Search Results

VirtuOst uses data from computed tomography scans to estimate bone mineral density, bone strength, and a load-to-strength ratio. This information can be used by a physician to assess fracture risk, identify osteoporosis, and monitor therapy. For pediatric patients, VirtuOst provides these estimates without any classifications and should be used only when the benefit of obtaining these estimates outweighs the risk of radiation.

VirtuOst is a software-only medical device that analyzes data in computed tomography (CT) scans to measure bone mineral density (BMD), bone strength, and a load-to-strength ratio at the proximal femur and vertebral body. BMD is measured from both a 2D projection (in g/cm2) and a volumetric scan reconstruction (in mg/cm³) of the CT scan. VirtuOst measurements can be used by a physician to identify osteoporosis, assess fracture risk, and monitor therapy. The VirtuOst analysis is performed on previously physician-acquired image data and is unrelated to acquisition equipment and clinical workstations.

1. Table of Acceptance Criteria and Reported Device Performance

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

• Hip Areal BMD Equivalence:
  • Test Set Size: 324 women and men (overall). Specifically, 244 women and 80 men.
  • Data Provenance: Not explicitly stated, but implies clinical data. Retrospective or prospective is not specified.
• Phantomless Calibration:
  • Development of reference data for visceral fat attenuation: 268 patients and a custom torso phantom scanned on 31 and 35 different CT scanners respectively.
  • Comparison of fat/air phantomless calibration vs. phantom calibration: 40 independent patient CT scans.
  • Data Provenance: Not explicitly stated, but implies clinical data from various CT manufacturers (GE Healthcare, Siemens Medical Solutions, Philips Healthcare, Toshiba International) at various settings (80-140 kVp). Retrospective or prospective is not specified.
• CT-to-DXA Areal BMD Conversion for Hip:
  • Test Set Size: 200 subjects scanned on both CT and DXA.
  • Data Provenance: Not explicitly stated, but implies clinical data. Retrospective or prospective is not specified.
• Slice Spacing Adjustment for Femurs:
  • Development of adjustments: Pairs of CT images (unspecified number).
  • Observational study: 2,783 women and men (1,306 with hip fracture). This was a case-cohort study design.
  • Data Provenance: Not explicitly stated, but implies clinical data. The observational study implies retrospective data.

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

The document does not describe the use of human experts to establish ground truth for the test sets. Instead, it relies on:

• Clinical reference standards: FDA-cleared DXA devices for hip areal BMD equivalence.
• External calibration phantoms: For validating phantomless calibration.
• Outcomes data: Hip fracture prediction in an observational study for slice spacing adjustment.
• Regression analysis and statistical comparison: For quantitative metrics.

4. Adjudication Method for the Test Set

Not applicable, as expert adjudication was not used to establish ground truth. Ground truth was based on objective measurements from clinical reference standards (DXA, external phantoms) or clinical outcomes.

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

No MRMC comparative effectiveness study involving human readers with and without AI assistance was mentioned. The study focused on the equivalence of the device's measurements to established clinical standards (DXA, phantom) and its ability to predict outcomes, rather than human reader performance improvement.

6. Standalone (Algorithm Only) Performance Study

Yes, the studies presented primarily demonstrate the standalone performance of the VirtuOst algorithm.

• The comparison of hip areal BMD measurements to DXA devices is a standalone assessment.
• The phantomless calibration validation compares the algorithm's output to a known standard (external phantom).
• The CT-to-DXA conversion study assesses the algorithm's ability to produce DXA-equivalent T- and Z-scores.
• The slice spacing adjustment validation and the observational study on hip fracture prediction also assess the algorithm's standalone performance in providing clinically relevant measurements.

7. Type of Ground Truth Used

The ground truth used was a combination of:

• Clinical reference standards: Measurements from FDA-cleared DXA devices for hip areal BMD.
• Physical standards: External calibration phantoms for validating phantomless calibration.
• Outcomes data: Hip fracture occurrence in a case-cohort study for evaluating the slice spacing adjustment and overall clinical utility.
• Regression analysis and statistical comparison: Used to define the relationship between the device's measurements and the chosen ground truths.

8. Sample Size for the Training Set

The document does not explicitly state the sample sizes used for training the VirtuOst algorithm. The information provided relates to testing and validation of the modified device.

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

The document does not provide details on how the ground truth for the training set was established. The studies described are primarily focused on the validation of the modified device's performance against established benchmarks and clinical data, rather than the initial development and training of the core algorithms. It is implied that the predicate device (K113725) was developed and trained prior to this submission, and this submission focuses on demonstrating that modifications have not negatively impacted safety or effectiveness.

