Radiation Safety Oversight of Surgical Procedures

Radiation Safety Oversight of Surgical Procedures Involving the Use of RAM
By: René Michel, M.S., RSO
VA San Diego Healthcare System, San Diego, CA

Introduction
* The objective of this presentation is to review the various Radiation Safety aspects of a typical medical procedure that involves the use of radiological agents.
* Lymphoscintigraphy (LS) is a medical procedure for the treatment of malignant melanoma and mamma-carcinoma.
* The goal is to identify which sentinel lymph nodes (SLN) have been infiltrated by tumor cells
* The objective of this presentation is to determine what basic radiation safety controls are needed.
* ALARA, dosimetry, contamination control, radioactive waste, etc.

Outline
* Radioactive Drugs Used
* Overview of the Procedure
* Radiation Exposure
* Contamination Control
* Recommendations

Radioactive Drugs
* Many radiopharmaceuticals have been evaluated for and used in LS studies
* The ideal drug, must have the following characteristics:
* Small and uniform particle size
* Short half-life
* Low LET
* Appropriate energy for gamma imaging
* 198Au colloid was one of the first widely used drugs in LS
198Au Characteristics
Particle size: 3-5 nm
Half-life: 2.7 d
Emissions: 412 keV photons plus beta particles
* 198Au was replaced by other agents with the increased availability of 99mTc
* Antimony trisulfide, albumin, human serum albumin, sulfur colloid and nano-colloid
99mTc Characteristics
Particle size: 3-90,000 nm
Half-life: 6 h
Emissions: 140 keV photons

Procedure Overview
* There are three stages in Sentinel Node LS
1) Lymphatic Mapping
2) Intradermal Blue Dye Injection
3) SLN Biopsy
Lymphatic Mapping
* The surgeon injects about 1 mCi of 99mTc unfiltered sulfur colloid intradermally near the lesion.
* The colloid is taken up by the lymphatic system and the patient is imaged with a conventional gamma camera.
* About 20 min from injection dynamic scanning is performed
* A late phase scanning done 90 min after injection shows the location of the SLNs.
* The location of the node is marked on the skin of the patient

Blue Dye Injection
* The patient is moved to the OR to perform biopsy
* To assist in identifying the nodes draining the site of interest, a blue dye is injected

SLN Biopsy

* A surgeon uses the skin mark and a scintillation probe to relocalize the highest area of uptake
* A dissection is performed through soft tissue to remove “hot” nodes located by the gamma probe
* All excised nodes are sent to the pathology lab for histological examination to asses for invasion by tumor cells

Radiation Exposure
* Nuclear Medicine personnel are excluded from this evaluation, they are already closely monitored.
* Radiation exposure to OR and Pathology personnel and the potential for spread of contamination are considered the main radiation safety concerns.

Hazards Control-Radiation Exposure
* The expected radiation exposure to personnel from handling SLN radioactive specimens is very small
* 10-15 SLN procedures/year are performed in most large medical centers
* Several studies have documented dosimetry data
Average whole-body radiation dose equivalent/procedure for hospital personnel from malignant melanoma and mamma-carcinoma SLN surgery with typical activities.
* A surgeon's hand dose has been reported to be 10 mrem (Miner et al. 1999)
* The pathologist’s hand dose is even smaller, ~ 4-6 mrem (Veronesi et al.1999)

Hazards Control- Contamination
* The residual activities a day post surgery are <0.3 mCi for tumor-specimens and <50 nCi for SNLE (Kopp and Wengenmair 2002). * These activities are relatively fixed to the tissue, they do not produce contamination that exceeds the allowed levels. * Standard universal precautions used to prevent infections are sufficient to avoid any kind of incorporation in the bodies of those handling specimens. Specimen Control * Under 10 CFR 20.1905 (NRC 2002), labeling is not required for containers holding less than 1.0 mCi of Tc-99m * Labeling is also exempted if only authorized personnel have access to containers, provided a written record identifies the contents. * Specimen quarantine before gross examination is unnecessary since the level of exposure to personnel is not a safety concern. * Despite the simplicity of the guidelines, each institution is expected to develop and implement procedures for handling radioactive specimens. * Awareness training documentation for all individuals handling these specimens is also necessary. Recommended Guidelines 1. Follow standard universal precautions (e.g., wear hospital gown, surgical gloves, etc.). 2. Using forceps, place all radioactive specimens removed from the patient in a sealed container. 3. In addition to the patient’s name and specimen number, label all resected primary site specimens with the name of the isotope (e.g., 99mTc), date and time when it was collected 4. Maintain security of specimens at all times 1. Upon completion of the surgical procedure, all instruments (e.g., forceps, scalpels, etc.) having had direct contact with the radioactive specimens should be cleaned following standard procedures. 2. All specimens should follow the normal biomedical waste stream and be surveyed before disposal to ensure that radiation levels are not distinguished from background References Radiation Safety Oversight of Surgical Procedures.ppt