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Biomedical subjects

Marc Dewey

Publications and source records attributed to Marc Dewey.

29 records · Page 2Linked to original sources
PubMed2005

Multislice computed tomography for preoperative evaluation of right ventricular volumes and function: comparison with magnetic resonance imaging.

BACKGROUND: This study was performed to validate preoperative right ventricular measurements obtained from multislice spiral computed tomography data sets in comparison with magnetic resonance imaging. METHODS: Before cardiac surgery, 25 patients (among them 12 patients with compromised right ventricular function) underwent contrast-enhanced retrospectively electrocardiogram-gated multislice spiral computed tomography and cine magnetic resonance imaging in a standardized fashion. Right ventricular end-diastolic, end-systolic and stroke volume, ejection fraction, and myocardial mass were calculated according to the slice summation method. Measurements obtained with both modalities were compared using Pearson's correlation coefficient (r), Student's t test for paired samples, and Bland-Altman analysis. RESULTS: The right ventricle was completely visualized with invariably adequate image quality on all multislice spiral computed tomography and magnetic resonance images. For all measurements a close correlation between multislice spiral computed tomography and magnetic resonance imaging was found (end-diastolic volume, r = 0.93; end-systolic volume, r = 0.95; stroke volume, r = 0.91; ejection fraction, r = 0.96; mass, r = 0.94). Mean values of all measurements did not differ significantly between both modalities, and limits of agreement were in an acceptable range. CONCLUSIONS: When compared with magnetic resonance imaging as a reference method, multislice spiral computed tomography seems to be an accurate and reliable noninvasive technique for evaluating right ventricular measurements.

Adult↗
PubMed2004

[Noninvasive diagnosis of coronary artery disease].

BACKGROUND: Coronary artery disease (CAD) is one of the most common diseases that accounts for a considerable part of health care reimbursement. Thus, noninvasive diagnosis of CAD is likewise of pivotal importance for medical care today. NONINVASIVE DIAGNOSIS OF CAD: In this review, the authors present the entire spectrum of noninvasive diagnostic methods available for CAD starting with a Ergomedescription and discussion of the simplest and most important clinical approaches (patients' complaints, risk factors, electrocardiogram, and treadmill test). The established imaging modalities for diagnosing CAD (echocardiography, stress echocardiography, and scintigraphy including the SPECT and PET technique) are presented outlining their specific advantages and disadvantages. Finally, the authors discuss the most recent imaging modalities for the diagnosis of CAD (multislice computed tomography [MSCT] and magnetic resonance imaging [MRI]). MSCT allows for performing high-quality noninvasive coronary angiography, whereas MRI enables exact visualization of myocardial function, perfusion, and viability. CONCLUSION: The comprehensive assessment possible with MSCT and MRI and future developments will change the significance and importance of the conventional diagnostic methods for the diagnosis of CAD in the near future.

Adult↗
PubMed2004

Assessment of myocardial infarction in pigs using a rapid clearance blood pool contrast medium.

Delayed enhancement MRI using extracellular contrast media allows reliable detection of myocardial infarction. If blood pool contrast media like P792 (Vistarem, Guerbet, France), in addition to improving coronary MR angiography, can be shown to also produce delayed enhancement in myocardial infarction they could improve the prerequisites for a comprehensive cardiac MR examination. In this study reperfused myocardial infarction in five minipigs was imaged with an inversion-recovery fast low-angle shot sequence using P792 (0.013 mmol Gd/kg) and the extracellular contrast medium Gd-DOTA (Dotarem, 0.1 mmol Gd/kg, Guerbet). The infarction size determined on MRI using P792 (7.55 +/- 2.31 cm(2)) highly correlated both with histomorphometry (7.81 +/- 2.18 cm(2), r = 0.991, P < 0.002) and with MRI using Gd-DOTA (7.85 +/- 2.35 cm(2), r = 0.978, P < 0.005). Bland-Altman analysis showed that the limit of agreement of MRI using P792 compared to histomorphometry was 3.3 +/- 7.6% of the infarction size. The contrast-to-noise ratio between infarcted and remote myocardium was not significantly different between Gd-DOTA (5.9 +/- 2.4) and P792 (4.4 +/- 1.1, P = 0.5). The blood pool contrast medium P792 allows reliable assessment of viability with good contrast and accuracy.

