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REVIEW 3 major objections 6 minor 26 references

Spectacular - A Modular DAQ System for Microdosimetry

T0 review · 3 major / 6 minor · reviewed 2026-08-05 · deepseek-v4-flash

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Pith's one-line read A modular data-acquisition system with roughly 175-electron noise records proton and carbon-ion microdosimetric spectra at full clinical dose rates, covering the full carbon lineal-energy range.

desk verdict A genuinely useful modular DAQ platform, but the clinical-dose-rate pileup claim is unsupported without rate and PUR characterization. read the letter →

arxiv 2608.03208 v1 pith:4BAKUXOI submitted 2026-08-04 physics.ins-det physics.med-ph

Matthias Knopf , Simon Waid , Daniel Radmanovac , Sebastian Onder , Richard Thalmeier , Peter Fischer , Stefan Gundacker , Claudio Verona
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Edoardo Domenicone Thomas Bergauer Albert Hirtl
This is my paper · ORCID
classification physics.ins-detphysics.med-ph
keywords microdosimetrylinearenergytransferparticletherapydataacquisitionsystempulsepileuprejectiondiamondmicrodosimetercharge-sensitiveamplifierdigitalshaping
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper argues that a single modular data-acquisition platform can meet both conflicting demands of clinical microdosimetry: resolving the small energy deposits (of order $10^3$ electrons) from $\mu$m-scale detectors while rejecting pileup at therapeutic ion-beam rates near $10^{10}\,\mathrm{s^{-1}}$. The authors built "Spectacular", centered on a Zynq UltraScale+ system-on-chip, a 16-bit $100\,\mathrm{MSa\,s^{-1}}$ ADC, and interchangeable front-end daughterboards, and tested it at a clinical ion-therapy center with a custom discrete charge-sensitive amplifier (equivalent noise charge of $\sim 175\,e$ at the optimal $1\,\mu\mathrm{s}$ shaping time) and a $10\,\mu\mathrm{m}$ diamond microdosimeter. With fast-slow pileup rejection (a $50\,\mathrm{ns}$ fast shaper inhibiting acquisition up to fourth order), the system recorded lineal-energy spectra for $62.4\,\mathrm{MeV}$ protons and $120\,\mathrm{MeV/u}$ carbon ions along the depth-dose curve at full clinical dose rates; for carbon the whole dynamic range was covered, while for protons a lower cutoff of $3.5\,\mathrm{keV}\,\mu\mathrm{m^{-1}}$ was required because entrance-channel low-LET events were not yet resolvable. If the claim holds, microdosimetry moves from research prototypes toward routine clinical use as an experimental source of radiation-quality data for treatment planning and quality assurance in particle therapy; the authors state that a dedicated CSA ASIC and revised boards are expected to uncover the currently inaccessible proton range.

What carries the argument

The carrying mechanism is one reconfigurable pipeline: a daughterboard-mounted charge-sensitive amplifier feeds a 16-bit, $100\,\mathrm{MSa\,s^{-1}}$ ADC, and the FPGA shapes the digitized trace with a finite-impulse-response kernel implementing a fourth-order quasi-Gaussian filter. Two time constants do the work: a $1\,\mu\mathrm{s}$ slow shaper extracts amplitudes with maximum signal-to-noise ratio, while a $50\,\mathrm{ns}$ fast shaper flags closely spaced events and vetoes acquisition up to fourth order (the fast-slow pileup-rejection method). The FPGA resets the CSA on threshold crossings, synchronizes to the accelerator extraction trigger, and delta-compresses the $200\,\mathrm{MB\,s^{

What would settle it

Acquire the same lineal-energy spectrum twice at the same beam position: once at full clinical dose rate and once with the beam attenuated until pileup is negligible. If the two $y\,d(y)$ distributions differ — a rate-dependent shift in the carbon or proton edge, or a suppression of high- or low-LET events — the pileup rejection is not complete. An equivalent test is to histogram the inter-event times from the $50\,\mathrm{ns}$ fast channel and compare against the expectation from the measured micro-spill structure; a mismatch would show that fourth-order inhibition is insufficient.

