(90 days)
The Digirad 2020tc SPECT Imaging System is intended for use in the generation of both planar and Single Photon Emission Computed Tomography (SPECT) clinical images in Nuclear Medicine applications. The Digirad SPECT Rotating Chair is used in conjunction with the Digirad 2020tc Imager™ to obtain SPECT images in patients who are seated in an upright position.
Specifically, the 2020tc Imager™ is intended to image the distribution of radionuclides in the body by means of a photon radiation detector. In so doing, the system produces images depicting the anatomical distribution of radioisotopes within the human body for interpretation by authorized medical personnel.
The Digirad SPECT Rotating Chair is an option to Digirad 2020tc Imager™ so that SPECT imaging with patients in the upright, seated position may be performed. The Digirad 2020tc Imager™ together with the SPECT Rotating Chair will be the Digirad 2020tc SPECT Imaging System.
The Digirad SPECT Rotating Chair assembly is mounted on a mobile platform and a fixture on which the gamma camera detector head of the 2020tc Imager is mounted. The detector head is connected by way of cables to the processing computer, which includes the associated recording and permanently aligned with respect to the center-of-rotation of the chair assembly, faces towards the patient throughout the period of data acquisition, and accommodates various patient heights with the adjustment of the vertical position. The center of the imaging field-of-view remains fixed relative to the chair's center-of-rotation; however, the horizontal position of the detector head may be moved closer or farther from the surface of the body. The detector head position may be adjusted at any time during the rotation to ensure that the detector head remains as close as possible to the body, but does not collide with an irregular body contour such as the shoulder, breast, etc. The chair assembly provides for the forward-backward (x) and side-to-side (y) adjustment of the chair position to ensure that the body part or organ to be imaged will remain entirely within the field-of-view during SPECT acquisition.
Radionuclide count data are collected at approximately 3 or 6 degree intervals during chair rotation. Data acquisition occurs for approximately 10-20 seconds after the chair rotates to and stops at the next position. Positional steps are adjustable, but remain the same once rotation and data recording have begun. Tomographic cross-sectional slices of the body (e.g., heart) are derived from the serial recordings using standard SPECT reconstruction methods.
Here's an analysis of the provided text regarding the acceptance criteria and study for the Digirad 2020tc SPECT Imaging System:
1. Table of Acceptance Criteria and Reported Device Performance:
| Acceptance Criteria / Performance Metric | Reported Device Performance |
|---|---|
| Chair Stability & Patient Motion (Clinical) | "In no case was any significant movement of the chest noted during the twenty minute simulated acquisition with the rotating chair." |
| Tomographic Image Quality (Clinical) | "Tomographic image quality was judged to be excellent by the Nuclear Medicine physicians at the investigational center and to be at least equal to images obtained from a reference SPECT capable gamma scintillation camera." |
| Accuracy of Reconstruction & Identification of Myocardial Perfusion Defects (Phantom Study) | "The quality of reconstructed tomographic images of a test phantom, obtained with the rotating chair in conjunction with the solid state 2020tc Imager™ and associated processor software, was at least equal to images obtained with a reference SPECT capable gamma camera." (Implies meeting or exceeding the performance of a reference device for accuracy in identifying defects, though quantitative metrics are not provided in this summary.) |
2. Sample Size and Data Provenance:
- Clinical Evaluation (Chair Stability & Patient Motion): The sample size was "healthy volunteer subjects." A specific number is not provided. The data provenance is not explicitly stated but implies a clinical setting, likely in the US given the FDA submission. It was a prospective evaluation.
- Clinical Imaging (Tomographic Image Quality): The sample size was "fourteen patients." The data provenance is not explicitly stated but implies a clinical setting, likely in the US given the FDA submission. It was likely a prospective study.
- Cardiac Phantom Imaging: A specific sample size or number of phantoms used is not provided. This was a laboratory/benchtop study.
3. Number of Experts and Qualifications for Ground Truth:
- Clinical Imaging (Tomographic Image Quality): The ground truth was established by "Nuclear Medicine physicians at the investigational center." The number of physicians is not specified, nor are their detailed qualifications (e.g., years of experience).
- Clinical Evaluation (Chair Stability & Patient Motion) and Cardiac Phantom Imaging: These involve objective physical measurements or comparisons to a reference device, rather than expert interpretation of images for diagnosis.
4. Adjudication Method:
- Clinical Imaging: The text states, "Tomographic image quality was judged to be excellent by the Nuclear Medicine physicians at the investigational center." This suggests a consensus or individual judgment by a group of experts, but a formal adjudication method (e.g., 2+1, 3+1) is not explicitly described.
- Other studies: Adjudication methods are not applicable to the chair stability or phantom studies in the same way.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:
- No, an MRMC comparative effectiveness study, as typically understood in the context of AI-assisted image interpretation, was not described. The study involved comparing the new system's image quality to a "reference SPECT capable gamma scintillation camera" as judged by radiologists, but it was not designed to measure the effect size of human readers improving with this specific AI vs. without AI assistance, as the device is a SPECT imaging system, not an AI interpretation tool.
6. Standalone (Algorithm Only) Performance:
- Yes, in spirit, a standalone performance was done for the imaging system's capability to produce quality images and reconstruct data. The cardiac phantom imaging specifically tested the "accuracy of reconstruction and identification of simulated myocardial perfusion defects" of the system itself, independent of human interpretation for initial image generation. However, this isn't an "algorithm only" performance in the sense of an AI diagnostic algorithm, but rather the performance of the integrated imaging and reconstruction software.
7. Type of Ground Truth Used:
- Clinical Imaging: Expert consensus/interpretation by Nuclear Medicine physicians regarding image quality.
- Clinical Evaluation: Objective observation of movement in healthy volunteers.
- Cardiac Phantom Imaging: Known physical properties of the phantom and comparison to a reference device.
8. Sample Size for the Training Set:
- Not applicable. The document describes a medical imaging device (SPECT system) undergoing clinical evaluation and comparison to a predicate device, not an AI algorithm that requires a distinct training set. The system itself is not described as having an AI component that learns from data in this context.
9. How the Ground Truth for the Training Set was Established:
- Not applicable, as there is no mention of a training set for an AI algorithm.
§ 892.1200 Emission computed tomography system.
(a)
Identification. An emission computed tomography system is a device intended to detect the location and distribution of gamma ray- and positron-emitting radionuclides in the body and produce cross-sectional images through computer reconstruction of the data. This generic type of device may include signal analysis and display equipment, patient and equipment supports, radionuclide anatomical markers, component parts, and accessories.(b)
Classification. Class II.