Comparison of machine learning methods with logistic regression analysis in creating predictive models for risk of critical in-hospital events in COVID-19 patients on hospital admission.

BACKGROUND: Machine learning (ML) algorithms have been trained to early predict critical in-hospital events from COVID-19 using patient data at admission, but little is known on how their performance compares with each other and/or with statistical logistic regression (LR). This prospective multicentre cohort study compares the performance of a LR and five ML models on the contribution of influencing predictors and predictor-to-event relationships on prediction model´s performance. METHODS: We used 25 baseline variables of 490 COVID-19 patients admitted to 8 hospitals in Germany (March-November 2020) to develop and validate (75/25 random-split) 3 linear (L1 and L2 penalty, elastic net [EN]) and 2 non-linear (support vector machine [SVM] with radial kernel, random forest [RF]) ML approaches for predicting critical events defined by intensive care unit transfer, invasive ventilation and/or death (composite end-point: 181 patients). Models were compared for performance (area-under-the-receiver-operating characteristic-curve [AUC], Brier score) and predictor importance (performance-loss metrics, partial-dependence profiles). RESULTS: Models performed close with a small benefit for LR (utilizing restricted cubic splines for non-linearity) and RF (AUC means: 0.763-0.731 [RF-L1]); Brier scores: 0.184-0.197 [LR-L1]). Top ranked predictor variables (consistently highest importance: C-reactive protein) were largely identical across models, except creatinine, which exhibited marginal (L1, L2, EN, SVM) or high/non-linear effects (LR, RF) on events. CONCLUSIONS: Although the LR and ML models analysed showed no strong differences in performance and the most influencing predictors for COVID-19-related event prediction, our results indicate a predictive benefit from taking account for non-linear predictor-to-event relationships and effects. Future efforts should focus on leveraging data-driven ML technologies from static towards dynamic modelling solutions that continuously learn and adapt to changes in data environments during the evolving pandemic. TRIAL REGISTRATION NUMBER: NCT04659187.

Prognostic Impact of Acute Cardiovascular Events in COVID-19 Hospitalized Patients-Results from the CORONA Germany Study.

BACKGROUND: Acute myocardial injury (AMJ), assessed by elevated levels of cardiac troponin, is associated with fatal outcome in coronavirus disease 2019 (COVID-19). However, the role of acute cardiovascular (CV) events defined by clinical manifestation rather than sole elevations of biomarkers is unclear in hospitalized COVID-19 patients. OBJECTIVE: The aim of this study was to investigate acute clinically manifest CV events in hospitalized COVID-19 patients. METHODS: From 1 March 2020 to 5 January 2021, we conducted a multicenter, prospective, epidemiological cohort study at six hospitals from Hamburg, Germany (a portion of the state-wide 45-center CORONA Germany cohort study) enrolling all hospitalized COVID-19 patients. Primary endpoint was occurrence of a clinically manifest CV-event. RESULTS: In total, 132 CV-events occurred in 92 of 414 (22.2%) patients in the Hamburg-cohort: cardiogenic shock in 10 (2.4%), cardiopulmonary resuscitation in 12 (2.9%), acute coronary syndrome in 11 (2.7%), de-novo arrhythmia in 31 (7.5%), acute heart-failure in 43 (10.3%), myocarditis in 2 (0.5%), pulmonary-embolism in 11 (2.7%), thrombosis in 9 (2.2%) and stroke in 3 (0.7%). In the Hamburg-cohort, mortality was 46% (42/92) for patients with a CV-event and 33% (27/83) for patients with only AMJ without CV-event (OR 1.7, CI: (0.94-3.2), p = 0.077). Mortality was higher in patients with CV-events (Odds ratio(OR): 4.8, 95%-confidence-interval(CI): [2.9-8]). Age (OR 1.1, CI: (0.66-1.86)), atrial fibrillation (AF) on baseline-ECG (OR 3.4, CI: (1.74-6.8)), systolic blood-pressure (OR 0.7, CI: (0.53-0.96)), potassium (OR 1.3, CI: (0.99-1.73)) and C-reactive-protein (1.4, CI (1.04-1.76)) were associated with CV-events. CONCLUSION: Hospitalized COVID-19 patients with clinical manifestation of acute cardiovascular events show an almost five-fold increased mortality. In this regard, the emergence of arrhythmias is a major determinant.

