PMC7085359_01
Targets segmental setting of TSP in an axial view of CT. Abbreviations: PTV-CW: chest wall region of PTV (blue); PTV-IM: internal mammary nodes region of PTV (red); PTV-EB: external breast region of PTV (green).
BMRI2020-7131590.001.jpg
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fig1
Figure 1 shows an exemplary patient axial CT image with this anatomic feature. TSP, PTV was divided into four regions: supra/infraclavicular region (PTV-SC), internal mammary nodes region (PTV-IM), chest wall region (PTV-CW), and external breast region (PTV-EB) as shown in Figure 1.
(a) Beam view of PTV-SC and PTV. (b) Beam view of the PTV exclude the PTV-SC. Abbreviations: Beam of PTV: cyan; Beam of PTV-SC: orange; Beam of PTV-IM: red; Beam of PTV-CW: blue; Beam of PTV-EB: green.
BMRI2020-7131590.002.jpg
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fig2
TSP uses 9 IMRT fields with single isocenter at the center of mass of the PTV showed in Figure 2. The beam angles of the two fields for PTV-SC were arranged to avoid the spinal cord and the humeral head with half-beam block inferiorly (Figure 2(a)). The jaw of every field was set to fit each region (PTV-CW, IM, and EB) as shown in Figure 2(b), and the overlap distance of jaws in the superior-inferior direction were about 1-2 cm from our planning experience, to avoid the hot or cold dose points near the segmented regions.