Recent Patents on Medical Imaging (Discontinued) - Volume 4, Issue 1, 2014

Imaging of the coronary circulation is a critical clinical topic, as only the best knowledge of coronary anatomy allows efficacious and safe coronary interventions [1]. However this is a fast moving field, with new techniques continuously added to the inventory of the cardiologists and with new evidence supporting such techniques continuously accumulating in literature [2]. Such needs largely justify the present monothematic issue which collects up to date information regarding coronary multimodality imaging. The backbone of coronary imaging, coronary angiography, is turning to the trans-radial approach, which offers important advantages both in terms of patient satisfaction and prognosis. This topic is tackled by the review by Rognoni et al. [3], describing the principles of quantitative coronary angiography, a robust method that nowadays allows researchers to assess the impact of the process of atherosclerosis on the lumen of the coronary artery and to establish over time whether an intervention attenuates progression or regression of atherosclerotic disease. In this paper the latest developments of computer assisted assessment of coronary artery luminograms are described and the limitations and difficulties related to interpretation of the angiographic information are discussed. The probably most dynamic field of cardiac and coronary imaging is constituted by the tomographic imaging techniques, among which cardiac and coronary CT-scan and cardiac magnetic resonance are gaining more and more favor to assess cardiac and coronary anatomy as well as the consequences of coronary artery disease, myocardial ischemia and necrosis. CT-scan of coronary arteries are becoming better and better in selecting patients for subsequent coronary interventions with magnificent 3- D reconstructions of the whole coronary tree. These topics are widely discussed by the reviews of Schaffer et al. [4]. Finally, the most exciting evolution has involved the invasive coronary imaging: IVUS, with particular attention to newer development of the technique, that is to say radiofrequency IVUS (virtual histology) for vulnerable coronary plaques detection; fractional flow reserve, which adds to coronary angiography fundamental functional information to guide coronary interventions; and finally optical coherence tomography which with its amazing resolution power can detect stent endothelization with details comparable to an histological examination. These fields are exhaustively covered in the reviews of Barbieri et al. [5] and the paper from the group of Imperial College of London lead by Prof Di Mario [6]. To finally turn the readers’ attention to the clinical point of view, the reviews of Lupi et al. [7] and Nardi et al. [8] address two of the most exciting imaging problems in the clinical cardiology, the search for vulnerable coronary plaques and the detection of cardioembolic sources.

In patients with coronary artery disease, quantitative coronary angiography (QCA) has proved to be a good method for quantification of atherosclerotic plaques since 80’ years. It is used for diagnosis and management in catheterization laboratory of a lot of patients undergoing percutaneous coronary intervention. QCA allows us to assess with dedicated computer software the impact of atherosclerosis on the lumen of the coronary arteries and to establish over time whether an intervention attenuates progression or regression of atherosclerotic disease. Currently, the use of QCA, in catheterization laboratory during percutaneous coronary intervention, is the most used method to investigate precisely the performance of coronary plaque; it, also, allows studying the efficacy of coronary intervention; nevertheless this technique has some limitations and difficulties resulting from the routine use in the evaluation of parameters. This review aims to summarize the principles and the methods used for quantitative coronary angiography with a look on the past and present describing also more recent patents and developments.

Despite the great innovations of non-invasive coronary imaging, coronary angiography still remains the gold standard for the assessment of coronary artery disease (CAD), even if with several limitations. In fact visual assessment of coronary stenosis is convenient and rapid, but often associated with large inter and intra-observer variability, above all in the setting of unstable CAD with complex lesions. Coronary intravascular ultrasound (IVUS) allows accurate tomographic assessment of the coronary lumen and wall. IVUS has several diagnostic applications and is useful for choosing the most appropriate interventional strategy as well as for optimizing percutaneous coronary interventions (PCI) results. The present review focuses on: (1) the role of IVUS to guide therapeutic strategies in complex lesions requiring PCI, (2) IVUS capacity to interrogate borderline coronary stenoses, (3) new perspectives and recent patents for the future of IVUS technology.

Angiography has been the cornerstone tool to assess coronary anatomy, leading to a rapid development of percutaneous revascularization techniques. Despite the widespread dissemination and high reproducibility, angiography alone can only provide a limited analysis of the lumen profile, without the possibility to disclose vessel wall characteristics and the composition of coronary lesions. Intracoronary imaging techniques have been developed to overcome these limitations. Intravascular ultrasound (IVUS) was the first intracoronary imaging modality introduced two decades before, followed more than a decade after by optical coherence tomography (OCT), a light based technology. This article presents the current status in the technical background of OCT imaging in the areas of research development and clinical practice, focusing on future developments of related patent forms.

