FDG Solution Research Articles

Evaluation of Physiochemical and Microbiological Stability of 2-[18F] Fluoro-2-Deoxy-D-Glucose, [18F]FDG: Synthesized in the Cyclotron Facility of National Institute of Nuclear Medicine and Allied Sciences

2-[18F]Fluoro-2-Deoxy-D-Glucose ([18F]FDG) is very effective and the most successful radiotracer for the assessment of glucose metabolism in the brain, heart, and lungs. It has also been used for imaging different tumors in oncology. The purpose of this study was to evaluate the stability and quality of [18F]FDG synthesized by the newly installed 18MeV Cyclotron facility at the National Institute of Nuclear Medicine and Allied Sciences (NINMAS). [18F]FDG was synthesized by nucleophilic fluorination of Mannose-triflate followed by basic hydrolysis with an IBA Synthera® auto synthesizer. [18F]FDG solution was collected in a sterilized vial after the filtration by a vented Millex®-GS 0.22µm syringe-driven hydrophilic filter. An aliquot of [18F]FDG solution was taken 0, 2, 4, 6, and 8 hours after the synthesis. All quality control parameters were measured in the first evaluated period, immediately (i.e., 0 hours) after synthesis. Radiochemical purity (RCP) was measured for all [18F]FDG samples and for all time points. The radiochemical and radionuclidic purity was more than 95% and 99.99% respectively. The [18F]FDG was physiochemically & microbiologically stable over 8 hours. Bangladesh J. Nuclear Med. 26(1): 44-50, 2023

Ultrasound-based sensors for respiratory motion assessment in multimodality PET imaging

Breathing motion can displace internal organs by up to several cm; as such, it is a primary factor limiting image quality in medical imaging. Motion can also complicate matters when trying to fuse images from different modalities, acquired at different locations and/or on different days. Currently available devices for monitoring breathing motion often do so indirectly, by detecting changes in the outline of the torso rather than the internal motion itself, and these devices are often fixed to floors, ceilings or walls, and thus cannot accompany patients from one location to another. We have developed small ultrasound-based sensors, referred to as ‘organ configuration motion’ (OCM) sensors, that attach to the skin and provide rich motion-sensitive information. In the present work we tested the ability of OCM sensors to enable respiratory gating during in vivo PET imaging. A motion phantom involving an FDG solution was assembled, and two cancer patients scheduled for a clinical PET/CT exam were recruited for this study. OCM signals were used to help reconstruct phantom and in vivo data into time series of motion-resolved images. As expected, the motion-resolved images captured the underlying motion. In Patient #1, a single large lesion proved to be mostly stationary through the breathing cycle. However, in Patient #2, several small lesions were mobile during breathing, and our proposed new approach captured their breathing-related displacements. In summary, a relatively inexpensive hardware solution was developed here for respiration monitoring. Because the proposed sensors attach to the skin, as opposed to walls or ceilings, they can accompany patients from one procedure to the next, potentially allowing data gathered in different places and at different times to be combined and compared in ways that account for breathing motion.

The role of activity, scan duration and patient\u2019s body mass index in the optimization of FDG imaging protocols on a TOF-PET/CT scanner

