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  • br Table E Fig The

    2020-08-28


    Table E3, Fig. 2). The coronary artery segments all received 4 Gy, except for the RCA segments, which received 0.3 to 32.0 Gy from right megavoltage wide tangents (Table E4, Fig. 2).
    Anterior Thromboxane B 2
    or orthovoltage regimens
    For anterior electron or orthovoltage radiation therapy, the doses depended on the field borders, beam energy, and whether the beam was direct or oblique. For all regimens, the RV received higher doses than the LV because of its proximity to the anterior fields (left regimens: RV 8.0-15.6 Gy and LV 0.8-9.4 Gy; and right regimens: RV 1.9-6.0 Gy and LV 0.2-1.0 Gy; Table 1, Fig. 2, Table E3). The left oblique beams were angled toward the LV and gave higher LV doses (range, 8.6-9.4 Gy) than the left direct beams (range, 0.8-9.0 Gy). For the left oblique beams, the LV apex received the highest doses (range, 
    The coronary artery segments closest to the fields received the highest doses. For the left regimens, these were the LADCA and RCA proximal and mid segments (range, 2.9-46.2 Gy; Table 2), and for the right regimens, the RCA proximal and mid segments (range, 12.7-28.5 Gy; Table E4).
    Anterior megavoltage regimens
    Five anterior megavoltage regimens were used: 2 for left cancer, 2 for right cancer, and 1 regimen was the same in the left and right cancers. Most segments were in the radiation therapy fields and received >20 Gy (Fig. 1F-H, Tables 1, 2, E3, and E4).
    Practical Radiation Oncology: May-June 2019
    Cardiac segment radiation doses breast cancer 167
    Right ventricle
    LV: apex
    LV: lateral
    LV: inferior
    Left sided regimen
    LV: septal
    Right sided regimen
    LV: anterior
    Right ventricle
    Right ventricle
    LV: apex
    LV: apex
    LV: lateral
    LV: lateral
    LV: inferior
    LV: inferior
    LV: septal
    LV: septal
    LV: anterior
    LV: anterior
    Right ventricle
    Right ventricle
    LV: apex
    LV: apex
    LV: lateral
    LV: lateral
    LV: inferior
    LV: inferior
    LV: septal
    LV: septal
    LV: anterior
    LV: anterior
    Partially wide tangents, block posteriorly (48 Gy/24f) (4)
    Right ventricle
    Right ventricle
    LV: apex
    LV: apex
    LV: lateral
    LV: lateral
    LV: inferior
    LV: inferior
    LV: septal
    LV: septal
    LV: anterior
    LV: anterior
    D2cc ventricular myocardium (%)
    Fig. 4 D2cc (%) hotspot doses to the ventricular myocardium (right and left ventricles combined) in women receiving tangential or anterior electron regimens for breast cancer in Sweden (1958-2001) or Denmark (1978-2000). For further details on regimens 1-7, see Table E1 (available online at https://doi.org/10.1016/j.prro.2019.01.004). ) Medial border: 3 cm contralateral. y Block tapered inferiorly around the breast. z Block tapered inferiorly below the fifth rib, medial border: 3 cm contralateral. x Doses are shown in percent rather than Gy Thromboxane B 2 to enable a comparison based on patient anatomy rather than differing target dose. The spatial location of the D2cc ventricular myocardial hotspot was identified for each regimen/computed tomography combination using the dose range selection tool on the treatment planning system to highlight the voxels within the volume receiving this dose. Some hotspot volumes spanned >1 structure and were not always contiguous. Abbreviations: LV Z left ventricle; f Z fractions.
    Cobalt chain regimens
    Cobalt chain radiation therapy involved small, rect-angular, overlapping cobalt fields in a vertical line along the internal mammary chain.23 The short cobalt chain was above the level of the heart, and all segments received <1 Gy (Tables 1, 2, E3, and E4). The long cobalt chain covered part of the heart and delivered <1 Gy to 10 Gy to the cardiac segments.
    Interpatient variation
    Interpatient variability in the mean doses ranged from <1 Gy to 2 Gy for segments distant from the fields (Fig. 3). For segments near the fields, variability ranged from 3 Gy to 47 Gy for the left and 3 Gy to 27 Gy for the right regimens.
    For LV segments in the left tangents, the LV apex, lateral, septal, and anterior segments were near field edges, which resulted in dose variability of 8 Gy to 37 Gy (Figs. 2A, B, and 3). For the LV inferior segment, the dose varied by <6 Gy. For the left anterior electrons, the LV segment dose variability was <17 Gy. For the right tangents and right-anterior electrons, the LV segment dose variability was <1 Gy.
    For coronary artery segments and left tangents, dose variability for LADCA segments ranged from 14 Gy to 
    47 Gy (Figs. 2A, B, and 3). For coronary arterial seg-ments further from the fields, the dose variation was 1 Gy to 11 Gy. For the right tangents, the dose variability was <8 Gy. For the left-anterior electrons, the LADCA seg-ments and RCA proximal and mid segments were close to the fields, and for right-anterior electrons, the RCA proximal and mid segments were close to the fields. Dose variability for these segments ranged from 3 Gy to 41 Gy. For arterial segments further from the fields, the dose variability was <6 Gy.