Clinical outcome, risk assessment, and seasonal variation in hospitalized COVID-19 patients-Results from the CORONA Germany study.

BACKGROUND: After one year of the pandemic and hints of seasonal patterns, temporal variations of in-hospital mortality in COVID-19 are widely unknown. Additionally, heterogeneous data regarding clinical indicators predicting disease severity has been published. However, there is a need for a risk stratification model integrating the effects on disease severity and mortality to support clinical decision-making. METHODS: We conducted a multicenter, observational, prospective, epidemiological cohort study at 45 hospitals in Germany. Until 1 January 2021, all hospitalized SARS CoV-2 positive patients were included. A comprehensive data set was collected in a cohort of seven hospitals. The primary objective was disease severity and prediction of mild, severe, and fatal cases. Ancillary analyses included a temporal analysis of all hospitalized COVID-19 patients for the entire year 2020. FINDINGS: A total of 4704 COVID-19 patients were hospitalized with a mortality rate of 19% (890/4704). Rates of mortality, need for ventilation, pneumonia, and respiratory insufficiency showed temporal variations, whereas age had a strong influence on the course of mortality. In cohort conducting analyses, prognostic factors for fatal/severe disease were: age (odds ratio (OR) 1.704, CI:[1.221-2.377]), respiratory rate (OR 1.688, CI:[1.222-2.333]), lactate dehydrogenase (LDH) (OR 1.312, CI:[1.015-1.695]), C-reactive protein (CRP) (OR 2.132, CI:[1.533-2.965]), and creatinine values (OR 2.573, CI:[1.593-4.154]. CONCLUSIONS: Age, respiratory rate, LDH, CRP, and creatinine at baseline are associated with all cause death, and need for ventilation/ICU treatment in a nationwide series of COVID 19 hospitalized patients. Especially age plays an important prognostic role. In-hospital mortality showed temporal variation during the year 2020, influenced by age. TRIAL REGISTRATION NUMBER: NCT04659187.

Comparison of the high relaxivity Gd chelates P1152 and Gd-BOPTA for contrast-enhanced MR angiography in rabbits at 1.5 Tesla and 3.0 Tesla.

PURPOSE: To compare signal-enhancing properties of the high relaxivity Gd chelates P1152 and Gd-BOPTA for contrast-enhanced MR angiography (CE-MRA) in rabbits at 1.5 Tesla (T) and 3.0T. MATERIALS AND METHODS: Three-dimensional CE-MRA of the abdominal vasculature was performed in six rabbits using both contrast agents at a dose of 0.1 mmol/kg. Data acquisition was carried out during first pass and up to 10 min after contrast material administration. CNR was determined in aorta, vena cava, and renal cortex. Image quality (5-point scale, 5 = best) of first pass MR angiograms was rated by two radiologists. RESULTS: During first pass CNR of the aorta was 55.1 +/- 5.8 (P1152) and 40.3 +/- 3.9 (Gd-BOPTA) at 1.5T (P < 0.05), and 114.9 +/- 9.9 (P1152) and 73.5 +/- 8.1 (Gd-BOPTA) at 3.0T (P < 0.05). Both contrast agents showed a comparable decline of CNR within 10 min. Image quality was rated 4.8 +/- 0.40 (P1152) and 4.5 +/- 0.50 (Gd-BOPTA) at 1.5T (P = 0.17), and 4.8 +/- 0.37 (P1152) and 4.7 +/- 0.47 (Gd-BOPTA) at 3.0T (P = 0.61). CONCLUSION: The high relaxivity Gd-chelate P1152 offers potential to improve image contrast for CE-MRA compared with a clinically approved high relaxivity contrast agent.

Multicenter, double-blind, randomized, intraindividual crossover comparison of gadobenate dimeglumine and gadopentetate dimeglumine for MR angiography of peripheral arteries.

