Advances In Noninvasive Imaging Research Articles

Role of multimodality imaging in ischemic and non-ischemic cardiomyopathy

Chronic heart failure (CHF) is a major and growing problem in the western hemisphere, affecting about 5million patients in the United States. In daily practice patients with left ventricular systolic dysfunction (LVSD) and significant angiographic coronary artery disease (CAD) are felt to have an ischemic cardiomyopathy (ICMP) and those without CAD or mild-moderate CAD out of proportion to the extent of LVSD are felt to have a non-ischemic cardiomyopathy (NICMP). Although invasive coronary angiography is the gold standard for the diagnosis of CAD, recent advances in non-invasive imaging have created multiple options for evaluating ICMP and NICMP. This review details the role of cardiac imaging in the diagnosis of ICMP and NICMP and outlines an algorithm of use of non-invasive tests in asymtomatic LVSD and symptomatic heart failure.

Internal Carotid Artery Stenosis: Natural History and Management

Extracranial internal carotid artery stenosis is an important cause of ipsilateral stroke. The natural history of the disease is related to the presence or absence of ipsilateral hemispheric symptoms and the severity of stenosis. Doppler ultrasound is commonly used as a screening test, with more advanced noninvasive imaging studies such as computerized tomography angiography (CTA) and magnetic resonance angiography (MRA) utilized as confirmatory tests if invasive treatment is contemplated. With less-invasive imaging techniques, traditional catheter angiography is rarely indicated for the diagnosis of carotid stenosis. Medical therapy remains the mainstay of treatment in patients with asymptomatic stenosis. Invasive treatment of asymptomatic internal carotid artery stenosis is indicated in a selected group of patients with severe stenosis and life expectancy exceeding 5 years. Invasive treatment is indicated for symptomatic patients with stenosis greater than 70% and in selected patients with recent symptoms and moderate (50% to 69%) stenosis. The risk of ipsilateral stroke is highest in the first few weeks following a presenting symptomatic event. Therefore, when indicated, invasive treatment of symptomatic disease should be considered soon after presenting symptoms to maximize the benefit of the procedure. Carotid endarterectomy (CEA) remains the gold standard for invasive treatment of internal carotid artery disease (symptomatic and asymptomatic). However, based on recent evidence, carotid angioplasty and stenting (CAS) is a valid alternative to CEA in an increasing percentage of patients in need of invasive treatment. Regardless of treatment modality, proper patient selection for invasive treatment remains the single most important factor to insure proper use of available technology.

Hepatic Abscess Masquerading as Cholangiocarcinoma

Purpose: Highlight the importance of surgical intervention when imaging and interventional endoscopic techniques fail to delineate the nature of liver pathology. Methods: We present a thirty-seven year old Vietnamese male who presented with abdominal pain and fever. On admission his LFTs and WBC were normal. One blood culture was positive for K. Pneumoniae. Abdominal imaging revealed dilated intrahepatic ducts in the left hepatic lobe on CT. His alfafetoprotein and CEA were normal while the CA 19-9 was elevated at 879. He underwent an ERCP which showed normal intrahepatic ducts even with selective balloon occlusion cholangiography on the left side. Given the high suspicion of malignancy a left lobectomy with caudate and portal node resection was done using intra-operative ultrasound. Pathology report of the resected lesions however showed multifocal hepatic abscessess with xanthogranulomatous changes,negative for malignancy. The patient made a full recovery and was subsequently discharged. Results: This patient had a liver lesion that was associated with dilated intrahepatic ducts and elevated CA 19-9 levels. There was a high index of suspicion for cholangiocarcinoma and hence he underwent surgical exploration which showed that he had a complex abscess instead. Conclusion: Despite the advances in non invasive imaging and endoscopic intervention,exploratory surgery still has a role in the management of liver lesions.

