From the Guidelines
After receiving 5 mCi of I-123 for a whole body scan to monitor for thyroid cancer recurrence, it is essential to follow precautions for about 24 hours to minimize radiation exposure to others. These precautions are based on the principles of radiation safety and the properties of I-123, as discussed in various guidelines, including those from the American College of Radiology 1 and the European Society for Medical Oncology 1. The key precautions include:
- Maintaining a distance of at least 3 feet from others, especially pregnant women and children
- Using separate towels, utensils, and bathroom facilities when feasible
- Washing hands thoroughly after using the toilet
- Drinking plenty of fluids to help eliminate the radioactive material from the body more quickly
- Limiting intimate contact with someone to about 30 minutes per day
- Temporarily stopping breastfeeding for 2-3 days after the scan These measures are necessary because I-123 emits gamma radiation, although the risk is relatively low compared to I-131. The radiation from I-123 has a short half-life of about 13 hours, meaning the radioactivity decreases by half every 13 hours, and most of the radioactive iodine will be eliminated from the body through urine, sweat, and saliva within 24-48 hours. It is crucial to follow these precautions to ensure the safety of others while allowing for effective diagnostic imaging of potential thyroid cancer recurrence, as outlined in guidelines for the management of thyroid cancer 1.
From the Research
Precautions After Receiving 5 mCi I123 for Whole Body Scan
- The patient should be aware that I-123 is a diagnostic tracer and does not cause thyroid stunning, as seen in studies 2, 3.
- After receiving 5 mCi I123, the patient can expect to undergo whole-body scanning, which may involve imaging at 6,24, and 48 hours, as evaluated in a study 4.
- The patient should be informed that the diagnostic scan may not detect all sites of tumor or remnant, with a sensitivity of 70% compared to post-I-131 treatment scans, as reported in a study 4.
- However, the use of I-123 for diagnostic whole-body scanning has been shown to be effective in demonstrating residual thyroid tissue, thyroid carcinoma, and metastases, as seen in studies 2, 3, 5.
- The patient should follow standard radiation safety precautions, although the risk of radiation exposure from I-123 is relatively low due to its short half-life and pure gamma emission, as noted in a study 2.
- It is essential to note that the diagnostic whole-body scan may not affect the dose of radio-iodine I-131 used for remnant ablation of differentiated thyroid cancer and does not influence the recurrence rates, as reported in a study 6.
- Patients should be aware that I-123 scans offer greater convenience and facilitate earlier institution of therapy by decreasing the interval between diagnostic scanning and radioiodine treatment, as mentioned in a study 5.