Animals↗
PubMed2004

Isotropic half-millimeter angiography of coronary artery bypass grafts with 16-slice computed tomography.

BACKGROUND: Computed tomography (CT) with four detector rows and magnetic resonance imaging (MRI) are still of limited value for the assessment of coronary artery bypass grafts (CABG). We investigated the abilities of 16-slice CT in these patients. METHODS: A retrospective analysis of all noninvasive coronary angiographies with multislice computed tomography (MSCT; Aquilion, Toshiba) on patients with CABG referred to our institution between October 2002 and April 2003 was conducted. MSCT angiography was performed using a standard protocol (0.5-seconds rotation time, 16 x 0.5 mm detector collimation, 120 kV, 250 to 300 mA, and 0.25 pitch). None of the patients received beta-blockers to reduce the heart rate. Seventy-five CABGs (20 arterial grafts and 55 venous grafts) in 27 patients were evaluated for patency and adequate diagnostic quality by two radiologists in consensus. RESULTS: All arterial and venous grafts were depicted with adequate diagnostic quality and were eligible for evaluation. Fifteen occlusions and five significant stenoses (at least 50%) could be identified. All of the proximal and 99% of the distal anastomoses were eligible. One distal anastomosis of an arterial graft was not assessable due to surgical clip artifacts. The length of the acquisition window was 174 +/- 46 ms (range 71 to 234 ms). The majority of the patients (70%) had a heart rate above 65 beats/min. However, due to the improved temporal and spatial resolution none of the examinations had an insufficient image quality. CONCLUSIONS: MSCT angiography with 16 detector rows and an isotropic high resolution reliably depicts CABG with adequate diagnostic quality.

Coronary Angiography↗
PubMed2004

Multisegment and halfscan reconstruction of 16-slice computed tomography for detection of coronary artery stenoses.

RATIONALE AND OBJECTIVES: To compare the diagnostic accuracy and image quality of 2 reconstruction algorithms (multisegment and halfscan) for computed tomography (CT) coronary angiography in patients without beta-blocker medication. MATERIALS AND METHODS: Thirty-four patients with 42 significant coronary stenoses in 136 main coronary branches were examined using a 16-slice CT scanner (Aquilion, Toshiba, Otawara, Japan). Twenty-seven patients (79%) had heart rates above 65 beats/min. RESULTS: Without exclusion of branches the sensitivity, specificity, accuracy, and rate of nonassessable segments with multisegment versus halfscan reconstruction were 88 versus 74%, 91 versus 71%, 90 versus 72%, and 2 versus 21% (P < 0.01), respectively. Multisegment reconstruction improved the average vessel length free of motion artifacts by 56% compared with halfscan reconstruction (P < 0.01). Image quality in terms of vessel continuity and visibility of side branches (P < 0.005) was significantly better using multisegment reconstruction. CONCLUSIONS: Multisegment reconstruction has superior diagnostic accuracy and image quality compared with halfscan reconstruction in patients with normal heart rates.

Adult↗
PubMed2004

Magnetic resonance imaging of myocardial perfusion and viability using a blood pool contrast agent.

