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P Véra

Publications and source records attributed to P Véra.

At least 19 recordsLinked to original sources
PubMed2005

Validation of the Monte Carlo simulator GATE for indium-111 imaging.

Monte Carlo simulations are useful for optimizing and assessing single photon emission computed tomography (SPECT) protocols, especially when aiming at measuring quantitative parameters from SPECT images. Before Monte Carlo simulated data can be trusted, the simulation model must be validated. The purpose of this work was to validate the use of GATE, a new Monte Carlo simulation platform based on GEANT4, for modelling indium-111 SPECT data, the quantification of which is of foremost importance for dosimetric studies. To that end, acquisitions of (111)In line sources in air and in water and of a cylindrical phantom were performed, together with the corresponding simulations. The simulation model included Monte Carlo modelling of the camera collimator and of a back-compartment accounting for photomultiplier tubes and associated electronics. Energy spectra, spatial resolution, sensitivity values, images and count profiles obtained for experimental and simulated data were compared. An excellent agreement was found between experimental and simulated energy spectra. For source-to-collimator distances varying from 0 to 20 cm, simulated and experimental spatial resolution differed by less than 2% in air, while the simulated sensitivity values were within 4% of the experimental values. The simulation of the cylindrical phantom closely reproduced the experimental data. These results suggest that GATE enables accurate simulation of (111)In SPECT acquisitions.

Algorithms↗
PubMed2001

Functional imaging in the work-up of childhood epilepsy.

In children with medically intractable lesional epilepsy, surgery is deemed successful if the epileptogenic focus can be removed while major neurological functions are spared. Current techniques rely on invasive intracranial recordings. The new developments in functional imaging offer the possibility of localizing the epileptogenic focus noninvasively (PET/SPECT) and mapping cognitive functions (fMRI). Ictal SPECT shows hyperperfusion in the focus and has proved to have better localizing value than interictal PET or SPECT, which show focal hypometabolism or hypoperfusion. Ictal SPECT is useful for deciding on the placement of intracranial electrodes in extratemporal epilepsies, particularly in young children. Functional MRI has proved highly accurate for localizing motor and language networks, thus offering the possibilities of replacing the Wada test (language hemispheric lateralization) and studying postlesional brain plasticity. Despite the difficulties of functional imaging in children owing to the limited cooperation that can be expected, ethical constraints, and poor normative data, SPECT/PET and fMRI provide clinically useful information for presurgical work-up of childhood epilepsies.

Adolescent↗
PubMed2001

Exercise-induced ST-elevation is related to left ventricular dysfunction but not to myocardial viability in patients with healed myocardial infarction.

BACKGROUND: Exercise-induced ST-segment elevation was proposed as a marker of myocardial viability after a recent myocardial infarction. AIMS: The aim of this study was to evaluate whether exercise-induced ST segment elevation is related to viability or to left ventricular dysfunction in patients with history of old Q wave myocardial infarction. METHODS: Fifty patients (43 men, age 57+/-11 years) were studied 31+/-49 months after a Q wave myocardial infarction. They all underwent stress, reinjection-redistribution, and late redistribution Tl-201 SPECT, completed by equilibrium radionuclide angiography. Viability was defined by defect reversibility or significant (>60%) persistent Tl-201 uptake in dyssinergic segments on late redistribution SPECT. Relative post-exercise and reinjection-redistribution LV volumes were calculated using validated software (QGS). RESULTS: Twenty-one out of 50 patients (42%, G1) had significant stress-induced ST-elevation (>1 mm 80 ms after J point in at least 2 ECG leads with Q wave), and 29/50 (58%, G2) did not. Seventeen out of 50 patients (34%) demonstrated myocardial viability on late redistribution scan. The diagnostic accuracy of exercise-induced ST-elevation was only 52% for viability assessment. Significant LVEF reduction and increased relative LV volumes were observed in G1 compared to G2 (LVEF: 39+/-10% vs. 49+/-11%, P=0.003; post-stress LV volume: 134+/-98 ml vs. 81+/-41 ml, P<0.02; reinjection-redistribution LV volume: 123+/-86 ml vs. 79+/-40 ml; P<0.02). Perfusion defects were similar in G1 and G2 (post-exercise: 38+/-12% vs. 37+/-14%, ns; reinjection-redistribution: 31+/-11% vs. 30+/-11%, ns; late redistribution: 30+/-10% vs. 28+/-11%, ns). CONCLUSION: These results suggest that, in patients with history of myocardial infarction, exercise-induced ST-segment elevation is not related to persistent myocardial viability but is associated to left ventricular dysfunction.

