How much image noise can be added in cardiac x-ray imaging without loss in perceived image quality? (original) (raw)
Related papers
Radiation Protection Dosimetry, 2013
This study investigates the influence of the initial X-ray system setting on patient doses and image quality in interventional cardiology procedures. Two dedicated interventional cardiology systems were studied: a system with image intensifier (II) and a flat detector (FD) system. Entrance surface air kerma (ESAK) rates in fluoroscopy and ESAK per frame in the acquisition mode were measured on the surface of a PMMA phantom for the field of views (FOV) of 23 and 17 cm (II system) and 25 and 20 cm (FD system). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were estimated using DICOM images obtained during the measurements. System performances were compared using a figure of merit combining SNR and ESAK. The influence of system setting on patient doses was investigated analysing the information for air kerma area product (KAP) and cumulative dose (CD) at the patient entrance reference point, for a sample of coronary angiography examinations. ESAK rates in fluoroscopy modes were a factor of 2 higher in the FD system for the similar FOVs, resulting in a factor of 1.9 higher median values of KAP and CD for patients with FD system than for the II system. SNR and CNR for the FD system were better than the equivalent FOVs with II. The resulting FOM was better for the FD system in both FOVs. Potential for optimisation was suggested by adjusting system settings.
Machine vision image quality measurement in cardiac x-ray imaging
Image Processing: Algorithms and Systems XIII, 2015
The purpose of this work is to report on a machine vision approach for the automated measurement of x-ray image contrast of coronary arteries filled with iodine contrast media during interventional cardiac procedures. A machine vision algorithm was developed that creates a binary mask of the principal vessels of the coronary artery tree by thresholding a standard deviation map of the direction image of the cardiac scene derived using a Frangi filter. Using the mask, average contrast is calculated by fitting a Gaussian model to the greyscale profile orthogonal to the vessel centre line at a number of points along the vessel. The algorithm was applied to sections of single image frames from 30 left and 30 right coronary artery image sequences from different patients. Manual measurements of average contrast were also performed on the same images. A Bland-Altman analysis indicates good agreement between the two methods with 95% confidence intervals-0.046 to +0.048 with a mean bias of 0.001. The machine vision algorithm has the potential of providing real-time context sensitive information so that radiographic imaging control parameters could be adjusted on the basis of clinically relevant image content.
Evaluation of dose–image-quality optimization in digital chest radiography
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
In this study, we aimed to evaluate the operation conditions and reduce patient doses while maintaining acceptable image quality in digital chest radiography. A geometric chest phantom with built-in regional test objects for quantitative assessment of image quality was used to produce images that simulate a chest projection. Images of the chest phantom were obtained using a GE Revolution XR/d digital X-ray system operated at tube potentials from 62 to 132 kVp with the grid and a distance of 180 cm between the source and image system. The X-ray images were obtained with the automatic exposure control (AEC) mode. Raw data of the acquired images were used for image-quality analysis. The signal-to-noise ratio (SNR) was used as an image-quality indicator and a figure of merit (FOM) computed by dividing the SNR 2 by the effective dose was used to estimate the optimization of the chest radiography. The routine operation tube potential of 112 kVp seems optimal for subdiaphragm examinations but not for lung and heart examinations.
Context sensitive cardiac x-ray imaging: a machine vision approach to x-ray dose control
Journal of Electronic Imaging, 2015
Modern cardiac x-ray imaging systems regulate their radiation output based on the thickness of the patient to maintain an acceptable signal at the input of the x-ray detector. This approach does not account for the context of the examination or the content of the image displayed. We have developed a machine vision algorithm that detects iodine-filled blood vessels and fits an idealized vessel model with the key parameters of contrast, diameter, and linear attenuation coefficient. The spatio-temporal distribution of the linear attenuation coefficient samples, when appropriately arranged, can be described by a simple linear relationship, despite the complexity of scene information. The algorithm was tested on static anthropomorphic chest phantom images under different radiographic factors and 60 dynamic clinical image sequences. It was found to be robust and sensitive to changes in vessel contrast resulting from variations in system parameters. The machine vision algorithm has the potential of extracting real-time context sensitive information that may be used for augmenting existing dose control strategies.
