Stelvio Sestini

Comparison of baseline-nitrate technetium-99m sestamibi with rest-redistribution thallium-201 tomography in detecting viable hibernating myocardium and predicting postrevascularization recovery.

OBJECTIVES This study aimed to define the optimal criteria for detecting viable myocardium with rest-redistribution thallium-201 (Tl-201) or baseline-nitrate technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) using discriminant analysis and to compare the accuracy of the two tracers in predicting postrevascularization recovery. BACKGROUND Rest-redistribution Tl-201 imaging is currently used for detection of myocardial viability, but the optimal variables for territory classification have not yet been defined. Although Tc-99m sestamibi is reportedly less effective than Tl-201, its reliability can be increased by injecting it during nitrate infusion. METHODS In 35 patients with left ventricular (LV) dysfunction, tracer activity within asynergic coronary territories was quantified on rest and redistribution Tl-201 and baseline and nitrate Tc-99m sestamibi SPECT. Asynergic territory viability was evaluated on the basis of the postrevascularization functional outcome. RESULTS Percent activity within asynergic territories was significantly influenced by their viability (p < 0.005) and the type of acquisition (p < 0.0001) but not by the tracer used. Discriminant analysis identified redistribution Tl-201 activity and nitrate-induced Tc-99m sestamibi activity change as the two most significant predictors of postrevascularization recovery. The discriminant function defined for Tl-201, including redistribution activity and reversibility, correctly classified 38 of 56 asynergic territories, whereas that for Tc-99m sestamibi, including nitrate-induced activity change and activity in nitrate images, correctly classified 43 territories. CONCLUSIONS Redistribution activity is more important than reversibility when differentiating viable from nonviable territories using rest-redistribution Tl-201. In Tc-99m sestamibi SPECT, nitrate-induced activity changes are particularly useful in identifying myocardial viability. Baseline-nitrate Tc-99m sestamibi SPECT appears no less effective than rest-redistribution Tl-201 in predicting postrevascularization recovery.

Usefulness of Dobutamine Tc-99m Sestamibi-Gated Single-Photon Emission Computed Tomography for Prediction of Left Ventricular Ejection Fraction Outcome After Coronary Revascularization for Ischemic Cardiomyopathy

Gated single-photon emission computed tomography (SPECT) imaging allows analysis of myocardial perfusion and assessment of baseline global and regional left ventricular (LV) function and their changes during low-dose dobutamine infusion. The study examined whether the changes in LV ejection fraction induced by dobutamine and evaluated using technetium-99m sestamibi- gated SPECT predict the evolution of ejection fraction after revascularization in patients with ischemic cardiomyopathy. Thirty-seven patients underwent resting and dobutamine nitrate-enhanced sestamibi-gated SPECT before revascularization and baseline-resting sestamibi gated SPECT after intervention to assess global functional changes. A postrevascularization improvement in ejection fraction > or =5 U was defined as significant. At follow-up, ejection fraction increased significantly in 19 patients. According to receiver-operating characteristic curve analysis, an increase in ejection fraction > or =5 U during dobutamine was the optimal cutoff value for predicting a significant postrevascularization improvement, with 79% sensitivity, 78% specificity, and 78% accuracy. A significant correlation was found between dobutamine and postrevascularization ejection fraction (r = 0.85; p <0.0001). The increase in ejection fraction during dobutamine is a good predictor of an improvement in ejection fraction after revascularization. This represents another important diagnostic contribution obtained using gated SPECT imaging for the assessment of myocardial viability in patients with ischemic cardiomyopathy.

