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By adapting previously reported reaction conditions, [18 F]FMISO was synthesized using a TracerLab FX-FDG module in 31 min from no carrier added [18 F]fluoride in 56% radiochemical yield. A novel and simple purification setup based on disposable cartridges was developed allowing the radiopharmaceutical to be obtained in high radiochemical purity (>99.5%) and with chemical impurities far below the Ph.Eur.'s thresholds. Moreover, the study pinpointed some shortcomings of the high-performance liquid chromatography (HPLC) method reported in the dedicated Ph.Eur's monograph.

By adapting previously reported reaction conditions, [

Introduction O-(2-[18F]Fluoroethyl)-L-tyrosine ([18F]FET) is an established radiotracer used for oncology investigations by Positron Emission Tomography (PET). Main limitations to its widespread use are the synthesis itself (time; cost; radiochemical yield; complexity) and a troublesome and time-consuming HPLC purification. Aim of this work was to improve the preparation overall efficiency and, most important, to achieve an efficient and reliable purification by means of disposable cartridges. Methods [18F]FET was synthesized by direct nucleophilic radiofluorination of O-(2-tosyloxy-ethyl)-N-trityl-L-tyrosine t-butylester (TET) followed by acid hydrolysis with HCl. Several conditions and materials were tested for the synthesis and purification step. For the latter, a number of different commercial cartridges, varying in amount, particulate size and adsorbent, were examined. Best results were obtained by a combination of STRATA-X, tC18 and QMA cartridges. Results Starting from only 5 mg of TET, up to 11 GBq of injectable solutions of [18F]FET were produced within 36 min with 54–65% radiochemical yields and radiochemical purities >99%. No D-form was observed by chiral HPLC. Chemical purity was 1–2 order of magnitude below the limits imposed by the European Pharmacopoeia's monograph on [18F]FET. A radiochemical purity decrease by radiolysis, observed only on relatively large batches of [18F]FET, was efficiently suppressed by preloading in the receiving final vial a small amount of ethanol ( Conclusions By combining improvements to a known synthetic route with a novel cartridge-based purification, [18F]FET was obtained in a very efficient and reproducible way. The whole process was easily implemented on a commercial automated module presently used for [18F]FDG production. Advances in knowledge and implications for patient care A few drawbacks regarding the HPLC conditions recommended in the European Pharmacopoeia were highlighted. An alternative method able to cope with them is herein proposed The simplified preparation herein described is expected to encourage a more widespread clinical use of [18F]FET.

When applied to a radiosynthesis, a microscale approach can help to save precursor and improve yields. Thus, a 5-10 μL microscale method based on a concentration procedure was developed and applied to the radiosynthesis of [

High specific activity is often a significant requirement for radiopharmaceuticals. To achieve that with fluorine-18 (18 F)-labeled probes, it is mandatory to start from no-carrier-added fluoride and to reduce to a minimum the amount of precursor in order to decrease the presence of any pseudocarrier. In the present study, a feasible and efficient method for microscale one-pot radiosynthesis of 18 F-labeled probes is described. It allows a substantial reduction in precursor, solvent, and reagents, thus reducing also possible side reaction in the case of base-sensitive precursors. The method is based on the use of a small amount of Kryptofix 2.2.2/potassium [18 F]fluoride in MeOH (K.222/K[18 F]F-MeOH) obtained using Oasis MAX and MCX cartridges. Five methods, differing in terms of MeOH evaporation and precursor addition, for the radiosynthesis of [18 F]fallypride and [18 F]FET in ≤50-μL scale, were examined and evaluated. The method using the addition of DMSO to the K.222/K[18 F]F-MeOH solution prior to MeOH evaporation is proposed as a versatile procedure for feasible one-pot 10- to 20-μL scale radiosyntheses. This method was successfully applied also to the radiosynthesis of [18 F]FES, [18 F]FLT, and [18 F]FMISO, with radiochemical yields comparable with those reported in the literature. Purification of a crude product by an analytical HPLC column was also demonstrated.

