P Zygmanski¹*, J Lima², A Liles³, V Zhang⁴, I Gineitaite³, E Sajo³, D Brivio¹, (1) Brigham & Women's Hospital, Boston, MA, (2) Hofstra, Mineola, NY, (3) University of Massachusetts Lowell, Lowell, MA, (4) Harvard University, Cambridge, MA

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  P Zygmanski

TU-F115-IePD-F4-5 (Tuesday, 7/12/2022) 1:15 PM - 1:45 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 4

Purpose: A new type of detector array for real-time monitoring of radiation beams in radiotherapy and radiology was developed. Parallel-plane architecture with multiple large-area uniform electrodes orthogonal to beamline was employed. The innovation consists of resistive thin film electrodes with multiple current/voltage readout pairs along their edges. Readouts measure different fractions of integral dose deposited inside the detector, the amount of which depends on the dose distribution with respect to Resistive Electrode Array (REA) geometry.

Methods: Detector response to MLC-collimated x-ray (TB6MV) fields was experimentally determined for circular and rectangular REAs. Multiple (16-24) signals were measured as a function of time (3ms) for static/moving MLCs. MLC fields tests included: rectangular, circular, field size dependence, sweeping gaps, moving irregular MLC, raster scanning beamlet, rotating beamlet.

Results: Detector response is proportional to MLC area and quasi-linear with 2D position of MLC center. Determination of clinically relevant radiation beam parameters from resistive electrode array signals (such MLC position, Monitor Unit fraction) requires calibration using the detector response model with empirical parameters. Circular vs rectangular REA shapes have both advantages and disadvantages. Optimal shape remains to be seen.

Conclusion: The readouts are not obstructing the x-ray fields and the shadow cast by the detector array is uniform. Detector design is scalable to much larger areas without significantly increasing the complexity of fabrication and weight (detector can cover the whole couch or wall). The design is also appropriate for development of multi-layer resistive electrode layers with many resistive electrodes (to absorb more dose) with many readouts (to improve spatial resolution).The intended application of REA is real time beam monitoring for verification of the x-ray, electron or proton machine performance (in radiation oncology or interventional fluoroscopy). But other applications are conceivable due to flexibility of design and low cost prototyping.

Keywords

Radiation Detectors, Quality Control, Quality Assurance

Taxonomy

TH- External Beam- Photons: Development (new technology and techniques)

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