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SyMRI is a post-processing software medical device intended for use in visualization of soft tissue. SyMRI analyzes input data from MR imaging systems. SyMRI utilizes data from supported MR sequences to generate parametric maps of R1, R2 relaxation rates, and proton density (PD).

SyMRI is intended for automatic labeling, visualization and volumetric quantification of segmentable brain tissues from a set of MR images. Brain tissue volumes are determined based on modeling of parametric maps from SyMRI.

SyMRI can also generate multiple image contrasts from the parametric maps. SyMRI enables post-acquisition image contrast adjustment.

SyMRI is indicated for head imaging.

When interpreted by a trained physician, output from SyMRI can provide information useful in determining diagnosis. SyMRI 2D is intended to be used in combination with at least one other, conventional MR acquisition (e.g. T2-FLAIR). T1W and T2W images from SyMRI 3D may replace conventional MR images in a clinical setting when interpreting together with a conventional 3D T2W FLAIR image.

Device Description

SyMRI works by post-processing a multi-delay, multi-echo acquisition into parametric maps. The acquisition is either a multi-slice 2D approach (M2D-MDME), consisting of 4 delays with a short and a long echo time each (8 images per slice), or a 3D approach (3D-QALAS) consisting of 4 delays with a short echo and 1 delay with a long echo time (5 images per slice).

The parametric maps are R1, R2 relaxation rates, and proton density (PD). The inverse relaxation parameters, T1 relaxation time (1/R1), and T2 relaxation time (1/R2) are also provided as parametric maps.

SyMRI also enables the users to obtain volumetric information in the head, including white matter (WM), gray matter (GM), cerebrospinal fluid (CSF), Myelin correlated (MyC) partial volume, brain parenchyma (BP) and intracranial cavity (IC). This is accomplished by using tissue definitions based on the parametric maps. The tissue definitions provide tissue partial volume, or tissue fraction, per voxel. SyMRI also provides image processing tools to extract the values of the parametric maps, and tissue partial volume, per individual voxel, per region of interest, or the entire imaging volume.

The parametric maps can be visualized as contrast weighted MR images, such as T1, T2, PD, and Inversion Recovery (IR) weighted images (including T1-FLAIR, STIR, Double IR, and PSIR weighted images).

The parametric maps can be visualized as contrast weighted MR images from SyMRI 3D may replace conventional MR images in a clinical setting when interpreting together with a conventional 3D T2W FLAIR image.

SyMRI calculates the pixel signal intensity as a function of R1, R2, PD, and desired MR scanner settings, such as echo time (TE), repetition time (TR), and inversion delay time (TI). A number of default settings for TE, TR, and TI are provided, but the user has the ability to change the contrast of the images. SyMRI generates all the different image contrasts from the same parametric maps, derived from the same acquisition. This leads to enhanced image slice registration, owing to the absence of inter-acquisition patient movement. SyMRI provides the user the ability to change the contrast of the images after the acquisition. This is performed by adjusting the TE, TR, and/or TI parameters post-acquisition, to generate the specific contrast desired.

SyMRI is intended to be used on data produced by any of the following acquisition sequences:

. MDME sequence data from GE MAGiC
MDME sequence data from Philips SyntAc
. MDME sequence data from Siemens TSE_MDME
3D-QALAS sequence data from Philips 3DsyntAc

AI/ML Overview

This document describes the acceptance criteria and study proving the device meets them for SyMRI.

