Search PubMed⌕ Search

Biomedical subjects

Christoph R Becker

Publications and source records attributed to Christoph R Becker.

At least 37 records · Page 2Linked to original sources
PubMed2006

Clinical value of MDCT in the diagnosis of coronary artery disease in patients with a low pretest likelihood of significant disease.

OBJECTIVE: The aim of this study was to evaluate the clinical value of MDCT in the diagnosis of coronary artery disease in a population having a low pretest likelihood of significant disease. SUBJECTS AND METHODS: Sixty-four patients with suspected coronary artery disease and a low pretest likelihood of significant disease according to the criteria of the American Heart Association underwent both MDCT of the heart and quantitative conventional coronary angiography (QCA). MDCT examinations were performed on a 16-MDCT scanner. CT data sets were evaluated on a per-patient basis and a per-segment basis and were classified as indicating no disease, nonsignificant disease (stenoses </= 50%), or significant disease (stenoses > 50%). Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of 16-MDCT in the detection or exclusion of significant and nonsignificant coronary artery disease were evaluated on both per-patient and per-segment bases. RESULTS: Regarding the success rate of 16-MDCT, 94% (60/64) of patients and 92% (388/420) of vessel segments were of sufficient quality for diagnosis. In the remaining 60 patients evaluated, QCA revealed significant coronary artery disease, nonsignificant disease, and no disease in 8.3% (5/60), 75.0% (45/60), and 16.7% (10/60) of cases, respectively, on a per-patient basis, and in 1.3% (5/388), 23.2% (90/388), and 75.5% (293/388) of cases, respectively, on a per-segment basis. The sensitivity, specificity, NPV, and PPV of 16-MDCT for the detection of significant coronary artery disease were 80.0%, 94.5%, 98.1%, and 57.1%, respectively, on a per-patient basis, and 80.0%, 99.2%, 99.7%, and 57.1% on a per-segment basis. CONCLUSION: In a population having a low pretest likelihood of significant coronary artery disease, 16-MDCT shows a moderate to high sensitivity and high NPV for the detection or exclusion of significant disease, but has a somewhat reduced PPV compared with QCA.

Adult↗
PubMed2006

Accuracy of 64-MDCT in the diagnosis of ischemic heart disease.

OBJECTIVE: The aim of this study was to evaluate the potential clinical value of a new generation of 64-MDCT systems with that of invasive coronary angiography in the diagnosis of coronary artery disease (CAD). SUBJECTS AND METHODS: Seventy-two consecutive patients with known or suspected CAD underwent both 64-MDCT and quantitative coronary angiography (QCA). A CT system with acquisition of 64 slices per gantry rotation was used with a spatial resolution of 0.4 x 0.4 x 0.4 mm and a gantry rotation time of 330 milliseconds. Sensitivity, specificity, and diagnostic accuracy of 64-MDCT in the detection or exclusion of CAD were evaluated on both a per patient and a per segment basis. RESULTS: Sixty-eight of 72 coronary CT angiograms (CTAs) (94%) were of diagnostic image quality. QCA showed significant CAD (i.e., one or more stenoses in > 50%) in 57% (39/68) and nonsignificant disease or healthy CTAs in 43% (29/68) of the patients. Sensitivity, specificity, and the negative predictive value (NPV) of 64-MDCT per patient were 97%, 79%, and 96%, respectively. Per segment, 923 of 1,020 coronary artery segments were assessable (90%). For the detection of stenoses of more than 50% and more than 75% per segment, 64-MDCT showed a sensitivity of 82% and 86%, respectively. Per segment, specificity and NPV were as high as 95% and 97%, respectively. CONCLUSION: In clinical routine, coronary CTA will primarily be used for risk stratification on a per patient basis. In the present study, coronary 64-MDCT showed a high diagnostic accuracy on both per patient and per segment analyses.

Adult↗
PubMed2006

Contrast-Induced Nephropathy (CIN) Consensus Working Panel: executive summary.

With the advances made in radiology and cardiology, greater numbers of patients are expected to undergo exposure to iodinated contrast media in the years to come. Contrast-induced nephropathy (CIN) accounts for a significant number of cases of hospital-acquired renal failure, with adverse effects on prognosis and healthcare costs. The CIN Consensus Working Panel is an international multidisciplinary group convened to address the challenges of CIN. The group reviewed 865 published papers, chosen for potential relevance from a comprehensive literature search that identified over 4000 references. The results were used to compile reviews covering the epidemiology and pathogenesis of CIN, baseline renal function measurement, risk assessment, identification of high-risk patients, contrast medium use, and preventive strategies. In this executive summary, consensus statements and an algorithm for the risk stratification and management of CIN are presented.

Contrast Media↗
PubMed2005

Quantification of obstructive and nonobstructive coronary lesions by 64-slice computed tomography: a comparative study with quantitative coronary angiography and intravascular ultrasound.

OBJECTIVES: The aim of the present study was to determine the diagnostic accuracy of 64-slice computed tomography (CT) to identify and quantify atherosclerotic coronary lesions in comparison with catheter-based angiography and intravascular ultrasound (IVUS). BACKGROUND: Currently, the ability of multislice CT to quantify the degree of coronary artery stenosis and dimensions of coronary plaques has not been evaluated. METHODS: We included 59 patients scheduled for coronary angiography due to stable angina pectoris. A contrast-enhanced 64-slice CT (Senation 64, Siemens Medical Solutions, Forchheim, Germany) was performed before the invasive angiogram. In a subset of 18 patients, IVUS of 32 vessels was part of the catheterization procedure. RESULTS: In 55 of 59 patients, 64-slice CT enabled the visualization of the entire coronary tree with diagnostic image quality (American Heart Association 15-segment model). The overall correlation between the degree of stenosis detected by quantitative coronary angiography compared with 64-slice CT was r = 0.54. Sensitivity for the detection of stenosis <50%, stenosis >50%, and stenosis >75% was 79%, 73%, and 80%, respectively, and specificity was 97%. In comparison with IVUS, 46 of 55 (84%) lesions were identified correctly. The mean plaque areas and the percentage of vessel obstruction measured by IVUS and 64-slice CT were 8.1 mm2 versus 7.3 mm2 (p < 0.03, r = 0.73) and 50.4% versus 41.1% (p < 0.001, r = 0.61), respectively. CONCLUSIONS: Contrast-enhanced 64-slice CT is a clinically robust modality that allows the identification of proximal coronary lesions with excellent accuracy. Measurements of plaque and lumen areas derived by CT correlated well with IVUS. A major limitation is the insufficient ability of CT to exactly quantify the degree of stenosis.

Aged↗
PubMed2005

Assessment of myocardial perfusion and viability from routine contrast-enhanced 16-detector-row computed tomography of the heart: preliminary results.

To assess the diagnostic accuracy of 16-detector-row computed tomography (16DCT) of the heart in the assessment of myocardial perfusion and viability in comparison to stress perfusion magnetic resonance imaging (SP-MRI) and delayed-enhancement magnetic resonance imaging (DE-MRI). A number of 30 patients underwent both 16DCT and MRI of the heart. Contrast-enhanced 16DCT data sets were reviewed for areas of myocardium with reduced attenuation. Both CT and MRI data were examined by independent reviewers for the presence of myocardial perfusion defects or myocardial infarctions (MI). Volumetric analysis of the hypoperfusion areas in CT and the infarct sizes in DE-MRI were performed. According to MRI, myocardial infarctions were detected in 11 of 30 cases, and perfusion defects not corresponding to an MI were detected in six of 30 patients. CTA was able to detect ten of 11 MI correctly (sensitivity 91%, specificity 79%, accuracy 83%), and detected three of six hypoperfusions correctly (sensitivity 50%, specificity 92%, accuracy 79%). Assessing the volume of perfusion defects correlating to history of MI on the CT images, a systematic underestimation of the true infarct size as compared to the results of DE-MRI was found (P<0.01). Routine, contrast-enhanced 16-detector row CT of the heart can detect chronic myocardial infarctions in the majority of cases, but ischemic perfusion defects are not reliably detected under resting conditions.

Adult↗
PubMed2005

Estimation of cardiac event risk by MDCT.

Coronary calcifications are specific markers for coronary atherosclerosis. The amount of coronary calcium is related to the likelihood of vulnerable plaques. Vulnerable plaques may rupture and may result in sudden coronary thrombus formation, occlusion, ischemia and ventricular fibrillation and finally cardiac death. Therefore, it is reasonable to believe that the risk of cardiac events can be assessed by the quantification of the extent of coronary calcium. However, until now, the predictive value of coronary calcium and the advantage over conventional risk factors has not yet been proven by any prospective cohort study. In practice uncertainty exists in the group of patients with an intermediate risk for cardiac events. In this particular cohort it is likely that the assessment of coronary atherosclerosis may help in the decision to initiate or discard a specific therapy. For this purpose it has been suggested to replace the Framingham age score by a score corrected by the amount of coronary calcium. Follow-up investigations may be helpful in the short term to determine the efficiency of different therapeutical options. To determine a significant progression of the amount of coronary calcium, the absolute mass should be determined in a period of 1 year.

Age Factors↗
PubMed2005

Coronary CT angiography in symptomatic patients.

The currently best available spatial and temporal resolution for retrospectively ECG gated coronary multi-detector-row CT angiography is 0.4 mm and 165 ms, respectively. These acquisition parameters are already rather close to cardiac catheter. Studies so far compared non-invasive coronary CT and convention angiography for the detection of coronary artery stenoses. The most promising result reported by all authors was the high negative predictive value of the CTA. It now needs to be determined if CTA is a reliable tool to rule out coronary artery stenoses in a patient cohort with low likelihood of CAD, such as those with atypical chest pain or ambiguous stress test. CTA may furthermore establish as a rapid and widely available tool to detect vulnerable plaques or intracoronary thrombus in patients with acute coronary syndrome and unstable angina. In patients with chronic stable angina, tools that determine myocardial ischemia under stress such as SPECT and MRI are probably better suited to determine the relevance of coronary artery stenoses. In this particular cohort, by displaying the extent and morphology of coronary atherosclerosis, CTA may help to direct the therapy to either intervention or surgery.

Angina Pectoris↗
PubMed2005

Use of iso-osmolar nonionic dimeric contrast media in multidetector row computed tomography angiography for patients with renal impairment.

OBJECTIVES: We wanted to determine the rate of contrast-induced nephropathy (CIN) caused in patients with renal impairment undergoing multidetector row computed tomography (MDCT) angiography with intravenous administration of iso-osmolar dimeric contrast media (iodixanol). MATERIALS AND METHODS: The first consecutive 100 patients referred to CT with a serum creatinine level (SCr) between 1.5 and 6 mg/dL were enrolled in the study. Serum creatinine also was determined on days 3 and 7 after the intravenous administration of 100 mL of iodixanol 270 with 5 mL/s. A CIN was considered if variation of SCr on day 3 was >0.5 mg/dl above baseline. RESULTS: Nine patients developed a CIN after MDCT angiography; 7 of them recovered completely by day 7, and the remaining 2 showed elevated SCr on day 7 but did not develop renal failure during their hospital stay. CONCLUSIONS: MDCT angiography performed in patients with impaired renal function with iodixanol may result in CIN but complete recovery is probable.

Aged↗
PubMed2004

Flat panel computed tomography of human ex vivo heart and bone specimens: initial experience.

The aim of this technical investigation was the detailed description of a prototype flat panel detector computed tomography system (FPCT) and its initial evaluation in an ex vivo setting. The prototype FPCT scanner consists of a conventional radiographic flat panel detector, mounted on a multi-slice CT scanner gantry. Explanted human ex vivo heart and foot specimens were examined. Images were reformatted with various reconstruction algorithms and were evaluated for high-resolution anatomic information. For comparison purposes, the ex vivo specimens were also scanned with a conventional 16-detector-row CT scanner (Sensation 16, Siemens Medical Solutions, Forchheim, Germany). With the FPCT prototype used, a 1,024x768 resolution matrix can be obtained, resulting in an isotropic voxel size of 0.25x0.25x0.25 mm at the iso-center. Due to the high spatial resolution, very small structures such as trabecular bone or third-degree, distal branches of coronary arteries could be visualized. This first evaluation showed that flat panel detector systems can be used in a cone-beam computed tomography scanner and that very high spatial resolutions can be achieved. However, there are limitations for in vivo use due to constraints in low contrast resolution and slow scan speed.

Foot Bones↗
PubMed2004

CT measurement of coronary calcium mass: impact on global cardiac risk assessment.

Coronary calcium mass percentiles can be derived from electron beam CT as well as from multidetector-row CT of all manufacturers. Coronary calcium mass may serve as a more individualized substitute for age for cardiac risk stratification. The aim was to investigate the potential impact of CT coronary calcium mass quantification on cardiac risk stratification using an adjusted Framingham score. Standardized coronary calcium mass was determined by multidetector-row CT in a total of 1,473 patients (1,038 male, 435 female). The impact on risk stratification of replacing the traditional Framingham age point score by a point score based on calcium mass relative to age was tested. Any coronary calcium found in males in the age group of 20-34 years and females in the age group of 20-59 years results in an increase of the Framingham score by 9 and 4-7 points, respectively. Only in males 65 years of age and older, none or minimal amounts of coronary calcium decrease the Framingham score by three points. The coronary calcium mass and age-related scoring system may have impact on the reassignment of patients with an intermediate Framingham risk to a lower or higher risk group.

Adult↗
PubMed2004

Relation of coronary calcium scores by electron beam tomography to obstructive disease in 2,115 symptomatic patients.

This angiographically correlated study reports on, for the first time, age- and gender-based distribution of the volumetric calcium score in a large group of patients with suspected coronary artery disease. Volumetric calcium data predicted significant coronary artery disease (>/=50% lumen diameter stenosis) as well as the traditional Agatston score. Exclusion of any calcium was highly accurate in ruling out obstructive disease in symptomatic subjects >/=50 years of age.

Adult↗
PubMed2004

Past, present, and future perspective of cardiac computed tomography.

In the United States, more than 1 million diagnostic invasive coronary angiograms are performed annually, and in about 50% the investigation is followed by an interventional procedure. The remaining symptomatic patients after angiography are treated conservatively or by bypass graft surgery. In recent decades coronary angiography has advanced to a fast and safe investigation. Nevertheless, in particular, patients are well aware of the small but not negligible risk of complications and the discomfort of the invasive procedure. In addition to electrocardiogram (EKG) or ultrasound stress test and thallium scintigraphy, there is further need for another noninvasive method that displays the morphology of the coronary arteries in a way that would allow the triage of patients with suspicion of coronary artery disease (CAD) for a conservative, interventional, or surgical treatment.

Coronary Angiography↗
PubMed2004

Advances in cardiac CT imaging: 64-slice scanner.

BACKGROUND: Clinical progress by the development of multi-slice CT (MSCT) technology beyond 16 slices can more likely be expected from further improved spatial and temporal resolution rather than from a mere increase in the volume coverage speed. We present an evaluation of a recently introduced 64-slice CT (64SCT) system, which makes use of a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot) to double the number of simultaneously acquired slices. MATERIALS AND METHODS: A recently introduced 64SCT system (SOMATOM Sensation 64, Siemens Medical Solutions, Forchheim, Germany) is being described and tested in first clinical practice, applying the following parameters: z-flying focal spot technology, 64 x 0.6 mm slices; spatial resolution, 0.4 x 0.4 x 0.4 mm; gantry rotation time, 330 ms; temporal resolution, 83-165 ms. Various phantom studies and first clinically implemented protocols are being described, to evaluate the full spectrum of possible applications for this scanner type, with a focus on cardiac imaging. RESULTS: ECG-gated cardiac scanning with this 64-slice CT system benefits clearly from both the improved temporal resolution and improved spatial resolution. These benefits enable a more reliable assessment of mixed plaques, due to reduced partial-voluming and beam-hardening artefacts caused by calcifications, and holds great promise for the reliable assessment of in-stent stenoses, as stent lumen visibility is clearly improved as compared to earlier MSCT systems. With the increased volume coverage and acquisition speed of the 64SCT system, a comprehensive emergency protocol of the thorax becomes feasible within an acceptable breath-hold time, performing an ECG-gated CT angiography of the complete thoracic vasculature. This protocol enables a detailed assessment of the thoracic aorta, the pulmonary arteries and the coronary arteries in one single examination. CONCLUSIONS: 64SCT Cardiac imaging provides an increased spatial resolution with an isotropic voxel size of 0.4 mm and an improved temporal resolution of 83-165 ms. These benefits hold great promise especially for fast-moving organs requiring detailed imaging, such as the heart and coronary arteries.

