title: Near-field dosimetry of 125I sources for interstitial brachytherapy implants measured using thermoluminescent sheets.
abstract: The dosimetric characteristics were measured for two types of 125I low-energy photon-emitting sources by using a wide and highly sensitive thermoluminescent (TL) sheet film, which was developed for two-dimensional dose distribution measurements. The TL film is made of Teflon homogeneously mixed with small powders of thermoluminescence (BaSO4:Eu doped). Various dosimetric parameters (i.e., radial dose function, 2D and 1D anisotropy functions) of model 6711 and 6702 125I sources were obtained at various distances from the source surfaces to 15 mm. These parameters obtained with TL sheet were compared with the data recommended in the updated AAPM TG-43 report. The radial dose functions measured with TL sheet are in agreement with those established data of model 6711 125I seed and model 6702 125I seed at most of the distances within 5% and 7%, respectively. All the measured anisotropy functions showed symmetry about the longitudinal source axis. The anisotropy of dose distributions was clearly present in the immediate vicinity of the source edges. The measured 2D anisotropy function values at 1 cm are in reasonably good agreement with the recommended values. The differences at two points in the 1D anisotropy functions measured with TL sheet and the established data at 1 cm from source center were 0.7% and 1.9% for model 6711 and 6702 125I sources, respectively; the differences at 0.5 cm were 1.5% and 1.7% for model 6711 and 6702 125I sources, respectively. The relative dosimetric characteristics in the vicinity of actual interstitial brachytherapy sources containing 125I have been experimentally determined by using the TL sheet as a 2D dosimeter.
authors.affiliation: Department of Oncoradiology, Nara Medical University, 840 Shijo-cho Kashihara-city Nara 634, Japan.
authors.forename: Kazuro
authors.initials: K
authors.lastname: Iwata
authors.forename: Ning J
authors.initials: NJ
authors.lastname: Yue
authors.forename: Ravinder
authors.initials: R
authors.lastname: Nath
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000379:methods; D007457:Iodine Radioisotopes / Q000032:analysis* / Q000627:therapeutic use*; D019736:Prostheses and Implants; D019275:Radiopharmaceuticals / Q000032:analysis / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation* / Q000379:methods
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals