Clinical Impact of Cardiac Photon-Counting Detector CT: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Impact of Cardiac Photon-Counting Detector CT (NCT05240807), a non-randomized na study. The primary outcome is Arm 1: Change in Clinical Coronary Artery Disease Status Measured in Photon-counting Detector CT Relative to Clinical CT as Measured by Percent Area Stenosis.

2. Clinical Question

3. Trial Design

This was a completed, non-randomized, parallel-model diagnostic imaging study sponsored by Mayo Clinic. The registry lists the study phase as not applicable and the masking as none. Enrollment was 276. The study start date is 2022-08-24, and the primary completion date is 2026-02-19. The two cohorts were defined by the clinical examination participants were scheduled to receive, rather than by random assignment to competing diagnostic strategies.

The Clinical Coronary CTA Cohort included people scheduled for clinically indicated coronary CT angiography. They received a research contrast-enhanced coronary angiogram using PCD-CT, alongside the clinical CT angiography used for the primary comparison. The registry describes 235 participants enrolled in this arm. The primary analysis population was narrower: 139 participants were analyzed because the endpoint applied to those with evaluable, calcified stenosis.

The second cohort included people scheduled for a clinically indicated nuclear medicine or MRI cardiac stress test. They received research PCD-CT angiography at rest and after administration of a cardiac stress agent. The registry lists 11 participants in this cohort. Outcomes listed for this arm include reader sensitivity and specificity for myocardial perfusion defects imaged by PCD-CT during cardiac stress.

The registry lists 4 outcome measures and 1 analysis. It also notes a scanner update during recruitment: a multi-energy ultra-high resolution update enabled a scan mode collecting x-ray energy data, and that mode was used for all patients recruited after the update. The record does not report the number of participants scanned before or after the update or how that change was handled analytically. Detailed eligibility criteria, recruitment procedures, and the statistical analysis plan are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: After their clinical scan and before their research scan (intervention), 25 patients withdrew consent, 4 patients failed to meet the inclusion criteria, and 1 patient had an issue with IV placement that prevented scanning resulting in a final cohort of 246 patients.

Overall Study

Analysis population for the primary outcome, as defined in the registry: To compare PAS, PCD and EID-CT scans are needed so only arm 1 participants were analyzed in this measure. 235 participants were enrolled in arm 1, however 139 participants were analyzed as this outcome measure only pertains to the subset of patients with evaluable, calcified stenosis (i.e., low motion artifact, visible in both scans). Arm 1 was split into and analyzed in 2 groups due to a change in PCD-CT technology during recruitment (multi-energy ultra-high resolution update).

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Arm 1: Change in Clinical Coronary Artery Disease Status Measured in Photon-counting Detector CT Relative to Clinical CT as Measured by Percent Area Stenosis, measured over Through completion of CT exam, approximately 1 hour.

The primary endpoint is change in percent area stenosis (PAS) measured by PCD-CT relative to clinical EID-CT in Arm 1. PAS is a measure of coronary narrowing based on the vessel cross-sectional area at the region of greatest stenosis relative to the healthy vessel cross-sectional area. It ranges from 0% to 100%; higher values indicate worse stenosis. The registered measure focuses on the site of worst stenosis in each coronary vessel or patient, using validated commercial software.

For each stenosis, the record describes measuring PAS at the same location on the PCD-CT and clinical EID-CT scans, then subtracting the values to obtain a change. This paired, same-location approach asks whether the two imaging methods produce different measurements for the stenosis being evaluated. It does not by itself establish that one measurement is closer to the underlying biological truth, nor does it show whether a change in measurement altered care.

The endpoint is summarized as a median with a 95% confidence interval, and its timeframe is through completion of the CT examination, approximately 1 hour. A median describes the midpoint of the observed distribution, while the confidence interval conveys uncertainty around the reported estimate under the analysis method. The registry record does not report the median change, its confidence interval, or enough statistical detail to identify how that interval was constructed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary measure compare?

The primary measure compares PAS assessed on PCD-CT with PAS assessed on clinical EID-CT. According to the registry, the measurements were taken at the same stenosis location, and the values were subtracted to represent change. This is a paired measurement structure: each stenosis has a measurement from each imaging method. In general, pairing can be useful because the comparison is made within the same observed lesion rather than between unrelated groups. It does not remove all sources of measurement error or ensure that the paired observations are representative of a broader population.

The endpoint description specifies a median summary. In general, the median is the central value after observations are ordered and can be less affected by unusually high or low observations than the arithmetic mean. That property can make it a useful summary when a distribution is asymmetric or contains outlying values. The registry does not report the distribution of individual changes, so it is not possible to judge from the record whether the median captures the shape or spread of the observed changes adequately.

What does a 95% confidence interval communicate?

The registered dispersion measure is a 95% confidence interval. In general, a confidence interval expresses the uncertainty associated with an estimate under a specified statistical procedure. Its width depends on the data and the method used; a narrower interval indicates greater precision under that procedure, while a wider interval indicates less precision. A confidence interval is not a guarantee that the true value lies inside the particular reported interval, and it does not by itself show whether a difference is clinically important.