Aged↗
PubMed2001

Ictal perfusion changes during occipital lobe seizures in infancy: report of two serial ictal observations.

Serial-ictal single-photon-emission computed tomography (SPECT) examinations are presented in two infants (ages 1 and 2 years), with early ictal and ictal in one, and ictal and late ictal images in the other. Both had pharmacoresistant occipital epilepsy, due to focal cortical dysplasia. In the first case, size of ictal hyperperfusion increased in the course of the seizure from early ictal to ictal state. A concomitant ictal hypoperfusion was observed around the hyperperfused area. In the second patient, there was a dramatic difference between ictal and late ictal images. In the late ictal state, the previous occipital ictal hyperperfusion and extraoccipital ictal hypoperfusion disappeared, together with homolateral posterotemporal and contralateral occipital hyperperfusion, corresponding to seizure propagation. Ictal extratemporal blood-flow changes are therefore highly dynamic, particularly in very young children.

Age Factors↗
PubMed2001

[Evaluation of the ejection fraction tomoscintigraphy synchronised with an electrocardiogram].

Electrocardiographic gated myocardial scintigraphy (gated SPECT) allows simultaneous evaluation of left ventricular perfusion and contractility. The aim of this study was to assess the impact of the type of tracer and temporal sampling on the measurement of the ejection fraction by gated SPECT. Eighty-six consecutive patients (59 men, 27 women, average age 62 +/- 11 years) with a history of myocardial infarction (anterior N = 50--inferior N = 36) were studied. All had measurement of the isotopic ejection fraction by equilibrium angioscintigraphy and by gated SPECT sampled at 8 (N = 45, 52%) or 16 images/cycle RR (N = 41, 48%). After filtered retroprojection, the ejection fraction was calculated by a validated method (QGS). A better correlation between gated SPECT and equilibrium angioscintigraphy was observed at 16 images/cycle (r = 0.90) compared with 8 (r = 0.80). The Bland-Altman curves showed improved accuracy of the measurement of the ejection fraction by gated SPECT with 16 compared with 8 images/cycles sampling (mean differences of 0.37 +/- 6.06% and 4.3 +/- 7.71%, respectively). Multivariable analysis showed that temporary sampling was the only parameter to significantly affect the difference between the two methods. There was no difference between the use of Thallium and that of 99mTc-sestamibi. Gated SPECT, therefore, provides an accurate measurement of the ejection fraction for routine clinical usage, providing the acquisition is made at 16 images/cycle.

Electrocardiography↗
PubMed2000

Effect of temporal sampling on evaluation of left ventricular ejection fraction by means of thallium-201 gated SPET: comparison of 16- and 8-interval gating, with reference to equilibrium radionuclide angiography.

Gated myocardial single-photon emission tomography (SPET) allows the evaluation of left ventricular ejection fraction (LVEF), but temporal undersampling may lead to systolic truncation and ejection fraction underestimation. The aim of this study was to evaluate the impact of temporal sampling on thallium gated SPET LVEF measurements. Fifty-five consecutive patients (46 men, mean age 62+/-12 years) with a history of myocardial infarction (anterior 31, inferior 24) were studied. All patients underwent equilibrium radionuclide angiography (ERNA) and gated SPET 4 h after a rest injection of 185 MBq (5 mCi) of thallium-201 using either 8-interval (group 1, n=25) or 16-interval gating (group 2, n=30). In group 2, gated SPET acquisitions were automatically resampled to an 8-interval data set. Projection data were reconstructed using filtered back-projection (Butterworth filter, order 5, cut-off 0.20). LVEF was then calculated using commercially available software (QGS). A higher correlation between gated SPET and ERNA was obtained with 16-interval gating (r=0.94) compared with the resampled data set (r=0.84) and 8-interval gating (r=0.71). Bland-Altman plots showed a dramatic improvement in the agreement between gated SPET and ERNA with 16-interval gating (mean difference: -0.10%+/-5%). Using multiple ANOVA, temporal sampling was the only parameter to influence the difference between the two methods. When using 8-interval gating, gated SPET LVEF was overestimated in women and underestimated in men (ERNA minus gated SPET = -4.0%+/-9.6% in women and 3.6%+/-7.6% in men, P=0.01). In conclusion, 16-interval thallium gated SPET offered the best correlation and agreement with ERNA, and should be preferred to 8-interval gated acquisition for LVEF measurement.

