Use of local noise power spectrum and wavelet analysis in quantitative image quality assurance for EPIDs

Abstract

The proposed local NPS (r-square values) showed superior sensitivity to the noise level variations of individual subpanels compared with global quantitative metrics such as MTF, NPS, and DQE. Wavelet analysis was effective in detecting isolated defective pixels and inter-subpanel flat-fielding artifacts. The proposed methods are promising for the early detection of imaging artifacts of EPIDs.

AAPM Task Group 198 Report: An implementation guide for TG 142 quality assurance of medical accelerators

“…129,130 These tests can be very sensitive to deterioration in image quality, most commonly caused by subpanel artifacts. The use of local noise power spectrum and wavelet analysis is described by Lee et al 131…”

Assessing the accuracy of electronic portal imaging device (EPID)‐based dosimetry: II. Evaluation of a dosimetric uncertainty budget and development of a new film‐in‐EPID absorbed dose calibration methodology

“…To improve the accuracy of the proposed film‐based calibration methodology, the EPID was disassembled for the purpose of modeling the flat‐panel detector in detail using the DOSXYZnrc usercode (v2019a) of the EGSnrc MC code system 18–19 . The identification of layer compositions and the measurement of physical dimensions were combined with data available in the literature and from manufacturer‐supplied specifications, resulting in an MC model consisting of 18 separate layers and 13 unique materials 20–22 . The default MC transport parameters in EGSnrc were used.…”

“…[18][19] The identification of layer compositions and the measurement of physical dimensions were combined with data available in the literature and from manufacturer-supplied specifications, resulting in an MC model consisting of 18 separate layers and 13 unique materials. [20][21][22] The default MC transport parameters in EGSnrc were used. The Mohan 6 MV photon energy spectrum was used to define a collimated point source located at an SSD of 160 cm.…”

A phantom based evaluation of the clinical imaging performance of electronic portal imaging devices

“…Moreover, their application has progressively expanded to include the acquisition of dosimetric data related to radiation treatment, either through in vivo dosimetry or via patient specific pretreatment QA [ 2 ]. The considerable challenges stemming from the extensive clinical integration of EPIDs [ 4 ] however, underscore the necessity for enhanced QA procedures to guarantee that the system operates as intended [ 5 , 6 ]. Image quality-based tests remain essential, since failure of these tests would result in a notably compromised functionality for dosimetry purposes.…”

“…Studies, e.g. investigating various issues such as the effects of external aluminum target beam of the LINAC on EPID [ 10 ], the use of wavelet analysis to detect and isolate defective pixels and artifacts for quantitative quality assurance (QA) of EPIDs, characterizing the image noise, have been published [ 6 ]. In addition, a review is referred to the properties of dosimetry and imaging of radiation detectors, such as the physical principles of operation of calorimeters ionization, charge detectors, semiconductor, luminescent, chemical detectors, and radiochromic films [ 11 ].…”