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Dosimetric characterization of a nanophotonic scintillator and applications to real-time in-vivo total body irradiation dosimetry

Published 14 Jun 2026 in physics.med-ph | (2606.16007v1)

Abstract: Purpose: Recent advances in metasurface photonics and manufacturing have enabled a nanophotonic surface coating to be applied to conventional scintillators, which has been shown to significantly improve light yield. However, the dosimetric properties of such coatings has not been established. We performed the first dosimetric characterization of a nanophotonic scintillator and explored clinical application to real-time in-vivo total body irradiation (TBI) dosimetry. Methods: A 4.5x1.5 cm cerium-doped yttrium aluminum garnet (YAG:Ce) scintillator, half patterned with the nanophotonic structure, half left unpatterned, enabled direct comparison between conventional and nanophotonic surfaces. The scintillator was placed in a 3D-printed light-tight box with an off-axis CMOS camera and irradiated with a clinical linear accelerator. Absolute dosimetry was done with dose-calibrated radiochromic film. For TBI, the scintillator was positioned on an anthropomorphic phantom in a TBI booth, with signal measured by both CMOS and consumer-grade phone cameras under different room lighting conditions. Results: The nanophotonic scintillator showed a 4.1x increase in signal and a 3.7x increase in contrast-to-noise ratio versus the conventional scintillator. Both scintillators exhibited dose-rate independence and linear dose response, with modest energy dependence. For TBI, the nanophotonic scintillator produced a clearly detectable signal with both CMOS and phone cameras, whereas the conventional scintillator signal was undetectable. Conclusions: Nanophotonic structures significantly enhance light output of conventional scintillators without impacting their dosimetric properties. Nanophotonic scintillators may enable real-time in-vivo TBI dosimetry. Future work should investigate this technology for improved dosimetry equipment and X-ray imaging detectors.

Summary

  • The paper demonstrates a 4.1-fold increase in light yield from nanophotonic patterned YAG:Ce scintillators, enabling reliable real-time dosimetry.
  • It reports a 3.7-fold improvement in contrast-to-noise ratio and confirms dose-rate independence and linear response across clinical ranges.
  • The study highlights the potential of using accessible camera systems for TBI dosimetry while paving the way for broader applications in medical imaging.

Dosimetric Characterization of Nanophotonic Scintillators: Advancements for Real-Time In-Vivo Total Body Irradiation Dosimetry

Introduction

This study presents the first comprehensive dosimetric evaluation of nanophotonic scintillators—specifically cerium-doped yttrium aluminum garnet (YAG:Ce) scintillators with engineered nanophotonic surface coatings—and investigates their application to real-time in-vivo total body irradiation (TBI) dosimetry. Motivated by the limitations in signal yield from conventional scintillators and the resulting requirement for expensive amplification hardware, the work exploits recent nanophotonic advances to enhance scintillator light yield, thereby enabling the use of cost-efficient, widely available camera systems for clinical dosimetry.

Experimental Design and Methods

The scintillator evaluated was a 4.5 cm × 1.5 cm YAG:Ce sample, with half its surface patterned using a nanophotonic structure (subwavelength period 450 nm), enabling direct intra-device comparison. Fabrication involved nanoimprint lithography with a polymer stamp and subsequent deposition and annealing of chalcogenide glass, capped by silica for protection. Dosimetric properties were characterized via irradiation with clinical linear accelerators, using CMOS and consumer-grade phone cameras for signal acquisition within a light-tight experimental setup. Dose calibration utilized radiochromic film, rigorously registered to scintillator signal readings.

Dosimetric Performance Analysis

Light Output and Signal Enhancement

Nanophotonic structuring resulted in a 4.1-fold increase in scintillation light yield compared to conventional YAG:Ce scintillators. This signal enhancement was sustained across clinically relevant experimental conditions.

Contrast-to-Noise Ratio and Real-Time Imaging

The increased light yield translated into a 3.7-fold improvement in contrast-to-noise ratio (CNR) for the nanophotonic scintillator, plateauing at 200 ms camera exposure. High CNR with reduced exposure enables real-time dosimetry with excellent temporal resolution, an essential feature for clinical applications such as TBI.

Dose-Rate Independence and Linearity

Both nanophotonic and conventional scintillators exhibited dose-rate independence, with less than 0.5% variation in signal response across dose rates (400–2000 MU/min). Signal response maintained strict linearity with delivered dose for all tested photon and electron energies, with R2=1.00R^2 = 1.00 in all fits. These results confirm the absence of any deleterious impact of the nanophotonic surface layer on the fundamental dosimetric behavior of the base scintillator.

Energy Dependence and Calibration

A modest energy dependence was observed for both photon and electron beams. Calibration curves displayed statistically significant differences in slopes across energies, reflecting minor but non-negligible variations; all photon measurements were within 2.5% and electron measurements within 4% of their respective common fits. This necessitates energy-specific calibration for precise clinical dosimetry with these devices.

