Image information content and patient exposure

Motz, J. W.; Danos, Michael

doi:10.1118/1.594405

Cited by 138 publications

(76 citation statements)

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“…The physical origin of these signals and their differences are specialised questions which we do not treat here; we will concentrate on the interaction of the measurement of these quantities and the propagation of the noise in their measurement. The interesting questions of optimising the contribution to the SNR of the detected difference signal as a function of signal energy for photons (Oosterkamp 1961, Motz andDanos 1978) and pulse sequence for NMR (Edelstein et al 1983) are essential matters which are addressed elsewhere.…”

Section: Discussionmentioning

confidence: 99%

“…Finally, some considerations of system efficiency and exposure optimisation are given by Wagner and Jennings (1979) and Jafroudi et al (1982), including effects of scatter (Wagner et al 1980) and beam energy (Motz and Danos 1978). These treatments involve the concept of detective quantum efficiency and the generalisation of this to exposure and dose efficiency.…”

Section: Exposure Efficiencymentioning

confidence: 99%

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Unified SNR analysis of medical imaging systems

1985

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The ideal observer signal to noise ratio (SNR) has been derived from statistical decision theory for all of the major medical imaging modalities. This SNR provides an absolute scale for image system performance assessment and leads to instrumentation design goals and constraints for imaging system optimisation since no observer can surpass the performance of the ideal observer. The dependence of detectable detail size on exposure or imaging time follows immediately from the analysis. A framework emerges for comparing data acquisition techniques, e.g. reconstruction from projections versus Fourier methods in NMR imaging, and time of flight positron emission tomography (TOFPET) versus conventional PET. The approach of studying the ideal observer is motivated by measurements on human observers which show that they can come close to the performance of the idea) observer, except when the image noise has negative correlations-as in images reconstructed from projections-where they suffer a small but significant penalty.

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Section: Discussionmentioning

confidence: 99%

Section: Exposure Efficiencymentioning

confidence: 99%

Unified SNR analysis of medical imaging systems

1985

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“…For all these advances, the fundamental problem that remains is that with conventional attenuation-based X-ray imaging, the signal is the reduction in transmitted X-ray photons. To have a signal (i.e., change in attenuation) that adequately exceeds the photon noise (the statistical noise due to the quantum nature of the X-ray photons Ӎ ͌N, where N is the number of photons per resolution unit), at least 10 4 -10 5 photons have to be exposed to the region of interest per resolution unit (27). A methodology that shows some promise toward practical use is X-ray imaging, which is based on the consequences of refraction of X-rays (resulting from the slightly different velocity of X-ray photons through different materials, essentially the same as the refraction of light) within the tissues (28,29).…”

Section: Discussionmentioning

confidence: 99%

Micro-Computed Tomography of the Lungs and Pulmonary-Vascular System

Ritman¹

2005

Proceedings of the American Thoracic Society

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Three-dimensional imaging of the intact lung and its vasculature is essential if the hierarchical and volumetric aspects of its structures and functions are to be quantitated. Although this is possible with clinical multislice helical CT scanners, the spatial resolution does not scale down adequately for small rodents for which cubic voxel dimensions of 50-100 m are required. Micro-computed tomography (micro-CT) provides the necessary spatial resolution of 3D images of the intact thoracic contents. Micro-CT can provide higher resolution so that basic micro-architectural structures, such as alveoli, can be individually visualized and quantitated. Dynamic events, such as the respiratory and cardiac cycles, can be imaged at multiple time points throughout a representative cycle by coordinating the scan sequence (i.e., gating) to the cycle phase of a sequence of cycles. Fusion of the micro-CT image data with other image data, such as micro-SPECT or histology, can enhance the information content beyond the mainly structural information provided by micro-CT. Conventional attenuation-based X-ray imaging can involve significant X-ray exposures at high spatial resolutions, and this could affect the phenotype (e.g., via interstitial fibrosis) and genotype (e.g., via mutation), so its use in longitudinal studies using micro-CT may be limited in some cases. However, because of recent developments in which the phase shift or refraction of X-rays rather than attenuation is used, the X-ray exposure may be significantly reduced.Keywords: microarchitecture; pulmonary hypertension; alveoli; airways Micro-computed tomography (micro-CT) is a rapidly developing imaging capability that has been described in detail elsewhere (1). This development is driven in large measure by the fact that because mice are rapidly becoming the experimental animals of choice for many research endeavors, there is motivation to scale clinical imaging capabilities down to the mouse level. There are several aspects to the scaling of the spatial and temporal resolution and volume scanned (2). One is to scale so as to generate a transaxial tomographic image equivalent to a clinical scan. Thus, with clinical multislice helical scanning, CT of the thorax generates 3D images that are approximately 300 to 400 mm in transverse diameter and are made up of voxels (a 3D picture-element or pixel) ‫ف‬ 1 mm 3 in volume. A "mini" CT scanner that is scaled to a proportional voxel resolution in a mouse (with a 20 mm thoracic diameter) would involve voxels ‫ف‬ 75 m in diameter. The mouse's lungs have a combined volume of about 1.3 cm 3 ; therefore, in the mouse a 3D volume of at least 2 cm 3 must be imaged to capture the entire lung. How- ever, the mouse heart and respiratory rate are much higher than in humans, so cardio-respiratory dynamic processes are much more difficult to image in mice than in humans (3) because the micro-CT scan durations are generally limited by the rate of X-ray production. If microscopic structures are to be imaged with micro-CT, image resolution...

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“…Contrast and spatial resolution fundamentally defines the limits of perceptibility and accuracy within the image [19,20]. The latter are considered an important aid to the radiographic perception of small and low contrast objects within the anatomy of the root canal.…”

Section: Discussionmentioning

confidence: 99%

Effects of Horizontal Beam Angulations and Imaging System on the Identification of the MB2 of Maxillary First Molar: An ROC Analysis

Orafi¹,

Hammad²

2017

ojdom

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The aim of this study was to evaluate the optimal horizontal beam angulation for the detection of second mesiobuccal canal (MB2) in maxillary first molar using three imaging modalities in terms of receiver operating characteristic (ROC) curve. Micro-computed tomography (micro-CT) was used to validate the presence or absence of MB2 canal. Images were generated with three different imaging modalities (analogue film, Visualix and VistaScan) for the twelve models at 10° intervals between 0° to 30° from both right and left sides. Each model consisted of maxillary second premolar, maxillary first and second molar arranged to replicate a posterior dentate maxilla. Images were scored on a 5-point scale by 15 observers. ROC analysis was performed to identify the optimal horizontal angulation for the three imaging modalities and the best observer groups. ANOVA was also used to assess if there was a difference between the three imagining modalities and between the observer groups. ROC analysis demonstrated that the highest area under the curve (AUC) was related to angle +20° (right). The AUC for the three radiographic techniques at angle +20° were as followed (analogue film, 0.625; Visualix, 0.544; VistaScan, 0.508). There was a significant difference between the analogue film and the other two digital systems (p<0.05). The +20° horizontal beam angulation for the analogue film was found to be optimal in the identification of MB2 canal with all imaging modalities. Endodontists demonstrated a significantly better performance compared with the other two groups.

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Image information content and patient exposure

Cited by 138 publications

References 0 publications

Unified SNR analysis of medical imaging systems

Unified SNR analysis of medical imaging systems

Micro-Computed Tomography of the Lungs and Pulmonary-Vascular System

Effects of Horizontal Beam Angulations and Imaging System on the Identification of the MB2 of Maxillary First Molar: An ROC Analysis

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