EXPLORER PET/CT: Evaluation of Healthy Individuals From Racial/Ethnic Minority Populations: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for EXPLORER PET/CT: Evaluation of Healthy Individuals From Racial/Ethnic Minority Populations (NCT04812080), a na na study. The primary outcome is Standardized Uptake Value (SUV) in gm/ml Reported as Mean and Standard Deviation.

2. Clinical Question

This is an imaging pilot, not a randomized treatment comparison. Its focus is the feasibility of collecting total-body PET/CT measurements with the EXPLORER scanner and describing uptake across the scan timepoints. The primary outcome is specified as SUV in gm/ml, reported as a mean and standard deviation, with a timeframe of 3 hours.

The registry describes the cohort as healthy volunteers from racial/ethnic minority populations. The stated objective is to gather preliminary imaging data in this population. The record does not set out a comparison with another scanner, a control cohort, or another imaging protocol. It therefore cannot answer whether EXPLORER measurements differ from measurements obtained under a comparator condition, nor does it report a clinical treatment effect.

The central statistical question is descriptive: what SUV measurements were observed, and how variable were those measurements? The registry record identifies the intended summary statistics but does not report the resulting means or standard deviations. It also does not report outcome analyses. The clinical question can therefore be described from the study objective and endpoint definition, but the numerical answer cannot be assessed from the registry record.

3. Trial Design

NCT04812080 is a completed, single-group imaging study sponsored by the University of California, Davis. The registry lists phase as NA, allocation as NA, and masking as none. The planned enrollment was 20. Its title and stated objective describe evaluation of healthy individuals from racial/ethnic minority populations using the EXPLORER PET/CT scanner.

The intervention is an imaging procedure rather than a medication or a comparison of treatment strategies. The arm description says participants received 10 +/- 2 mCi of 18F-FDG through an IV line. An ultra-low-dose CT scan, described as less than 1 minute, was acquired for attenuation correction. The arm description also specifies a 60 minute PET scan. The outcome population description states that participants completed a dynamic scan for 60 minutes and two scans at 90- and 120-minutes post-injection, each lasting 20-minutes. The record's arm description is truncated after its reference to a further time after injection, so no additional procedural detail can be established from that text.

The registry gives a start date of 2021-08-18, a primary completion date of 2021-11-08, and a status of COMPLETED. Completion describes the study's registry status; it does not itself establish that numerical outcome results were posted. The record lists two outcome measures and zero analyses. It does not report a randomized allocation process, a masking procedure, or a parallel control group. As a result, the design supports description of measurements collected in the study cohort, rather than a like-for-like comparison between groups.

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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: All the participants completed their scheduled scans at three timepoints: dynamic scan for 60 minutes, two scans at 90- and 120-minutes post-injection, for 20-minutes each.

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 Standardized Uptake Value (SUV) in gm/ml Reported as Mean and Standard Deviation, measured over 3 hours.

The primary endpoint is Standardized Uptake Value (SUV) in gm/ml, described as a mean with standard deviation and assessed over a timeframe of 3 hours. The stated objective is to collect preliminary information about total body FDG perfusion and early biodistribution in the enrolled cohort. The registry describes SUV as a ratio involving image-derived radioactivity concentration and whole-body radioactivity concentration.

SUV is used in PET imaging as a way to express measured radiotracer uptake in relation to the amount of radioactivity in the body. In general, expressing uptake as a standardized measure can help researchers describe and compare measurements across sampled regions or scan times. That general purpose does not make an SUV result a direct measure of clinical benefit, nor does it by itself establish that uptake is clinically important.

For a continuous outcome, a mean describes the central value of measurements, while a standard deviation describes their spread around that mean. These summaries can help characterize both the typical measured uptake and the variation among observations. Their interpretation depends on knowing the measurement context, including the scan timing and the population from which the observations came.

The registry identifies the planned summary format but does not report the observed mean or standard deviation. It also does not provide region-specific results or other details needed to assess how SUV values were selected or aggregated. Therefore, the endpoint's purpose and scale can be explained, but its observed magnitude and variability are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean and standard deviation describe?

The primary outcome is continuous and is specified to be reported as a mean and standard deviation. In general, the mean summarizes the center of a set of measurements. The standard deviation describes how dispersed those measurements are around the mean. Together, these summaries can convey the typical observed SUV and the variability in the cohort. They do not show the full distribution, and they can be affected by unusually high or low observations.

Neither summary is reported numerically in the registry record. As a result, the actual center and spread of the SUV observations cannot be evaluated. A specified summary format is not the same as a posted result.

What would a confidence interval add?

In general, a confidence interval expresses the uncertainty around an estimated quantity under a statistical model. It provides a range of values compatible with the data and method at a stated confidence level. A narrower interval generally indicates greater precision, while a wider interval indicates more uncertainty. A confidence interval is not reported for the primary endpoint in the registry record, so its precision cannot be assessed from a posted interval.