New Advances in Noninvasive Imaging of the Carotid Artery: CIMT, Contrast-Enhanced Ultrasound, and Vasa Vasorum

Carotid ultrasound measurement of carotid intima-media thickness (CIMT) and detection of plaques is a useful method to better assess cardiovascular disease risk status, especially in those at intermediate risk. We discuss the use CIMT and other emerging techniques such as contrast-enhanced carotid ultrasound imaging in the evaluation of the carotid artery and its value in cardiovascular disease.

The safety of dedicated-team catheter-based diagnostic cerebral angiography in the era of advanced noninvasive imaging.

Given the current high quality and usefulness of noninvasive cerebrovascular imaging, invasive angiographic evaluation of the cerebrovascular system is justified if the procedural risk for a neurologic complication is far below the anticipated benefit. The purpose of this study was to evaluate the safety of diagnostic cerebral angiography provided by a dedicated neurointerventional team in a high-volume university hospital. A consecutive cohort of 1715 patients undergoing diagnostic cerebral angiography at our institution from 2000 to 2008 was retrospectively assessed for incidence of stroke or TIA related to cerebral angiography. In the subgroup of patients (n = 40) who serendipitously underwent DWI within the first 30 days after cerebral angiography, the presence of new DWI hyperintensities found in territories explored during angiography was tabulated. Complications related to the catheter technique and sheath placement were also studied. No stroke or permanent neurologic deficit was seen in any of the 1715 patients undergoing diagnostic neuroangiography. One patient experienced a TIA. Nonneurologic complications without long-term sequelae occurred in 9 patients. Two patients had punctate areas of restricted diffusion in territories that had been angiographically explored. Within a high-volume neurointerventional practice, the risk for neurologic complications related to catheter-based diagnostic cerebral angiography can approach zero. As the absolute number of invasive diagnostic procedures diminishes with time, diagnostic cerebral angiography remains a useful tool while providing a foundation for neuroendovascular interventions, and should preferably be performed in institutions with high-volume operators also capable of managing unanticipated complicating adverse events.

Simulation Devices in Interventional Radiology: Validation Pending

MEDICALsimulationoffersatantaliz-ing breadth and depth of potential fortraining and assessment in interven-tional radiology. It promises to providesolutions to many of the shortcom-ings of our traditional “apprentice-ship” training. Mandatory restric-tions on in-hospital work hours ofresident trainees limit the time avail-able for training and the breadth ofcase material to which the individualtrainee is exposed. At the same time,advances in noninvasive imaginghave reduced trainee exposure to in-vasive procedures. Thus today’s res-ident/trainee has limited opportu-nity to acquire the basic gatewayskills (eg, selective diagnostic cathe-ter angiography), upon which moreadvanced interventional skills arebased (1–3). Medical simulators en-gineered for interventional radiologytraining have the potential to ad-dress these gaps.Simulators introduce a novel capa-bility not only to train but also to es-tablish objective evidence of technicalcompetence during and after training(4–6). Although there is growing evi-dence for their effectiveness, few med-ical procedural simulations have dem-onstrated predictive validity. In otherwords, in very few instances has pro-ficiency with a medical proceduralsimulator been proved to transfer tothe clinical situation. This transfer oftrained skills to patients has now beenshown for simulations of laparoscopicsurgery, colonoscopy, and anesthesia(7–9), but at the time of writing, simi-lar evidence is still being sought forendovascular simulators.In the future, it is likely that simu-lations will be incorporated into certi-fication examinations for interven-tional radiology (6). Although it maybe intuitive that skills learned on sim-ulators should effectively transfer tothe clinical interventional radiologyenvironment, intuition is not evidence.A great deal of work on the develop-ment and validation of interventionalradiology procedural simulations mustbe completed before the inclusion ofsimulations on board, and other statu-tory, certification examinations can beendorsed. Ideally, the development andvalidation of the critical measures ofperformance (metrics) and test items tobe used in simulators should be ac-complished through a joint effort ofprofessional societies and the certify-ing bodies. Only in this way will weensure that the test instrument is com-patible with the educational curricu-lum and that the desired competenciesare being assessed. Input will be re-quired from psychologists and expertsin the subject matter, who will analyzeknowledgeandtaskperformance,break-ing them down into their key compo-nents (10,11). Metrics must be identifiedand used specifically for assessment ofthe learner. By design, this can be madeto occur automatically (by a simulator)within the context of a simulation. Thesubject experts involved in test develop-ment must be appointed with completetransparency by the certifying authori-ties. They must faithfully represent a ro-bust interventional radiology curricu-lum, with all facets of content, skill, andeven geographic diversity.Ideally a single, comprehensive setof procedures, skill sets, and metricsshould be defined and provided asopen source for incorporation into ac-ademic and commercial simulatormodels. Each set of metrics based onthe test items must in turn be vali-dated for its stated purpose. The di-versity of training environments rep-resented within and across radiologysocieties provides an excellent oppor-tunity for careful test validation. Theuse of trainees in transfer-of-trainingstudies will show whether skills ac-quired through simulation indeedtranslate into performance in patients.Subsequent review would demon-strate whether that performance ismaintained. Funding and support forthis work should derive jointly fromindustry, the various specialty societ-ies, and government agencies in theform of public-private partnerships.

