THE STRUCTURE OF Hp(0.07) VALUES OBTAINED BY THE NUCLEAR MEDICINE PERSONNEL DURING 18F-FDG PRODUCTION AND INJECTION

The production of 18F-FDG is a multi-stage process, which includes not only obtaining the marker and labelling the radiopharmaceutical but also carrying out the quality control of the obtained compound. The staff can be exposed to ionizing radiation at any stage of production. This article presents the results of hands exposure of staff members employed in a facility, where 18F-FDG is produced and injected into patients. High-sensitivity thermoluminescent detectors (MCP-N) were used for measurements. The measurements were conducted with regard to the occupational structure the employees and the performed procedures. The obtained results showed that the highest risk of radiation exposure for personnel was associated with the quality control of the radiopharmaceutical. The daily doses registered by MCP-N detectors on fingertips reached 4.5 mSv, which may result in exceeding the annual radiation limit of 500 mSv.

THYROID EXPOSURE DURING 18F-FDG PRODUCTION PROCEDURES

The production of radiopharmaceuticals for the needs of positron emission tomography (PET), in particular 18F-FDG, is a multi-step process performed most often by physicists and chemists. The monitoring of occupational exposure of staff employed in radiopharmaceutical production centres includes the measurement of the Hp(10) and Hp(0.07) values. Occupational exposure to ionising radiation means that the thyroid may be, among others, affected by the radiation field. This work analyses the exposure of the thyroid gland of employees of centres that produce the isotopes for PET, in particular fluorine-18. The analysis take into account the employment structure and work system of the discussed centres. Measurements were carried out by using high-sensitivity thermoluminescence detectors (MCP-N). The measurements covered 17 employees. Our results show that the estimated maximum annual thyroid gland exposure will not exceed 30 mSv.

Synthesis and evaluation of an N-[18F]fluorodeoxyglycosyl amino acid for PET imaging of tumor metabolism

INTRODUCTION

The limitations of [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG), including producing false-positive or -negative results, low image contrast in brain tumor diagnosis and poor differentiation of tumor and inflammatory, necessitate the development of new radiopharmaceuticals. In the present study, a novel [¹⁸F]fluoroglycoconjugate tracer, [¹⁸F]FDGly-NH-Phe, for tumor metabolism imaging was prepared and evaluated.

METHODS

[¹⁸F]FDGly-NH-Phe was prepared by condensing [¹⁸F]FDG with L-4-aminophenylalanine in an acidic condition, and purified with semi-preparative-high performance liquid chromatography (HPLC). The in vitro stability study was conducted in phosphate-buffered saline (PBS, pH 4.0-9.18) at room temperature (RT) and in fetal bovine serum (FBS) at 37 °C. The preliminary cellular uptake studies were performed using Hep-2 cell. The bio-distribution studies, PET/CT imaging and metabolism studies were performed and compared with [¹⁸F]FDG on ICR or BALB/c nude model mice.

RESULTS

[¹⁸F]FDGly-NH-Phe was derived from a direct condensation of [¹⁸F]FDG with L-4-aminophenylalanine with high stability in FBS and PBS (pH of 6.5-9.18). In vitro cell experiments showed that [¹⁸F]FDGly-NH-Phe uptake in Hep-2 cells was primarily transported through amino acid transporters including Na⁺-dependent A system, ASC system, and system B^0,+ system. The bio-distribution of [¹⁸F]FDGly-NH-Phe in normal ICR mice showed faster blood radioactivity clearance, and lower uptake in brain and heart than [¹⁸F]FDG. The performance of PET/CT imaging for [¹⁸F]FDGly-NH-Phe in the mice model manifested excellent tumor visualization, high tumor-to-background ratios, and low accumulation in inflammatory lesions. Metabolism studies for [¹⁸F]FDGly-NH-Phe indicated high in vivo stability in plasma and urine and decomposition into [¹⁸F]FDG in the tumor microenvironment.

CONCLUSION

The results demonstrated that [¹⁸F]FDGly-NH-Phe as a novel amino acid PET tracer showed the capability to differentiate tumor from inflammation, and the potentials for future clinical applications.