Even when available, an interval would address statistical uncertainty in an estimate, not whether an SUV value is clinically important. Interpretation would also depend on the measurement context and on what difference or range would matter for the study's scientific purpose. Those criteria are not reported in the registry record.

Why does the single-group design matter?

A single-group design can describe measurements collected in a cohort, but it does not create a concurrent control comparison. Here, the registry lists a single-group model and allocation as NA. There is no randomized comparator arm to separate differences associated with the scanner or scan procedure from other sources of variation. The data could characterize measurements within the enrolled cohort if results were available, but the design does not support a randomized between-group effect estimate.

The study is also described as a pilot intended to collect preliminary information. In general, pilot data can inform measurement procedures and the planning of later research. They are not, by themselves, evidence of a definitive clinical effect. The registry record does not report a protocol, a formal sample-size justification, or a prespecified threshold for interpreting SUV values.

How should the planning illustrations be read?

The registry's planning assumptions describe a calculation based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These are planning assumptions, not a report of this study's actual design: the registered study is single-group. A planning illustration asks how many participants per arm might be needed under specified assumptions in a hypothetical comparison. It does not indicate how many participants were observed to have an outcome, and it is not observed power.

In general, planning calculations depend on the effect size chosen, the variability assumed, the allocation, and the analysis method. If the effect to detect is expressed as a fraction of an observed effect, smaller target effects generally require larger samples under otherwise similar assumptions. That is a general statistical relationship, not a numerical conclusion about this study. The registry assumptions do not give the numerical effect fractions or planning results in the record. No planning value should be treated as the study's observed result.

What role can over-dispersion play?

Over-dispersion is a general issue for count data when variation exceeds what a simple probability model expects. It can make standard errors too small if a model assumes less variability than the data contain. The primary outcome in this record is a continuous SUV measure, not a count endpoint, and no count analysis is reported. Over-dispersion is therefore not a reported feature of this study's primary analysis. More broadly, an analysis method should match the data type and its distribution; the statistical analysis plan is not reported in the registry record.

For continuous measurements, researchers may need to consider distribution shape, influential observations, repeated measurements, and the dependence among observations collected from the same participant. The registry description identifies repeated scan timepoints but does not report the model or approach used to account for within-participant measurements. No such approach should be inferred from the outcome description alone.

What can be concluded from the analysis record?

The registry lists zero analyses and supplies no numerical primary outcome results. Thus, there is no reported test statistic, p-value, confidence interval, or adjusted estimate to interpret. The registry record also does not report whether a prespecified analysis plan existed or whether any interim analyses were conducted. Without posted estimates and details of the analysis, statistical significance and precision cannot be assessed. General statistical concepts explain what such results would mean, but they cannot substitute for results absent from the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, but it does not report a statistical analysis plan, a hierarchy of outcomes, or a multiplicity adjustment. Multiplicity arises when several outcomes, timepoints, regions, or hypotheses are tested: the more opportunities there are to declare a finding, the greater the chance of a false-positive result if each test is treated in isolation. That general concern does not establish that multiple hypothesis tests were performed in this study. The registry lists zero analyses, and no analysis results are reported.

The primary endpoint is identified as SUV in gm/ml with a timeframe of 3 hours. The outcome description refers to a dynamic scan and scans at 90- and 120-minutes post-injection. The registry does not explain whether separate values for each timepoint were treated as distinct outcomes, combined, or analyzed using a repeated-measures method. Any specific handling would be speculation.

The record says all participants completed their scheduled scans. It does not provide a detailed account of missing SUV measurements, data exclusions, or how missing outcome values were handled. It also does not state whether all enrolled participants were included in an analysis population or whether any other population definitions were used. Those items are not reported in the registry record. Completion of scheduled scans is useful context, but it is not a substitute for outcome-level missing-data reporting.

The statistical plan, interim analysis procedures, and missing-data assumptions are not reported in the registry record. Consequently, the risk of selective reporting and the sensitivity of results to missing data cannot be evaluated from the posted information.

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 reports safety figures for the EXPLORER PET/CT Imaging group. Serious adverse events affected 0 participants, with 20 listed as at risk. Other adverse events affected 0 participants, also with 20 listed as at risk. Deaths are reported as 0. These are the posted counts for this group.

These figures should be read as registry-reported event counts, not as proof that the procedure has no risks. The record does not provide detailed event definitions, a narrative of event monitoring, or information about the observation period for these safety counts. It also does not report a comparator group, so these figures cannot be used to make a comparative safety estimate.

The registry separately states that all participants completed their scheduled scans. That procedural statement does not add detail about how adverse events were assessed or whether all possible events were captured. The posted safety information is therefore limited to the event counts and at-risk figures recorded for the imaging group. It should not be expanded into claims about unreported events or broader safety in other populations.