BackgroundTime-of-flight (TOF) PET technology determines a reduction in the noise and improves the reconstructed image quality in low count acquisitions, such as in overweight patients, allowing a reduction of administered activity and/or imaging time. However, international guidelines and recommendations on the 18F-fluoro-2-deoxyglucose (FDG) activity administration scheme are old or only partially account for TOF technology and advanced reconstruction modalities.The aim of this study was to optimize FDG whole-body studies on a TOF-PET/CT scanner by using a multivariate approach to quantify how physical figures of merit related to image quality change with acquisition/reconstruction/patient-dependent parameters in a phantom experiment.MethodsThe NEMA-IQ phantom was used to evaluate contrast recovery coefficient (CRC), background variability (BV) and contrast-to-noise ratio (CNR) as a function of changing emission scan duration (ESD), activity concentration (AC), target internal diameter (ID), target-background activity ratio (TBR) and body mass index (BMI). The phantom was filled with an average concentration of 5.3 kBq/ml of FDG solution and the spheres with TBR of 21.2, 8.8 and 5.0 in 3 different sessions. Images were acquired at varying background activity concentration from 5.1 to 1.3 kBq/ml, and images were reconstructed for ESD of 30–151 s per bed position with and without point spread function (PSF) correction. The parameters were all considered in a single analysis using multiple linear regression methods.ResultsAs expected, CRC depended only on sphere ID and on PSF application, while BV depended on sphere ID, ESD, AC and BMI of the phantom, in order of decreasing relevance. Noteworthy, ESD and AC resulted as the most significant predictors of CNR variability with a similar relevance, followed by the BMI of the patient and TBR of the lesion.ConclusionsAC and ESD proved to be effective tools in modulating CNR. ESD could be increased rather than AC to improve image quality in overweight/obese patients to fulfil ALARA principles.

Using EQ·PET to reduce reconstruction-dependent variations in [18F]FDG-PET brain imaging

This study aims at assessing whether EANM harmonisation strategy combined with EQ·PET methodology could be successfully applied to harmonize brain 2-deoxy-2[18F]fluoro-D-glucose ([18F]FDG) positron emission tomography (PET) images.The NEMA NU 2 body phantom was prepared according to the EANM guidelines with an [18F]FDG solution. Raw PET phantom data were reconstructed with three different reconstruction protocols frequently used in clinical PET brain imaging: () Ordered subset expectation maximization (OSEM) 3D with time of flight (TOF), 2 iterations and 21 subsets; () OSEM 3D with TOF, 6 iterations and 21 subsets; and () OSEM 3D with TOF, point spread function (PSF), and 8 iterations and 21 subsets. EQ·PET filters were computed as the Gaussian smoothing that best independently aligned the recovery coefficients (RCs) of reconstructions and with the RCs of the reference reconstruction, . The performance of the EQ·PET filter to reduce variations in quantification due to differences in reconstruction was investigated using clinical PET brain images of 35 early-onset Alzheimer’s disease (EOAD) patients. Qualitative assessments and multiple quantitative metrics on the cortical surface at different scale levels with or without partial volume effect correction were evaluated on the [18F]FDG brain data before and after application of the EQ·PET filter.The EQ·PET methodology succeeded in finding the optimal smoothing that minimised root-mean-square error (RMSE) calculated using human brain [18F]FDG-PET datasets of EOAD patients, providing harmonized comparisons in the neurological context. Performance was superior for TOF than for TOF + PSF reconstructions.Results showed the capability of the EQ·PET methodology to minimize reconstruction-induced variabilities between brain [18F]FDG-PET images. However, moderate variabilities remained after harmonizing PSF reconstructions with standard non-PSF OSEM reconstructions, suggesting that precautions should be taken when using PSF modelling.

One-step conjugation of glycylglycine with [18F]FDG and a pilot PET imaging study

This study describes a single step conjugation of Glycylglycine (GlyGly) which is a small peptide, with [18F]FDG via oxime formation. Amiooxy-functionalization of GlyGly (AO-GlyGly) was accomplished through the reaction of Boc-aminooxy succinimide ester. Conjugation reaction was performed at 100 °C for 30 min in a vial containing AO-GlyGly and [18F]FDG solution. The radiolabeled product ([18F]FDG-GlyGly) was obtained with 98.65 ± 0.35% yield without any purification step which makes this method more attractive for 18F radiolabeling. The present study is concluded with an in vivo pilot animal PET study to assess biodistribution and kinetics of chemoselectively [18F]FDG tagged GlyGly in vivo.