Practical Application in TBI Dosimetry

The nanophotonic scintillator demonstrated robust signal detectability across multiple anatomical locations on an anthropomorphic phantom in TBI setup conditions, with CNR values readily exceeding clinically relevant thresholds. Crucially, the light signal was reliably recorded using both professional CMOS and consumer phone cameras. In contrast, the conventional scintillator signal was undetectable under identical conditions.

Implications and Future Directions

Clinical Impact

The enhancements in signal yield and CNR enable real-time in-vivo TBI dosimetry using accessible camera systems, addressing longstanding limitations with passive detectors (TLD, OSLD) and active detectors (diodes, MOSFETs) in terms of workflow and reliability. The approach circumvents the requirement for expensive intensified cameras, potentially democratizing advanced dosimetric monitoring in radiotherapy clinics.

Broader Applications

Beyond TBI dosimetry, nanophotonic scintillators—with their superior light output—hold significant promise for improving X-ray imaging detector efficiency. Strong signal yield could enable either reduced patient dose or improved image quality in kV imaging panels and CT systems. Application to QA equipment and potential adaptation to small-field dosimetry (pending developments in tissue-equivalent plastic scintillator enhancement) further broaden the scope of impact.

Technical Considerations and Limitations

The present nanophotonic YAG:Ce scintillator is not tissue equivalent, introducing challenges for perturbation-free small-field dosimetry. Expanding nanophotonic patterning to polymeric plastics remains a technical challenge, with lower index contrast, material processing constraints, and optical transparency preservation needing resolution. Controlled random surface texturing for plastics emerges as a scalable alternative.

Research Outlook

Further research will focus on optimizing detector placement and camera configuration for clinical TBI, quantifying radiation damage effects, and characterizing angular and temperature dependencies. Reflective coatings and additional nanostructuring may yield further signal enhancements. Exploration of nanophotonic designs for X-ray imaging and QA panels, as well as integration with plastic scintillators, are anticipated future directions.

Conclusion

Nanophotonic structuring of scintillator surfaces yields substantial increases in light output and CNR, without compromising core dosimetric properties such as dose-rate independence and linearity. This technology enables real-time, in-vivo TBI dosimetry with consumer-grade cameras, promising significant improvements in radiotherapy workflow and patient safety. Further characterization and engineering refinements will facilitate expanded clinical deployment and adaptation to broader medical imaging and dosimetry domains.

(2606.16007)

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What is this paper about?

This paper is about making a common radiation-sensing material, called a scintillator, much brighter so it’s easier to read with simple cameras. The team tested a new “nanophotonic” surface coating—tiny patterns smaller than the wavelength of light—placed on top of a regular scintillator to see if it boosts brightness without messing up how accurately it measures radiation. They also tried it in a real-world style test for total body irradiation (TBI), a type of cancer treatment, to see if it could measure dose in real time using ordinary cameras.

What questions were they trying to answer?

In simple terms:

  • Can a special nano-patterned coating make a scintillator glow brighter when radiation hits it?
  • Does this brighter coating still measure radiation correctly (is it linear, stable with different dose rates, and consistent across beam types)?
  • Could this brighter scintillator let doctors check radiation dose during TBI treatments in real time, using affordable cameras instead of expensive equipment?

How did they do it?

Think of a scintillator like a glow tile: when radiation hits it, it gives off light. A brighter glow makes it easier to measure how much radiation is there.

  • The material: They used a common scintillator called YAG:Ce (yttrium aluminum garnet with cerium), about the size of a stick of gum but thinner.
  • The upgrade: Half of the scintillator was left normal, and the other half got a nanophotonic coating. Picture a super-fine, invisible grid etched onto the surface that helps more light escape, like anti-glare patterns on screens—only much smaller.
  • Side-by-side comparison: Because one piece had both surfaces (coated and uncoated), they could directly compare brightness and accuracy under the exact same radiation.
  • Measuring the light: They put the scintillator in a dark, 3D-printed box and filmed it from the side with a camera (so the camera wasn’t blasted by radiation).
  • Measuring the dose: They used special “radiochromic film” that darkens with radiation (like high-tech sunburn paper) to figure out exactly how much dose the scintillator received. They matched the film map to the camera images to connect “how bright” to “how much dose.”
  • TBI test: They placed the scintillator on a life-sized human-shaped model (a phantom) in a TBI treatment room and tried recording the glow with:
    • A standard lab camera in low, comfortable room lighting.
    • A regular smartphone camera with the room lights off.

Simple explanations of key terms:

  • Scintillator: A material that lights up when hit by radiation.
  • Nanophotonic coating: Tiny patterns that control and boost how light comes out of a surface.
  • Dosimetry: Measuring how much radiation dose something gets.
  • Dose rate: How fast the radiation dose is delivered (like how quickly a bucket fills with water).
  • Linearity: If you double the dose, does the light double too? That’s a good sign of accurate measurement.
  • Energy dependence: Whether the response changes a bit for different types/energies of radiation beams.
  • Contrast-to-noise ratio (CNR): How clearly the glow stands out from background fuzz in the image; higher is better.

What did they find?

Here are the main results:

  • Much brighter glow:
    • The nanophotonic-coated side gave about 4.1 times more light than the uncoated side.
    • Image quality improved too: CNR was about 3.7 times higher with the coated side at typical camera settings.
  • Good measurement behavior:
    • Dose rate independence: Changing how fast dose was delivered (within typical clinical ranges) didn’t affect the glow; variations were within ±0.5%. That’s excellent and means stable readings.
    • Linear response: The glow increased in a straight-line way with dose for all tested beams. In plain terms, more dose → proportionally more light, which is what you want for a reliable meter.
    • Modest energy dependence: The exact slope of “light vs. dose” changed a bit for different beam energies (both for photons and electrons). It’s small but noticeable, so the device should be calibrated for each beam energy to be most accurate.
  • Real-time TBI test success:
    • In a TBI setup (big distances and low dose rate make signals faint), the nanophotonic scintillator still produced a clearly detectable signal with a lab camera under dim room lighting at the head, chest, and diaphragm positions.
    • A consumer smartphone camera could also see the signal clearly (with room lights off).
    • The regular (uncoated) scintillator’s signal was too dim to detect in these TBI tests.

Why these results matter:

  • Brighter light means you can use simpler, cheaper cameras instead of bulky, expensive light detectors.
  • Good linearity and dose-rate independence mean the brightness boost doesn’t wreck the measurement accuracy.
  • Being able to see the signal during TBI with widely available cameras could let clinicians watch dose in real time and fix issues immediately, instead of waiting for after-the-fact readings.

Why is this important?

  • For patients: Real-time dose checks during complex treatments like TBI can improve safety and help ensure the right amount of radiation reaches the right places.
  • For clinics: Brighter scintillators could lower equipment costs and make advanced dose monitoring more accessible, even in smaller hospitals.
  • For imaging: In X-ray or CT scanners, a brighter scintillator might allow:
    • Lower X-ray dose to the patient for the same image quality, or
    • Better image quality at the same dose.

What’s next?

The researchers suggest:

  • Refining the setup for clinical TBI: optimize camera placement, test different positions on the body, and build easy-to-use calibration for different beam energies.
  • Checking durability and consistency: test temperature effects, angle sensitivity, and long-term radiation wear.
  • Exploring other uses: applying similar nanophotonic ideas to different scintillators, including plastics (useful for tiny radiation fields), and to medical X-ray detectors for better imaging.

The simple takeaway

By adding a tiny, carefully designed “light-boosting” pattern to a standard glow material, the team made it about four times brighter without losing accuracy. That extra brightness makes it possible to see radiation dose in real time with ordinary cameras—even in tough, low-light situations like TBI—opening the door to safer treatments and more affordable tools.

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Knowledge Gaps

Knowledge gaps, limitations, and open questions

The following items identify what remains missing, uncertain, or unexplored in the study and can guide targeted follow-up work:

  • Dosimetry scope: Absolute dose accuracy under true TBI conditions was not validated; no comparison against gold-standard in-vivo dosimetry (e.g., TLD/OSLD/diodes/MOSFET) across multiple anatomical sites, large SSD, spoiler use, and oblique incidence.
  • Dose-rate range: Dose-rate independence was only tested from 400–2,000 MU/min; behavior at very low effective dose rates typical for extended-SSD TBI and at ultrahigh-dose-rate (FLASH) regimes remains unmeasured, including detector/camera dynamic range and potential saturation.
  • Angular dependence: No measurement of angular response; need a 2D angular sensitivity map (incidence and azimuth) to support oblique fields and variable patient geometry.
  • Field-size and scatter dependence: Response vs field size, distance to field edge, and scatter conditions (e.g., with/without spoiler, different room scatter) was not characterized.
  • Temporal response: Scintillator rise/decay times, afterglow, and potential signal carryover between pulses were not measured; implications for real-time dosimetry and temporal deconvolution are unknown.
  • Radiation damage and aging: Long-term stability of the nanophotonic coating under cumulative clinical doses was not assessed (e.g., light-yield drift, spectral shifts, surface oxidation, photodarkening).
  • Environmental sensitivity: Temperature and humidity dependence of light yield (including at skin temperature) were not quantified; robustness to condensation/sweat and cleaning fluids is unknown.
  • Mechanical durability and sterility: Effects of handling, repeated cleaning/sterilization, abrasion, and bending on nanostructure integrity and performance were not evaluated.
  • Tissue perturbation: The non–tissue-equivalent YAG:Ce layer’s impact on surface dose and electron fluence was not quantified (especially for small fields and TBI near build-up); no Monte Carlo or film-in-phantom validation of perturbation.
  • Plastic scintillator pathway: Feasibility, manufacturability, and expected light-yield gains of applying the nanophotonic approach to tissue-equivalent plastic scintillators were not experimentally explored.
  • Spectral/directional emission: The nanophotonic layer’s impact on emission spectrum, polarization, and angular distribution was not measured; camera spectral matching and filter design remain uninformed.
  • Camera dependence: Performance was demonstrated with one CMOS and one smartphone; generalizability to diverse camera sensors/lenses, control of auto-exposure/white balance, radiation-induced sensor damage, and lifetime were not assessed.
  • Ambient light robustness: Minimum detectable dose rate vs ambient illuminance was not mapped; benefits of narrowband optical filters and shielding against room light were not tested.
  • Image-processing robustness: Background subtraction relied on pre-beam frames; resilience to patient motion, changing illumination, and real-time operation (latency, failure modes) was not validated; no end-to-end uncertainty budget for the optical pipeline.
  • Stray-light contamination: Potential contributions from Cherenkov/radioluminescence in the housing/tape/spoiler/skin were not isolated (e.g., via spectral separation or control materials).
  • Calibration methodology: The film-on-scintillator-in-air approach introduces geometry/material biases (notably for photons); no Monte Carlo–based correction or water-equivalent calibration was performed to resolve electron vs photon discrepancies.
  • Uniformity: Spatial uniformity of light enhancement across the patterned area and between devices/batches was not quantified; no mapping of intra-device nonuniformity or batch-to-batch variability.
  • Half-patterned test geometry: Potential lateral light transport and cross-talk between patterned and unpatterned halves were not analyzed; comparisons using separate, fully patterned/unpatterned devices would remove confounds.
  • Thickness/backing optimization: The impact of scintillator thickness and the addition of reflective backing on signal, CNR, and perturbation was not systematically evaluated.
  • Viewing geometry: Dependence of measured signal on detector orientation and camera off-axis/viewing angle was not mapped; an optimized camera placement protocol is lacking.
  • Scalability and multiplexing: Feasibility of multi-point arrays (ID discrimination, cross-talk, readout bandwidth) and minimal useful detector size for clinical deployment were not studied.
  • Clinical workflow: No human in-vivo pilot demonstrating accuracy, action thresholds, and workflow integration (setup, positioning, documentation) compared to current standard-of-care dosimeters.
  • Regulatory and safety: Biocompatibility of coatings/adhesives, skin-contact safety, and sterilization protocols were not addressed; electrical/safety considerations for camera use in TBI rooms are unspecified.
  • MR compatibility: Performance and safety in magnetic fields (MR-Linac environments) were not assessed (materials, forces, image artifacts).
  • Comprehensive uncertainties: A full error budget (dosimetric, optical, geometric, camera noise, calibration drift) and day-to-day reproducibility were not reported.
  • Imaging use-cases: For X-ray detector applications, system-level metrics (MTF, DQE, NPS), dose-reduction potential, and artifact behavior were not measured; no integration study with existing panels.
  • Modality/energy generalization: Response for kV beams, proton/ion therapy, and specialized clinical beam modifiers (wedges, bolus, compensators) remains untested.
  • Patient-interface optics: Effects of air gaps, skin curvature, hair/clothing, and dressings on optical coupling and signal stability were not characterized.
  • Camera radiation shielding: The efficacy and optimization of camera shielding, radiation-induced noise quantification, and long-term drift under TBI conditions were not evaluated.
  • Data and reproducibility: Raw data, calibration curves, and analysis code are not publicly available, limiting independent verification and meta-analysis.
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Practical Applications

Immediate Applications

The following applications can be piloted or deployed now using the paper’s demonstrated performance (4.1× light output, 3.7× CNR improvement, linear dose response, dose-rate independence, modest energy dependence) and accessible hardware (CMOS/smartphone cameras).

