Physics & Astronomy

Cyclotron Production of Short Lived Positron Emitters in Medical Imaging

There are substantial advantages in imaging the annihilation radiation produced by positron emitting radio-labeled compounds in medical imaging. Within the past ten years there has been a huge increase in the number of facilities performing medical imaging with positron tracers due to Medicare and insurance coverage, primarily for cancer indications.

Fluorine-18 is a positron emitter with a 110 minute half-life that can be labeled to a glucose molecule, which is taken up and trapped by most malignant tumors. The short half-life requires that production, radiolabeling and shipping be done quickly and on a daily basis. Other positron-emitting tracers for research imaging are labeled with C-11 (T1/2 – 20 minutes), N-13 (T-1/2 – 10 minutes) and O-15 (T-1/2 2 minutes), but require that a cyclotron be on site at the imaging facility. The FDA requires that the production of all radiolabeled drugs now be done in a laboratory that is compliant with Good Manufacturing Practices (GMP). Therefore due to the short half-life the production and quality control testing procedures must be fast and efficient. Automated synthesis modules are used to perform radiolabeling as high quantities of radioactive materials are involved and chemistry procedures must be precise.

Positron Emission Tomography (PET) imaging is performed by detecting the annihilation photons from the radiotracer. Most scanners now also incorporate a CT scanner within the same gantry to allow the generation of physiologic images from PET to be displayed along with CT anatomic images. PET/CT scans have become the standard of care for staging tumor forming cancers and are used to follow the effectiveness of therapy in some patients. PET/CT has demonstrated the highest sensitivity for detecting most types of cancer and can also be applied to some applications in neurology for diagnosing Alzheimer’s disease and applications in some types of heart disease. PET/CT has been the fastest growing area of medical imaging for the last few years.