RATIONALE AND OBJECTIVES: A comprehensive cardiac magnetic resonance (MR) examination should comprise imaging of myocardial perfusion, viability, and the coronary arteries. Blood pool contrast agents (BPCAs) improve coronary MR angiography, whereas their potential for imaging of perfusion and viability is unknown. The abilities to noninvasively image myocardial perfusion and viability using the BPCA P792 (Guerbet, France) were tested in a closed-chest model of nonreperfused myocardial infarction in 5 pigs. MATERIALS AND METHODS: Two to 3 days after instrumentation, myocardial perfusion imaging with a saturation-recovery steady-state free precession technique and viability imaging with an inversion-recovery fast low-angle shot sequence were conducted on a 1.5-T MR scanner using the extracellular contrast agents (ECCA) Gd-DOTA (0.1 mmol Gd/kg) and blood pool contrast agent (BPCA) P792 (0.013 mmol Gd/kg). RESULTS: Perfusion defects were visualized in all pigs with good correlation between the ECCA and the BPCA (1.77 +/- 1.16 cm2 vs. 1.80 +/- 1.19 cm2, r = 0.959, P < 0.01). Reduced myocardial perfusion was detected using the ECCA up to 80 seconds after injection. In contrast, BPCA administration enabled visualization of perfusion defects on equilibrium perfusion imaging in all cases for 10 minutes. The size of myocardial infarction detected with viability MR imaging correlated well between the standard method (ECCA) and delayed-enhancement imaging with the BPCA (5.40 +/- 3.16 versus 5.52 +/- 3.13 cm3, r = 0.994, P < 0.002). CONCLUSIONS: The BPCA investigated in this study allows both reliable detection of perfusion defects on first pass and equilibrium perfusion imaging and characterization of viability after myocardial infarction. Thus, this contrast agent is suitable for a comprehensive cardiac MR examination.

Animals↗
PubMed2003

Coronary artery disease: new insights and their implications for radiology.

Coronary artery disease (CAD) diminishes local, regional, or global blood supply to the heart and is most commonly caused by coronary atherosclerosis. New insights into the etiology of atherosclerosis suggest that CAD is an inflammatory disorder that responds well to modulation rather than an unchangeable chronic process. Since 75% of all acute coronary syndromes result from rupture of atherosclerotic plaques, factors causing rupture have a crucial role. Magnetic resonance imaging and CT have the potential to visualize the composition of coronary artery plaques and thus to identify plaques at risk. Considering the new insights into stunning and hibernation, myocardial late enhancement on MRI might provide pivotal information for therapeutic decision making among lysis therapy, catheter intervention, and bypass surgery. Exercise electrocardiography without or with right precordial leads, stress echocardiography, and stress scintigraphy are simple clinical procedures to identify CAD with high sensitivities of 67, 92, 76, and 88%, respectively. The MRI and CT have to be compared with these good results. Nevertheless, we are expecting that MRI and CT will replace the conventional diagnostic modalities, gain a central role in diagnosing patients with suspected CAD, and prove to be cost-effective in this regard.

Coronary Disease↗
PubMed2003

[Peer-education workshop on research during medical studies. Results of a survey among participants].

BACKGROUND AND OBJECTIVE: Physicians in Germany are conferred the title "Doctor of medicine" (MD) upon successful completion of a dissertation. There is no course in the German medical curriculum that enables students to pursue original research. CONCEPT AND METHODS: We sought to address this lack of adequate preparation through a student-organized, hands-on workshop, which was problem- and, in part, computer-based. The workshop lasted 16 h (over the course of a weekend). The chronological sequence of a dissertation served as the main structure of this peer-education approach and was supported by a 30-page handout. The following topics were addressed: (1) Search for a dissertation, (2) Legal regulations, (3) Literature research and statistics, (4) Scientific writing, (5) Practical work, and (6) Review of the dissertation. The participants gained knowledge about and started working with the appropriate computer applications for these issues. So far, 60 students participated in four workshops. Evaluations were collected through an anonymous questionnaire at the end of the workshops. RESULTS: 56 students responded (93%). 98% of the respondents would definitely recommend other students to participate in the workshop. None of them recommend against taking the class. Students' opinion about their own skills in pursuing a dissertation before and at the end of the workshop (range: 1 = very good to 5 = unsatisfying) was 3.4 +/- 0.8 and 1.8 +/- 0.5, respectively ( p < 0.001). No student believed that his skills did not improve. 88% of the respondents wanted the workshop to continue being optional. CONCLUSIONS: This peer-education approach is cost-efficient, enjoys high acceptance by students, and improves research skills among participants.

Academic Dissertations as Topic↗