  • Real-time in-vivo surface dosimetry for total body irradiation (TBI)
    • Sectors: Healthcare (radiation oncology)
    • Tools/workflows: Nanophotonic YAG:Ce adhesive patches at head/chest/diaphragm; tripod-mounted CMOS or shielded smartphone cameras placed outside the field; simple analysis pipeline for background subtraction and time-integration; energy-specific calibration curves; dim-to-comfortable lighting
    • Assumptions/dependencies: Energy dependence requires per-energy calibration; thin detector does not perturb TBI beams; camera spectral sensitivity around 550 nm; camera shielding to suppress radiation-induced noise; clinical validation and QA procedures; institutional approvals
  • Lower-cost replacement for intensified cameras in surface imaging during TBI/TSET and beam visualization
    • Sectors: Healthcare (clinical physics QA and setup verification)
    • Tools/workflows: Nanophotonic-coated scintillator screens coupled to commodity CMOS cameras for non-contact beam visualization and workflow checks; 3D-printed light baffles; exposure/CNR presets (≈200–500 ms exposures)
    • Assumptions/dependencies: Adequate ambient light control; per-energy calibration; radiation hardness of cameras and coatings; verification against existing systems
  • Brachytherapy QA radioluminescence imaging with reduced hardware burden
    • Sectors: Healthcare (brachytherapy QA)
    • Tools/workflows: Nanophotonic scintillator screens to visualize source positions/strengths using non-intensified cameras; existing image analysis algorithms for source localization
    • Assumptions/dependencies: Calibration at relevant (often lower) photon energies; durability under clinical use; evaluation of angular/temperature effects; regulatory change control for QA devices
  • Daily linac QA and isocenter verification with brighter scintillator screens
    • Sectors: Healthcare (linac QA)
    • Tools/workflows: Retrofitting QA phantoms that currently rely on scintillation with nanophotonic-coated elements to shorten exposures and reduce camera costs; automated pass/fail dashboards
    • Assumptions/dependencies: Stability of coatings under routine use; per-energy calibration stored in device; reproducibility of CNR improvements across machines
  • Educational demonstrations/lab exercises using phone-readable scintillation
    • Sectors: Education (medical physics, radiation science), Public outreach
    • Tools/workflows: Small nanophotonic scintillator tiles viewable with smartphones for demonstrating radiation-to-light conversion; simple safety-minded setups using clinical QA beams or controlled sources
    • Assumptions/dependencies: Compliance with radiation safety; control of ambient light; robust mechanical protection (caps/covers)
  • R&D methodology for characterizing scintillator modifications
    • Sectors: Academia, Industry R&D
    • Tools/workflows: Half-patterned scintillator samples for internal control; radiochromic film-to-camera co-registration; CNR/dose linearity/dose-rate test scripts; MATLAB/Python pipelines
    • Assumptions/dependencies: Access to calibrated beams and film dosimetry; reproducible sample fabrication; standard uncertainty analysis
  • Incremental light-yield gains via reflective back-coatings in current prototypes
    • Sectors: Healthcare (dosimetry prototypes), Industry (detector suppliers)
    • Tools/workflows: Apply thin mirror or dielectric stack to the rear of the scintillator to further boost extraction; re-verify calibration
    • Assumptions/dependencies: No adverse angular response or spectral shift; adhesive/thermal compatibility; minimal added thickness

Long-Term Applications

These applications require further research, scaling, integration, or validation (e.g., large-area manufacturing, regulatory clearance, extended characterization: angular/temperature dependence, long-term stability, radiation damage).

