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MSKai is an image identification, post-processing, measurement, and reporting software tool that provides qualitative viewing and quantitative spine measurements from previously-acquired T2 weighted DICOM lumbar spine Magnetic Resonance Imaging (MRI) images for users' review, evaluation and analysis. It provides the following functionality to assist users in identifying, observing, measuring and reporting measurements:

Anatomy segmentation;
Anatomy labeling;
Anatomy measurement; and
Export of measurement results to a qualitative and quantitative report for user's evaluation, amendment and authorization

MSKai does not serve as a diagnostic device by providing or recommending any type of medical diagnosis or treatment. MSKai simply provides users the ability to access objective and repeatable identification, segmentation, measurement and reported measurements of the Lumbar spine. The user is responsible for the indications of preferences and settings, confirming the software-generated measurements, and reviewing, confirming and approving draft reports based on their medical training.

The device is intended to be used only by physicians, radiologist, hospitals and other medical institutions. Only T2 weighted DICOM images of MRI acquired from lumbar spine exams of patients aged 18 and above are acceptable input. MSKai does not support DICOM images of patients that are pregnant, have post-operational complications, tumors, infections, or complex hardware.

Device Description

MSKai is a medical device (software) for inspecting and evaluating T2-weighted magnetic resonance imaging (MRI) of the lumbar spine. The software is an imaging interpretation tool that assists radiologists and neuro/ortho spine surgeons ("users") to identify and measure lumbar spine features in medical images and document their interpretations in a report. The segmentation and measurements are classified using "alerts" based on rule-based algorithms. The user also identifies and classifies any other observations that the software may not annotate.

AI/ML Overview

Here's a breakdown of the acceptance criteria and the study proving the MSKai device meets those criteria, based on the provided FDA 510(k) clearance letter:

MSKai Device Performance Study Summary

The MSKai device is an image identification, post-processing, measurement, and reporting software tool for T2-weighted lumbar spine MRI images. A standalone software performance assessment study was conducted to demonstrate its accuracy in segmentation and measurement, meeting pre-defined acceptance criteria.

Table of Acceptance Criteria and Reported Device Performance:

A. Segmentation Performance (Mean Dice Coefficient - MDC)

Anatomy Segmentation	View	Acceptance Criteria (MDC Limit)	Reported Device Performance (Mean Dice Coefficient)	95% Confidence Interval (CI)	Met Criteria?
Vertebral Body (L1)	Sagittal	0.8	0.968	0.92-0.98	Yes
Vertebral Body (L2)	Sagittal	0.8	0.977	0.93-0.98	Yes
Vertebral Body (L3)	Sagittal	0.8	0.981	0.94-0.99	Yes
Vertebral Body (L4)	Sagittal	0.8	0.963	0.92-0.98	Yes
Vertebral Body (L5)	Sagittal	0.8	0.985	0.91-0.98	Yes
Vertebral Body (S1)	Sagittal	0.8	0.945	0.93-0.99	Yes
L5/S1 Disc	Sagittal	0.8	0.993	0.91-0.99	Yes
L4/L5 Disc	Sagittal	0.8	0.991	0.93-0.99	Yes
L3/L4 Disc	Sagittal	0.8	0.992	0.93-0.99	Yes
L2/L3 Disc	Sagittal	0.8	0.989	0.91-0.99	Yes
L1/L2 Disc	Sagittal	0.8	0.986	0.94-0.99	Yes
Cord Canal	Sagittal	0.8	0.983	0.93-0.99	Yes
Axial Disc	Axial	0.8	0.984	0.89-0.97	Yes
Vertebral Body	Axial	0.8	0.991	0.93-0.99	Yes
Dural Sac	Axial	0.8	0.978	0.90-0.98	Yes
Nerve Root	Axial	0.8	0.952	0.90-0.95	Yes
Posterior Arch	Axial	0.8	0.911	0.90-0.96	Yes

All reported Mean Dice Coefficients (MDC) met or exceeded the acceptance criterion of 0.8.

