Antoine Verger

Compared Performance of High-Sensitivity Cameras Dedicated to Myocardial Perfusion SPECT: A Comprehensive Analysis of Phantom and Human Images

Differences in the performance of cadmium-zinc-telluride (CZT) cameras or collimation systems that have recently been commercialized for myocardial SPECT remain unclear. In the present study, the performance of 3 of these systems was compared by a comprehensive analysis of phantom and human SPECT images. Methods: We evaluated the Discovery NM 530c and DSPECT CZT cameras, as well as the Symbia Anger camera equipped with an astigmatic (IQ⋅SPECT) or parallel-hole (conventional SPECT) collimator. Physical performance was compared on reconstructed SPECT images from a phantom and from comparable groups of healthy subjects. Results: Classifications were as follows, in order of performance. For count sensitivity on cardiac phantom images (counts⋅s−1⋅MBq−1), DSPECT had a sensitivity of 850; Discovery NM 530c, 460; IQ⋅SPECT, 390; and conventional SPECT, 130. This classification was similar to that of myocardial counts normalized to injected activities from human images (respective mean values, in counts⋅s−1⋅MBq−1: 11.4 ± 2.6, 5.6 ± 1.4, 2.7 ± 0.7, and 0.6 ± 0.1). For central spatial resolution: Discovery NM 530c was 6.7 mm; DSPECT, 8.6 mm; IQ⋅SPECT, 15.0 mm; and conventional SPECT, 15.3 mm, also in accordance with the analysis of the sharpness of myocardial contours on human images (in cm−1: 1.02 ± 0.17, 0.92 ± 0.11, 0.64 ± 0.12, and 0.65 ± 0.06, respectively). For contrast-to-noise ratio on the phantom: Discovery NM 530c had a ratio of 4.6; DSPECT, 4.1; IQ⋅SPECT, 3.9; and conventional SPECT, 3.5, similar to ratios documented on human images (5.2 ± 1.0, 4.5 ± 0.5, 3.9 ± 0.6, and 3.4 ± 0.3, respectively). Conclusion: The performance of CZT cameras is dramatically higher than that of Anger cameras, even for human SPECT images. However, CZT cameras differ in that spatial resolution and contrast-to-noise ratio are better with the Discovery NM 530c, whereas count sensitivity is markedly higher with the DSPECT.

Comparison between stress myocardial perfusion SPECT recorded with cadmium-zinc-telluride and Anger cameras in various study protocols

PurposeThe results of stress myocardial perfusion SPECT could be enhanced by new cadmium-zinc-telluride (CZT) cameras, although differences compared to the results with conventional Anger cameras remain poorly known for most study protocols. This study was aimed at comparing the results of CZT and Anger SPECT according to various study protocols while taking into account the influence of obesity.MethodsThe study population, which was from three different institutions equipped with identical CZT cameras, comprised 276 patients referred for study using protocols involving 201Tl (nu2009=u2009120) or 99mTc-sestamibi injected at low dose at stress (99mTc-Low; stress/rest 1-day protocol; nu2009=u2009110) or at high dose at stress (99mTc-High; rest/stress 1-day or 2-day protocol; nu2009=u200946). Each Anger SPECT scan was followed by a high-speed CZT SPECT scan (2 to 4xa0min).ResultsAgreement rates between CZT and Anger SPECT were good irrespective of the study protocol (for abnormal SPECT, 201Tl 92xa0%, 99mTc-Low 86xa0%, 99mTc-High 98xa0%), although quality scores were much higher for CZT SPECT with all study protocols. Overall correlations were high for the extent of myocardial infarction (ru2009=u20090.80) and a little lower for ischaemic areas (ru2009=u20090.72), the latter being larger on Anger SPECT (pu2009<u20090.001). This larger extent was mainly observed in 50 obese patients who were in the 201Tl or 99mTc-Low group and in whom stress myocardial counts were particularly low with Anger SPECT (228u2009±u2009101 kcounts) and dramatically enhanced with CZT SPECT (+279u2009±u2009251xa0%).ConclusionConcordance between the results of CZT and Anger SPECT is good regardless of study protocol and especially when excluding obese patients who have low-count Anger SPECT and for whom myocardial counts are dramatically enhanced on CZT SPECT.

Correlation of SUV-Derived Indices With Tumoral Aggressiveness of Gliomas in Static 18F-FDOPA PET: Use in Clinical Practice.

