Improvements in nuclear medicine in the last 15 years have seen the widespread introduction of new techniques and imaging capabilities, and consequently, manufacturers from the USA, Europe, Japan and Korea are developing and delivering more sophisticated equipment which further demands new techniques in radiation protection.
Radiation protection is driven by the A.L.A.R.A principle (“As Low As Reasonably Achievable”). To satisfy the rules and regulations imposed by legislators, hospital radiation personnel have to be monitored continuously to adhere to these standards.
Automated infusion systems for PET were introduced as an attempt to minimise radiation exposure to personnel operating in PET facilities and nuclear medicine departments. We refer to these devices as a “mini hot lab on wheels” including a basic isotope dose calibrator, infusion pump, syringe pump, PC & microprocessing power with a multi-dispensing capability being the basic description of an automatic system (but with some limitations).
Automatic infusion systems are normally loaded in the nuclear medicine department with a multi-dose vial of [F-18]-FDG containing the radioisotope produced at the cyclotron facility. These systems have been designed to deliver only (F-18 = 511 keV), introducing a limitation and inconvenience to the nuclear medicine department in regards to dispensing and administering other isotopes.
Other radioisotopes such as Tc-99m, Ga-67, Ga-68 and Lu-177 still need to be injected manually by the technologist, in a way deviating from the purpose of minimising the radiation dose to the operator and totally disregarding the ALARA principle.
What is permitted today in terms of allowed radiation doses to personnel was totally overlooked 40 years ago and may well be totally different again in another 40 years from today. Therefore, we should strive to take all efforts possible to minimise the radiation exposure to the operators, and not just adhere to the contemporary guidelines.
In conclusion, an automatic injection infusion system only partially addresses the radiation exposure to personnel. It also totally fails to protect the operator after the radiopharmaceutical has been administered to the patient as it has no shielding for the operator included in the design.
Proceeding to deliver the isotope to the patient – the technologist delivers the radioactive dose according to the program of the automated infusion system;
They leave the room to allow this to be conducted automatically (approx. 1 min);
They then return to the room to disconnect the infusion system from the patient. In doing so, the technologist will be exposed to the highest levels of radiation in diagnostic nuclear medicine practice (immediately after injection of a PET radiopharmaceutical) multiple times every day. As radiation protection is not included or provided for with the infusion system, the technologist receives a radiation dose for any procedure such as removing the cannula from the patient, check the patient’s wellbeing, or responding to their call for attention;
As the patient has typically been injected with the radioisotope [F-18]-FDG with an energy level of 511 keV which has a half-life of 110 mins;
The automatic system does not offer any protection to the operator. After the injection, we must consider that the patient is now a very highly radioactive and mobile source emanating radiation!
We see in the literature supplied by the manufacturer the automatic system, with patient and personnel having a discussion including physical contact, giving the impression that the unit is safe and radiation exposure after delivery is not a concern.
Automatic infusion systems are expensive to acquire and maintain. When they break down or malfunction, the medical facility is dependent on the manufacturer for service. They are also not cost-effective for smaller PET practices. However, the staff in these practices still need to be afforded the optimal solution for minimising radiation exposure. The world market for automated systems is estimated to be approx. 300 units per year, with an increase of 15-20% increase p.a.
As the systems are capable of only being loaded with a single multi-dose vial, they are limited to only one radiopharmaceutical. For some PET facilities that only use FDG, this may not be a problem, but the current trend is towards offering a wider array of PET radiopharmaceuticals to answer a greater range of clinical questions. In this scenario, the automated system is a “one trick pony”.