Conversion of aqueous [18F]fluoride to reactive [18F]fluoride is an important first step in the radiosynthesis of 18F-labeled compounds by nucleophilic substitution. A versatile method for the rapid preparation of reactive [18F]fluoride by the combined use of an Oasis MAX cartridge and a methanolic solution of the Kryptofix 222-KHCO3 complex (K.222/KHCO3) was developed. The latter amount was optimized with the aim to keep it as low as possible while achieving recovery yields of [18F]fluoride comparable to those attained with the commonly used QMA cartridge. Thus, a 97% recovery yield was obtained with just 2µmol of K.222/KHCO3 methanolic solution (10mM, 200µL) within 7min. This result allowed in turn to optimize the microscale radiosynthesis of [18F]FDG. Moreover, the method was successfully applied to the 100µL-scale 18F-substitution reactions of several precursors.

Tetrabutylammonium is a phase-transfer agent commonly used in PET radiochemistry. Its toxicity makes its quantification mandatory. However, the official HPLC method for tetrabutylammonium analysis reported in the European Pharmacopoeia (Ph. Eur.) apparently fails to achieve the described separation in most new generation reverse-phase columns. The study highlights the differences in separation achievable by varying some of the chromatographic conditions, such as temperature, eluent composition and ion-pairing agent concentration. In the end, variations to the method within the limits allowed by the Ph. Eur. were not sufficient to overcome the problem, thus forcing to a more radical change of the organic component of the mobile phase.

When applied to a radiosynthesis, a microscale approach can help to save precursor and improve yields. Thus, a 5–10 μL microscale method based on a concentration procedure was developed and applied to the radiosynthesis of [18F]FET and [18F]fallypride. In spite of using an amount of precursor ca. 100 times smaller, radiochemical yields were comparable or even higher than those reported in literature. Because of the very low reaction volumes, the possible effects of concentrated dose of activity and carrier fluoride were also investigated.

Rationale Pathological response to neo-adjuvant chemotherapy (NAC) represents a commonly used predictor of survival in triple negative breast cancer (TNBC) and the need to identify markers that predict response to NAC is constantly increasing. Aim of this study was to evaluate the potential usefulness of PET imaging with [18F]FDG and [18F]FLT for the discrimination of TNBC responders to Paclitaxel (PTX) therapy compared to the response assessed by an adapted Response Evaluation Criteria In Solid Tumors (RECIST) criteria based on tumor volume (Tumor Volume Response). Methods Nu/nu mice bearing TNBC lesions of different size were evaluated with [18F]FDG and [18F]FLT PET before and after PTX treatment. SUVmax, Metabolic Tumor Volume (MTV) and Total Lesion Glycolysis (TLG) and Proliferation (TLP) were assessed using a graph-based random walk algorithm. Results We found that in our TNBC model the variation of [18F]FDG and [18F]FLT SUVmax similarly defined tumor response to therapy and that SUVmax variation represented the most accurate parameter. Response evaluation using Tumor Volume Response (TVR) showed that the effectiveness of NAC with PTX was completely independent from lesions size at baseline. Conclusions Our study provided interesting results in terms of sensitivity and specificity of PET in TNBC, revealing the similar performances of [18F]FDG and [18F]FLT in the identification of responders to Paclitaxel.

Microspheres of the proper size injected into the hepatic artery lodge themselves preferentially in and around tumours as a result of both the increased vascularity of tumours and the fact that blood from the hepatic artery flows preferentially to malignancies. Thus, radioembolization with microspheres labelled with β−-emitter radionuclides has become a well-established and powerful tool for the treatment of liver malignancies, since it adds to the embolization effect the deposition of lethal doses of radiation to the tumour cells.

Purpose We evaluated whether 18F-3′-deoxy-3′-fluorothymidine positron emission tomography (FLT PET) can predict the final postoperative histopathological response in primary breast cancer after the first cycle of neoadjuvant chemotherapy (NCT).

Conversion of aqueous [

Two positron-emitting analogues of tyrosine, O-[11C]methyl-L-tyrosine and O-[18F]fluoromethyl-L-tyrosine were prepared as new tumor imaging agents. The alkylating agent, [11C]methyl triflate or [18F]fluoromethyl triflate, was simply bubbled through a dimethylsulfoxide solution of L-tyrosine disodium salt at room temperature. After subsequent HPLC purification the labeled L-tyrosine analogues were obtained in decay-corrected radiochemical yields of over 50%, based on their corresponding labeling agent, with radiochemical purities always higher than 98%. The quite straightforward preparation, together with the high radiochemical yields achieved, make both these syntheses suitable for routine production. Copyright © 2003 John Wiley & Sons, Ltd.

