Browsing by Author "Roselt, P"
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- Item[18F]-Flumazenil: a γ-aminobutyric acid A–specific PET radiotracer for the localisation of drug resistant temporal lobe epilepsy(Society of Nuclear Medicine and Molecular Imaging, 2013-07-15) Vivash, L; Grégoire, MC; Lau, EW; Ware, RE; Binns, D; Roselt, P; Bouilleret, V; Myers, DE; Cook, MJ; Hicks, RJ; O’Brien, TJStudies report that 11C-flumazenil (FMZ) PET more specifically localizes the epileptogenic zone in patients with medically refractory focal epilepsy than 18F-FDG PET. However, practical aspects of 11C use limit clinical application. We report a phase I/IIa study assessing the clinical use of 18F-FMZ PET for the localization of the epileptogenic zone in patients with drug-resistant temporal lobe epilepsy (TLE). Receptor binding was quantified using kinetic modeling that did not require arterial sampling. Methods: Dynamic 18F-FMZ PET and static interictal 18F-FDG PET scans were compared in healthy controls (n = 17 for 18F-FMZ and n = 20 for 18F-FDG) and TLE patients with mesial temporal sclerosis on MR imaging (MTS, n = 12) and with normal MR imaging (NL TLE, n = 19). Masked visual assessment of images was undertaken. Parametric images of 18F-FMZ binding potential (BPND) were generated using the simplified reference tissue model. Region-of-interest analysis on coregistered MR images and statistical parametric mapping were used to quantify 18F-FMZ BPND and 18F-FDG uptake in the temporal lobe. Results: The visual assessment of static standardized uptake value images showed 18F-FMZ PET to have high specificity (16/17 [94%]) and moderate sensitivity (21/31 [68%]) for the localization of the epileptogenic zone, with a more restricted abnormality than 18F-FDG PET. However, the 18F-FMZ standardized uptake value images were falsely localizing in 3 of 31 patients (10%). Region-of-interest analysis demonstrated reductions in ipsilateral hippocampal 18F-FMZ BPND in patients with either MTS or NL TLE, compared with controls subjects. Ipsilateral hippocampal 18F-FMZ BPND was independent of both hippocampal volume and 18F-FDG uptake, whereas ipsilateral hippocampal volume was correlated with 18F-FDG uptake (r2 = 0.69, P < 0.0001). Statistical parametric mapping analysis demonstrated decreased uptake in 14 of 31 (45%) cases with 18F-FMZ PET and 18 of 29 (62%) with 18F-FDG PET. Cluster size was significantly smaller on 18F-FMZ than 18F-FDG images (37 vs. 160 voxels, P < 0.01). Conclusion: 18F-FMZ PET has potential as a clinical tool for the localization of the epileptogenic zone in the presurgical evaluation of drug-resistant TLE, providing information complementary to 18F-FDG PET, with a more restricted region of abnormality. © 2013 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
- ItemDevelopment of [18F]-Flumazenil-PET for localisation of the epileptogenic zone in patients with medically refractory focal epilepsy(Springer, 2010-10-11) Vivash, L; Grégoire, MC; Dedeurwaerdere, S; Bouilleret, V; Roselt, P; Lau, EW; Ware, RE; Binns, D; Katsifis, A; Hicks, RJ; Myers, DE; O'Brien, TJIntroduction: Studies of GABAA/central benzodiazepine receptor (GABAA/cBZR) distribution in the CNS using [11C]-flumazenil-PET (FMZ-PET) have enabled localisation of the epileptogenic zone (EZ) in patients with medically refractory epilepsy. [11C]-FMZ-PET images show a more restricted region of abnormality with increased sensitivity when compared with FDG-PET. However, use of [11C]-FMZ in routine clinical practice has been hindered by practical limitations of [11C]. The aim of the current study is to develop an [18F]-radiolabelled FMZ tracer with high specificity and improved imaging quality for EZ localisation in routine clinical practice. Methods: Preclinical studies: Presaturation, displacementand uptake PET scans were performed to define the kinetics of [18F]-FMZ binding in non-epileptic rats (n=8). Bmax (receptor density) and KD (binding affinity) were then quantified in the brains of epileptic (n=9; kainic acid-induced model of temporal lobe epilepsy) vs. non-epileptic control animals (n=10). Clinical study: 4 patient groups have been studied; healthy controls (n=20), patients with well-localised TLE from MRI scans (n=10), patients with lateralised TLE(n=7), and patients with other focal epilepsies (n=4). Each participant underwent a single 60 minute dynamic [18F]-FMZ-PET scan. Patients also underwent an FDG-PET scan. Blinded visual assessment of images to locate the EZ was performed. Parametric images of binding potential (BP) were generated. Datasets were processed using ROI analysis and SPM to assess differences in BP between patients and controls and localisation of the EZ in patients. Results:[18F]-FMZ was shown to be a suitable PET radiotracer for imaging GABAA/cBZR in vivo, with reversible and competitive binding and low non-specific binding. [18F]-FMZ-PET reliably detected decreased Bmax in the hippocampi of epilepticrats (left 16.3, right 15.9) compared with controls (left 20.9, right 19.8, p=0.022, p=0.049), with no change in KD (left 8.24 vs 8.46, p=0.82, right 7.43vs 8.07 p=0.56). There were no changes in whole brain Bmax or KD. To date the visual assessment of the clinical data has shown [18F]-FMZ-PET to have high sensitivity (100%) and positive predictive value (100%) for the EZ in patients, with a more restricted localisation of the EZ compared to FDG-PET. Quantitative analysis is ongoing. Conclusions: The pre-clinical studies have demonstrated that [18F]-FMZ-PET is a reliable radiotracer for quantification of CNSGABAA/cBZR expression in vivo. Preliminary analysis in our current clinical study indicates that [18F]-FMZ-PET also has excellent imaging characteristics in humans, and shows promise as a new clinical tool for localising the EZ in TLE patients. © 2020 Springer Nature Switzerland AG
- ItemDiscovery of [F-18]N-(2-(Diethylamino)ethyl)-6-fluoronicotinamide: a melanoma positron emission tomography imaging radiotracer with high tumor to body contrast ratio and rapid renal clearance(American Chemical Society, 2009-09-10) Greguric, I; Taylor, SR; Denoyer, D; Ballantyne, P; Berghofer, PJ; Roselt, P; Pham, TQ; Mattner, F; Bourdier, T; Neels, OC; Dorow, DS; Loc'h, C; Hicks, RJ; Katsifis, AThe high melanoma uptake and rapid body clearance displayed by our series of [123I]iodonicotinamides prompted the development of [18F]N-(2-(diethylamino)ethyl)-6-fluoronicotinamide ([18F]2), a novel radiotracer for PET melanoma imaging. Significantly, unlike fluorobenzoates, [18F]fluorine incorporation on the nicotinamide ring is one step, facile, and high yielding. [18F]2 displayed high tumor uptake, rapid body clearance via predominantly renal excretion, and is currently being evaluated in preclinical studies for progression into clinical trials to assess the responsiveness of therapeutic agents. © 2009, American Chemical Society
- ItemFully automated one-pot radiosynthesis of O-(2-[18F]fluoroethyl)-L-tyrosine on the TracerLab FXFN module(Elsevier B.V., 2011-07-01) Bourdier, T; Greguric, I; Roselt, P; Jackson, TW; Faragalla, J; Katsifis, AIntroduction: An efficient fully automated method for the radiosynthesis of enantiomerically pure O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) using the GE TracerLab FXFN synthesis module via the O-(2-tosyloxyethyl)-N-trityl-L-tyrosine tert-butylester precursor has been developed. Methods: The radiolabelling of [18F]FET involved a classical [18F]fluoride nucleophilic substitution performed in acetonitrile using potassium carbonate and Kryptofix 222, followed by acid hydrolysis using 2N hydrochloric acid. Results: [18F]FET was produced in 35±5% (n=22) yield non-decay-corrected (55±5% decay-corrected) and with radiochemical and enantiomeric purity of >99% with a specific activity of >90 GBq/μmol after 63 min of radiosynthesis including HPLC purification and formulation. Conclusion: The automated radiosynthesis provides high and reproducible yields suitable for routine clinical use. © 2011 Elsevier Inc.
