(60 days)
LiverMultiScan (LMSv4) is indicated for use as a magnetic device software application for noninvasive liver evaluation that enables the generation, display and review of 2D magnetic resonance medical image data and pixel maps for MR relaxation times.
LiverMultiScan (LMSv4) is designed to utilize DICOM 3.0 compliant magnetic resonance image datasets, acquired from compatible MR systems, to display the internal structure of the abdomen including the liver. Other physical parameters derived from the images may also be produced.
LiverMultiScan (LMSv4) provides a number of tools, such as automated liver segmentation and region of interest (ROI) placements, to be used for the assessment of selected regions of an image. Quantitative assessments of selected regions include the determination of triglyceride fat fraction in the liver (PDFF), T2* and iron-corrected T1 (cT1) measurements. T2* may be optionally computed using the DIXON or LMS MOST methods.
These images and the physical parameters derived from the images, when interpreted by a trained clinician, yield information that may assist in diagnosis.
LiverMultiScan is a standalone software device. The purpose of the LiverMultiScan device is to assist a trained operator with the evaluation of information from Magnetic Resonance (MR) images from a single time-point (a patient visit). LiverMultiScan is a post-processing software device, a trained operator uses tools such as automatic liver segmentation and region of interest placement upon previously acquired MR images, from which a summary report is generated. The summary report is subsequently sent to an interpreting clinician at the acquiring site.
LiverMultiScan is not intended to replace the established procedures for the assessment of a patient's liver health by an interpreting clinician, providing many opportunities for competent human intervention in the interpretation of images and information displayed.
The metrics are intended to be used as an additional diagnostic input to provide information to clinicians as part of a wider diagnostic process. It is expected that in the normal course of liver disease diagnosis, patients with clinical symptoms or risk factors which may indicate liver disease. The interpreting clinician needs to take into consideration the device's limitations and accuracy during clinical interpretation.
Liver function tests, blood tests, ultrasound scanning as well as liver biopsy are all expected to be used at the discretion of a qualified clinician in addition to information obtained from the use of LiverMultiScan metrics. The purpose of LiverMultiScan metrics is to provide imaging information to assist in characterizing tissue in the liver, in addition to existing methods for obtaining information relating to the liver. LiverMultiScan metrics are not intended to replace any existing diagnostic source of information but can be used to identify patients who may benefit most from further evaluation, including biopsy.
Information gathered through existing diagnostic tests and clinical evaluation of the patient, as well as information obtained from LiverMultiScan metrics, may contribute to a diagnostic decision.
LiverMultiScan is not a computer-aided diagnostic device and can only present imaging information which must be interpreted by a qualified clinician. LiverMultiScan is an aid to diagnosis and treatment decisions remains the responsibility of the clinician.
In consequence, the product is considered to have no adverse effect on health since the results represent only a part of the information that the user will utilize for final interpretation. In this regard, LiverMultiScan presents a moderate level of concern with respect to patient safety.
Here's a detailed breakdown of the acceptance criteria and the study proving the device meets them, based on the provided text:
1. Table of Acceptance Criteria and Reported Device Performance
The acceptance criteria are implicitly defined by the performance test results demonstrating acceptable levels of accuracy, repeatability, and reproducibility. The document states that the observed variations were "well within the prescribed acceptance criteria," but the numerical values for the criteria themselves are not explicitly listed. Instead, the reported performance values are provided.
| Metric (Type) | Performance Aspect | Acceptance Criteria (Implicit) | Reported Device Performance (LMSv4) |
|---|---|---|---|
| cT1 (Bench) | Accuracy (1.5T) | Within acceptable range (not explicitly stated, but negative bias in line with literature is acceptable) | -189.5 to -35.11 ms (Consistent with literature-reported underestimation of ground truth T1 using MOLLI techniques) |
| cT1 (Bench) | Accuracy (3T) | Within acceptable range (not explicitly stated, but negative bias in line with literature is acceptable) | -187.0 to -19.12 ms (Consistent with literature-reported underestimation of ground truth T1 using MOLLI techniques) |
| T2* (Bench) | Accuracy (1.5T) | Accurate over expected physiological range of values (not explicitly stated numerically) | -0.68 to 0.64 ms (Accurate over the expected physiological range of values) |
| T2* (Bench) | Accuracy (3T) | Accurate over expected physiological range of values (not explicitly stated numerically) | -0.30 to 0.39 ms (Accurate over the expected physiological range of values) |
| IDEAL PDFF (Bench) | Accuracy (1.5T) | Accurate over expected physiological range of values (not explicitly stated numerically) | -3.80 to 6.08% (Accurate over the expected physiological range of values) |
| IDEAL PDFF (Bench) | Accuracy (3T) | Accurate over expected physiological range of values (not explicitly stated numerically) | -1.39 to 5.58% (Accurate over the expected physiological range of values) |
| cT1 (ROI) (Clinical) | Repeatability | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -43.25 to 26.77 ms (Highly repeatable) |
| cT1 (Segmentation) (Clinical) | Repeatability | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -40.75 to 25.02 ms (Highly repeatable) |