Imaging of photoassimilates transport in plant tissues by positron emission tomography

AbstractThe current findings show that positron emission tomography (PET), primarily developed for medical diagnostic imaging, can be applied in plant studies to analyze the transport and allocation of wide range of compounds labelled with positronemitting radioisotopes. This work is focused on PET analysis of the uptake and transport of 2-deoxy-2-fluoro[18F]-D-glucose (2-[18F]FDG), as a model of photoassimilates, in tissues of giant reed (Arundo donax L. var. versicolor) as a potential energy crop. The absorption of 2-[18F]FDG and its subsequent transport in plant tissues were evaluated in both acropetal and basipetal direction as well. Visualization and quantification of the uptake and transport of 2-[18F]FDG in plants immersed with the root system into a 2-[18F]FDG solution revealed a significant accumulation of 18F radioactivity in the roots. The transport rate in plants was increased in the order of plant exposure through: stem > mechanically damaged root system > intact root system. PET analysis in basipetal direction, when the plant was immersed into the 2-[18F]FDG solution with the cut area of the leaf of whole plant, showed minimal translocation of 2-[18F]FDG into the other plant parts. The PET results were verified by measuring the accumulated radioactivity of18F by direct gamma-spectrometry.

Partial volume correction of brain PET studies using iterative deconvolution in combination with HYPR denoising

BackgroundAccurate quantification of PET studies depends on the spatial resolution of the PET data. The commonly limited PET resolution results in partial volume effects (PVE). Iterative deconvolution methods (IDM) have been proposed as a means to correct for PVE. IDM improves spatial resolution of PET studies without the need for structural information (e.g. MR scans). On the other hand, deconvolution also increases noise, which results in lower signal-to-noise ratios (SNR). The aim of this study was to implement IDM in combination with HighlY constrained back-PRojection (HYPR) denoising to mitigate poor SNR properties of conventional IDM.MethodsAn anthropomorphic Hoffman brain phantom was filled with an [18F]FDG solution of ~25 kBq mL−1 and scanned for 30 min on a Philips Ingenuity TF PET/CT scanner (Philips, Cleveland, USA) using a dynamic brain protocol with various frame durations ranging from 10 to 300 s. Van Cittert IDM was used for PVC of the scans. In addition, HYPR was used to improve SNR of the dynamic PET images, applying it both before and/or after IDM. The Hoffman phantom dataset was used to optimise IDM parameters (number of iterations, type of algorithm, with/without HYPR) and the order of HYPR implementation based on the best average agreement of measured and actual activity concentrations in the regions. Next, dynamic [11C]flumazenil (five healthy subjects) and [11C]PIB (four healthy subjects and four patients with Alzheimer’s disease) scans were used to assess the impact of IDM with and without HYPR on plasma input-derived distribution volumes (VT) across various regions of the brain.ResultsIn the case of [11C]flumazenil scans, Hypr-IDM-Hypr showed an increase of 5 to 20% in the regional VT whereas a 0 to 10% increase or decrease was seen in the case of [11C]PIB depending on the volume of interest or type of subject (healthy or patient). References for these comparisons were the VTs from the PVE-uncorrected scans.ConclusionsIDM improved quantitative accuracy of measured activity concentrations. Moreover, the use of IDM in combination with HYPR (Hypr-IDM-Hypr) was able to correct for PVE without increasing noise.

Improving CT-Based PET Attenuation Correction in the Vicinity of Metal Implants by an Iterative Metal Artifact Reduction Algorithm of CT Data and Its Comparison to Dual-Energy-Based Strategies: A Phantom Study.

