The use of gel dosimetry to measure the 3D dose distribution of a⁹⁰Sr/⁹⁰Y intravascular brachytherapy seed

Abstract

Absorbed dose distributions in 3D imparted by a single (90)Sr/(90)Y beta particle seed source of the type used for intravascular brachytherapy were investigated. A polymer gel dosimetry medium was used as a dosemeter and phantom, while a special high-resolution laser CT scanner with a spatial resolution of 100 microm in all dimensions was used to quantify the data. We have measured the radial dose function, g(L)(r), observing that g(L)(r) increases to a maximum value and then decreases as the distance from the seed increases. This is in good agreement with previous data obtained with radiochromic film and thermoluminescent dosemeters (TLDs), even if the TLDs underestimate the dose at distances very close to the seed. Contrary to the measurements, g(L)(r) calculated through Monte Carlo simulations and reported previously steadily decreases without a local maximum as a function of the distance from the seed. At distances less than 1.5 mm, differences of more than 20% are observed between the measurements and the Monte Carlo calculations. This difference could be due to a possible underestimation of the energy absorbed into the seed core and encapsulation in the Monte Carlo simulation, as a consequence of the unknown precise chemical composition of the core and its respective density for this seed. The results suggest that g(L)(r) can be measured very close to the seed with a relative uncertainty of about 1% to 2%. The dose distribution is isotropic only at distances greater than or equal to 2 mm from the seed and is almost symmetric, independent of the depth. This study indicates that polymer gel coupled with the special small format laser CT scanner are valid and accurate methods for measuring the dose distribution at distances close to an intravascular brachytherapy seed.

Monte Carlo calculated TG‐60 dosimetry parameters for the emitter brachytherapy source

“…4, the radial dose function of the 153 Sm source is compared to that of the 90 Sr / 90 Y, 90 Y, and 142 Pr sources. 13,23,24…”

Three-dimensional radiation dosimetry using polymer gel and solid radiochromic polymer: From basics to clinical applications

“…The measurements were done with various types of radioactive sources: Iridium-192 high dose rate (HDR) source[42-48], low dose rate (LDR) Iodine-125 seed[49,50], and LDR Cesium-137 source[51]. Additionally, the 3D dosimeters were used for the dosimetry of beta-emitting radioactive sources such as Ruthenium-103[52], Renium-188[53], and Ytirium-90[54]. The SPD was also used with a radioactive source[55,56].…”

Monte Carlo dosimetric parameter study of a new32P brachytherapy source

“…Although the dosimetric parameters of the 32 P brachytherapy source are difficult to obtain, the experimental works and simulation codes were both successful when performed. [9][10][11][12] Wang et al 10 derived the dosimetric data from their modified EGS4 MC code of a 90 Sr/ 90 Y source in SS304 stainless steel. Xu et al 12 presented the three-dimensional distribution of a 90 Sr/ 90 Y intravascular brachytherapy seed by experimental measurement.…”