Per-patient selection · Breast Positioning
Per-patient supine vs prone breast-positioning selection is a clinical decision shaped by breast volume, dosimetric trade-offs, DIBH compatibility, patient tolerance and setup reproducibility. This page is the eight-factor selection matrix used at simulation to lock the per-patient workflow.
| Factor | Supine | Prone |
|---|---|---|
| Breast volume | Routine for ≤ B-cup; manageable up to C-cup with appropriate cushion | Recommended for ≥ C-cup; mandatory consideration ≥ D-cup where supine breast crosses the midline |
| Ipsilateral lung dose | V20 typically 12–18 % for tangential left-breast (Gy) | V20 typically drops 30–50 % vs supine for larger breasts; lung kept out of the high-dose tangent path |
| Cardiac dose (left-side) | Heart-mean-dose typically 2–5 Gy free-breathing; DIBH reduces to 1–2 Gy | Heart-mean-dose 1–3 Gy free-breathing; less DIBH-dependent due to cardiac displacement |
| Skin dose | Higher at the breast-axilla junction; skin-fold dose can drive moist desquamation | Lower at the breast-axilla junction; breast tissue drapes away from the chest wall |
| Patient tolerance | Most patients comfortable; lengthy DIBH protocols (≥ 20-min total breath-hold time) can be tiring | More demanding posture; requires patient mobility + comfort assessment; some patients cannot tolerate prone for the fraction duration |
| Setup reproducibility | Workflow standardised; daily CBCT verification well-established | Requires breast-board angle indexing + cushion conformal hold; CBCT visualisation can be more challenging for some breast geometries |
| Combined with DIBH | Standard combination; T-grip + breast cushion + indexed board hold the DIBH posture across fractions | DIBH less commonly combined with prone; the prone posture displaces heart away from chest wall already |
| Bilateral or chest-wall | Standard for chest-wall and bilateral breast workflows; tangential field arrangement is direct | Not typically used for bilateral or chest-wall workflows; prone is single-breast geometry |
How to use this matrix
At simulation, the radiation oncologist and physicist score each factor against the patient profile. Breast volume and ipsilateral lung dose typically drive the selection; cardiac dose for left-side cases shifts the balance toward DIBH-supine unless the prone advantage is large. Patient tolerance is the over-ride — a patient who cannot tolerate prone for the fraction duration is treated supine regardless of dosimetric advantage. The accessory family covers both modes, so the per-patient decision is purely clinical, not constrained by equipment.
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