The registry record does not report the interval endpoints or the method used to construct the interval. It also does not report a hypothesis test for the primary measure. Without the numerical estimate and interval, the observed direction, scale, and precision of the change cannot be evaluated. A significance claim cannot be inferred from the endpoint description alone.

Why does the analysis population matter?

The primary measure is restricted to participants with evaluable, calcified stenosis. The record lists 235 participants enrolled in Arm 1 and 139 analyzed for this endpoint. The subset restriction means that the endpoint estimate, if reported, would describe the analyzed participants meeting that criterion. Generalizing it to the whole cohort would require information about how analyzed and non-analyzed participants differed and whether evaluability was related to scan quality, stenosis characteristics, or other factors. Those details are not reported in the registry record.

In general, restricting an analysis to evaluable observations can affect both precision and representativeness. Missing or unevaluable measurements may reduce the amount of information available and can introduce bias if the chance of having an evaluable measurement is associated with the outcome. The record does not describe missing-data methods, reasons for non-analysis beyond the endpoint's stated subset criterion, or sensitivity analyses.

What can be inferred from the study design?

The study is described as non-randomized, with no masking. The cohorts reflect participants' scheduled clinical examinations, and the registry cautions against treating the arms as like-for-like controls. General statistical interpretation therefore distinguishes the paired imaging comparison in Arm 1 from comparisons between the two cohorts. The former can assess differences between paired measurements in the analyzed sample. It does not establish that PCD-CT caused a change in management or improved clinical outcomes. The registry does not report a randomized treatment allocation or a masking procedure.

The outcome description says the same stenosis location was assessed on both scans, which is relevant to measurement comparability. It does not report details such as reader training, reproducibility assessments, rules for selecting the worst stenosis, or whether readings were blinded to the other scan's measurement. These elements could affect measurement consistency, but their presence or absence cannot be assumed.

How should the sample-size illustrations be read?

The record describes sample-size calculations as planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is expressed as a stated fraction of the observed effect. In general, such calculations illustrate the sample size associated with specified assumptions; they do not describe the trial's observed power. The record emphasizes that these are not the trial's own design assumptions. Numerical illustration results and the observed effect used for them are not reported in the registry record, so no sample-size values or effect magnitude can be interpreted.

For time-to-event outcomes, the record says planning figures use total events, while other figures use participants per arm. These distinctions concern how planning quantities are expressed, not evidence that the study itself was randomized or that an outcome effect was demonstrated. The registry does not report a rationale for the original enrollment target, a formal sample-size justification, interim analyses, or a detailed statistical plan.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures and 1 analysis, but a detailed statistical analysis plan is not reported in the registry record. It does not state whether one outcome was designated as the sole confirmatory endpoint for inference, how multiple outcomes were prioritized, or whether any adjustment for multiple comparisons was planned or performed. When several outcomes are assessed, general statistical practice recognizes that repeated testing can increase the chance of at least one apparently notable result. Whether that issue applies to the reported analyses cannot be determined without the analysis plan and results.

The primary endpoint is defined for an analyzed subset of Arm 1: 139 participants with evaluable, calcified stenosis, among 235 enrolled in that arm. The record does not describe a complete participant flow for this endpoint, the reasons each otherwise enrolled participant was not analyzed, or whether all eligible stenoses were measurable. It does not report a missing-data strategy, imputation, sensitivity analyses, or a comparison of included and excluded participants. These omissions limit assessment of whether the analyzed observations could differ systematically from those not analyzed.

The record also does not report prespecified subgroup analyses or whether the scanner update was considered in the analysis. It states that the multi-energy ultra-high resolution mode was used for all participants recruited after the update, but does not describe an analysis by scan mode or a method for accounting for changes over recruitment. The specific statistical model, assumptions checks, and handling of repeated stenoses within participants are not reported in the registry record. The available information therefore supports describing the endpoint definition and analysis population, but not reconstructing the inferential procedure or evaluating multiplicity and missing-data assumptions in detail.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry records adverse-event counts separately for the Clinical Coronary CTA Cohort and the Clinical Nuclear Medicine or MRI Cardiac Stress Test Cohort. For the coronary CTA cohort, the listed number at risk for serious adverse events is 235, with 0 affected; the other adverse-event count also lists 235 at risk and 0 affected. For the stress-test cohort, the corresponding at-risk counts are 11, with 0 affected for serious and other adverse events. Deaths are listed as 0 in both cohorts. The record lists no top serious adverse-event terms.

These are the counts recorded in the registry, not evidence that no adverse events of any kind occurred in every setting. The record does not provide event definitions, collection procedures, observation duration beyond the listed study context, or detail about events judged unrelated to the imaging procedures. The displayed zeros should therefore be read as zero events recorded in these registry categories, rather than proof of absence of all possible harms. The figures also do not establish comparative safety: the study was non-randomized, and the registry warns that its arms are not like-for-like controls.

12. What the Result Does, and Does Not, Mean

The study asks whether PCD-CT provides clinically important information about suspected coronary artery disease and perfusion defects compared with other diagnostic imaging. Its primary registered measure is narrower: the change in PAS between PCD-CT and clinical EID-CT at the site of worst stenosis, among analyzed participants in the coronary CTA cohort. The registry record describes how this measurement was defined and identifies the population analyzed, but does not report the numerical primary result. It is therefore not possible to say from the registry record how large the change was, which direction it took, or how precisely it was estimated.

