PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 8675424

A model for the modulation transfer function of cardiovascular x-ray systems.

M R Rezaee·P M van der Zwet·J J Gerbrands·J H Reiber
View original source ↗Export metadata ↓

Abstract

RATIONALE AND OBJECTIVES: To derive a theoretical model for the modulation transfer function (MTF) of the complete imaging chain of a cardiovascular x-ray system. A sufficiently accurate MTF model may be used in quantitative coronary arteriographic applications to decrease the systematic overestimation of small coronary vessels. The model could be used to restore blurred images in image restoration applications and also may be used for image quality assurance measurements. METHODS: Digital images of a step wedge phantom were acquired at different modes (5-, 7-, and 9-inch) of the image intensifier and at different kilovolt levels of the x-ray generator. From these images the MTFs that were used to estimate the parameters of the model were assessed. RESULTS: The total MTF of the cardiovascular x-ray imaging chain consisting of image intensifier, video camera, optical elements, and analog/digital converter can be modeled by the simple formula MTF = e-(w/f)R, where w is the frequency in linepairs per millimeter. The constants frequency f and the device index n are parameters that can be derived for an individual x-ray system using the phantom. In this formula, the contribution from the focus of the x-ray source has been excluded. The mean square error (MSE) between the measured values and those assessed from the theoretical model of the MTF for the horizontal direction was found to be equal to 0.00003 for the 5-inch mode of image intensifier, and for the vertical resolution at the 9-inch mode this MSE was equal to 0.00038. In addition, we have demonstrated that the contributions of the video camera and the image intensifier to the total MTF can be replaced by an imaginary electron-optical device. CONCLUSION: An accurate representation for the MTF of a cardiovascular x-ray system has been derived. This MTF model can be used in x-ray image quality assurance measurements and in quantitative image processing applications.

Explore related subjects

Cardiovascular SystemFourier AnalysisHumansImage Processing, Computer-AssistedModels, TheoreticalOptical DevicesPhantoms, ImagingRadiographic Image EnhancementJournal Article

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M R Rezaee, P M van der Zwet, J J Gerbrands, J H Reiber. 1996. A model for the modulation transfer function of cardiovascular x-ray systems.. https://doi.org/10.1097/00004424-199603000-00007

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2006

Sleep apnoea and hypertension: role of chemoreflexes in humans.

The link between sleep apnoea and systemic hypertension in humans is well documented. However, a direct causal association between the two diseases independent of comorbidities has been difficult to establish. Comorbidities clearly play an important role in this strong relationship; however, new findings also suggest that sleep apnoea is an independent risk factor for hypertension. This relationship appears to be at least in part a result of chronically elevated sympathetic activity, and therefore manifests as a neurally mediated hypertension. Although the mechanism(s) for this causal relationship of sleep apnoea to hypertension remains ill defined, a growing body of literature suggests that autonomic dysfunction, mediated by abnormal chemoreflex control of sympathetic activity, is a potential mechanism. Abnormal chemoreflex responses to both acute and chronic apnoea or hypoxia have been demonstrated. Hypothesized mechanisms by which chemoreflex dysfunction may contribute to chronically elevated sympathetic tone and ultimately hypertension are explored in this review. Thus, this review focuses on the current evidence linking chemoreflex function to obstructive sleep apnoea and systemic hypertension in humans and provides an analysis of these data and their implications.

Cardiovascular System↗
PubMed2006

Gender differences in drug responses.

This review summarizes gender differences (GDs) in drug response. Although GDs have been described both in pharmacodynamics and pharmacokinetics, their role in clinical practice is not yet completely elucidated. The evidence that women have been less enrolled in clinical trials and that a gender-specific analysis usually is not included in the evaluation of results, contributes largely to this uncertainty. Consequently, adverse drug reactions (ADRs) are still higher in females than in males. Since sex is a fundamental biological variable that cannot be discounted, GDs in pharmacology have to be considered in order to improve drug safety efficacy and to optimize medical therapy both in men and women.

Cardiovascular System↗