Ask a specific question about this device

Virtu Ost VFA uses sagittal sections from a spine-containing CT scan, with or without contrast enhancement, to visualize and measure vertebral deformities, classify the type and grade of any existing vertebral fracture, and from this identify patients at high risk of a future osteoporosis-related fracture. This information can be interpreted by a physician to diagnose existing vertebral fractures and to manage patients for osteoporosis.

VirtuOst Vertebral Fracture Assessment (VFA) software is used to perform vertebral morphometry and is an integrated component of VirtuOst (K113725). VirtuOst VFA accepts as input a sagittal section of a vertebral body, obtained from a spine-containing computed tomography (CT) scan, and provides semi-automated, interactive tools with which the user can perform six-point quantitative vertebral morphometry according to well-established guidelines. The process can be repeated for multiple vertebral bodies. For each vertebral body analyzed, the quantitative vertebral morphometry algorithm locates three points each along the superior and inferior endplate on a sagittal section through the vertebra, typically a mid-sagittal section. The user verifies or modifies point placement. Based on these six morphometry points, anterior, posterior and middle vertebral heights are measured. Percent deformities are calculated from these heights and are then compared against well-established criteria for vertebral deformities typical of osteoporosis-related vertebral fracture in order to classify types and grades of any existing osteoporosis-related vertebral fracture, from which a patient can be classified as being at high risk of a future osteoporosis-related fracture. The VFA algorithm can be applied to any complete vertebral body captured in the CT scan, and the scan can be contrast-enhanced or not. Consistent with the recommended use of the well-established fracture-classification criteria, deformity types and fracture grades and fracture-risk classifications are only reported for vertebral levels T4 through L4. A report is generated containing these results, along with images of the sagittal sections from which the measurements were acquired. A physician then interprets the report to make any medical diagnoses or treatment decisions.

Here's a breakdown of the acceptance criteria and the study details for the VirtuOst Vertebral Fracture Assessment device, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document doesn't explicitly state quantitative acceptance criteria in percentages or thresholds in a dedicated section. However, it implicitly uses agreement and precision metrics compared to manual measurements and a predicate device as evidence of acceptable performance for market clearance.

Summary of Device Performance: The study concludes that VirtuOst VFA is highly accurate, and its precision is substantially equivalent to that of the predicate device. Precision errors are small and do not significantly affect fracture determination or grading, even with varying CT slice thicknesses (up to 3mm) and the use of IV contrast enhancement.

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

• Sample Size for Test Set: n=40 women and men (35 with potential fractures, 5 without).
• Data Provenance:
  • Country of Origin: Not explicitly stated, but the study used "computed tomography scans acquired as part of standard care for 7000 women and men age 65 and older."
  • Retrospective or Prospective: The selection of patients from an existing database of 7000 CT scans, where scans were within a 90-day period (implying existing sets of scans), indicates a retrospective study design for data collection.

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

• Number of Experts: Not explicitly stated. The text mentions "vertebral heights were also manually measured from high resolution (0.5 mm) printouts of midsagittal sections of the L1 vertebra from each CT scan." It does not specify who performed these manual measurements or their qualifications. It simply refers to these "manual measurements" as the reference standard.

4. Adjudication Method for the Test Set

• Adjudication Method: Not explicitly described. The manual measurements are presented as a reference standard, but the process by which multiple experts might have agreed upon these measurements (e.g., 2+1, 3+1) is not detailed. The study mentions two operators performing VFA, but this is for repeatability analysis of the device, not for establishing ground truth directly.

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

• Was an MRMC study done?: No. The study conducted was primarily a precision and accuracy study, comparing the device's measurements against manual measurements and assessing intra- and inter-operator variability. It did not involve comparing human readers' diagnostic performance with AI assistance versus without AI assistance.

• Effect size of human reader improvement with AI vs. without AI assistance: Not applicable, as no MRMC comparative effectiveness study was performed in this manner.

6. Standalone Performance Study

• Was a standalone study done?: Yes. The study investigated the "Accuracy of VirtuOst VFA relative to the manual measurements" and its repeatability (intra-operator, interoperator, short-term, combined precision), as well as the impact of slice thickness and contrast enhancement on the device's performance. This directly assesses the algorithm's performance independent of real-time human interpretation loop changes in diagnostic workflow.

