Adult-onset Still disease: evaluation with serial f-18 fluorodeoxyglucose positron emission tomography.
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Adult↗
Biomedical subjects
Jan Versijpt
Publications and source records attributed to Jan Versijpt.
Experimental performance assessment of SPM for SPECT neuroactivation studies using a subresolution sandwich phantom design.
The validity domain of voxel-based statistical analysis of SPECT neuroactivation studies with statistical parametric mapping (SPM) has been investigated by a limited number of theoretical and simulation studies. In this work, an experimental setup is described with an assessment of its activation detection performance together with the influence of acquisition and processing parameters. A subresolution sandwich phantom was constructed using a printed high-resolution digital Hoffman phantom with a (99m)TcO(4)-ink mixture. Activations of 8, 16, and 24 mm diameter, with an intensity ranging from 5 to 60%, were constructed in the right frontal cortex, anterior and posterior cingulate, and left striatum. Triple-headed SPECT acquisitions were carried out using both fan-beam and parallel beam geometry. The impact of activation characteristics (size, intensity and location), study size, physical degradation factors, and reconstruction technique were studied using SPM99 in a group comparison design with correction for multiple comparisons. For a 15 x 15 design, all 24-mm activations of 5% intensity were detected for the fan-beam data. Decreased focus or study size, lower SPECT resolution, absence of scatter, and attenuation correction resulted in an increase in minimally detectable activation. For a single study referred to 15 control studies, only 24-mm activation foci with a minimal intensity of 10% were detected in the optimal configuration. This approach allows experimental parameter optimization of SPM-based group or single-subject SPECT activation studies compared to normal data, as used in clinical applications. In principle, these findings can be extended to SPECT receptor studies or PET data.
Algorithms↗
Analysis of clinical brain SPECT data based on anatomic standardization and reference to normal data: an ROC-based comparison of visual, semiquantitative, and voxel-based methods.
UNLABELLED: The technique of anatomic standardization and comparison with normal templates is increasingly used in clinical brain SPECT practice and allows automated, operator-independent volume-of-interest (VOI) or voxel-based analysis of whole-brain data. In 2 distinct clinical populations with severe traumatic brain injury and cognitive impairment, this study compared 3 widely available approaches that use normal templates to evaluate SPECT brain perfusion deficits. METHODS: In total, 74 subjects were studied. These included 14 patients with severe, traumatic brain injury (group 1; 10 males, 4 females; mean age +/- SD, 27.6 +/- 8.2 y) and 15 patients with cognitive impairment (group 2; 7 males, 8 females; mean age, 75.8 +/- 8.6 y). These data were compared with those from, respectively, 25 and 20 age- and sex-adjusted healthy volunteers. All data were analyzed in 4 ways. Three semiquantitative statistical algorithms were used: statistical parametric mapping (SPM) using SPM99, brain registration and analysis of SPECT studies (BRASS) using a voxelwise region-growing technique, and a predefined VOI approach. These results were compared with visual analysis based on consensus reading by 3 experienced nuclear medicine physicians. Receiver operating characteristic (ROC) analysis was performed at various statistical cutoffs. Moreover, as a measure of regional agreement, relative regional agreement between methods was assessed. RESULTS: In both study groups, BRASS voxel-based analysis was most accurate, as defined by the area under the ROC curve (0.97 for group 1 and 0.96 for group 2). VOI assessment was slightly more accurate than visual consensus analysis, whereas SPM showed, overall, a lower area under the ROC curve. SPM analysis was also significantly less sensitive at thresholds corresponding to low false-positive fractions. Regional analysis showed 83%-92% agreement between all methods. CONCLUSION: Under clinical conditions, classification of brain SPECT studies can greatly be aided by anatomic standardization techniques and reference to normal data. Under the investigated circumstances, SPM was found to have a lower sensitivity than VOI or voxelwise region-growing techniques, especially at low false-positive fractions.
Adolescent↗
Perfusion SPECT changes after acute and chronic vagus nerve stimulation in relation to prestimulus condition and long-term clinical efficacy.
