In vivo dosimetry of thyroid doses from different irradiated sites in children and adolescents: a cross-sectional study.
BACKGROUND
Scattered radiation can be assessed by in vivo dosimetry. Thyroid tissue is sensitive to radiation, even at doses <10 cGy. This study compared the scattered dose to the thyroid measured by thermoluminescent dosimeters (TLDs) and the estimated one by treatment planning system (TPS).


METHODS
During radiotherapy to sites other than the thyroid of 16 children and adolescents, seventy-two TLD measurements at the thyroid were compared with TPS estimation.


RESULTS
The overall TPS/TLD bias was 1.02 (95% LA 0.05 to 21.09). When bias was stratified by treatment field, the TPS overestimated TLD values at doses <1 cGy and underestimated them at doses >10 cGy. The greatest bias was found in pelvis and abdomen: 15.01 (95% LA 9.16 to 24.61) and 5.12 (95% LA 3.04 to 8.63) respectively. There was good agreement in orbit, head, and spine: bias 1.52 (95% LA 0.48 to 4.79), 0.44 (95% LA 0.11 to 1.82) and 0.83 (0.39 to 1.76) respectively. There was small agreement with broad limits for lung and mediastinum: 1.13 (95% LA 0.03 to 40.90) and 0.39 (95% LA 0.02 to 7.14) respectively.


CONCLUSIONS
The scattered dose can be measured with TLDs, and TPS algorithms for outside structures should be improved.
Cassiane Cardoso
CC
Bonato
Henrique Bregolin
HB
Dias
Michele da Silva
Mda S
Alves
Lucas Ost
LO
Duarte
Telpo Martins
TM
Dias
Maiara Oliveira
MO
Dalenogare
Claudio Castelo Branco
CC
Viegas
Graduate Program in Internal Medicine, Endocrinology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil. rhelnecave@gmail.com.
Regina Helena
RH
Elnecave
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D058958:Organs at Risk; D011829:Radiation Dosage; D011874:Radiometry; D012542:Scattering, Radiation; D012867:Skin / Q000528:radiation effects; D013961:Thyroid Gland / Q000528:radiation effects*