Evaluation of Silicon-Based Photon-Counting CT for Coronary Stenosis Quantification with Realistic Coronary Artery Phantoms

Adam S. Wang; Bruno De Man; Ge Wang; Grant M. Stevens; Jed Pack; Koen Nieman; Maria Jose Medrano; Stephen Araujo

REVIEW 2 major objections 6 minor 7 references

Evaluation of Silicon-Based Photon-Counting CT for Coronary Stenosis Quantification with Realistic Coronary Artery Phantoms

T0 review · 2 major / 6 minor · reviewed 2026-08-07 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read Deep-silicon photon-counting CT improves coronary stenosis quantification in realistic calcified phantoms, cutting Micro-CT-referenced percent-area-stenosis error from 3.10% to 1.62%.

desk verdict A well-controlled phantom study with a plausible dSi-PCCT advantage, but the threshold-based segmentation and an apparent equation typo are the soft spots a referee should probe. read the letter →

arxiv 2608.06158 v1 pith:QJL5IO6E submitted 2026-08-06 physics.med-ph

Maria Jose Medrano , Jed Pack , Stephen Araujo , Grant M. Stevens , Koen Nieman , Ge Wang , Bruno De Man , Adam S. Wang This is my paper · ORCID

classification physics.med-ph PACS 87.57.Q

keywords photon-countingCTdeepsilicondetectorcoronarystenosisquantificationcalciumbloomingarteryphantomMicro-CTgroundtruthspatialresolutionenergy-integrating

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 sets out to establish that a deep-silicon photon-counting detector CT system (dSi-PCCT), by virtue of its higher native spatial resolution, quantifies coronary stenosis in calcified vessels more accurately than a conventional energy-integrating detector CT (EID-CT). The evidence comes from twelve realistic coronary phantom sections spanning four calcification geometries and three iodine concentrations, scanned statically and registered to Micro-CT as ground truth; the paper reports that Micro-CT-referenced percent area stenosis error fell from 3.10% to 1.62% mean absolute error (p=0.027) and segmented vessel-area error from 0.55 to 0.31 mm² (p=0.001). If correct, the result implies that the resolution limits of current detectors, not just motion or reconstruction choices, are a measurable cause of calcium-blooming stenosis overestimation, and it gives a quantitative baseline for judging future dynamic-phantom and clinical photon-counting CT studies.

What carries the argument

The argument is carried by a three-way scanner comparison on the same physical objects: a Micro-CT reference at 0.02 mm isotropic resolution, a conventional EID-CT scanner, and the dSi-PCCT scanner, with the two clinical systems run at dose-matched parameters but each at its resolution-optimized reconstruction (0.39×0.39×0.63 mm³ voxels with a Bone kernel for EID-CT versus 0.12×0.12×0.41 mm³ voxels with UHD Ultra and deep-learning reconstruction for dSi-PCCT). After rigid registration to Micro-CT, an automated three-class multi-Otsu thresholding step labels every voxel as lumen, calcification, or background; the union of the lumen and calcification masks defines the vessel area at each longitudinal position. Using the Micro-CT vessel area as the common denominator for both modalities converts the comparison into an isolation of segmentation and boundary-fidelity differences, which is what lets the paper attribute the improvement to reduced partial-volume and calcium-blooming effects from higher spatial resolution.

What would settle it

A reader-based contour study on the same registered phantom images that finds no meaningful difference in Micro-CT-referenced percent area stenosis MAE between dSi-PCCT and EID-CT (for example, a gap below one percentage point) would indicate the headline improvement is an artifact of the multi-Otsu thresholding rather than a true resolution benefit; equally, a dynamic phantom experiment in which simulated cardiac motion erases the gap would bound the clinical relevance.

