Medical Physicist's Notes · LUCY™ 3D
AAPM MPPG 9.a (Halvorsen 2017) makes end-to-end QA mandatory for any SRS or SBRT programme, and adds a 72-hour on-site availability requirement that points to an in-house phantom. The LUCY 3D's per-component 0.1 mm tolerance and the inserts validated in the Sarkar 2016 head-to-head SRS phantom paper let it sit across all five links of that chain — from CT acquisition to dose readout — with every claim below sourced inline.
Stereotactic uncertainty is the sum of the chain. Each link below maps to a documented Lucy insert capability — the Sarkar 2016 paper is the published reference for the chamber-and-MR configurations.
CT acquisition + immobilisation
Phantom in the stereotactic frame on the simulator couch — geometric accuracy of CT slice spacing and in-plane resolution checked against the known phantom geometry.
Lucy insert
Multi-targeting geometric inserts (manufacturer)
MRI + image fusion
MR signal-generator and grid distortion inserts (Sarkar 2016 setup) characterise MRI geometric distortion across the FOV and surface CT-MRI fusion errors before they reach a stereotactic plan.
Lucy insert
MR signal generator + grid distortion insert
Planning system + dose calculation
Known target geometry inside known materials gives the planning system a reference forward-calculation; deviations surface algorithm or beam-data issues before patient cases.
Lucy insert
Multiple known-geometry targeting inserts
Couch alignment + IGRT (kV/CBCT/MV)
On-couch CBCT or MV imaging registers the phantom to the plan; the alignment chain is exercised end-to-end under the patient-like geometry.
Lucy insert
kV / MV / CBCT alignment QA
Dose delivery + readout
Exradin A16 micro chamber in the dose-measurement insert (Sarkar 2016 setup) gives absolute and relative dose at the stereotactic isocentre. Small-field-appropriate detector for the SRS isocentric volumes.
Lucy insert
A16 micro chamber + dosimetry insert
Source for the A16-on-Brainlab and MR-insert configurations: Sarkar V et al., J Radiosurg SBRT 4(3):213–223 (2016).
Three requirements from the practice guideline. None of them name Lucy — but each one is a spec a phantom has to clear to serve the programme.
Appropriate E2E phantoms for the scope of SRS-SBRT services offered
Halvorsen 2017 mandates the phantom set be appropriate to the programme — single-isocentre, multi-met, lung SBRT, frameless mask, MR-guided as relevant. Lucy 3D's insert system covers the cranial / frame and frameless SRS scope.
Available on site within 72 hours
Halvorsen 2017 sets a verbatim 72-hour maximum for E2E phantom availability. A phantom kept on site — not shared across institutions — meets this by default; IROC mail-in phantoms do not.
Each E2E step performed by the staff who will perform it clinically
The same physicist / RTT chain that runs patient cases must run the E2E check. A phantom whose workflow is reproducible in-house — not just at the vendor demo — is the practical fit.
Source: Halvorsen PH et al., AAPM-RSS MPPG 9.a, J Appl Clin Med Phys 18(5):10–21 (2017). PMC5874865.
Stereotactic uncertainty is the sum of the chain.
If the phantom contributes 0.1 mm per component, the phantom's own term in the budget stays in the noise — leaving you with a clean read on the machine, the imaging, the planning and the delivery.
Source: / LUCY 3D product page and brochure (1294-25).
Scope of this page
Lucy is not named in MPPG 9.a, TG-135 or TG-101 — those reports define the end-to-end QA requirement that any appropriate phantom must serve, and we cite that requirement. The peer-reviewed comparison evidence is the Sarkar 2016 head-to-head against StereoPHAN; we cite that. Treat this page as a fit-to-standard argument, not a vendor-vs-vendor comparison.
Sources cited on this page