Purpose Glioma grading is necessary for prognostic evaluation and optimal treatment decisions. The aims of this study were to establish whether a correlation between 18F-FDOPA uptake with tumor grade was observed and to determine which of the SUV-derived indices was the best correlated. Patients and Methods Thirty-one patients were retrospectively included (mean [SD] age, 36.8 [12.1] years) including 21 proven low-grade tumors due to histology, imaging, and clinical follow-up and 10 histologically proven high-grade tumors. Static PET acquisitions were postreconstructed between the 10th and 30th minute after injection of 18F-FDOPA. Regions of interest of 20 mm were applied to tumors, and isocontoured volumes were defined at levels of 50% and 80% of the peak intensity voxel. Background was quantified with 30-mm-diameter regions of interest on contralateral striatum and centrum semioval. Tumoral uptake was evaluated with the following SUV-derived indices: SUVmax, SUVmean, SUVmax, and SUVmean of isocontoured volume, tumor/striatum ratio (T/S), and tumor/normal brain ratio (T/N). Results All the SUV-derived indices tested were significantly correlated with tumor grade, considering low-grade and high-grade groups (P < 0.05), except for the SUVmean 50%. The 2 best-correlated indices were SUVmean T/N and SUVmean T/S, with correlation coefficients of 0.561 and 0.522, respectively. Receiver operating characteristic analysis defined optimal thresholds of 1.33 and 1 for sensitivity and specificity of 71% and 100% and 67% and 100%, respectively. Conclusions 18F-FDOPA PET SUV-derived indices are routinely available information that enables accurate discrimination of low-grade and high-grade gliomas. The best-correlated indices were SUVmean T/N and SUVmean T/S with thresholds of 1.33 and 1.

Evidence of Cyclic Changes in the Metabolism of Abdominal Aortic Aneurysms During Growth Phases: 18F-FDG PET Sequential Observational Study

The rates of growth of medically treated abdominal aortic aneurysms (AAA) are difficult to determine, and relationships with parietal inflammation and with metabolic parameters from 18F-FDG PET remain unclear. This 18F-FDG PET sequential observational study was aimed at analyzing the metabolic changes accompanying the growth phases of medically treated AAA. Methods: Thirty-nine patients (37 men; age [mean ± SD], 71 ± 12 y) exhibiting small and medically treated AAA (maximal diameter, 46 ± 3 mm) underwent 18F-FDG PET and CT angiography at baseline and 9 mo later. Clinical and imaging parameter correlates of the 9-mo increase in maximal diameter were investigated; these included 18F-FDG maximal standardized uptake values (SUVmax) averaged for slices encompassing the AAA volume. Results: Of the 39 patients, 9 (23%) had a significant (≥2.5 mm) increase in maximal diameter at 9 mo, whereas the remaining 30 did not. The patients with an increase in maximal diameter at 9 mo exhibited lower SUVmax within the AAA at baseline than patients who did not have such an increase (1.80 ± 0.45 vs. 2.21 ± 0.52; P = 0.04); they also displayed a trend toward greater changes in SUVmax at 9 mo (difference between 9 mo and baseline: +0.40 ± 0.85 vs. −0.06 ± 0.57; P = 0.07). Similar levels were ultimately reached in both groups at 9 mo (2.20 ± 0.83 and 2.15 ± 0.66). SUVmax was a significant, yet modest, baseline predictor of the absolute change in maximal diameter during follow-up (P = 0.049). Conclusion: The enhancement in the maximal diameter of small AAA was preceded by a stage with a low level of 18F-FDG uptake, but this low level of uptake was no longer documented after the growth phases, suggesting a pattern of cyclic metabolic changes.

Age-related changes in FDG brain uptake are more accurately assessed when applying an adaptive template to the SPM method of voxel-based quantitative analysis

IntroductionThe impact of age is crucial and must be taken into account when applying a voxel-based quantitative analysis on brain images from [18F]-fluorodeoxyglucose Positron Emission Tomography (FDG-PET). This study aimed to determine whether age-related changes in brain FDG-PET images are more accurately assessed when the conventional statistical parametric mapping (SPM) normalization method is used with an adaptive template, obtained from analysed PET images using a Block-Matching (BM) algorithm to fit with the characteristics of these images.MethodsAge-related changes in FDG-PET images were computed with linear models in 84 neurologically healthy subjects (35 women, 19 to 82-year-old), and compared between results provided by the SPM normalization algorithm applied on its dedicated conventional template or on the adaptive BM template. A threshold P value of 0.05 was used together with a family-wise error correction.ResultsThe age-related changes in FDG-PET images were much more apparent when computed with the adaptive template than with the conventional template as evidenced by: (1) stronger correlation coefficients with age for the overall frontal and temporal uptake values (respective R2 values of 0.20 and 0.07) and (2) larger extents of involved areas (13 and 5xa0% of whole brain template volume, respectively), leading to reveal several age-dependent areas (especially in dorsolateral prefrontal, inferior temporal/fusiform and primary somatosensory cortices).ConclusionAge-related changes in brain FDG uptake may be more accurately determined when applying the SPM method of voxel-based quantitative analysis on a template that best fits the characteristics of the analysed TEP images.