  • Commercial real-time in-vivo TBI dosimetry system
    • Sectors: Healthcare (radiation oncology)
    • Tools/products/workflows: Wearable scintillator patches with fiducials; wall/ceiling-mounted camera arrays; real-time dose reconstruction and alarms; EMR integration; automated energy/angle compensation
    • Assumptions/dependencies: Multicenter clinical validation; robustness to patient movement, skin curvature, and lighting; cybersecurity and IEC/ISO compliance; sterilization and biocompatibility; hospital IT integration
  • Nanophotonic-enhanced kV X-ray detector panels for CT and radiography
    • Sectors: Medical imaging; Industrial NDT
    • Tools/products/workflows: Nanophotonic coatings on scintillator plates (e.g., CsI:Tl, YAG:Ce) to improve DQE; options to trade 4× light for lower patient dose or higher image quality; panel-level process control and metrology; redesign of optical coupling
    • Assumptions/dependencies: Uniform, wafer-scale/maskless patterning with consistent MTF; mechanical and radiation durability; afterglow and temporal response characterization; regulatory approval (510(k)/CE); cost-benefit at panel scale
  • Enhanced EPIDs for MV portal imaging and dosimetry
    • Sectors: Radiation oncology (IGRT, QA)
    • Tools/products/workflows: Retrofitted or next-gen EPID scintillator layers with nanophotonic texturing to raise SNR and spatial resolution; improved portal dosimetry and QA workflows
    • Assumptions/dependencies: Compatibility with EPID optics, vacuum/thermal environment; radiation hardness; pixel cross-talk; factory calibration and long-term stability
  • Plastic nanophotonic scintillators for small-field dosimetry
    • Sectors: Healthcare (stereotactic radiosurgery, MR-Linac), Industry (detector vendors)
    • Tools/products/workflows: Periodic or controlled-random subwavelength surface textures or high-index patterned coatings on plastic scintillators to improve light extraction while preserving tissue equivalence and small volume
    • Assumptions/dependencies: Feasible nanoimprint/roughness processes on plastics (low Tg), preserved optical clarity, sufficient index contrast (n≈1.5–1.6), long-term surface stability, calibration vs. field size/angle
  • Dosimetry for ultrahigh dose-rate (FLASH) radiotherapy
    • Sectors: Healthcare (emerging therapies)
    • Tools/products/workflows: Nanophotonic scintillator screens coupled to CMOS/SiPMs enabling microsecond-resolved 2D profiles without expensive intensified systems
    • Assumptions/dependencies: Validation at >40 Gy/s; management of detector saturation and phosphorescence; radiation damage robustness; synchronization to beam pulses
  • MR-Linac compatible surface dosimetry patches
    • Sectors: Healthcare (MR-guided radiotherapy)
    • Tools/products/workflows: Non-magnetic nanophotonic scintillator patches read by fiber optics or remote cameras to provide real-time skin dose in magnetic fields
    • Assumptions/dependencies: Verified MR safety (B0/RF heating/artifacts), optical behavior and alignment in high fields, MR-room workflow integration
  • Low-dose environmental/industrial radiation monitoring with camera-readable panels
    • Sectors: Energy (nuclear facilities), Industrial safety, NDT
    • Tools/products/workflows: Fixed scintillator panels observed by shielded cameras to detect leaks/beam misalignment; cloud dashboards and alerts
    • Assumptions/dependencies: Sensitivity and stability at very low dose rates; ambient light suppression; weathering/contamination resistance; periodic calibration and false-alarm control
  • Smartphone-based dose readout software for clinics
    • Sectors: Software, Healthcare QA
    • Tools/products/workflows: Cross-device app for background subtraction, CNR monitoring, per-energy dose conversion, and QA logging; device-specific spectral calibration and color correction; secure data export
    • Assumptions/dependencies: Inter-model variability in camera sensors; HIPAA/privacy compliance; IT policies for mobile devices; user training and human factors
  • Policy and standards updates endorsing real-time in-vivo TBI dosimetry
    • Sectors: Policy/Professional societies (AAPM, ESTRO)
    • Tools/products/workflows: Task group recommendations after multicenter studies; procurement guidelines emphasizing lower-cost, real-time solutions; training curricula
    • Assumptions/dependencies: Evidence base demonstrating accuracy, reliability, and patient benefit; cost-effectiveness analyses; interoperability and safety guidelines
  • Supply-chain/manufacturing scale-up for nanophotonic scintillator coatings
    • Sectors: Materials and device manufacturing
    • Tools/products/workflows: Industrial nanoimprint lithography, roll-to-roll or wafer-scale processes, in-line optical metrology, protective capping layers; QA specs for pattern uniformity and adhesion
    • Assumptions/dependencies: Yield and cost at panel sizes; abrasion and chemical resistance; compatibility with existing detector assembly lines; IP/licensing and standardization

Assumptions common across many applications: modest energy dependence necessitates per-energy calibration; angular and temperature dependencies plus radiation damage must be characterized for clinical-grade use; camera placement and shielding are critical to suppress radiation-induced noise; non–tissue-equivalent YAG:Ce is acceptable for TBI and QA but not ideal for small-field dosimetry (driving plastic-based developments).