Even if a numerical measurement difference were available, a difference in PAS would not alone establish that patient management changed, that a change was beneficial, or that clinical outcomes improved. The endpoint is a comparison of imaging measurements. The study purpose refers to management impact, but the record does not report a patient-management outcome result in the information.

The separate stress-test cohort was intended to inform assessment of myocardial perfusion defects, with reader sensitivity and specificity listed as outcomes. Numerical results for those outcomes are not reported in the registry record. Thus the record does not establish diagnostic sensitivity, specificity, or comparative performance for stress imaging.

The non-randomized design and the distinct clinical cohorts also limit direct comparisons between arms. They were assembled according to scheduled clinical examinations, and the registry explicitly notes that the arms are not a like-for-like control comparison. The study can be understood as evaluating imaging measurements in its defined cohorts, but it should not be interpreted as a randomized trial of competing patient-management strategies.

The appropriate conclusion is consequently limited: the registry documents a completed imaging study, a defined paired stenosis measure, and specified cohorts, but does not provide the primary outcome estimate or the listed diagnostic accuracy results. The data recorded are insufficient to determine the size, precision, or clinical implications of those outcomes.

13. Why This Trial Matters Statistically

This trial raises a statistical question central to diagnostic imaging: whether two imaging technologies produce different quantitative assessments when applied to the same lesion. Measuring PAS at the same location on PCD-CT and clinical EID-CT provides a paired comparison, which differs from comparing unrelated groups. The endpoint is also clinically interpretable in concept because it describes the degree of vessel narrowing, while its actual relevance to decisions depends on results and management data that are not reported in the registry record.

The analysis population illustrates why endpoint definitions and participant flow matter. Although 235 participants were enrolled in the coronary CTA cohort, 139 were analyzed for the primary measure because it applied to a subset with evaluable, calcified stenosis. Readers need both the endpoint definition and the scope of the analyzed sample to understand what a result would represent. The registry does not supply the numerical estimate or detailed information about exclusions, so the degree to which the analyzed subset reflects the broader cohort cannot be assessed.

The scanner update during recruitment adds another dimension to measurement studies: technology and acquisition modes can change while a study is underway. The record notes that a multi-energy ultra-high resolution mode was used after the update, but does not report analyses by mode. This does not show that the update affected results; it identifies a feature of the study context that would be useful to consider alongside measurement estimates.

Finally, this record shows why a completed status alone is not enough for statistical interpretation. Understanding evidence requires the estimate, its uncertainty, the analysis population, and the methods used. Here, the endpoint and design are described, but key outcome estimates and analysis details are not reported. The distinction between a clearly defined statistical question and an interpretable numerical answer is important for clinical researchers evaluating diagnostic studies.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary numerical result is not reported in the registry record. The median change in PAS and its 95% confidence interval are both absent, preventing assessment of direction, magnitude, and precision. The detailed results for reader sensitivity and specificity in the stress-test cohort are also not reported. These gaps prevent a quantitative interpretation of the outcomes named in the record.

The primary analysis concerns 139 participants, whereas 235 were enrolled in Arm 1. The record attributes this restriction to the endpoint applying to participants with evaluable, calcified stenosis, but does not provide a complete account of participant flow, further eligibility details for the analysis, or characteristics of those not analyzed. It is therefore not possible to assess whether selection into the analysis population could affect the result or its generalizability.

The non-randomized design and absence of masking are recorded study features. The registry states that the two arms are not a like-for-like control comparison, so between-arm contrasts should not be interpreted as if created by random assignment. The primary endpoint compares imaging measurements within Arm 1, but the record does not report reader blinding, reproducibility, or procedures for handling multiple stenoses from the same participant.

The scanner underwent a multi-energy ultra-high resolution update during recruitment. The registry does not report the distribution of participants across scan modes or whether the update was considered in the analysis. It also does not report a detailed statistical plan, missing-data methods, multiplicity procedures, or the construction method for the confidence interval. These limitations concern what can be evaluated from the registry record; they do not establish that any particular method was or was not used.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Clinical Impact of Cardiac Photon-Counting Detector CT — NCT05240807.
• Registry record last updated 2026-06-12; status last verified 2026-06.
• Results first posted 2026-06-12.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry describes a completed, non-randomized, parallel-model diagnostic imaging study sponsored by Mayo Clinic, with enrollment of 276 and no masking. Participants scheduled for coronary CT angiography received research PCD-CT, as did participants scheduled for nuclear medicine or MRI cardiac stress testing, with stress imaging performed at rest and after a cardiac stress agent.

The primary endpoint compares PAS measured on PCD-CT and clinical EID-CT in the coronary CTA cohort. The registry lists a median change with a 95% confidence interval and reports that 139 participants were analyzed for this outcome from the 235 enrolled in Arm 1. The primary estimate, confidence interval, detailed analysis methods, and numerical results for the listed stress-test outcomes are not reported in the registry record.