(56 days)
ThinkQA is a radiation therapy dosimetry Quality Assurance (QA) device consisting of a software framework intended to contain a suite of modules to verify that radiation dose actually delivered to the patient is as intended.
The Epibeam module contained in ThinkQA is intended to be used as follows:
Epibeam is a standalone software tool independent of the linear accelerator, the TPS and the Record-and-Verify system. It is intended to assist in reducing the clinical risk in the delivery of radiotherapy treatments and does not alter the treatment delivery. It is to be used by a radiation oncology medical professional as a guide to provide pretreatment plan delivery verification.
The software is to be used for the purposes of detecting errors in the delivery of radiation therapy prior to treatment, like corruption of the transferred plan data to the treatment unit, inappropriate multileaf collimator sequence or beam output malfunctioning. The software acquires data from the Electronic Portal Imaging Device (EPID) during a blank fraction dedicated to the pretreatment verification without the patient and subsequently processes it. The processed data is compared with data calculated by the Epibeam system. The comparison is derived on one hand, from the application of dose conversion to the EPID data and on the other hand, from the computation of a predicted dose image under ideal conditions of functioning. A gamma-index analysis is then performed according to the dose difference and distance-to-agreement criteria provided by the user.
Epibeam is not a treatment planning system and cannot be used to generate radiotherapy treatment plans. It provides an independent means of checking the reliability of the dose delivery for each beam in reference to TPS data.
Epibeam therefore provides an added level of treatment quality assurance, thus giving clinicians confidence especially when complex treatment techniques are employed (gantry-fixed and rotational intensity modulated radiation therapy).
Epibeam is intended to support decision making in relation to the delivery of treatment plan to the patient with every clinical linear accelerators equipped with an EPID, but does not alter the existing Indications for Use of the treatment unit.
ThinkQA is a modular software suite composed of the module Epibeam which is a quality assurance tool dedicated to Patient Specific QA for pretreatment verification of irradiation beams.
The EPIbeam verification module integrated to the ThinkOA software platform is a Quality Assurance tool in external beam radiation therapy, used in combination with the electronic portal imaging device (EPID) and dedicated to the irradiation beam pre-treatment verifications, particularly for IMRT and VMAT techniques.
EPIbeam principle is based on the comparison of two images expressed in terms of absolute dose: on the one hand, a RT Plan defined in the TPS is used for the acquisition of a real portal image (test image) with the EPID directly irradiated (without attenuating medium); on the same RT Plan is used to compute a theoretical portal image (reference image). Specific models and algorithms are applied to express both images in the same absolute dose terms.
The dose images obtained from the same RT Plan, one by the conversion model of the acquired raw EPID images and the other by the prediction model, can be quantitatively compared through dose difference mappings or 2D gamma-index. Both models are based on dosimetric data provided from the TPS.
Here's a summary of the acceptance criteria and study details for the ThinkQA Epibeam device, based on the provided document:
1. Table of Acceptance Criteria and Reported Device Performance
The document does not explicitly present a table of numerical acceptance criteria. Instead, it describes functional requirements and states that "acceptance criteria were met." The performance is generally framed as demonstrating substantial equivalence to the predicate device.
