br Cobalt chain regimens br

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 12-O-tetradecanoyl phorbol-13-acetate 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.
Hotspot doses were located in the LV apex, LV ante-rior, and LADCA segments for most left regimens, and in the RV, RCA proximal, and RCA mid segments for most right regimens (Figs. 4 and 5). The order of the segments according to higher-versus-lower doses was the same as in the typical CT scan for 91% of LV segment and regimen combinations, 91% of whole coronary artery and regimen combinations, and 81% of coronary artery segment and regimen combinations (Tables E5 and E6; available online at https://doi.org/10.1016/j.prro.2019.01.004).
Correlations between cardiac segments
The doses to all LV and LADCA segments were highly correlated with doses to the whole heart (range of correlation coefficients, 0.7-0.9; all P < .0001; Fig. 6).
LMCA
LADCA prox
LADCA mid LADCA dist RCA prox RCA mid RCA dist RCA pd Cx
Left sided regimen
Right sided regimen
LMCA
LADCA prox
LADCA mid LADCA dist RCA prox RCA mid RCA dist RCA pd Cx 
Wide tangents, divergent (41 Gy/22f)* (2) Direct electron internal mammary chain (40 Gy/10f) (5) LMCA LADCA prox LADCA mid LADCA dist
RCA prox
RCA mid
RCA dist RCA pd Cx
LADCA prox
LADCA prox
LADCA mid
LADCA mid
LADCA dist
LADCA dist
RCA prox
RCA prox
RCA mid
RCA mid
RCA dist
RCA dist
RCA pd
RCA pd
Cx
Cx
LMCA Partially wide tangents, block posteriorly (48 Gy/24f) (4)
LADCA prox
LADCA prox
LADCA mid
LADCA mid
LADCA dist
LADCA dist
RCA prox
RCA prox
RCA mid
RCA mid
RCA dist
RCA dist
RCA pd
RCA pd
Cx
Cx
D0.5cc main coronary arteries (%)
y Block tapered inferiorly around breast. z Block tapered inferiorly below the fifth rib, medial border: 3 cm contralateral x Doses are shown in percent rather than Gy to enable a comparison based on patient anatomy rather than differing target dose. The spatial location of the D0.5cc main coronary arteries hotspot was identified for each regimen and 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: LMCA Z left main coronary artery; LADCA Z left anterior descending coronary artery; RCA Z right coronary artery; Cx Z circumflex coronary artery; f Z fractions; IMC Z internal mammary chain; prox Z proximal; dist Z distal; pd Z posterior descending.