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Glossary

  • AAPM TG-29: An American Association of Physicists in Medicine task group report providing guidance on total and half body irradiation procedures and verification. "AAPM TG-29 specifies that in-vivo dosimetry should be performed to verify that the prescription matches what was delivered"
  • Absolute dosimetry: The process of determining the actual absorbed dose using calibrated detectors. "Absolute dosimetry was done with dose-calibrated radiochromic film."
  • Annealing: A thermal process used to modify material structure, often to reorganize thin films or relieve stress. "Finally, annealing above the glass transition temperature drove the film to reorganize into a highly ordered array of nanospheroids."
  • Anthropomorphic phantom: A human-shaped model used to simulate patient anatomy for imaging or dosimetry tests. "An anthropomorphic phantom was placed in our clinic's TBI booth"
  • Brachytherapy: A radiation therapy technique where sealed radioactive sources are placed inside or next to the treatment area. "Some innovative QA devices use scintillators for daily linac QA and isocenter verification [3] and brachytherapy [4], illustrating the increased use of scintillators for QA applications."
  • Buildup material: Overlying material that establishes charged particle equilibrium and builds up dose to a maximum. "in a megavoltage photon beam, dose is deposited by secondary electrons liberated through photon interactions, and at a point in air without overlying buildup material the local secondary electron fluence is small and strongly dependent on the detector itself."
  • Cerium-doped yttrium aluminum garnet (YAG:Ce): An inorganic scintillator material with emission in the green spectrum used for radiation detection. "we performed the first dosimetric characterization of a cerium-doped yttrium aluminum garnet (YAG:Ce) nanophotonic scintillator."
  • Chalcogenide glass: A family of high-index, infrared-transmitting glasses used in photonics and thin-film coatings. "A thin chalcogenide glass film was subsequently deposited by thermal evaporation."
  • Coefficient of determination (R2): A statistical measure indicating how well data fit a regression model. "The coefficient of determination, R2, and the root mean square error, RMSE, were calculated for each fit."
  • Collimator: A device in a linear accelerator that shapes and directs the radiation beam. "The gantry and collimator were set to 0° and varying energies were delivered..."
  • Contrast-to-noise ratio (CNR): A measure of how distinguishable a signal is from background noise in an image. "The nanophotonic YAG:Ce exhibited a 3.7 time increase in CNR compared to the conventional YAG:Ce scintillator."
  • Electronic portal imaging devices (EPID): Flat-panel detectors on linacs for imaging and dosimetric verification of radiation beams. "They are also commonly used in electronic portal imaging devices (EPID) found on C-arm linear accelerators (linacs)..."
  • Effective atomic number: A weighted average atomic number representing a compound’s interaction with radiation. "The 0.5 mm YAG:Ce layer, by contrast, has a much higher effective atomic number and density, producing substantially more secondary electrons..."
  • Effective variance method: An approach to estimate parameter uncertainties in regression when both variables have errors. "Fitting was performed for each energy using orthogonal distance regression to account for uncertainties in both the dose and signal measurements, with the slope uncertainty estimated using the effective variance method."
  • F-test: A statistical test comparing variances or model fits to assess significance between models. "Energy dependence was assessed using an F-test comparing a single common slope fitted to all energies simultaneously against separately fitted slopes for each energy."
  • Fiducial markers: Reference points used to align and register images or datasets accurately. "Using the edges of the films as fiducial markers, a rigid registration was used to map the film measured dose to the CMOS camera time series images"
  • Flattening filter free (FFF): A mode of linac operation without the flattening filter, allowing very high dose rates. "250 MU 10 MV flattening filter free (FFF) photons were delivered to the nanophotonic YAG:Ce scintillator..."
  • FLASH radiotherapy: Ultra-high dose rate irradiation (typically >40 Gy/s) that can reduce normal tissue toxicity. "scintillators have emerged as a premier candidate for ultra-high dose rate (FLASH) radiotherapy"
  • Gantry: The rotating part of a linac that positions the treatment beam around the patient. "The gantry and collimator were set to 0°"
  • Gafchromic EBT-XD: A specific type of self-developing radiochromic film used for high-dose dosimetry. "radiochromic film (Gafchromic EBT-XD, Ashland, Bridgewater NJ, USA) was first calibrated according to established protocols [35]."
  • Glass transition temperature: The temperature where an amorphous material transitions from rigid to rubbery, enabling structural reorganization. "Finally, annealing above the glass transition temperature drove the film to reorganize into a highly ordered array of nanospheroids."
  • High-index coating: A thin film with a high refractive index used to manipulate light propagation at surfaces. "either by imprinting a nanoscale texture directly into the polymer surface or by depositing a patterned high- index coating on top of the plastic substrate."
  • Index contrast: The difference in refractive indices between materials that governs optical confinement and scattering. "reducing the available index contrast for photonic structuring."
  • Interference lithography: A patterning technique using interference of light beams to define periodic nanoscale structures over large areas. "These subwavelength structures were fabricated using an interference-lithography-defined master mold which enables patterning over centimeter- scale areas."
  • Ion recombination: The process where ion pairs recombine in detectors, reducing measured signal, especially at high dose rates. "they circumvent the significant ion recombination challenges inherent to gas-filled detectors"
  • Isocenter: The point in space where the radiation beam axes converge and around which the gantry rotates. "Some innovative QA devices use scintillators for daily linac QA and isocenter verification"
  • Linear accelerator (linac): A machine that accelerates electrons to generate therapeutic X-rays or electron beams for radiotherapy. "They are also commonly used in electronic portal imaging devices (EPID) found on C-arm linear accelerators (linacs)..."
  • Local density of optical states (LDOS): A measure of how many electromagnetic modes are available at a point and frequency, influencing emission rates. "Nanophotonics exploits geometry to engineer the local density of optical states"