B. Measurement Performance (Mean Absolute Error - MAE)

Structural Measurements	View	Acceptance Criteria (MAE Limit)	Reported Device Performance (Mean Absolute Error)	95% Confidence Interval (CI)	Met Criteria?
Protruding Disc Material (L5/S1)	Sagittal	2mm	1.19mm	1.11 -1.68mm	Yes
Protruding Disc Material (L4/L5)	Sagittal	2mm	1.22mm	1.12 -1.71mm	Yes
Protruding Disc Material (L3/L4)	Sagittal	2mm	1.23mm	1.14 -1.65mm	Yes
Protruding Disc Material (L2/L3)	Sagittal	2mm	1.19mm	1.07 -1.61mm	Yes
Protruding Disc Material (L1/L2)	Sagittal	2mm	1.21mm	1.11 -1.63mm	Yes
Intervertebral Angle (L5/S1)	Sagittal	6°	2.6°	1.58 - 2.45°	Yes
Intervertebral Angle (L4/L5)	Sagittal	6°	2.7°	1.61 - 2.59°	Yes
Intervertebral Angle (L3/L4)	Sagittal	6°	2.7°	1.57 - 2.54°	Yes
Intervertebral Angle (L2/L3)	Sagittal	6°	2.9°	1.64 - 2.62°	Yes
Intervertebral Angle (L1/L2)	Sagittal	6°	2.4°	1.66 - 2.48°	Yes
Vertebral Body Height (Anterior) (L1)	Sagittal	2mm	0.66mm	0.62 -0.91mm	Yes
Vertebral Body Height (Anterior) (L2)	Sagittal	2mm	0.68mm	0.61 -0.88mm	Yes
Vertebral Body Height (Anterior) (L3)	Sagittal	2mm	0.69mm	0.61 -0.93mm	Yes
Vertebral Body Height (Anterior) (L4)	Sagittal	2mm	0.64mm	0.58 -0.91mm	Yes
Vertebral Body Height (Anterior) (L5)	Sagittal	2mm	0.67mm	0.61 -0.91mm	Yes
Vertebral Body Height (Midline) (L1)	Sagittal	2mm	0.94mm	0.62 -0.87mm	Yes
Vertebral Body Height (Midline) (L2)	Sagittal	2mm	0.93mm	0.54 -1.03mm	Yes
Vertebral Body Height (Midline) (L3)	Sagittal	2mm	0.96mm	0.61 -1.01mm	Yes
Vertebral Body Height (Midline) (L4)	Sagittal	2mm	0.97mm	0.57 -1.13mm	Yes
Vertebral Body Height (Midline) (L5)	Sagittal	2mm	0.94mm	0.57 -0.99mm	Yes
Vertebral Body Height (Posterior) (L1)	Sagittal	2mm	0.92mm	0.67 -0.99mm	Yes
Vertebral Body Height (Posterior) (L2)	Sagittal	2mm	0.93mm	0.61 -1.01mm	Yes
Vertebral Body Height (Posterior) (L3)	Sagittal	2mm	0.91mm	0.68 -0.99mm	Yes
Vertebral Body Height (Posterior) (L4)	Sagittal	2mm	0.92mm	0.71 -1.06mm	Yes
Vertebral Body Height (Posterior) (L5)	Sagittal	2mm	0.93mm	0.68 -1.09mm	Yes
Disc Height (Anterior) (L5/S1)	Sagittal	2mm	0.91mm	0.67 -0.99mm	Yes
Disc Height (Anterior) (L4/L5)	Sagittal	2mm	0.90mm	0.57 -1.06mm	Yes
Disc Height (Anterior) (L3/L4)	Sagittal	2mm	0.87mm	0.62 -1.03mm	Yes
Disc Height (Anterior) (L2/L3)	Sagittal	2mm	0.89mm	0.78 -1.06mm	Yes
Disc Height (Anterior) (L1/L2)	Sagittal	2mm	0.93mm	0.71 -1.23mm	Yes
Disc Height (Midline) (L5/S1)	Sagittal	2mm	0.93mm	0.73 -1.12mm	Yes
Disc Height (Midline) (L4/L5)	Sagittal	2mm	0.90mm	0.68 -1.01mm	Yes
Disc Height (Midline) (L3/L4)	Sagittal	2mm	0.89mm	0.71 -1.13mm	Yes
Disc Height (Midline) (L2/L3)	Sagittal	2mm	0.91mm	0.64 -1.03mm	Yes
Disc Height (Midline) (L1/L2)	Sagittal	2mm	0.92mm	0.69 -1.11mm	Yes
Disc Height (Posterior) (L5/S1)	Sagittal	2mm	0.87mm	0.58 -1.03mm	Yes
Disc Height (Posterior) (L4/L5)	Sagittal	2mm	0.93mm	0.67 -0.99mm	Yes
Disc Height (Posterior) (L3/L4)	Sagittal	2mm	0.87mm	0.66 -1.07mm	Yes
Disc Height (Posterior) (L2/L3)	Sagittal	2mm	0.93mm	0.72 -1.21mm	Yes
Disc Height (Posterior) (L1/L2)	Sagittal	2mm	0.89mm	0.58 -0.91mm	Yes
Anterio-Lithesis (L5/S1)	Sagittal	2mm	1.04mm	0.81 -1.43mm	Yes
Anterio-Lithesis (L4/L5)	Sagittal	2mm	1.02mm	0.77 -1.52mm	Yes
Anterio-Lithesis (L3/L4)	Sagittal	2mm	1.05mm	0.88 -1.61mm	Yes
Anterio-Lithesis(L2/L3)	Sagittal	2mm	1.07mm	0.84 -1.43mm	Yes
Anterio-Lithesis (L1/L2)	Sagittal	2mm	1.02mm	0.79 -1.33mm	Yes
Retro-Lithesis (L5/S1)	Sagittal	2mm	1.07mm	0.82 -1.51mm	Yes
Retro-Lithesis (L4/L5)	Sagittal	2mm	1.049mm	0.78 -1.42mm	Yes
Retro-Lithesis (L3/L4)	Sagittal	2mm	1.01mm	0.81 -1.29mm	Yes
Retro-Lithesis (L2/L3)	Sagittal	2mm	1.05mm	0.77 -1.34mm	Yes
Retro-Lithesis (L1/L2)	Sagittal	2mm	1.08mm	0.83 -1.27mm	Yes
Lordotic Angle	Sagittal	6°	2.99°	2.01 - 3.62°	Yes
Protruding Disc Material	Axial	2mm	0.97 mm	0.72 -1.42mm	Yes
Dural Sac Diameter	Axial	2mm	1.3 mm	0.87 -1.39mm	Yes

