Technical Note: Issues related to external marker block placement for deep inspiration breath hold breast radiotherapy

Abstract

The RPM marker block can be placed on the breast for DIBH treatments; however, caution should be used regarding surface dose effects. The two-dot marker block should not be used for block tilts beyond 20°. Marker block placement at a middle or superior position on the breast results in the strongest correlation with chest wall position.

A novel surrogate for motion management in external beam radiotherapy of breast cancer patients

“…The measured vertical motion amplitudes were 14.75 ± 0.05 and 15.05 ± 0.05 mm (mean ± SD) for the NRS and TMB, respectively, when measured with the untilted surrogate. When tilting the surrogates, a larger tilt resulted in a larger measured amplitude, but similar for both surrogates; this has been previously reported for the TMB [16]. No significant differences between the surrogates were found in tracking performance, The NRS has a base with a diameter of 38 mm and reflective markers affixed on a stalk with 30 mm spacing between them, i.e., the same distance as on the TMB.…”

“…Several studies have shown that a surrogate/marker positioned on the xiphoid process or the sternum improved correlation to breast/thoracic wall compared to a position on the abdomen [11,17,21], in general the closer the surrogate is placed to the breast in cranio-caudal and lateral directions the better [8,16]. NRS' narrow base enabled positioning of the surrogate on the sternum at the level of the papilla.…”

“…Several commercial methods to monitor and regulate respiration during DIBH exist [5], and the most common methods are: external surrogate with an optical or infrared camera [1,3,4,[6][7][8][9][10], spirometry [11], or surface monitoring with optical cameras and structured light [12][13][14][15]. When using a reflective surrogate, the closer the surrogate is placed to the treated breast in the cranio-caudal and lateral direction the better it represents the motion of the breast [8,16,17]. However, when positioning the surrogate close to the target, the surrogate will often be positioned in the path of the treatment beam.…”

“…The commercially available two-marker real-time position management (RPM) box (TMB) was not suitable for placement within the treatment beams due the amount of material it consists of, as this may result in an unwanted skin reaction. Furthermore, due to the relatively wide lateral extent of the TMB, it may be positioned with a tilt toward the treated breast on some patients [16]. Therefore, a novel respiratory surrogate (NRS) was designed consisting of less material and with a smaller footprint to (1) allow placement within the treatment beam and (2) enable a stable placement of the reflective surrogate on the sternum approximately at the level of the papilla.…”

Target position reproducibility in left‐breast irradiation with deep inspiration breath‐hold using multiple optical surface control points

“…In our study, the RPM block was placed on the patients' abdomen, midway between the xyphoid process and the umbilicus, and a 5 mm gating window was selected, as recommended by the RPM manufacturer and in recent works . The positioning of the fiducial block on the sternum or breast can result in improved DIBH reproducibility, but concerns are associated to the lateral block tilt and surface dose effects . A reduced gating window can also contribute to increase targeting accuracy, but there is the evidence that large errors in CW position can occur despite a small gating window .…”