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Extended reading notes

Core claim

On its own terms, the paper's central discovery is that, under matched static acquisition conditions, the dSi-PCCT system reproduces Micro-CT-referenced lumen and calcification geometry along calcified coronary phantom sections more faithfully than EID-CT, and that this boundary fidelity translates directly into lower percent-area-stenosis error. Across all 12 vessel sections the whole-profile mean absolute error in Micro-CT-referenced percent area stenosis drops from 3.10% (EID-CT) to 1.62% (dSi-PCCT), and segmented vessel-area MAE drops from 0.55 to 0.31 mm²; in the secondary ellipse-derived analysis the absolute deviation from Micro-CT ranges from 0.1% to 6.5% for dSi-PCCT versus 0.8% to 24.2% for EID-CT. The advantage is largest exactly where EID-CT struggles most: Type IV (circumferential) calcification and the lowest iodine concentration. The authors deliberately frame the primary metric as a task-based measure of imaging accuracy, distinct from conventional clinical percent stenosis, and they present the result as a baseline for dynamic and clinical follow-up.

Load-bearing premise

The load-bearing premise is that the automatic thresholding that separates lumen, calcium, and background is equally fair to both scanner types after registration; if the blurrier EID-CT images are systematically harder to threshold, the reported error gap could come from the segmentation tool rather than from the detector.

Editorial extensions

If this is right

If the result holds, high-resolution dSi-PCCT roughly halves the mean absolute error of percent area stenosis measurement in static calcified coronary phantoms, from 3.10% to 1.62%.
The largest improvements occur for circumferential (Type IV) calcification and at 10 mg/mL iodine, implying the technology helps exactly the high-risk calcified cases where conventional CCTA is least reliable.
The secondary ellipse-derived analysis shows the advantage also appears when the reference lumen is estimated from the image itself rather than from Micro-CT, suggesting the benefit is not an artifact of the ground-truth comparison.
The reported values provide a baseline for future dynamic-phantom and clinical CCTA studies to judge how much of the resolution gain survives cardiac motion and reader variability.

Reading between the lines

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

My inference: because the phantoms were static, the 1.48-percentage-point MAE gap is probably an upper bound for clinical practice; cardiac motion will add error to both systems, and motion correction or compensation will be needed to retain the resolution benefit in vivo.
A testable extension the authors did not run: add controlled motion to the same phantom set, for example with a moving platform or gated acquisitions at different heart rates, to measure how much of the dSi-PCCT advantage survives realistic blur.
My inference: the automated multi-Otsu pipeline could systematically favor the sharper modality; a reader-contour study on the same registered images would confirm whether the improvement is true boundary fidelity instead of thresholding behavior.
Because the paper did not use dSi-PCCT's spectral capabilities, the combined effect of high resolution plus material decomposition (iodine/calcium separation) is an open question and could be larger than the resolution-only gain reported here.

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Editorial analysis

A structured set of objections, weighed in public.

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

Desk Editor's Note

read the letter

Worth a read. This is the first quantitative stenosis-quantification comparison for the deep-silicon photon-counting detector against conventional EID-CT using realistic calcified coronary phantoms and an external Micro-CT reference. The study design is genuinely well-controlled: matched kVp and dose, system-specific resolution-optimized reconstructions, rigid registration to Micro-CT, longitudinal profile metrics, and a secondary ellipse-based analysis that agrees with the primary one. The reported reductions in MAE (3.10% to 1.62% for percent area stenosis, 0.55 to 0.31 mm² for vessel area) are plausible and the direction is consistent with prior CdTe PCCT work.

The main soft spot is exactly the one the paper flags in its own limitation section: the automated three-class multi-Otsu segmentation is load-bearing for every reported number, and modality-invariance of the thresholds is not demonstrated. Given the two systems differ in HU response, noise, kernel, and voxel size, an independent threshold-perturbation or reader-based sensitivity check would materially strengthen the central claim. The reader's concern about the 12 profiles coming from six phantoms is real but minor; the permutation test correctly treats each profile as a matched block, so the p-values are not egregiously liberal.

There is also a potentially important error in the manuscript text: Eq. 2 defines percent area stenosis as 100*A_lumen/A_vessel, but the Micro-CT values in Table 2 increase with calcification extent, which matches A_calc/A_vessel (or 100*(1 - A_lumen/A_vessel)). If the implementation used the printed equation, the reported numbers would be nonsense; more likely the equation has a typo. The authors should fix this before publication, because as written the metric is ambiguous.

