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The intended use of the CTXA Hip Extence Data accessory for the CTXA Hip Bone Mineral Densitometry module is to provide a context for the clinical interpretation of a patient's proximal femur BMD estimates. T-scores are calculated relative to a US normal female Caucasian reference population age 20-39 years, and Z-scores are calculated relative to a US normal female Caucasian reference population age 20-79 years. The use of a reference data set and the interpretation of parameters derived by the CTXA Hip module when comparing patient-specific BMD estimates to the installed and selected reference data set is at the discretion of the physician.

The CTXA Hip Extenced Reference Data is an accessory to the CTXA Hip Bone Mineral Densitometer. The CTXA Hip Extended Reference Data is used within the CTXA Hip module to calculate T-scores and percent young normal for any patient, and Z-scores for patients age 20-80 for BMD estimates made using the CTXA Hip module.

The provided text describes a 510(k) premarket notification for the "CTXA Hip Extended Reference Data" device, which is an accessory to the CTXA Hip Bone Mineral Densitometer. The purpose of this accessory is to provide a broader reference dataset for calculating T-scores and Z-scores for Bone Mineral Density (BMD) estimates from the CTXA Hip module.

1. A table of acceptance criteria and the reported device performance:

2. Sample size used for the test set and the data provenance:

The document does not explicitly state a specific sample size used for a test set in the context of a validation study for the "CTXA Hip Extended Reference Data" accessory itself.

Instead, the substantiation for substantial equivalence appears to rely on:

• Logical deduction: BMD estimates are "identical" to the predicate, implying the core measurement accuracy is unchanged.
• Quantification of T-score differences: A "0.1-0.2 T-score unit" difference, which is then deemed "not significant clinically."
• Reference Population: The reference data set used for T-scores and Z-scores is described as a "US normal female Caucasian reference population." The specific size, collection methodology (retrospective/prospective), or exact provenance (e.g., specific study) of this reference population is not detailed in the provided text.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

The document does not mention the use of experts to establish ground truth for a test set in the context of the device's performance evaluation. The device's function is a calculation based on predefined reference data, not a diagnostic interpretation that typically requires expert consensus for ground truth.

4. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

Not applicable. The document does not describe an adjudication method for a test set, as its evaluation focuses on the consistency of calculations and the clinical insignificance of minor differences, rather than a diagnostic accuracy study where adjudication is common.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

Not applicable. The device, "CTXA Hip Extended Reference Data," is an accessory for a bone densitometer providing reference data for score calculation. It does not involve AI assistance to human readers or a multi-reader multi-case study. It simply provides a new reference population for existing BMD measurements.

6. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

The device's core function is standalone in the sense that it provides a calculation of T-scores and Z-scores based on a reference database. The "algorithm" (i.e., the method of calculating these scores against the reference data) is performed without human intervention in the calculation itself. However, the interpretation of these scores "is at the discretion of the physician," meaning the overall diagnostic process remains human-in-the-loop. The document focuses on the accuracy and clinical insignificance of differences in these calculated scores.

7. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

The "ground truth" in this context refers to the reference population data against which patient BMD estimates are compared to calculate T and Z scores. The document describes this as a "US normal female Caucasian reference population age 20-39 years" for T-scores and "US normal female Caucasian reference population age 20-79 years" for Z-scores. The specific methodology for establishing this "normal" reference population (e.g., how subjects were selected, what criteria defined "normal," how BMD was measured for this database) is not detailed in the provided text.

8. The sample size for the training set:

The document does not mention a training set in the context of machine learning or AI. The "reference data" would be analogous to a training set here, but its sample size is not specified.

9. How the ground truth for the training set was established:

The document does not detail how the "US normal female Caucasian reference population" (which serves as the "ground truth" or reference for the device's calculations) was established. It is simply referred to as a "reference population."

