(71 days)
The intended use of the device here in question, i.e., the Imatron Ultrafast CT Scanner, remains unchanged from the intended use of prior predicate Imatron and other scanners. The Imatron Ultrafast CT Scanner is designed -- as are all similar devices -- to produce cross sectional images (i.e., thin slices) of the human anatomy. In this instance, such images are produced via helical (i.e., continuous volume or dynamic) or stationary (i.e., static) scanning. Imatron's device is -- as are some of the predicate devices -- also intended to be used for clinical situations requiring determination of specific quantitative information, such as the determination of calcium or other materials in bone, tumors, or organs.
The Imatron Ultrafast CT scanner is a scanning system which operates by directing a focused beam of electrons along tungsten target rings to produce X-rays which pass through the body at multiple angles as in conventional CT scanning systems. The Imatron Ultrafast CT scanner is capable of producing CT slices at rapid speeds since the data is produced by electronic rotation of the electron beam itself rather than the mechanical rotation of an X-ray tube as in conventional CT scanning systems. Currently, the Imatron Ultrafast CT scanner operating at its highest resolution mode has 864 single, contiguous X-ray detectors subtending an arc of 0.250 degrees each. The resulting 5% amplitude modulation transfer function (MTF) for high contrast objects at the center of the circle of reconstruction is 7 line pairs per centimeter (lp/cm).
The provided text describes a 510(k) submission for a design modification to the Imatron Ultrafast CT Scanner, specifically implementing a High Resolution Detector (HRD). The study focuses on demonstrating "substantial equivalence" to a predicate device rather than establishing new acceptance criteria for a novel device. Therefore, some information requested, particularly regarding acceptance criteria and separate performance metrics, is not explicitly detailed as would be for a new device submission.
Here's an analysis of the available information:
1. Table of Acceptance Criteria and Reported Device Performance
The submission doesn't present a formal table of "acceptance criteria" in the sense of predefined thresholds for clinical performance metrics (e.g., sensitivity, specificity). Instead, it focuses on demonstrating that the modified device's performance, specifically its image resolution, is improved and that the device remains "substantially equivalent" to its predicate.
| Criterion/Parameter (as described) | Predicate Device Performance | Modified Device (HRD) Performance | Acceptance (Implied) |
|---|---|---|---|
| Arc Subtended by Detectors | 0.250 degrees (864 single detectors) | 0.125 degrees (864 pairs of detectors) | Improved Resolution |
| 5% Amplitude MTF (High Contrast Objects, center of reconstruction) | 7 line pairs per centimeter (lp/cm) | 9.5 lp/cm | Improved Resolution (Superior to Predicate) |
| Dose Efficiency | Original system's | Retained (same as original) | Equivalent |
| Number of Data Acquisition Channels | Original system's | Retained (same as original) | Equivalent |
| Number of Samples | Original system's | Retained (same as original) | Equivalent |
| Safety, Effectiveness, Intended Use Impact | Not significantly impacted by other modifications | Not significantly impacted | Equivalent |
2. Sample Size Used for the Test Set and Data Provenance
- Test Set Sample Size: 12 human subjects.
- Data Provenance: Clinical performance testing with human volunteers was conducted "on site" (likely Imatron's facility) and was prospective, following IRB overview and informed consent. The country of origin is not explicitly stated but can be inferred as the USA given the FDA submission context.
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 study described is a "human volunteer testing" to show "substantial equivalence," not a diagnostic accuracy study requiring expert-derived ground truth for the device's output.
4. Adjudication Method for the Test Set
This information is not provided. As noted above, the study appears to be focused on demonstrating device functionality and equivalence, not a diagnostic accuracy study that would typically involve adjudication of device outputs against a ground truth.
5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was Done
No, an MRMC comparative effectiveness study was not done. The submission describes bench testing and human volunteer testing to demonstrate substantial equivalence of the device itself, not to evaluate reader performance with or without AI assistance. The device in question is a CT scanner, not an AI software.
6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done
Yes, in a sense. The "Non-clinical Performance" section describes extensive bench testing (~61 tests including product acceptance and release criteria, and phantom testing) carried out before human testing. This represents a standalone assessment of the device's physical and technical performance. The device itself is a scanner, not an AI algorithm, so the concept of an "algorithm only" performance would refer to its technical specifications.
7. The Type of Ground Truth Used
For the bench testing and phantom testing, the "ground truth" would be established by the physical characteristics of the phantoms and the expected technical performance measurements for a CT scanner (e.g., MTF calculations). For the human volunteer testing, the "ground truth" or reference standard for comparison is the performance characteristics of the predicate device, aiming to show that the modified device performs equivalently or better in terms of image quality and safety. There is no mention of pathology, outcomes data, or expert consensus in relation to diagnostic accuracy for clinical conditions.
8. The Sample Size for the Training Set
This information is not applicable and therefore not provided. The Imatron Ultrafast CT Scanner is a hardware device (a CT scanner), not a machine learning or AI-based algorithm that requires a "training set" in the context of AI development.
9. How the Ground Truth for the Training Set Was Established
This information is not applicable as there is no training set for a hardware device.
§ 892.1750 Computed tomography x-ray system.
(a)
Identification. A computed tomography x-ray system is a diagnostic x-ray system intended to produce cross-sectional images of the body by computer reconstruction of x-ray transmission data from the same axial plane taken at different angles. This generic type of device may include signal analysis and display equipment, patient and equipment supports, component parts, and accessories.(b)
Classification. Class II.