  • Metasurface photonics: The study and use of ultrathin, subwavelength-structured surfaces to control light’s phase, amplitude, and polarization. "Recent advances in metasurface photonics and manufacturing have enabled a nanophotonic surface coating to be applied to conventional scintillators"
  • Monitor unit (MU): A linac output unit proportional to delivered dose under specified calibration conditions. "The linac was calibrated such that 1 monitor unit (MU) was equal to 1 cGy at the depth of maximal dose in water"
  • MR-Linac: A hybrid medical device combining an MRI scanner and a linear accelerator for image-guided radiotherapy. "in high-field MR-Linac environments"
  • Nanoimprint lithography: A replication technique that presses a patterned stamp into a polymer to transfer nanoscale features. "The master texture was first transferred onto the scintillator by nanoimprint lithography: a polymer stamp replicated from the silicon master was pressed into a UV-curable polymer layer"
  • Nanophotonics: The field that manipulates light using structures at the nanometer scale to control optical properties and emission. "Nanophotonics is a field of research that provides strategies to shape light by structuring matter on the scale of the optical wavelength or below"
  • Optically stimulated luminescent dosimeters (OSLDs): Passive dosimeters that store radiation energy and release light upon optical stimulation for dose readout. "Thermoluminescent dosimeters (TLDs) and optically stimulated luminescent dosimeters (OSLDs) are the most common; however, both are passive 'offline' detectors..."
  • Orthogonal distance regression: A fitting method that accounts for errors in both independent and dependent variables. "Fitting was performed for each energy using orthogonal distance regression to account for uncertainties in both the dose and signal measurements"
  • Partial buildup: The condition where some, but not full, charged particle equilibrium is established, increasing local dose deposition. "thereby self-establishing a partial buildup that enhances energy deposition relative to the film."
  • Photodiode: A semiconductor device that converts light into an electrical signal, commonly used in X-ray detector panels. "which is then detected by a CMOS photodiode [2]."
  • Photonic crystal: A periodic optical nanostructure that affects photon propagation, enabling control of emission and light extraction. "The resulting photonic crystal had a subwavelength period of 450 nm."
  • Photon fluence: The number of photons passing through a unit area, often used to discuss imaging dose levels. "enable lower photon fluences to generate equivalent image quality, reducing patient dose."
  • Photonic structuring: The design of micro/nanostructures to tailor optical behavior such as emission, scattering, or guiding. "reducing the available index contrast for photonic structuring."
  • Plexiglass electron spoiler: A scattering plate placed in the beam path during TBI to increase surface dose from photon beams. "A 1 cm plexiglass electron spoiler was used as is standard in our clinic."
  • Quality assurance (QA): Procedures and measurements ensuring that radiotherapy and imaging equipment deliver accurate and safe performance. "Scintillating materials, which emit light upon excitation by high-energy radiation, are integral to radiotherapy dosimetry, quality assurance (QA), and medical imaging"
  • Radiochromic film: A self-developing film that darkens in proportion to absorbed radiation dose, used for dosimetry. "For absolute dose measurements, radiochromic film (Gafchromic EBT-XD, Ashland, Bridgewater NJ, USA) was first calibrated"
  • Random surface texturing: A scalable approach that introduces controlled roughness to enhance light extraction without periodic patterns. "a recent alternative is to use controlled random surface texturing rather than periodic nanophotonic patterning"
  • Region of interest (ROI): A selected area in an image used for focused analysis of signal and noise. "A region of interest (ROI) was manually applied to cover the conventional and nanophotonic scintillator portions"
  • Rigid registration: An image alignment method allowing only rotations and translations to map one dataset onto another. "Using the edges of the films as fiducial markers, a rigid registration was used to map the film measured dose to the CMOS camera time series images"
  • Root mean square error (RMSE): A measure of the average magnitude of regression residuals, indicating model fit quality. "The coefficient of determination, R2, and the root mean square error, RMSE, were calculated for each fit."
  • Scanning electron micrograph: An image produced by a scanning electron microscope, showing surface nanostructure details. "C, scanning electron micrograph view of nanophotonic surface showing sub-wavelength size structures."
  • Secondary electron fluence: The flow of electrons generated by primary photon interactions, responsible for dose deposition in photon beams. "the local secondary electron fluence is small and strongly dependent on the detector itself."
  • Silica cladding: A protective or optical cladding layer of SiO2 used to encapsulate and protect photonic structures. "The surface coating consists of a polymer coating with embedded chalcogenide glass and silica cladding (Fig. 1BC)."
  • SiO2 capping layer: A thin protective silica layer deposited on nanostructures to prevent oxidation or damage. "A thin SiO2 capping layer was added to protect the chalcogenide nanostructures from further oxidation."
  • Source to surface distance (SSD): The distance from the radiation source to the surface of the target/patient, defining geometry and dose rate. "The scintillator was positioned at 100 cm source to surface distance"
  • Thermoluminescent dosimeters (TLDs): Passive detectors that store energy from radiation and emit light when heated for dose readout. "Thermoluminescent dosimeters (TLDs) and optically stimulated luminescent dosimeters (OSLDs) are the most common"
  • Tissue equivalent: Describes materials whose radiation interaction properties mimic human tissue, minimizing dosimetric perturbations. "One potential drawback of the current nanophotonic scintillator is that it is not tissue equivalent."
  • Total body irradiation (TBI): A radiotherapy technique delivering dose to the entire body, often as part of transplant conditioning. "We also tested a potential first application of the scintillator in the clinic for total body irradiation (TBI) in-vivo dosimetry."
  • Water-equivalent: Materials having radiation attenuation and scattering characteristics similar to water, used as dosimetric references. "The radiochromic film is thin and approximately water-equivalent, so it generates few secondary electrons internally"
  • YAG:Ce (yttrium aluminum garnet, cerium-doped): A scintillator with peak emission around 550 nm used in imaging and dosimetry. "YAG:Ce is a commonly used inorganic scintillating material with maximum emission at 550 nm [34]."
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