Objective assessment of image quality V Photon-counting detectors and list-mode data

Abstract

A theoretical framework for detection or discrimination tasks with list-mode data is developed. The object and imaging system are rigorously modeled via three random mechanisms: randomness of the object being imaged, randomness in the attribute vectors, and, finally, randomness in the attribute vector estimates due to noise in the detector outputs. By considering the list-mode data themselves, the theory developed in this paper yields a manageable expression for the likelihood of the list-mode data given the object being imaged. This, in turn, leads to an expression for the optimal Bayesian discriminant. Figures of merit for detection tasks via the ideal and optimal linear observers are derived. A concrete example discusses detection performance of the optimal linear observer for the case of a known signal buried in a random lumpy background.

A comparative study based on image quality and clinical task performance for CT reconstruction algorithms in radiotherapy

“…In order to further analyze the change in CT number and its affect on dose calculation, we performed the quantitative comparison to ascertain whether the treatment plans generated using different radiation dose scans and reconstruction algorithms were clinically equivalent 11 , 12 . For the 53 cm sized phantom, five pairs of different dose images (tube potential: 120 kVp; ${\text{CTDI}}_{\text{vol}}$: 32.7, 65.4, 98.1, 130.8, and 168.0 mGy) were reconstructed through the FBP and the ${\text{iDose}}^4$ L3 algorithms, respectively.…”

“…It has been reported from routine works of our clinical institutions that traditional diagnostic image quality definitions may not be realistic enough to determine the performance of the radiotherapy tasks, which certainly influence treatment planning accuracy. Inspired by a recent paradigm shift of image quality assessment that image quality should be defined by the ability of a user to perform medically or scientifically relevant tasks with the image data, 12 , 13 the purpose of this study is: 1) to conduct new comparative experiments of the FBP and ${\text{iDose}}^4$ algorithms, with varying noise reduction levels, by associating the ALARA principles with radiotherapy task performance, and 2) to provide suggestions for clinical radiotherapy usage of the ${\text{iDose}}^4$algorithm. This study is expected to fill the gap between image quality assessment and the clinical usage of CT simulation images in radiotherapy.…”

Radiance and photon noise: imaging in geometrical optics, physical optics, quantum optics and radiology

“…This form of data storage is referred to as list mode, in contrast to the pixellated or binned mode implicit in (5.1) and (5.2). Listmode data storage has received considerable attention in the radiology literature, [11][12][13] and it is used routinely in PET.…”

“…For self-luminous objects as in astronomy, nuclear medicine or fluorescence microscopy, Caucci and Barrett 13 have shown that (6.2) where ℒ is a linear operator that maps L 2 (ℝ 3 ) to L 2 (ℝ K ). We emphasize that ℒ is linear even when the relation between raw data (e.g., sensor signals) and estimated attributes is nonlinear.…”

Objective assessment of image quality VI: imaging in radiation therapy

“…The theory underlying OAIQ is detailed in earlier papers in this series [1-5] and in [6]. For diagnostic tasks, many evaluation methods related to receiver operating characteristic (ROC) curves have been developed and used to assess imaging systems and reconstruction algorithms [7,8].…”