All reported Mean Absolute Errors (MAE) were below the acceptance criterion of 2mm or 6°.

Sample Size and Data Provenance:
- Test set sample size: 238 MR image studies (from 238 patients).
- Data Provenance: Images were collected from five sites across the U.S.
- Timeframe: Not explicitly stated whether retrospective or prospective, but generally clinical performance studies for 510(k) clearances use retrospective data. The description "collected from five sites across the U.S." doesn't specify if it was specifically collected for this study, implying it could be retrospective.
Number of Experts and Qualifications for Ground Truth:
- Total number of experts for ground truth establishment (initial curation for training/testing): 5 experts.
- Qualifications of these experts: 3 neurosurgeons, 1 interventional radiologist, and 1 PhD in Biomechanics.
- Number of experts for measurement analysis in the testing dataset (independent group): 4 separate and independent experts.
- Qualifications of these specific measurement experts: 2 neurosurgeons, 2 radiologists.
Adjudication Method for the Test Set:
- The document implies a consensus method for ground truth, stating "Ground truth data, curated by five experts in a two-phase process, underpins model training." and for the independent testing dataset, "being measured by an independent group of 4 experts."
- For the testing dataset measurements, it says "Measurement analysis was performed by 4 separate and independent experts." It also mentions "Inter-ratter reliabilities were conducted in the experts who perform the training/testing measurements."
- However, it does not explicitly state a formal adjudication method like "2+1" or "3+1" (where agreement by a majority or third reader is required to resolve discrepancies). The language "curated by five experts" and "measured by an independent group of 4 experts" suggests a consensus or multiple-read approach, but the specific rule for resolving disagreements is not detailed.
Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:
- No MRMC study was done. The document explicitly states: "No human clinical study was conducted to support the pre-market clearance." This means there is no data provided on how much human readers improve with AI vs. without AI assistance. The study described is a standalone performance study.
Standalone Performance:
- Yes, a standalone (algorithm only without human-in-the-loop performance) study was done. The study's title is "Standalone Software Performance Study" and it states, "the MSKai software outputs without any editing by a radiologist" were compared to ground truth.
Type of Ground Truth Used:
- Expert Consensus: The ground truth was established by human experts (3 neurosurgeons, 1 interventional radiologist, and 1 PhD in Biomechanics) who curated and measured anatomical segmentations and structures.
Sample Size for the Training Set:
- Training Data: The document mentions "Three blind independent data sets were used to train, test and measure within the model." It specifically states the "Ground Truth dataset: 255 patient images." While this dataset was used for "ground truth development" for model training, the exact number of images specifically used only for the training phase versus those used for internal testing/validation during development is not distinctly broken out beyond the general "Ground Truth dataset: 255 patient images" being used to "underpin model training."
How Ground Truth for the Training Set Was Established:
- The ground truth for the training set (referred to as the "Ground Truth dataset") was "curated by five experts in a two-phase process." These experts were 3 neurosurgeons, 1 interventional radiologist, and 1 PhD in Biomechanics. This involved establishing the accurate segmentations and measurements that the algorithm was trained to reproduce.

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