Alchemy with Short-Lived Radionuclides

S INCE Bolwig and Lassen 1 reported a procedure by which the water extraction fraction (WEF) in rat brain could be measured, various methodological improvements have been made. In these methods, however, the carotid artery is cannulated to introduce the tracers.w Cerebral blood flow (CBF) may change during cannulation or injection of tracers, and hence, changes in WEF may occur. Even using relatively new methods with i.v. injection of pHlwater, 4 -* rats must be sacrificed to measure the brain concentration of radioactive water. Moreover, overestimation of WEF is expected because of the difference in washout rates of the water and the reference tracer 5 or because of the difficulty in measuring intraparenchymal [ 3 H] water separately from the intravascular tracer. 46 We previously reported a model and an operational equation (Equation 2) to estimate WEF after i.v. injections of radioactive water and reference tracer, when CBF and cerebral blood volume (CBV) are known. 78This method does not require knowing the absolute concentrations of radioactivity in the arterial blood and brain, as arterial curves and total count rates from the brain are sufficient. Isotopic decay is explicitly incorporated in the operational equation. We have also developed an experimental system to measure the coincidence counts from positron-emitting tracers in the head and the artery, with 2 pairs of external detectors. 9These prerequisites, in conjunction with the successful synthesis of ["C]butanol, 10 encouraged us to develop a new method for determining WEF in rats, without carotid injection and without sacrifice.

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“…12 The specific activity of the H 2 13 O was 0.75 mCi//il of H 2 O when delivered at approximately 120 seconds after the end of bombardment.…”

Section: Radiopharmaceuticalsmentioning

confidence: 95%

Water extraction fraction and permeability-surface product after intravenous injection in rats.

Takagi¹,

Ehara²,

Finn

1987

Stroke

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“…At 26 MeV the reported saturation yield in a gas target is quite large [100mCi//~A (Sajjad et al, 1985)]. The feasibility of making medically useful quantities of ~50-agents by the ~60(p,pn) reaction with a CS-30 cyclotron has been demonstrated previously using gas targets (Beaver et al, 1976;Fernandez-Rubio et al, 1981). Using somewhat higher proton energies (29 MeV) in a gas target Ruth (1985) has also produced large amounts of [~50]O2 (30 mCi/#A at saturation) by this reaction.…”

Section: Introductionmentioning

confidence: 99%

Direct simultaneous production of [15O]water and [13N]ammonia or [18F]fluoride ion by 26 MeV proton irradiation of a double chamber water target

Mulholland

Kilbourn²,

Moskwa³

1990

International Journal of Radiation Applications and Instrumenta

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A simple double liquid chamber target was developed to provide the option for simultaneous production of [15O]H2O and either 13N or 18F using a single proton beam. Irradiation of natural water in a thin aluminium front chamber produced [15O]H2O by the 16O(p, pn)15O reaction directly. Large (0.5-1.0 Ci) doses of sterile [15O]H2O (greater than 99.95% radionuclide purity) were routinely prepared in 1 min from end of 20 microA bombardments using this target and an in-line mixed bed ion exchange column purification. Water in the thin front chamber degraded proton energies on exit to 20-18 MeV. The rear silver liquid chamber was threefold thick to 17 MeV protons in water and it efficiently produced either 13N by the 16O(p, alpha)13N reaction or [18F]fluoride ion by the 18O(p, n)18F reaction. Both target chambers were overpressurized with at least 6 atm of gas to minimize boiling/cavitation of water at high beam currents. Using hydrogen as the overpressure gas on the back chamber and an in-line anion exchange column radionuclidic cleanup process, high yields of sterile, aqueous [13N]NH3 (40-200 mCi; 20 microA) were produced directly from the back chamber at the same time that [15O]H2O was being produced from the front chamber. The combination of this target system with a cyclotron capable of generating 26-30 MeV protons provides great flexibility and simplicity for rapid, high volume production of the three best validated and most widely used radiopharmaceuticals at the present time in clinical positron emission tomography: [15O]H2O, [13N]NH3 and [18F]FDG.

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Quality Assurance and Quality Control of Short-Lived Radiopharmaceuticals for PET

Meyer¹,

Coenen²,

Waters³

et al. 1993

Radiopharmaceuticals for Positron Emission Tomography

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Alchemy with Short-Lived Radionuclides

Cited by 7 publications

References 2 publications

Water extraction fraction and permeability-surface product after intravenous injection in rats.

Water extraction fraction and permeability-surface product after intravenous injection in rats.

Direct simultaneous production of [15O]water and [13N]ammonia or [18F]fluoride ion by 26 MeV proton irradiation of a double chamber water target

Quality Assurance and Quality Control of Short-Lived Radiopharmaceuticals for PET

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