Hydrophobic adsorbents such as C18 and C30 were coated with PEG and subsequently used for the separation of Mo/Tc. The most effective resin for adsorbing PEG was the C18-U resin, which demonstrated a coating capacity of 97.6±2.8mg PEG per g of resin. The ability to adsorb pertechnetate was proportional to the amount of PEG coated on the hydrophobic resin. The [(99m)Tc]pertechnetate recovery during the separation of cyclotron produced (99m)Tc from (100)Mo was 91.8±0.3% (n=2). The resultant product met relevant USP monograph specifications.

After the production of (99)mTc via the Mo-100(p,2n)Tc-99m reaction, there is a requirement for separating Tc-99m from bulk Mo-100. Although a number of separation methods have been demonstrated, the possibility of using a cartridge-based system is particularly attractive for routine use in a good manufacturing practice (GMP) regulatory environment. This study confirmed that hydrophobic interaction chromatography (HIC) solid phase extraction (SPE) with PEG as stationary phase is an efficient and easily automated method for separating molybdate and pertechnetate, and that PEG degradation in the conditions used does not affect the performance of the resin. In addition, reversed phase SPE using Waters Oasis (R) HLB shows promise for successful separation of molybdenum and technetium and work continues to extend this technology to readily available commercial SPE cartridges.

There is growing interest in the large scale cyclotron production of 99mTc via the 100Mo(p,2n)99mTc reaction. While the use and recycling of cyclotron-irradiated enriched molybdenum targets has been reported previously in the context of 94mTc production, to the best of our knowledge, previous recycling studies have been limited to the use of oxide targets. To facilitate reuse of high-power enriched 100Mo targets, this work presents and evaluates a strategy for recycling of enriched metallic molybdenum. For the irradiated 100Mo targets in this study, an overall metal to metal recovery of 87% is reported. Evaluation of "new" and "recycled" 100Mo revealed no changes in the molybdenum isotopic composition (as measured via ICP-MS). For similar irradiation conditions of "new" and "recycled" 100Mo, (i.e. target thicknesses, irradiation time, and energy), comparable levels of 94gTc, 95gTc, and 96gTc contaminants were observed. Comparable QC specifications (i.e. aluminum ion concentration, pH, and radiochemical purity) were also reported. We finally note that [99mTc]–MDP images obtained by comparing MDP labelled with generator-based 99mTc vs. 99mTc obtained following the irradiation of recycled 100Mo demonstrated comparable biodistribution. With the goal of producing large quantities of 99mTc, the proposed methodology demonstrates that efficient recycling of enriched metallic 100Mo targets is feasible and effective.

In accordance with the recommendations of the International Radiological Protection Commission, the current maximum acceptable radiation dose limits for members of the public have been reduced to 1 mSv in the United States, Canada, and European Union countries including the United Kingdom. This has had a significant impact on radiation protection guidelines for contacts of patients treated with 131I. Many previous recommendations have relied upon models which may overestimate dose rates at short distances. We therefore undertook measurements of 131I dose rates using adult and infant phantoms that more accurately reflected true geometry. Effective dose calculations and patient contact restrictions were then derived from these direct dose measurements. Doses received by the adult phantom were measured at three distances (contact, 1.0 m, 2.0 m) and doses received by the infant phantom were measured at contact in two orientations (adult cradling infant over shoulder and at waist). The doses measured were significantly lower than previously predicted for the adult and infant phantom. Our measurements suggest that patient contact restrictions could be made less stringent than those currently in widespread use.

UNLABELLED:Although 123I-IBZM is widely used as a D2 receptor imaging agent, image quality is compromised by a relatively low target-to-nontarget ratio. Animal studies suggest that 123I-epidepride (Kd 0.024 nM) may be superior to 123I-IBZM, but this agent has not been systematically studied in humans.METHODS:We directly compared 123I-epidepride and 123I-IBZM in five normal volunteers (age range 30-58 yr, mean 43 yr). Brain SPECT imaging was performed 2 hr after the 123I-IBZM injection (average dose 153 MBq). Iodine-123-epidepride scans were performed 1 hr (n = 3), 2 hr (n = 5) and 3 hr (n = 3) postinjection (average dose 149 MBq).RESULTS:Both radiopharmaceuticals were well tolerated. Iodine-123-epidepride provided excellent visualization of the striatum. Percent specific striatum uptake at 2 hr (71.7 +/- 4.9%) was much greater than with 123I-IBZM (32.6 +/- 5.3%, p < 0.01).CONCLUSION:Iodine-123-epidepride is a new D2 receptor agent that exhibits excellent neuroimaging properties and has a much higher affinity for striatal uptake than 123I-IBZM.

The normal biodistribution of Tc-99m pertechnetate includes the thyroid gland, salivary glands, choroid plexus, and gastric mucosa. The primary route of excretion is through renal clearance. The authors describe two cases in which hepatobiliary excretion of intravenously administered Tc-99m pertechnetate was observed during scanning for Meckel's diverticulum as a possible source of gastrointestinal bleeding.

Departments of 1 Radiopharmacy 2 Paediatrics 3 Nuclear Medicine, Health Sciences Centre, Winnipeg, Manitoba.