The aim of this study was to evaluate the potential of iterative metal artifact reduction (IMAR) for the improvement of computed tomography (CT)-based position emission tomography (PET) attenuation correction in the vicinity of metal implants and compare it with dual-energy-based metal artifact reduction strategies. A dedicated dental phantom was constructed consisting of a cylindrical tube filled with [18-F]FDG solution (5300 mL and 50.9 MBq) containing 2 artificial jaws with 1 nonprecious alloy fixed dental prosthesis and 3 single tooth crowns in the lower jaw.Computed tomography measurements of the phantom were acquired on a stand-alone dual-energy CT scanner equipped with IMAR capabilities. A series of 24 CT data sets were obtained using different scan parameters and monoenergetic extrapolation of dual-energy CT acquisitions with and without IMAR reconstruction.Position emission tomography measurements of the phantom were performed on a state-of-art PET/CT scanner. Position emission tomography data were reconstructed using all 24 previously acquired CT data sets.Relative errors in the quantification of activity concentrations using the different CT scanning and reconstruction parameters were quantified by placement of regions of interest within the phantom. Metal artifacts of different extent were observed in all CT data sets. A marked reduction in CT metal artifacts was observed using IMAR. In general, activity concentrations were overestimated/underestimated in areas of high/low-density metal artifacts, respectively.Relative errors in PET quantification ranged between -71% and +70% without IMAR. Using IMAR, these errors were reduced to a range between -40% and +12%. Averaged absolute values of relative PET quantification errors were 27% and 7% without and with the use of IMAR (P < 0.001), respectively. Iterative metal artifact reduction was superior compared with dual-energy-based metal artifact reduction strategies, and the combination of both strategies did not result in further significant improvement of PET quantification. The use of IMAR in PET/CT is a promising approach for markedly improving image quality and PET quantification in the vicinity of metal implants. Further clinical studies are necessary to assess the clinical performance of this algorithm in patients.

A two-center study for the quality control of [(18)F]FDG using FASTlab phosphate cassettes.

The GE FASTlab radiosynthesis module is routinely used for the production of [(18)F]FDG, utilizing the commercially available phosphate cassettes. Because of the observation of a white precipitate in the product vial before the product expiry time, we re-examined the quality of the produced [(18)F]FDG solution. Phosphate buffered [(18)F]FDG solution was synthesized on the FASTlab and analyzed at both National Taiwan University Hospital (NTUH) of Taiwan and Royal Brisbane and Women's Hospital (RBWH) of Australia. In addition to the standard product quality control (QC), the concentration of aluminum (Al(3+)) as probable cause of the precipitations in the [(18)F]FDG solution was analyzed by inductively coupled plasma mass spectrometry (ICP-MS at RBWH) and inductively coupled plasma optical emission spectrometry (ICP-OES at NTUH), and using three semi-quantitative methods at NTUH, Advantec(®) Alumi Check Test Strip, Quantofix(®) Aluminum Test Strip and MColortest™ Aluminum Test kit. The precipitates were observed in the [(18)F]FDG solution within 24 (NTUH) and 6 (RBWH) hours after the end of synthesis in 38-100% of the batches, dependent on the batch of the FASTlab cassettes. Addition of metal-free HCl(aq) to aliquots of [(18)F]FDG containing precipitate, followed by ICP-MS analysis revealed Al(3+) concentrations of 70-80ppm. Al(3+) concentrations of 10-12ppm were detected in [(18)F]FDG batches that did not show any precipitation. In contrast, less than 5ppm of the residual Al(3+) was detected by semi-quantitative methods in all batches. The US (USP), British (BP), European (EP) and Japanese (JP) pharmacopeias demand that [(18)F]FDG for injection should be clear and particulate free within the given shelf-life/expiration time. To avoid Al-phosphate precipitation within the product expiry time, FASTlab citrate cassettes, rather than phosphate cassettes, should be used for [(18)F]FDG production. Although testing for Al(3+) is not listed in the [(18)F]FDG monographs of the USP, BP and EP, residual Al(3+) levels should be considered in the interests of patient safety.