The effect of work system on the hand exposure of workers in 18F-FDG production centres

The production of the 18F isotope-the marker of deoxyglucose (18F-FDG)-the radiopharmaceutical most commonly used in the oncological diagnostic technique of positron emission tomography, requires a cyclotron device. At present, there are nine facilities working in Poland that are equipped with cyclotrons used for producing the short-lived isotopes. The aim of the paper is to determine the hand exposure of workers employed in the two 18F-FDG production centres taking in to account the production procedures and work system in those facilities. Measurements, which included all professional workers exposed to ionizing radiation that were employed in two facilities, were performed by using high-sensitivity thermoluminescent detectors during the routine activities of the personnel. The work system used at the production centre has an impact on the level of the recorded doses. Among the production procedures performed by the staff, the highest ionizing radiation doses have been received by the staff during the 18F-FDG quality control. The maximum estimated annual Hp(0.07) for chemists from the quality control department can exceed the annual skin limit dose (500 mSv). The source of lowest doses on the hands are the cyclotron operating procedure and the 18F-FDG production, provided that these procedures can't be combined with other production procedures.

Management of radioactive waste gases from PET radiopharmaceutical synthesis using cost effective capture systems integrated with a cyclotron safety system

The emphasis on the reduction of gaseous radioactive effluent associated with PET radiochemistry laboratories has increased. Various radioactive gas capture strategies have been employed historically including expensive automated compression systems. We have implemented a new cost-effective strategy employing gas capture bags with electronic feedback that are integrated with the cyclotron safety system. Our strategy is suitable for multiple automated ¹⁸F radiosynthesis modules and individual automated ¹¹C radiosynthesis modules. We describe novel gas capture systems that minimize the risk of human error and are routinely used in our facility.

Quantification of the activity of tritium produced during the routine synthesis of (18)F fluorodeoxyglucose for positron emission tomography

Gamma emitting radioactive by-products generated during the cyclotron irradiation of (18)O labelled water by protons to produce (18)FDG (fluorodeoxyglucose) for positron emission tomography are well characterised. However, the production of tritium ((3)H) through the (18)O(p,t)(16)O nuclear reaction has not been investigated in detail. The aim of this study was to measure tritium activity produced during a large number of (18)FDG production runs in order to obtain a better perspective on its impact on radioactive waste management, particularly as regards storage and disposal. Tritium was assayed by liquid scintillation counting in recovered (18)O water from 24 separate production runs. The mean (SD) values of activity and activity concentration were 170 (20) kBq and 81 (8) kBq ml(-1) respectively. Both quantities were positively correlated with the activity of (18)F. Tritium was detected in much lower concentration in water used to rinse the target vessel. The activity of tritium is such that it is exempt from regulatory control and may be combined with bulk non-active waste for disposal as Very Low Level Waste. However, variations in the irradiation conditions or the procedures for the collection of recovered water might result in its classification as Low Level Waste, necessitating a more complex disposal regime.

Targeting paraprotein biosynthesis for non-invasive characterization of myeloma biology

Purpose

Multiple myeloma is a hematologic malignancy originating from clonal plasma cells. Despite effective therapies, outcomes are highly variable suggesting marked disease heterogeneity. The role of functional imaging for therapeutic management of myeloma, such as positron emission tomography with 2-deoxy-2-[¹⁸F]fluoro-D-glucose (¹⁸F-FDG-PET), remains to be determined. Although some studies already suggested a prognostic value of ¹⁸F-FDG-PET, more specific tracers addressing hallmarks of myeloma biology, e.g. paraprotein biosynthesis, are needed. This study evaluated the amino acid tracers L-methyl-[¹¹C]-methionine (¹¹C-MET) and [¹⁸F]-fluoroethyl-L-tyrosine (¹⁸F-Fet) for their potential to image myeloma and to characterize tumor heterogeneity.

Experimental Design

To study the utility of ¹¹C-MET, ¹⁸F-Fet and ¹⁸F-FDG for myeloma imaging, time activity curves were compared in various human myeloma cell lines (INA-6, MM1.S, OPM-2) and correlated to cell-biological characteristics, such as marker gene expression and immunoglobulin levels. Likewise, patient-derived CD138⁺ plasma cells were characterized regarding uptake and biomedical features.