Watch

Extended reading notes

Core claim

On its own terms, the paper claims that the Spectacular platform — a Zynq UltraScale+ SoC, 16-bit ADC at $100\,\mathrm{MSa\,s^{-1}}$, and a standardized daughterboard interface — turns microdosimetry readout into a reconfigurable chain: swap the front end, keep the digitization, shaping, and pileup rejection. A discrete CSA reached ENC $\sim 175\,e$ at $1\,\mu\mathrm{s}$ shaping. With a fourth-order quasi-Gaussian digital shaper and a $50\,\mathrm{ns}$ fast channel vetoing up to fourth order, it recorded spectra for $62.4\,\mathrm{MeV}$ protons and $120\,\mathrm{MeV/u}$ carbon ions at full clinical dose rate, calibrated by the proton edge. Carbon covered the full dynamic range; protons requi

Load-bearing premise

The fast-slow pileup rejection (a $50\,\mathrm{ns}$ fast shaper vetoing up to fourth order) is assumed to keep spectra free of pileup distortion at full clinical dose rates, but the paper reports no measured event rate, pileup fraction, or comparison against a pileup-free reference.

Editorial extensions

If this is right

  • If the platform performs as claimed, the same carrier board evaluates different charge-sensitive front ends, ASICs, and detectors without redesigning the digitization and processing chain, accelerating sensor development for microdosimetry.
  • Carbon-ion beams can be characterized across the entire lineal-energy dynamic range at clinical dose rates, supplying experimental radiation-quality data for treatment-planning and quality-assurance workflows.
  • Once the noise target below $100\,e$ is reached with the dedicated CSA ASIC and revised boards, the proton entrance-channel range below $3.5\,\mathrm{keV}\,\mu\mathrm{m^{-1}}$ becomes accessible, closing the remaining gap.
  • Synchronizing acquisition with the extraction trigger and exploiting the micro-spill time structure of synchrotron beams offers an additional lever against pileup on top of the fast-slow veto.
  • Multi-channel simultaneous readout, currently limited to one digitized channel in this prototype, is the natural next step enabled by the four-channel carrier design and FPGA-side processing.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • The paper reports no per-spill event rates or pileup fractions, so the "full clinical dose rate" claim stands or falls with the fast-slow rejection assumption; a rate sweep or a comparison against a pileup-free reference spectrum would settle it directly. (This is my inference, not the paper's claim.)
  • The digitize-early, shape-digitally pipeline is parameterized only by filter time constants, so the same architecture transfers to other high-rate single-event spectroscopy problems, such as LET spectrometry in mixed radiation fields or neutron/gamma discrimination.
  • Because synchrotron beams arrive in a micro-spill structure correlated with the machine orbital frequency, gating on the spill phase could reject a class of pileup events that a free-running $50\,\mathrm{ns}$ veto misses; the paper's extraction-trigger synchronization option is the natural first step toward testing that.
  • The multiplexed single-ADC prototype leaves the four-channel claim untested under simultaneous load; a four-channel acquisition would reveal whether the shared digitizer introduces dead time or cross-talk that single-channel results cannot show.
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Signed reviews

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 6 minor

Summary. This manuscript describes Spectacular, a modular DAQ platform for solid-state microdosimetry. The system is based on a Xilinx Zynq UltraScale+ SoC, a 16-bit 100 MS/s ADC, interchangeable front-end daughterboards, and FPGA/CPU/host processing. The authors report a discrete CSA with ~175 e ENC at 1 µs shaping time, verified linearity up to 250 fC, and a fast-slow pileup rejection scheme using a 50 ns fast shaper, a 1 µs slow shaper, and inhibition up to fourth order. Beam tests at MedAustron with a 10 µm diamond microdosimeter produced microdosimetric spectra for 62.4 MeV protons and 120 MeV/u carbon ions at several depths, calibrated with the proton edge and compared qualitatively with GATE simulations. The central claims are that the platform can acquire spectra under full clinical dose-rate conditions, that the full dynamic range for carbon ions is covered, and that pulse pileup is mitigated by the implemented PUR scheme.

Significance. If the rate capability and spectral fidelity claims are substantiated, this would be a useful contribution to clinical microdosimetry instrumentation. The paper has clear strengths: the ENC was measured with the sensor attached in the irradiation room, the spectra are calibrated against the external proton-edge standard, the comparison to independent GATE simulations provides a reference for the measured shapes, and the hardware architecture is documented in enough detail to be reproduced. The authors also explicitly disclose the proton low-energy cutoff, which is a welcome limitation statement. However, the central claim of acquiring undistorted spectra under full clinical dose-rate conditions is not yet supported because no quantitative rate or pileup information is provided. This is an addressable gap, not an internal inconsistency, and should be fixed before publication.