PURPOSE: To prospectively compare the image quality and diagnostic performance achieved with doses of gadobenate dimeglumine and gadopentetate dimeglumine of 0.1 mmol per kilogram of body weight in patients undergoing contrast material-enhanced magnetic resonance (MR) angiography of the pelvis, thigh, and lower-leg (excluding foot) for suspected or known peripheral arterial occlusive disease. MATERIALS AND METHODS: Institutional review board approval was granted from each center and informed written consent was obtained from all patients. Between November 2006 and January 2008, 96 patients (62 men, 34 women; mean age, 63.7 years +/- 10.4 [standard deviation]; range, 39-86 years) underwent two identical examinations at 1.5 T by using three-dimensional spoiled gradient-echo sequences and randomized 0.1-mmol/kg doses of each agent. Images were evaluated on-site for technical adequacy and quality of vessel visualization and offsite by three independent blinded readers for anatomic delineation and detection/exclusion of pathologic features. Comparative diagnostic performance was determined in 31 patients who underwent digital subtraction angiography. Data were analyzed by using the Wilcoxon signed-rank, McNemar, and Wald tests. Interreader agreement was determined by using generalized kappa statistics. Differences in quantitative contrast enhancement were assessed and a safety evaluation was performed. RESULTS: Ninety-two patients received both agents. Significantly better performance (P < .0001; all evaluations) with gadobenate dimeglumine was noted on-site for technical adequacy and vessel visualization quality and offsite for anatomic delineation and detection/exclusion of pathologic features. Contrast enhancement (P < or = .0001) and detection of clinically relevant disease (P < or = .0028) were significantly improved with gadobenate dimeglumine. Interreader agreement for stenosis detection and grading was good to excellent (kappa = 0.749 and 0.805, respectively). Mild adverse events were reported for four (six events) and five (eight events) patients after gadobenate dimeglumine and gadopentetate dimeglumine, respectively. CONCLUSION: Higher-quality vessel visualization, greater contrast enhancement, fewer technical failures, and improved diagnostic performance are obtained with gadobenate dimeglumine, relative to gadopentetate dimeglumine, when compared intraindividually at 0.1-mmol/kg doses in patients undergoing contrast-enhanced MR angiography for suspected peripheral arterial occlusive disease.

Isolated closed minor-muscle injury of the lower leg did not cause an obvious systemic immune response.

OBJECTIVE: A common consequence in patients with blunt trauma is a deterioration of the immune system. The specific impacts of a frequently occurring isolated soft tissue trauma on the immune response are described. However, the dimension of trauma needed to cause systemic effects has not been definitely elucidated. METHODS: Mice were traumatized on the lower leg. The extent of soft tissue trauma was quantified by determination of the wet/dry ratio, magnetic resonance imaging (MRI), and serum content of muscle proteins. Five minutes, 3, 24, 36, 48, and 72 h after trauma (a.t.) the ex vivo cytokine-expression of immune-competent cells were measured. RESULTS: Trauma resulted in an early edema that could be quantified by MRI and wet/dry ration. Release of muscle-specific proteins was detected 5 min a.t. The trauma did not cause significant changes of TNF-alpha response of isolated cells to endotoxin. IL6-response of splenocytes to endotoxin was slightly increased 72 h a.t., while IL6-response of peritoneal macrophages to endotoxin was decreased 36 h a.t. CONCLUSION: We describe a standardized trauma model for minor soft tissue injury in mice. Systemic effects on the immune system by traumatized lower leg were not found on the level of circulating cytokines or cellular responses to endotoxin.

Contrast-enhanced magnetic resonance angiography: evaluation of the high relaxivity low diffusible gadolinium-based contrast agent P846 in comparison with gadoterate meglumine in rabbits at 1.5 Tesla and 3.0 Tesla.