Trying to succeed when the right ventricle fails

Compared with the left ventricle, studies of right ventricular failure as a distinct clinical entity have lagged behind. Evolving appreciation of the prognostic significance of right ventricular dysfunction in the heart failure population and advances in noninvasive imaging have provided the impetus for recent investigation into the assessment and management of right ventricular failure. Pulmonary hypertension and attendant right ventricular dysfunction are prevalent in patients with systolic and diastolic heart failure and are associated with poor survival. Simple echocardiographic and MRI indices of right ventricular function relate to prognosis and may also be useful in following response to therapy. Management of acute and chronic right ventricular failure is largely empiric and is focused on treating the underlying cause along with judicious use of diuretics and inotropes. The use of left ventricular assist devices to help treat pulmonary hypertension in heart failure is an emerging strategy in transplant-eligible patients. Right ventricular failure is clinically significant and merits further dedicated study. Parameters of right ventricular dysfunction can be assessed noninvasively. An approach to the management of acute and chronic right ventricular failure should take into consideration novel pharmacologic and device-based therapies.

ICA, kernel methods and nonnegativity: New paradigms for dynamical component analysis of fMRI data

In the last decades, functional magnetic resonance imaging (fMRI) has been introduced into clinical practice. As a consequence of this advanced noninvasive medical imaging technique, the analysis and visualization of medical image time-series data poses a new challenge to both research and medical application. But often, the model data for a regression or generalized linear model-based analysis are not available. Hence exploratory data-driven techniques, i.e. blind source separation (BSS) methods are very popular in functional nuclear magnetic resonance imaging (fMRI) data analysis since they are neither based on explicit signal models nor on a priori knowledge of the underlying physiological process. The independent component analysis (ICA) represents a main BSS method which searches for stochastically independent signals from the multivariate observations. In this paper, we introduce a new kernel-based nonlinear ICA method and compare it to standard BSS techniques. This kernel nonlinear ICA (kICA) overcomes the restrictions of linearity of the mixing process usually encountered with ICA. Dimension reduction is an important preprocessing step for this nonlinear technique and is performed in a novel way: a genetic algorithm is designed which determines the optimal number of basis vectors for a reduced-order feature space representation as an optimization problem of the condition number of the resulting basis. For the fMRI data, a comparative quantitative evaluation is performed between kICA with different kernels, nonnegative matrix factorization (NMF) and other BSS algorithms. The comparative results are evaluated by task-related activation maps, associated time courses and ROC study. The comparison is performed on fMRI data from experiments with 10 subjects. The external stimulus was a visual pattern presentation in a block design. The most important obtained results in this paper represent that kICA and sparse NMF (sNMF) are able to identify signal components with high correlation to the fMRI stimulus, and kICA with a Gaussian kernel is comparable to standard ICA algorithms and even more, it yields spatially focused results.

Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a common and frequently devastating condition, accounting for ≈5% of all strokes and affecting as many as 30 000 Americans each year.1,2 The American Heart Association (AHA) previously published “Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage.”3 Since then, considerable advances have been made in endovascular techniques, diagnostic methods, and surgical and perioperative management paradigms. Nevertheless, outcome for patients with SAH remains poor, with population-based mortality rates as high as 45% and significant morbidity among survivors.4–9 Several multicenter, prospective, randomized trials and prospective cohort analyses have influenced treatment protocols for SAH. However, rapid evolution of newer treatment modalities, as well as other practical and ethical considerations, has meant that rigorous clinical scientific assessment of the treatment protocols has not been feasible in several important areas. To address these issues, the Stroke Council of the AHA formed a writing group to reevaluate the recommendations for management of aneurysmal SAH. A consensus committee reviewed existing data in this field and prepared the recommendations in 1994.3 In an effort to update those recommendations, a systematic literature review was conducted based on a search of MEDLINE to identify all relevant randomized clinical trials published between June 30, 1994, and November 1, 2006 (search terms: subarachnoid hemorrhage , cerebral aneurysm , trial ; Table 1). Each identified article was reviewed by at least 2 members of the writing group. Selected articles had to meet one of the following criteria to be included: randomized trial or nonrandomized concurrent cohort study. Case series and nonrandomized historical cohort studies were reviewed if no studies with a higher level of evidence were available for a particular topic covered in the initial guidelines. These were chosen on the basis of sample size and the relevance of the particular studies to subjects that …

Blunt carotid and vertebral artery injuries

The recognition and treatment of blunt cerebrovascular injuries has dramatically evolved over the past two decades. As imaging technology has improved both with respect to the image quality and acquisition times, its use has become a fundamental diagnostic tool in blunt trauma evaluation. The single greatest radiological advance in the past quarter century has been the refinement and increasing use of computed tomographic imaging for the diagnosis of surgical disease. Paralleling advances in noninvasive imaging, a heightened awareness of blunt cerebrovascular injuries has emerged, and the first screening protocols were developed at high volume trauma centres. Through aggressive screening, these injuries have increasingly been recognised before devastating neurological ischaemia and adverse neurocognitive outcomes. The mainstay of treatment for these injuries is antithrombotic therapy. However, all blunt cerebrovascular injuries require short and long-term follow-up. While the majority of injuries will resolve with medical management, a proportion will require further intervention in order to reduce the risk of subsequent stroke.

Interdepartmental Conflict Management and Negotiation in Cardiovascular Imaging

Although the relationship between cardiologists and radiologists has a thorny history, advanced cardiac imaging technology and the promise of cardiac computed tomography are forcing both specialties back to the negotiation table. These discussions represent an opportunity for better communication, collaboration, and resource allocation. The authors address the aspects of interdepartmental conflict management and negotiation through their radiology department's ongoing efforts to provide high-quality advanced noninvasive cardiovascular imaging services at a large academic institution. The definition and causes of conflict are defined, with a specific focus on noninvasive cardiovascular imaging, followed by a description of steps used in the negotiation process. The authors encourage radiologists to entertain an open dialogue with cardiology, because in many cases, both sides can benefit. The benefits of a negotiated outcome include minimizing internal competitors, incorporating cardiologists' expertise to cardiac imaging algorithms, and more effective training opportunities.

Noninvasive Imaging Advances for Osteoporosis

Noninvasive Imaging Advances for Osteoporosis

Peripheral arterial disease: Epidemiology, natural history, diagnosis and treatment

Lower extremity peripheral arterial disease (PAD) affects approximately 10% of the American population, with 30% to 40% of these patients presenting with claudication symptoms. The prevalence of PAD increases with age and the number of vascular risk factors. More importantly, it is a marker of atherosclerotic disease burden, and is associated with increased mortality from cardiovascular and cerebrovascular causes. There have been recent advances in noninvasive imaging, endovascular approaches for revascularization, and aggressive risk factor management for prevention of cardiac and cerebrovascular complications in PAD. There is now a trend toward aggressive risk factor modification and endovascular revascularization for most patients, with surgical interventions reserved for certain situations only. In the present article, a systematic review is presented, focusing on the key aspects of the disease epidemiology, presentation, natural history, diagnosis and available management options.