Influence of Thoracic Aortic Inflammation and Calcifications on Arterial Stiffness and Cardiac Function in Older Subjects.

BackgroundVascular aging is accompanied by gradual remodeling affecting both arterial and cardiac structure and mechanical properties. Hypertension is suggested to exert pro-inflammatory actions enhancing arterial stiffness.ObjectivesTo determine the influence of thoracic aortic inflammation and calcifications on arterial stiffness and cardiac function in hypertensive and normotensive older subjects.DesignA prospective study.SettingAn acute geriatrics ward of the University Hospital of Nancy in France.SubjectsThirty individuals ≥ 65 years were examined, including 15 hypertensive subjects and 15 controls well-matched for age and sex.MeasurementsApplanation tonometry was used to measure aortic pulse wave velocity (AoPWV) and carotid/brachial pulse pressure amplification (PPA). Left ventricular parameters were measured with magnetic resonance imaging. Local thoracic aortic inflammation and calcification were measured by 18 F-fluorodeoxyglucose positron emission tomography/computed tomography imaging. Biomarkers of low-grade inflammation were also quantified.ResultsAoPWV was higher in elderly hypertensive subjects comparatively to normotensive controls (15.5±5.3 vs. 11.9±2.5, p=0.046), and hypertensives had a higher calcification volume. In the overall population, calcifications of the thoracic descending aorta and inflammation of the ascending aorta accounted for respectively 18.1% (p=0.01) and 9.6% (p=0.07) of AoPWV variation. Individuals with high levels of calcifications and/or inflammation had higher AoPWV (p=0.003). Inflammation had a negative effect on PPA explaining 13.8% of its variation (p<0.05).ConclusionsThis study highlights the importance of local ascending aortic inflammation as a potential major actor in the determination of PPA while calcifications and hypertension are more linked to AoPWV. Assessment of PPA in the very elderly could provide complementary information to improve diagnostic and therapeutic strategies targeting ascending aortic inflammation.

Changes in dorsolateral prefrontal connectivity after rTMS in treatment-resistant depression: a brain perfusion SPECT study

PurposeRepetitive transcranial magnetic stimulation (rTMS) is a non-invasive and safe alternative to electroconvulsive therapy for treatment-resistant depression (TRD). After rTMS, changes in brain SPECT perfusion have been remotely identified within medial temporal limbic areas, while no local effects have been found within the left dorsolateral prefrontal cortex (DLPFC)—i.e. under the coil. Functional changes in connectivity may underlie these remote effects. Interestingly, functional connectivity has been recently investigated using perfusion SPECT, and abnormalities identified in TRD patients. The aim of the present study is to evaluate perfusion and connectivity SPECT changes in TRD patients after rTMS of the left DLPFC. We hypothesize that changes in DLPFC networks may explain remote hypoperfusions found after rTMS.MethodsFifty-eight TRD patients underwent a brain SPECT before and after high-frequency rTMS of the left DLPFC. Whole-brain voxel-based changes in perfusion were evaluated with SPM8, and inter-regional correlation analysis performed to study left DLPFC functional connectivity (pu2009<u20090.005, corrected for cluster volume).ResultsAfter rTMS, patients were significantly improved on Beck Depression Inventory score (pu2009<u20090.0001). Considering a 50% reduction threshold, 27 patients were identified as responders (47%). After rTMS, perfusion changes were not found locally within the left DLPFC, but remotely within the bilateral temporal lobes, including limbic areas. Inter-regional correlation SPECT analysis brings out a decrease of connectivity between the left DLPFC and both the cingulate/medial frontal cortex and bilateral medial temporal limbic areas, in relation with the clinical response.ConclusionsrTMS of DLPFC in TRD patients leads to remote temporal hypoperfusions in relation with changes in functional connectivity between the DLPFC and the default mode network, especially including medial temporal limbic areas.

