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The Hologic QDR Explorer is a fan beam X-Ray Bone Densitometer indicated for (1) the measurement of bone mineral content (BMC) and the estimation of bone mineral density (BMD), (2) comparison of measurements to reference databases, (3) the estimation of fracture risk, (4) body composition analysis, and (5) measurement of periprosthetic BMD

The Hologic QDR Explorer is a fan beam X-Ray Bone Densitometer indicated for (1) the measurement of bone mineral content (BMC) and the estimation of bone mineral density (BMD), (2) comparison of measurements to reference databases, (3) the estimation of fracture risk, (4) body composition analysis, and (5) measurement of periproshtetic BMD.

This submission (K033224) is a Special 510(k) for the Hologic QDR Explorer X-Ray Bone Densitometer. Special 510(k)s are used for modifications to a device already cleared by the FDA, where the modification does not affect the intended use or fundamental scientific technology of the device. Therefore, a comprehensive de-novo study proving the device meets acceptance criteria is typically not performed, as the substantial equivalence is largely based on the predicate device's performance.

Instead, the submission focuses on demonstrating that the modified device (QDR Explorer) is substantially equivalent to its predicate (QDR-3000 K943505 and Hologic Discovery Package for QDR X-Ray Bone Densitometers K023398) and continues to meet the safety and effectiveness standards established for bone densitometers. The information provided outlines changes in specifications rather than reporting specific performance metrics against acceptance criteria from a new clinical study.

Here's an analysis of the provided information in the context of your request:

1. Table of Acceptance Criteria and Reported Device Performance

The provided text does not include a table of acceptance criteria and reported device performance against those criteria as would be found in a primary clinical study for a new device. Instead, it presents a comparison table between the predicate device (QDR-3000) and the proposed device (QDR Explorer) to demonstrate substantial equivalence.

The "acceptance criteria" for a Special 510(k) often revolve around demonstrating that the modified device performs comparably to the predicate device and that the changes do not introduce new safety or effectiveness concerns. For this specific device, the "performance" aspects highlighted are primarily changes in hardware specifications.

Here's a reinterpretation of the provided table, focusing on the differences and implied acceptance of parity:

2. Sample Size for the Test Set and Data Provenance

This Special 510(k) primarily relies on the established performance of the predicate device (QDR-3000) and previous clearances for its software and additional functionalities (e.g., K023398 for Discovery software, K983028 for fracture risk, K963363 for reference databases, K961787 for body composition, K002711 for periprosthetic BMD).

There is no dedicated sample size for a "test set" reported for the QDR Explorer in this submission that would involve new clinical data collection. The submission emphasizes substantial equivalence documentation of specification changes, largely in hardware and software versions. If any testing was done to confirm the functionality of the new detector, source-to-detector distance, or new software running on new hardware, it would likely be in the form of engineering verification and validation tests, not a clinical trial with a "test set" in the traditional sense of evaluating diagnostic accuracy.

The data provenance for the predicate device's original clearance would have been specific to that submission (K943505). Similarly, the data for the cleared software (K023398) and other functionalities (K983028, K963363, K961787, K002711) would be tied to their respective 510(k) submissions. This document itself doesn't provide new clinical data.

3. Number of Experts and Qualifications for Ground Truth

Given that this is a Special 510(k) based on substantial equivalence to an already cleared predicate and the focus is on hardware/software updates, there is no mention of experts establishing a new ground truth for a test set. The fundamental "ground truth" for bone densitometry is typically established through clinical correlation studies comparing BMD measurements to, for example, fracture rates, or to other validated methods like quantitative computed tomography (QCT) or direct bone biopsy (though less common for routine densitometry validation). These would have been part of the predicate device's original clearance.

4. Adjudication Method for the Test Set

As there is no new clinical "test set" described in this submission, there is no adjudication method mentioned.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

Bone densitometers are typically quantitative measurement devices. Their performance is evaluated based on precision (reproducibility of measurements) and accuracy (how well measurements correlate with actual bone mineral content/density). They are not usually evaluated through MRMC studies that assess human reader interpretation of images, as is common for diagnostic imaging AI. Therefore, no MRMC study was performed or reported here, and thus no effect size of AI assistance on human readers.

6. Standalone Algorithm Performance Study

The Hologic QDR Explorer is a physical medical device (an X-ray bone densitometer), not an AI algorithm. Its performance is the direct output of the system (BMC, BMD values). Therefore, the concept of a "standalone algorithm only without human-in-the-loop performance" doesn't directly apply. The device is the "algorithm" in a sense, as it processes the X-ray data to produce the measurements. The "performance" is the accuracy and precision of those measurements, which would have been established for the predicate device.

7. Type of Ground Truth Used

The "ground truth" for bone densitometry, in general, relies on:

• Clinical Outcomes Data: Correlation of BMD measurements with actual fracture incidence or risk.
• Pathology/Histology: In some research contexts, direct measurement of bone mineral content from biopsy.
• Expert Consensus/Reference Standards: Usage of anthropomorphic phantoms with known bone mineral densities, and comparisons to established reference populations for Z-scores and T-scores.

For this Special 510(k), the ground truth essentially lies in the established clinical utility and accuracy of the predicate device (QDR-3000) and the prior clearances for its functionalities and software. The QDR Explorer, through its substantial equivalence claim, implicitly leverages this existing ground truth rather than generating new primary ground truth data.

8. Sample Size for the Training Set

There is no "training set" mentioned in the context of this device. Bone densitometers are primarily physics-based measurement systems, not machine learning algorithms that require a training set in the typical sense. Data used for developing or validating reference databases (e.g., K963363) would involve large epidemiological studies, but this submission doesn't detail those.

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

As there is no "training set" for an AI algorithm, this question is not applicable to the information provided for this device. The development of reference databases, if considered a form of "training data," would involve large-scale population studies where age, sex, ethnicity, and direct BMD measurements are collected to establish statistical norms. These methods would have been detailed in the original 510(k)s for those specific functionalities (e.g., K963363).

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