Performance assessment of active vs passive pixel x‐ray angiography detector systems using a bias‐corrected channelized Hotelling observer and adult patient‐equivalent experimental conditions

Fetterly, Kenneth A.

doi:10.1002/mp.13192

Cited by 5 publications

(17 citation statements)

References 29 publications

(64 reference statements)

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“…In our clinical practice, images are routinely rescaled from the “native” pixel matrix of the detector to 512

\times

512 8 bit matrices for retrospective review and archival. Previous work demonstrated that d ′ estimates from 512

\times

512 8 bit images were 4% lower than those based on the native pixel matrix 35 . To mimic the clinical practice and to minimize computational resources, 512

\times

512 8 bit images were exported from the angiography system and used to estimate d ′ in this work.…”

Section: Methodsmentioning

confidence: 99%

“…For example, when comparing passive vs active pixel detector technologies at low exposure imaging conditions, d 0 bias due to TVNS noise is larger for the former. 35 This is mainly due to the reduced electronic noise achievable in active pixel detectors.…”

Section: B Bias From Temporally Variable Nonstationary Noisementioning

confidence: 99%

“…This d ′ bias is more noticeable under imaging conditions where electronic noise contributes substantially relative to x‐ray quantum noise. For example, when comparing passive vs active pixel detector technologies at low exposure imaging conditions, d ′ bias due to TVNS noise is larger for the former 35 . This is mainly due to the reduced electronic noise achievable in active pixel detectors.…”

Section: Theorymentioning

confidence: 99%

“…Previous work with CHO models in x-ray angiography by our group 17,35 identified location-specific, nonrandom electronic noise variation between individual frames of a multiframe image as a source of measurement bias. That work referred to the electronic noise inherent to the detector as temporally variable nonstationary (TVNS) noise, or otherwise noise that was nonstationary in the time domain.…”

Section: B Bias From Temporally Variable Nonstationary Noisementioning

confidence: 99%

“…Previous work demonstrated that d 0 estimates from 512 Â 512 8 bit images were 4% lower than those based on the native pixel matrix. 35 To mimic the clinical practice and to minimize computational resources, 512 Â 512 8 bit images were exported from the angiography system and used to estimate d 0 in this work. Also, as stated in Section 1, unprocessed images with static objects were used in this paper before moving forward with future work including image processing and moving objects.…”

Section: D1 Phantom and Image Acquisitionmentioning

confidence: 99%

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Task‐specific efficient channel selection and bias management for Gabor function channelized Hotelling observer model for the assessment of x‐ray angiography system performance

et al. 2021

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Purpose: Channelized Hotelling observer (CHO) models have been implemented to assess imaging performance in x-ray angiography systems. While current methods are appropriate for assessing unprocessed images of moving test objects upon uniform-exposure backgrounds, they are inadequate for assessing conditions which more appropriately mimic clinical imaging conditions including the combination of moving test objects, complex anthropomorphic backgrounds, and image processing. In support of this broad goal, the purpose of this work was to develop theory and methods to automatically select a subset of task-specific efficient Gabor channels from a task-generic Gabor channel base set. Also, previously described theory and methods to manage detectability index (d 0 ) bias due to nonrandom temporal variations in image electronic noise will be revisited herein. Methods: Starting with a base set of 96 Gabor channels, backward elimination of channels was used to automatically identify an "efficient" channel subset which reduced the number of channels retained in the subset while maintaining the magnitude of the d 0 estimate. The concept of a pixelwise Hotelling observer (PHO) model was introduced and similarly implemented to assess the performance of the efficient-channel CHO model. Bias in d 0 estimates arising from temporally variable nonstationary noise was modeled as a bivariate probability density function for normal distributions, where one variable corresponds to the signal from the test object and the other variable corresponds to the signal from temporally variable nonstationary noise. Theory and methods were tested on uniform-exposure unprocessed angiography images with detector target dose (DTD) of 6, 18, and 120 nGy containing static disk-shaped test objects with diameter in the range of 0.5 to 4 mm. Results: Considering all DTD levels and test object sizes, the proposed method reduced the number of Gabor channels in the final subset by 63-82% compared to the original 96 Gabor channel base set, while maintaining a mean relative performance (ðd 0 CHO =d 0 PHO Þ Â 100%) of 95% AE 4% with respect to the reference PHO model. Experimental results demonstrated that the bivariate approach to account for bias due to temporally variable nonstationary noise resulted in improved correlation between the CHO and PHO models as compared to a previously proposed univariate approach. Conclusions: Computationally efficient backward elimination can be used to select an efficient subset of Gabor channels from an initial channel base set without substantially compromising the magnitude of the d 0 estimate. Bias due to temporally variable nonstationary noise can be modeled through a bivariate approach leading to an improved unbiased estimate of d 0 .

