Measurement of dose rate from exposure-calibrated sup 125 I seeds

Journal Article · Tue May 01 00:00:00 EDT 1990 · International Journal of Radiation Oncology, Biology and Physics; (USA)

DOI:https://doi.org/10.1016/0360-3016(90)90458-V· OSTI ID:6693379

Luxton, G; Astrahan, M A; Findley, D O; Petrovich, Z ^[1]

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1. Univ. of Southern California School of Medicine, Los Angeles (USA)

Dose rate in water 1 cm transverse to an {sup 125}I seed calibrated for air kerma strength is not well established; {sup 125}I dosimetry calculations are, however, based on this constant. The specific dose constant was obtained from a series of dose rate measurements using thermoluminescent dosimetry (TLD) in a rigid geometry, full scatter acrylic phantom for individual model 6711 seeds. With a statistical precision of approximately +/- .5%, the dose rate to an infinitesimal mass of water located in acrylic at a perpendicular distance of 1 cm from the seed was found to be 0.977 cGy/h per microGy-m2/h of air kerma strength. Dose rate in a water phantom was calculated using a model that takes into account differences in both attenuation and scatter between water and acrylic. The specific dose constant in water was determined to be 0.932 (1.184 cGy-cm{sup 2}/mCi-h, for the conventional exposure rate constant of 1.45 R cm2/mCi-h). This value is 7.5% less than dose rate in water from an unattenuated point source, and 9.7% less than the value commonly used for dosimetry calculations. The results suggest that most clinical {sup 125}I dosimetry estimates to date should be reconsidered for a possible reduction by about 10%. Relative scatter attenuation factors at 3 and 5 mm are also presented.

• OSTI ID: 6693379
• Journal Information: International Journal of Radiation Oncology, Biology and Physics; (USA), Journal Name: International Journal of Radiation Oncology, Biology and Physics; (USA) Vol. 18:5; ISSN 0360-3016; ISSN IOBPD
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
655003* -- Medical Physics-- Dosimetry
ATTENUATION
BETA DECAY RADIOISOTOPES
CALIBRATION
DAYS LIVING RADIOISOTOPES
DOSES
DOSIMETRY
ELECTRON CAPTURE RADIOISOTOPES
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
ISOTOPES
KERMA
MOCKUP
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PHANTOMS
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOISOTOPES
SCATTERING
STRUCTURAL MODELS
THERMOLUMINESCENT DOSIMETRY
WATER