We evaluated whether (18)F-3'-deoxy-3'-fluorothymidine positron emission tomography (FLT PET) can predict the final postoperative histopathological response in primary breast cancer after the first cycle of neoadjuvant chemotherapy (NCT).In this prospective cohort study of 15 patients with locally advanced operable breast cancer, FLT PET evaluations were performed before NCT, after the first cycle of NCT, and at the end of NCT. All patients subsequently underwent surgery. Variables from FLT PET examinations were correlated with postoperative histopathological results.At baseline, median of maximum standardized uptake values (SUVmax) in the groups showing a complete pathological response (pCR) + residual cancer burden (RCB) I, RCB II or RCB III did not differ significantly for the primary tumour (5.0 vs. 2.9 vs. 8.9, p = 0.293) or for axillary nodes (7.9 vs. 1.6 vs. 7.0, p = 0.363), whereas the Spearman correlation between SUVmax and Ki67 proliferation rate index was significant (r = 0.69, p 0.001). Analysis of the relative percentage change of SUVmaxin the primary tumour (∆SUVTmax(t₁)) and axillary nodes (∆SUVNmax(t₁)) after the first NCT cycle showed that the power of ∆SUVTmax(t 1) to predict pCR + RCB I responses (AUC = 0.91, p 0.001) was statistically significant, whereas ∆SUVNmax(t₁) had a moderate ability (AUC = 0.77, p = 0.119) to separate subjects with ΔSUVTmax(t₁) -52.9 % into two groups: RCB III patients and a heterogeneous group that included RCB I and RCB II patients. A predictive score μ based on ΔSUVTmax(t₁) and ΔSUVNmax(t₁) parameters is proposed.The preliminary findings of the present study suggest the potential utility of FLT PET scans for early monitoring of response to NCT and to formulate a therapeutic strategy consistent with the estimated efficacy of NCT. However, these results in a small patient population need to be validated in a larger independent cohort.

3-[1H-Imidazol-4-yl]propyl 4-fluorobenzyl ether (fluoroproxyfan), a potential histamine H 3 receptor ligand, was labeled with 18 F for clinical PET studies. The synthesis involved the O-alkylation of 3-(1-triphenylmethyl-1H-imidazol-4-yl)propanol with 4-[ 18 F]fluorobenzyl bromide in the presence of silver triflate and a non-nucleophilic amine base. 4-[18F]Fluoroproxyfan was obtained within 100 min from the end of bombardment (EOB) in 10% radiochemical yield (decay corrected to EOB) with a radiochemical purity >99% and a specific activity >150 GBq/μmol.

A novel approach to the synthesis of L-[S-methyl-11C]methionine ([11C]MET) is described which involves a commercial C18 Sep-Pak Plus as a solid-phase support material for the [11C]methylation step. The present method, which uses [11C]CH3I produced by the classical LiA1H4/HI route, supplies [11C]MET ready for injection within 11 min from the end of bombardment (EOB) with a radiochemical yield, decay corrected at EOB, of 78% and a radiochemical purity at the end of synthesis (EOS) higher than 99%. The required setup is extremely simple and easy to automate and can be reset for a further synthesis within a few minutes. Moreover, due to its versatility, the method can be utilized for the production of other radiopharmaceuticals requiring a simple [11C]methylation. Copyright © 1999 John Wiley & Sons, Ltd.

