Optical fibre based real-time measurements during an LDR prostate brachytherapy implant simulation: using a 3D printed anthropomorphic phantom

Abstract

An optical fibre sensor based on radioluminescence, using the scintillation material terbium doped gadolinium oxysulphide (Gd2O2S:Tb) is evaluated, using a 3D printed anthropomorphic phantom for applications in low dose-rate (LDR) prostate brachytherapy. The scintillation material is embedded in a 700 µm diameter cavity within a 1 mm plastic optical fibre that is fixed within a brachytherapy needle. The high spatial resolution dosimeter is used to measure the dose contribution from Iodine-125 (I-125) seeds. Initially, the effects of sterilisation on the sensors (1) repeatability, (2) response as a function of angle, and (3) response as a function of distance, are evaluated in a custom polymethyl methacrylate phantom. Results obtained in this study demonstrate that the output response of the sensor, pre- and post-sterilisation are within the acceptable measurement uncertainty ranging from a maximum standard deviation of 4.7% pre and 5.5% post respectively, indicating that the low temperature sterilisation process does not damage the sensor or reduce performance. Subsequently, an LDR brachytherapy plan reconstructed using the VariSeed treatment planning system, in an anthropomorphic 3D printed training phantom, was used to assess the suitability of the sensor for applications in LDR brachytherapy. This phantom was printed based on patient anatomy, with the volume and dimensions of the prostate designed to represent that of the patient. I-125 brachytherapy seeds, with an average activity of 0.410 mCi, were implanted into the prostate phantom under trans-rectal ultrasound guidance; following the same techniques as employed in clinical practice by an experienced radiation oncologist. This work has demonstrated that this sensor is capable of accurately identifying when radioactive I-125 sources are introduced into the prostate via a brachytherapy needle.

A Review of Recent Advancements in Sensor‐Integrated Medical Tools

“…Therefore, radiation dose could be successfully monitored by measuring the light intensity converted from the radiational energy. [ 172 , 173 ] When two methods are combined, more accurate brachytherapy can be performed. For example, an electromagnetic position sensor and radiation dose sensor with a plastic scintillation dosimeter were fused, significantly improving accuracy.…”

A Multi-Point Optical Fibre Sensor for Proton Therapy

“…Radiotherapy systems employing or potentially benefiting from multipoint sensing range from particle radiotherapy [1][2][3] to brachytherapy [4][5][6][7][8][9] and teletherapy [10][11][12][13]. The simultaneous, real-time monitoring of multiple points inside and outside of an irradiated volume using fibre-based sensors is currently under investigation by several groups with some success, namely in the form of the commercially available Hyperscint™ scintillator dosimeter [14]-a system that utilises a spectrometer and employs a spectral separation method to chromatically remove induced Čerenkov and fluorescence from the total signal [15][16][17].…”

Water Phantom Characterization of a Novel Optical Fiber Sensor for LDR Brachytherapy

“…Optical fiber based sensors have the small size required for insertion into BT needle applicators / catheters, allowing for potential in-vivo measurements during a procedure. Previous work by the authors have reported initial results demonstrating the potential of Gd2O2S:Tb as a scintillator for applications in LDR prostate BT [10].…”

“…This study considers the characterization of the optical fiber sensor design previously described [10], as well as additional sensor designs varying both the scintillator geometry at the tip of the sensor and the polymethyl methacrylate (PMMA) fiber core diameter. Characterization was performed using a commercial water phantom system integrated with custom 3D printed components, allowing for a more precise evaluation of sensor performance.…”