The effect of 125I interstitial radiotherapy on blood-brain barrier function in normal canine brain.
Blood-brain barrier (BBB) function was studied in 14 normal dogs at time periods from 7 to 717 days after permanent insertion of 5- to 7-mCi seeds of iodine-125 (125I) for interstitial radiation. The BBB function was measured with carbon-14-labeled alpha aminoisobutyric acid (AIB) and quantitative autoradiography, and expressed as a unidirectional blood-to-brain transfer constant, K. The 125I radiation lesions consisted of three concentric histologically and functionally distinct zones: 1) a central zone of calcified necrosis; 2) a spongy fluid-filled zone; and 3) a narrow rim (2.6 +/- 0.6 mm wide) of viable brain tissue with increased permeability. Within this rim, the mean value of the K of AIB was 5.8 times that of normal cortex. Over the 7- to 392-day time period the value of K remained rather constant, and by 716 days K values had returned to normal. There was moderate regional variation in the value of K; it was highest in the white matter and lowest in the gray matter surrounding the radiation lesion. The radiation lesion progressively increased in size from 7 to 80 days, after which there was little change. This study illustrates that the geographically circumscribed radiation from 125I seeds is accompanied by similarly well-defined changes in BBB function, which may persist for over 1 year following insertion of the 125I seed. This altered BBB function is probably responsible for the cerebral edema associated with 125I interstitial radiotherapy.
Groothuis
D R
DR
Department of Neurology, Northwestern University, Evanston, Illinois.
Wright
D C
DC
Ostertag
C B
CB
D000621:Aminoisobutyric Acids; D000818:Animals; D001812:Blood-Brain Barrier; D001918:Brachytherapy; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism / Q000473:pathology / Q000502:physiology*; D004285:Dogs; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D009336:Necrosis
D000621:Aminoisobutyric Acids; D007457:Iodine Radioisotopes; C100049:2-aminoisobutyric acid