Background: Dementia with Lewy bodies (DLB) is a common form of late-life dementia that can be difficult to differentiate from other disorders, especially Alzheimer disease (AD), during life. At autopsy the striatal dopaminergic transporter is reduced. Objectives: To examine the extent and pattern of dopamine transporter loss using iodine I 123-radiolabeled 2  -c a r b o m e t h o x y -3  -( 4 -i o d o p h e n y l ) -N -( 3fluoropropyl) nortropane (FP-CIT) with single-photon emission computed tomography (SPECT) in DLBs compared with other dementias and to assess its potential to enhance a differential diagnosis. Design: Cohort study comparing FP-CIT with criterion standard of consensus clinical diagnosis. Setting: General hospital. Participants: One hundred sixty-four older subjects (33 healthy older control subjects, 34 with NINCDS/ADRDA [National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association]-confirmed AD, 23 with consensus guideline-confirmed DLB, 38 with United Kingdom's Parkinson Disease Society Brain Bank-confirmed Parkinson disease [PD], and 36 with PD and dementia).Interventions: Injection of 123 I-2-carbomethoxy-3-(4-iodophenyl)-N-(3-fluoropropyl) nortropane with SPECT scan performed at 4 hours. Main Outcome Measures: Visual ratings of scans and region of interest analysis.Results: Significant reductions (PϽ.001) in FP-CIT binding occurred in the caudate and anterior and posterior putamens in subjects with DLB compared with subjects with AD and controls. Transporter loss in DLBs was of similar magnitude to that seen in PD, but with a flatter rostrocaudal (caudate-putamen) gradient (P=.001), while the greatest loss in all 3 areas was seen in those who had PD and dementia. Both region of interest analysis and visual ratings provided good separation between DLBs and AD (region of interest: sensitivity, 78%; specificity, 94%; positive predictive value, 90%) but not among subjects with DLB, PD, and PD with dementia.Conclusions: Dopamine transporter loss can be detected in vivo using FP-CIT SPECT in DLB. Further studies, especially of subjects with DLB without PD, are required to fully establish use in clinical practice.
The signal to noise ratio (SNR) is one of the important measures of the performance of a magnetic resonance imaging (MRI) system. The object of this study was to compare a single acquisition method, which estimates the noise from background pixels, with a dual acquisition method which estimates the noise from the subtraction of two sequentially acquired images. The dual acquisition method is more exact, but is slower to perform and requires image manipulation. A comparison between the two methods gave a good correlation, and a regression equation of SNRsingle = 1.1 + 0.94 SNRdual. The single acquisition method is therefore appropriate for use in a quality assurance programme, since it is quicker and simpler to perform and is a good indicator of the more exact measure.
The authors determined rates of brain atrophy, as assessed by the boundary shift integral on serial MRI, in patients with dementia with Lewy Bodies (DLB, n = 10), AD (n = 9), vascular dementia (VaD, n = 9), and age-matched controls (n = 20). Mean % +/- SD atrophy rates per year were as follows: DLB, 1.4 +/- 1.1; AD, 2.0 +/- 0.9; VaD, 1.9 +/- 1.1; and controls, 0.5 +/- 0.7. Dementia subjects had higher rates than controls (p < 0.001), but there were no significant differences between the three dementia groups. The authors found accelerating atrophy with increasing severity of cognitive impairment, further emphasizing the need for early diagnosis and intervention in dementia.
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