Vessel masking improves densitometric myocardial perfusion assessment

Vesselness-constrained robust PCA for vessel enhancement in x-ray coronary angiograms

Effective vessel enhancement in x-ray coronary angiograms (XCA) is essential for the diagnosis of coronary artery disease, yet challenged by complex background structures of varying intensities as well as motion patterns. As a typical layer-separation method, robust principal component analysis (RPCA) has been proposed to automatically improve vessel visibility via sparse and low-rank decomposition. However, the attenuated motion of vessels in x-ray angiograms leads to the unsatisfactory vessel enhancement performance of the decomposition framework. To address this problem, we propose a vesselness-constrained RPCA method (VC-RPCA), where a vessel-like appearance prior is incorporated into the layer separation framework for accurate vessel enhancement. We first pre-compute the vessel-like appearance prior based on a Frangi filter to highlight the curvilinear structures. After removing large-scale background structures via a morphological closing operation, we then integrate the pre-computed vessel-like appearance prior into a low-rank decomposition framework to separate the fine vessel structures. In addition, we develop an adaptive regularization strategy that imposes structured-sparse constraints to solve the scale issue and capture vessels without salient motion. The proposed method was validated on 13 clinical XCA sequences containing 777 images in total. The contrast-to-noise ratio, Dice coefficient and area under the ROC curve were employed for quantitative evaluation of the vessel enhancement performance. Experiments show that (1) the adaptive regularization strategy helps to obtain a complete coronary tree in the separated vessel layer; (2) our low-rank decomposition framework is robust against false positive/negative responses of the Frangi filter; and (3) the proposed VC-RPCA is computationally fast and outperforms other state-of-the-art RPCA methods for vessel enhancement in the full-contrast and low-contrast scenarios. The results demonstrate that the proposed VC-RPCA can accurately separate coronary arteries and prominently improve vessel visibility in x-ray angiograms.

Relationship between early myocardial reperfusion assessed by videodensitometry and late left ventricular function. Results following invasive treatment of acute myocardial infarction

Introduction: It is known that there is a relationship between myocardial perfusion and left ventricular function. Aim: The aim of the current study was to examine the relationship between myocardial reperfusion as assessed by videodensitometry on coronary angiograms following invasive treatment of ST elevation myocardial infarction and magnetic resonance imaging-derived late left ventricular function. Method: The study included 25 patients with ST elevation myocardial infarction. A quantitative parameter of myocardial (re)perfusion was calculated by the ratio of maximal density (Gmax) and the time to reach maximum density (Tmax) following invasive treatment. Magnetic resonance imaging was performed 387±262 days after ST elevation myocardial infarction for the evaluation of left ventricular function in all cases. Results: Significant correlations were demonstrated between left ventricular ejection fraction and Gmax(r = 0.40, p = 0.05) and Gmax/Tmax(r = 0.41, p = 0.04) following vessel masking. Conclusions: The results demonstrate significant relationship between densitometric Gmax/Tmaxand late left ventricular function following ST elevation myocardial infarction. Orv. Hetil., 2014. 155(5), 187–193.

Diaphragm border detection in coronary X-ray angiographies: New method and applications

X-ray angiography is widely used in cardiac disease diagnosis during or prior to intravascular interventions. The diaphragm motion and the heart beating induce gray-level changes, which are one of the main obstacles in quantitative analysis of myocardial perfusion. In this paper we focus on detecting the diaphragm border in both single images or whole X-ray angiography sequences. We show that the proposed method outperforms state of the art approaches. We extend a previous publicly available data set, adding new ground truth data. We also compose another set of more challenging images, thus having two separate data sets of increasing difficulty. Finally, we show three applications of our method: (1) a strategy to reduce false positives in vessel enhanced images; (2) a digital diaphragm removal algorithm; (3) an improvement in Myocardial Blush Grade semi-automatic estimation.

Videodensitometric time-density curve change after alcohol septal ablation of obstructive hypertrophic cardiomyopathy

A recently developed computerized method for estimation of myocardial perfusion, based on the analysis of the time-density curves, is demonstrated to assess myocardial blush over a selected myocardial region of interest in a patient with obstructive hypertrophic cardiomyopathy before and after alcohol septal ablation.

Aortic valve stenosis is associated with reduced myocardial perfusion as assessed by videodensitometry in coronary angiograms

Aortic valve stenosis may be accompanied by angina despite coronary arteries free of significant stenosis due to microvascular abnormalities. Aims: The aim of the current study was to test whether densitometry-derived myocardial perfusion on coronary angiogram is reduced in patients with aortic valve stenosis. Methods: The study comprised 20 patients with aortic valve stenosis (mean transvalvular gradient: 47.4±15.2 mm Hg) and 30 control subjects without significant epicardial coronary artery stenosis. A quantitative parameter of myocardial perfusion was calculated by the ratio of maximal density (Gmax) and time to reach maximum density (Tmax) on time–density curves in regions of interest of each coronary artery on coronary angiograms. Results: Mean three-vessel Gmax/Tmax proved to be significantly lower in patients with aortic valve stenosis compared to control subjects (2.55±1.02 1/sec vs. 3.39±1.09 1/sec, p<0.01). Conclusions: Reduced Gmax/Tmax values indicative of myocardial perfusion abnormalities as measured by densitometry on coronary angiograms could be demonstrated in patients with aortic valve stenosis compared to controls. Orv. Hetil., 2012, 153, 1256–1262.