MR-guided breast radiotherapy: feasibility and magnetic-field impact on skin dose

Abstract

The UMC Utrecht MRI/linac (MRL) design provides image guidance with high soft-tissue contrast, directly during radiotherapy (RT). Breast cancer patients are a potential group to benefit from better guidance in the MRL. However, due to the electron return effect, the skin dose can be increased in presence of a magnetic field. Since large skin areas are generally involved in breast RT, the purpose of this study is to investigate the effects on the skin dose, for whole-breast irradiation (WBI) and accelerated partial-breast irradiation (APBI). In ten patients with early-stage breast cancer, targets and organs at risk (OARs) were delineated on postoperative CT scans co-registered with MRI. The OARs included the skin, comprising the first 5 mm of ipsilateral-breast tissue, plus extensions. Three intensity-modulated RT techniques were considered (2× WBI, 1× APBI). Individual beam geometries were used for all patients. Specially developed MRL treatment-planning software was used. Acceptable plans were generated for 0 T, 0.35 T and 1.5 T, using a class solution. The skin dose was augmented in WBI in the presence of a magnetic field, which is a potential drawback, whereas in APBI the induced effects were negligible. This opens possibilities for developing MR-guided partial-breast treatments in the MRL.

MRI and CT imaging for preoperative target volume delineation in breast-conserving therapy

“…Moreover, preoperative target volumes would probably be more stable in the absence of seroma formation, and not being subject to seroma shrinkage [17,31]. The advantages of preoperative CE-MRI for treatment planning will be further studied with respect to the dosimetric consequences [32]. CE-MRI in supine position could also be used for other purposes.…”

Online Adaptive Radiation Therapy

“…This may lead to an elevation of skin dose in the region surrounding the treatment volume. 82 This, however, may be an advantage in locally advanced breast cancers (LABCs) that involve the superficial tissues including the skin.…”

Future of medical physics: Real‐time MRI‐guided proton therapy

“…These may be above the patient, or scattered from the patient on the exit side. 41,42,43,44,45,46,47,48,49,50 With MRPT, the therapeutic proton beam (being charged particles), is subject to the Lorentz deflection force when transporting towards the patient at the center of the MRI, as well as within the patient while slowing down. The planning process is best broken down into two components as described in Fig.…”