unselected population. Consequently the remaining 56% of patients had either other forms of dementia (AD, FTD, VaD) or represented the ‘worried well’. Occipital hypoperfusion was demonstrated in 28% (11/39) of patients with DLB and in 31% (14/45) of non-DLB cases. Conclusion Occipital hypoperfusion on HMPAO SPECT is only demonstrated in a minority of patients with DLB. Furthermore, occipital hypoperfusion is equally likely in patients with DLB as opposed to all other dementias. It is important for reporting clinicians to be aware that the appearances of the occipital lobe on HMPAO SPECT imaging may not be sufficiently reliable to either rule in, or rule out, a diagnosis of DLB. A DaTSCAN is essential. 7 DaTSCANt in clinical practice: qualitative or quantitative analysis? K.E. Gannon 1 , J. Deeb 2 , R. Gunasekera 1 and C.H. Hawkes 2 1 Nuclear Medicine Department, 2 Essex Neuroscience Centre, Queen’s Hospital, Romford, Essex, UK. Introduction Essential Tremor (ET) is commonly misdiagnosed as Parkinson’s disease (PD), particularly at early stages. DaTSCANt ( 123 I-FP-CIT) SPECT imaging provides a useful diagnostic tool for assessing patients with suspected PD. Uptake of activity is usually normal in ET patients and reduced in PD patients. Methods 22 ET and 35 PD patients were recruited from neurology clinics along with 15 healthy controls. All patients underwent DaTSCANt tomography using a Siemens E.CAM gamma camera at Oldchurch Hospital. Images were assessed visually by the same nuclear medicine consultant. They were also assessed quantita- tively by a single operator using QuantiSPECT software. Both the 2-Box and crescent ROI techniques were employed, and all ET and PD patients were compared to a normal range generated from the healthy controls. All results, both visual and quantitative were compared to the final clinical diagnosis (FCD). Results Table U2 Whole Striatum 2-Box Whole Striatum Crescent FCD vs. Visual All Agree FCD vs. QuantiSPECT All Agree FCD vs QuantiSPECT ET 86% 73% 82% 82% 95% PD 97% 80% 83% 69% 71% Conclusion Visual analysis is consistent with FCD in 97% of cases. Quantitative analysis reveals a high specificity using the crescent ROI method. It is possible that ET patients with abnormal scans are at a higher risk of developing Parkinson’s disease. Further clinical follow up is required. 8 Factor analysis of rCBF SPECT images to mimic experienced observer R. Peare and R.T. Staff Department of Nuclear Medicine, Aberdeen Royal Infirmary, Aberdeen, UK. Purpose To investigate whether the use of principal component analysis of rCBF SPECT images can model experienced observer interpretation. Method SPECT images from 227 patients were used in this analysis. The images were categorised by an experienced observer as normal (35), Alzheimer’s disease (AD) (113), vascular (30), mixed (45) or frontal disease (4). The SPECT images were spatially normalised to the SPM SPECT template. Regions of interest were generated using WFU PickAtlas 2.0. All regions were normalised to the cerebellum. Principal component analysis was performed using SPSS. Predictive models were created using Z scores and a centroid technique. Results The model was able to distinguish normal from not normal with a sensitivity of 83% and a specificity of 84%. It distinguished AD from other forms of dementia with a sensitivity of 65% and a specificity of 71%. It differentiated between vascular and mixed disease with a sensitivity of 83% and a specificity of 80%. Conclusion This method has the potential to be a useful tool in analysing clinical rCBF SPECT images. In particular, principal component factors could be used to curate images and allow appropriate database interroga- tion: (‘I have an image show me a similar image’). 9 Evaluation of 1808 acquisition for DaTSCAN using a brain phantom J. O’Brien 1 , E. Clarke 2 , W.H. Thomson 1 and A. Notghi 1 1 City Hospital Birmingham, and 2 GE Healthcare Medical Diagnostics, Birmingham, UK. Purpose Recommended acquisition for DaTSCAN is a circular (E13 cm radius) 3601 SPECT acquisition. This can be difficult in patients with claustrophobia or severe tremor. The vertex view has been used, but result can be inconclusive [1]. We evaluated the feasibility of 1801 acquisition for such patients. Methods We used a DaTSCAN phantom (courtesy of GE Healthcare). Standard images were acquired over 3601 in 30 min with a dual-headed Philips Axis camera. 1801 images were acquired with the same acquisition time in three ways: using two heads configured at 901 and also at 1021, and with single head only (other head moved far out). These open configurations are acceptable for claustrophobic patients. Results Comparison was made with 3601 images. Some distortion occurred in all 1801 images. Due to camera head limitations, 901 gave a poor orbit radius (18.3 cm) compared with 1021 and single head (15.1cm and 12.1 cm). Resolution was therefore degraded which BNMS Oral and Poster Abstracts 2007 A3 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.