Technetium-99m radiopharmaceuticals prepared for routine clinical use, were labelled with [99mTc]pertechnetate obtained from either a commercial chromatographic generator or from a Winnipeg Health Sciences Centre semi-automated self-shielded methyl ethyl ketone extraction system. The [99mTc]pertechnetate source for each 99mTc radiopharmaceutical was selected at random over a 16 month period of time. The routine quality control data (silica-gel thin layer chromatography) was reviewed retrospectively, as an in vitro assessment of the quality of the [99mTc]radiopharmaceutical prepared from each [99mTc]pertechnetate source. Bone scans ([99mTc]pyrophosphate) and wall motion studies ([99mTc]red blood cells) were evaluated as an in vivo assessment of the [99mTc]pertechnetate used to label the pyrophosphate or red blood cells. The in vitro studies indicated no difference in the labelling efficiency and radiochemical purity of the 99mTc radiopharmaceuticals prepared from either source of [99mTc]pertechnetate and there was also no difference observed in the image quality of either bone scans or wall motion studies obtained with either source of [99mTc]pertechnetate.

SummaryRadionuclide imaging for the detection and localization of gastrointestinal bleeding is a highly sensitive and well-established clinical tool. 99 Tcm-labelled erythrocytes have permitted the recognition of intermittent bleeding up to 24 h following injection. However, free pertechnetate is actively secreted by gastric mucosa and can result in confounding gut activity. The possibility that pertechnetate may elute from the radiolabelled erythrocytes was investigated in an in vitro model. Blood samples from five subjects undergoing gated cardiac studies were labelled by modified in vivo, modified in vitro and pure in vitro methods and then incubated in serum for 24 h. Automated cell counts and instant thin layer chromatography were used to measure the physical and radiochemical stability of the labelled erythrocytes. No detectable haemolysis occurred and no free pertechnetate was released from the cells. However, an unexpected hydrophilic 99 Tcm species became detectable in the supernatant with a quantitative index which increased from an initial value of 0.016 ± 0.004 to 0.079 ± 0.012 at 24 h (P < 0.00001). This index did not differ among the three labelling methods. A chromatographically similar material was identified in the urine of a patient undergoing a gastrointestinal bleed study. The possibility of gut and/or hepatobiliary secretion of this material needs further clarification before delayed positive studies can be relied upon to indicate gastrointestinal bleeding.

S of the Society of Nuclear Medicine in Canada and Prairie Provinces Chapter, SNM Conjoint Meeting: PDF Only

S of the Society of Nuclear Medicine in Canada and Prairie Provinces Chapter, SNM Conjoint Meeting: PDF Only

The use of [99mTc]HMPAO for cerebral blood flow imaging has been hampered by the short useful life time of the labelled radiopharmaceutical. Preparation of [99mTc]HMPAO in 85% ethanol was found to increase the in vitro stability (92% radiochemical purity at 90 min) in comparison to the aqueous preparation (79% at 90 min). Biological distribution studies in mice indicated similar brain uptake (4.42 ± 1.02 and 4.12 ± 0.82% per gram at 20 min) and brain:blood ratio (0.97 ± 0.27 and 1.03 ± 0.20 at 20 min) of the ethanolic (2 h after preparation) and aqueous (15 min after preparation) formulations of [99mTc]HMPAO respectively. The improved in vitro stability of [99mTc]HMPAO prepared in 85% ethanol may prove useful in instances where previously the 30 min time limit precluded its use.

A procedure for the separation and recovery of arsenic radionuclides from a germanium oxide target using a liquid-liquid extraction technique is described. The effects of target material and preparation were investigated. The effects of hydrochloric acid and hydrogen peroxide concentration on germanium recovery were determined. The efficacy of various reducing agents were evaluated for recovery of arsenic. In addition, the effects of hydrochloric acid and reducing agent concentration were evaluated for optimum arsenic extraction conditions. The germanium oxide target material was recovered in greater than 97% yield in a form suitable for re-irradiation. The arsenic radionuclides were extracted in 99% radiochemical yield with less than 1% crossover contamination of germanium radionuclides.

Two formulations of [99mTc]sucralfate have been used to image gastric and duodenal ulcers and inflammatory bowel disease. One formulation is a complexation of [99mTc]HSA with sucralfate. The second is prepared by directly labeling sucralfate with [99mTc]pertechnetate in the presence of stannous ion. An in vitro study of the factors affecting the production and stability of these labeled sucralfate preparations was conducted. Both formulations were stable at the acidic pH likely encountered in the stomach. However, at pH greater than 6 the albumin-sucralfate complex began to dissociate while directly labeled sucralfate was stable to a pH of 9. Conversely it was shown that directly labeled sucralfate was more susceptible to loss of 99mTc to other chelating species. Sucralfate complexed with [99mTc]HSA was radiochemically stable up to a specific activity of 26 GBq (700 mCi) per gram while directly labeled sucralfate showed decreased 24-hr stability at specific activities greater than 837 mCi (31 GBq) per gram.

A facile procedure for the radiosynthesis of 3H- or 14C-labelled bromoacetate by reaction of sodium acetate with bromine in the presence of elemental sulfur is described. The effects of reaction time and temperature as well as bromine and sulfur concentration were investigated. Optimum conditions in which 1 mg sodium acetate (mass equivalent to 1 mCi (37 MBq) 14C) was allowed to react with 10 μL bromine and 0.1 mg sulfur at 105°C for 60 min afforded [14C]bromoacetate in greater than 90% radiochemical yield and [3H]bromoacetate in greater than 60% radiochemical yield based on initial 14C- or 3H-labelled sodium acetate concentration.