Radiopharmaceutical Production - PowerPoint Presentation

Slide1

Radiopharmaceutical Production

Radionuclide TransferTransfer Considerations

STOP

RadionuclideTransfer

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 gasIn the radionuclide is a liquid, it must either be pushed with pressure or transported in some type of containerIf 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 transferSummary

STOP

Gas Transfer

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

Pressure

Closed

750

Closed

Open

15

Open

The transfer of gases is relatively easy in that the target gas can usually be moved with a pressure differential

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.

C-11 transfer line - 60 meters

CH

3

I Synthesis Box

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

Liquid Transfer

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.

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.

As we go from pure gas flow, adding more and more liquid, we get these gradations in the type of flow through the tubing

Pure Gas Flow

Annular Flow

Annular-Wavy Flow

Slug Flow

Plug Flow

Bubble Flow

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

Mode 1 – Incomplete TransferThe 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 metalMode 2 – Line PluggingMany 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 sameThis is probably due to compressibility of gas boli in the liquid train

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

F-18 Recovery Procedure

Clean the station

Extract F-18 onto resin with K2CO3 soln.Add MeCN to K2

CO

3

in mixing vessel

Push through line to lab with He flowRinse with pure MeCNThe column never sees MeCN

O-18 from target

1

3

2

6

4

5

6

4

5

3

1

2

1

3

2

4

6

5

3

1

2

6

4

5

Helium in

Vent

Plug

CO

3

--

Vent

O-18 recovery

MeCN

rinse 2

MeCN

rinse 1

Mixing

Cleaning

Water

Cleaning

Water

Recovery

Resin

Column

MeCN

=

acetonitrile

Transitions from one Flow pattern to another

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

Annular-Wavy Flow

Plug Flow

Low and high surface tension on a metal plate

Ammonia Synthesis Using

DeVarda’s

Alloy

Water with [

13

N]Nitrates

DeVarda’s Alloy

NaOH

Flow of Helium

Saline Solution

13

NH

3

Vent

Vacuum

Sterilizing

Filter

Another example of transfer of liquid is the production of N-13 ammonia using the

DeVarda’s

alloy method of converting nitrates into ammonia

Solid Target Transfer

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

Metal Target Systems

Beamline

on “OSCAR” superconducting cyclotron

Solid target system for Siemens RDS 111 cyclotron

Cu Targets

Beam

Cooling Gas

(He: -20



C)

Target Holder

Targetry System

Collimator

Cooling Water

Irradiation Port

Courtesy of Drs. Suzuki &

Fukumura

, NIRS

Solid Target Transfer

Solid target is loaded into target holder

After irradiation the target is dropped down a chute

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

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

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 forceIn 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.

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