Abstract:PurposeThe objective of this work is to outline a framework for dosimetric characterization that will comprehensively detail the clinical commissioning steps for 3D‐printed materials applied as patient support or immobilization devices in photon radiotherapy. The complex nature of 3D‐printed materials with application to patient‐specific configurations requires careful consideration. The framework presented is generalizable to any 3D‐printed object where the infill and shell combinations are unknown.MethodsA r… Show more
“…Within a study on headrests for Stereotactic Radio Surgery (SRS), 3D printed headrests had higher transmittance (98.89%) than standard SRS headrests (98.51%) [33]. Two studies demonstrated a methodology to measure beam attenuation with variable thickness and infill patterns [10,43].…”
“…Within a study on headrests for Stereotactic Radio Surgery (SRS), 3D printed headrests had higher transmittance (98.89%) than standard SRS headrests (98.51%) [33]. Two studies demonstrated a methodology to measure beam attenuation with variable thickness and infill patterns [10,43].…”
“…The 3D-printed plastic plates enable the peak dose in the mini-beam dose profile. Thanks to the fast prototyping of the 3D-printing technology, [22][23][24] it was not only possible to create several plastic plates with different thicknesses and angles to change FWHM and ctc as well as compensate for beam divergence but also to design mounting setups for reproducible positioning of the mini-beam collimator in the MultiRad. The relevance of aligning the mini-beam collimator properly in the center of the X-ray radiation field is illustrated in Figure S7.…”
BackgroundInterest in spatial fractionation radiotherapy has exponentially increased over the last decade as a significant reduction of healthy tissue toxicity was observed by mini‐beam irradiation. Published studies, however, mostly use rigid mini‐beam collimators dedicated to their exact experimental arrangement such that changing the setup or testing new mini‐beam collimator configurations becomes challenging and expensive.PurposeIn this work, a versatile, low‐cost mini‐beam collimator was designed and manufactured for pre‐clinical applications with X‐ray beams. The mini‐beam collimator enables variability of the full width at half maximum (FWHM), the center‐to‐center distance (ctc), the peak‐to‐valley dose ratio (PVDR), and the source‐to‐collimator distance (SCD).MethodsThe mini‐beam collimator is an in‐house development, which was constructed of 10 × 40 mm2 tungsten or brass plates. These metal plates were combined with 3D‐printed plastic plates that can be stacked together in the desired order. A standard X‐ray source was used for the dosimetric characterization of four different configurations of the collimator, including a combination of plastic plates of 0.5, 1, or 2 mm width, assembled with 1 or 2 mm thick metal plates. Irradiations were done at three different SCDs for characterizing the performance of the collimator. For the SCDs closer to the radiation source, the plastic plates were 3D‐printed with a dedicated angle to compensate for the X‐ray beam divergence, making it possible to study ultra‐high dose rates of around 40 Gy/s. All dosimetric quantifications were performed using EBT‐XD films. Additionally, in vitro studies with H460 cells were carried out.ResultsCharacteristic mini‐beam dose distributions were obtained with the developed collimator using a conventional X‐ray source. With the exchangeable 3D‐printed plates, FWHM and ctc from 0.52 to 2.11 mm, and from 1.77 to 4.61 mm were achieved, with uncertainties ranging from 0.01% to 8.98%, respectively. The FWHM and ctc obtained with the EBT‐XD films are in agreement with the design of each mini‐beam collimator configuration. For dose rates in the order of several Gy/min, the highest PVDR of 10.09 ± 1.08 was achieved with a collimator configuration of 0.5 mm thick plastic plates and 2 mm thick metal plates. Exchanging the tungsten plates with the lower‐density metal brass reduced the PVDR by approximately 50%. Also, increasing the dose rate to ultra‐high dose rates was feasible with the mini‐beam collimator, where a PVDR of 24.26 ± 2.10 was achieved. Finally, it was possible to deliver and quantify mini‐beam dose distribution patterns in vitro.ConclusionsWith the developed collimator, we achieved various mini‐beam dose distributions that can be adjusted according to the needs of the user in regards to FWHM, ctc, PVDR and SCD, while accounting for beam divergence. Therefore, the designed mini‐beam collimator may enable low‐cost and versatile pre‐clinical research on mini‐beam irradiation.
“…After evaluating the print accuracy, the masks were additively manufactured on the extrusion-based 3D printer Evolizer (EVO-tech GmbH, Schörfling, Austria). As material, acrylonitrile butadiene styrene (ABS), a standard 3D-printing filament, was used, as several studies have identified it as suitable for this application, also considering the attenuation properties [ 14 , 20 , 24 , 25 ]. Fig.…”
Purpose
For stereotactic radiation therapy of intracranial malignancies, a patient’s head needs to be immobilized with high accuracy. Fixation devices such as invasive stereotactic head frames or non-invasive thermoplastic mask systems are often used. However, especially stereotactic high-precision masks often cause discomfort for patients due to a long manufacturing time during which the patient is required to lie still and because the face is covered, including the mouth, nose, eyes, and ears. To avoid these issues, the target was to develop a non-invasive 3D-printable mask system with at least the accuracy of the high-precision masks, for producing masks which can be manufactured in the absence of patients and which allow the eyes, mouth, and nose to be uncovered during therapy.
Methods
For four volunteers, a personalized 3D-printed mask based on magnetic resonance imaging (MRI) data was designed and manufactured using fused filament fabrication (FFF). Additionally, for each of the volunteers, a conventional thermoplastic stereotactic high-precision mask from Brainlab AG (Munich, Germany) was fabricated. The intra-fractional fixation accuracy for each mask and volunteer was evaluated using the motion-correction algorithm of functional MRI measurements with and without guided motion.
Results
The average values for the translations and rotations of the volunteers’ heads lie in the range between ±1 mm and ±1° for both masks. Interestingly, the standard deviations and the relative and absolute 3D displacements are lower for the 3D-printed masks compared to the Brainlab masks.
Conclusion
It could be shown that the intra-fractional fixation accuracy of the 3D-printed masks was higher than for the conventional stereotactic high-precision masks.
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