Results

Using myeloma cell lines and patient-derived CD138⁺ plasma cells, we found that the relative uptake of ¹¹C-MET exceeds that of ¹⁸F-FDG 1.5- to 5-fold and that of ¹⁸F-Fet 7- to 20-fold. Importantly, ¹¹C-MET uptake significantly differed between cell types associated with worse prognosis (e.g. t(4;14) in OPM-2 cells) and indolent ones and correlated with intracellular immunoglobulin light chain and cell surface CD138 and CXCR4 levels. Direct comparison of radiotracer uptake in primary samples further validated the superiority of ¹¹C-MET.

Conclusion

These data suggest that ¹¹C-MET might be a versatile biomarker for myeloma superior to routine functional imaging with ¹⁸F-FDG regarding diagnosis, risk stratification, prognosis and discrimination of tumor subtypes.

Optimization of microfluidic PET tracer synthesis with Cerenkov imaging

Microfluidic technologies provide an attractive platform for the synthesis of radiolabeled compounds. Visualization of radioisotopes on chip is critical for synthesis optimization and technological development. With Cerenkov imaging, beta particle emitting isotopes can be localized with a sensitive CCD camera. In order for Cerenkov imaging to also serve as a quantitative tool, it is necessary to understand how material properties relevant to Cerenkov emission, namely, index of refraction and beta particle stopping power, affect Cerenkov light output. In this report, we investigate the fundamental physical characteristics of Cerenkov photon yield at different stages of [(18)F]FDG synthesis on the electrowetting on dielectric (EWOD) microfluidic platform. We also demonstrate how Cerenkov imaging has enabled synthesis optimization. Geant4, a Monte Carlo program applied extensively in high energy physics, is used to simulate Cerenkov photon yield from (18)F beta particles traversing materials of interest during [(18)F]FDG synthesis on chip. Our simulations show that the majority (approximately two-thirds) of the (18)F beta particle energy available to produce Cerenkov photons is deposited on the glass plates of the EWOD chip. This result suggests the possibility of using a single calibration factor to convert Cerenkov signal to radioactivity, independent of droplet composition. We validate our simulations with a controlled measurement examining varying ratios of [(18)O]H2O, dimethyl sulfoxide (DMSO), and acetonitrile (MeCN), and find a consistent calibration independent of solvent composition. However, the calibration factor may underestimate the radioactivity in actual synthesis due to discoloration of the droplet during certain steps of probe synthesis. In addition to the attractive quantitative potential of Cerenkov imaging, this imaging strategy provides indispensable qualitative data to guide synthesis optimization. We are able to use this imaging technique to optimize the mixing protocol as well as identify and correct for loss of radioactivity due to the migration of radioactive vapor outside of the EWOD heater, enabling an overall increase in the crude radiochemical yield from 50 ± 3% (n = 3) to 72 ± 13% (n = 5).

Automated solid-phase radiofluorination using polymer-supported phosphazenes

The polymer supported phosphazene bases PS-P₂(tBu) and the novel PS-P₂(PEG) allowed for efficient extraction of [¹⁸F]F⁻ from proton irradiated [¹⁸O]H₂O and subsequent radiofluorination of a broad range of substrates directly on the resin. The highest radiochemical yields were obtained with aliphatic sulfonates (69%) and bromides (42%); the total radiosynthesis time was 35-45 min. The multivariate analysis showed that the radiochemical yields and purities were controlled by the resin load, reaction temperature, and column packing effects. The resins could be reused several times with the same or different substrates. The fully automated on-column radiofluorination methodology was applied to the radiosynthesis of the important PET radiotracers [¹⁸F]FLT and [¹⁸F]FDG. The latter was produced with 40% yield on a 120 GBq scale and passed GMP-regulated quality control required for commercial production of [1¹⁸F]FDG. The combination of compact form factor, simplicity of [¹⁸F]F⁻ recovery and processing, and column reusability can make solid phase radiofluorination an attractive radiochemistry platform for the emerging dose-on-demand instruments for bedside production of PET radiotracers.

Radiochemistry on chip: towards dose-on-demand synthesis of PET radiopharmaceuticals

We have developed an integrated microfluidic platform for producing 2-[(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG) in continuous flow from a single bolus of radioactive isotope solution, with constant product yields achieved throughout the operation that were comparable to those reported for commercially available vessel-based synthesisers (40-80%). The system would allow researchers to obtain radiopharmaceuticals in a dose-on-demand setting within a few minutes. The flexible architecture of the platform, based on a modular design, can potentially be applied to the synthesis of other radiotracers that require a two-step synthetic approach, and may be adaptable to more complex synthetic routes by implementing additional modules. It can therefore be employed for standard synthesis protocols as well as for research and development of new radiopharmaceuticals.