Brain Imaging and Behavior: Progress and Opportunities

The emergence of advanced noninvasive medical imaging directed toward the in vivo investigation of the human brain has revolutionized the study of brain behavior relationships in healthy individuals as well as in those with illnesses affecting neural structure and function. Computer-assisted tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) are landmark technical advances that forever changed the clinical neuroscience disciplines of neurology, neurosurgery, psychiatry and neuropsychology, as well as radiology itself, as they entered widespread use during the 1970s (CT) and 1980s (PET and MRI). These tools were rapidly applied to clinical research studies of major brain disorders from strokes and tumors to dementia and schizophrenia. In the post-millennial era, high field MRI now yields unprecedented information about brain morphology with spatial resolution at the millimeter or sub-millimeter scale. Numerous MR techniques can be tuned to reveal particular normal or lesional tissue contrast. T2-weighted and fluidattenuated inversion recovery MR scans have become an accepted surrogate marker for quantifying demyelinating lesion burden in patients with multiple sclerosis in clinical trials and are also widely used to quantify microvascular lesion burden. These techniques have also been used to study cognitive correlates of specific brain disorders. MR and PET are moving toward becoming accepted biomarkers for detection and treatment monitoring in Alzheimer’s disease and other dementias. Fluorodeoxyglucose PET assessment of metabolism was recently approved by Medicare for use in the differential diagnosis of dementia in complex or ambiguous cases. Advanced molecular imaging probes targeting specific receptors, transporters or pathophysiological features of disease also show great promise for early diagnosis and as a biomarker for treatment response. These and other related tools will play a major role in the new era of personalized medicine. A remarkable recent example is the advent of ligands for in vivo labeling of brain amyloid, a key molecular hallmark of Alzheimer’s disease involved in plaque formation. Use of blood oxygen level dependent contrast functional MRI (fMRI) to assess brain activation patterns has been enormously successful as a research tool since the milestone studies in the early 1990s. Arterial spin labeling fMRI techniques now permit quantitative determination of cerebral blood flow without ionizing radiation. Evidence of fMRI’s maturity is the recent provision of a current procedural terminology code for reimbursement when used as a clinically indicated mapping procedure for neurosurgical planning. Clinical fMRI continues to advance, for example, in combination with transient disruption approaches such as repetitive transcranial magnetic stimulation and intraoperative stimulation mapping. MR spectroscopy and spectroscopic imaging address the neurochemical composition of brain tissue. Magnetic resonance spectroscopic imaging is now capable of rapidly generating quantitative maps of major metabolites that serve as markers for neuronal integrity and also yield information regarding metabolism, membrane breakdown and inflammation. Another remarkable MR technique, diffusion weighted imaging, can reveal acute strokes as they are evolving and influence treatment strategy in near real time. A related technique, diffusion tensor imaging (DTI), permits visualization of fiber tracts indicating the location and integrity of connectivity patterns within major neural circuits subserving Brain Imaging and Behavior (2007) 1:1–2 DOI 10.1007/s11682-007-9005-0

Salivary gland imaging in Sjogren’s syndrome

Sjogren’s syndrome (SS) is a systemic connective tissue disease characterized by a progressive immune-mediated impairment of the exocrine glands. The high prevalence in the general population of sicca and other symptoms mimicking SS has increased the need for accurate tools in its diagnosis. Imaging may be substantially helpful in this regard, as well as in the assessment of acute and chronic complications of the disease. A future application of salivary imaging in SS may be guiding therapeutics by enabling radiographic monitoring of treatment responsiveness. This review of salivary gland imaging in SS summarizes the types of information yielded by currently available modalities and suggests their proper clinical application. It emphasizes recent advances in noninvasive imaging, including magnetic resonance sialography, ultrasonography and nuclear medicine techniques.