The paper does not provide code or data, which limits independent replication, and the conclusions are appropriately scoped to static, resolution-optimized conditions. I do think the central argument holds up: the improvement is task-based, measured against an external reference, and the secondary analysis and the visible contours in the figures corroborate the primary result. I'd send this to peer review, asking for a threshold sensitivity analysis and a corrected Eq. 2. For someone working on CT performance evaluation or PCCT clinical translation, this is a useful data point.

Referee Report

2 major / 6 minor

Summary. This paper compares a conventional energy-integrating detector CT (EID-CT) scanner with a deep silicon photon-counting CT (dSi-PCCT) system for coronary stenosis quantification in realistic calcified coronary artery phantoms, using Micro-CT as the ground-truth reference. Twelve vessel sections spanning four calcification geometries and three iodine concentrations were scanned with all three systems, rigidly registered to Micro-CT, and segmented with an automated multi-Otsu pipeline. The primary analysis reports lower whole-profile mean absolute error in Micro-CT-referenced percent area stenosis for dSi-PCCT (1.62% vs 3.10%, p=0.027) and lower segmented vessel-area error (0.31 vs 0.55 mm², p=0.001); the secondary ellipse-derived analysis is concordant. The authors conclude that the high-resolution dSi-PCCT protocol improves task-based coronary stenosis quantification under static, resolution-optimized conditions.

Significance. If the results hold, this is a valuable controlled comparison for a newly cleared silicon-based photon-counting CT system. The study uses an external Micro-CT reference, matched kVp and tube current (dose), explicit pre-registered analysis, and a realistic phantom set with clinical calcification morphologies. The authors are transparent about limitations, especially the non-clinical automated segmentation and static imaging conditions. The main value is as a quantitative task-based baseline for future dynamic and clinical studies. However, the central estimate depends on the modality invariance of the multi-Otsu segmentation, which is not independently validated, and on statistical assumptions that may overstate significance because the 12 profiles come from only six physical phantoms.

major comments (2)

[2.3.1 / 4] The automated three-class multi-Otsu thresholding (Section 2.3.1) is the sole source of the lumen and calcification masks from which every reported metric is computed. The thresholds are estimated independently per volume, and the two modalities differ in HU response (276 vs 337 HU for 10 mg/mL iodine, Section 4), noise, voxel size, and reconstruction kernel. A systematic shift in the selected lumen/calcification boundary between EID-CT and dSi-PCCT would directly change the primary and secondary outcomes. The third limitation in Section 4 concedes that the pipeline does not reproduce the clinical workflow, but the manuscript provides no quantitative test of segmentation robustness. A threshold-perturbation sensitivity analysis, an independent reader-based validation on a subset, or a comparison against the known physical dimensions of the phantom would be needed to establish that the reported improvement reflects boundary fidelity rather than thresholding behavior. Because every MAE value depends on these masks, this is load-bearing for the central claim.
[2.3.3 / 8] The statistical comparison treats the 12 vessel-section profiles as independent matched blocks, but these profiles are derived from only six physical phantoms (three vessel geometries × two iodine concentrations), with multiple calcification regions per phantom. Profiles from the same physical phantom share manufacturing tolerances, registration transformations, and noise realizations, so the effective sample size is smaller than 12. The paired block permutation test in Section 2.3.3 does not account for this clustering. For the primary percent-area-stenosis MAE, the reported p=0.027 may not survive a phantom-level clustered analysis. Please report per-phantom or per-geometry MAE values and provide a clustered permutation test or a mixed-effects analysis, and consider the two primary endpoints together when interpreting significance.

minor comments (6)