UNLABELLED: Left-sided vagus nerve stimulation (VNS) is an efficacious treatment for patients with refractory epilepsy. Previous studies have implicated thalamic and mesial temporal involvement in acute stimulation. In this study, acute and chronic effects of VNS in patients with refractory complex partial seizures with or without secondary generalization (CPS +/- SG) were evaluated with respect to the prestimulus condition and long-term follow-up. METHODS: Twenty-three patients (12 females, 11 males; mean age, 32.4 +/- 10.6 y; mean CPS +/- SG duration, 21.0 +/- 11.7 y) were prospectively included. All patients were considered unsuitable candidates for resective surgery because of nonlocalizing findings in the presurgical evaluation. All underwent a split-dose (99m)Tc-ethyl cysteinate dimer activation study before and immediately after their initial stimulation (0.25 or 0.5 mA, 30 Hz) on a high-resolution triple-head gamma camera. Ten patients also underwent a SPECT activation study 5.7 +/- 1.6 mo after implantation with an additional 0.25-mA stimulus superposed on a therapeutic intensity of 1.5 +/- 0.3 mA. Data were analyzed by an automated semiquantitative volume-of-interest analysis after stereotactic anatomic standardization. RESULTS: In the acute, initial setting, the left thalamus, right parahippocampal gyrus, and right hippocampus were deactivated by VNS (P < 0.011). Acute stimulation in the chronic state resulted in a significant left thalamic activation (P < 0.001). When chronic perfusion was compared with the initial pre-VNS baseline, perfusion decreases were found in both thalami (-5.3% on the left and -3.4% on the right, P < or = 0.04). Perfusion changes in chronic VNS correlated negatively with the prestimulus perfusion pattern, indicating the tendency toward decreased brain activity on VNS. Initial stimulation changes in the right amygdala in the group of 10 patients with chronic assessment were predictive of therapeutic response (P = 0.018); in addition, right chronic hippocampal perfusion changes correlated strongly with the long-term clinical efficacy of VNS (P = 0.004). CONCLUSION: Under initial and chronic conditions, acute VNS stimulation produces different perfusion changes that are related to the interictal perfusion pattern before stimulation. The long-term mechanism of clinically effective VNS may rely on mainly hippocampal/amygdala and thalamic inhibition. Acute amygdala and chronic hippocampal perfusion changes are predictive of long-term therapeutic response in specific patient subgroups.
Adult↗
Semiquantification of the peripheral-type benzodiazepine ligand [11C]PK11195 in normal human brain and application in multiple sclerosis patients.
OBJECTIVES: [11C]PK11195 is a peripheral-benzodiazepine-receptor radioligand used for detection of microglial inflammation. Normal uptake by means of semiquantification was measured in order to establish reference data. The applicability of this semiquantitative approach was tested in three multiple sclerosis patients. MATERIALS AND METHODS: Seven controls and three patients underwent MR and PET scanning. Coregistered static scans 40 minutes postinjection of [11C]PK11195 were used for assessment of relative ligand uptake by comparison to whole-brain uptake. RESULTS: For static scans acquired in near steady-state, the relative ligand uptake was significantly higher in gray matter structures as compared to the whole brain (ratio: 1.041 +/- 0.06, p = 0.036) whereas it was comparable in white matter (1.010 +/- 0.035). Intersubject reproducibility was 11.4% and 12.9% for white and grey matter. Intrasubject reproducibility was of the same order: 14.0% and 14.5% respectively. In two clinically active patients with Gadolinium-positive T1-weighted lesions on MRI the focal ligand uptake was significantly increased (1.36 and 1.14, p = 0.001). In one clinically stable patient, the uptake value corresponding with a T2-weighted MR lesion was not different from normal brain measurements. CONCLUSION: The current investigations show that normal brain uptake of [11C]PK11195 is very low and shows the feasibility of a semiquantitative method which can be applied to larger cohorts of patients subgroups.
Adult↗