Calcinosis↗
PubMed2004

Multidetector-row computed tomography and magnetic resonance imaging of atherosclerotic lesions in human ex vivo coronary arteries.

In the present study, we tested the ability of multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI) to identify and retrospectively characterize atherosclerotic lesions in human ex vivo coronary arteries. Thirteen ex vivo hearts were studied with MDCT and MRI. MDCT-images were obtained with an isotropic voxel size of 0.6mm(3). MR images were obtained with an in-plane resolution of 195 microm and 3mm slice thickness. All images were matched with histopathology sections. For both modalities, the sensitivity for the detection of any atherosclerotic lesion was evaluated, and a retrospective analysis of plaque morphology according to criteria defined by the American Heart Association (AHA) was performed. At histopathology, 28 atherosclerotic lesions were found. 21 and 23 of these lesions were identified by MDCT and MRI, respectively. Both modalities detected a small number of false-positive lesions. After retrospective matching with histopathology, MDCT as well as MRI were able to differentiate typical morpholocigal features for fatty, fibrous or calcified plaque components. Using the information presented in this study, in vivo coronary artery wall imaging using MDCT as well as MRI could be facilitated and supported for future investigations on this subject.

Adult↗
PubMed2004

MDCT-imaging of peripheral arterial disease.

With the design and development of advanced computed tomography (CT) techniques and applications, like the newest generation of 16-detector-row CTs, CT angiography of the lower limb becomes a feasible tool for imaging peripheral vascular disease. Due to several advantages, compared with conventional digital subtraction angiography (DSA), including minimal invasiveness, CT angiography competes against diagnostic DSA in several clinical situations. 16-DCT offers the possibility to acquire thin slices from the diaphragm to the ankle in less than 40 sec. Easily, a data set of 800 to 1200 transverse slices may be created. To use transverse reconstructions alone to read these volumetric data sets is not appropriate. Powerful post-processing tools for volumetric analysis are required so that routine interpretation can be performed as efficiently and accurately as transverse section review. Because of its widespread availability and applicability, CT angiography of the lower extremities may be applied to patients in a pre- or post-procedural situation and also serves as a first line modality in patients with acute onset of clinical symptoms. Although multidetector CT arteriography is rapidly achieving clinical acceptance, further studies need to be performed to fully evaluate the clinical value of this method of peripheral arterial imaging. This article reviews the current status of multidetector CT peripheral arteriography, including indications, technical details, image post-processing, radiation exposure, and clinical results.

Angiography↗
PubMed2004

Optimization of ex vivo CT- and MR- imaging of atherosclerotic vessel wall changes.

OBJECTIVE: To optimize a methodology for ex vivo imaging of atherosclerotic vessel wall changes using multidetector-row computed tomography (MDCT) and multi-contrast magnetic resonance imaging (MRI). METHODS: In phantom studies and studies on intact ex vivo porcine and human hearts, various filling mixtures of MDCT and MRI contrast agents have been evaluated, to enable filling and distension of the coronary arteries for optimal visualization of atherosclerotic vessel wall changes with both techniques. Various proportions of methyl cellulose, iodine-containing CT contrast agent and paramagnetic MR contrast agent containing iron-oxide particles have been tested. Imaging parameters have been optimized for high resolution plaque imaging using a four detector-row CT scanner and a 1.5 T MR system. RESULTS: Phantom studies and studies on ex vivo porcine and human hearts demonstrated optimal proportion of methyl cellulose and CT contrast agent to be 98% vs. 2%, and 75% vs. 25% of methyl cellulose vs. MR contrast agent, respectively. These proportions provided optimal opacification of the vessel lumen in the MDCT images with 250 Hounsfield Units, and good signal suppression within the vessel lumen in the MR images, resembling in vivo imaging techniques. After retrospective matching with histopathology, atherosclerotic lesions of the human ex vivo specimens could be identified on MRI and MDCT images. CONCLUSION: Using an optimized mixture of methyl cellulose, MDCT and MRI contrast agents, visualization of atherosclerotic vessel wall changes is feasible, and applicable to various ex vivo models.

Aged↗