Search Results (6)

Background/Objectives: The use of a patient-specific bolus in radiation therapy is critical for achieving precise dose delivery, particularly for irregular anatomical surfaces. Conventional boluses often suffer from poor conformity and air gaps, leading to suboptimal dose distribution. This study aimed to develop and evaluate a novel bolus fabrication method using the mold-and-casting (M&C) technique, which integrates 3D printing and flexible silicone materials to address these limitations. Methods: The proposed workflow includes CT imaging, 3D modeling, mold fabrication via 3D printing, and silicone casting to produce a patient-specific bolus. The process is followed by quality assurance steps and clinical application. Geometric accuracy was assessed through surface matching and cross-sectional comparisons, and dosimetric performance was evaluated using in vivo measurements with MOSFET detectors. The biocompatibility of the silicone material was tested according to standardized cytotoxicity, skin sensitization, and irritation protocols. Results: The fabricated boluses demonstrated high geometric fidelity, with volumetric and surface discrepancies of less than 3% compared to the planned structures. Dosimetric evaluations indicated that maximum dose differences remained within the clinically acceptable range of ±5%, confirming accurate dose delivery. Biocompatibility tests confirmed that the silicone material is safe for clinical use. Conclusions: The M&C method offers a streamlined approach to patient-specific bolus fabrication that integrates well into existing clinical workflows. Compared to traditional sheet boluses, it significantly reduces air gaps and enhances surface dose uniformity. These findings support the clinical potential of this technique to improve both precision and efficiency in radiation therapy. Full article

Background: In high-risk breast cancer patients with skin infiltration, the administration of a uniform dose to superficial tissues is fundamental in order to reduce local skin relapse. A personalized bolus may prevent the potential inadequate dose distribution of a standard bolus due to air gaps between the bolus and the skin. In this pilot study, we introduced into clinical practice the use of a personalized 3D-printed bolus filled with ultrasound transmission gel. Methods: Seven patients undergoing radiotherapy after mastectomy were selected. A 3D-printed bolus dosimetric assessment was performed with MOSFET dosimeters on an anthropomorphic phantom and, subsequently, on three selected cases with increasing bolus shape irregularity. Acute/late toxicity and local control were assessed. Results: Overall, for the clinical cases, the percentage median difference between the measured and calculated doses was −2.7% (−7.0–4.9%). The median follow-up was 21 months. After two years, one patient showed G2 pain, one patient manifested G1 telangiectasia, one patient showed G1 hyperpigmentation, and two patients had no relevant toxicity. Conclusions: A personalized 3D-printed bolus filled with ultrasound gel may easily reproduce the standard bolus’ consistency and provide accurate coverage of the target area with tolerable acute/late toxicity grades. This is a pilot study, and further investigations are needed. Full article

Optical fibres are gaining popularity for relative dosimetry in proton therapy due to their spatial resolution and ability for near real-time acquisition. For FLASH proton therapy, these fibres need to handle higher dose rates and larger doses than for conventional proton dose rates. We developed a multi-point fibre sensor embedded in a 3D-printed phantom which can measure the profile of a FLASH proton beam. Seven PMMA fibres of 1 mm diameter were embedded in a custom 3D-printed plastic phantom of the same density as the fibres. The phantom was placed in a proton beam with FLASH dose rates at the TRIUMF Proton Therapy Research Centre (PTRC). The sensor was exposed to different proton energies, 13.5 MeV, 19 MeV and 40.4 MeV, achieved by adding PMMA bolus in front of the phantom and three different beam currents, varying the dose rates from 7.5 to 101 Gy/s. The array was able to record beam profiles in both transverse and axial directions in relative agreement with measurements from EBT-XD radiochromic films (transverse) and Monte Carlo simulations (axial). A decrease in light output over time was observed, which might be caused by radiation damage in the matrix of the fibre and characterised by an exponential decay function. Full article

In radiation therapy (RT) for skin cancer, tissue-equivalent substances called boluses are widely used to ensure the delivery of an adequate dose to the skin surface and to provide a radioprotective effect for normal tissue. The aim of this study was to develop a new type of three-dimensional (3D) bolus for RT involving body parts with irregular geometries and to evaluate its clinical feasibility. Two 3D-printed boluses were designed for two patients with squamous cell carcinoma (SCC) of their distal extremities based on computed tomography (CT) images and printed with polylactic acid (PLA). The clinical feasibility of the boluses was evaluated by measuring the in vivo skin dose at the tumor site with optically stimulated luminescence detectors (OSLDs) and comparing the results with the prescribed and calculated doses from the Eclipse treatment planning system (TPS). The average measured dose distribution for the two patients was 94.75% of the prescribed dose and 98.8% of the calculated dose. In addition, the average measured dose during repeated treatments was 189.5 ± 3.7 cGy, thus demonstrating the excellent reproducibility of the proposed approach. Overall, the customized 3D-printed boluses for the RT of distal extremities accurately delivered doses to skin tumors with improved reproducibility. Full article

In radiation therapy, a bolus is used to improve dose distribution in superficial tumors; however, commercial boluses lack conformity to patient surface leading to the formation of an air gap between the bolus and patient surface and suboptimal tumor control. The aim of this study was to explore 3D-printing technology for the development of patient-specific conformal 3D-printed devices, which can be used for the radiation treatment of superficial head and neck cancer (HNC). Two 3D boluses (0.5 and 1.0 cm thick) for surface dose build-up and patient-specific 3D phantom were printed based on reconstruction of computed tomography (CT) images of a patient with HNC. The 3D-printed patient-specific phantom indicated good tissue equivalency (HU = −32) and geometric accuracy (DSC = 0.957). Both boluses indicated high conformity to the irregular skin surface with minimal air gaps (0.4–2.1 mm for 0.5 cm bolus and 0.6–2.2 mm for 1.0 cm bolus). The performed dose assessment showed that boluses of both thicknesses have comparable effectiveness, increasing the dose that covers 99% of the target volume by 52% and 26% for single field and intensity modulated fields, respectively, when compared with no bolus case. The performed investigation showed the potential of 3D printing in development of cost effective, patient specific and patient friendly conformal devices for dose verification in radiotherapy. Full article

Intravitreal injections have become the cornerstone of retinal care and one of the most commonly performed procedures across all medical specialties. The impact of hydrodynamic forces of intravitreal solutions when injected into vitreous or vitreous substitutes has not been well described. While computational models do exist, they tend to underestimate the starting surface area of an injected bolus of a drug. Here, we report the dispersion profile of a dye bolus (50 µL) injected into different vitreous substitutes of varying viscosities, surface tensions, and volumetric densities. A novel 3D printed in vitro model of the vitreous cavity of the eye was designed to visualize the dispersion profile of solutions when injected into the following vitreous substitutes—balanced salt solution (BSS), sodium hyaluronate (HA), and silicone oils (SO)—using a 30G needle with a Reynolds number (Re) for injection ranging from approximately 189 to 677. Larger bolus surface areas were associated with faster injection speeds, lower viscosity of vitreous substitutes, and smaller difference in interfacial surface tensions. Boluses exhibited buoyancy when injected into standard S1000. The hydrodynamic properties of liquid vitreous substitutes influence the initial injected bolus dispersion profile and should be taken into account when simulating drug dispersion following intravitreal injection at a preclinical stage of development, to better inform formulations and performance. Full article