OBJECTIVES: To evaluate the gadolinium-based contrast agent P846 and compare it with gadoterate meglumine (Gd-DOTA) for contrast-enhanced magnetic resonance angiography (MRA) in rabbits at 1.5 T and 3.0 T, respectively. MATERIALS AND METHODS: Five rabbits underwent contrast-enhanced MRA of the abdominal vasculature applying gadolinium doses of 0.025 mmoL/kg for P846 and 0.1 mmoL/kg for Gd-DOTA, respectively. All animals were examined on a 1.5-T and 3.0-T MR system. Image data were acquired during the first-pass arterial phase and repeatedly over 10 minutes. Contrast-to-noise-ratio (CNR) was determined in the aorta, the inferior vena cava, and the renal cortex. Image quality of arterial phase MR angiograms was consensually judged on a 5-point scale (5 = high). RESULTS: Contrast-enhanced MRA was successful in all cases with both contrast agents. CNR values consistently proved statistically significantly higher for P846 compared with Gd-DOTA. CNR values in the aorta during the arterial phase were 46.0 +/- 3.7 (P846) and 28.0 +/- 3.2 (Gd-DOTA) at 1.5 T (P < 0.05), and correspondingly 89.3 +/- 12.7 (P846) and 64.1 +/- 15.0 (Gd-DOTA) at 3.0 T (P < 0.05). Image quality of arterial phase MR angiograms was rated with scores of 4.8 +/- 0.4 (P846) and 4.0 +/- 0.0 (Gd-DOTA) at 1.5 T (P = 0.06), and 5.0 +/- 0.0 (P846) and 4.8 +/- 0.4 (Gd-DOTA) at 3.0 T (P = 0.42), respectively. CONCLUSIONS: The contrast agent P846 provides high contrast enhancement and image quality for contrast-enhanced MRA in rabbits at 1.5 T and 3.0 T with a 4-fold lower gadolinium dose compared with a standard extracellular contrast agent.

Combined arterial and venous whole-body MR angiography with cardiac MR imaging in patients with thromboembolic disease--initial experience.

The objective was to assess the feasibility of a combined arterial and venous whole-body three-dimensional magnetic resonance (MR) angiography, together with a cardiac MR examination, in patients with arterial thromboembolism. Ten patients with arterial thromboembolism underwent a contrast-enhanced whole-body MR examination of the arterial and venous vessels, followed by a cardiac MR examination on a separate occasion within 24 h. All examinations were performed on a 1.5-T MR scanner. For both arterial and venous MR angiography only one injection of contrast agent was necessary. The cardiac imaging protocol included dark-blood-prepared half-Fourier acquisition single-shot turbo-spin-echo sequences, fast steady-state free precession cine sequences, T2-weighted turbo-spin-echo sequences and inversion recovery gradient-echo fast low-angle-shot sequences after injection of contrast agent. MR imaging revealed additional clinically unknown arterial thromboembolisms in four patients. The thoracic aorta was depicted as embolic source in four patients, while deep vein thrombosis (DVT) was found in one patient as the underlying disease. Unsuspected infarction of parenchymal organs was detected by MRI in two patients. An unknown additional DVT was found in one patient. Four patients were considered to have arterial emboli of cardiac origin. In conclusion, acquisition of arterial and venous MR angiograms of the entire vascular system combined with cardiac MR imaging is a most comprehensive and valuable strategy in patients with arterial thromboembolism.

MR angiography of the renal arteries: intraindividual comparison of double-dose contrast enhancement at 1.5 T with standard dose at 3 T.

OBJECTIVE: The purpose of this study was to compare prospectively and within subjects use of 0.1 mmol/kg of gadodiamide at 3 T with use of 0.2 mmol/kg of gadodiamide at 1.5 T for MR angiography of the renal arteries. SUBJECTS AND METHODS: Twenty-two patients (14 men, eight women; mean age, 66.5 years) underwent two MR angiographic examinations of the renal arteries separated by at least 24 hours on whole-body 1.5- and 3-T MRI systems with a phase-encoded 3D spoiled breath-hold pulse sequence. Two radiologists blinded to the dose of contrast material assessed all image data in consensus for renal arterial disease and for image quality on a five-point Likert-type scale. Quantitative evaluation (vessel signal-to-noise ratio and vessel-muscle contrast-to-noise ratio) was performed by a third radiologist. RESULTS: Five renal arterial stenoses were detected with both techniques. The difference in mean image quality for the two doses and field strengths was not statistically significant. Overall vessel length and intraparenchymal branches, however, were better visualized with the double dose at 1.5 T. Signal-to-noise and contrast-to-noise ratios were significantly higher (both, p < 0.05) with the double dose at 1.5 T (125.7 and 64.2, respectively) compared with the standard dose at 3 T (112.3 and 59.7). CONCLUSION: MR angiography can be performed with high diagnostic image quality at 3 T with 0.1 mmol/kg of gadodiamide. Signal-to-noise and contrast-to-noise ratios are higher with a double dose at 1.5 T.

