| Schedule | Constraint | Source |
|---|---|---|
| 60 Gy / 30 fx Standard course | As low as reasonably achievable; mean <5–10 Gy | eviQ 409 |
Where possible, spare the hippocampus opposite the tumor. Not applicable when it is involved.
Quoted from eviQ 409, checked 2026-09-25. Full table with references →
| Schedule | Constraint | Source |
|---|---|---|
| 30 Gy / 10 fx NRG CC001 | D100% ≤9 Gy (per protocol), ≤10 Gy (variation acceptable) | NRG CC001 |
| Max (0.03 cc) ≤16 Gy (per protocol), ≤17 Gy (variation acceptable) | NRG CC001 |
Both hippocampi, evaluated as one structure. The limits apply to the hippocampi, not to the avoidance region around them.
Quoted from NRG CC001, checked 2026-09-25. Full table with references →
A curved structure in the medial temporal lobe of each hemisphere, lying along the floor and inner wall of the temporal horn of the lateral ventricle. It runs from the amygdala in front, back and up toward the splenium of the corpus callosum.
The hippocampus, on the inner side of each temporal lobe, is central to forming new memories and to learning.
The hippocampus is central to forming new memories, and it holds a population of neural stem cells that radiation can injure. Hippocampal dose during whole-brain treatment has been linked to memory decline. RTOG 0933 and the randomized NRG CC001 trial showed that keeping the hippocampi to a low dose with IMRT reduces cognitive decline, which made hippocampal avoidance a planning technique of its own. In glioma plans, sparing the hippocampus away from the tumor is a secondary goal when it can be done without compromising the target.
The EPTN 2018 atlas defines the hippocampus as the gray matter medial to the temporal horn of the lateral ventricle, bordered medially by the quadrigeminal cistern, following Gondi et al. Its size varies with age and disease (2.8–4.0 cm³ in the literature it cites). For research it can be split into an anterior part (head) and a posterior part (body), using the lateral ventricle as a landmark for the anterior part. Delineation on T1-weighted MRI is essential.
The NRG CC001 protocol requires the hippocampi to be contoured according to the RTOG hippocampal contouring atlas, and names three structures: both hippocampi together, each side separately, and the hippocampal avoidance region grown from them. Gondi 2010 walks through the contouring and planning.
The European Particle Therapy Network contouring atlas for brain organs at risk on CT and MRI, with anatomical descriptions and boundaries. Citation checked against Crossref.
The NRG CC001 trial protocol (version date 26 September 2017, copy posted on ClinicalTrials.gov for NCT02360215). Arm 1 was standard whole-brain radiotherapy with 3D conformal fields; arm 2 was IMRT-based hippocampal avoidance, both 30 Gy in 10 fractions with memantine. Sections 5.2.4–5.2.8 define the CTV and PTV, the required structures (hippocampi, the hippocampal avoidance region, lenses, optic nerves and chiasm), the normalization, the per-protocol and variation-acceptable limits for the PTV, hippocampi and optic structures, and the planning priority order. DoseLab's hippocampal avoidance table quotes section 5.2.7 directly.
A planning paper describing how to contour the hippocampus, build the avoidance region and plan hippocampal-sparing whole-brain radiotherapy with helical tomotherapy and linac-based IMRT, 30 Gy in 10 fractions. Citation checked against Crossref.