Adult↗
PubMed2000

Therapeutic efficacy of intralesional 131I-labelled hyaluronectin in grafted human glioblastoma.

The grafted human glioblastoma cell CB109 was used as a model for intralesional therapy with 131I-labelled hyaluronectin glycoprotein (131I-HN).131I-HN bound specifically to in situ hyaluronic acid (HA), a main component of the extracellular matrix which is involved in tumour invasion. Labelling experimental conditions were determined and, finally, 25 microCi/microgHN, 1 microg chloramine-T/microgHN and a 60-s stirring period provided a 131I-HN preparation with an optimal affinity for HA (64% compared to unlabelled HN). Following intratumoral injection, 131I-HN was retained with a limited diffusion outside the tumour. On day 4 the radioactivity concentrated in the tumour was still 25 times greater than that in the liver, spleen and kidneys combined. For therapeutic assays, 65 microCi 131I-HN was injected into the tumour, resulting in a delivery of 6.8 Gy over a 7-day period. Controls received unlabelled HN, heat-inactivated HN, a mixture of inactivated HN plus free 131I or no treatment (six animals per group). Tumour volumes were evaluated every second day from treatment day and the rate of tumour growth was expressed as a ratio of tumour size at time intervals to the tumour size at the time of injection. Growth curves were compared: heat-inactivated with or without free 131I had no anti-tumour effect. Unlabelled HN-injected tumours had a slightly slower growth rate than untreated tumours (p < 0.02) and growth rate of 131I-HN-injected tumours was much lower (p < 0.00002). A pronounced inhibitory effect with intralesional 131I-labelled HN injection resulted from a combination of a) blockage of HA, a proliferation facilitating factor, and b) local irradiation of tumoral tissue, while uptake in normal tissues was minimized.

Animals↗
PubMed1999

Shortcomings of diuresis scintigraphy in evaluating urinary obstruction: comparison with pressure flow studies.

BACKGROUND: In at least 15 % of dilated urinary tracts, diuresis renography fails to assess the presence or absence of urinary obstruction. OBJECTIVE: To determine the shortcomings of (99 m)Tc-DTPA frusemide diuresis renography by reference to pressure flow studies. MATERIALS AND METHODS: Thirty-four patients, aged 1 month to 20 years, with questionable obstruction were evaluated by diuresis renography and pressure flow studies (the Whitaker test) as the reference method during the same short period of time. Discrepancies were analysed. RESULTS: In patients with type I or IIIa renographic response, pressure flow studies never led to any change in management. Poor function, major dilatation and prior surgery were found to be risk factors of inaccurately obstructive pattern (type II) on renography (n = 6). In patients with type IIIb response, pressure flow studies could show low-grade (n = 3) or intermittent obstruction (n = 2). Intermittent obstruction was also demonstrated in two patients with type II response. CONCLUSION: In patients with risk factors, type II response was sometimes inaccurate, and urodynamic evaluation showed absence of obstruction and led to conservative management. Type IIIb response should be considered equivocal rather than partially obstructive, and pressure flow studies could be considered in such patients.

Adolescent↗
PubMed1999

Contribution of single-photon emission computed tomography in the diagnosis and follow-up of CNS toxicity of a cytarabine-containing regimen in pediatric leukemia.