1. Table of Acceptance Criteria and Reported Device Performance

Performance Metric	Acceptance Criteria	Reported Device Performance
Quantitative Accuracy & Precision (R1, R2, PD)	Equivalent to predicate device. Correspondence with reference values (gold standard phantoms).	R1, R2, and PD measurements show correspondence with reference values (inversion recovery for R1, CPMG multi-echo for R2, heavy water phantoms for PD, and NIST/ISMRM Model 130 phantom). The subject device met the same predefined acceptance criteria as the predicate device, demonstrating equivalence in accuracy and precision for quantification when compared to gold standards.
Segmentation Accuracy & Precision	Equivalent to predicate device.	The verification results demonstrate that the subject device SyMRI meets the same pre-defined performance criteria as the predicate.
Non-inferiority of Synthetic 3D Images (Diagnostic Performance)	Non-inferiority in sensitivity and specificity for detecting any pathology compared to conventional 3D images. Non-inferiority in diagnostic accuracy of radiological finding class compared to conventional 3D images.	Synthetic 3D images were non-inferior in terms of sensitivity and specificity in detecting any pathology, as well as non-inferior in diagnostic accuracy of radiological finding class, compared to equivalent conventional MR images over a wide range of brain pathologies.
Legibility of Anatomical Structures	High legibility of anatomical structures.	All images (synthetic and conventional) had a very high legibility of anatomical structures.
Artifact Prevalence	Lower prevalence of artifacts in synthetic images compared to conventional images. No novel artifacts.	Synthetic images had lower prevalence of artifacts compared to the conventional MR images. No novel artifacts were reported for synthetic MR images.
Image Quality Score	Higher image quality score for synthetic images compared to conventional images.	Synthetic images had slightly higher image quality scores compared to conventional images for both T1W and T2W images.

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

Sample Size: 189 subjects
Data Provenance:
- Country of Origin: United States (6 institutes in the US)
- Study Type: Prospective, multi-reader clinical investigation.
- Subject characteristics: Patients with a wide range of different pathologies, and healthy controls. Both adults and pediatric patients were included.

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

The document does not explicitly state the number of experts used to establish a ground truth for the test set. However, it mentions that five experienced radiologists assessed the images in the clinical investigation. Their qualifications are described as "experienced radiologists."

4. Adjudication Method for the Test Set

The document does not explicitly state an adjudication method (e.g., 2+1, 3+1). It states that "Five experienced radiologists... assessed the images in two reading sessions with a four-week memory washout period in between." This suggests individual assessments rather than a consensus-based adjudication for primary readings, though further details on how discrepancies (if any) were handled are not provided.

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

Yes, a MRMC comparative effectiveness study was done. The study involved five experienced radiologists assessing images in two reading sessions.
Effect Size of Human Reader Improvement with AI vs. Without AI Assistance: This specific information (effect size of human readers improving with AI assistance vs. without) is not directly provided. The study focused on demonstrating the non-inferiority of synthetic 3D images (generated by the AI device, SyMRI) compared to conventional 3D images in terms of diagnostic performance (sensitivity, specificity, diagnostic accuracy). It also evaluated image quality and artifact prevalence of the synthetic images. It does not describe a scenario where human readers interpreted conventional images and then re-interpreted them with AI assistance to measure improvement. Instead, it compares the diagnostic utility of AI-generated images versus conventional images.

6. Standalone (Algorithm Only) Performance Study

Yes, a standalone performance assessment was conducted for the quantitative aspects of the device:

Accuracy of R1/R2/PD quantification: Evaluated compared to "gold standard inversion recovery (R1), CPMG multi-echo (R2), heavy water phantoms (PD) and standard system Model 130 NIST/ISMRM phantom." This demonstrates an algorithm-only accuracy assessment against established physical standards.
Segmentation Accuracy & Precision: Verified against pre-defined performance criteria similar to the predicate device. While not explicitly stated as "algorithm only," the context of "verification results" for quantification and segmentation usually refers to algorithmic performance.

7. Type of Ground Truth Used

For Quantitative Parameters (R1, R2, PD): Gold standard phantoms (inversion recovery, CPMG multi-echo, heavy water phantoms, NIST/ISMRM Model 130 phantom).
For Diagnostic Performance (Pathology Detection, Diagnostic Accuracy, Image Quality): The consensus or individual expert assessments of the five experienced radiologists after reviewing both synthetic and conventional images served as the reference for comparison, aiming to establish non-inferiority against conventional imaging. Although not explicitly called "ground truth," the conventional images and expert interpretations thereof served as the benchmark. The study compared the device-generated synthetic images to equivalent conventional MR images. It also mentions "radiological finding class," implying expert-derived classifications.