[2.2 / Table I] In Table I, the dSi-PCCT and Micro-CT rows omit the kVp value (120 kVp is given in the text). The table should list all acquisition parameters explicitly and consistently for each system.
[2.3.1] The two-step multi-Otsu segmentation strategy 'for vessel sections containing the highest iodine concentration' is mentioned but not described; please specify how the second step is initialized and why this adaptation is needed only at the highest concentration.
[4] The conclusion attributes the improvement to the detector's higher native resolution, but the comparison also involves different reconstruction algorithms (DL-High UHD Ultra vs ASiR-V 50% Bone) and voxel sizes. The manuscript mostly phrases this as a system-level protocol comparison, but the abstract and conclusion should consistently avoid implying a pure detector-physics attribution.
[2.3.3] With 12 paired profiles, there are only 2^12 = 4096 distinct sign permutations; if the 10,000-permutation procedure uses resampling rather than exact enumeration, the discreteness of the permutation distribution should be acknowledged when reporting p-values.
[2.3.3] For the primary analysis, profiles are aligned by assigning each modality's own slice of maximum calcification to z=0. If blooming shifts the calcification peak location in EID-CT, this alignment could shift the EID-CT profile relative to the Micro-CT reference and inflate the MAE. Please clarify whether the Micro-CT reference z-grid is used as the common coordinate for all modalities.
[Table 2 / Eq. 2] The Micro-CT values in Table 2 are ellipse-derived percent area stenosis (Eq. 3) at the maximum-calcification cross-section, not values computed with Eq. 2. The observation that these values increase with calcification extent is consistent with Eq. 2 as well, because A_lumen/A_vessel decreases as calcification increases; there is no internal inconsistency between the two formulations.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the comparison is an externally benchmarked measurement study.

full rationale

The paper is an empirical imaging comparison, not a derivation. The primary endpoint is the mean absolute error between modality-specific segmentations and an independently measured Micro-CT reference, with all metrics computed directly from registered image volumes (Eqs. 1-4). No parameter is fitted to the Micro-CT stenosis values, and no predicted quantity is defined in terms of the outcome it is claimed to explain. The multi-Otsu segmentation thresholds are estimated from image intensity distributions per modality, not from the reference stenosis measurements, so the relative EID-CT versus dSi-PCCT difference is not forced by construction. The phantom provenance citation (Pack et al., 2024) is used to describe physical phantom design and fabrication, not to justify the reported accuracy; the Micro-CT ground truth is a separate measured dataset. Although the phantom developers and system vendor overlap with the author list, this is a conflict-of-interest consideration rather than circularity, and it does not reduce the central claim to a self-citation. The acknowledged limitations about threshold-based segmentation and the non-clinical workflow are validity concerns, not evidence that the result is equivalent to its inputs. The study is self-contained against an external benchmark, so the appropriate circularity score is 0.

Assumptions & free parameters 2 free parameters · 4 assumptions · 0 invented entities

The central claim depends on four domain assumptions: Micro-CT is a valid ground truth, multi-Otsu segmentation is unbiased across modalities, static ex vivo conditions isolate resolution effects, and the 3D-printed calcium phantoms represent clinical plaque. Free parameters are limited to segmentation thresholds and morphological post-processing choices, whose values are not reported. No invented entities are introduced.

free parameters (2)

Multi-Otsu intensity thresholds (K=3) = not reported (computed per image)
Each image's thresholds are fit to its own histogram and determine which voxels become lumen versus calcification; all reported area errors depend on these thresholds.
Morphological post-processing area threshold = not specified
Isolated-component removal and gap filling use area-based thresholds that can change segmented vessel area; values are not reported.

assumptions (4)

domain assumption Micro-CT at 0.02 mm isotropic resolution is an unbiased ground truth for lumen and calcification areas.
The entire comparison defines errors as deviations from Micro-CT-derived masks; if Micro-CT itself suffers partial-volume or threshold bias, all modality MAEs inherit it.
domain assumption The automated multi-Otsu threshold segmentation performs equivalently across modalities and does not favor the higher-resolution system.
The paper's central conclusion depends on this; the Discussion acknowledges that reader-based studies and independent segmentation validation are needed.
domain assumption Static scanning and system-specific high-resolution reconstructions isolate the effect of intrinsic spatial resolution.
Motion and reconstruction differences can modulate blooming; the authors scope the claim to static, resolution-optimized conditions.
domain assumption The 3D-printed phantoms with calcium-epoxy paste reproduce clinical calcified plaque attenuation and geometry.
Phantom realism is inherited from Pack et al. 2024; the current paper does not independently validate attenuation values.