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“…In our clinical practice, images are routinely rescaled from the “native” pixel matrix of the detector to 512

\times

512 8 bit matrices for retrospective review and archival. Previous work demonstrated that d ′ estimates from 512

\times

512 8 bit images were 4% lower than those based on the native pixel matrix 35 . To mimic the clinical practice and to minimize computational resources, 512

\times

512 8 bit images were exported from the angiography system and used to estimate d ′ in this work.…”

Section: Methodsmentioning

confidence: 99%

Section: B Bias From Temporally Variable Nonstationary Noisementioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: B Bias From Temporally Variable Nonstationary Noisementioning

confidence: 99%

Section: D1 Phantom and Image Acquisitionmentioning

confidence: 99%

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Task‐specific efficient channel selection and bias management for Gabor function channelized Hotelling observer model for the assessment of x‐ray angiography system performance

et al. 2021

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Adaptation of a channelized Hotelling observer model to accommodate anthropomorphic backgrounds and moving test objects in X‐ray angiography

Gomez‐Cardona,

Favazza,

Leng

et al. 2023

Medical Physics

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BackgroundPrior implementations of the channelized Hotelling observer (CHO) model have succeeded in assessing the performance of X‐ray angiography systems under a variety of imaging conditions. However, often times these conditions do not resemble those present in routine clinical imaging scenarios, such as having complex anthropomorphic backgrounds in conjunction with moving test objects.PurposeThis work builds up on prior established CHO methods and introduces a new approach to switch from the already established “multiple‐sample” CHO implementation to a “single‐sample” technique. The proposed implementation enables the inclusion of moving test objects upon nonuniform backgrounds by allowing only a single sample to represent the test object present condition that is to be used within the statistical test to estimate the detectability index.MethodsTo assess the proposed method, two image data sets were acquired with a clinical X‐ray angiography system. The first set consisted of a uniform background in combination with static test objects while the second consisted of an anthropomorphic chest phantom in conjunction with moving test objects. The first set was used to validate the proposed approach against the multiple‐sample method while the second was used to assess the feasibility of the proposed method under a variety of imaging conditions, including seven object sizes and seven detector target dose (DTD) levels.ResultsFor the uniform background data set, considering all detectability indices greater or equal than 1, the ratio between the detectability indices of the proposed single‐sample approach versus the multiple‐sample method was 0.997 ± 0.056 (range 0.884–1.159). The average single‐direction width of the 95% confidence intervals (CIs) of the detectability index estimates for the multiple‐sample method was 0.38 ± 0.43 (range 0.03–2.20). For the single‐sample approach, the average width was 2.52 ± 0.63 (range 1.11–5.44). For the anthropomorphic background image set, the results were consistent with classical quantum‐limited signal‐to‐noise ratio (SNR) theory. The magnitude of the detectability indices varied predictably with changes in both object size and DTD, with the highest value associated with the highest dose and the largest object size. Additionally, the proposed method was able to capture differences in the imaging performance for a given test object across the field of view, which was associated with the attenuation levels provided by different features of the anthropomorphic background.ConclusionsA new single‐sample variant of the CHO model to assess the performance of X‐ray angiography imaging systems is proposed. The new approach is consistent with quantum‐limited image quality theory and with a standard implementation of the CHO model. The proposed method enables the assessment of moving test objects in combination with complex, nonuniform image backgrounds, thereby opening the possibility to assess imaging conditions which more closely resemble those used in clinical care.

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Characterization of GE discovery IGS 740 angiography system by means of channelized Hotelling observer (CHO)

et al. 2019

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The aim of the study is to use the well-known channelized Hotelling observer model (CHO) to characterize a recently installed angiography system (GE Discovery IGS 740) using sets of images of a contrast-detail phantom acquired with clinical protocols. A Leeds TO10 phantom was used. The phantom has 108 details: 12 diameters (size range: 0.25 mm–11 mm), each with nine contrasts (declared range: 0.012–0.930 at 70 kVp 1.00 with 1 mm Cu filtration). TO10 has been imaged between two 10 cm thick homogeneous solid water slabs. Two FOVs (32 cm and 20 cm) were used. Fluoroscopy images were taken using an abdominal protocol at two different frame rates (15 fps and 7.5 fps) and at two dose levels (low and normal); cineangiography images were acquired using an abdominal protocol at 15 fps at two dose levels (low and normal). A 40 Gabor channels CHO with internal noise was used. Human observers’ studies were carried out to tune the internal noise parameter and to validate the model observer. Contrast-detail curves were obtained from the CHO output using a visibility threshold of 75% and fitted with Rose’s model theory in order to characterize the angiography system. Wilcoxon rank-sum tests were performed to investigate possible differences among the different sets of images. The CHO can distinguish between the two dose levels (p -values < 0.002), while FOV and frame rate do not affect the contrast-detail curves significantly. It is important to note that the CHO does not find statistically significant differences between a fluoroscopy with FOV = 20 cm at normal dose level (17.6 mGy min−1) and a cineangiography with FOV = 32 cm low dose level (42.1 mGy min−1). This result can lead to a dose reduction of about 70% for our specific task (i.e. a static, disc shaped object at known location in homogeneous field). Given their stability in comparison to human observers, model observers provide an effective tool for image quality evaluation.

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Performance assessment of active vs passive pixel x‐ray angiography detector systems using a bias‐corrected channelized Hotelling observer and adult patient‐equivalent experimental conditions

Cited by 5 publications

References 29 publications

Task‐specific efficient channel selection and bias management for Gabor function channelized Hotelling observer model for the assessment of x‐ray angiography system performance

Task‐specific efficient channel selection and bias management for Gabor function channelized Hotelling observer model for the assessment of x‐ray angiography system performance

Adaptation of a channelized Hotelling observer model to accommodate anthropomorphic backgrounds and moving test objects in X‐ray angiography

Characterization of GE discovery IGS 740 angiography system by means of channelized Hotelling observer (CHO)

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