Impact of radiotherapy on normal brain tissue: semi-automated quantification of decrease in perfusion.
OBJECTIVE
We attempted to ascertain the impact of Co-60 conventional external radiotherapy (cRT) on the perfusion of normal brain tissue in relation to the radiation doses delivered to the tumors in patients with primary brain tumors.


METHODS
After surgery 18 patients (pts) were due to undergo cRT with a total dose of 5400- 6400 cGy. All the patients had a Tc-99m-HMPAO SPECT study prior to cRT (basal), 15th and 30th days of cRT as well as 1 (in 6 pts), 3 (in 9 pts), and 6 (in 3 pts) months after cRT. For quantitative evaluation, the entire set of transverse slices were divided into 4 regions as frontal, parietal, occipital and temporal regions by means of a computer software program. Semi-automated quantification was performed on a total of 1392 regions in 87 studies to determine left to right ratios. An interregional difference of at least 10% was considered abnormal.


RESULTS
After elimination of tumor sites, 80 normal brain regions showed decreased perfusion after cRT. The percent decrease in perfusion was (mean 22.5+/-9.9) significantly higher in areas irradiated with doses > 3000 cGy (p < 0.05).


CONCLUSIONS
cRT has adverse effects on the perfusion of normal brain tissue for doses > 500 cGy. Our findings justify treating patients with small and limited lesions with stereotactic radiotherapy in order to minimize the adverse effects of cRT on normal tissues.
Gülaldi
N C
NC
Department of Nuclear Medicine, Faculty of Medicine, Hacettepe University, Ankara, Turkey. gulaldi@hun.edu.tr
Kostakoğlu
L
L
Uzal
D
D
Hayran
M
M
Elahi
N
N
Uysal
U
U
Aktaş
A
A
Atahan
L
L
Bekdik
C
C
D000293:Adolescent; D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001921:Brain / Q000000981:diagnostic imaging / Q000528:radiation effects*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000532:radiotherapy* / Q000601:surgery; D002648:Child; D003037:Cobalt Radioisotopes; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D011878:Radiotherapy / Q000009:adverse effects; D011879:Radiotherapy Dosage; D012044:Regression Analysis; D012074:Remission Induction; D019690:Technetium Tc 99m Exametazime / Q000493:pharmacokinetics; D015899:Tomography, Emission-Computed, Single-Photon
D003037:Cobalt Radioisotopes; D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime