| Schedule | Constraint | Source |
|---|---|---|
| 41.4 Gy / 23 fx Preoperative | Avoid hotspots | eviQ 1861 |
| 50.4 Gy / 28 fx Definitive; also 50 Gy / 25 fx | Loops max <50 Gy | eviQ 1865 |
Quoted from eviQ 1861 and eviQ 1865, checked 2026-09-29. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 50.4 Gy / 28 fx 45–54 Gy / 25–30 fx | Loops V15 Gy <120 cc | QUANTEC summary |
| Bowel cavity V45 Gy <195 cc | QUANTEC summary |
Avoid hotspots. Each limit applies only to the contouring method it names.
Quoted from eviQ 3581, checked 2026-09-29. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 42–54 Gy / 3 fx Liver metastases | D0.1 cc ≤25.2 Gy | UK SABR consensus 2022 |
| D5 cc ≤17.7 Gy | UK SABR consensus 2022 | |
| 27.5–60 Gy / 5 fx HCC or metastases | D0.1 cc ≤30 Gy (optimal), ≤35 Gy (mandatory) | UK SABR consensus 2022 |
| D10 cc ≤25 Gy | UK SABR consensus 2022 |
Quoted from eviQ 4026, checked 2026-09-29. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 45–50.4 Gy / 25–28 fx Long course | V35 Gy <180 cc, V40 Gy <100 cc, V45 Gy <65 cc | RTOG 0822 |
| No volume ≥50 Gy | RTOG 0822 | |
| Bowel cavity V45 Gy <195 cc | QUANTEC summary | |
| 25 Gy / 5 fx Short course | Loops D200 cc <20 Gy, D20 cc <25 Gy | RCR rectal IMRT guidance |
| Bowel cavity D200 cc <23 Gy | RCR rectal IMRT guidance |
Use the limits that match how you contour bowel — individual loops or the bowel cavity.
Quoted from RTOG 0822 and QUANTEC summary and RCR rectal IMRT guidance, checked 2026-09-29. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 50.4–54 Gy / 28–30 fx Dose-painted IMRT | Loops V30 Gy <200 cc, V35 Gy <150 cc, V45 Gy <20 cc | RTOG 0529 |
| Max <50 Gy | RTOG 0529 |
An NRG template applies the same values to the whole bowel space.
Quoted from eviQ 1860, checked 2026-09-29. 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.