| Schedule | Constraint | Source |
|---|---|---|
| 60 Gy / 20 fx Moderate hypofractionation | V40.8 Gy <60% | CHHiP (Dearnaley 2016), CHHiP PROs (Wilkins 2015) |
| V60 Gy <3% | CHHiP (Dearnaley 2016), CHHiP PROs (Wilkins 2015) | |
| 70 Gy / 28 fx Moderate hypofractionation | V70 Gy ≤10% | ASTRO DVH Compendium 2026 |
| V65 Gy ≤10% | ASTRO DVH Compendium 2026 | |
| V40 Gy ≤35% | ASTRO DVH Compendium 2026 | |
| 78–80 Gy / 39–40 fx Conventional | V50 Gy <50% | ENZARAD protocol |
| V70 Gy <20% | ENZARAD protocol |
Acceptable limits; stricter ideal targets exist.
Quoted from eviQ 234 and ASTRO DVH Compendium 2026, checked 2026-10-14. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 60 Gy / 20 fx Nodes 44 Gy | V40.8 Gy <60% | CHHiP (Dearnaley 2016), CHHiP PROs (Wilkins 2015) |
| V60 Gy <3% | CHHiP (Dearnaley 2016), CHHiP PROs (Wilkins 2015) | |
| 68 Gy / 25 fx Nodes 45–50 Gy | V50 Gy <35% | POP-RT (toxicity) |
| V70 Gy <0.1% | POP-RT (toxicity) | |
| 78–80 Gy / 39–40 fx Nodes 54–60 Gy | V50 Gy <50% | ENZARAD protocol |
| V70 Gy <20% | ENZARAD protocol |
Quoted from eviQ 3657, checked 2026-09-23. Full table with references →
Ideal limits; applied to rectum and sigmoid.
Quoted from eviQ 4140, checked 2026-09-22. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 64–66 Gy / 32–33 fx 2 Gy per fraction | V50 Gy <50% | RAVES, RADICALS-RT |
| V66 Gy <30% | RAVES, RADICALS-RT | |
| 52.5 Gy / 20 fx 2.63 Gy per fraction | V40 Gy <60% | RADICALS-HD |
| V52.5 Gy <30% | RADICALS-HD |
Quoted from eviQ 4487, checked 2026-09-22. Full table with references →
The final segment of the large bowel, running from the rectosigmoid junction down through the pelvis to the anal canal. It lies directly behind the prostate and seminal vesicles, separated from them only by a thin fascial layer (Denonvilliers' fascia), which is why the anterior rectal wall sits so close to the prostate target.
The rectum stores stool before it leaves the body.
For prostate treatment the rectum is usually the organ that limits the plan. Late rectal toxicity — bleeding, urgency, frequency — is one of the side effects most closely tied to dose escalation, and it is driven mainly by how much of the rectum receives high dose. That is why rectal limits are written as a ladder of Vx values rather than one number: the DVH should stay under every rung.
Because the rectum's filling changes from day to day, the rectum you contour on the planning CT is a snapshot. Consistent bowel preparation, rectal spacers and daily image guidance all aim to make the treated anatomy match the planned one.
In gynecologic treatment the rectum lies directly behind the cervix, vagina and vaginal cuff. In post-operative plans the vaginal ITV may include the front wall of the rectum, so high rectal volumes are expected. In cervix brachytherapy the rectum's D2cc — the minimum dose to the most exposed 2 cc — is one of the main planning limits, added to the external beam dose in EQD2.
Gay 2012 gives two versions:
Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): one structure including the rectal wall and all contents; its Table 9 instruction reads "start contouring 10 cm superior to PTV then inferior to anal sphincter." Make sure your rectum and anus contours match the definitions behind your limits.
RTOG consensus panel atlas of male and female pelvic normal tissues. Citation as given in the eviQ reference list; not yet checked against the journal.
An editorial history of the UT Southwestern SABR constraint tables — often called the “Timmerman tables” — covering how they were developed and revised, and their relationship to AAPM TG-101 and NRG/RTOG protocols. Tables 2–11 separate serial tissues (listed with a volume, a volume max and a max point dose) from parallel tissues (listed with a critical volume and a critical-volume dose max). In Tables 2–7 a footnote defines “point” as ≤0.035 cm³; Tables 8–11 add a contouring-instructions column for each structure.