uptake ligand Annemette Løkkegaard 1, 2 , Lene M. Werdelin 1 , Lars Friberg 2 1 Department of Neurology, Bispebjerg Hospital, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark 2 Department of Clinical Physiology and Nuclear Medicine, Bispebjerg Hospital, Copenhagen, Denmark Received: 8 April 2002 / Accepted: 27 June 2002 / Published online: 13 September 2002 © Springer-Verlag 2002