Sequential morphological changes in the dog brain after interstitial iodine- 125 irradiation

Area of Science:

• Neurology
• Radiology
• Oncology

Background:

• Stereotactic radiosurgery utilizes radioactive sources for targeted tissue ablation.
• Understanding the precise effects of different radioisotopes is crucial for optimizing treatment strategies.
• Iodine-125 is a potential radioisotope for localized brain lesion generation.

Purpose of the Study:

• To investigate the morphological changes in canine brains following stereotactic implantation of Iodine-125 seeds.
• To evaluate the efficacy and safety of Iodine-125 as a radioactive source for creating localized brain necrosis.
• To compare the effects of Iodine-125 with other radioactive sources.

Main Methods:

• Stereotactic implantation of Iodine-125 seeds (3.55 mCi) into the subcortical white matter of the left coronal gyrus in six beagle dogs.
• Morphological analysis of brain tissue at intervals from 25 to 368 days post-implantation.
• Dosimetric assessment to correlate tissue changes with accumulated radiation dose.

Main Results:

• A consistent finding of calcifying necrosis (3-6 mm diameter) with adjacent demyelination was observed.
• No delayed radiation damage was detected outside the perifocal demyelinated zone.
• Necrosis was sharply delineated and stabilized in size after 70 days (18,000 cGy), with associated vasogenic edema.

Conclusions:

• Iodine-125 seeds produce a well-defined, localized necrotic lesion in the brain without significant delayed radiation effects.
• The characteristics of Iodine-125 (low energy gamma, no beta radiation, 60.2-day half-life) make it a favorable source for controlled brain lesion generation.
• Observed morphological changes differ from those induced by other radioisotopes, highlighting the unique properties of Iodine-125.