(87 days)
MR Elastography is a software option intended for use on Achieva and Ingenia 1.5T and 3.0T MR Systems for producing images representing tissue stiffness of the abdomen area such as liver and muscle. MR Elastography applies an MR acquisition sequence synchronized with an external source of vibration to produce images representing tissue stiffness (in kiloPascals, kPa). The stiffness image production technique also creates an overlay representing the reliability of the stiffness image production algorithm.
The MR Elastography feature consists of a specialized acquisition: a source of acoustic frequency vibration and means to impart that vibration to the scan subject: an image processing step to produce stiffness maps, confidence maps, and wave images; and an analysis tool to evaluate the parametric images created.
The acquisition is based on the Phase Contrast FFE sequence acquired while imparting a known frequency of vibration into the patient. A set of images with controlled phase differences between the acquisition and the mechanical oscillation is created by synchronizing the mechanical driver with the acquisition at different time delays. The vibration source and connecting equipment are provided by Resoundant Inc. as a complete set. Elasticity images are created from the image data generated by this acquisition strategy using an algorithm developed by Resoundant Inc. and The Mayo Clinic. In addition, wave images and confidence overlays are also produced to provide data quality assurance.
The Philips MR Elastography software option is intended for use on Achieva and Ingenia 1.5T and 3.0T MR Systems to produce images representing tissue stiffness of the abdomen area (e.g., liver and muscle). It utilizes an MR acquisition sequence synchronized with an external vibration source to generate stiffness images (in kiloPascals, kPa) and an overlay indicating the reliability of the stiffness image production algorithm.
The acceptance criteria for the device are not explicitly quantified with specific performance metrics in the provided document. Instead, the document describes the successful completion of verification activities to demonstrate functionality and substantial equivalence to predicate devices.
Here's an analysis of the provided information:
1. Table of Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance |
|---|---|
| Functionality with Achieva and Ingenia MR systems | MR Elastography has been verified to function with the Achieva and Ingenia MR systems. Sample images demonstrate the wave and elastogram outputs. All tests performed for MR Elastography were successful. |
| Production of repeatable results | Included confidence studies prove that MR Elastography produces repeatable results. |
| Differentiation between tissues of different stiffness | Included confidence studies prove that MR Elastography can reliably differentiate between tissues of different stiffness. |
| Clinical user needs met | The clinical user needs are tested as part of the validation testing. The clinical validation of MR Elastography is completed successfully. All clinical user needs have passed for Achieva and Ingenia 1.5T and 3T systems. |
| Safety and effectiveness | Nonclinical and clinical tests demonstrated that the device is safe and works according to its intended use. |
| Substantial equivalence to predicate devices | The acquisition, processing, and output images are substantially equivalent to GE MR-Touch (K083421) and Siemens MR Elastography (K121434). MR Elastography does not introduce new indications for use, nor does the use of the device result in any new potential hazard. |
2. Sample Size Used for the Test Set and Data Provenance
The document does not specify the sample size used for the test set. It mentions "sample images" and "confidence studies" but does not provide details on the number of subjects or images included in these tests. The data provenance is also not explicitly stated in terms of country of origin or whether the studies were retrospective or prospective.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications of Experts
This information is not provided in the document. The document mentions an "algorithm developed by Resoundant Inc. and The Mayo Clinic" and that the "MR Elastography software post-processing package was based on an estimation algorithm provided by The Mayo Clinic and Resoundant, Inc." but does not detail the specific involvement of experts in establishing ground truth for testing, nor their qualifications.
4. Adjudication Method for the Test Set
The adjudication method used for the test set is not described in the provided document.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done
No MRMC comparative effectiveness study is mentioned or referenced in the provided text. The document focuses on demonstrating substantial equivalence to predicate devices and fulfilling functionality and safety requirements.
6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
The document describes the "MR Elastography" feature as consisting of hardware and software elements, including an "image processing step to produce stiffness maps, confidence maps, and wave images" and an "analysis tool." The "confidence studies" seem to be related to the algorithm's performance in producing repeatable results and differentiating tissue stiffness, which implies a standalone evaluation of the algorithm's output. However, it's not explicitly stated as a formal "standalone" study to evaluate algorithmic performance against a definitive ground truth in a clinical context.
7. The Type of Ground Truth Used
The type of ground truth used is not explicitly specified. The document states that "confidence studies prove that MR Elastography produces repeatable results and can reliably differentiate between tissues of different stiffness," suggesting that some form of reference independent of the device was used to confirm stiffness differentiation, potentially phantoms with known stiffness or other established methods. However, the specific type (e.g., pathology, outcomes data) is not detailed.
8. The Sample Size for the Training Set
The document does not provide any information regarding the sample size used for the training set. It mentions that the algorithm was "developed by Resoundant Inc. and The Mayo Clinic" and that the software was developed "in conjunction with The Mayo Clinic and Resoundant, Inc.," but does not elaborate on the data used during development.
9. How the Ground Truth for the Training Set Was Established
This information is not provided in the document.
§ 892.1000 Magnetic resonance diagnostic device.
(a)
Identification. A magnetic resonance diagnostic device is intended for general diagnostic use to present images which reflect the spatial distribution and/or magnetic resonance spectra which reflect frequency and distribution of nuclei exhibiting nuclear magnetic resonance. Other physical parameters derived from the images and/or spectra may also be produced. The device includes hydrogen-1 (proton) imaging, sodium-23 imaging, hydrogen-1 spectroscopy, phosphorus-31 spectroscopy, and chemical shift imaging (preserving simultaneous frequency and spatial information).(b)
Classification. Class II (special controls). A magnetic resonance imaging disposable kit intended for use with a magnetic resonance diagnostic device only is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 892.9.