Objective. 18 F-fluorodeoxyglucose-positron emission tomography (FDG-PET) scanning has been proposed as a new way of assessing disease activity in Takayasu arteritis (TA), but previous studies have used the nonvalidated National Institutes of Health (NIH) global activity criteria, and thus might be biased. This study was undertaken to determine the value of PET scanning for assessment of disease activity in TA, by comparing PET scan data with clinical, biologic, and magnetic resonance imaging (MRI) data assessed separately.Methods. Twenty-eight patients with TA (according to the American College of Rheumatology criteria) underwent a total of 40 PET scans. Images were reviewed by 2 pairs of independent nuclear medicine physicians and assessed for pattern and intensity of vascular uptake. TA activity data were obtained within 15 days of the PET scans.Results. PET scanning revealed abnormal vascular uptake in 47% of the 40 examinations. The uptake intensity grade was 0 in 7 scans, grade 1 in 7 scans, grade 2 in 13 scans, and grade 3 in 13 scans. Morphologic analysis was conducted by grading the pattern of the vascular uptake as diffuse (73%), segmental (20%), or focal (13%). There was a trend toward an association between clinically active disease and the semiquantitative assessment of FDG uptake (P ‫؍‬ 0.08). We found no statistical association between levels of acute-phase reactants and intensity of uptake. There was no significant association between the semiquantitative assessment of FDG uptake and the presence of vascular wall thickening (P ‫؍‬ 0.23), gadolinium uptake (P ‫؍‬ 0.73), or the presence of vascular wall edema (P ‫؍‬ 0.56).Conclusion. Our findings indicate that there is no association between FDG vascular uptake intensity and clinical, biologic, or MRI assessment of disease activity. Previous studies using the nonvalidated NIH global activity criteria are likely biased.

Objective. Erdheim-Chester disease (ECD) is a rare form of non-Langerhans' cell histiocytosis. The aim of this study was to assess the value of whole-body scanning with 18 F-fluorodeoxyglucose-positron emission tomography (FDG-PET) in a large cohort of ECD patients from a single center.Methods. We retrospectively reviewed all PET scans performed on 31 patients with ECD who were referred to our department between 2005 and 2008. PET images were reviewed by 2 independent nuclear medicine specialist physicians and were compared with other imaging modalities performed within 15 days of each PET scan.Results. Thirty-one patients (10 women and 21 men; median age 59.5 years) underwent a total of 65 PET scans. Twenty-three patients (74%) were untreated at the time of the initial PET scan, whereas 30 of the 34 followup PET scans (88%) were performed in patients who were undergoing immunomodulatory therapy. Comparison of the initial and followup PET scans with other imaging modalities revealed that the sensitivity of PET scanning varied greatly among the different organs studied (range 4.3-100%), while the specificity remained high (range 69.2-100%). Followup PET scans were particularly helpful in assessing central nervous system (CNS) involvement, since the PET scan was able to detect an early therapeutic response of CNS lesions, even before magnetic resonance imaging showed a decrease in their size. PET scanning was also very helpful in evaluating the cardiovascular system, which is a major prognostic factor in ECD, by assessing the heart and the entire vascular tree during a single session.Conclusion. The results of our large, singlecenter, retrospective study suggest that the findings of a FDG-PET scan may be interesting in the initial assessment of patients with ECD, but its greater contribution is in followup of these patients.

(PD). Quantification of 123 I-FP-CIT images is performed at equilibrium using a ratio (BR) of specific (striatal) to nonspecific (occipital) uptake with values obtained from regions of interest drawn manually over these structures. Statistical parametric mapping (SPM) is a fully automated voxel-based statistical approach that has great potential in the context of DAT imaging. However, the accuracy of the spatial normalization provided by SPM has not been validated for 123 I-FP-CIT images. Our first aim was to create an 123 I-FP-CIT template that does not require the acquisition of patient-specific MRI and to validate the spatial normalization procedure. Next, we hypothesized that this customized template could be used by different SPECT centers without affecting the outcomes of imaging analyses. Methods: The spatial normalization to the customized template created with SPM (template A1) was validated using 123 I-FP-CIT images obtained from 6 subjects with essential tremor (ET) with normal DAT status and 6 PD patients. Variability in BR values due to the normalization was evaluated using striatal volume of interest (VOI). To determine whether different SPECT centers could use a unique 123 I-FP-CIT template, we generated 3 other 123 I-FP-CIT templates using different subjects and image-processing schemes. The interchangeability of these templates was assessed using (a) putamen BR values analyzed with the intraclass correlation coefficient (ICC) and the Bland-Altman graphical analysis, and (b) SPM analysis comparing the results of group comparisons-that is, ET versus PD, obtained after normalization to each of the 4 templates. Results: There was no significant difference between pre-and postnormalization striatal BR values in our study. The mean variability calculated with putamen VOI values after normalization to each template was ,10%, with the lowest ICC of 98%. Intergroup analyses performed with VOI and SPM approaches provided similar results independently of the template used. Conclusion: SPM normalization was accurate even in subjects with low striatal 123 I-FP-CIT uptake, making it a promising approach for automatic analysis of 123 I-FP-CIT images using a single customized template at different centers. Parki nson's disease (PD) is characterized by the progressive degeneration of nigrostriatal dopaminergic neurons. This neurodegenerative process is associated with a loss of striatal dopamine transporters (DATs) as shown by postmortem studies (1,2). Therefore, in vivo measurement of DAT density with PET or SPECT is an early marker of the dopaminergic cell loss in subjects with parkinsonian symptoms or in asymptomatic carriers of genetic mutations causing PD (3-7). In clinical routine, DAT SPECT images are often analyzed visually. However, quantitative analysis is useful to differentiate subjects with subtle localized or diffuse loss of DATs that can be difficult to sort out by visual inspection alone. Moreover, quantification is mandatory to measure disease progression (7-11) and to assess the efficacy of ne...

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