Asymptomatic carotid stenosis: what to do

Patients with asymptomatic carotid stenosis are at increased vascular risk but optimal treatment is controversial. We reviewed the current evidence for medical and surgical intervention in these patients. Optimal medical treatment is the most important aspect of management of patients with asymptomatic carotid stenosis. On the basis of previous trials, endarterectomy is only of overall benefit in men, and this benefit may now be obviated by improved medical treatment. There is insufficient evidence to advocate the routine use of carotid angioplasty or stenting in patients with asymptomatic stenosis. Inaccuracy in the measurement of carotid stenosis may contribute to conflicting estimates of stroke risk in relation to the degree of asymptomatic stenosis. Advances in noninvasive imaging of plaque morphology and inflammation and the detection of microembolic signals may help to risk stratify patients but data on clinical usefulness are lacking. Absolute benefit from endarterectomy for asymptomatic carotid stenosis is small, but can sometimes be justified in men. Further research is required to determine long-term benefit in women and to risk stratify patients, particularly in the light of advances in medical treatment.

CCS/CAR/CANM/CNCS/CanSCMR joint position statement on advanced noninvasive cardiac imaging using positron emission tomography, magnetic resonance imaging and multidetector computed tomographic angiography in the diagnosis and evaluation of ischemic heart disease – executive summary

Over the past few decades, advanced imaging modalities with excellent diagnostic capabilities have emerged. The aim of the present position statement was to systematically review existing literature to define Canadian recommendations for their clinical use. A systematic literature review to 2005 was conducted for positron emission tomography (PET), multidetector computed tomographic angiography and magnetic resonance imaging (MRI) in ischemic heart disease. Papers that met the criteria were reviewed for accuracy, prognosis data and study quality. Recommendations were presented to primary and secondary panels of experts, and consensus was achieved. Indications for PET include detection of coronary artery disease (CAD) with perfusion imaging, and defining viability using fluorodeoxyglucose to determine left ventricular function recovery and/or prognosis after revascularization (class I). Detection of CAD in patients, vessel segments and grafts using computed tomographic angiography was considered class IIa at the time of the literature review. Dobutamine MRI is class I for CAD detection and, along with late gadolinium enhancement MRI, class I for viability detection to predict left ventricular function recovery. Imaging must be performed at institutions and interpreted by physicians with adequate experience and training. Cardiac imaging using advanced modalities (PET, multidetector computed tomographic angiography and MRI) is useful for CAD detection, viability definition and, in some cases, prognosis. These modalities complement the more widespread single photon emission computed tomography and echocardiography. Given the rapid evolution of technology, initial guidelines for clinical use will require regular updates. Evaluation of their integration in clinical practice should be ongoing; optimal use will require proper training. A joint effort among specialties is recommended to achieve these goals.

Cross-sectional vascular imaging with CT and MR angiography

Both CTA and MRA are highly advanced noninvasive vascular imaging modalities. CTA is more readily available with approximately 30,000 installed systems worldwide. MDCTA offers faster scan times than ceMRA and offers higher resolution. Disadvantages are the use of ionizing radiation and nephrotoxic contrast agents. Calcified plaques occasionally can make the determination of ruminai patency difficult. MRA does not have this problem, but offers somewhat inferior spatial resolution and is unsuitable for the evaluation of the patency of stented vessels.

Advanced Non-invasive Imaging Techniques—Nuclear Imaging

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Clinical examination of the heart

Abstract Examination of the heart is an important clinical skill. Despite advances in non-invasive imaging, no other investigation (ECG, radiology, echocardiography or radioisotope scanning) has supplanted clinical examination as a means of: •making an initial anatomical diagnosis •rapidly assessing cardiac function and progress at the bedside. The skill of examination is best learned at the bedside from a practitioner already experienced in it, and it is best perfected by practice.