New patient setup procedure using surface-guided imaging to reduce body touch and skin marks in whole-breast irradiation during the COVID-19 pandemic

This study aimed to assess the effectiveness of a new patient-setup procedure using surface-guided imaging during the coronavirus disease 2019 (COVID-19) pandemic for left-sided whole-breast irradiation with deep inspiration breath-hold. Two setup procedures were compared regarding patient positioning accuracy for the first 22 patients. The first was a traditional setup (T-setup) procedure that used a surface-guided system after patient setup with traditional skin marks and lasers. The second procedure involved a new setup (N-setup) that used only a surface-guided system. The positioning accuracy of the remaining 23 patients was assessed using a setup that combined marker reduction and the N-setup procedure. No significant difference was observed in positioning accuracy between the two setups. The positioning accuracy of the marker-reduction setup was within 3 mm in all directions. The N-setup procedure may be a useful strategy for preventing infection during or after the COVID-19 pandemic.

Cardiac dosimetric evaluation of deep inspiration breath-hold level variances using computed tomography scans generated from deformable image registration displacement vectors

There is a reduction in cardiac dose for left-sided breast radiotherapy during treatment with deep inspiration breath-hold (DIBH) when compared with treatment with free breathing (FB). Various levels of DIBH may occur for different treatment fractions. Dosimetric effects due to this and other motions are a major component of uncertainty in radiotherapy in this setting. Recent developments in deformable registration techniques allow displacement vectors between various temporal and spatial patient representations to be digitally quantified. We propose a method to evaluate the dosimetric effect to the heart from variable reproducibility of DIBH by using deformable registration to create new anatomical computed tomography (CT) scans. From deformable registration, 3-dimensional deformation vectors are generated with FB and DIBH. The obtained deformation vectors are scaled to 75%, 90%, and 110% and are applied to the reference image to create new CT scans at these inspirational levels. The scans are then imported into the treatment planning system and dose calculations are performed. The average mean dose to the heart was 2.5Gy (0.7 to 9.6Gy) at FB, 1.2Gy (0.6 to 3.8Gy, p < 0.001) at 75% inspiration, 1.1Gy (0.6 to 3.1Gy, p = 0.004) at 90% inspiration, 1.0Gy (0.6 to 3.0Gy) at 100% inspiration or DIBH, and 1.0Gy (0.6 to 2.8Gy, p = 0.019) at 110% inspiration. The average mean dose to the left anterior descending artery (LAD) was 19.9Gy (2.4 to 46.4Gy), 8.6Gy (2.0 to 43.8Gy, p < 0.001), 7.2Gy (1.9 to 40.1Gy, p = 0.035), 6.5Gy (1.8 to 34.7Gy), and 5.3Gy (1.5 to 31.5Gy, p < 0.001), correspondingly. This novel method enables numerous anatomical situations to be mimicked and quantifies the dosimetric effect they have on a treatment plan.