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Program Information

Radiation Safety


Melissa Carol Martin

M Martin1*, (1) Therapy Physics, Inc., Gardena, CA

MO-D-Salon BCD-2 Monday 4:00:00 PM - 6:00:00 PM Room: Salon BCD

Combined imaging modalities of PET/CT and PET/MRI are currently available in the United States. Designing the shielding required for these dual modality units is complex and requires knowledge of both modalities for these pieces of equipment. Design considerations for PET/CT Scanners include delivery and storage of the radioisotope, dose preparation and administration, uptake rooms and restroom facilities, scanning room, control room, post scan requirements, and accompanying persons. The primary radioisotope used for whole body PET scans is Fluorine-18 FDG while Rb-128 is used for cardiac studies. Ideally, the department is laid out with the highest level of activity toward an exterior wall and away from the reception and public areas of the department. Individual calculations for each of these areas must be made in accordance with the recommendations of AAPM Task Group 108 Report. Occupancy factors for each area vary and must be taken into consideration. Additional separate calculations must be performed for the expected exposures from CT scanner, particularly if the CT scanner is used independently from PET acquisitions. The same type of considerations must be made for the MRI/PET scanners in that the shielding needed for MRI will not provide protection from the radiation exposure from the CT scanner while the usual lead shielding used to provide radiation protection for the CT scanner will not prevent artifacts in the MRI suite or excess magnetic fields in the control room area. Radio frequency (RF) shielding works to prevent exterior RFI (Radio Frequency Interference) from negatively affecting the operation of the MRI and the digital image being produced. An RF shield encompasses all six sides of a room. The design and construction challenge with RF enclosures occurs when addressing the need to connect or penetrate certain necessary applications such as the RF door, RF window, and air vents.

Learning Objectives:
1. Attendees will be aware of the required radiation shielding needed to limit the radiation exposure from the use of PET isotopes in the Diagnostic Imaging Department.
2. Attendees will be aware of the required radiation shielding needed to limit the radiation exposure from the use of the CT scanner in connection and independent of the PET portion of the PET/CT Scanner
3. Attendees will be aware of the required shielding needed for a MRI/PET scanner to prevent artifact generation within the MRI scanner room due to outside interference from RF signals.
4. Attendees will be aware of the required magnetic shielding needed for a MRI/PET scanner to minimize the magnetic exposure levels for staff to established safe levels while allowing entry into the room, observation of the patient, and ventilation for the scanner room.



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