Technical Assistance Request, Evaluation of Comments on NRC Information Notice for Ophthalmic Applicators (NRC IN 90-59)
See the memorandum from J. E. Glenn to D. M. Collins dated February 20, 1992.
As requested in a Region II memorandum from William Cline to J. E. Glenn, dated March 13, 1991 (Enclosure 1), the staff has reviewed the comments presented by the Navy Radiation Safety Committee (Enclosure 2) concerning NRC Information Notice 90-58, "Improper Handling of Ophthalmic Strontium-90 Beta Radiation Applicators" (Enclosure 3). The following comments were offered in response to the Navy Radiation Safety Committee's concerns as denoted by NRC Region II (Enclosure 1).
Comment 2a: Issue of holding the eye open with tape during the procedure.
NRC consultants tell us that tape is not an optimal means of securing a patient's eyelid. The current medical practice calls for the use of eyelid retractors. In order to prevent Bremsstrahlung radiation, retractors made of low atomic weight materials are preferred.
Comment 2b: Number of treatments per year versus use of fingertips.
The number of treatments stated in case 2 was used as an example and should not become the focus of the illustration. The case emphasizes that a physician using his/her fingers to secure the eyelid while administering the treatment is improper procedure. Regardless of the number of treatment applications, attention surrounding the illustration should be directed towards ALARA guidelines and the use of passive restraints such as eyelid retractors to immobilize the eyelid.
Comment 2c: Interpretation of "extremity" limits.
Contrary to the Navy's criticism, contact with the source tip of the applicator could indeed result in a radiation dose in excess of NRC limits. We do not agree with the concept that exposure with the Sr-90 eye applicator source is tantamount to "hot particle" exposure because of differences in geometry and dosimetry. In particular, the area irradiated by a "hot particle" is substantially less than one square centimeter, whereas the area irradiated by a strontium-90 (Sr-90) eye applicator is greater than one square centimeter. As defined in 10 CFR 20.1003, the shallow-dose equivalent for skin or extremities applies to tissue at a depth of 0.007 centimeters averaged over an area of one square centimeter. Therefore this criteria applies to Sr-90 eye applicators.
Comment 2d: Rules requiring personnel monitors.
The requirements for personal dosimeters discussed in the information notice are in keeping with minimally accepted ALARA guidelines.
The Navy's data indicates that their exposures do not approach 10 CFR Part 20 minimum requirements for personnel monitoring devices. However, it would be prudent health physics practice to wear personal dosimeters because of unanticipated exposures as well as planned exposures. Once an individual has demonstrated sufficient knowledge and skill using an applicator, exceptions might be considered.
If a licensee can clearly demonstrate that (1) the radioactive material used is limited to the Sr-90 eye applicator and (2) the resulting exposures did not reach the limits set forth in 20.202 or 20.1502 (a), NRC would consider licensee procedures without requirements for the use of personal dosimeter devices on a case-by-case basis.
Comment 2e: Sterilizing agents.
Further review of the sterilization processes revealed that the typical manufacturer's directions for sterilizing the device are inconsistent with the Centers for Disease Control's (CDC) recommendations. While this may be an important point, the information provided in Item 1 of the typical manufacturer's instructions was designed to call the licensee's attention to the need for sterilization of the Sr-90 eye applicators. The manufacturers may ultimately modify their sterilization procedures to coincide with those of the CDC.
Comments 2f and 2g: Corrosion and Calibration.
The information of concern in comments 2f and 2g was not discussed in NRC IN 90-58. We are currently planning to develop an information notice covering both the calibration and possible corrosion of the device.
Comment 2h: Seventy years of use without an incident.
The three uses cited in the information notice represent examples of significant potential exposures and, as such, warrant notification of the licensees.
Regulatory references: 10 CFR 20.1, 10 CFR 20.202, 10 CFR 20.1101, 10 CFR 20.1502
Subject codes: 8.1, 8.3, 8.5
Applicability: Byproduct Material