Sherbrooke Molecular Imaging Center

Sherbrooke, Canada

Sherbrooke Molecular Imaging Center

Sherbrooke, Canada
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Selivanova S.V.,Sherbrooke Molecular Imaging Center | Selivanova S.V.,Université de Sherbrooke | Lavallee E.,Sherbrooke Molecular Imaging Center | Senta H.,Sherbrooke Molecular Imaging Center | And 8 more authors.
Journal of Nuclear Medicine | Year: 2017

A single-site prospective open-label clinical study with cyclotronproduced sodium 99mTc-pertechnetate (99mTc-NaTcO4) was performed in patients with indications for a thyroid scan to demonstrate the clinical safety and diagnostic efficacy of the drug and to confirm its equivalence with conventional 99mTc-NaTcO4 eluted from a generator. Methods: 99mTc-NaTcO4 was produced from enriched 100Mo (99.815%) with a cyclotron (24 MeV; 2 h of irradiation) or supplied by a commercial manufacturer (bulk vial eluted from a generator). Eleven patients received 325 ± 29 (mean ± SD) MBq of the cyclotron-produced 99mTc-NaTcO4, whereas the age- and sex-matched controls received a comparable amount of the generator-derived tracer. Whole-body and thyroid planar images were obtained for each participant. In addition to the standard-energy window (140.5 keV 6 7.5%), data were acquired in lower-energy (117 keV ± 10%) and higher-energy (170 keV 6 10%) windows. Vital signs and hematologic and biochemical parameters were monitored before and after tracer administration. Results: Cyclotron-produced 99mTc-NaTcO4 showed organ and whole-body distributions identical to those of conventional 99mTc-NaTcO4 and was well tolerated. All images led to a clear final diagnosis. The fact that the number of counts in the higher-energy window was significantly higher for cyclotron-produced 99mTc-NaTcO4 did not influence image quality in the standard-energy window. Image definition in the standardenergy window with cyclotron-produced 99mTc was equivalent to that with generator-eluted 99mTc and had no particular features allowing discrimination between the 99mTc production methods. Conclusion: The systemic distribution, clinical safety, and imaging efficacy of cyclotron-produced 99mTc-NaTcO4 in humans provide supporting evidence for the use of this tracer as an equivalent for generator-eluted 99mTc-NaTcO4 in routine clinical practice. COPYRIGHT © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Leblanc E.,Université de Sherbrooke | Beaudoin J.-F.,Sherbrooke Molecular Imaging Center | Lecomte R.,Sherbrooke Molecular Imaging Center | Lecomte R.,Université de Sherbrooke | And 5 more authors.
Advances in Orthopedics | Year: 2014

Low dose microcomputed tomography (μCT) is a recently matured technique that enables the study of longitudinal bone healing and the testing of experimental treatments for bone repair. This imaging technique has been used for studying craniofacial repair in mice but not in an orthopedic context. This is mainly due to the size of the defects (approximately 1.0 mm) in long bone, which heal rapidly and may thus negatively impact the assessment of the effectiveness of experimental treatments. We developed a longitudinal low dose μCT scan analysis method combined with a new image segmentation and extraction software using Hounsfield unit (HU) scores to quantitatively monitor bone healing in small femoral cortical defects in live mice. We were able to reproducibly quantify bone healing longitudinally over time with three observers. We used high speed intramedullary reaming to prolong healing in order to circumvent the rapid healing typical of small defects. Bone healing prolongation combined with μCT imaging to study small bone defects in live mice thus shows potential as a promising tool for future preclinical research on bone healing. Copyright © 2014 Lu-Zhao Di et al.