Effective use of a new quality and safety checklist for the steady and safe supply of fluorine-18 fluorodeoxyglucose for positron emission tomography/computed tomography

Fluorine-18-fluorodeoxyglucose ((18)F-FDG ) positron emission tomography/computed tomography (PET/CT) with the in-hospital synthesis of (18)F-FDG was initiated in our hospital on April 1, 2010. We aim to perform stable supply of (18)F-FDG for patients and to avoid unnecessary radiation exposure due to mis-preparation of (18)F-FDG. Pharmacists perform quality control tests to determine whether (18)F-FDG meets official regulations. After the quality control test, we give (18)F-FDG that conforms to these standards to patients to conduct (18)F-FDG PET/CT. After a quality control test is initiated, various problems can occur including leakage and staff radiation exposure. We recorded daily radiation exposure in the hot lab and calculated the average daily radiation exposure on a monthly basis for a period of one year. We developed a checklist to safely and quickly synthesize(18)F-FDG for patients. The total radiation exposure of the three pharmacists was 394, 180, and 214μSv/y and overall lower than the occupational maximum values (≤50mSv/year and ≤100mSv/5years for males). In conclusion, using the new checklist, pharmacists and the operator of the Sumitomo Heavy Industries Accelerator service Co., Ltd. were able to practice their daily work effectively during the synthesis and quality control testing of (18)F-FDG. Notably the usual radiation exposure reported in the present study was quite lower than the allowable maximum.

[Adaptation of the (18)FDG module for the preparation of a sodium fluoride [(18)F] injection solution in agreement with the United States (USP 32) and European Pharmacopeia (PhEur 6)]

OBJECTIVE

To establish an automated procedure for the preparation of sodium fluoride (18)F injection using the resources available in our laboratory for the preparation of (18)FDG and to analyze the repercussion of the conditioning column of the fluoride ion entrapment on the characteristics of the final product.

MATERIAL AND METHOD

The sequence of an (18)FDG synthesis module prepared so that it traps the fluoride ion from the cyclotron in ion-exchange resin diluted with 0.9% sodium chloride. The final solution was dosified and sterilized in a final vial in an automatized dispensing module. Three different column conditioning protocols within the process were tested. Quality controls were run according to USP 32 and EurPh 6, adding control of ethanol levels of residual solvent and quality controls of the solution at 8 h post-preparation.

RESULTS

Activation of the resin cartridges with ethanol and water was the chosen procedure, with fluoride ion trapping > 95% and pH around 7. Ethanol levels were < 5.000 ppm. Quality controls at 8 h indicated that the solution was in compliance with the USP 32 and EurPh 6 specifications.

CONCLUSION

This is an easy, low-cost, reliable automated method for sodium fluoride preparation in PET facilities with existing equipment for (18)FDG synthesis and quality control.

PET designated flouride-18 production and chemistry

Positron emission tomography (PET) is a nuclear medicine imaging technology which allows for four-dimensional, quantitative determination of the distribution of labeled biological compounds within the human body. PET is becoming an increasingly important tool for the measurement of physiological, biochemical and pharmacological functions at the molecular level in healthy and pathological conditions. This review will focus on Flouride-18, one of the common isotopes used for PET imaging, which has a half life of 109.8 minutes. This isotope can be produced with an efficient yield in a cyclotron as a nucleophile or as an electrophile. Flouride-18 can be thereafter introduced into small molecules or biomolecules using various chemical synthetic routes, to give the desired imaging agent.

[Automated synthesis of 2-[(18)F]-fluoro-2-deoxy-D-glucose by on-column hydrolysis]

OBJECTIVE

To study automated synthesis of 2-[(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG) via on-column hydrolysis.

METHODS

Automated synthesis of (18)F-FDG was performed by the on-column hydrolysis procedure in TRACERlab FXF-N synthesizer. (18)F-FDG injection was obtained via nucleophilic fluorination of 1, 3, 4, 6-tetra-O-acetyl-2-O-trifluoromethanesulfony-beta-D-mannopyranose as the precursor molecule with (18)F-fluoride, hydrolysis of the (18)F-labeled intermediate on SEP-PAK C18 cartridges with 2 mol/L NaOH solution, and purification and neutralization with SEP-PAK cartridges.