PURPOSE: Cytarabine (ara-C) is one of the most effective chemotherapeutic agents in patients with acute leukemia (AL), with a clear dose effect. Use of high-dose ara-C is hampered, however, by a noticeable toxicity, particularly to the CNS. We investigated the usefulness of CNS perfusion imaging with technetium-99m ((99m)Tc)-hexamethyl-propylene-amine oxime (HMPAO) single-photon emission computed tomography (SPECT) concurrent to magnetic resonance imaging (MRI) to specifically assess the effects of standard- and high-dose ara-C in children with AL. PATIENTS AND METHODS: Twenty-six perfusion studies using (99m)Tc-HMPAO SPECT were performed in 12 children (age range, 4 to 15 years) with AL after induction therapy, which consisted of a standard-dose ara-C, immediately after consolidation with high-dose ara-C, and later during follow-up (range, 6 to 44 months). The chemotherapy-related adverse events were monitored and correlated to SPECT and MRI. RESULTS: After the induction phase, all children were neurologically normal on MRI. On SPECT imaging, four children displayed a slightly heterogeneous perfusion. After high-dose ara-C (4 to 36 g/m(2)), five children had regressive neurologic signs of potential toxic origin. Of these five children, only one had an abnormal MRI scan, whereas all patients showed evidence of diffuse cerebral and/or cerebellar heterogeneous perfusion on SPECT. The seven other patients without any neurologic symptoms had normal MRI scans; SPECT was normal for three patients and abnormal for four patients. On follow-up, for four children who had presented with clinical neurologic toxicity, SPECT improved in three patients and remained unchanged in one patients. In two of these four children, delayed abnormalities (T2 white matter hypersignal and cerebellar atrophy) appeared on MRI scans. CONCLUSION: In our series, diffuse heterogeneous brain hypoperfusion is often the sole early objective imaging feature identified by SPECT of high-dose ara-C neurotoxicity, where MRI still demonstrates normal pictures.

Adolescent↗
PubMed1999

Thallium-gated SPECT in patients with major myocardial infarction: effect of filtering and zooming in comparison with equilibrium radionuclide imaging and left ventriculography.

UNLABELLED: The effect of filtering and zooming on 201TI-gated SPECT was evaluated in patients with major myocardial infarction. METHODS: Rest thallium (TI)-gated SPECT was performed with a 90 degrees dual-head camera, 4 h after injection of 185 MBq 201TI in 32 patients (mean age 61 +/- 11 y) with large myocardial infarction (33% +/- 17% defect on bull's eye). End diastolic volume (EDV), end systolic volume (ESV) and left ventricular ejection fraction (LVEF) were calculated using a commercially available semiautomatic validated software. First, images were reconstructed using a 2.5 zoom, a Butterworth filter (order = 5) and six Nyquist cutoff frequencies: 0.13 (B5.13), 0.15 (B5.15), 0.20 (B5.20), 0.25 (B5.25), 0.30 (B5.30) and 0.35 (B5.35). Second, images were reconstructed using a zoom of 1 and a Butterworth filter (order = 5) (cutoff frequency 0.20 [B5.20Z1]) (total = 32 x 7 = 224 reconstructions). LVEF was calculated in all patients using equilibrium radionuclide angiocardiography (ERNA). EDV, ESV and LVEF were measured with contrast left ventriculography (LVG). RESULTS: LVEF was 39% +/- 2% (mean +/- SEM) for ERNA and 40% +/- 13% for LVG (P = 0.51). Gated SPECT with B5.20Z2.5 simultaneously offered a mean LVEF value (39% +/- 2%) similar to ERNA (39% +/- 2%) and LVG (40% +/- 3%), optimal correlations with both ERNA (r = 0.83) and LVG (r = 0.70) and minimal differences with both ERNA (-0.9% +/- 7.5% [mean +/- SD]) and LVG (1.1% +/- 10.5%). As a function of filter and zoom choice, correlation coefficients between ERNA or LVG LVEF, and gated SPECT ranged from 0.26 to 0.88; and correlation coefficients between LVG and gated SPECT volumes ranged from 0.87 to 0.94. There was a significant effect of filtering and zooming on EDV, ESV and LVEF (P < 0.0001). Low cutoff frequency (B5.13) overestimated LVEF (P < 0.0001 versus ERNA and LVG). Gated SPECT with 2.5 zoom and high cutoff frequencies (B5.15, B5.20, B5.25, B5.30 and B5.35) overestimated EDV and ESV (P < 0.04) compared with LVG. This volume overestimation with TI-gated SPECT in patients with large myocardial infarction was correlated to the infarct size. A zoom of 1 underestimated EDV, ESV and LVEF compared with a 2.5 zoom (P < 0.02). CONCLUSION: Accurate LVEF measurement is possible with TI-gated SPECT in patients with major myocardial infarction. However, filtering and zooming greatly influence EDV, ESV and LVEF measurements, and TI-gated SPECT overestimates left ventricular volumes, particularly when the infarct size increases.

