Radiation dose to the spinal cord from I-131 sodium iodide (NaI) in a spinal tumor
- Oak Ridge Institute for Science and Education, TN (United States)
- Ohio State Univ., Columbus, OH (United States)
- Royal Prince Alfred Hospital, Camperdown (Australia); and others
A patient with thyroid cancer previously treated with 7.4 GBq of I-131 and 30 Gy external beam therapy to a metastasis in the thoracic spine was referred for additional I-131 therapy. In view of the previous radiation exposure, an estimate of the dose to the spinal cord from the additional I-131 was requested. Uptake and clearance of I-131 in the tumor were determined from a diagnostic I-131 study. The size of the tumor and its position relative to the spinal cord were estimated from co-registered MRI and I-123 SPECT studies. The radiation dose to the spinal cord from I-131 in the tumor was estimated using the Monte Carlo package MCNP. The spinal cord and spinal canal were modelled a concentric cylinders. The tumor was modelled as a sphere within the T8 vertebra, partially surrounding the spinal cord and invading the spinal canal. Over 1.4 million electron histories and 1.4 million photon histories were followed. The dose distribution was calculated along the spinal cord in the vicinity of the tumor. For a therapy administration of 6.5 GBq and assuming the tumor was in contact with the cord, the average absorbed dose to the cord at the level of the center of the tumor was estimated at 1.7 Gy with the electrons contributing about 1.1 Gy and the photons 0.6 Gy. The dose to the surface of the cord in contact with the tumor would be considerably higher. Along the cord, the electron dose dropped to less than 0.1%, and the photon dose declined to a value of about 0.2 Gy at a distance of 1 cm from the edge of the tumor.
- DOE Contract Number:
- AC05-76OR00033
- OSTI ID:
- 447767
- Report Number(s):
- CONF-960659--
- Journal Information:
- Journal of Nuclear Medicine, Journal Name: Journal of Nuclear Medicine Journal Issue: Suppl.5 Vol. 37; ISSN 0161-5505; ISSN JNMEAQ
- Country of Publication:
- United States
- Language:
- English
Similar Records
The Radiation Dose-Response of the Human Spinal Cord
Irradiation of Pediatric High-Grade Spinal Cord Tumors