WE-E-201C-09: Intravascular Imaging with Storage Phosphor Detector

Purpose: To develop and test an intravascular positronimagingsystem based on a storage phosphor (SP) detector for imaging vulnerable plaques of human coronary arteries.Materials and methods: The positron‐emitting radiotracer F18‐FDG accumulates in vulnerable arterial plaques with inflamed overlying cap; thus vulnerable plaques could be imaged by an intravascular positrondetector located at the end of a cardiac catheter. An experimental intravascular imaging detector was constructed as a SP tube with 55 mm length, 2 mm diameter, and 0.28 mm wall thickness. A light diffuser with 0.9 mm diameter and 55 mm length is inserted into the SP tube to erase signal accumulated in the SP during fluoroscopic guidance of catheter insertion. The light diffuser was connected to a 0.38 W laser source through a 2 m long optical fiber. A heart phantom with 300 cm3 volume, and 3.2 mm diameter coronary arteries with plaques was fabricated. 0.5 μCi/cm3 FDG solution filled the heart and coronary arteries, with a range of activities in the plaques. The detector was inserted in a coronary artery and the plaques were imaged for 2 min. The detector was extracted and read out in 2 min using a SP reader. Results: The light diffuser erased the fluoroscopic x‐ray signal of the SP to background levels. Vulnerable plaques with area activities of 1.2 nCi/mm2 and higher were visualized. This activity is a factor of 10 lower than that expected in human vulnerable plaques. The detector can image the internal surface of 50 mm long vessels with 0.6 mm FWHM spatial resolution in a single measurement. The detector is flexible, easy to handle, and provides virtually real time imaging. Conclusion: The intravascular detector provides sensitivity, spatial resolution, flexibility, and imaging times that are well suited for clinical imaging of vulnerable plaques of human coronary artery.

Intravascular imaging with a storage phosphor detector

The aim of this study is to develop and test an intravascular positron imaging system based on a storage phosphor detector for imaging and detecting vulnerable plaques of human coronary arteries. The radiotracer F18-FDG accumulates in vulnerable plaques with inflammation of the overlying cap. The vulnerable plaques can, therefore, be imaged by recording positrons emitted from F18-FDG with a detector inserted into the artery. A prototype intravascular detector was constructed based on storage phosphor. The detector uses a flexible storage phosphor tube with 55 mm length, 2 mm diameter and 0.28 mm wall thickness. The intravascular detector is guided into the vessel using x-ray fluoroscopy and the accumulated x-ray signal must be erased prior to positron imaging. For this purpose, a light diffuser, 0.9 mm in diameter and 55 mm in length, was inserted into the detector tube. The light diffuser was connected to a laser source through a 2 m long optical fiber. The diffuser redirected the 0.38 W laser light to the inner surface of the phosphor detector to erase it. A heart phantom with 300 cm3 volume and three coronary arteries with 3.2 mm diameter and with several plaques was constructed. FDG solution with 0.5 µCi cm−3 activity concentration was filled in the heart and coronary arteries. The detector was inserted in a coronary artery and the signal from the plaques and surrounding background activity was recorded for 2 min. Then the phosphor detector was extracted and read out using a storage phosphor reader. The light diffuser erased the signal resulting from fluoroscopic exposure to level below that encountered during positron imaging. Vulnerable plaques with area activities higher than 1.2 nCi mm−2 were visualized by the detector. This activity is a factor of 10–20 lower than that expected in human vulnerable plaques. The detector was able to image the internal surface of the coronary vessels with 50 mm length and 360° circumference. Spatial resolution was 0.6–1.2 mm FWHM with a readout pixel resolution of 80 µm. The detector is flexible, reusable and easy to handle; it provides virtually real-time imaging. An intravascular imaging detector based on storage phosphor has shown a potential for imaging human coronary artery plaques. The detector provides the sensitivity, spatial resolution, flexibility and short imaging times necessary for clinical applications. Future research will decrease the detector diameter from 2 mm to 1 mm, and will apply the design to in vivo animal experiments.

FPGA Electronics for OPET: A Dual-Modality Optical and Positron Emission Tomograph.