Female↗
PubMed1999

Use of subtraction ictal SPECT co-registered to MRI for optimizing the localization of seizure foci in children.

UNLABELLED: Ictal SPECT studies are increasingly used to localize seizure foci in children with refractory epilepsy, but few studies have reported on ictal-interictal subtraction images co-registered to MRI at this age. METHODS: Twenty-seven children with partial epilepsy (aged 3 mo-18 y) underwent ictal ethyl cysteinate dimer (ECD) SPECT (20 mCi/1.73 m2) combined with video-electroencephalography (EEG) and interictal ECD SPECT followed 2 d later by three-dimensional MRI. Ictal-interictal and interictal-ictal subtraction images were computed by registering and normalizing the ictal to the interictal SPECT scans for each child. The ictal, interictal SPECT and subtraction images were registered to each child's MRI. Difference images (ictal-interictal) were then superimposed on MRI for anatomic localization of the perfusion changes. Intra- and interobserver reproducibility and "facility of interpretation" of overlay images were compared with standard analysis of the non-coregistered ictal and interictal scans. RESULTS: Overlay images allowed the detection of at least one hyperperfused focus in 93% of the children, compared with 74% using ictal and interictal scans separately. Seizure onset was suspected clinically, on EEG or on MRI in 20 children. Overlay images were concordant (n = 11) or larger (n = 7) than the suspected focus in 18 of 20 (90%), whereas these images failed to show any abnormality in 1 child and were discordant with MRI in another patient. In the remaining 7, images showed cortical localization in 6 patients. Among the 5 patients who underwent electrocorticography, overlay images were concordant in 3, larger in 1 and absent in 1. The intra- and interobserver reproducibility and facility of interpretation were significantly higher using overlay images than standard analysis, even when ictal and interictal SPECT were co-registered. CONCLUSION: The co-registration of ictal-interictal subtraction SPECT images to MRI seems to be a helpful technique in localizing the onset of seizure and guiding the intracranial recording in childhood epilepsy. Moreover, this method improves sensitivity, enhances intra- and interobserver reproducibility and makes interpretation easier.

Adolescent↗
PubMed1999

201Tl and 99mTc-MIBI gated SPECT in patients with large perfusion defects and left ventricular dysfunction: comparison with equilibrium radionuclide angiography.

UNLABELLED: Left ventricular ejection fraction (LVEF) is a major prognostic factor in coronary artery disease and may be computed by 99mTc-methoxyisobutyl isonitrile (MIBI) gated SPECT. However, 201Tl remains widely used for assessing myocardial perfusion and viability. Therefore, we evaluated the feasibility and accuracy of both 99mTc-MIBI and 201Tl gated SPECT in assessing LVEF in patients with myocardial infarction, large perfusion defects and left ventricular (LV) dysfunction. METHODS: Fifty consecutive patients (43 men, 7 women; mean age 61 +/- 17 y) with a history of myocardial infarction (anterior, 26; inferior, 18; lateral, 6) were studied. All patients underwent equilibnum radionuclide angiography (ERNA) and rest myocardial gated SPECT, either 1 h after the injection of 1110 MBq 99mTc-MIBI (n = 19, group 1) or 4 h after the injection of 185-203 MBq 201Tl (n = 31, group 2) using a 90 degrees dual-head camera. After filtered backprojection (Butterworth filter: order 5, cutoff 0.25 99mTc or 0.20 201Tl), LVEF was calculated from reconstructed gated SPECT with a previously validated semiautomatic commercially available software quantitative gated SPECT (QGS). Perfusion defects were expressed as a percentage of the whole myocardium planimetered by bull's-eye polar map of composite nongated SPECT. RESULTS: Gated SPECT image quality was considered suitable for LVEF measurement in all patients. Mean perfusion defects were 36% +/- 18% (group 1), 33% +/- 17% (group 2), 34% +/- 17% (group 1 + group 2). LVEF was underestimated using gated SPECT compared with ERNA (34% +/- 12% and 39% +/- 12%, respectively; P = 0.0001). Correlations were high (group 1, r= 0.88; group 2, r = 0.76; group 1 + group 2, r = 0.82), and Bland-Altman plots showed a fair agreement between gated SPECT and ERNA. The difference between the two methods did not vary as LVEF, perfusion defect size or seventy increased or when the mitral valve plane was involved in the defect. CONCLUSION: LVEF measurement is feasible using myocardial gated SPECT with the QGS method in patients with large perfusion defects and LV dysfunction. However, both 201Tl and 99mTc-MIBI gated SPECT similarly and significantly underestimated LVEF in patients with LV dysfunction and large perfusion defects.