Temporal epilepsy lesions may be detected by the voxel-based quantitative analysis of brain FDG-PET images using an original block-matching normalization software

AbstractIntroductionnStatistical parametric mapping (SPM) provides useful voxel-by-voxel analyses of brain images from 18F-fluorodesoxyglucose positron emission tomography (FDG-PET) after an initial step of spatial normalization through an anatomical template model. In the setting of the preoperative workup of patients with temporal epilepsy, this study aimed at assessing a block-matching (BM) normalization method, where most transformations are computed through small blocks, a principle that minimizes artefacts and overcomes additional image-filtering.nMethodsBrain FDG-PET images from 31 patients with well-characterised temporal lobe epilepsy and among whom 22 had common mesial temporal lobe epilepsy were retrospectively analysed using both BM and conventional SPM normalization methods and with PET images from age-adjusted controls. Different threshold p values corrected for cluster volume were considered (0.01, 0.005, and 0.001).ResultsThe use of BM provided equivalent values to those of SPM with regard to the overall volumes of temporal and extra-temporal hypometabolism, as well as similar sensitivity for detecting the involved temporal lobe, reaching 87 and 94xa0% for SPM and BM, respectively, at a threshold p value of 0.01. However, the ability to more accurately localize brain lesions within the mesial portion of the temporal lobe was a little higher with BM than with SPM with respective sensitivities reaching 78xa0% for BM and 45xa0% for SPM (pxa0<xa00.05).ConclusionsBM normalization compares well with conventional SPM for the voxel-based quantitative analysis of the FDG-PET images from temporal epilepsy patients. Further studies in different population are needed to determine whether BM is truly an accurate alternative to SPM in this setting.

Comparison of O-(2-18F-Fluoroethyl)-L-Tyrosine Positron Emission Tomography and Perfusion-Weighted Magnetic Resonance Imaging in the Diagnosis of Patients with Progressive and Recurrent Glioma: A Hybrid Positron Emission Tomography/Magnetic Resonance Study

OBJECTIVEnTo compare the diagnostic performance of O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) positron emission tomography (PET) and perfusion-weighted magnetic resonance imaging (PWI) for the diagnosis of progressive or recurrent glioma.nnnMETHODSnThirty-two pretreated gliomas (25 progressive or recurrent tumors, 7 treatment-related changes) were investigated with 18F-FET PET and PWI via a hybrid PET/magnetic resonance scanner. Volumes of interest with a diameter of 16 mm were centered on the maximum of abnormality in the tumor area in PET and PWI maps (relative cerebral blood volume, relative cerebral blood flow, mean transit time) and the contralateral unaffected hemisphere. Mean and maximum tumor-to-brain ratios as well as dynamic data for 18F-FET uptake were calculated. Diagnostic accuracies were evaluated by receiver operating characteristic analyses, calculating the area under the curve.nnnRESULTSn18F-FET PET showed a significant greater sensitivity to detect abnormalities in pretreated gliomas than PWI (76% vs. 52%, Pxa0= 0.03). The maximum tumor-to-brain ratio of 18F-FET PET was the only parameter that discriminated treatment-related changes from progressive or recurrent gliomas (area under the curve, 0.78; Pxa0= 0.03, best cut-off 2.61; sensitivity 80%, specificity 86%, accuracy 81%). Among patients with signal abnormality in both modalities, 75% revealed spatially incongruent local hot spots.nnnCONCLUSIONSnThis pilot study suggests that 18F-FET PET is superior to PWI to diagnose progressive or recurrent glioma.

Brain molecular imaging in pharmacoresistant focal epilepsy: Current practice and perspectives

This review aims to synthesize all the available data on brain molecular imaging, such as single-photon emission computed tomography (SPECT) and interictal fluorodeoxyglucose positron emission tomography (FDG-PET), in focal epilepsies. SPECT imaging is able to measure regional cerebral blood flow and its major innovation remains its ictal imaging value. On the other hand, FDG-PET, which has higher spatial resolution and lower background activity than SPECT, enables glycolytic metabolism to be identified in interictal states. Therefore, interictal FDG-PET has greater sensitivity than interictal SPECT, especially in temporal lobe epilepsies (TLEs). Thus, 18F-FDG-PET is a necessary step in the presurgical evaluation of TLEs, but also of extratemporal epilepsies (ETEs), contributing to >30% of the decision to undertake surgery. In addition, FDG-PET has particular diagnostic value in focal epilepsies showing normal magnetic resonance imaging (MRI). PET also has good prognostic value for post-surgical outcomes as well as cognitive impairment, especially in cases where the hypometabolism extent is limited. Moreover, the notion of an epileptic network is well highlighted by functional PET imaging, allowing better understanding of the pathological substrates of these disorders. Future development of quantitative analysis software and of novel radiotracers and cameras will certainly enhance its clinical usefulness.