– By Kiel Strang, TRIUMF High School Fellowship Student
For the past 6 weeks I’ve been working for Dr. Conny Hoehr and TRIUMF’s Nuclear Medicine group. The main project I’ve been working on involves a new process for producing Technetium-94m (94mTc) with the TR13 cyclotron.
94mTc is a radioisotope used in PET imaging and has some properties that make it an attractive replacement for 99mTc, a commonly used imaging isotope that is now in short supply. When the positron emitted by 94mTc annihilates with an electron, it emits 2 gamma rays in opposite directions.
Detecting these in coincidence allows the position of the tracer molecule to be determined more precisely than is possible with the single gamma emitted by 99mTc, producing better image quality.
94mTc has been previously produced using solid molybdenum trioxide-94 (94MoO3) targets. Dr. Hoehr and her team are developing an alternate method of producing 94mTc using a liquid target filled with a solution of 94MoO3, ammonium hydroxide (NH4OH), hydrogen peroxide (H2O2) and water.
My role in this project was developing the software to control and automate handling of the target solution.
Using NI Lookout (http://sine.ni.com/nips/cds/view/p/lang/en/nid/12511), I developed a control interface for the process and automated the expected sequence of operations. I tried to make the interface easy to understand and operate, and flexible enough to allow for easy adjustment as the procedures are finalized.
As this is an experimental system, I tried to leave the operator lots of flexibility. In addition to the automated stages, the interface allows manual control of all the valves.
One of the most interesting challenges in developing the interface was controlling the syringe pump used to push solutions into the system. This pump has an integrated microcontroller that can be programmed with quite complex tasks, but the interface between the pump controller and the Lookout control software is very limited. There are 2 programmable input pins available and 1 pin, which starts or pauses the pump program.
The Lookout control program needs to be able to select any of 3 preset dispensing volumes (for filling the target, dispensing products, and purging the system). I did this using timing on one of the input pins – when the pump program is started, it will select a volume based on the length of time the pin is powered. The other programmable pin is used as an emergency stop signal.
Because this system is not expected to be assembled and run until the fall, I had to test each component individually. For the Lookout software, I created simulated inputs and indicators for the state of the outputs. I also tested the pump by manually connecting power to its input pins. These methods allowed me to verify that each component works as intended before the entire system is assembled.
I’ve been debating between studying Physics or Engineering Physics for a couple of years, but working at TRIUMF has shown me that an engineering education could be very valuable even if I eventually decide to pursue a career in physics.