Bergeron M.,Université de Sherbrooke | Pepin C.M.,Université de Sherbrooke | Cadorette J.,Sherbrooke Molecular Imaging Center | Beaudoin J.-F.,Sherbrooke Molecular Imaging Center | And 7 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2010

The scintillator is one of the key building blocks that critically determine the physical performance of PET detectors. The quest for scintillation crystals with improved characteristics has been crucial in designing scanners with superior imaging performance. Recently, it was shown that the decay time constant of high lutetium content Lu1.8Gd0.2SiO 5:Ce (LGSO) scintillators can be adjusted between 30 ns and 48 ns by varying the cerium concentration from 0.025 mol% to 0.75 mol%, thus providing interesting characteristics for phoswich detectors. The large light output (90-120% NaI), the better spectral match and the high initial photoelectron rate (200 phe+/ns) of these scintillators with avalanche photodiode (APD) readout promise to provide superior energy and timing resolution. Moreover, their improved mechanical properties as compared to conventional LGSO (Lu 0.2Gd1.8SiO5:Ce) make block array manufacturing readily feasible. To verify these assumptions, new phoswich block arrays made of LGSO-90%Lu with low and high mol% Ce concentrations were fabricated and assembled into LabPET modules. Typical crystal decay time constants were 32 ns and 48 ns, respectively. We therefore report on the initial evaluation of this modified version of the LabPET detector module. Phoswich crystal identification performed using a non-optimized digital pulse shape discrimination algorithm yielded an average 10% error. At 511 keV, energy resolution of 20 2% and 15 1% were obtained, while coincidence timing resolution between 4.9 0.3 ns and 4.1 0.1 ns were achieved. The improved characteristics of this new LGSO-based phoswich detector module are expected to enhance the LabPET scanner performance, first by improving sensitivity due to the overall higher stopping power of the detector module, and second by narrowing the coincidence time window, thus minimizing the random event rate. Altogether these two improvements will significantly enhance the noise equivalent count rate performance of an all LGSO-based LabPET scanner. © 2010 IEEE.

Selivanova S.V.,Sherbrooke Molecular Imaging Center | Selivanova S.V.,Université de Sherbrooke | Lavallee E.,Sherbrooke Molecular Imaging Center | Senta H.,Sherbrooke Molecular Imaging Center | And 12 more authors.
Journal of Nuclear Medicine | Year: 2015

Cyclotron production of 99mTc is a promising route to supply 99mTc radiopharmaceuticals. Higher 99mTc yields can be obtained with medium-energy cyclotrons in comparison to those dedicated to PET isotope production. To take advantage of this capability, evaluation of the radioisotopic purity of 99mTc produced at medium energy (20-24 MeV) and its impact on image quality and dosimetry was required. Methods: Thick 100Mo (99.03% and 99.815%) targets were irradiated with incident energies of 20, 22, and 24 MeV for 2 or 6 h. The targets were processed to recover an effective thickness corresponding to approximately 5-MeV energy loss, and the resulting sodium pertechnetate 99mTc was assayed for chemical, radiochemical, and radionuclidic purity. Radioisotopic content in final formulation was quantified using g-ray spectrometry. The internal radiation dose for 99mTc-pertechnetate was calculated on the basis of experimentally measured values and biokinetic data in humans. Planar and SPECT imaging were performed using thin capillary and water-filled Jaszczak phantoms. Results: Extracted sodium pertechnetate 99mTc met all provisional quality standards. The formulated solution for injection had a pH of 5.0-5.5, contained greater than 98% of radioactivity in the form of pertechnetate ion, and was stable for at least 24 h after formulation. Radioisotopic purity of 99mTc produced with 99.03% enriched 100Mo was greater than 99.0% decay corrected to the end of bombardment (EOB). The radioisotopic purity of 99mTc produced with 99.815% enriched 100Mo was 99.98% or greater (decay corrected to the EOB). The estimated dose increase relative to 99mTc without any radionuclidic impurities was below 10% for sodium pertechnetate 99mTc produced from 99.03% 100Mo if injected up to 6 h after the EOB. For 99.815% 100Mo, the increase in effective dose was less than 2% at 6 h after the EOB and less than 4% at 15 h after the EOB when the target was irradiated at an incident energy of 24 MeV. Image spatial resolution and contrast with cyclotron-produced 99mTc were equivalent to those obtained with 99mTc eluted from a conventional generator. Conclusion: Clinical-grade sodium pertechnetate 99mTc was produced with a cyclotron at medium energies. Quality control procedures and release specifications were drafted as part of a clinical trial application that received approval from Health Canada. The results of this work are intended to contribute to establishing a regulatory framework for using cyclotron-produced 99mTc in routine clinical practice. © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Paquette M.,Sherbrooke Molecular Imaging Center | Phoenix S.,Sherbrooke Molecular Imaging Center | Ouellet R.,Sherbrooke Molecular Imaging Center | Langlois R.,Sherbrooke Molecular Imaging Center | And 4 more authors.
Molecular Imaging and Biology | Year: 2013

Purpose: The aim of this study was to compare the in vivo stability, uptake, and positron emission tomography (PET) imaging performance of a novel estrogen receptor PET tracer, 4-fluoro-11β-methoxy-16α-[ 18F]fluoroestradiol (4FMFES), with 16α-[18F] fluoroestradiol (FES). Procedures: MC7-L1 and MC4-L2 (ER+) cell lines and their ERα-knockdown variants (ERαKD) were implanted subcutaneously in Balb/c mice. After 21 days, mice were imaged using either FES or 4FMFES. One hour post-injection, static images were acquired for 30 min and the tumor %ID/g uptake values were derived. Biodistribution data were also obtained 1 h following the injection of either FES or 4FMFES. Blood samples were taken at different times and analyzed on thin-layer chromatography to quantify the presence of radiometabolites for each radiotracer. To assess specific targeting to the estrogen receptors, mice bearing only ER+ tumors were treated with the competitive ER inhibitor fulvestrant 48 h prior to imaging with 4FMFES. Results: Metabolic stability was found to be similar for both tracers in mice. Both FES and 4FMFES differentiated ER+ tumors from ERαKD tumors in biodistribution and PET imaging studies. 4FMFES achieved a significantly higher %ID/g uptake in ER+ tumors and MC4-L2 ERαKD tumors than FES in the PET imaging studies. Also, tumor-to-background ratio was higher in ER+ tumors using 4FMFES compared to FES. Dissection data showed a significantly higher %ID/g in all tested cell lines and ER-rich tissues using 4FMFES versus FES. Fulvestrant-treated mice had either low or undetectable tumor uptake. Conclusion: In a tumor-bearing mouse model, 4FMFES achieves better specific tumor uptake and better contrast than FES, making it a promising candidate for ER imaging. © 2013 World Molecular Imaging Society.

Roy M.,Research Center on Aging | Roy M.,Université de Sherbrooke | Nugent S.,Research Center on Aging | Nugent S.,Université de Sherbrooke | And 15 more authors.
Brain Research | Year: 2012

Despite decades of study, it is still unclear whether regional brain glucose uptake is lower in the cognitively healthy elderly. Whether regional brain uptake of ketones (β-hydroxybutyrate and acetoacetate [AcAc]), the main alternative brain fuel to glucose, changes with age is unknown. We used a sequential, dual tracer positron emission tomography (PET) protocol to quantify brain 18F-fluorodeoxyglucose (18F-FDG) and 11C-AcAc uptake in two studies with healthy, male Sprague-Dawley rats: (i) Aged (21 months; 21M) versus young (4 months; 4M) rats, and (ii) The effect of a 14 day high-fat ketogenic diet (KD) on brain 18F-FDG and 11C-AcAc uptake in 24 month old rats (24M). Similar whole brain volumes assessed by magnetic resonance imaging, were observed in aged 21M versus 4M rats, but the lateral ventricles were 30 larger in the 21M rats (p=0.001). Whole brain cerebral metabolic rates of AcAc (CMRAcAc) and glucose (CMRglc) did not differ between 21M and 4M rats, but were 28 and 44 higher, respectively, in 24M-KD compared to 24M rats. The region-to-whole brain ratio of CMRglc was 37-41 lower in the cortex and 40-45 lower in the cerebellum compared to CMRAcAc in 4M and 21M rats. We conclude that a quantitative measure of uptake of the brain's two principal exogenous fuels was generally similar in healthy aged and young rats, that the of distribution across brain regions differed between ketones and glucose, and that brain uptake of both fuels was stimulated by mild, experimental ketonemia. © 2012 Elsevier B.V.