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Cite this review

Pith. "Pith review of Evaluation of Silicon-Based Photon-Counting CT for Coronary Stenosis Quantification with Realistic Coronary Artery Phantoms." pith.science (2026). https://pith.science/paper/QJL5IO6E

@misc{pith2026260806158,
  author       = {Pith},
  title        = {Pith review of: Evaluation of Silicon-Based Photon-Counting CT for Coronary Stenosis Quantification with Realistic Coronary Artery Phantoms},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/QJL5IO6E}},
  note         = {Machine review of arXiv:2608.06158}
}

read the original abstract

Objective: To quantify the impact of high-resolution deep silicon photon-counting CT (dSi-PCCT) on coronary stenosis quantification in anatomically realistic calcified coronary artery phantoms using Micro-CT as ground truth. Methods: Twelve vessel sections representing four calcification geometries (Type I-IV) and three luminal iodine concentrations (10, 15, and 20 mg/mL) were scanned under static conditions using energy-integrating detector CT (EID-CT), dSi-PCCT, and Micro-CT. Images were registered to Micro-CT and segmented using an automated threshold-based pipeline. The primary analysis compared longitudinal profiles of Micro-CT-referenced percent area stenosis and segmented vessel area. A secondary analysis evaluated ellipse-derived percent area stenosis and percent vessel-area deviation at the maximum-calcification cross-section. Results: dSi-PCCT reduced whole-profile mean absolute error in Micro-CT-referenced percent area stenosis from 3.10% with EID-CT to 1.62% (p=0.027) and reduced segmented vessel-area error from 0.55 to 0.31 mm2 (p=0.001). In the secondary analysis, absolute deviations in ellipse-derived percent area stenosis ranged from 0.1% to 6.5% for dSi-PCCT and from 0.8% to 24.2% for EID-CT (p<0.001). Mean absolute differences in percent vessel-area deviation from Micro-CT were also lower with dSi-PCCT than with EID-CT (15.0% vs 26.6%, p<0.001). Conclusion: Under static, resolution-optimized conditions, dSi-PCCT improved task-based coronary stenosis quantification and vessel delineation relative to EID-CT, supporting further evaluation in dynamic phantoms and clinical CCTA.

Figures

Figures reproduced from arXiv: 2608.06158 by the authors.

**Figure 1.** (a) Sample 3D-printed coronary artery phantom model. Pits along the vessel wall were designed to accommodate calcium-epoxy paste. (b) Representative calcified plaque geometries as defined by (Qi et al., 2016), classified by the number of vessel-wall quadrants occupied by the plaque in cross-sectional view. (c) Coronary vessel phantom positioned within a cylindrical enclosure [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗

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Reference graph

Works this paper leans on

7 extracted references · 6 canonical work pages

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INTRODUCTION Coronary computed tomography angiography (CCTA) is recommended as a first-line imaging test for evaluating coronary artery disease (CAD) in low-to-intermediate risk patients (Gulati et al., 2021). However, CAD detection in CCTA exams remains limited for high-risk patients with dense calcifications and stents, where it is not routinely recomme...

work page 2021
[2]

To isolate the effects of intrinsic spatial resolution from motion-related artifacts, all scans were performed under static conditions

METHODS AND MATERIALS A set of realistic coronary artery phantoms derived from clinical coronary CT angiography (CCTA) examinations was scanned using three CT systems: a conventional energy-integrating detector CT (EID-CT), which served as the comparative baseline; a deep silicon-based photon-counting CT (dSi-PCCT) evaluated in this study; and a Micro-CT,...

work page 2024
[4]

In the primary Micro-CT-referenced analysis, dSi-PCCT reduced whole-profile mean absolute error in percent area stenosis from 3.10% with EID-CT to 1.62% (p=0.027)

DISCUSSION In this study, we evaluated the impact of high-resolution dSi-PCCT on coronary stenosis quantification using anatomically realistic calcified coronary artery phantoms. In the primary Micro-CT-referenced analysis, dSi-PCCT reduced whole-profile mean absolute error in percent area stenosis from 3.10% with EID-CT to 1.62% (p=0.027). dSi-PCCT also ...

work page 2022
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Influence of slice thickness and reconstruction kernel on the computed tomographic attenuation of coronary atherosclerotic plaque,

CONCLUSIONS In summary, silicon-based photon-counting CT reduced blooming artifacts and improved coronary stenosis quantification compared with EID-CT across a range of calcification morphologies and luminal attenuation levels. The greatest improvements were observed for heavily calcified vessels, where blooming-related errors are most pronounced. These f...

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Ex vivo coronary calcium volume quantification using a high-spatial-resolution clinical photon-counting-detector computed tomography,

Available at: https://doi.org/10.3389/fninf.2013.00045. Marsh, J.F. et al. (2023) “Ex vivo coronary calcium volume quantification using a high-spatial-resolution clinical photon-counting-detector computed tomography,” Journal of Medical Imaging, 10(04). Available at: https://doi.org/10.1117/1.JMI.10.4.043501. Mergen, V. et al. (2022) “Ultra-High-Resolutio...

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(Figure 1b), calcified plaque geometries were categorized into four calcification types (I–IV) according to the number of vessel-wall quadrants occupied by plaque in cross-sectional view. Calcification pits were incorporated into seven to eight regions along each vessel segment and were designed to span one, two, three, or four quadrants of the lumen circ...

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Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.

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INTRODUCTION Coronary computed tomography angiography (CCTA) is recommended as a first-line imaging test for evaluating coronary artery disease (CAD) in low-to-intermediate risk patients (Gulati et al., 2021). However, CAD detection in CCTA exams remains limited for high-risk patients with dense calcifications and stents, where it is not routinely recomme...

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To isolate the effects of intrinsic spatial resolution from motion-related artifacts, all scans were performed under static conditions

METHODS AND MATERIALS A set of realistic coronary artery phantoms derived from clinical coronary CT angiography (CCTA) examinations was scanned using three CT systems: a conventional energy-integrating detector CT (EID-CT), which served as the comparative baseline; a deep silicon-based photon-counting CT (dSi-PCCT) evaluated in this study; and a Micro-CT,...

work page 2024

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In the primary Micro-CT-referenced analysis, dSi-PCCT reduced whole-profile mean absolute error in percent area stenosis from 3.10% with EID-CT to 1.62% (p=0.027)

DISCUSSION In this study, we evaluated the impact of high-resolution dSi-PCCT on coronary stenosis quantification using anatomically realistic calcified coronary artery phantoms. In the primary Micro-CT-referenced analysis, dSi-PCCT reduced whole-profile mean absolute error in percent area stenosis from 3.10% with EID-CT to 1.62% (p=0.027). dSi-PCCT also ...

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Influence of slice thickness and reconstruction kernel on the computed tomographic attenuation of coronary atherosclerotic plaque,

CONCLUSIONS In summary, silicon-based photon-counting CT reduced blooming artifacts and improved coronary stenosis quantification compared with EID-CT across a range of calcification morphologies and luminal attenuation levels. The greatest improvements were observed for heavily calcified vessels, where blooming-related errors are most pronounced. These f...

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Ex vivo coronary calcium volume quantification using a high-spatial-resolution clinical photon-counting-detector computed tomography,

Available at: https://doi.org/10.3389/fninf.2013.00045. Marsh, J.F. et al. (2023) “Ex vivo coronary calcium volume quantification using a high-spatial-resolution clinical photon-counting-detector computed tomography,” Journal of Medical Imaging, 10(04). Available at: https://doi.org/10.1117/1.JMI.10.4.043501. Mergen, V. et al. (2022) “Ultra-High-Resolutio...

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(Figure 1b), calcified plaque geometries were categorized into four calcification types (I–IV) according to the number of vessel-wall quadrants occupied by plaque in cross-sectional view. Calcification pits were incorporated into seven to eight regions along each vessel segment and were designed to span one, two, three, or four quadrants of the lumen circ...

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