RESULTS

The uncorrected radiochemical yield of (18)F-FDG was more than 60% within the total synthesis time shorter than 20 min. The radiochemical purity of (18)F-FDG was above 99%.

CONCLUSION

On-column hydrolysis is simple and practical for the automated synthesis of (18)F-FDG. (18)F-FDG injection produced by this procedure can be used in clinical PET imaging.

Assessment of radionuclidic impurities in 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) routine production

In this paper, radionuclidic impurities generated during the bombardment of [18 O]water in the routine production of 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) were studied. In order to assess such impurities and the efficacy of purification methods through the different steps of the synthesis, samples of the target filters, purification columns, [18 O]water recovered after the synthesis, and the final solution was collected and their activities measured and analyzed by means of a gamma-ray spectrometry system. The data demonstrated that purification methods adopted for the synthesis provide the [18F]FDG radionuclidically pure, as requested by the EU Pharmacopeia.

Synthesis modules and automation in F-18 labeling

Fast implementation of PET into clinical studies and research has resulted in high demands in the automated modules for the preparation of PET radiopharmaceuticals in a safe and reproducible manner. 18F-labeled radiotracers are of considerable interest due to longer half-life of fluorine-18 allowing remote site application, as demonstrated by [18F]FDG. In this chapter, the state of the art of commercially available modules for [18F]FDG is reviewed with the emphasis on multibatch production of this important radiotracer. Examples are given on the syntheses of other clinically relevant 18F-labeled radiotracers by using existing [18F]FDG synthesizers or with the help of general-purpose [18F]nucleophilic fluorination modules. On-going research and progress in the automation of complex radio labeling procedures followed by development of flexible multipurpose automated apparatus are discussed. The contribution of radiochemists in facilitating automation via introduction of new 18F-labeling techniques and labeling synthons, on-line reactions and purifications etc. is outlined.

Radioactive byproducts in [18O]H2O used to produce 18F for [18F]FDG synthesis

Potential radioactive byproducts in [(18)O]H(2)O irradiated with 9.6 MeV protons to produce (18)F were analyzed theoretically and experimentally. Twenty two nuclear reaction cross sections included in the National Nuclear Data Center's (NNDC) data base were selected from the possible nuclear reactions between 9.6 MeV protons and a silver havar target. Ten radionuclides: (52)Mn, (55)Fe, (55)Co, (56)Co, (57)Co, (58)Co, (59)Ni, (95)Tc, (96)Tc and (109)Cd were detected experimentally in [(18)O]H(2)O by using high purity germanium semiconductor detectors. The activities of the 10 radionuclides were distributed between 4B q and 1.2k Bq. These activities were less than the reference values given in the International Basic Safety Standards. The radionuclides derived from nuclear reactions between a silver target body and 9.6 MeV protons at a beam current 25 microA for 60 min irradiation would be exempt from restrictions for radioactive waste. The purified [(18)F]FDG prepared from (18)F produced by irradiating a silver havlar target with 9.6 MeV protons was not contaminated by the radionuclides.

Multistep Synthesis of a Radiolabeled Imaging Probe Using Integrated Microfluidics

Microreactor technology has shown potential for optimizing synthetic efficiency, particularly in preparing sensitive compounds. We achieved the synthesis of an [(18)F]fluoride-radiolabeled molecular imaging probe, 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), in an integrated microfluidic device. Five sequential processes-[18F]fluoride concentration, water evaporation, radiofluorination, solvent exchange, and hydrolytic deprotection-proceeded with high radio-chemical yield and purity and with shorter synthesis time relative to conventional automated synthesis. Multiple doses of [18F]FDG for positron emission tomography imaging studies in mice were prepared. These results, which constitute a proof of principle for automated multistep syntheses at the nanogram to microgram scale, could be generalized to a range of radiolabeled substrates.