| Acceptance Criteria (Implied / Functional) | Reported Device Performance |
|---|---|
| Pretreatment check functionality | Yes |
| Independent software operation | Yes |
| Ability to acquire pretreatment images | Yes |
| Algorithm for computing predicted reference dose image | Yes |
| Algorithm for converting acquired portal image into dose image | Yes |
| Comparison of measured and reference dose images via gamma-index analysis | Yes |
| Generation of reviewer reports | Yes |
| Inclusion of gamma agreement index per beam | Yes |
| Inclusion of significant statistic gamma index values per beam | Yes |
| Ability to view test and reference images | Yes |
| Ability to view superimposed test/reference dose profiles | Yes |
| Ability to view 2D gamma index distribution | Yes |
| Patient control database integration | Yes |
| User-defined Alert Criteria for out-of-tolerance analysis | Yes |
| Import Approved Plan data from Treatment Planning System | Yes |
| Import Portal Images from pretreatment fraction | Yes |
| Automatic offline analysis | Yes |
| Support for multiple treatment techniques (Static, IMRT, VMAT) | Yes |
| Requirement for EPID panel Calibration for commissioning | Yes |
| Use of TPS results for dose data reference | Yes |
| Demonstration of substantial equivalence to predicate device (K133572) | Achieved through performance, functional, and algorithmic testing. |
| Conformance to applicable technical design specification | Met |
| Achievement of safety and effectiveness | Achieved |
| Meeting device requirements under normal conditions of use | Met |
2. Sample Size Used for the Test Set and Data Provenance
The document does not specify a distinct "test set" with a particular sample size from real patient data. The validation seems to be based on "clinically representative conditions" and "test cases" rather than a specific patient cohort for a validation study.
- Sample Size for Test Set: Not explicitly stated as a separate patient-based test set. The testing involved "unit, integration and system tests" and "validation of the system under clinically representative conditions."
- Data Provenance: Not specified regarding country of origin or whether it was retrospective or prospective. Given the nature of a software release, it's likely synthetic or internally generated test cases reflecting various clinical scenarios, and potentially retrospective clinical data for "clinically representative conditions."
3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications
The document does not mention the use of external experts to establish a "ground truth" for a specific test set. The ground truth for the device's function appears to be established through:
- Comparison of acquired EPID data with data calculated by the Epibeam system itself, based on TPS plans and prediction models.
- The assumption that the TPS data and the device's prediction model represent the "ideal conditions of functioning" or "reference."
4. Adjudication Method for the Test Set
Not applicable/not mentioned. There's no indication of an adjudication method involving multiple human readers for establishing a ground truth or resolving discrepancies in a test set.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No, an MRMC comparative effectiveness study was not done. The document focuses on the standalone performance and substantial equivalence of the software tool.
6. Standalone (i.e., algorithm only without human-in-the-loop performance) Study
Yes, a standalone study was done. The entire premise of the "Performance Testing - Bench" section describes the testing of the ThinkQA software's functionalities and algorithms independently. The Epibeam module is described as a "standalone software tool independent of the linear accelerator, the TPS and the Record-and-Verify system." The performance testing demonstrates that the software itself "meets the requirements of the device."
7. Type of Ground Truth Used
The ground truth for the comparison performed by the Epibeam module is based on:
- Predicted dose image: Calculated by the Epibeam system under ideal conditions, derived from the RT Plan defined in the Treatment Planning System (TPS).
- Dose conversion of acquired EPID data: The software converts raw EPID images into dose terms.
- TPS data: The models and algorithms used by Epibeam are based on dosimetric data provided by the TPS, which serves as a reference for the planned dose.
Essentially, the "ground truth" for the device's internal comparison is the expected dose distribution as calculated by the validated Treatment Planning System and through the device's own prediction models.
8. Sample Size for the Training Set
The document does not explicitly mention a "training set" or its size. As a "software framework" and a "Quality Assurance tool," its development likely involved conventional software engineering practices, potentially including internal data for model development and calibration, but a specific "training set" like in deep learning models is not detailed.
9. How the Ground Truth for the Training Set Was Established
Since a "training set" is not explicitly mentioned, the method for establishing its ground truth is also not described. The device's foundational data relies on the principles of radiation dosimetry and verified TPS data.
§ 892.5050 Medical charged-particle radiation therapy system.
(a)
Identification. A medical charged-particle radiation therapy system is a device that produces by acceleration high energy charged particles (e.g., electrons and protons) intended for use in radiation therapy. This generic type of device may include signal analysis and display equipment, patient and equipment supports, treatment planning computer programs, component parts, and accessories.(b)
Classification. Class II. When intended for use as a quality control system, the film dosimetry system (film scanning system) included as an accessory to the device described in paragraph (a) of this section, is exempt from the premarket notification procedures in subpart E of part 807 of this chapter subject to the limitations in § 892.9.