8. Sample Size for the Training Set

The document does not provide information on the sample size used for the training set of the SyMRI algorithm. It focuses on the validation study.

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 describe the training process for the algorithm. It primarily details the performance validation of the device.

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K Number

K233733

Device Name

SyMRI

Manufacturer

SyntheticMR AB (Publ)

Date Cleared

2024-03-26

(126 days)

Product Code

Regulation Number

Type

Panel

Reference & Predicate Devices

K203372

Intended Use

When interpreted by a trained physician, the parametric maps, tissue maps, and volumetrics from SyMRI can provide information useful in determining diagnosis. SyMRI is indicated for head imaging.

SyMRI can also generate multiple contrast weighted images from the parametric maps generated by post-processing data from M2D-MDME sequence. SyMRI enables post-acquisition image contrasts adjustments from acquisition using M2D-MDME sequence.

When M2D-MDME acquisition data is used as input to SyMRI the synthetic contrast weighted images can also provide information useful in determining diagnosis. SyMRI is intended to be used in combination with at least one other, conventional MR acquisition (e.g. T2-FLAIR).

Device Description

SyntheticMR's SyMRI is a Class II Magnetic resonance diagnostic device (Requlation # 892.1000) with product code LNH. The device has no components and/or accessories.

SyMRI enables the users to obtain volumetric information in the head, including white matter (WM), grey matter (GM), cerebrospinal fluid (CSF), Myelin correlated (MyC) partial volume, brain parenchyma (BP) and intracranial cavity (IC). This is accomplished by using tissue definitions based on the parametric maps. The tissue definitions provide tissue partial volume, or tissue fraction, per voxel. SyMRI also provides image processing tools to extract the values of the parametric maps, and tissue partial volume, per individual voxel, per region of interest, or the entire imaging volume.

The parametric maps can also be visualized as contrast weighted MR images, such as T1, T2, PD, and Inversion Recovery (IR) weighted images (including T1-FLAIR, T2-FLAIR, STIR, Double IR, and PSIR weighted images). SyMRI calculates the pixel signal intensity as a function of R1, R2, PD, and desired MR scanner settings, such as echo time (TE), repetition time (TR), and inversion delay time (TI). A number of default settings for TE, TR, and TI are provided, but the user has the ability to change the contrast of the images.

SyMRI generates all the different image contrasts from the same parametric maps, derived from the same acquisition. This leads to enhanced image slice registration, owing to the absence of interacquisition patient movement. SyMRI provides the user the ability to change the contrast of the images after the acquisition. This is performed by adjusting the TE, TR, and/or TI parameters postacquisition, to generate the specific contrast desired.

SyMRI is intended to be used to process data produced by any of the following acquisition sequences:

M2D-MDME sequence data from GE MAGiC ●
M2D-MDME sequence data from Philips SyntAc
. M2D-MDME sequence data from Siemens TSE MDME
3D-QALAS sequence data from Philips 3DSyntAc Only 3T .

SyMRI can also create contrast weighted images from 3D-QALAS but these are only available in the product for quality assurance purposes as a risk mitigation related artifacts that could affect quantification and segmentation, and should not be used for clinical purposes.

AI/ML Overview

Here's an analysis of the acceptance criteria and the study proving the device meets them, based on the provided text:

Acceptance Criteria and Device Performance

Acceptance Criteria Category	Acceptance Criteria (from text)	Reported Device Performance (from text)
Quantification Accuracy	Good correspondence with reference values for R1, R2, and PD measurements, meeting same predefined acceptance criteria as predicate.	"The R1, R2 and PD measurements show a good correspondence with the reference values, and the subject device met the same predefined acceptance criteria as the predicate device. It can be concluded that the accuracy and precision of SyMRI is good." (Comparison to gold standard inversion recovery (R1), CPMG multi-echo (R2), heavy water phantoms (PD) and standard system Model 130 NIST/ISMRM phantom.)
Quantification Precision	Good precision for R1, R2, and PD measurements, meeting same predefined acceptance criteria as predicate.	"The R1, R2 and PD measurements show a good correspondence with the reference values, and the subject device met the same predefined acceptance criteria as the predicate device. It can be concluded that the accuracy and precision of SyMRI is good."
Segmentation Precision	Within-subject standard deviation on scan-rescan (repeatability) for segmentation volumes should be acceptable.	"The precision of segmentation results was evaluated by scanning healthy volunteers multiple times and analyzing the difference in segmentation volumes. This is evaluated in terms of repeatability as within-subject standard deviation on the scan-rescan on the same model and field strength." (Results implied satisfactory based on overall conclusion of meeting predefined performance criteria.)
Volumetric Equivalence (3D-QALAS vs. M2D-MDME)	Segmentation fractions (BPF, MyCPF, WMF, GMF) from SyMRI using 2D and 3D acquisition methods must be statistically equivalent within a clinically determined equivalence margin on both mean difference and slope.	"The performance data show that segmentation fractions BPF, MyCPF, WMF and GMF from SyMRI using 2D or 3D are statistically equivalent within the clinically determined equivalence margin on both mean difference and slope between the two acquisition methods." (Bench test on 45 healthy volunteers.)

Study Details

Sample sizes used for the test set and the data provenance:
- Quantification Accuracy & Precision Test (Phantoms): The text mentions "gold standard inversion recovery (R1), CPMG multi-echo (R2), heavy water phantoms (PD) and standard system Model 130 NIST/ISMRM phantom." No specific number of phantoms or scans is provided.
- Segmentation Precision Test (Healthy Volunteers): "healthy volunteers scanned multiple times." No exact number of subjects or scans is explicitly stated for this particular test, though 45 healthy volunteers were used for the equivalence test.
- Volumetric Equivalence Test (3D-QALAS vs. M2D-MDME): 45 healthy volunteers.
- Data Provenance: Not explicitly stated, but given the mention of "healthy volunteers" and "bench test," it implies a prospective study. The country of origin is not specified.
Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- The document does not mention the use of experts to establish ground truth for the test set for quantification or segmentation accuracy/precision. Ground truth for quantification was based on "gold standard" physical measurements (e.g., phantoms) and for segmentation precision, it was based on within-subject variability, which doesn't typically require human expert ground truth review in the same way.
- For the volumetric equivalence study, the ground truth was a statistical comparison between two acquisition methods within the device itself, not against an external expert-derived ground truth.
Adjudication method for the test set:
- Not applicable as the ground truth establishment did not involve multiple human experts requiring adjudication.
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:
- No MRMC comparative effectiveness study was done, nor was there any evaluation of human reader improvement with AI assistance mentioned in the provided text. The study focuses on the technical performance of the device itself (quantification, segmentation, and equivalence between acquisition methods). The device is a "post-processing software medical device intended for use in visualization of soft tissue" and its interpretation is "When interpreted by a trained physician," implying human interpretation, but no study on the impact of the device on physician performance is detailed.
If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:
- Yes, the described performance data (Quantification Accuracy & Precision, Segmentation Precision, and Volumetric Equivalence) are all standalone performance evaluations of the SyMRI algorithm. These tests assess the device's technical output (parametric maps, segmentation, volumes) directly, without involving human interpretation as an outcome measure.
The type of ground truth used:
- Quantification: "Gold standard" physical measurements, specifically "inversion recovery (R1), CPMG multi-echo (R2), heavy water phantoms (PD) and standard system Model 130 NIST/ISMRM phantom." This represents a form of physical/reference standard ground truth.
- Segmentation Precision: Repeatability (scan-rescan variability) in healthy volunteers. This is an internal consistency/precision ground truth rather than an external anatomical ground truth.
- Volumetric Equivalence: A statistical comparison between the device's outputs from two different acquisition methods (M2D-MDME and 3D-QALAS). The M2D-MDME method effectively serves as a reference within the context of determining equivalence.
The sample size for the training set:
- The document does not provide information on the training set used for the SyMRI algorithm. The performance data section focuses solely on verification and validation (testing) and does not disclose details about the development or training phase of the software.
How the ground truth for the training set was established:
- Not provided, as information on the training set itself is absent from the text.

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