Electrocardiography↗
PubMed1999

[Ictal SPECT in the epileptic child. Contribution of subtraction interictal images and superposition of with MRI].

Ictal SPECT is a highly sensitive method to localize the epileptogenic focus in refractory temporal lobe epilepsy in adults. In extratemporal epilepsy, sensitivity can be improved by subtracting interictal from ictal images and superimposing subtraction images on MRI. In children, such a procedure is potentially interesting because most epilepsies are extratemporal and ictal SPECT not yet routinely developed. The aim of this study was to test the feasibility of ictal SPECT with subtraction image processing in a pediatric population. Twenty-six children with refractory partial epilepsy and aged from 3 months to 18 years underwent ictal ECD-SPECT (20 mCi/1.73 m2) combined with video-EEG and interictal ECD-SPECT plus 3D-MRI two days later. Ictal-interictal subtraction images were computed by registering and normalizing the ictal to the interictal SPECT scans for each child. The ictal, interictal SPECT and subtraction images were registered to the children's MRI. Difference images were then superimposed to MRI for anatomical localization of the perfusion changes (overlay images). Looking for perfusion changes, overlay images allowed to detect at least one hyperperfused focus in 92 p. 100 of the 26 children compared to 73 p. 100 visually comparing ictal and interictal scans separately. Seizure onset was suspected on clinical and/or EEG and/or MRI in 19 children. Positive overlay images were concordant (n = 11) or larger (n = 7) than the suspected focus in 17/19 (90 p. 100), whereas they failed to show any abnormality in 1 child and were discordant with MRI in another one. In the 7 remaining patients, images showed cortical localization in 6 cases. Ictal SPECT is therefore faisable in very young children. Ictal-interictal subtraction SPECT images co-registered to MRI improves sensitivity compared to classical visual analysis. It seems therefore to be a helpful technique to localize the onset of seizure and to guide the intracranial recording in childhood epilepsy.

Adolescent↗
PubMed1997

Edge detection in brain SPET perfusion imaging: a comparison of several methods.

Four methods of brain edge detection on brain SPET perfusion (99Tcm-hexamethylpropylene amine oxime) images were compared: ellipse adaptation, simple thresholding (four threshold values), a low threshold (40%) followed by 1, 2 or 3 pixel erosion, and the Deriche 3D adaptive cut-off frequency method (four filter widths: alpha = 1, 2, 3 or 4). The SPET data of six patients were reconstructed to obtain 10 axial slices, each 10 mm thick, covering the whole brain. On the 60 axial slices, the methods were compared based on automaticity, computation time and accuracy of edge detection compared with morphological edges drawn manually on the patients' 3D co-registered magnetic resonance imaging (MRI) scans. The proportion of pixels inside the contour defined by the MRI scan but outside the SPET edge (p(i)), and the proportion of pixels inside the contour defined by the SPET image but outside the MRI contour (pe), were calculated. The thresholding methods provided interesting results, particularly the application of a low threshold value (40%), followed by a 2 pixel erosion, which required a computation time of 12 s (p(i) = 5.7 +/- 2.2%; pe = 2.7 +/- 0.9%). Because of adjustments to each slice of the ellipse axis, the processing time of this method was about 3 min (p(i) = 1.5 +/- 1.4%; pe = 11.3 +/- 3.4%). The Deriche 3D filter was time-consuming (6 min for 10 slices on a NXT workstation, SMV International). With this method, the best edge fitting was found with a filter width of 3 and 4 (p(i) = 9.6 +/- 11.1%; pe = 14.1 +/- 23.2%; alpha = 3). Three-dimensional filtering methods must be refined to reduce the computation time and to improve brain edge fitting accuracy when compared with the eroded thresholding method.

