Facilities and equipment

Shielding calculation process for RLT treatment rooms

Steps

1. Review the floor plan: The first step is to review the facility's floor plan to understand its scale and complexity. Identify the locations of radiation sources, which typically include^1,2:
• RLTs within patients in treatment rooms (the primary radiation sources)
• Radioactive materials in storage rooms and hot labs (where doses are calibrated and prepared for patient infusion)
2. Determine the shielding requirements: Based on the exposure rates at the control points, calculate the amount of shielding necessary to meet the radiation exposure requirements²
3. Determine the occupancy factors “T”: The occupancy factors for different areas are assigned according to their use. For example, fully occupied work areas have an occupancy factor of 1 (indicating continuous use). Public corridors have an occupancy factor of 1/5 and an unattended waiting room has an occupancy factor of 1/20 (indicating limited occupancy)¹
4. Determine the work factors “W”: The work factor is determined by the number of patients treated per day and can vary depending on the specific scenario. This factor is incorporated into the calculations to estimate the allowable exposure in a week at each control point^1,3

The following information considers a simplified calculation for exposure rate in different distances from the primary source. In these calculations, the work factor will be based on an average activity level, such as those from PLUVICTO® (lutetium Lu 177 vipivotide tetraxetan) and LUTATHERA® (lutetium Lu 177 dotatate), assuming 40 hours per week.

If an individual were to be continuously present in an uncontrolled area, the dose rate (Di) from external sources shall not exceed 20 µSv in any 1 hour.⁵ Accordingly, the treatment workload per week (or year) must be accounted for (see scenarios below) and the thickness of the wall (ie, shielding barrier) must be calculated.^6,7

Scenarios

The examples and scenarios provided herein are for educational purposes. NCRP Report No. 147 states that only qualified experts shall perform the shielding calculations and surveys. A qualified expert is an individual who is certified by the American Board of Radiology, the American Board of Medical Physics, or the American Board of Health Physics; they may be the Authorized Medical Physicist on the radioactive materials license.¹

Expert insight

Consulting firms can offer comprehensive services that include the design, calculation, and installation oversight for radiation shielding in health care settings. These firms may assist in performing detailed shielding analysis for treatment centers. Contact the Novartis radioligand therapy specialists for more information.³

See below for 3 examples: