Towards Flat-Field MTF Measurements Via the Noise Response Method As Part of an Interventional Radiology QC Program
Abstract
Purpose
The modulation transfer function (MTF) is a standard metric for quantifying the spatial resolution of radiographic imaging detectors. Measurement of the MTF can be achieved through the Noise Response (NR) method, which utilizes only flat-field images for MTF determination and obviates the need for precision test objects as required by traditional techniques. The procedural simplicity of this method makes it amiable for inclusion in routine clinical quality control (QC) workflows. This study explores the feasibility of the NR method for spatial resolution consistency checks as part of an interventional radiology (IR) QC program.
Methods
Single-shot flat-field acquisitions were taken with stationary C-arms equipped with digital flat-panel detectors. The noise power spectrum (NPS) of these images was utilized for MTF determination via the NR method, which applies cascaded linear-systems theory to derive a general relationship between the detector quantum NR and the MTF. Two sets of imaging conditions were used: One according to IEC 62220-1 for NPS determination with maximum source-to-imager distance (SID) and RQA5 beam quality, and one at 100 cm SID with a solid aluminum phantom as utilized in a recently established institutional IR QC program. NR analysis based on previously developed MATLAB scripts was explored for detector MTF determinations.
Results
Both imaging conditions resulted in similar fluoroscope techniques being utilized. Initial MATLAB NR analysis proved promising, which has prompted development of a more efficient and robust implementation in Python.
Conclusion
A feasibility study for applying the NR method as part of an IR QC program was initiated. Detector flat-field images were obtained for processing via the NR method, with the aim of providing a quick and simple means of spatial resolution consistency checks that can be implemented as part of daily IR QC.