Abstract:
Radiotherapy is the most commOn modality for treating human cancers, About 60,80% of
cancer patients need radiotherapy at some lime or othcr, clther for curative or pallialive
purposes, This is the only application of radialion. which intentionally delivcrs very high
dos.s to humans, Til. oulcomc of mdiotherapy in cancer care is heavily dependent on the
quality or lhe treaul1enl. Radialion dose to organs outside lhe lrealment field can be
si!>l1ifieantand there rare i, or clll,;cal interesl. To achieve optimum resul!, " judicious
balance bem'een the lolal dose of radiotherapy delivered and tile tbreshold limil or the
;urroundLng normal critical tissues IS requircd. Beller lrealmenl eonlrol with higher dose
to tumor volume and at lhe samc time proteeling the normal tissue against radiation injury
can bc achieved by proper treatment planning.
In lhe pre,ent work dose dislribulion to the normal tis;ue, or organ, out, ide the trealment
volume due to scattering radi"tion during radiotherapy procedure was measured by LiF
TLD.100 technique, Three ""Co teletherapy unib were used in this work, The relative risk
factor to normal ti"ue or organ i, obtained by applying: JCRP-60 (1990)
recommendalion. The measurement is conducled in four steps; (I) Dosimetry of 6OCO
telelhcrapy units rollowing lAEA do,imctry prolocol TRS-277 with lbe establishment of
the empirical formula Dm", ~ a, + a1 - a,r', (2) scattering radiation dose contribution to
different part, of paticnt's body during radiotherapy Ircatmcnt for various canecr site is
measured and cmptrical formula (s) arc c,lablishcd fnr scmlcring radiation dose
contribution 10 lhe nearest organs dUl'ing cervical treatment, (3) a correction factor to
convert skLn to orl;an depth dose due to scaltering radialion is established. and (4) organ
rbk factor outside the treatmcnl volume due 10 scattering radiation Is obtained by
calculating org"n CqULvalent do,e,
Thc result Oblained would be useful to recommend measure, for the protection of
patient's normal organ by applying proper lreatment planning during radiotherapy
treatmenl, which is a prerequisite for quality assurance in radiotherapy.