To investigate the possible role of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) in the prognostic evaluation of primary breast cancer, we studied 86 patients with T1-3 (TNM classification) breast tumours before surgery and compared the tumour FDG uptake, calculated as a standardized uptake value (SUV), with postoperative histopathological findings, steroid hormone receptor status of the tumour, thymidine labelling index (LI) and tissular expression of p53. SUV was significantly higher in infiltrating ductal carcinomas (n = 68; median SUV = 5.6) than in lobular ones (n = 18; median SUV = 3.8), and in grade 3 carcinomas (n = 26; median SUV = 6.2) than in grade 1-2 ones (n = 60; median SUV = 4.9). Moreover, SUV was significantly higher in carcinomas with high levels of p53 (n = 12; median SUV = 9.5) than in those with low levels (n = 48; median SUV = 4.25). By contrast, there was no significant correlation between SUV and the steroid hormone receptor status or LI of tumours. Our data demonstrate that FDG uptake, expressed as SUV, is associated with certain prognostic factors in breast cancer, such as histopathological grading and p53 expression, which can be assessed only by means of postoperative in vitro examinations. Hence, the information provided by FDG-PET is to some extent related to relevant information on tumour biology. The clinical value of these data will have to be confirmed by analysis of the independence of SUV from other prognostic factors by means of a multivariate analysis performed on a larger series of patients with adequate follow-up. If SUV is confirmed as an independent variable, FDG-PET could assume an important role in the determination of appropriate therapeutic strategies for primary breast cancer.

A novel automated system for the detection and disposal of radioactive gases emitted within the walls of a hot-cell is described. The system has been designed and installed at the Nuclear Medicine Division's FET Unit of the National Cancer Institute of Milan (Italy). Basically, a radiation detector monitors the air exhausted from the hot-cell, which is normally released through the hospital main chimmey. Beyond a selected threshold of radioactivity concentration, the air flow is automatically conveyed to a buffer tank. A set of measures to ensure radiation safety to the chemist is also reported.

Introduction 3′-Deoxy-3′-[ 18 F]fluorothymidine ([ 18 F]FLT) shows great potential as a tracer for proliferative studies with PET. However, its regular application is often limited by low radiochemical yields and the use of a troublesome HPLC separation. Moreover, a high content of ethanol, at least one-fold higher than the European Pharmacopoeia and US Pharmacopoeia's established limit, is always present in the final product. The present study reports an optimization of the reaction conditions and a simple and straightforward purification step which affords a solution of [ 18 F]FLT suitable for human use. Methods Several conditions and materials were tested for both the nucleophilic substitution and purification step. The latter was achieved by means of a series of commercial solid-phase extraction cartridges. Very conveniently, the whole one-pot synthesis was carried out on commercial automated modules using basically the same setup employed for the synthesis of [ 18 F]FDG. Results Under routine conditions, radiochemical yields of 37% [decay-corrected to start of synthesis (SOS)] were achieved in ca. 39 min from SOS, with radiochemical purities >98% (usually >99%). The negligible radiolysis observed could be easily suppressed by adding 0.5% of EtOH. Typical unlabelled chemical impurities detected were thymidine (0.15 ppm), thymine (0.28 ppm) and stavudine (0.05 ppm). Conclusions A reliable, simple and efficient preparation of [ 18 F]FLT has been developed, able to afford an ethanol-free solution of the tracer with no need for any HPLC purification. Because of its similarity to the [ 18 F]FDG synthesis, the method can be readily implemented on basically all the commercial modules developed for this common radiotracer.

The biologically active S -enantiomer of [ N -methyl- 11 C]citalopram was evaluated as a radioligand for in vivo labelling of the 5-hydroxytryptamine uptake site in brain, using ex vivo tissue counting in rats and positron emission tomography in man. In rats, the maximal signal for total versus non-specific binding was approx. 2 at 60–120 min after radioligand injection. Subsequent studies in man failed to identify a specific signal over a 90 min scanning period, due to prolonged retention of non-specific label.

