Triaging of patients following the start of a new Cardiac PET service with Rb82

Introduction: Coronary Arterial Disease (CAD) is the disease responsible for more deaths in UK and similarly in most of western country. Our Nuclear Medicine (NM) service already provided Myocardial Perfusion Scintigraphy (MPS) with Tc-99m-MIBI using CT enhanced gamma cameras, but the service was not considered competitive with other imaging modalities (cardiac-CT, cardiac-MRI). In 2018 we started a project to introduce cardiac PET CT with Rb-82 which provides more diagnostic information on CAD with less radiation dose to the patient and allows rest and stress images to be achieved in one short appointment. Cardiac PET does not require daily provision of radiotracer, since the Sr-82/Rb-82 generator is replaced every 4-6 weeks, enabling the service to be more operationally flexible.

Material and Methods: To set up the service we required a cart for Rb-82 infusion, Sr-82/Rb-82 generator, adenosine infusion pump, 3 lead ECG and dedicated training for technologist, physics and nursing staff. Corridor 4DM, a suite for cardiac post processing was installed to support reporting on the Hermes Medical platform. The MPS output of NM service was an average of 1650 MPS stress scans a year with relative rest scans divided across 4 NM sites.Rb-82cardiac PET-CT is performed in the most centrally located site, where the PET scanner is located. The PET-CT service is equipped with a GE-Discovery 710 DR with a 128 slice CT enabling also to perform CT dedicated for Calcium Score. The department is also supported by a mobile PET-CT service with a Siemens Biograph, working 3 days a week for 18F-FDG PET scans only. The site has a dedicated Cardiac Imaging service performing an average of 8200 Cardiac MRI scans and 6100 with increasing requests and consequent capacity service. The service was planned to start in November 2019 with 10 scans a week and reach full capacity in April 2020 with 40 scans a week. The access plan to the new service aimed to have 50% of our Tc-99m MPS scans converted to cardiac PET, while the other 50% as new request specific for cardiac PET, since the Rb-82 was considered a much suitable alternative to other imaging modalities. Results and Discussion: The service started in November 2019 with 10 patients a week and in 2 months the number of scans performed reached 24 a week. Oncology patients’ slots were preserved increasing the operating days of mobile PET and opening Saturday lists on the static scanner. Initially we populated the cardiac PET list converting MPS requests, while in December we received more than 70 new requests. None attendance for patients referred from peripheral hospital was flagged compared to referrals from central hospitals. The triage was also made considering Cardiac PET-CT has much better diagnostic accuracy in overweight patients compared with MPS. Feedback from patients was collected and showed a general happiness in particular for patients that had a conventional MPS before. Only 1 minor adverse event was observed as side effect of adenosine.

Conclusions: Rb82 Cardiac PET-CT has a game changer role in NM for cardiac diagnostic, being able to provide comprehensive diagnostic information with better patient experience and an administered dose 80% lower than conventional MPS. The service requires a massive amount of efforts from the PET team and a very careful triaging of patients, to ensure appropriateness of scans and to preserve oncology patient slots when limited resources are available in the PET service.