- ItemHigh-contrast PET of melanoma using F-18-MEL050, a selective probe for melanin with predominantly renal clearance(Society of Nuclear Medicine, 2010-03) Denoyer, D; Greguric, I; Roselt, P; Neels, OC; Aide, N; Taylor, SR; Katsifis, A; Dorow, DS; Hicks, RJThe aim of this study was to evaluate the novel probe 18F-6-fluoro-N-[2-(diethylamino)ethyl] pyridine-3-carboxamide (18F-MEL050) for the imaging of primary and metastatic melanoma. Methods: PET using 18F-MEL050 was performed in murine models of melanoma. The specificity of 18F-MEL050 was studied by comparing its accumulation in pigmented B16-F0 allograft tumors with that of human amelanotic A375 xenografts using PET and high-resolution autoradiography. 18F-MEL050 PET results were compared with 18F-FDG PET, the current standard in melanoma molecular imaging. To test the ability of 18F-MEL050 to assess the metastatic spread of melanoma, a murine model of lung metastasis was imaged by PET/CT, and results correlated with physical assessment of tumor burden in the lungs. Results: In pigmented B16-F0 grafts, 18F-MEL050 PET yielded a tumor-to-background ratio of approximately 20:1 at 1 h and greater than 50:1 at 2 and 3 h. In the B16-F0 melanoma allograft model, tumor-to-background ratio was more than 9-fold higher for 18F-MEL050 than for 18F-FDG (50.9 ± 6.9 vs. 5.8 ± 0.5). No uptake was observed in the amelanotic melanoma xenografts. Intense uptake of 18F-MEL050 was evident in metastatic lesions in the lungs of B16-BL6 tumor–bearing mice on PET at 2 h after tracer injection, with high concordance between 18F-MEL050 accumulation on PET/CT and tumor burden determined at necroscopy. Conclusion: 18F-MEL050 has a rapid tumor uptake and high retention with specificity for melanin, suggesting great potential for noninvasive clinical evaluation of suspected metastatic melanoma. © 2010, Society of Nuclear Medicine
- ItemImaging of tumor hypoxia with [124I]IAZA in comparison with [18F]FMISO and [18F]FAZA – first small animal PET results(Canadian Society for Pharmaceutical Sciences, 2007-06-14) Reischl, G; Dorow, D; Cullinane, C; Katsifis, A; Roselt, P; Binns, D; Hicks, RJPURPOSE: This study was performed to compare the 2-nitroimidazole derivatives [124I]IAZA, [18F]FAZA and well known [18F]FMISO in visualization of tumor hypoxia in a mouse model of human cancer using small animal PET. METHODS: PET imaging of female Balb/c nude mice bearing A431 tumors on a Phillips Mosaic small animal PET scanner was performed 3 h p.i. for all three tracers. Mice injected with [124I]IAZA were scanned again after 24 h and 48 h. In addition to the mice breathing air, in the case of [18F]FAZA and [124I]IAZA a second group of mice for each tracer was kept in an atmosphere of carbogen gas (5% of CO2 + 95 % of O2; from 1 h before to 3 h after injection) to evaluate the oxygenation dependency on uptake (all experiments n = 4). After the final PET scan animals were sacrificed and biodistribution was studied. RESULTS: Mice injected with [18F]FAZA displayed significantly higher tumor-to background (T/B) ratios (5.19 +/- 0.73) compared to those injected with [18F]FMISO (3.98 +/- 0.66; P $lt; 0.05) or [124I]IAZA (2.06 +/- 0.26; P $lt; 0.001) 3 h p.i. Carbogen breathing mice showed lower ratios ([18F]FAZA: 4.06 +/- 0.59; [124I]IAZA: 2.02 +/- 0.36). The T/B ratios increased for [124I]IAZA with time (24 h: 3.83 +/- 0.61; 48 h: 4.20 +/- 0.80), but after these late time points the absolute whole body activity was very low, as could be seen from the biodistribution data (< 0.1 %ID/g for each investigated organ) and ratios were still lower than for [18F]FAZA 3 h p.i. Due to de-iodination uptake in thyroid was high. Biodistribution data were in good agreement with the PET results. CONCLUSIONS: [18F]FAZA showed superior biokinetics compared to [18F]FMISO and [124I]IAZA in this study. Imaging at later time points that are not possible with the short lived 18F labeled tracers resulted in no advantage for [124I]IAZA, i. e. tumor to normal tissue ratios could not be improved. © 1999 Canadian Society for Pharmaceutical Sciences.