In vivo autoradiography of [N-methly-3H]citalopram in rat brain shows a differential regional localization which correlates with the localization of 5-HT re-uptake binding sites defined in vitro. A comparison of the biodistribution of [N-mrthyl-3H]citalopram over 2 h after i.v. injection in (1) control rats (2) rats pre-dosed with either citalopram or paroxetine and (3) rats chemically-lesioned with p-chloroamphetamine provides an estimate of specific binding relative to total binding in vivo. The ratio of binding in certain regions (e.g. cingulate) to binding in a reference tissue (e,g, cerebellum) at 30–120 min post injection is c. 1.4. In view of these results a method was developed for labelling citalopram with carbon-11 ( t 1 2 = 20.3 min, β+ = 99.8%) to provide a potential radioligand for studies using positron emission tomography. Thus, reaction of nca [11C]iodomethane, prepared from cyclotron-produced [11C]carbon dioxide, with norcitalopram in ethanol containing 2,2,6,6-tetramethyl-piperidine for 5 min at 95 °C gives crude [N-methyl-11C]citalopram in 60% radiochemical yield, decay-corrected. HPLC on silica gel provides radiochemically and chemically pure [N-methyl-11C]citalopram, as assessed by TLC, HPLC and MS. This product (isolated radiochemical yield, 49%) is easily formulated for i.v. injection. Up to 2GBq of formulated product with a specific activity of c. 15 GBq/μmol have been prepared within 40min from the end of radionuclide production. The described radiosynthesis has also been applied to give the single biologically active (+)-enantiomer of [N-methyl-11C]citalopram rather than the racemate. This product gives enhanced specific signal in the rat following i.v. injection, the ratio of uptake in regions of interest relative to cerebellum approaching 2 at 90 min.

Viqualine, {4-[3-[3(R)-ethenyl-4(R)-piperidinyl]propyl]-6-methoxyquinoline}, has been labelled in the O-methyl position with no-carrier-added (nca) carbon-11 (t1/2 = 20.4 min; β+ = 99.8%) to provide a potential radioligand for PET studies of 5HT re-uptake sites. Direct treatment of desmethyl-viqualine with nca [11C]iodomethane gave [O-methyl-11C]viqualine as only a minor product. NMR data suggested that the dominant product is that from the [11C]alkylation of the competing piperidino-nitrogen. Protection of this nitrogen with the trityl group, followed by treatment with nca [11C]iodomethane in dimethyl sulphoxide with sodium hydroxide as base, and then rapid deprotection by mild acid hydrolysis gave nca [O-methyl-11C]viqualine as the main crude product (27% radiochemical yield, decay-corrected from [11C]iodomethane). Radiochemically and chemically pure nca [O-methyl-11C]viqualine was obtained by work up on C18 Sep-pak followed by reverse phase HPLC. The radiosynthesis, including final formulation for i.v. administration, takes 56 min after producing the carbon-11 as [11C]carbon dioxide by the 14N(p,α)11C reaction. This radiosynthesis illustrates the potential utility of the trityl group for the protection of nitrogen in rapid carbon-11 radiochemistry.

A method has been developed for labelling PK 14105 [N-methyl-N-(1-methyl-propyl)-1(2-fluoro-5-nitrophenyl)isoquinoline-3- carboxamide], a ligand that has high affinity and selectivity for peripheral type benzodiazepine binding sites (PBBS), with NCA fluorine-18 (t1/2 = 109.8 min, beta + = 96.9%). The method involves treating the 2-chloro-analogue with cyclotron-produced NCA [18F]fluoride in dimethyl sulphoxide, with rubidium carbonate as base, at 140 degrees C for 20 min. Purification is achieved by separation on a reverse phase Sep-Pak followed by PHLC on a silica gel column, to give chemically and radiochemically pure product with a specific activity of ca 7.4 GBq/mumol (200 mCi/mumol), decay-corrected to the end of radionuclide production (EOB). The radiosynthesis requires 210 min. giving a radiochemical yield of 10-20%, decay-corrected to EOB. [18F]PK 14105 was found to bind avidly to sites associated with kainic acid-induced unilateral lesions of rat striata. Such binding was blocked by pre-dosing the rat with PK 11195, so providing evidence for specific binding to PBBS. These results suggest that [18F]PK 14105 has potential for studying phenomena associated with PBBS in man by PET.

The previously reported preparation of O-[(11)C]methyl-l-tyrosine ([(11)C]MT), a promising tumor imaging agent, has been now considerably simplified and automated. Main changes were the use of [(11)C]methyl iodide ([(11)C]MeI) in the reaction with l-tyrosine disodium and the use of solid phase extraction on commercially available cartridges instead of HPLC for the final purification. An injectable saline solution of [(11)C]MT was obtained within 30 min after EOB with radiochemical yield of ca. 60% (decay-corrected, based on [(11)C]MeI). Radiochemical purity was over 97%. The automated preparation was carried out using a miniature module employing manifold valves.