Computed tomography (CT) is important for the management of many medical illnesses, including coronary artery disease (CAD). However this technique is not free from disadvantages like the exposure to ionizing radiations and to iodinated contrast agents. To overcome these problems, imaging technologies are changing rapidly. New- generation computed tomography scanners (NGCCT) may bring substantial advantages over traditional CT and other currently used imaging methods. These novel tools employ dedicated protocols to shorten imaging times and reduce radiation doses without affecting accuracy. Current CT scanners can very accurately identify severe CAD requiring intervention in most patients, but NGCCT may further benefit imaging for some “difficult” patients like obese patients, patients with high or irregular heart rates, and patients who have high coronary calcium burden or previous stents or bypass grafts. In fact in these patients traditional CT studies often produce suboptimal quality images. Our review presents the current status in the technical background of coronary nuclear tomographic imaging in the areas of clinical practice, and focuses on future developments of related patent forms.

Coronary obstruction by thrombus, triggered by rupture-prone atherosclerotic plaques, is the leading cause of myocardial infarction and accounts for millions of deaths and invasive coronary revascularization procedures. Coronary plaques become vulnerable far before any hemodynamic effect, thus conventional diagnostic techniques based on the angiographic assessment of the coronary vessels or the induction of myocardial perfusion defects or ischemia fail to identify lesions with an adverse clinical evolution. In this review we report about the currently available imaging methods used to investigate atherosclerotic plaques. Different coronary vessel imaging modalities such as coronary angiography, coronary ultrasound, nuclear imaging, magnetic resonance (MRI), computed tomography and other novel currently investigated methods are discussed in our systematic revision. Virtual histology IVUS, elastography and palpography are ultrasound-based methods used to characterize functions of different tissues their harmonic properties or their deformabilities. Optical coherence tomography, near infrared spectroscopy and fluorescence use infrared light to obtain high definition images of the vessel wall or tissue characterization. Intravascular MRI is a promising tool coupling high tissue-specificity imaging of MRI and high definition of intravascular techniques. Moreover recent advances in plaque-specific contrast media for magnetic resonance and positron emission tomography are described, highlighting their strength, pitfalls and future direction of the Research in the field. This article presents the current status in the technical background of intravascular ultrasound and nuclear tomographic imaging in the areas of clinical practice, and focuses on future developments of related patent forms.

Several cardiac diseases, like supra-ventricular arrhythmias, myocardial infarction, left ventricular remodelling with aneurysms and heart valve diseases like mitral valve stenosis, infective endocarditis and prosthetic heart valves predispose to intracavitary thrombus generation, which is the main source for peripheral embolism. Often the main unifying risk factor for cardio-embolism is atrial fibrillation (AF) and many of these cardio-embolic complications are transient ischemic cerebrovascular attacks or strokes with various levels of residual compromise. Cardiac imaging with different techniques and modalities has the potential to effectively stratify thrombo-embolic risk in patients with AF and other cardiac comorbidities. In this review we tried to characterize the current clinical role of different cardiac imaging methods, specifically echocardiography, cardiac computed tomography and cardiovascular magnetic resonance, in identifying cardio-embolic risk factors and guiding antithrombotic therapy, with a particular attention to novel patents and future developments of these techniques.

Recent investigations have shown that diffusion tensor magnetic resonance imaging (DT-MRI) and magnetic resonance spectroscopic imaging (MRSI) provide useful information in diagnosis brain tumor glioma. Therefore, various software have been developed and patented which enable users to overlay multimodal MRI such as DTI-MRI and MRSI for more accurate localization of abnormal lesions. The purpose of this work was to further investigate the potential of these modalities in diagnosis of brain glioma tumors. This paper integrates DTI and MRSI features for differentiating high grade from low grade brain glioma tumors. Three DTI and two MRSI features are extracted from twelve histologically proven brain glioma patients in pre-treatment status. Artificial Neural Network (ANN) classifiers are developed to estimate tumor grades by optimizing Receiver Operating Characteristic (ROC) curves. Our study shows that all DTI and MRSI features are statistically significantly different (P < 0.05) in high grade versus low grade tumors. Low grade tumors have higher mean diffusivity (MD) (1.43±0.21) and lower fractional anisotropy (FA) (0.14±0.04) and relative anisotropy (RA) (0.11±0.03) compared with high grade tumors (1.29±0.47, 0.18±0.12, 0.15±0.10, respectively). Also, Cho/Cr and Cho/NAA ratios of high grade tumors (2.27±1.24, 2.16±1.96) are higher than those of low grade tumors (1.29±0.44, 0.88±0.31). The proposed ANN classifier using FA, RA, Cho/Cr, and Cho/NAA features generates the largest volume under the ROC (the highest accuracy), illustrating that the proposed integration of DTI and MRSI features improves accuracy of tumor grade estimation.

The application of tissue Doppler imaging (TDI) has shown remarkable growth in clinical practice during the past years, especially, in risk stratification of patients with coronary heart disease or heart failure (systolic and diastolic). TDI systolic velocities have been used to detect impaired systolic function in patient with coronary artery disease and heart failure. Important patents were reported in the last years. Main Future development is the application of threedimensional echocardiography with TDI and other technologies derived from TDI, as Strain, Strain Rate and Twodimensional (2D) Strain.