The new FDG brain revolution: the neurovascular unit and the default network

F-fluorodeox-yglucose (FDG), it was possible to see and study the livingbrain in humans! Pioneers were top experts who provideddifferent specialized expertise, but strictly cooperatingbetween themselves [1]. Physicists, engineers and mathe-maticians were actively involved in producing the besthardware and software. The research on crystals, inidentifying the most effective electronics, in definingaccurate methods for attenuation and scatter correctionand so on, was nevertheless limited by the relatively poortechnology, with the main consideration being limitedcomputer power. These developments stimulated a majorinterest in the brain. Satisfactory sensitivity and resolution,together with reliable solutions to the technical problems,were only achieved with dedicated cerebral PET scannerswhich had a field of view that permitted exclusive analysisof the brain.Basic scientists had the possibility of realizing ascientific dream: the transfer of data on cerebral glucosemetabolism acquired in animals by quantitative autoradi-ography to humans. Another issue in the original FDG PETresearch was to consider mandatory absolute quantification.Thus arterial (or arterialized) sampling, to obtain data to beincluded in mathematical models, was routinely performed.However, because the equations included nonmeasurableparameters, the presence of a lumped constant affectedabsolute measurement in an individual [2–4]. PET teamsincluded (and were directed by) clinical experts includingnot only nuclear physicians, but also other professionalssuch as neuroradiologists, neurologists and psychiatrists,who frequently cooperated with psychologists, anatomistsand physiologists.Because of the unsatisfactory spatial resolution and thenegative influence of the partial volume effect, inpresence of glucose uptake in the normal brain, only alow lesion/background ratio was achievable, except forhot spots, i.e. the presence of focal areas of increaseduptake determined by physiological and/or pathologicalcauses. Therefore, the use of FDG as a positive indicatorwasrestrictedinthefirststudiesandinthesearchforhotspots, many studies involved physiological stimulationtests (closed/open eyes, auditory system, etc.) in normalsubjects [5, 6]. Similarly, major interest in pathologicalanalysis was directed to the evaluation of brain tumours,starting from Warburg’s hypothesis of higher FDG uptakein malignant lesions with respect to benign ones [7]. Withfurther clinical experience, in the analysis of patients withepilepsy, a higher sensitivity was clearly demonstratedduring the ictal phase, the focus being seen as a hot spot,with respect to the interictal period when the lesion wasnot easily detectable, being an area with a slightly reducedoverall FDG uptake [8, 9]. Discrepant results in epilepsyclearly demonstrate how, in the absence of a structurallesion evident on CT, it is more difficult to search for afunctional alteration when it corresponds to an area ofdecreased uptake (cold spot).

Use of technetium-99m hexamethylpropylene amine oxime SPET for the study of cerebral blood flow reactivity after acetazolamide infusion in patients with Behçet's disease

Abstract.The purpose of this study was to characterise the nature of the baseline perfusion defects found in patients with Behçet’s disease using hexamethylpropylene amine oxime single-photon emission tomography in conjunction with acetazolamide test (Acz SPET). Eleven patients underwent both baseline and Acz SPET. Regions of interest (ROIs) were drawn on the areas with decreased perfusion (D-ROI) and, in the same section, on areas with normal perfusion (N-ROI). The ROIs were then repositioned on the corresponding section on Acz SPET. The mean ROI counts were then transformed into a perfusion index value (PIV) with reference to the global brain counts. In total we found 24 D-ROIs (17 in the cortical and 7 in subcortical grey matter). The influence of Acz infusion was selectively registered in the D-ROIs, where PIVs changed from 1.23±0.17 (baseline SPET) to 1.63±0.23 (Acz SPET) (P<0.001). No significant difference was seen in the N-ROIs (1.46±0.21 and 1.40±0.17, respectively, on baseline SPET and Acz SPET). Our results demonstrate that Acz infusion increases the regional cerebral blood flow within baseline grey matter perfusion defects. This finding suggests that baseline perfusion abnormalities could reflect a disconnection rather than local vasculitic involvement.

Use of 99mTc-sestamibi gated SPECT to assess the influence of anterograde flow before primary coronary angioplasty on tissue salvage and functional recovery in acute myocardial infarction

