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Table 2 SBRT dose constraints. (TD = Target dose)

From: PROstate Multicentre External beam radioTHErapy Using a Stereotactic boost: the PROMETHEUS study protocol

Constraint Per-Protocol Minor Variation Major Variation
CTVsbrt D98a > 100% TD 95–100% TD < 95% TD
PTVsbrt D50a < 105% TD 105–110% TD > 110% TD
PTVsbrt D90a > 100% TD 95–100% TD < 95% TD
PTVsbrt D95a > 95% TD 90–95% TD < 90% TD
PTVsbrt D99a > 16 Gy 15–16 Gy < 15 Gy
PTVsbrt Dmax to 0.1cc < 110% TD 110–120% TD > 120% TD
PTVsbrt Dmax Not within a critical structure
Rectal Wall Dmax to 0.1cc < 17 Gy 17–17.5 Gy > 17.5 Gy
Rectal Wall V16 Gy < 0.5cc 0.5-1cc > 1cc
Rectal Wall V14 Gy < 3cc 3-5 cc > 5cc
Rectal Wall V12 Gy < 30% 30–40% > 40%
Rectal Wall V10 Gy < 40% 40–50% > 50%
Rectal Wall V8 Gy < 60% 60–70% > 70%
Rectal Mucosa Dmax to 0.1cc < 15 Gy 15–15.5 Gy > 15.5 Gy
Rectal Mucosa V14 Gy < 0.5cc 0.5-1cc > 1cc
Rectum Posterior Wall < 8.5 Gy 8.5–9.5 Gy > 9.5 Gy
Bladder Dmax to 0.1cc < 110% TD 110–120% TD > 120% TD
Bladder V19 Gy < 10cc 10-15cc > 15cc
Bladder V17 Gy < 15% 15–20% > 20%
Bladder V9 Gy < 50% 50–60% > 60%
Urethra PRV Dmax to 0.1cc < 110% TD 110–115% TD > 115% TD
Urethra PRV V105% TD < 5% 5–15% > 15%
Neck of Femurs Dmax to 0.1cc < 8 Gy 8–9 Gy 9 Gy
Penile Bulb Dmax to 0.1cc (Recommended) 100% TD 100–105% TD > 105% TD
Penile Bulb V10 Gy (Recommended) <3cc 3-5cc > 5cc
Intermediate Dose Spillage: ratio of volumes receiving 50% TD to 100% TD < 4 4–5 > 5
Total Monitor Units < 3× Dose in cGy 3–3.5× Dose in cGy > 3.5× Dose in cGy
High Dose Conformation: Volume receiving 100% of TD divided by volume of PTVsbrt < 1.1 1.1–1.2 > 1.2
  1. aWhere Urethra has been limited to 19 Gy, these volumes may exclude the urethra: eg. CTVsbrt D98 = CTVsbrt – Urethra PRV D98