Improved quality control of [18F]FDG by HPLC with UV detection

A conventional high-performance liquid chromatographic (HPLC) method for the analysis of 2-fluoro-2-deoxy-d-glucose (FDG) and 2-deoxy-2-chloro-d-glucose (ClDG) in [18F]FDG preparations is described. This method was based on a postcolumn derivatization with 2-cyanoacetamide (2-CA) and UV detection. FDG and ClDG were separated on a normal-phase column using acetonitrile/water as the mobile phase. The eluate was mixed with 2-CA in sodium borate buffer solution at the outlet of a PTFE coil (10 m x 0.5 mm id) from the column, and the reaction was carried out at 100 degrees C during the passage through the coil. The UV absorbance of the resultant product was monitored at 276 nm. Under optimum conditions, the detection limits [signal-to-noise (S/N) ratio=3] for FDG and ClDG were 0.31 and 0.17 microg/ml for a 20-microl injection volume, respectively, and the linearity ranges were 0.5-100 microg/ml for both compounds. The intra- and interday reproducibilities were better than 2.2% [relative standard deviation (R.S.D.)]. This HPLC separation procedure is also useful for determining the radiochemical purity of [18F]FDG preparations since it allows the analysis of 2-[18F]fluoro-1,3,4,6-tetra-O-acetyl-d-glucose ([18F]TAG), partially hydrolyzed [18F]TAG and [18F]F-. This method can be used at many positron emission tomography (PET) facilities since it does not require an expensive, sophisticated electrochemical detector.

Rapid synthesis of [18F]FDG without an evaporation step using an ionic liquid

In this study, we describe a new 2-[18F]fluoro-2-deoxy-d-glucose ([18F]FDG) synthesis without a distillation step. This involves fluorinating in an ionic liquid-containing medium. A test for the effective elution of [18F]fluoride from the anion exchange resin showed the proper selection of the base and the required eluant composition, which is an essential requirement for the automation of [18F]FDG synthesis. An 18F-labeling study by nucleophilic substitution showed that the major factors controlling the yield were the temperature and the reaction medium composition. The 18F-fluorination proceeded with a labeling efficiency of 74.6+/-7.4% (n=8) for optimized conditions. Alkaline hydrolysis and purification carried out in the liquid phase provided a final decay-corrected [18F]FDG yield of 59.1+/-5.1% (n=3), a radiochemical purity of 91.9+/-3.7% (n=3), and a reaction time of 13 min. Alkaline hydrolysis and purification carried out in the solid phase provided a final decay-corrected [18F]FDG yield of 48.8+/-6.0% (n=3), a radiochemical purity of 96.0+/-4% (n=3), and a reaction time of 19 min. The rapid and straightforward synthesis of [18F]FDG can be achieved by eliminating all evaporation steps, which is made possible by the use of ionic liquid-containing media for the fluorination step.

Practical and reliable synthesis of 1,3,4,6-tetra--acetyl-2-- trifluoromethanesulfonyl-?-D-mannopyranose, a Precursor of 2-Deoxy-2-[F]fluoro-D-glucose (FDG)

PURPOSE

To develop a practical and reliable synthesis of 1,3,4,6-tetra-O-acetyl-2-O-trifluoromethanesulfonyl-beta-D-mannopyranose (mannose triflate), a precursor of 2-deoxy-2-[18F]fluoro-D-glucose (FDG).

PROCEDURES

The key intermediate in the preparation of the triflate precursor, 1,3,4,6-tetra-O-acetyl-beta-D-mannopyranose, was synthesized starting from D-mannose via the following four steps: (1) per-O-acetylation with Ac2O-I2, (2) formation of acetobromomannose with 30% HBr in AcOH, (3) 1,2-orthoester formation with EtOH-2,4,6-collidine and (4) hydrolysis of the 1,2-orthoester with 1M aqueous HCl. Triflation of this key intermediate with Tf2O-pyridine then completed the synthesis of the mannose triflate.

RESULTS

Starting from 200 g of D-mannose, the triflate precursor was synthesized with an overall yield of 65 g to 85 g (12% to 16%) in approximately seven days. The inherent low efficiency of the orthoester hydrolysis was compensated by the quantitative recovery and subsequent recycling of penta-O-acetyl-D-mannopyranose.

CONCLUSION

A large-scale preparation of mannose triflate is now routinely carried out to satisfy the growing needs for FDG in both research centers and hospitals.

