Evaluation of novel 3D-printed and conventional thermoplastic stereotactic high-precision patient fixation masks for radiotherapy

Abstract

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.

Clinical value of styrofoam fixation in intracranial tumor radiotherapy

“…Veronika M. Miron et al. ( 9 ) fabricated a new comfortable positioning head mask via a 3D printing technique with higher fixation accuracy. M. Mattke et al.…”

Synthetic CTs for MRI-only brain RT treatment: integration of immobilization systems

“…For brain radiotherapy (RT) patients are commonly immobilized using an RT mask system, typically consisting of an RT thermoplastic mask, an RT mask holder, and an RT flat tabletop. This setup is applied during CT scans and during treatment at the linear accelerator [ 1 , 2 ]. In CT-based RT planning, these auxiliary devices are considered in the dose calculation, as radiation can penetrate through the devices from certain angles, and couch tops and immobilization devices have been reported to have dosimetric effects [ 3 ].…”

“…In our institution, the RT mask holder and RT tabletop available at the CT and the treatment machine cannot be used for MRI due to their MR incompatibility. Hence, a wooden mask holder was built for this purpose [ 1 , 2 ]. The accuracy of this setup should be regularly assured so that no large difference between the patient’s position in MRI and treatment can occur [ 1 , 8 ].…”