- ItemImproved detection of regional melanoma metastasis using 18F-6-Fluoro-N-[2-(Diethylamino)Ethyl] Pyridine-3-Carboxamide, a Melanin-specific PET probe, by perilesional administration(Society of Nuclear Medicine, 2011-01-01) Denoyer, D; Potdevin, T; Roselt, P; Neels, OC; Kirby, L; Greguric, I; Katsifis, A; Dorow, DS; Hicks, RJThe efficacy of differing routes of administration of 18F-6-fluoro-N-[2-(diethylamino)ethyl] pyridine-3-carboxamide (18F-MEL050), a new benzamide-based PET radiotracer for imaging regional lymph node metastasis in melanoma, was assessed. Methods: B16-Black/6 metastatic melanoma cells harboring an mCherry transgene were implanted into the left-upper-foot surface of 49 C57 Black/6 mice as a model of popliteal lymph node (PLN) metastasis. Ultrasound scanning of the left PLN was performed at baseline and in combination with 18F-MEL050 PET on days 5, 9, and 14. Mice were divided into 2 groups to compare the results of tracer administration either subcutaneously at the tumor site (local) or in the lateral tail vein (systemic). After PET on each imaging day, 5 mice per group—including any with evidence of metastasis—were sacrificed for ex vivo validation studies including assessment of retained radioactivity and presence of the mCherry transgene as a surrogate of nodal tumor burden. Results: Nine mice were judged as positive for PLN metastasis by ultrasound at day 5, and 8 PLNs were positive on 18F-MEL050 PET, 3 after systemic and 5 after local administration. Ex vivo analysis showed that ultrasound correctly identified 90% of positive PLNs, with 1 false-positive. 18F-MEL050 PET correctly identified 60% of positive PLNs after systemic administration and 100% after local administration with no false-positive results by either route. The average node-to-background ratio for positive PLNs was 6.8 in the systemic-administration group and correlated with disease burden. In the local-administration group, the mean uptake ratio was 48, without clear relation to metastatic burden. Additional sites of metastatic disease were also correctly identified by 18F-MEL050 PET. Conclusion: In addition to its potential for systemic staging, perilesional administration of 18F-MEL050 may allow sensitive and specific, noninvasive identification of regional lymph node metastasis in pigmented malignant melanomas. © 2011, Society of Nuclear Medicine
- ItemIn vivo measurement of hippocampal GABAA/cBZR density with [18F]-Flumazenil PET for the study of disease progression in an animal model of temporal lobe epilepsy(Public Library of Science, 2014-01-21) Vivash, L; Grégoire, MC; Bouilleret, V; Berard, A; Wimberley, CA; Binns, D; Roselt, P; Katsifis, A; Myers, DE; Hicks, RJ; O'Brien, TJ; Dedeurwaerdere, SPurpose Imbalance of inhibitory GABAergic neurotransmission has been proposed to play a role in the pathogenesis of temporal lobe epilepsy (TLE). This study aimed to investigate whether [18F]-flumazenil ([18F]-FMZ) PET could be used to non-invasively characterise GABAA/central benzodiazepine receptor (GABAA/cBZR) density and affinity in vivo in the post-kainic acid status epilepticus (SE) model of TLE. Methods Dynamic [18F]-FMZ -PET scans using a multi-injection protocol were acquired in four male wistar rats for validation of the partial saturation model (PSM). SE was induced in eight male Wistar rats (10 weeks of age) by i.p. injection of kainic acid (7.5–25 mg/kg), while control rats (n = 7) received saline injections. Five weeks post-SE, an anatomic MRI scan was acquired and the following week an [18F]-FMZ PET scan (3.6–4.6 nmol). The PET data was co-registered to the MRI and regions of interest drawn on the MRI for selected structures. A PSM was used to derive receptor density and apparent affinity from the [18F]-FMZ PET data. Key Findings The PSM was found to adequately model [18F]-FMZ binding in vivo. There was a significant decrease in hippocampal receptor density in the SE group (p<0.01), accompanied by an increase in apparent affinity (p<0.05) compared to controls. No change in cortical receptor binding was observed. Hippocampal volume reduction and cell loss was only seen in a subset of animals. Histological assessment of hippocampal cell loss was significantly correlated with hippocampal volume measured by MRI (p<0.05), but did not correlate with [18F]-FMZ binding. Significance Alterations to hippocampal GABAA/cBZR density and affinity in the post-kainic acid SE model of TLE are detectable in vivo with [18F]-FMZ PET and a PSM. These changes are independent from hippocampal cell and volume loss. [18F]-FMZ PET is useful for investigating the role that changes GABAA/cBZR density and binding affinity play in the pathogenesis of TLE. © 2014 Vivash et al.