Diagnostic performance of gadobenate dimeglumine enhanced MR angiography of the iliofemoral and calf arteries: a large-scale multicenter trial.

OBJECTIVE: The purpose of this study was to compare gadobenate dimeglumine-enhanced MR angiography and unenhanced time-of-flight MR angiography for the detection of significant peripheral arterial occlusive disease using digital subtraction angiography as our reference standard. SUBJECTS AND METHODS: Two hundred seventy-two patients underwent MR angiography and digital subtraction angiography of the iliofemoral arteries. MR angiography was performed before (2D time-of-flight acquisitions) and after (spoiled gradient-echo acquisitions) the administration of 0.1 mmol/kg of gadobenate dimeglumine at 1-2 mL/s. Contrast-enhanced MR angiography and digital subtraction angiography of the calf arteries were performed in 241 of 272 participants. Images were evaluated on-site and by four blinded reviewers (three for MR angiography, one for digital subtraction angiography). Comparative diagnostic performance for the detection of significant (> or = 51% vessel lumen narrowing) disease was evaluated using the McNemar test and generalized estimating equations. Interobserver agreement was assessed with generalized kappa statistics. The chi-square test was used to compare technical failure rates. RESULTS: Digital subtraction angiography confirmed significant disease (597 stenoses, 386 occlusions) in 983 iliofemoral segments. The sensitivity (54-80.9%), specificity (89.7-95.3%), and accuracy (85-87.5%) of contrast-enhanced MR angiography for the detection of significant iliofemoral disease were significantly (p < 0.001, all reviewers) better than those of time-of-flight MR angiography (33.2-62.8%, 74.3-88.9%, and 68-77.3%, respectively). Similar diagnostic performance was obtained for the calf arteries. The technical failure rate with contrast-enhanced MR angiography (2.5-3.4%) was similar to that of digital subtraction angiography (1.4%) and significantly (p < 0.001) lower than that of time-of-flight MR angiography (6.2-18.0%). Significantly better reproducibility (p < 0.001) was obtained with contrast-enhanced MR angiography (82% vs 65.2% agreement; kappa = 0.66 vs 0.45). CONCLUSION: Improved diagnostic performance and reproducibility are achievable with gadobenate dimeglumine-enhanced MR angiography in patients with peripheral arterial occlusive disease.

Contrast-enhanced magnetic resonance angiography: P792 blood pool agent versus Gd-DOTA in rabbits at 3.0 T versus 1.5 T.

PURPOSE: To assess the gadolinium-based macromolecular intravascular contrast agent P792 for magnetic resonance angiography (MRA) at magnetic field strengths of 3.0 T, in comparison to 1.5 T, in rabbits. MATERIALS AND METHODS: Eleven female New Zealand rabbits of the same age served as the animal model. Dose relationship testing was performed with 2 doses (13 and 25 micromol/kg; n = 4 per group) of P792 as compared with a single dose (100 micromol/kg; n = 3) of gadoterate meglumine (Gd-DOTA). All animals underwent contrast-enhanced MRA of the abdominal aorta and its branches on 2 occasions separated by 72 hours. The particular doses were administered in random order. Contrast-enhanced MRA was performed on 3.0 and 1.5 T whole-body MR systems, using a fast 3D spoiled gradient recalled echo sequence. Data acquisition was performed before and up to 10 minutes after administration of intravenous contrast material. Image quality was judged on a 4-point-Likert scale. Signal-to-noise and contrast-to-noise measurements were performed; statistical differences (P < 0.05) between the groups were determined. RESULTS: P792 and Gd-DOTA yielded high-quality MR angiograms in rabbits in all cases. Although image quality within the first 3 minutes after contrast material administration was equal for both agents, P792 at a dose of 25 micromol/kg was considered superior to Gd-DOTA at the later time points. Signal-to-noise and contrast-to-noise values of the higher dose of P792 were statistically significantly higher than those of Gd-DOTA in the post-bolus phase. CONCLUSIONS: P792 seems to be well suited for high-quality early phase and equilibrium phase MRA in rabbits at a field strength of 3.0 T, on the basis of this initial evaluation in an animal model.