The development of a prototype dual-modality optical and PET (OPET) small animal imaging tomograph is underway in the Crump Institute for Molecular Imaging at the University of California Los Angeles. OPET consists of a single ring of six detector modules with a diameter of 3.5 cm. Each detector has an 8 × 8 array of optically isolated BGO scintillators which are coupled to multichannel photomultiplier tubes and open on the front end. The system operates in either PET or optical mode and reconstructs the data sets as 3D tomograms. The detectors are capable of detecting both annihilation events (511 keV) from PET tracers as well as Single Photon Events (SPEs) (2-3 eV) from bioluminescence. Detector channels are readout using a custom multiplex readout scheme and then filtered in analog circuitry using either a γ-ray or SPE specific filter. Shaped pulses are sent to a Digital Signal Processing (DSP) unit for event processing. The DSP unit has 100 MHz Analog-to-Digital Converters on the front-end which send digitized samples to Field Programmable Gate Arrays which are programmed via user configurable algorithms to process PET coincidence events or bioluminescence SPEs. Information determined using DSP includes: event timing, energy determination-discrimination, position determination-lookup, and coincidence processing. Coincidence or SPE events are recorded to an external disk and minimal post processing is required prior to image reconstruction. Initial imaging results from a phantom filled with 18FDG solution and an optical pattern placed on the front end of a detector module in the vicinity of a SPE source are shown.

Positron autoradiography for intravascular imaging: feasibility evaluation

Approximately 70% of acute coronary artery disease is caused by unstable (vulnerable) plaques with an inflammation of the overlying cap and high lipid content. A rupturing of the inflamed cap of the plaque results in propagation of the thrombus into the lumen, blockage of the artery and acute ischaemic syndrome or sudden death. Morphological imaging such as angiography or intravascular ultrasound cannot determine inflammation status of the plaque. A radiotracer such as 18F-FDG is accumulated in vulnerable plaques due to higher metabolic activity of the inflamed cap and could be used to detect a vulnerable plaque. However, positron emission tomography (PET) cannot detect the FDG-labelled plaques because of respiratory and heart motions, small size and low activity of the plaques. Plaques can be detected using a miniature particle (positron) detector inserted into the artery. In this work, a new detector concept is investigated for intravascular imaging of the plaques. The detector consists of a storage phosphor tip bound to the end of an intravascular catheter. It can be inserted into an artery, absorb the 18F-FDG positrons from the plaques, withdrawn from the artery and read out. Length and diameter of the storage phosphor tip can be matched to the length and the diameter of the artery. Monte Carlo simulations and experimental evaluations of coronary plaque imaging with the proposed detector were performed. It was shown that the sensitivity of the storage phosphor detector to the positrons of 18F-FDG is sufficient to detect coronary plaques with 1 mm and 2 mm sizes and 590 Bq and 1180 Bq activities in the arteries with 2 mm and 3 mm diameters, respectively. An experimental study was performed using plastic tubes with 2 mm diameter filled with an FDG solution, which simulates blood. FDG spots simulating plaques were placed over the surface of the tube. A phosphor tip was inserted into the tube and imaged the plaques. Exposure time was 1 min in all simulations and experiments. Experiments showed that detecting the coronary plaques using the proposed technique is possible. The proposed technique has the potential for fast and accurate detection of vulnerable coronary and other intravascular plaques.

Autoradiolysis of the 2-deoxy-2-[18F]fluoro-D-glucose radiopharmaceutical

To control virtually the toxic compounds and to improve quality control of the solution of 2-deoxy-2-[18F]fluoro-d-glucose (2-[18F]FDG), the products of its autoradiolysis were analyzed by high-performance liquid chromatography with electrospray mass spectrometric and radiometric detectors (HPLC/MS/RAD), thin layer chromatography on TLC silica plate and HPTLC on amino modified silica plate. Except Kryptofix™ 2.2.2, glucose and fluoride anion, no by-products and impurities were observed by LC/MS analysis of fresh 2-[18F]FDG samples. The analysis performed in the time interval of 6 to 48 hours after the end of 2-[18F]FDG synthesis indicated that the activity of the autoradiolysis products separated by HPLC did not exceed 1.3%. As the main autoradiolysis products of 3.3 . 10-5 to 4.4 . 10-5M 2-[18F]FDG solution of original specific activity 0.5-1.5 GBq . cm-3 were established: arabinose - 2.8 μM (G= 0.07/100 eV), gluconic and glucuronic acids 1.8-0.5 μM (G =0.01-0.05/100 eV), arabinose and araburonic acids occurred under 0.5 μM concentration at residual glucose contents about 0.14 mM. Radiation chemical yields of active products were calculated from molar activity of 2-[18F]FDG and the percentage of their activity: 0.5% radiochemical yield of 2-[18F]fluoroglucuronic acid corresponds to the G = 0.004/100 eV and 0.3% yield of 2-[18F]fluorogluconic acid issues G = 0.003/100 eV.