major comments (3)
  1. [§3 Processing; §4 Characterization] The central claim that spectra were acquired under full clinical dose-rate conditions rests on the fast-slow PUR scheme, but no event rate, pileup fraction, or pileup-free reference is reported. The scheme is specified only as a 50 ns fast shaper and inhibition 'up to the fourth order'; the fast-channel resolving time, inhibition window, dead time, and inhibited fraction are missing. Events closer than the fast-channel resolving time, and fifth-and-higher-order coincidences, are unaddressed, and the inhibition dead time itself can bias the accepted-event distribution. Since residual pileup adds artificial high-y events, the reported yd(y) spectra could be distorted. Please report rates per depth, quantify PUR efficiency/dead time, and validate one spectrum against a reduced-rate or pileup-free acquisition. The cited micro-spill structure [22,23] does not replace measured spill-synchroniz
  2. [§4, Figure 4] Figure 4 shows no error bars or uncertainties, and the agreement with GATE is only qualitative. Because the conclusions depend on spectral shapes and dynamic-range coverage, please add statistical and calibration uncertainties and a quantitative comparison (e.g., y_F, y_D, or bin-wise residuals) for representative depths. Also specify the GATE physics list, detector geometry, and energy-deposition model used; citing [13] is insufficient.
  3. [§4, proton spectra] The proton spectra are subject to a lower cutoff of 3.5 keV/µm, so shallow-depth spectra are not fully resolved and the dose-weighted yd(y) is truncated. This materially qualifies the claimed clinical-rate acquisition for protons. Please quantify the fraction of events and dose below the cutoff from the GATE simulation, show its impact on y_F and y_D, and state this limitation explicitly in the abstract and conclusions.
minor comments (6)
  1. [Abstract; §3] Typographical errors: 'By enabling optimization fast testing' in the abstract; 'Spectacularisbasedaroud' and 'daugtherboards' in §3. Please proofread throughout.
  2. [§2–§4] Terminology is inconsistent: 'pile-up' and 'pileup' are both used, and the simulation code is sometimes 'Gate' and sometimes 'GATE'. Please standardize.
  3. [References] References [1]–[3] and [22]–[24] lack complete bibliographic information (journal, volume, pages, or DOI). Please complete the entries.
  4. [§3 Processing] The phrase 'up to the fourth order' is ambiguous: does it mean fourth-order coincidences or inhibition of up to four subsequent pulses? Please define the order and the corresponding time window.
  5. [§4 Characterization] No nominal clinical dose rates or particle fluences are stated for the beam tests. Please report the dose rate and, if available, the count rate observed by the detector at each depth.
  6. [Figure 1] Caption contains a missing space ('10µmdiamond') and the legend labels may be hard to distinguish for color-blind readers. Consider markers or distinct line styles.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the DAQ characterization is self-contained and benchmarked against independent external references.

full rationale

The paper's central results are direct measurements calibrated against independent references, not circular reductions. The ENC of ~175 e is obtained from the FWHM of baseline fluctuations at 1 µs shaping time, an internal measurement. Linearity is verified by injecting calibrated charge pulses through a 0.1 pF test capacitor up to the estimated carbon-edge charge, an external electrical reference. The microdosimetric spectra are calibrated using the proton edge, a standard spectral feature from the literature, and then compared with GATE Monte Carlo simulations, which are independent of the measured data. No fitted parameter is later renamed as a prediction, and no quantity is defined in terms of the result it is used to produce. The self-citations ([16] for the diamond detector, [22,23] for spill-structure characterization, [24] for a future ASIC) are contextual: the fast-slow pileup-rejection scheme described in Section 3 is implemented on the basis of the standard fast-slow coincidence method, and the cited spill-structure work is presented only as a possible future avenue, not as the mechanism used for the reported acquisitions. The absence of reported event rates and pileup fractions weakens the support for the 'full clinical dose-rate conditions' claim, but that is an evidentiary gap rather than a circularity: the claim does not reduce by construction to the unstated rates. No circular step can be exhibited from the paper's own equations or citations.

Assumptions & free parameters 3 free parameters · 4 assumptions · 0 invented entities

The central claim rests on the calibration and simulation being reliable, and on the assertion that the pileup rejection works at clinical rates without direct verification. No new physical entities are introduced.

free parameters (3)
  • Proton lower cutoff applied to spectra = 3.5 keV/µm
    Applied in Section 4 because noise performance was insufficient to resolve low-LET events in the proton entrance channel; this post-hoc threshold shapes the reported proton spectra.
  • Slow shaper time = 1 µs
    Chosen as the optimal shaping time at which ENC=175 e is quoted (Section 3); affects SNR and rate capability.
  • Fast shaper time for PUR = 50 ns
    Set for the fast-slow pileup rejection channel (Section 3); effectiveness is asserted but not quantified.
assumptions (4)
  • domain assumption GATE Monte Carlo simulations correctly model the therapeutic beams and detector response
    Used to compute depth-dose curves and expected y.d(y) spectra in Figures 1 and 4; the paper does not validate the simulation itself.
  • domain assumption The diamond microdosimeter and readout chain respond linearly up to the carbon-edge energy deposition
    Linearization verified by charge injection up to 250 fC (Section 3), which is stated to correspond to the carbon edge; this extrapolates from injected charge to real particle events.
  • domain assumption Proton-edge calibration is valid for the diamond detector
    Used to convert pulse heights to lineal energy (Section 4), referencing [12] for gas TEPCs; transferability to a solid-state detector is assumed.
  • domain assumption The beam's micro-spill temporal structure can be exploited for pileup rejection
    Cited to the authors' own earlier work [22,23]; this underpins the pileup mitigation claim but is not re-derived or independently verified in this paper.

