In vivo detection of an 125I seed located in the intracardiac region after prostate permanent brachytherapy.

PURPOSE

The purpose of this investigation is to determine the mechanism of seed migration after prostate implant and to develop procedures to minimize the risk of seed migration.

METHODS AND MATERIALS

Radioactivity survey of prostate cancer patients after permanent brachytherapy with (125)I to detect pulmonary seed embolization is routinely performed using a seed migration detector. The seed migration detector is made from a low-energy, high-sensitivity scintillation survey meter by adding a single-hole collimation cap to the scintillation probe. If a seed migration is suspected, a pair of chest radiographs is ordered to document the location of the migrated seed. A comprehensive investigation is elicited if there are discrepancies between the seed migration detector survey and the radiographic examination.

RESULTS

One hundred five patients have been surveyed, and 20 patients have demonstrated pulmonary seed embolization. In 1 patient, the seed migration detector sensed radioactivity in the thorax, but repeat chest radiographic examinations failed to show a radiopaque foreign body in the chest cavity. Owing to the signal variation mimicking heart rate, an (125)I seed located in the intracardiac region was suspected. This suspicion was confirmed in a high-quality fluoroscopy examination.

CONCLUSIONS

Seed embolization to the intracardiac region is rarely reported. The true rate may be higher, but has not been adequately documented owing to the limitation of diagnostic quality of chest radiographs to detect seed migration to the intracardiac region. The seed migration detector, on the other hand, demonstrated its efficacy in the detection of seed migration, particularly in the detection of a seed located in the intracardiac region.