7. Type of Ground Truth Used

• Ground Truth Type: "Manual measurements" of vertebral heights from high-resolution printouts of midsagittal sections using six-point morphometry methods. This constitutes an expert-derived or reference standard measurement based on established definitions of vertebral fracture. The specific "experts" who performed these manual measurements are not explicitly qualified in the text.

8. Sample Size for the Training Set

• Sample Size for Training Set: Not specified. The document focuses on the validation study and does not provide details about the training data used to develop the VirtuOst VFA algorithm.

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

• How Ground Truth for Training Set Was Established: Not specified in the provided text.

Ask a specific question about this device

VirtuOst uses data from computed tomography scans to estimate bone mineral density, bone strength, and a load-to-strength ratio. This information can be used by a physician to assess fracture risk, identify osteoporosis, and monitor therapy. For pediatric patients, VirtuOst provides these estimates without any classifications and should be used only when the benefit of obtaining these estimates outweighs the risk of radiation.

VirtuOst is a stand-alone software package that analyzes data in computed tomography (CT) scans to measure bone mineral density (BMD), bone strength, and a load-tostrength ratio at the proximal femur and vertebral body. BMD is measured from both a 2D projection (in g/cm2) and a volumetric scan reconstruction (in mg/cm2) of the CT scan. VirtuOst measurements can be used by a physician to identify osteoporosis, assess fracture risk, and monitor therapy.

The provided text describes the VirtuOst device (K113725), which analyzes CT scans to estimate bone mineral density, bone strength, and a load-to-strength ratio for assessing fracture risk and monitoring therapy.

Here's a breakdown of the requested information based on the provided document:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined "acceptance criteria" in a quantitative, pass/fail format typical for medical device regulatory submissions. Instead, it focuses on demonstrating substantial equivalence to predicate devices. The "performance" is described in terms of equivalence and comparative effectiveness.

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

The document states:

• "Clinical studies demonstrated the substantial equivalence for measurements of bone mineral density between VirtuOst and predicate densitometers which used either DXA or computed tomography scans as input."
• "Clinical repositioning studies demonstrated that the precision of outcomes from VirtuOst and predicate devices are equivalent."
• "Results from a number of clinical fracture surveillance studies demonstrated that fracture risk assessment by VirtuOst estimates of whole-bone strength and the load-to-strength ratio, are at least as good as fracture risk assessment by DXA and QCT estimates of BMD."
• "Strength of the proximal femur and vertebral body estimated using VirtuOst are statistically equivalent to strength as measured by direct mechanical testing in cadaver experiments."

The exact sample sizes for these "clinical studies," "clinical repositioning studies," "clinical fracture surveillance studies," and "cadaver experiments" are not specified in the provided 510(k) summary. The data provenance (country of origin, retrospective/prospective) is also not explicitly stated.

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

This information is not provided in the document. The mention is of "clinical studies" and "clinical fracture surveillance studies" which would imply clinical diagnoses, but the specifics of expert involvement or their qualifications for establishing ground truth are absent.

4. Adjudication method for the test set

The adjudication method (e.g., 2+1, 3+1, none) for the test set is not specified in the provided document.

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

The document does not mention an MRMC comparative effectiveness study where human readers use the AI device with and without assistance. The studies described focus on the device's standalone performance compared to existing methods or predicate devices, rather than human-in-the-loop performance improvement.

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

Yes, a standalone study was done. The entire submission describes the performance of the VirtuOst software as a standalone analytical tool. Its measurements are compared to predicate devices or direct mechanical testing, supporting its function without explicitly detailing a human-in-the-loop component for its primary performance evaluation. The "Summary of Performance Data" directly refers to the device's outputs for BMD, bone strength, and fracture risk assessment.

7. The type of ground truth used

Based on the descriptions:

• For bone mineral density (BMD): The ground truth appears to be established by measurements from predicate densitometers (DXA and QCT scans). This is a comparative ground truth based on established clinical measurement tools.
• For bone strength: The ground truth was direct mechanical testing in cadaver experiments.
• For fracture risk assessment: The ground truth appears to be based on clinical fracture surveillance studies, implying actual fracture outcomes or follow-up diagnoses. This is an outcomes data or clinical diagnosis type of ground truth.

8. The sample size for the training set

The document does not specify the sample size for the training set. It only discusses performance evaluation on what can be inferred as "test" or "validation" sets through clinical and non-clinical studies.

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

The document does not provide information on how the ground truth for the training set was established, as it does not detail the training phase or data.

Ask a specific question about this device