- ItemIn-vivo imaging characteristics of two fluorinated flumazenil radiotracers in the rat(Springer, 2009-06) Dedeurwaerdere, S; Grégoire, MC; Vivash, L; Roselt, P; Binns, D; Fookes, CJR; Greguric, I; Pham, TQ; Loc'h, C; Katsifis, A; Hicks, RJ; O'Brien, TJ; Myers, DEPurpose: [11C]Flumazenil shows promise as a clinical and research PET radiotracer to image changes in GABAA central benzodiazepine receptor (cBZR), but its widespread use has been limited by practical limitations of [11C]. This study evaluated the imaging characteristics of two fluorinated PET radiotracers in rats in vivo: [18F]fluoroflumazenil ([18F]FFMZ) and [18F]flumazenil ([18F]FMZ). Methods: PET acquisitions were performed on a small-animal scanner following injection of [18F]FFMZ in nine rats and [18F]FMZ in eight rats. The following treatments were investigated: (1) injection of the tracer dose, (2) presaturation then injection of the tracer dose, and (3) injection of the tracer dose followed by a displacement injection. Unchanged tracer was measured in plasma and brain structures in four animals 10 and 30 min after injection, and ex-vivo autoradiography was also performed. Results: For both [18F]FFMZ and [18F]FMZ maximal brain activity peaked rapidly, and was highest in the hippocampus (1.12±0.06 SUV, 1.24±0.10 SUV, respectively), and lowest in the pons (1.00±0.07 SUV, 1.03±0.09 SUV, respectively). By 50 min after injection, maximal uptake for [18F]FFMZ and [18F]FMZ had decreased in the hippocampus to 18±3% and 80±1% (p<0.01), respectively. The presaturation and displacement studies showed a higher nonspecific component for [18F]FFMZ than for [18F]FMZ. Metabolite studies showed that at 30 min only 10% of the signal was from [18F]FFMZ in the brain. This nonspecific binding was apparent on autoradiography. In contrast, [18F]FMZ accounted for >70% of the signal in the brain, which resulted in well-defined regional binding on autoradiography. Conclusion These results demonstrate that [18F]FMZ is a superior radiotracer to [18F]FFMZ for in-vivo PET imaging of the GABAA/cBZR, having slower metabolism and leading to lower concentrations of metabolites in the brain that results in a substantially better signal-to-noise ratio. © 2009, Springer.
- ItemPreclinical characterization of 18FD-FPHCys, a new amino acid-based PET tracer(Springer, 2012-04-01) Denoyer, D; Kirby, L; Waldeck, K; Roselt, P; Neels, OC; Bourdier, T; Shepherd, R; Katsifis, A; Hicks, RJThe imaging potential of a new F-18-labelled methionine derivative, S-(3-[F-18]fluoropropyl)-d-homocysteine (F-18-D-FPHCys), and its selectivity for amino acid transporter subtypes were investigated in vitro and by imaging of human tumour xenografts. Expression of members of the system L (LAT isoforms 1-4 and 4F2hc) and ASCT (ASCT isoforms 1 and 2) amino acid transporter subclasses were assessed by quantitative real-time PCR in four human tumour models, including A431 squamous cell carcinoma, PC3 prostate cancer, and Colo 205 and HT-29 colorectal cancer lines. The first investigations for the characterization of F-18-D-FPHCys were in vitro uptake studies by comparing it with [1-C-14]-l-methionine (C-14-MET) and in vivo by PET imaging. In addition, the specific involvement of LAT1 transporters in F-18-D-FPHCys accumulation was tested by silencing LAT1 mRNA transcription with siRNAs. To determine the proliferative activity in tumour xenografts ex vivo, Ki-67 staining was used as a biomarker. A431 cells showed the highest F-18-D-FPHCys uptake in vitro and in vivo followed by Colo 205, PC3 and HT-29. A similar pattern of retention was observed with C-14-MET. F-18-D-FPHCys retention was strongly correlated with LAT1 expression both in vitro (R (2) = 0.85) and in vivo (R (2) = 0.99). Downregulation of LAT1 by siRNA inhibited F-18-D-FPHCys uptake, demonstrating a clear dependence on this transporter for tumour uptake. Furthermore, F-18-D-FPHCys accumulation mirrored cellular proliferation. The favourable properties of F-18-D-FPHCys make this tracer a promising imaging probe for detection of tumours as well as for the noninvasive evaluation and monitoring of tumour growth.© 2012, Springer.