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The CTXA Hip Bone Mineral Densitometer is intended to estimate bone mineral content (BMC) and bone mineral density (BMD) in the proximal femur. The BMD estimates can be compared with CTXA Hip-derived reference data. T-scores are calculated with respect to CTXA Hip young normal female reference data, and the T-scores can be used by the physician as an aid in determining fracture risk.

The CTXA Hip Bone Mineral Densitometer (CTXA Hip) is a software package intended for estimation of bone mineral content (BMC), in grams, and bone mineral density (BMD), in glem', of the proximal femur. The CTXA Hip uses quantitative computed tomography (QCT) methods to derive bone mass and bone density estimates from 3D CT image data sets. The CTXA Hip is intended to be used with compatible, whole-body CT scanners and with compatible CT calibration phantoms. BMD estimates are derived in units of g/cm2 equivalent K2HPO4 density.

Here's a breakdown of the acceptance criteria and study details for the CTXA Hip Bone Mineral Densitometer, based on the provided 510(k) summary:

1. Table of Acceptance Criteria and Reported Device Performance

Note: The 510(k) summary does not explicitly state numerical acceptance criteria for many of these metrics. Instead, it reports the device performance and implicitly suggests these values are acceptable by concluding substantial equivalence to predicate devices.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size for Test Set: Not explicitly stated. The summary mentions "clinical studies" for both in vivo precision and correlation with predicate devices, and "a clinical study" for collecting reference data. No specific numbers are provided for patient cohorts in these studies.
• Data Provenance:
  • In vitro phantom studies: Location not specified, but likely laboratory-based.
  • Clinical studies (in vivo precision & correlation): Not explicitly stated, but the reference data collection mentions "young normal US Caucasian females," implying US origin for at least that part of the clinical data.
  • Retrospective or Prospective: Not explicitly stated for any of the clinical studies.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications of Those Experts

This information is not provided in the summary. The studies described are focused on device precision and correlation with other devices, not on diagnostic accuracy against a human-established ground truth in a direct sense.

4. Adjudication Method for the Test Set

This information is not provided in the summary. Given the nature of the device (automated bone mineral density estimation), direct human adjudication of results in the traditional sense (e.g., consensus on image interpretation) is not applicable in the same way it would be for a diagnostic AI device. The comparison is against established device outputs (DXA) or precision metrics.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not reported. The device is a "standalone" algorithm for quantitative measurement, not an AI-assisted diagnostic tool for human readers.

• Effect size of human readers improve with AI vs without AI assistance: Not applicable, as no MRMC study was performed with human readers.

6. If a Standalone Study Was Done

Yes, standalone performance was assessed. The entire submission describes the performance of the CTXA Hip software itself (an algorithm) in various scenarios:

• In vitro phantom studies: Assessed precision and bias independently.
• Clinical studies for in vivo precision: Assessed the device's consistency over time when applied to human subjects.
• Clinical studies comparing BMD results with predicate DXA devices: Evaluated the device's output against established measurement systems.

7. The Type of Ground Truth Used

• For in vitro phantom studies: The ground truth was based on the known physical properties and densities of the phantoms used, expressed as equivalent K2HPO4 mineral density.
• For in vivo precision studies: The "ground truth" was the device's own consistent measurement of BMD in the same individuals over time, aiming for low variability.
• For correlation studies with predicate devices: The "ground truth" was the BMD measurements obtained from the predicate DXA devices (Hologic QDR 1000 and QDR 4500), which are established methods for bone densitometry.

8. The Sample Size for the Training Set

This information is not provided in the summary. The CTXA Hip is described as a software package using QCT methods to derive estimates, but the details of any machine learning or specific algorithm training are not discussed. It's likely based on established QCT principles rather than a distinct "training set" in the modern AI sense.

9. How the Ground Truth for the Training Set Was Established

Since a "training set" in the typical machine learning sense is not explicitly mentioned and the device appears to be based on established QCT principles rather than being a trained AI model, the method for establishing "ground truth for the training set" is not applicable/provided. The summary focuses on validation of the methodology and its output against existing standards.

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