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Cite this review

Pith. "Pith review of Spectacular - A Modular DAQ System for Microdosimetry." pith.science (2026). https://pith.science/paper/4BAKUXOI

@misc{pith2026260803208,
  author       = {Pith},
  title        = {Pith review of: Spectacular - A Modular DAQ System for Microdosimetry},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/4BAKUXOI}},
  note         = {Machine review of arXiv:2608.03208}
}
abstract

Particle therapy using light ions like protons, helium ions or carbon ions enables precise tumor targeting with enhanced biological effectiveness while minimizing damage to healthy tissue. Successful treatment planning depends not only on the absorbed dose but also on quality of the radiation, as quantified by the linear energy transfer (LET). Microdosimetry provides a direct experimental determination of such quantities by measuring the energy deposited per incoming particle in micrometer-sized solid-state detectors representing the relevant biological scales. However, the small signal amplitudes and high particle rates in therapeutic ion beams challenge existing readout systems, which are not sufficiently optimized for reliable operation with respect to pileup and signal-to-noise ratio (SNR). To address this, a modular data acquisition (DAQ) system was developed to accelerate the design of custom readout electronics and sensor characterization in microdosimetry and related spectroscopic applications. Centered around a Xilinx Zynq system-on-chip, it combines real-time processing, high-bandwidth streaming, and high-resolution digitization (16 bit at 100 MSas$^{-1}$) to enable advanced digital signal processing. The platform integrates programmable power supplies, a bias-voltage filter, test-pulse generators, and flexible I/O. Detector and preamplifier front-ends are hosted on interchangeable daugtherboards connected via a standardized interface, allowing different hardware configurations and readout algorithms to be evaluated on the same platform. The Spectacular DAQ system was successfully tested at the MedAustron ion therapy facility with custom charge-sensitive amplifiers and a diamond microdosimeter. By enabling optimization fast testing of different readout electronics and sensors, it supports and advances the integration of microdosimetry into routine clinical practice.

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Reference graph

Works this paper leans on

26 extracted references · 26 canonical work pages

  1. [13]

    S. Jan, G. Santin, D. Strul, S. Staelens, K. Assié, D. Autret et al.,GATE: a simulation toolkit for PET and SPECT,

    work page

  2. [1]

    Hagiwara, T

    Y. Hagiwara, T. Bhattacharyya, N. Matsufuji, Y. Isozaki, H. Takiyama, K. Nemoto et al.,Influence of dose-averaged linear energy transfer on tumour control after carbon-ion radiation therapy for pancreatic cancer,

    work page

  3. [2]

    Matsumoto, S.H

    S. Matsumoto, S.H. Lee, R. Imai, T. Inaniwa, N. Matsufuji, M. Fukahori et al.,Unresectable chondrosarcomas treated with carbon ion radiotherapy: Relationship between dose-averaged linear energy transfer and local recurrence,

    work page

  4. [3]

    Molinelli, G

    S. Molinelli, G. Magro, A. Mairani, A. Allajbej, A. Mirandola, A. Chalaszczyk et al.,How LEM-based RBE and dose-averaged LET affected clinical outcomes of sacral chordoma patients treated with carbon ion radiotherapy,

    work page

  5. [4]

    F. Guan, L. Bronk, M. Kerr, Y. Li, L.A. Braby, M. Sobieski et al.,Interpreting the biological effects of protons as a function of physical quantity: linear energy transfer or microdosimetric lineal energy spectrum?,

    work page

  6. [5]

    Kalholm, L

    F. Kalholm, L. Grzanka, E. Traneus and N. Bassler,A systematic review on the usage of averaged LET in radiation biology for particle therapy,

    work page

  7. [6]

    Magini, P

    J. Magini, P. Pisciotta, M. Hussein, S. Both, A. Gerbershagen, E. Traneus et al.,Integration of microdosimetry into treatment planning systems using look-up tables (lut): A proof-of-concept, Physica Medica136(2025) 105031

    work page 2025

  8. [7]