Brain↗
PubMed1996

Proportional anatomical stereotactic atlas for visual interpretation of brain SPET perfusion images.

A semi-automatic method was developed to determine the anterior (AC) and posterior (PC) commissures on brain single-photon emission tomographic (SPET) perfusion images, and then to draw the proportional anatomical Talairach's grid on each axial SPET image. First, the AC-PC line was defined on SPET images from the linear regression of four internal landmarks (frontal pole of the brain, inferior limit of the anterior corpus callosum, sub-thalamic point and occipital pole). Second, the SPET position of AC and PC points on the AC-PC line was automatically determined from measurements made on hard copies of magnetic resonance (MR) images of the patients. Finally, a proportional Talairach's grid was automatically drawn on each axial SPET image. To assess the accuracy of localization of AC and PC points, co-registered technetium-99m hexamethylpropylene amine oxime SPET and MR images from 11 subjects were used. The mean displacements between estimated points on SPET and true points on MRI (Deltax=sagittal, Deltay=frontal and Deltaz=axial displacement) were calculated. The mean displacements (in mm) were Deltax=-1.4+/-1.8, Deltay=-1.7+/-3.3 and Deltaz=-1. 1+/-2.5 for AC, and Deltax=-1.8+/-1.8, Deltay=0.3+/-3.2 and Deltaz=-1.3+/-2.7 for PC. These displacements represented an error of less than 5 mm at the anterior or posterior pole of the brain or at the vertex. Intra- and inter-observer comparisons did not reveal significant differences in mean displacements. Thus, this semi-automatic method results in reproducible and accurate stereotactic localization of SPET perfusion abnormalities. This method can be used routinely for repeat follow-up studies in the same subject as well as in different individuals without requiring SPET-MRI co-registration.

Algorithms↗
PubMed1996

Post-stroke changes in cortical 5-HT2 serotonergic receptors.

UNLABELLED: Fluorine-18-setoperone PET imaging was used to investigate serotonergic 5-HT2-specific binding in unlesioned cerebral cortex in stroke patients. METHODS: Seventeen stroke patients (mean age 50 +/- 31 yr) with right (n = 9) or left (n = 8) chronic stroke (middle or anterior cerebral artery territory) underwent [18F]setoperone PET and MR imaging. The distribution volume of the 5-HT2-specific binding at equilibrium (DVSe) was determined in the unlesioned cortical regions. The results were compared with those obtained in 14 age-matched controls. In addition, we investigated the effect of the side of the stroke, lesion volume and its localization. RESULTS: After removing the age effect by covariance analysis, we found a significant DVSe decrease in the temporal (p < 0.05) and frontal (p < 0.05) unlesioned cortices ipsilateral to the stroke. The changes were similar in patients with left and right stroke and did not correlate with the volume of the stroke. However, the localization of the stroke affected the topography of DVSe abnormalities. When the lesion did not extend more medially than the internal capsule, DVSe was significantly reduced in the temporal lobe (-30%, p < 0.05) but not in the frontal lobe (-21%, p = ns). Conversely, when the lesion extended subcortically in the anteromedial region, close to the midline, DVSe was reduced in both temporal (-40%, p < 0.05) and frontal (- 49%, p < 0.05) lobes. CONCLUSION: This study confirms that stroke may alter 5-HT2 receptors in large unlesioned cortical areas and that the changes depend on the subcortical extent of the lesion.

Adult↗