Stereotactic Radiosurgery · Quick Reference

Quick Reference

Recommended imaging sequences, marginal doses, single-fraction limits, and organ-at-risk constraints at a glance

A consolidated reference for day-to-day planning: the MRI sequences worth acquiring per indication, the representative marginal/prescription doses for the main cranial and spine targets, the single-fraction maximum tolerated doses by lesion size, and the commonly cited organ-at-risk constraints. Every value here is a starting point for multidisciplinary planning, not a prescription; final dose and technique are individualized and follow the current constraint set adopted by your physics and radiation-oncology team.

Timoteo Almeida, MD, PhD | Department of Neurological Surgery

Orientation

This page is deliberately tabular. The detailed reasoning, evidence, and citations behind each number live on the corresponding disease and technical pages; here the goal is fast retrieval. Read the caveats in each caption — doses are representative ranges from the literature and converge differently across centers and platforms.

Part I

Recommended Imaging

1.MRI sequences by indication

Representative high-yield sequences (thin-slice, SRS-protocol MRI co-registered to planning CT). Adapt to local protocol.
Indication	Core sequences
Brain metastases	Thin-slice (≤1 mm) volumetric post-contrast T1 (MPRAGE/SPGR); consider black-blood post-contrast T1 to improve small-met detection; T2/FLAIR
Vestibular schwannoma	High-resolution T2 (CISS/FIESTA) for nerve/cochlea; thin post-contrast T1
Meningioma	Volumetric post-contrast T1; CT for hyperostosis/bone; consider DOTATATE PET for skull-base/dural tail
Pituitary/perisellar	Dedicated thin sellar pre/post-contrast T1; T2; define optic apparatus precisely
AVM	Catheter angiography (gold standard for nidus) + MR/MRA; CT/CTA as adjunct
Trigeminal neuralgia	High-resolution T2 (CISS/FIESTA) of the trigeminal nerve/REZ; post-contrast T1 for vessels
Spine SBRT	Thin-slice T1 and T2 co-registered to planning CT for cord/thecal sac and target; CT myelogram if MRI inadequate/hardware

Part II

Marginal / Prescription Doses

2.Cranial single-fraction targets

Representative single-fraction marginal doses (literature ranges; individualize by size, location, prior RT, and OAR proximity).
Target	Typical marginal dose
Brain metastasis	By size per RTOG 90-05 (see below); commonly 18–24 Gy
Vestibular schwannoma	~12–13 Gy (hearing/nerve preservation)
Meningioma (WHO 1 / benign)	~12–16 Gy
Pituitary — nonfunctioning adenoma	~14–16 Gy
Pituitary — functioning (secreting) adenoma	~18–30 Gy (higher for hormonal control)
AVM	~16–25 Gy (commonly ~18–23 Gy; obliteration is dose- and volume-dependent)
Glomus / paraganglioma	~13–16 Gy
Trigeminal neuralgia	~80–90 Gy maximum to the nerve/REZ (ablative)
Functional (e.g., VIM thalamotomy)	~130 Gy maximum (lesioning dose)

3.Single-fraction MTD by size (RTOG 90-05)

RTOG 90-05 maximum tolerated single-fraction doses by maximum tumor diameter (previously irradiated brain; widely used as a ceiling reference).
Maximum diameter	Single-fraction dose
≤ 20 mm	24 Gy
21–30 mm	18 Gy
31–40 mm	15 Gy

4.Spine SBRT schedules

Common spine schedules (choose by tumor, cord proximity, prior RT, and postoperative status; cord limits are protocol-specific).
Schedule	Note
16–24 Gy / 1 fx	High local control; steepest cord challenge, higher fracture risk
24 Gy / 2 fx	SC.24 regimen with randomized pain benefit
27 Gy / 3 fx	Common for larger volumes / postoperative beds
30–40 Gy / 5 fx	When cord or long segment limits hypofractionation; common postop

Part III

Organ-at-Risk Constraints

5.Commonly cited limits

Representative single-fraction OAR constraints (use the current adopted constraint set, e.g., TG-101/HyTEC; fractionated limits differ).
Structure	Representative single-fraction limit
Optic apparatus (nerves/chiasm)	Planning goal Dmax ≈ 8–10 Gy; risk rises through 10–12+ Gy, so hypofractionate when needed
Brainstem	Dmax ≈ 12.5–15 Gy
Spinal cord / thecal sac	Dmax ≈ 12.4–14 Gy (single fx); ~17 Gy/2 fx; ~20–22 Gy/3 fx
Cochlea (hearing preservation)	Mean ≈ 4 Gy (VS); keep as low as feasible
Lens	As low as achievable (≈ ≤5 Gy region)
Radionecrosis predictor (brain)	Track V12Gy (volume receiving ≥12 Gy)

Starting points, not prescriptions Every dose and constraint on this page is a representative literature value for orientation. Final prescription, fractionation, and OAR limits are individualized and must follow the current consensus documents (RTOG 90-05, TG-101, QUANTEC, HyTEC) and the constraint set your center has adopted. Cord and optic limits in particular are tighter in the reirradiation setting.

Key points

Imaging: thin-slice volumetric post-contrast T1 for most cranial targets; high-resolution T2 (CISS/FIESTA) for cranial-nerve targets (VS, TN); catheter angiography for AVM; co-registered thin T1/T2 for spine.
Representative cranial margins: VS ~12–13 Gy, benign meningioma ~12–16 Gy, nonfunctioning pituitary ~14–16 Gy (functioning ~18–30), AVM ~16–25 Gy, TN ~80–90 Gy, VIM thalamotomy ~130 Gy.
RTOG 90-05 single-fraction ceiling: 24 / 18 / 15 Gy for ≤20 / 21–30 / 31–40 mm.
Spine: 16–24 Gy/1 fx, 24 Gy/2 fx (SC.24), 27 Gy/3 fx, 30–40 Gy/5 fx; cord Dmax limits are protocol-specific and tighter on reirradiation.
OAR rough single-fraction limits: optic goal ~8–10 Gy, brainstem ~12.5–15 Gy, cord ~12.4–14 Gy, cochlea mean ~4 Gy — always defer to the adopted constraint set.

References

Shaw E, Scott C, Souhami L, et al. Single-dose radiosurgical treatment of recurrent previously irradiated primary brain tumors and brain metastases (RTOG 90-05). Int J Radiat Oncol Biol Phys. 2000;47(2):291–298.
Benedict SH, Yenice KM, Followill D, et al. Stereotactic body radiation therapy: AAPM Task Group 101. Med Phys. 2010;37(8):4078–4101.
Milano MT, Grimm J, Niemierko A, et al. HyTEC: single- and multifraction SRS dose/volume tolerances of the brain. Int J Radiat Oncol Biol Phys. 2021;110(1):68–86.
Sahgal A, et al. Spinal cord dose tolerance for SBRT. Int J Radiat Oncol Biol Phys. 2013;85(2):341–347.

Educational quick reference for neurosurgery and radiation-oncology trainees; not a treatment directive. All values are representative literature ranges; defer to current consensus documents and your center's adopted constraint set. Detailed evidence and citations are on the corresponding disease and technical pages.