Dayna Bodensteiner, RT(R)(T), CMD Clinical Marketing Manager, Sun Nuclear, a Mirion Medical company
Modern linear accelerators are more capable, and more geometrically demanding, than the machines daily QA programs were originally built to check. SRS and SBRT margins have contracted to 1–3 mm, patient-specific QA is increasingly satisfied by calculation-based methods rather than measurement, and the AAPM’s own guidance (TG-198, MPPG 8.b, TG-100) now points toward a daily check that is both more comprehensive and more clinically relevant. Two independent academic centers, Cedars-Sinai Medical Center and NYU Langone Health, recently presented their evaluations of a new integrated daily QA platform, Daily QATM 4 Pro (Sun Nuclear, a Mirion Medical company), at AAPM (American Association of Medical Physicists) in Vancouver, British Columbia. This article summarizes their findings, evaluating whether an integrated, single-session approach belongs in their own QA programs.
Why Integration Matters
When dosimetric, geometric, and imaging checks are performed as separate tests on separate devices, the interaction between them is invisible. Published work cited in the Cedars-Sinai evaluation illustrates the cost of this blind spot: a 1 mm isocenter error has been reported to cost 5–6% of SRS target coverage, a 0.5 mm setup error has been linked to a 20% loss in GTV D99% for sub-centimeter targets, and a 0.19 mm MLC offset has been associated with more than 5% coverage loss in multi-target SRS. Because geometric and dosimetric measurements are traditionally acquired on different phantoms and stored in different databases, none of these interactions are visible to a program running serial, single-purpose tests. Additionally, the underlying hardware was never built to run active or imaging Winston-Lutz tests. Daily QA 4 Pro was designed specifically to remove that compromise, combining multiple checks in a single QA platform.
The Platform
Daily QA 4 Pro combines three upgrades on a single, indexed phantom: eight off-axis tungsten fiducials visible on kV, MV, and CBCT with an SGRT-optimized surface (imageable); a six-degree-of-freedom adapter, CT- scannable and plannable to ±1.5° roll/pitch/yaw (indexable); and a 3D diode array — 229 SunPoint 2 diodes across the main board plus two side boards — that enables active Winston-Lutz via 2×2 fields. From one indexed setup, the device runs four tests in automate mode in roughly 15–20 minutes: positioning/repositioning (kV/MV/CBCT and SGRT versus treatment isocenter), active Winston-Lutz (radiation isocenter coincidence), open-field dosimetry (output, symmetry, flatness, beam center, penumbra, field size), and — as a weekly, ten- minute add-on — imaging Winston-Lutz (imaging isocenter accuracy, gantry/collimator/couch accuracy, imager offset, SID, and MLC accuracy). Active Winston-Lutz reconstructs a star shot in 3D from gantry, collimator, and couch rotations without a separate BB phantom, using the diode array itself as the reference; imaging Winston- Lutz treats the eight fiducials as a single rigid body and maps each detected error — panel offset, gantry/couch/collimator angle, gantry pitch, MLC accuracy — back to its source.
Sensitivity, Reproducibility, and TPS Agreement at Cedars-Sinai Medical Center
Maria Bellon, MS, DABR, and colleagues at Cedars-Sinai Medical Center characterized the device’s measurement floor and sensitivity on a Varian TrueBeam with a Millennium MLC with 6 FFF. Repeatability and reproducibility testing, which included three runs at nominal setup, with the device fully removed and replaced between each — showed variation below 0.1 mm across every parameter tested, including active Winston-Lutz minimum tangent radius measurements (gantry, couch, and collimator) and open-field beam centers. Sensitivity testing applied couch shifts of 0.5, 1, 1.5, and 3.0 mm in all three axes simultaneously, showed accuracy levels
(<0.1mm) that approached typical SRS tolerance, confirming that the device resolves clinically meaningful displacement rather than measurement noise. Additionally, beam-center tracking accuracy was consistent across field sizes from 2cm × 2cm to 20 × 20cm (average tracking error approximately 0.1 mm), and output factors agreed with the treatment planning system to within 0.64%. Lastly, a small-field profile comparison provided further validation that a single session can plausibly support dosimetric, radiation-geometric, and imaging verification together.