Routine quality control of recycled target [18O]water by capillary electrophoresis and gas chromatography

Recycling of [(18)O]water for [(18)F]fluoride production can be accomplished with reliable results. We have developed sensitive, robust, and rapid analyses of impurities in [(18)O]water. Anions were quantitated by capillary electrophoresis and organic residuals were quantitated by gas chromatography using methods with excellent reproducibility and linearity. Kryptofix 222 (K-222) was quantitated by a sensitive LC-MS-MS technique. Isotopic composition was determined by GC-MS with satisfactory accuracy and precision. These methods were employed to evaluate recovered [(18)O]water purified by a novel electrolysis method. 2-[(18)F]FDG yields using purified [(18)O]water with very low levels of impurities are indistinguishable from newly purchased [(18)O]water. High (> 300 ppm) carbonate concentration reduces the fluoride trapping efficiency of QMA. The analyses of anions, organics, and isotopic enrichment were applied routinely for quality control of [(18)O]water to predict a satisfactory outcome of 2-[(18)F]FDG production.

PET Practice in Nuclear Pharmacy

PET systems, which are based on many years of work in theoretical and practical physics, provide a window into both normal and disease state biochemical processes not possible by other external imaging techniques. FDG is a workhorse of PET chemistry, helping to visualize the accumulation of glucose in cancer cells. A complex series of steps is involved in [18F]fluoride ion production to make a sterile, injectable solution of FDG. PET and CT scanners are being developed that increase greatly the clinical utility of both technologies.

Adduct of 2-[18F]FDG and 2-nitroimidazole as a putative radiotracer for the detection of hypoxia with PET: synthesis, in vitro- and in vivo-characterization

A new sugar-coupled 2-nitroimidazole derivative ([18F](see structure in text)) has been prepared in good radiochemical yields starting from peracetylated 2-[18F]FDG obtained from an automated 2-[18F]FDG production module. The corresponding glucose derivative (see structure in text) has proved to be able to inhibit 2-[18F]FDG uptake into tumor cells in a concentration dependent way. However, [18F](see structure in text) failed to show a retention in hypoxic tumor tissue thus excluding itself from further investigations.

Chemical impurities in [18F]FDG preparations produced by solid-phase 18F-fluorination

[18F]FDG was produced by solid-phase 18F-fluorination (resin method) and chemical impurities were determined in the [18F]FDG preparations by ion chromatography. The major chemical impurities were D-glucose (90.5 +/- 6.4 microg/mL), 2-chloro-2-deoxy-D-glucose (11.8 +/- 2.7 microg/mL), and D-mannose (1.7 +/- 0.7 microg/mL), which were expected to be present by considering the synthetic routes. An FDG mass (0.5 +/- 0.2 microg/mL) was also detected in the preparations. No notable radiochemical impurities, including 2-[18F]fluoro-2-deoxy-D-mannose, were detected in the [18F]FDG preparations. Thus, the levels of several chemical impurities were determined in the [18F]FDG preparations produced by solid-phase 18F-fluorination.

Initial and subsequent approach for the synthesis of 18FDG

2-deoxy-2-[18F] fluoro-D-glucose (18FDG) was developed in 1976 in a collaboration between scientists at the National Institutes of Health, the University of Pennsylvania, and Brookhaven National Laboratory. It was developed for the specific purpose of mapping brain glucose metabolism in living humans, thereby serving as a tool in the basic human neurosciences. With 18FDG it was possible for the first time to measure regional glucose metabolism in the living human brain. Around the same time, the use of 18FDG for studies of myocardial metabolism and as a tracer for tumor metabolism were reported. After the first synthesis of 18FDG via an electrophilic fluorination with 18F gas (produced via the 20Ne(d,alpha)18F reaction), small volume enriched water targets were developed that made it possible to produce large quantities of [18F]fluoride ion via the high-yield 18(p,n)18F reaction. This was followed by a major milestone, the development of a nucleophilic fluorination method that produced 18FDG in very high yield. These advances and the remarkable properties of 18FDG have largely overcome the limitations of the 110-minute half-life of 18F so that 18FDG is now available to most regions of the United States from a number of central production sites. This avoids the need for an on-site cyclotron and chemistry laboratory and has opened up the use of 18FDG to institutions that have a positron emission tomography (PET) scanner (or other imaging device) but no cyclotron or chemistry infrastructure. Currently, 18FDG is used by many hospitals as an off the shelf radiopharmaceutical for clinical diagnosis in heart disease, seizure disorders, and oncology, the area of most rapid growth. However, it remains an important tool in human neuroscience and in drug research and development.