    L.T. Tran, L. Chartier, D. Bolst, A. Pogossov, S. Guatelli, M. Petasecca et al.,Characterization of proton pencil beam scanning and passive beam using a high spatial resolution solid-state microdosimeter,Medical physics44(2017) 6085. – 7 –

    work page 2017

Show all 26 references
  1. [8]

    Petringa, C

    G. Petringa, C. Verona, A. Attili, L. Brighel, R. Catalano, G.A.P. Cirrone et al.,Microdosimetric characterization of a clinical helium beam using a microplus-bridge detector and a diamond detector for rbe assessment,Physics in Medicine & Biology70(2025) 195010

    2025

  2. [9]

    Magrin, C

    G. Magrin, C. Verona, M. Ciocca, M. Marinelli, E. Mastella, M. Stock et al.,Microdosimetric characterization of clinical carbon-ion beams using synthetic diamond detectors and spectral conversion methods,

  3. [10]

    S.H. Lee, K. Mizushima, R. Kohno, Y. Iwata, S. Yonai, T. Shirai et al.,Estimating the biological effects of helium, carbon, oxygen, and neon ion beams using 3d silicon microdosimeters,

  4. [11]

    Braby, V

    L.A. Braby, V. Conte, M. Dingfelder, D.T. Goodhead, L.S. Pinsky, A.B. Rosenfeld et al.,ICRU report 98, stochastic nature of radiation interactions: Microdosimetry,

  5. [12]

    Conte, D

    V. Conte, D. Moro, B. Grosswendt and P. Colautti,Lineal energy calibration of mini tissue-equivalent gas-proportional counters (TEPC),

  6. [14]

    Rosenfeld,Novel detectors for silicon based microdosimetry, their concepts and applications,

    A.B. Rosenfeld,Novel detectors for silicon based microdosimetry, their concepts and applications,

  7. [15]

    Guardiola, C

    C. Guardiola, C. Fleta, D. Quirion, G. Pellegrini and F. Gómez,Silicon 3d microdetectors for microdosimetry in hadron therapy,

  8. [16]

    Verona, G

    C. Verona, G. Verona Rinati, G. Schettino and G. Parisi,Development and fabrication of microdosimeter arrays based on single-crystal diamond schottky diodes,

  9. [17]

    Zahradnik, P

    I.A. Zahradnik, P. Barberet, D. Tromson, L. De Marzi and M.T. Pomorski,A diamond guard ring microdosimeter for ion beam therapy,

  10. [18]

    Davis, K

    J.A. Davis, K. Ganesan, D.A. Prokopovich, M. Petasecca, M.L.F. Lerch, D.N. Jamieson et al.,A 3D lateral electrode structure for diamond based microdosimetry,

  11. [19]

    Petringa, C

    G. Petringa, C. Verona, R. Catalano, M. Guarrera, A. Kurmanova, L. Brighel et al.,Toward the use of silicon carbide based detector for protontherapy microdosimetry,

  12. [20]

    Venegas, C

    M.J. Venegas, C. Guardiola, G. Pellegrini, C.T. Muñoz, J.G. López, M.D.C. Jiménez-Ramos et al., Ion-beam-induced charge study of new 4h-SiC detectors for microdosimetry,

  13. [21]

    Parisi, F

    G. Parisi, F. Romano and G. Schettino,Microdosimetry for hadron therapy: A state of the art of detection technology,

  14. [22]

    Knopf, A

    M. Knopf, A. Gsponer, M. Kausel, S. Waid, S. Onder, S. Gundacker et al.,Characterizing the delivered spill structure of medical proton and carbon-ion beams at MedAustron using a high frequency silicon carbide readout,

  15. [23]

    Knopf et al.,Measurements of the micro-spill structure of medical cyclotron and synchrotron beams and its impact on pulse pileup,2605.07508

    M. Knopf et al.,Measurements of the micro-spill structure of medical cyclotron and synchrotron beams and its impact on pulse pileup,2605.07508

    arXiv

  16. [24]

    S. Waid, M. Knopf, G. Magrin, A. Hirtl, S. Onder, S. Gundacker et al.,A frontend ASIC for microdosimetry,

  17. [25]

    Ohkawa, M

    S. Ohkawa, M. Yoshizawa and K. Husimi,Direct synthesis of the gaussian filter for nuclear pulse amplifiers,

  18. [26]

    Verona, A

    C. Verona, A. Fabbri, A. Fazzi, L. Bianchi, A. Bianchi, G.A.P. Cirrone et al.,Experimental characterization of a diamond detection system for combined dose, LET and RBE assessment in clinical proton beams, . – 8 –

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