Artifacts from implanted leads in cardiac PET using CT-based attenuation correction

Conclusion: The LV EF and volumes are comparable in patients with and without type II DM in the absence of ischemia or infarction. The LV volumes and EF are lower in women than men in the presence or absence of DM. It is possible that ischemia/infarction affect more adversely the LV function in DM accounting for the worse LV function [and worse outcome] in patients with established CAD. Background: The use of CT-based attenuation correction (CT-AC) in cardiac PET can potentially cause artifacts, not just due to respiratory phase mismatch, but also due to implanted metallic leads. The significance of such metallic lead artifacts requires investigation. Methods: PET images of phantoms containing pacemaker leads and ICD leads in uniform FDG solution were acquired and analyzed. The leads were mounted in 90-degree bent configurations, allowing the magnitude of the artifact to be assessed when the lead is normal to or parallel to the transaxial planes. FDG cardiac PET studies of patients having implanted pacemaker (n=4) or ICD leads (n=4) were also analyzed. In all cases, images were acquired on both dedicated PET and PET-CT scanners, to compare differences of transmission sources vs. reduced-dose 120kVp “slow” CT for attenuation correction. Results: The magnitude of artifact depends on several factors: composition, design, and location. Unlike internal conductor wires (of low atomic number metal), external platinum alloy electrodes are much more likely to cause artifacts. Pacemaker leads, which have relatively small electrodes, caused noticeable artifacts in CT images but not in the resultant CT-AC PET or the dedicated PET images. ICD leads, which have much larger electrodes (shock coils), did cause significant regional artifacts in CT-AC PET images, but not in dedicated PET images. The apparent increase in FDG concentration from ICD metal artifact was on the order of 80% for phantom images (with the lead oriented in-plane) and 30% in patient myocardial images. Clinically significant artifacts were observed when the ICD lead was implanted adjacent to the left ventricle, but not when adjacent to the right ventricle. Conclusions: ICD leads can produce clinically significant artifacts in CT-AC cardiac PET, depending on their position and orientation, whereas pacemaker leads do not. Automated methods to correct for metal artifact would be beneficial, since the prevalence of implanted ICDs in patients undergoing cardiac PET is likely to rise. These results also may have implications for CT-AC cardiac SPECT imaging.

Production of 2-[18F]Fluoro-2-deoxy-D-glucose at the Laboratory of Radiochemistry, University of Helsinki

Production 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) was started at the Laboratory of Radiochemistry in 1998 when a cyclotron, specially designed for the production of short-lived positron emitters, was bought to the laboratory. The radiosynthesis of [18F]FDG is based on aminopolyether-mediated nucleophilic fluorination. [18F]Fluoride is produced by the 18O(p,n)18F nuclear reaction. [18F]FDG is synthesised with an automated device. The radiochemical yield of the synthesis is 50% (by the end of bombardment). Sterile and isotonic [18F]FDG solution is produced within 55 min. [18F]FDG is delivered for patient use by the medical company MAP Medical Technologies.

Thin layer chromatographic detection of Kryptofix 2.2.2 in the routine synthesis of [ 18F]2-fluoro-2-deoxy- d-glucose

A simple procedure for the detection of 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo (8.8.8) hexacosane (Kryptofix 2.2.2) in the final solution of [ 18F]FDG prepared by the aminopolyether supported nucleophilic substitution of 1,3,4,6-tetra-O-acetyl 2-O-trifluoromethanesulfonyl-β- d-mannopyranose (Hamacher et, al., 1986) has been developed. Presence of Kryptofix 2.2.2 in the routine production of [ 18F]FDG was detected using methanol/ammonium hydroxide (9:1) solvent system. A method to remove Kryptofix from [ 18F]FDG solution has been suggested.