Noise Analysis in Digital Radiography
1986
Noise plays a dominant role in the detection of low-contrast objects in any imaging system. Until the advent of the computed tomography (CT) scanner and more recently digital radiography, noise in an imaging system (typically a screen-film combination) was considered to have two major components: quantum mottle, the statistical fluctuations in the number of detected photons, and structure noise, due to phosphor screen inhomogeneities and film grain. The development of electronic X-ray detectors and in particular digital video subtraction systems has added much complexity to noise analysis. Due to the many new noise sources present, noise analysis now requires new evaluation criteria and techniques. The rapid development of digital subtraction angiography in the past few years has required the use of new and improved imaging components. (1-12) These improvements have been focused heavily upon noise reduction particularly in the TV system. (13) The signal-to-noise ratio (SNR) of the TV camera required significant improvements before digital video angiography with intravenous (IV) injections could be implemented. The noise in the imaging chain which ends up in the output of the system, the final image, deteriorates the quality of the final image in both a subjective and a quantitative sense. This noise may lead to an undetected lesion in a visual interpretation reading or may create errors in quantitative results, such as percent stenosis or regional blood flow.
Optimization of Image Quality and Patient Dose in Digital Radiography of the Chest
Journal of Babol University of Medical Sciences, 2017
BACKGROUND AND OBJECTIVE: Digital systems have been replacing with screen-film analogue systems in diagnostic radiology departments, rapidly. Despite the differences in the properties of new x-ray imaging detectors, the same radiographic protocols that had been used for radiographic film-screen are used for digital imaging systems, without any review yet. In this study, the image quality and the patient dose in digital imaging of the chest are evaluated and optimized. METHODS: Two digital radiography machines, Shimadzu RDA Speed and Siemens G2107 have been used in this experimental research. Imaging and dose measurement are carried out at different source to phantom distances and kilo-voltages. For measurement of the image quality, a contrast-detail radiography (CDRAD) phantom is used. For evaluation of optimization, the Inverse Image Quality Figure per patient dose squared (IQFinv/E 2) is used. FINDINGS: Evaluation of measured data for optimization shows that for both of these two digital radiography machines, despite of increasing in patent dose, with reducing of kilo-voltage, the IQFinv/E 2 is increased. The maximum values of this parameter for Imam Khomeini and Bu Ali Hospitals are measured 0.0180 and 0.0083, respectively. CONCLUSION: The results of this study indicate that despite the traditional notion of using higher kilo-voltages for chest radiography, with increasing kilo-voltage, the ratio of image quality per patient dose is reduced. So, for optimization of chest radiography, as much as possible the kilo-voltage should be reduced based on the size of patient and clinical purpose.
Influence of Image Metrics When Assessing Image Quality from a Test Object in Cardiac X-ray Systems
Journal of Digital Imaging, 2011
Modern fluoroscopic systems used for invasive cardiology typically acquire digital images in a 1,024 × 1,024 × 12 bits. These images are maintained in the original format while they remain on the imaging system itself. However, images are usually stored using a reduced 512 × 512 × 8-bits format. This paper presents a method for digital analysis of test objects images. The results obtained using image-intensifier and flat-detector systems are given for the original and reduced matrices. Images were acquired using a test object (TO) and a range of polymethyl methacrylate (PMMA) thicknesses from 4 to 28 cm. Adult patient protocols were evaluated for 16–28 cm of PMMA using the image-intensifier system. Pediatric protocols were evaluated for 4–16 cm of PMMA using the flat-detector system. The TO contains disks of various thicknesses to evaluate low contrast sensitivity and a bar pattern to evaluate high-contrast spatial resolution (HCSR). All available fluoroscopic and cine modes were evaluated. Entrance surface air kerma was also measured. Signal-to-noise ratio (SNR) was evaluated using regions of interest (ROI). HCSR was evaluated by comparing the statistical analysis of a ROI placed over the image of the bar pattern against a reference ROI. For both systems, an improvement of approximately 20% was observed for the SNR on the reduced matrices. However, the HCSR parameter was substantially lower in the reduced metrics. Cardiologists should consider the clinical influence of reduced spatial resolution when using the archived images.
Catheterization and cardiovascular interventions : official journal of the Society for Cardiac Angiography & Interventions, 2015
The purpose of this study was to quantify the reduction in patient radiation dose during coronary angiography (CA) by a new X-ray technology, and to assess its impact on diagnostic image quality. Recently, a novel X-ray imaging technology has become available for interventional cardiology, using advanced image processing and an optimized acquisition chain for radiation dose reduction. 70 adult patients were randomly assigned to a reference X-ray system or the novel X-ray system. Patient demographics were registered and exposure parameters were recorded for each radiation event. Clinical image quality was assessed for both patient groups. With the same angiographic technique and a comparable patient population, the new imaging technology was associated with a 75% reduction in total kerma-area product (KAP) value (decrease from 47 Gycm(2) to 12 Gycm(2) , P < 0.001). Clinical image quality showed an equivalent detail and contrast for both imaging systems. On the other hand, the subj...