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Radiopharmaceutical Production. Radionuclide Transfer Transfer Considerations. STOP. Once the radionuclide is produced, it is necessary to get it from the cyclotron to the chemistry laboratory
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Radiopharmaceutical Production Radionuclide Transfer Transfer Considerations STOP
Once the radionuclide is produced, it is necessary to get it from the cyclotron to the chemistry laboratory If the radionuclide is in the form of a gas, the transfer can usually be done with pressure and perhaps a push gas In the radionuclide is a liquid, it must either be pushed with pressure or transported in some type of container If the radionuclide is a solid, then there must be some transport container or system to move the target from the cyclotron vault to the laboratory for processing. Contents Gas transfer Liquid transfer Solid target transfer Summary RadionuclideTransfer STOP
Gas Transfer The transfer of gases is relatively easy in that the target gas can usually be moved with a pressure differential Pressure 750 15 Closed Open Closed Open Click again and the exit valve will close, the entrance valve will open and the target will pressurize. After that the process can be repeated until all the activity is out of the target. In the simplest scenario, the gas pressure in the target is used to push the gas to the hot laboratory. An example of this operation is shown in the diagram at right. Click anywhere to start process. The valve out of the target will open and the target will empty into the vessel. The pressure will go to atmospheric
C-11 transfer line - 60 meters Transfer from the Cyclotron to the Chemistry Laboratory Although the distance to the lab can be quite long, the transfer of gases is usually easy CH3I Synthesis Box
The transfer of liquids is slightly more problematic since the liquid can break up in to many tiny droplets and result in an inefficient transfer. The picture on the top at right shows the ideal situation where there is a single bolus. The picture below shows the water breaking up into small segments which increases the pressure required to transfer the liquid and decreases the efficiency of transfer. Liquid Transfer
Flow Patterns - Two Phase System There several possible types of liquid and gas flow through a small bore line. These are shown in the diagram below along with the nomenclature. Pure Gas Flow Annular Flow Annular-Wavy Flow Slug Flow Plug Flow Bubble Flow As we go from pure gas flow, adding more and more liquid, we get these gradations in the type of flow through the tubing
F-18 transfer line Long distance F-18 Transfer As an example, to transfer liquid over a 60 meter distance, it was impossible to reliably transfer pure water.
Failure Modes The water had to be mixed with acetonitrile to reduce the surface tension and allow smooth transfer. The apparatus is shown on the next slide Mode 1 – Incomplete Transfer • The liquid is adhering to the walls of the tubing and the flow becomes annular • Contamination of the surface will raise the surface tension of plastic tubing and lower the surface tension of metal Mode 2 – Line Plugging • Many small boli at the beginning of the liquid train is worse that many small boli at the end of the train although the total force needed to push the liquid through should be the same • This is probably due to compressibility of gas boli in the liquid train
Helium in Vent 1 3 2 2 3 1 CO3-- O-18 from target MeCN rinse 2 Plug 5 6 4 6 4 5 Vent 1 3 3 1 2 2 Cleaning Water MeCN rinse 1 Resin Column Cleaning Water Recovery Mixing 5 5 4 6 6 4 O-18 recovery F-18 Recovery Procedure MeCN = acetonitrile Clean the station Extract F-18 onto resin with K2CO3 soln. Add MeCN to K2CO3 in mixing vessel Push through line to lab with He flow Rinse with pure MeCN The column never sees MeCN
The surface tension dominated regime refers to plug, slug and bubbly flow The shear dominated regime refers to annular, mist and annular wavy flow The surface tension determines the type of flow which will occur in the tubing Plug Flow Annular-Wavy Flow Transitions from one Flow pattern to another Low and high surface tension on a metal plate
Ammonia Synthesis Using DeVarda’s Alloy Another example of transfer of liquid is the production of N-13 ammonia using the DeVarda’s alloy method of converting nitrates into ammonia 13NH3 Water with [13N]Nitrates Flow of Helium Sterilizing Filter Vent Vacuum DeVarda’s Alloy NaOH Saline Solution
There many target used to produce radionuclides which use a solid target. These targets can be internal targets which stay inside the cyclotron during the irradiation or they can be mounted externally on the cyclotron or on a beam line. After the irradiation, these targets must be moved to the hot cells for processing. This can be done pneumatically or with a train or other carrier Solid Target Transfer
Metal Target Systems Solid target system for Siemens RDS 111 cyclotron Beamline on “OSCAR” superconducting cyclotron
Targetry System Cooling Gas (He: -20C) Cu Targets Beam Target Holder Cooling Water Collimator Irradiation Port Courtesy of Drs. Suzuki & Fukumura, NIRS
Solid Target Transfer Here is an example of a solid target transfer system where the target is moved using a cart and pulley system. It is mechanically very simple and therefore quite reliable Solid target is loaded into target holder At the end of the chute is a transport cart The transport cart is then moved along a track to the hot cell for processing After irradiation the target is dropped down a chute
Summary The transfer of radionuclides from the cyclotron to the chemistry lab can be quite simple or rather complex depending on the chemical and physical form of the target material. In gases, transfer is usually very simple with a pressure gradient being the driving force In liquids, the surface tension of the liquid and the distance over which the liquid must be transferred can be significant confounding factors in the transfer. Care must be taken to either keep the liquid from breaking up or to rinse the lines with a second bolus of liquid in order to transfer the maximum amount of activity. In solids, the targets are usually transferred using a mechanical system. The system may be as simple as a holder on a string, or as complex as a pneumatic transfer system with the ability to direct the target to several locations.
