(261 days)
Velacur is intended to provide estimates of tissue stiffness generated from shear wave speed measurements (40-70 Hz), ultrasound attenuation and Velacur Determined Fat Fraction (VDFF). The Velacur Determined Fat Fraction combines ultrasound attenuation and backscatter coefficient measurements. The device is indicated to non-invasively determine liver tissue stiffness, attenuation, and Velacur Determined Fat Fraction. VDFF is not intended to be used in pediatric patients. These are meant to be used in conjunction with other clinical indicators in order to aid in clinical management of patients with liver diseases, including hepatic steatosis.
The device is intended to be used in a clinical setting and by trained medical professionals.
Velacur is a portable device intended to non-invasively measure the stiffness and attenuation of the liver via measurement of liver tissue shear modulus and ultrasound attenuation. This is done by measuring the wavelength or wave speed of mechanically created shear waves within the orqan of the patient. Attenuation is measured directly via the loss in power of the ultrasound beam.
The device is designed to be used at the point of care, in clinics and hospitals. The device is used by a medical profession, an employee of the clinic/hospital. The activation unit is placed under the patient, while lying supine on an exam bed. The activation unit vibrates at frequencies 40, 50, and 60 Hz causing shear waves within the liver of the patient. The ultrasound transducer is placed on the patient's skin, over the intercostal space, and is used to take volumetric scans of the liver while shear waves are occurring. The device includes two algorithms designed to help users detect good quality shear waves and identify liver tissue. From the scan data, the device calculates tissue stiffness and attenuation.
Minor hardware and software changes were made to the organ guide (cleared in K223287) was also extended to add more optional overlays on top of the liver overlay to help with optimizing the scan and training users to obtain adequate images. The significant change is the addition of a new output measure for Velacur, an ultrasound derived fat fraction (VDFF).
Here's a breakdown of the acceptance criteria and study details for the Velacur device, as described in the provided FDA 510(k) summary:
1. Table of Acceptance Criteria and Reported Device Performance
The document describes two separate machine learning algorithms: the Velacur Determined Fat Fraction (VDFF) algorithm, the Organ Guide Extension, and the Wave Quality Guide. Each has its own acceptance criteria and performance metrics.
| Feature/Algorithm | Acceptance Criteria | Reported Device Performance |
|---|---|---|
| Velacur Determined Fat Fraction (VDFF) | ||
| Correlation (VDFF vs. MRI-PDFF) | Not explicitly stated an "acceptance criterion" value, but implied to be strong based on predicate device testing. | 0.85 [0.77-0.91] (correlation coefficient [95% CI] in validation cohort) |
| AUC for 5% Steatosis Detection | Not explicitly stated an "acceptance criterion" value. | 0.97 [0.89-0.99] (AUC [95% CI] for detection of 5% steatosis) |
| Organ Guide Extension | ||
| Dice Coefficient | > 0.7 | Not explicitly stated the exact achieved value, but implies met acceptance criteria. |
| Pixel Accuracy | > 80% | Not explicitly stated the exact achieved value, but implies met acceptance criteria. |
| Wave Quality Guide | ||
| Dice Coefficient | > 0.7 | Not explicitly stated the exact achieved value, but implies met acceptance criteria. |
| Sensitivity | > 80% | Not explicitly stated the exact achieved value, but implies met acceptance criteria. |
| Specificity | > 80% | Not explicitly stated the exact achieved value, but implies met acceptance criteria. |
2. Sample Size Used for the Test Set and Data Provenance
-
Velacur Determined Fat Fraction (VDFF):
- Test Set Sample Size: 70 new patients
- Data Provenance: From 3 separate sites (with different Velacur operators). Implied to be prospective, as it's separate from the training data. The document states "Data was collected from sites across the US and Canada" for training, and "Evaluation data was collected... from separate patients, sites and collected by different users than the data used for training in order to ensure data independence," suggesting a similar geographical distribution for the test set. Retrospective/prospective not explicitly stated for this particular validation cohort, but the nature of MRI scans for ground truth implies it would be collected alongside the Velacur scans.
-
Organ Guide Extension:
- Test Set Sample Size: More than 800 images from 21 patients.
- Data Provenance: "Evaluation data was collected from volunteers and patients with non-alcoholic fatty liver disease and non-alcoholic steatohepatitis. All patients were recruited from hepatology clinics." Data was collected from sites across the US and Canada (implied to be similar for evaluation as for training). Data for evaluation was explicitly stated to be from "separate patients, sites and collected by different users than the data used for training," indicating an independent, possibly prospective collection for evaluation.
-
Wave Quality Guide:
- Test Set Sample Size: More than 4,000 images from 36 patients.
- Data Provenance: "Evaluation data was collected from volunteers and patients with non-alcoholic fatty liver disease and non-alcoholic steatohepatitis. All patients were recruited from hepatology clinics." Data was collected from sites across the US and Canada (implied to be similar for evaluation as for training). Data for evaluation was explicitly stated to be from "separate patients, sites and collected by different users than the data used for training," indicating an independent, possibly prospective collection for evaluation.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
-
Velacur Determined Fat Fraction (VDFF):
- Number of Experts: Not specified.
- Qualifications of Experts: Not specified. The MRI scans were "assessed to create the final measurement," implying expert interpretation without explicitly stating the number or qualifications.
-
Organ Guide Extension:
- Number of Experts: Not specified.
- Qualifications of Experts: "experts in the field of sonography and/or ultrasound elastography." No specific experience level (e.g., years) is provided.
-
Wave Quality Guide:
- Number of Experts: Not specified.
- Qualifications of Experts: "experts in the field of ultrasound elastography." No specific experience level (e.g., years) is provided.
4. Adjudication Method for the Test Set
The document does not explicitly describe an adjudication method (such as 2+1 or 3+1) for establishing ground truth for any of the algorithms. It generally states that ground truth was established by experts or through MRI-PDFF assessment, implying a single assessment per case or a consensus without detailing the process.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study comparing human readers with and without AI assistance was not reported in this document. The studies focus on the standalone performance of the AI algorithms.
6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done
Yes, standalone performance studies were done for all three components:
- Velacur Determined Fat Fraction (VDFF): The reported correlation coefficient and AUC are measures of the algorithm's direct performance against a ground truth (MRI-PDFF).
- Organ Guide Extension: The Dice Coefficient and pixel accuracy measure the algorithm's ability to segment organs directly.
- Wave Quality Guide: The Dice Coefficient, sensitivity, and specificity measure the algorithm's direct ability to identify good quality waves.
7. The Type of Ground Truth Used
- Velacur Determined Fat Fraction (VDFF): MRI Proton Density Fat Fraction (MRI-PDFF). This is considered a highly accurate quantitative measure for liver fat.
- Organ Guide Extension: Manual image segmentation by experts.
- Wave Quality Guide: Manual image segmentation by experts.
8. The Sample Size for the Training Set
- Velacur Determined Fat Fraction (VDFF): 112 patients from 4 sites (used for parameter fitting/training).
- Organ Guide Extension: More than 5,000 patient images.
- Wave Quality Guide: More than 15,000 patient images from 100+ patients.
9. How the Ground Truth for the Training Set Was Established
- Velacur Determined Fat Fraction (VDFF): MRI-PDFF scans were assessed to create the final measurement.
- Organ Guide Extension: Manual image segmentation by experts in the field of sonography and/or ultrasound elastography.
- Wave Quality Guide: Manual image segmentation by experts in the field of ultrasound elastography.
§ 892.1560 Ultrasonic pulsed echo imaging system.
(a)
Identification. An ultrasonic pulsed echo imaging system is a device intended to project a pulsed sound beam into body tissue to determine the depth or location of the tissue interfaces and to measure the duration of an acoustic pulse from the transmitter to the tissue interface and back to the receiver. This generic type of device may include signal analysis and display equipment, patient and equipment supports, component parts, and accessories.(b)
Classification. Class II (special controls). A biopsy needle guide kit intended for use with an ultrasonic pulsed echo imaging system only is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 892.9.