Measurement of radiation dose to the eye-lens with bilateral whole brain irradiation

Abstract

In 40 pate in ts with metas t atic brain t umor and acute Iy mphoblastic leukemia received whole brain irradiatio n, the dose de livered to the eyelens was measured using T. L. D. ch ips a pp lied on the eyes as usual shield.The dose to the eye le ns was expressed t he re lati ve dose to the mid brain dose. Radiotherapy was adm inistered using Co.60 teletherapy with bilateral who le brain irrad iation .The resul ts are as fo llows:1. The dose to t he ri ght eye f rom its in c ipi ent fie ld is 16.6% of tumor dose wh il e the dose to the same eye from the opposite fie ld is 4 1. 2 %. On left eye , 19.2% from incipie nt field wh il e 39.2% from the opposite fie ld .2. Tota l rece ived dose to ri ght an d left eyes is 28.9%, 29.8 % of tumor dose respectively.3. Comparing len s shield group w ith o rb it shield group received dose is 22.5 %, 15.8% of tumor dose, respectivel y.4. The dose deli vered to the eye lens in ipsilateral side depends upon inter nal scatte rin g, locatio n of lead shield and penetrat ing dose of lead in itsel f. The dose in co n tralatera l side depends upon divergency of radiation beam and patient's ma lpos ition.5. The dose to the eye len s should be less than 10 % of tumor dose with adequate shield , also not m iss ing t he chance of leptome ninge a l recurrence because of overshi e lding.