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

This study's stated contribution is preliminary imaging information from healthy volunteers from racial/ethnic minority populations scanned using EXPLORER PET/CT. It identifies a continuous primary outcome, SUV in gm/ml, and describes the scan schedule used to collect total-body FDG perfusion and early biodistribution information. The record also reports that the study is completed and that participants completed their scheduled scans.

Those design details do not reveal the numerical SUV findings. The registry does not report the primary outcome mean or standard deviation, or any analyses. Consequently, the actual uptake values, their variation, and their statistical precision cannot be described. The study's stated purpose should not be mistaken for an observed finding.

The single-group design also sets a clear boundary on interpretation. Without a comparator, the record cannot establish a difference between EXPLORER and another scanner or protocol. It does not report a treatment comparison or clinical outcome. An imaging measurement can characterize radiotracer uptake, but a measured SUV alone does not establish a health benefit or a clinical consequence.

The cohort is described as healthy individuals from racial/ethnic minority populations. The registry does not provide additional detail about the characteristics of participants or the population's representativeness. The findings, if numerical results were available, would need to be interpreted in the context of the enrolled cohort and the study procedures rather than assumed to apply to other populations.

In statistical terms, this is a descriptive pilot with an outcome definition but without posted outcome estimates. Its record can inform readers about what the investigators set out to measure and the broad imaging schedule. It cannot answer how large or variable the observed SUV measurements were, whether differences across scan times were present, or how precise any estimate might be. Those conclusions require results not reported in the registry record.

13. Why This Trial Matters Statistically

This study is statistically notable for asking a measurement-focused question in a population described as healthy individuals from racial/ethnic minority populations. The stated aim is to collect preliminary data on total-body FDG perfusion and early biodistribution using EXPLORER PET/CT. In an imaging pilot, careful description of what is measured, when it is measured, and how variation is summarized is important for later scientific work.

The record defines the primary outcome as SUV in gm/ml, reported using a mean and standard deviation. This makes clear that the intended result is a continuous measurement summary rather than a clinical event comparison. The specified scan timepoints also make the measurement context relevant: values collected at different times may represent different stages of tracer distribution. The registry does not report how these repeated measurements were analyzed, so readers should not infer a particular model.

The single-group design underscores the distinction between describing a cohort and estimating a comparative effect. It can support characterization of measurements in the enrolled participants, but a control group would be needed for a direct between-group comparison. The record appropriately presents the study as a pilot, while its lack of posted numerical endpoint results limits what can be learned from the registry entry itself.

Statistically, the key lesson is that an outcome definition and a completed status do not supply the estimate. Without the observed mean, standard deviation, or an analysis, neither magnitude nor precision can be judged. This distinction matters when interpreting imaging studies: the methodological purpose may be clear even when the registry record does not provide results needed to evaluate the measurement findings.

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 main limitation for statistical interpretation is that the registry record does not report numerical results for the primary endpoint. Although it specifies SUV in gm/ml and a mean with standard deviation, neither summary is posted. The record lists zero analyses, so no inferential result or estimate of precision is available for interpretation.

The study is registered as single-group, with allocation listed as NA and masking as none. There is no comparator group for a direct comparison. This limits conclusions to the descriptive aim of the study and prevents assessment of differences attributable to a comparator condition. The registry does not report a statistical analysis plan, sample-size justification, or interim analysis procedures.

The endpoint description refers to scans at multiple timepoints, but the record does not explain how repeated observations were handled statistically, whether values were summarized by timepoint, or whether measurements were combined. Nor does it report region-level results or a detailed definition of the measurement aggregation. These details matter for understanding the unit of analysis and the dependence among measurements from the same participant.

The record says all participants completed scheduled scans, but it does not report a detailed missing-data account, exclusions, or the population used in each analysis. The arm description is truncated after its reference to a further time after injection, limiting the procedural information available there. The population's characteristics beyond the stated healthy-volunteer description are not reported in the registry record. Together, these omissions constrain reproducibility and the scope of any interpretation based on the registry entry.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: EXPLORER PET/CT: Evaluation of Healthy Individuals From Racial/Ethnic Minority Populations — NCT04812080.
• Registry record last updated 2026-03-11; status last verified 2023-04.
• Results first posted 2023-02-15.
• 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

NCT04812080 is a completed, single-group imaging study sponsored by the University of California, Davis. It enrolled 20 healthy volunteers from racial/ethnic minority populations to collect preliminary data using EXPLORER PET/CT. The primary outcome is SUV in gm/ml, described as a mean and standard deviation over a timeframe of 3 hours.

The registry lists a start date of 2021-08-18 and a primary completion date of 2021-11-08. Participants completed scheduled scans, including a dynamic scan and scans at 90- and 120-minutes post-injection. The record lists two outcome measures and zero analyses.

Numerical primary outcome estimates and statistical analyses are not reported in the registry record. The available information therefore describes the study's objective, design, imaging procedure, and endpoint, but does not permit assessment of the observed SUV values or their precision.