| T2* (DIXON) (Clinical) | Repeatability | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -5.21 to 6.01 ms (Highly repeatable) |
| T2* (MOST) (Clinical) | Repeatability | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -3.17 to 3.25 ms (Highly repeatable) |
| IDEAL PDFF (ROI) (Clinical) | Repeatability | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -1.48 to 1.42% (Highly repeatable) |
| IDEAL PDFF (Segmentation) (Clinical) | Repeatability | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -1.31 to 1.34% (Highly repeatable) |
| cT1 (ROI) (Clinical) | Reproducibility | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -103 to 91.8 ms (Reproducible between scanners and field strengths) |
| cT1 (Segmentation) (Clinical) | Reproducibility | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -102.3 to 93.69 ms (Reproducible between scanners and field strengths) |
| T2* (DIXON) (Clinical) | Reproducibility | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -1.74 to 0.35 ms (Reproducible between scanners and field strengths) |
| T2* (MOST) (Clinical) | Reproducibility | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -2.40 to 2.15 ms (Reproducible between scanners and field strengths) |
| IDEAL PDFF (ROI) (Clinical) | Reproducibility | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -2.88 to 2.53% (Reproducible between scanners and field strengths) |
| IDEAL PDFF (Segmentation) (Clinical) | Reproducibility | Well within prescribed acceptance criteria (Limits of Agreement - not numerically specified) | -2.94 to 2.53% (Reproducible between scanners and field strengths) |
| Operator Variability | Repeatability/Reproducibility | Well within prescribed acceptance criteria (not numerically specified) | Variation introduced by operator measurements (both ROI and segmentation) is well within the prescribed acceptance criteria. |
2. Sample Size Used for the Test Set and Data Provenance
- Sample Size for Test Set: The document does not explicitly state the numerical sample size for the test set. For the bench testing, it mentions "purpose-built phantoms" and for clinical testing, "in-vivo acquired volunteer data." The number of phantoms or volunteers is not specified.
- Data Provenance:
- Bench Testing: Data was acquired from "purpose-built phantoms." The country of origin is not specified, but the applicant (Perspectum Ltd) is based in the UK.
- Clinical Testing: "in-vivo acquired volunteer data" from "volunteers participating in the performance testing were representative of the intended patient population." The country of origin for these volunteers is not specified. The study appears to be prospective for the gathered "volunteer data" in the sense that data was acquired for the purpose of testing, but the details are sparse.
3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not mention the use of experts to establish ground truth for the test set.
- Bench Testing: Ground truth for phantom accuracy was based on the "gold standard" to which the LMSv4 values were compared. This "gold standard" is implied to be the known physical properties or reference measurements of the phantoms.
- Clinical Testing: The clinical performance relates to repeatability and reproducibility of the device's measurements themselves, not against a human-established ground truth. Operator variability was assessed, implying trained operators were involved, but their qualifications and number are not detailed beyond "trained internal Perspectum operators."
4. Adjudication Method for the Test Set
No adjudication method for the test set is mentioned. The performance testing focuses on the device's intrinsic accuracy, repeatability, and reproducibility, rather than agreement with human interpretation that would typically require adjudication.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No MRMC comparative effectiveness study was done. The document states: "No clinical investigations or studies were conducted during performance testing of LMSv4." The device is positioned as an "aid to diagnosis" and "not intended to replace any existing diagnostic source of information," suggesting its role is as a tool rather than a standalone diagnostic.
6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study
Yes, a standalone performance study was clearly done. The "Performance Testing - Bench" section directly assesses the "accuracy and precision of device measurements" using phantoms. The "Performance Testing - Clinical" section assesses the "precision of LMSv4 measurements" (repeatability and reproducibility) using volunteer data. While operator variability was assessed, the core measures are of the algorithm's output. The device itself is described as a "post-processing software device" where an "operator uses tools such as automatic liver segmentation and region of interest placement," implying the algorithm performs the quantification and the operator interfaces with it.
7. Type of Ground Truth Used
- Bench Testing: The ground truth for accuracy was established using a "gold standard" derived from the "purpose-built phantoms" that contained vials with known relaxation times.
- Clinical Testing: For repeatability and reproducibility, the "ground truth" is essentially the device's own consistent measurement across repeated scans, different scanners/field strengths, and different operators. It is not externally validated against pathology or clinical outcomes in this document.
8. Sample Size for the Training Set
The document does not provide any information regarding the sample size for the training set. It focuses solely on the performance testing of the device.
9. How the Ground Truth for the Training Set Was Established
The document does not provide any information regarding the training set or how its ground truth was established, as it does not describe the development or training of the LMSv4 algorithm. The emphasis is on proving substantial equivalence to a predicate device through performance benchmarking.
§ 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.