Performance assessment of O-18 water purifier

In the synthesis of 18F-FDG by the nucleophilic substitution method, 18O-H2O is usually used as target water. The target water should be recovered after synthesis and reused, because it is expensive, but recovered water contains impurities such as organic substances, and it must be purified before reuse. For this reason Sumitomo Heavy Industries, Ltd. developed an O-18 water purifier for elimination of organic substances in recovered water. This instrument consists of a UV irradiation unit and low-temperature distillation unit. Our institution had an opportunity to test use this instrument and evaluated its performance. The concentrations of organic substances after UV irradiation was greatly reduced, and recovery efficiency after distillation by the low-temperature distillation unit was very satisfactory at 99.3 +/- 0.5%. Furthermore, the yield of 18F-FDG from 18O-H20 purified with this instrument was sufficient for the clinical use.

[18F-FDG injections produced by a solid phase 18F-fluorination (FDG MicroLab): effects of 18F-FDG and the components on endotoxin and sterility tests]

Effects of 18F-FDG and components of the injections on endotoxin tests (Limulus tests) and sterility tests (Blood culture system) were determined with 18F-FDG injections produced by a solid phase 18F-fluorination (FDG MicroLab, GE). 18F-FDG injections with endotoxins shortened the time for gelling (turbidimetry), compared with that of the control (saline). Blood culture systems inoculated with 18F-FDG injections and microorganisms showed positive results within 72 h of incubation for every species of microorganisms used in the present study (Bacillus subtilis, Candida albicans, Clostridium sporogenes, Micrococcus luteus). These results were quite similar to those for the control samples inoculated with saline and the microorganisms. Consequently, 18F-FDG and the components of the injections produced by the present methods may not significantly affect the endotoxin tests and sterility tests.

A water-cooled spherical niobium target for the production of [18F]fluoride

A new automated target system for the routine production of [18F]fluoride from (18)O-enriched water has been constructed. It consists of a small spherical niobium target chamber mounted into a special holder, which provides rapid cooling by water flow around the sphere. The target is irradiated with 21 MeV protons; the incident energy in the target chamber is 13 MeV. The system is operated without external over-pressure and has been tested for beam currents up to 50 microA. 95% of the theoretical yield of [18F]fluoride has been extracted and used for the synthesis of [18F]2-fluoro-2-deoxy-D-glucose.

Preparation of fluorine-18 labelled sugars and derivatives and their application as tracer for positron-emission-tomography

The usefulness of 18F-labelled carbohydrates, especially 2-deoxy-2-[18F]fluoro-D-glucose, to study pathophysiological processes in man non-invasively using positron-emission-tomography (PET) led to a widespread investigation of different 18F-labelled sugars and sugar derivatives. In consideration of the short half-life of fluorine-18 (T(1/2) = 110 min) synthetic strategies concerning precursor design, labelling conditions and deprotection of the intermediate compounds were developed to guarantee an efficient high radiochemical yield synthesis for diagnostic purposes. Besides some aspects of medical application of 2-deoxy-2-[18F]fluoro-D-glucose, a few synthetic strategies are described reflecting development work on promising 18F-labelled sugars for diagnostic purposes during the last two decades.

[Synthesis of 18F-FDG with FDG MicroLab system: basic studies for clinical application]

We synthesized 18F-FDG by using an automated synthetic apparatus "FDG MicroLab" (GE Medical Systems) which produces 18F-FDG by a solid phase 18F-fluorination. Its quality and reproducibility were evaluated in order to assess feasibility of the apparatus for routine clinical production of 18F-FDG. For 5 consecutive 18F-FDG synthesis, target irradiation was carried out at 15 microA for 60 min. 18F-FDG was obtained in 50 min after EOB with an end-of-synthesis yield of 9.34 +/- 1.06 GBq. Radiochemical yield and radiochemical purity were 47 +/- 3% (decay corrected) and 98.0 +/- 0.5%, respectively. Other several quality control parameters tested conformed with "Standards of Compounds Labeled with Positron Nuclides" (RADIOISOTOPES, 44, 1995). Thus, the automated synthetic apparatus "FDG MicroLab" has proven to stably produce 18F-FDG with high yield and high purity. The apparatus is feasible for routine clinical production of 18F-FDG.