Interstitial rotating shield brachytherapy for prostate cancer

Abstract

For the case considered, the proposed(153)Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%-44% if the clinician allows a urethral dose gradient volume of 0-5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed (153)Gd-based I-RSBT technique in reasonable treatment times.

Multisource Rotating Shield Brachytherapy Apparatus for Prostate Cancer

“…For this apparatus 153 Gd is selected as the source isotope due to its reasonable dose rate, energy spectrum ranging from 40 keV to 105 keV (60.9 keV average), half-life of 242 days, and its potential for mass production via neutron irradiation of 151 Eu or 152 Gd. 31 A nitinol (NiTi) RSBT needle containing a rotating catheter as well as a shielded 153 Gd source was designed, and the dose rate distribution about the partially shielded source was calculated using the MCNP5 Monte Carlo code and a published 153 Gd spectrum, 36 with photons emitted in the intermediate range of 40–105 keV. The modeled source was a 7.41 g/cm 3 Gd 2 O 3 pellet containing 2,442 GBq of 153 Gd per gram of Gd 2 O 3 , which could be generated by neutron irradiation of spent dual-photon absorptiometry sources containing about 87% 152 Gd.…”

“…In a previous study, 31 a partially-shielded source/catheter/needle system was defined, based on the 153 Gd isotope, and was shown by simulation to be capable of lowering the urethral dose up to 44% relative to conventional HDR-BT. An apparatus for mechanically delivering the dose through the inserted needles was not proposed, however, and the multisource RSBT apparatus presented here overcomes the technical barriers to implementation of the previously proposed approach.…”

“…An apparatus for mechanically delivering the dose through the inserted needles was not proposed, however, and the multisource RSBT apparatus presented here overcomes the technical barriers to implementation of the previously proposed approach. 31 Since the dose rate per unit mass for 153 Gd is substantially lower than that of 192 Ir, multiple shielded 153 Gd sources need to be used simultaneously in order to deliver RSBT dose distributions of up to 20 Gy in a clinically acceptable time of fewer than 2 hours. The apparatus presented in this work can control the emission angles and depths of up to 20 partially-shielded 153 Gd sources simultaneously.…”

Evaluation of hypothetical 153Gd source for use in brachytherapy

“…However, in the study by Enger et al, 14 to have a reasonable dose rate, a relatively large (10.0 mm length and 0.84 mm diameter of active length) 153 Gd source was designed; therefore, this size of source is too large to be partially shielded effectively interstitially, and inefficient due to self-attenuation. The source that is much more likely to be used clinically is that described in the study by Adams et al 17 In that study, an active diameter of 0.44 mm and active length of 10.0 mm was used for each source, while 10 such shielded sources were evaluated. Taking into account the specific activity, self-absorption, construction costs, the needed dosage and duration of an effective treatment by 153 Gd source, there should be a trade-off between dosimetric effectiveness and treatment time.…”

Absolute intensities of the γ-ray emissions originating from the electron capture decay of 153Gd

“…Gadolinium-153 has been proposed as a replacement for 192 Ir in brachytherapy treatment. The lower energy photon emissions from 153 Gd are advantageous as they would require less shielding [8,9]. The common production mode of 153 Gd is by the neutron irradiation of a europium target, which is subsequently chemically separated to produce a radiochemically pure 153 Gd [10,11].…”