First Clinical Experience and Workflow Impact at NYU Langone Health
David Barbee, PhD, DABR, and the radiation oncology physics team at NYU Langone Health reported the first clinical experience with Daily QA 4 Pro across six linear accelerators, integrated with the SunCHECK environment. Active Measurement Winston-Lutz demonstrated a noise floor of 0.07 mm and a minimum detectable shift of 0.14 mm (95% CI) for isolated positional shifts up to 1.5 mm, with composite isocenter results comparable to two years of monthly BB-based Winston-Lutz history on the same machines. Imaging Winston- Lutz performed even better on positioning sensitivity, with a 0.05 mm noise floor and 0.10 mm minimum detectable shift (N = 36), and additionally quantified kV/MV panel offset, gantry pitch and roll, and MLC field center/width per gantry angle. The team’s evaluation carried one important caveat: because active measurement Winston-Lutz derives the Z isocenter position from lateral diode arrays under an assumption of ideal gantry delivery, a gantry angle error is geometrically magnified into an apparent Z-axis shift. Based on this relationship, NYU Langone recommends keeping gantry angle error below ±0.2° to stay within a 0.5 mm goal, and below ±0.5° to stay within a 1.0 mm hard limit — a practical calibration point for programs adopting the technique. On workflow, replacing serial IGRT, beam constancy, and off-axis Winston-Lutz measurements with the integrated sequence reduced total measurement time from roughly 32 minutes to 16 minutes per linac in NYU Langone’s comparison, with SGRT included only in the integrated workflow.
Implications for Practice
Taken together, the two evaluations support a QA model consistent with current AAPM guidance: a single indexed device runs the comprehensive daily suite, executed by radiation therapists in automate mode, while the qualified medical physicist retains responsibility for test selection and sign-off (TG-198). Because the daily measurement set is richer, monthly QA can be scaled back to checks that are genuinely additive rather than duplicative, and tests can be selected by clinical risk rather than by habit (MPPG 8.b; TG-100). The resulting shift lets physics staff spend relatively more time interpreting trends and setting action limits and relatively less time on data acquisition itself. This direction, multiple authors have described as a maturing of the physicist’s role from technology caretaking toward a more clinically- and scientifically-oriented service (Medical Physics 3.0).
Conclusion
Independent data from Cedars-Sinai Medical Center and NYU Langone Health show that daily dosimetric, geometric and imaging verification can be performed with a single indexed setup, in less time, without sacrificing robustness. Programs considering adoption should assess how an automated daily suite fits their workflow and staffing and verify their machines meet its performance assumptions. As per-patient measurement shifts toward calculation-based methods, daily QA becomes the primary measurement-based verification of machine performance — the role Daily QA 4 Pro is purpose-built to fill.
References
1. Bellon M. Daily QA 4 Pro: Redefining Daily QA. Presented at AAPM, Vancouver BC, July 19, 2026.
2. Barbee D. First Clinical Experience with Daily QA 4 Pro. Presented at the AAPM Chapter/COMP meeting, July 21, 2026.
3. Guckenberger M, Meyer J, Wilbert J, Baier K, Bratengeier K, Vordermark D, Flentje M. Precision required for dose-escalated treatment of spinal metastases and implications for image-guided radiation therapy (IGRT). *Radiother Oncol.* 2007;84(1):56–63. doi:10.1016/j.radonc.2007.05.021
4. Nakano H, Tanabe S, Utsunomiya S, Yamada T, Sasamoto R, Nakano T. Effect of setup error in the single- isocenter technique on stereotactic radiosurgery for multiple brain metastases. *J Appl Clin Med Phys.* 2020;21(12):155–165. doi:10.1002/acm2.13081
5. Prentou G, Pappas EP, Prentou E, et al. Impact of systematic MLC positional uncertainties on the quality of single-isocenter multi-target VMAT-SRS treatment plans. *J Appl Clin Med Phys.* 2022;23(8):e13708. doi:10.1002/acm2.13708.
6. Peng JL, Kahler D, Li JG, Amdur RJ, Vanek KN, Liu C. Feasibility study of performing IGRT system daily QA using a commercial QA device. *J Appl Clin Med Phys.* 2011;12(3):3535. doi:10.1120/jacmp.v12i3.3535
7. Hanley J, Dresser S, Simon WE, Flynn R, Klein EE, Letourneau D, et al. AAPM Task Group 198 Report: An implementation guide for TG 142 quality assurance of medical accelerators. *Med Phys.* 2021;48(10):e830–e885. doi:10.1002/mp.14992.
8. Krauss D, et al. AAPM Medical Physics Practice Guideline 8.b: Linear accelerator performance tests. *J Appl Clin Med Phys.* 2023
9. Huq MS, Fraass BA, Dunscombe PB, Gibbons JP Jr, Ibbott GS, Medin PM, Mundt AJ, Mutic S, Palta JR, Rath F, Thomadsen BR, Yorke ED. The report of Task Group 100 of the AAPM: Application of risk analysis methods to radiation therapy quality management. *Med Phys.* 2016;43(7):4209–4262. doi:10.1118/1.4947547
10. Samei E, Pawlicki T, Bourland D, et al. Redefining and reinvigorating the role of physics in clinical medicine: A report from the AAPM Medical Physics 3.0 Ad Hoc Committee. *Med Phys.* 2018;45(9):e783–e789. doi:10.1002/mp.13087
11. Pawlicki T, Mundt AJ. Continued emphasis on quality and safety jeopardizes clinical medical physics careers in radiation oncology: What can be done about it? *J Appl Clin Med Phys.* 2019;20(2):4–6. doi:10.1002/acm2.12532