- ItemRadiosynthesis of a novel PET fluoronicotinamide for melanoma tumour PET imaging [18F]MEL050(CSIRO Publishing, 2011-01-01) Greguric, I; Taylor, S; Pham, TQ; Wyatt, NA; Jiang, CD; Bourdier, T; Loc'h, C; Roselt, P; Neels, OC; Katsifis, A[18F]6-Fluoro-N-[2-(diethylamino)ethyl]nicotinamide [18F]MEL050 is a novel nicotinamide-based radiotracer, designed to target random metastatic dissemination of melanoma tumours by targeting melanin. Preclinical studies suggest that [18F]MEL050 has an excellent potential to improve diagnosis and staging of melanoma. Here we report the radiochemical optimization conditions of [18F]MEL050 and its large scale automated synthesis using a GE FXFN automated radiosynthesis module for clinical, phase-1 investigation. [18F]MEL050 was prepared via a one-step synthesis using no-carrier added K[18F]F-Krytpofix® 222 (DMSO, 170°C, 5 min) followed by HPLC purification. Using 6-chloro-N-[2-(diethylamino)ethyl]nicotinamide as precursor, [18F]MEL050 was obtained in 40–46% radiochemical yield (non-decay corrected), in greater than 99.9% radiochemical purity and specific activity ranging from 240 to 325 GBq μmol–1. Total synthesis time including formulation was 40 min and [18F]MEL050 was stable (99.8%) in PBS for 6 h. © 2011, CSIRO Publishing
- ItemSynthesis and radiosynthesis of a novel PET fluorobenzyl piperazine for melanoma tumour imaging; [18F]MEL054(CSIRO publishing, 2012-02-18) Taylor, SR; Roberts, MR; Wyatt, NA; Pham, TQ; Stark, D; Bourdier, T; Roselt, P; Katsifis, A; Greguric, I2-{2-[4-(4-[18F]-Fluorobenzyl)piperazin-1-yl]-2-oxoethyl}isoindolin-1-one ([18F]MEL054), is a new potent indolinone-based melanin binder designed to target melanotic tumours. [18F]MEL054 was prepared by an automated two-step radiosynthesis, comprising of the preparation of 4-[18F]fluorobenzaldehyde from 4-formyl-N,N,N-trimethylanilinium triflate, followed by reductive alkylation with 2-(2-oxo-2-piperazin-1-ylethyl)isoindolin-1-one. 4-[18F]Fluorobenzaldehyde was prepared on a GE TRACERlab FXFN module in 68 ± 8 % radiochemical yield (RCY, non-decay corrected), purified by a Sep-Pak Plus C18 cartridge and eluted into the reactor of an in-house modified Nuclear Interface [18F]FDG synthesis module for the subsequent reductive alkylation reaction. HPLC purification produced [18F]MEL054 in a collected RCY of 34 ± 9 % (non-decay corrected), the total preparation time (including Sep-Pak Plus C18 and HPLC purification) did not exceed 105 min. The radiochemical purity of [18F]MEL054 was greater than 99 % with a specific radioactivity of 71–119 GBq μmol–1 and [18F]MEL054 remained stable in saline solution (>98 %) after 3 h. © 2013 CSIRO.