| Schedule | Constraint | Source |
|---|---|---|
| 70 Gy / 28 fx Moderate hypofractionation | D0.035 cc ≤54 Gy | ASTRO DVH Compendium 2026 |
| V40 Gy ≤1% | ASTRO DVH Compendium 2026 | |
| 78–80 Gy / 39–40 fx Conventional | Peritoneal cavity V45 Gy <195 cc | QUANTEC |
Quoted from ASTRO DVH Compendium 2026 and eviQ 234, checked 2026-10-14. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 68 Gy / 25 fx Nodes 45–50 Gy | Bowel bag V45 Gy <158 cc | POP-RT (toxicity) |
| Bowel bag V60 Gy <6 cc | POP-RT (toxicity) | |
| 78–80 Gy / 39–40 fx Nodes 54–60 Gy | Peritoneal cavity V45 Gy <195 cc | QUANTEC |
25 fx values are acceptable limits; stricter ideal targets exist.
Quoted from eviQ 3657, checked 2026-09-23. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 36.25 Gy / 5 fx To PTV (40 Gy to CTV) | V30 Gy ≤1 cc | TROG NINJA |
| V18.1 Gy ≤5 cc | PACE-B |
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 | Peritoneal cavity V45 Gy <195 cc | QUANTEC |
| 52.5 Gy / 20 fx 2.63 Gy per fraction | D1 cc <46 Gy (EQD2 50 Gy) | eviQ 4487 |
Quoted from eviQ 4487, checked 2026-09-22. Full table with references →
The duodenum, jejunum and ileum. In the pelvis, loops of ileum are mobile and can drop down toward the bladder and seminal vesicles, especially when the bladder is empty or after pelvic surgery.
The small intestine absorbs most of the nutrients from food.
Small bowel matters most when the treated volume extends upward — pelvic lymph nodes, the prostate bed or large seminal vesicle volumes. For prostate-only treatment it is often far from the target, but a loop sitting just above the bladder can still come close. Acute effects include cramping and diarrhea; serious late effects such as obstruction are rare but significant.
In GI treatment small bowel is often the limiting organ: in rectal and anal cancer the elective nodal volumes rise into the pelvis where loops of bowel lie, and in pancreas and liver SBRT the bowel wraps around the target. The duodenum, the first part of the small bowel, has its own page.
In gynecologic treatment small bowel is usually the organ that limits the pelvic plan: the nodal volumes rise to the common iliac vessels or beyond, and after hysterectomy bowel loops often fall into the empty pelvis. NRG's GYN templates contour the bowel space (Spc_Bowel) — every slice from at least 2 cm above the PTV, including fat and mesentery — and a full bladder at simulation helps push bowel out of the field.
Sources use two different approaches:
Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): all loops of small bowel within 10 cm of the PTV in any direction, as one structure.
A limit written for loops does not apply to a bowel bag, or the reverse — match the structure to your source.
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.
RTOG consensus guidelines and atlas for delineating upper abdominal normal organs. Citation checked against Europe PMC.
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.