While developing a breast thermotherapy device to facilitate MR-guided thermo-chemotherapy for the intact breast, it is crucial to ensure effective breast immobilization. It is critical that the device provides consistent positioning throughout the procedure, thereby enabling accurate treatment delivery. In addition, it is equally important that the device provides sufficient comfort to enable patients to endure the procedure.

To quantify these aspects, a design evaluation was conducted (METC approved, N-WMO, MEC-2024-0767). Ten healthy female participants were assessed in the prone position using a clinically established breast MR imaging setup. This provided baseline data and a framework for designing a new breast immobilization method, which was subsequently evaluated using the same approach and healthy volunteers. The breast was submerged in water, and its immobilization (i.e. intra- and inter-positioning displacement) was monitored with Electromagnetic Tracking (EMT) sensors for a duration of 90 minutes. Afterwards, participants were asked to assess comfort in terms of perceived (dis)comfort, local perceived discomfort, local perceived pressure points, and positioning complaints by completing a questionnaire.

Eight out of the 10 participants completed the evaluation for the full treatment duration of 90 minutes on the MR setup. The prone position held with the MR setup was scored with a median discomfort score of 5.0 (IQR 4.0-6.0). The newly developed immobilization method made it feasible for all 10 participants to maintain the prone position for 90 minutes, reporting a median discomfort score of 4.5 (IQR 2.3-5.0). The immobilization results obtained with the new immobilization method showed intra-positioning displacements of the nipple within a margin of 8 mm, whereas intra-positioning displacements of the nipple using the MR imaging platform were recorded within a margin of 9 mm. Inter-positioning displacements of the breast with the new immobilization method were recorded within a margin of 36 mm, while results with the MR setup were recorded within a margin of 51 mm.

Thus, the new immobilization method improved comfort and facilitated that all the volunteers endured the 90 minutes evaluation. However, a reduction in breast displacement was not necessarily observed. Further studies with a larger sample size are needed to support generalizable findings.