We investigated the potential of O -[ 11 C]methyl-L-tyrosine and O -[ 18 F]fluoromethyl-L-tyrosine as positron-emitting tracers for tumor imaging. The two tracers had similar distribution patterns in rats bearing AH109A hepatoma, with pancreas and, on a lesser extent, AH109A showing the highest uptake. Uptake of both tracers in the AH109A and uptake ratios of AH109A-to-tissues (with the exception of AH109A-to-bone) gradually increased for 60 min. O -[ 11 C]methyl-L-tyrosine was metabolically stable, whereas a negligible low amount of metabolites was observed for O -[ 18 F]fluoromethyl-L-tyrosine. Both tracers showed the potential for tumor imaging.

The production and use of [18F]fluoromethyl triflate ([18F]CH2FOTf), a more reactive [18F]fluoromethylating agent than [18F]fluoromethyl bromide ([18F]CH2BrF), is described. [18F]CH2FOTf was prepared from [18F]CH2BrF. The latter was synthesized by nucleophilic substitution of CH2Br2 with no-carrier-added [18F]fluoride and purified by four Sep-Pak Plus silica cartridges connected in series. It was then quantitatively converted on-line to [18F]CH2FOTf by passing through a heated AgOTf column. Decay-corrected radiochemical yields of [18F]CH2FOTf based on [18F]fluoride were 47±8% (n=20). Both [18F]CH2BrF and [18F]CH2FOTf were applied to solid-supported [18F]fluoromethylation of N,N-dimethylaminoethanol on a Sep-Pak Plus C18 cartridge to produce the 18F-labeled choline analogue, (β-hydroxyethyl)dimethyl-[18F]fluoromethylammonium ([18F]fluorocholine). Depending on flow rate and amount of precursor used, decay corrected radiochemical yields of [18F]fluorocholine from [18F]CH2BrF ranged from 6% to 63%, while [18F]CH2FOTf afforded yields of more than 80%. Thus, by using the latter reagent and a subsequent purification on a Sep-Pak Accell CM cartridge, [18F]fluorocholine was produced from [18F]fluoride in overall radiochemical yields of 40% (decay corrected) in less than 30 min.

In rat brain, the biologically active isomer (+)-[ N - methyl - 11 C]citalopram can be used to label 5-HT uptake sites in vivo , giving ratios of uptake in selected regions of interest relative to cerebellum of approximately 2: 1. In human brain, however, the non-specific carbon-11 label is retained over a 90 min scanning period. Both (+)- and (-)-isomers gave similar summed images and similarly shaped time-activity curves for all regions analysed (including cerebellum). The reasons for the species difference in retention of non-specific label are not clear.

Peripheral-type benzodiazepine binding sites are not normally present in most cerebral tissues, but following neuronal damage, the cells involved in the ensuing gliosis show a marked expression of these sites. In a unilateral excitotoxic striatal lesion in the rat, we sought to determine whether the isoquinoline derivatives PK11195 and PK14105 bind to these sites in vivo and whether demonstration of these sites offers the potential of indirectly localising areas of neuronal damage. Binding was studied at several intervals after coinjection of [3H]PK11195 and [18F]PK14105 to determine the time courses of specific binding. Both compounds were rapidly extracted into all cerebral tissues, but in the absence of binding sites in nonlesioned tissues, this was followed by a rapid clearance of radioactivity. In lesioned areas, both [3H]PK11195 and [18F]PK14105 accumulated over the first 5 min followed by a much slower clearance of radioactivity, resulting in a "specific signal." [3H]PK11195 binding peaked at 20-30 min postinjection, with radioactivity in the lesioned striatum being three times greater than in its contralateral homologue. The specific signal was present for at least 60 min. The maximal [18 F]PK14105-specific signal was of similar magnitude but peaked earlier and was retained for only 45 min. Specific signals with both ligands were also detected in regions remote from the primary lesion site, e.g., in the hippocampus and substantia nigra. Predosing animals with a large dose of PK11195 (3 mg/kg), sufficient to saturate peripheral-type benzodiazepine binding sites, abolished in vivo binding of both [3H]PK11195 and [18F]PK14105 to both primary- and remote-lesioned tissues. The specific signal with both ligands could be of sufficient magnitude and duration to make tomographic studies in humans feasible.