PurposePreserved thrombolysis in myocardial infarction (TIMI) flow before percutaneous coronary intervention (PCI) in acute myocardial infarction is related to improved outcome. Gated single-photon emission computed tomography (SPECT) allows the simultaneous assessment of left ventricular perfusion and function. We evaluated the initial risk area and subsequent evolution of perfusion and function according to TIMI flow before successful primary PCI.Methods In 36 patients, treated with abciximab, primary PCI and stenting, 99mTc-sestamibi was injected before PCI and gated SPECT acquired thereafter. Gated SPECT was repeated 7 and 30 days later. Perfusion defect, wall motion score index, left ventricular ejection fraction and volumes were examined.Results Before PCI, 14 patients (group A) showed TIMI flow 2–3 and 22 (group B) TIMI flow 0–1, but no differences in clinical variables, initial risk area, wall motion score, ejection fraction or volumes. Perfusion defect was smaller in group A at 7 (9%±11% vs 19%±14%, p<0.02) and 30 days (7%±7% vs 16%±12%, p<0.02) and the salvage index was higher at 30 days (77%±22% vs 55%±28%, p<0.02). Wall motion score was lower in group A at 30 days (p<0.05). Ejection fraction significantly improved in both groups at 7 and 30 days. End-diastolic volume showed a trend towards a reduction in group A, whilst it was significantly increased in group B. Conversely, end-systolic volume was significantly decreased in group A but remained unchanged in group B.ConclusionIn the setting of optimal myocardial reperfusion for myocardial infarction, preserved TIMI flow before PCI does not limit the initial risk area but it does improve myocardial salvage and functional recovery.

Brain Network Underlying the Improvement of Social Functioning in Schizophrenic Patients After One-year Treatment with Social Skills Training

PURPOSE To assess changes in social and neuro-cognition and regional cerebral blood flow (rCBF) in schizophrenic patients with psychotic syndrome treated with Social Skill Training (SST). METHODS 17 patients underwent two high resolution rCBF SPECT at rest before and after a one-year treatment with SST. Patients were assessed using a neuropsychological evaluation (W.A.I.S.-R, T.M.T, Verbal Fluency, W.C.S.T.). SPM8 was used to investigate rCBF changes from the pre- to the post-SST condition and the relationship between rCBF and clinical scores used as covariates of interest. RESULTS All patients presented with an improvement in social perception, ability to deal with abstract social conventions, rules and judgments about people (Comprehension and Picture Completion sub-tests) and some neuro-cognitive functions sustaining the process of socially relevant information. The main effect of SST was to produce rCBF increases in precuneus, PCC, superior parietal lobules, PMC, pre-SMA, precentral gyrus, dmPFC, dlPFC, vmPFC, OFC (p<0.0001 uncorrected). The SPM analysis showed that Comprehension was supported by PMC, dmPFC, OFC and vmPFC, while the Picture Completion was supported by PMC and dmPFC (p<0.0001). CONCLUSION SST in schizophrenic patients improves resting neural activity in cortical areas of the amigdala-based and non-amygdala networks of social brain, including dmPFC and vmPFC, and dlPFC, which are known to be part of default mode and task-positive networks and to be implicated in schizophrenia.

Pharmacokinetic analysis of plasma curves obtained after i.v. injection of the PET radioligand [11C] raclopride provides a likely explanation for rapid radioligand metabolism.

Positron emission tomography (PET) is an imaging technique that provides direct measurements of receptor binding in neurons. The present study was performed to find reasons for the common observation of rapid metabolism of receptor radioligands during time of a brain PET scan. To this aim, the 1‐h phase during which imaging‐data are acquired was evaluated by using a pharmacokinetic approach. The values of half‐lives, volumes of distribution, and dilution calculated for a set of metabolite corrected plasma curves of D2‐receptor radioligand [11C]raclopride (PETc) during 50 min after radioligand injection in tracer dose were compared with the reference values obtained from a set of plasma curves (REFc) during 30 h after i.v. infusion of unlabelled raclopride in pharmacological doses. We found that the half‐life of PETc correspond to the distribution half‐life of REFc. Accordingly, the distribution volume during the terminal phase of PETc (13.6 ± 10.8 L) was significantly lower than that during the terminal phase (82.2 ± 30.5 L) and at steady state (59.4 ± 20 L) for REFc, and the dilution of raclopride in body for PETc at 50 min was 38 L, whereas it was 1015 L for REFc at 30 h. The [11C]raclopride in plasma at 50 min was higher (10% of dose) than the value for unlabelled raclopride at 30 h (4%). We concluded that the kinetic behavior of the radiolabelled drug [11C]raclopride during the 1 h time of a PET corresponds to the distribution phase. The high percentage of [11C]raclopride in plasma during this phase is a likely reason for the observed rapid radioligand metabolism. J. Cell. Physiol. 227: 1663–1669, 2012.