Michaud J.-B.,Université de Sherbrooke | Tetrault M.-A.,Université de Sherbrooke | Beaudoin J.-F.,Université de Sherbrooke | Beaudoin J.-F.,Sherbrooke Molecular Imaging Center | And 7 more authors.
IEEE Transactions on Nuclear Science | Year: 2015

Scanner sensitivity is often critical in high-resolution Positron Emission Tomography (PET) dedicated to molecular imaging. In neighboring pixelated detectors with individual readout, sensitivity decreases because of multiple coincidences produced by Compton scattering. Correct analysis of those coincidences would enable a substantial sensitivity increase. However, including scattering byproducts in the image often lead to image quality degradation because of inaccurate Line-of-Response (LOR) assessment. In such scanners, to support high count rates, multiple coincidences are usually discarded when image degradation is not acceptable, or blindly accepted for a low computational burden. This paper presents a new, real-time capable method that includes Inter-Crystal Scatter (ICS) triple coincidences in the image without significant quality degradation. The method computes the LOR using a neural network fed by preprocessed raw data. As a proof of principle, this paper analyzes the simplest ICS scenario, triple coincidences where one photoelectric 511-keV event coincides with two more whose energy sum is also 511 keV. The paper visits the algorithm structure, presents Monte Carlo assessment with the LabPET model, and displays images reconstructed from real data. With an energy window of 360-660 keV and a singles energy threshold of 125 keV, the inclusion of triple coincidences yielded a sensitivity increase of 54%, a resolution degradation similar to that of other sensitivity-increasing methods, and only a slight contrast degradation for real LabPET data, with potential for numerous further improvements. © 2014 IEEE.

Nugent S.,Université de Sherbrooke | Croteau E.,Université de Sherbrooke | Croteau E.,Sherbrooke Molecular Imaging Center | Pifferi F.,Université de Sherbrooke | And 6 more authors.
Prostaglandins Leukotrienes and Essential Fatty Acids | Year: 2011

Cerebral metabolic rate of glucose (CMRg) is lower in individuals affected by cognitive decline and dementia, especially in Alzheimer's disease. However, as yet there is no consensus as to whether CMRg decreases during healthy aging. Epidemiological studies show that weekly consumption of fish abundant in ω3 fatty acids has a protective effect on cognition during aging. Thus, the primary objective of this human study was to use positron emission tomography analysis with 18F-fluorodeoxyglucose to evaluate whether supplementation with a fish oil rich in ω3 fatty acids increases cerebral glucose metabolism in young or elderly adults. Healthy young (23±5y old; n=5) and elderly (76±3y old; n=6) women and men were included in the study. Semi-quantitative expression of the data as 'standardized uptake values' showed that elderly participants had significantly lower cerebral glucose metabolism compared with the young group. However, when expressed quantitatively a CMRg, there was no effect of age or ω3 supplementation on glucose metabolism in any of the brains regions studied. Higher plasma triglyceride levels and higher plasma insulin levels were associated with lower CMRg in several regions, suggesting that a trend towards the metabolic syndrome may be associated with cerebral hypometabolism. We conclude that under these experimental conditions, ω3 supplementation did not affect brain glucose metabolism in the healthy elderly. Future studies in this area should address whether glucose intolerance or other conditions linked to the metabolic syndrome impact negatively on brain glucose metabolism and cognition. © 2011 Elsevier Ltd.

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