Peripheral vascular disease: comparison of continuous MR angiography and conventional MR angiography--pilot study.

The aim of this study was to prospectively assess the accuracy of three-dimensional magnetic resonance (MR) angiography for evaluation of stenosis in the peripheral arterial system with a continuous moving table technique, with conventional MR angiography as reference. This study was approved by the local institutional review board; informed consent was obtained. Five healthy male volunteers (mean age, 27 years; range, 24-35 years) and four men and one woman (mean age, 63 years; range, 46-78 years) with peripheral arterial occlusive disease were examined. Images obtained with both techniques showed excellent concordance (Cohen kappa = 0.75). Images obtained with a conventional protocol had higher quality compared with those obtained with the continuous technique (mean, 1.07 +/- 0.25 [standard deviation] vs 1.58 +/- 0.6; P < .05); small vessels appeared sharper on them. For detection of significant stenosis and occlusion, accuracy, sensitivity, and specificity of the continuous technique were 92.8%, 100%, and 89.2%, respectively.

Clinical safety and diagnostic value of the gadolinium chelate gadoterate meglumine (Gd-DOTA).

OBJECTIVE: The purpose of this study was to assess the diagnostic value and safety of the contrast agent gadoterate meglumine (Gd-DOTA, DOTAREM, Guerbet, Roissy CdG Cedex, France) in the setting of a postmarketing surveillance study. MATERIALS AND METHODS: Between January 2004 and October 2005, radiologists in 61 radiologic institutions were asked to document the routine use of Gd-DOTA in a questionnaire. In addition to assessing the image quality and diagnostic value of the contrast-enhanced magnetic resonance imaging scans, we statistically evaluated and analyzed demographic and safety data. RESULTS: A total of 24,308 patients were intravenously injected with Gd-DOTA for various diagnostic examinations. The examination allowed for establishing a diagnosis in >99% of cases and image quality was rated as "excellent" or "good" in 97.5% of all cases. Adverse events were noted in only 0.4% of the examinations and were mostly rated as minor, such as feeling of warmth or taste alteration. There was one serious adverse event, albeit with complete recovery. CONCLUSION: This postmarketing surveillance study suggests diagnostic efficacy and a favorable clinical safety profile of Gd-DOTA in clinical practice.

Time-resolved contrast-enhanced magnetic resonance angiography of the hand with parallel imaging and view sharing: initial experience.

We sought to compare a three-dimensional, contrast-enhanced, magnetic resonance angiogram (3D CE MRA) sequence combining parallel-imaging (generalised autocalibrating partially parallel acquisitions (GRAPPA)) with a time-resolved echo-shared angiographic technique (TREAT) in an intraindividual comparison to a standard 3D MRA sequence. Four healthy volunteers (27-32 years), and 11 patients (11-82 years) with vascular pathologies of the hand were examined on a 1.5-Tesla (T) MR system (Magnetom Avanto, Siemens, Erlangen, Germany) using two multichannel receiver coils. Following automatic injection (flow rate 2.5 cc/s) of 0.1 mmol/kg gadoterate (Dotarem, Guerbet, Roissy, France), 32 consecutive 3D data sets were collected with the TREAT sequence (TR/TE: 4.02/1.31 ms, FA: 10 degrees, GRAPPA acceleration factor: R=2, TREAT factor: 5, voxel size: 1.0 x 0.7 x 1.3 mm(3)) and a T1-wwighted 3D gradient-echo sequence (TR/TE: 5.3/1.57 ms, FA: 30 degrees, GRAPPA acceleration factor: 2, voxel size: 0.71 x 0.71 x 0.71 mm(3,)). MR data sets were evaluated and compared for image quality and visualisation of vascular details. In the volunteer group, all MR imaging was successful while technical problems prevented acquisition of the standard protocol in two patients. For the corresponding segments, the number of visible segments was equal on both sequences. Overall image quality was significantly better on the standard protocol than on the TREAT protocol. TREAT MRA provided functional information in lesions with rapid blood flow, e.g. detection of feeding and draining vessels in an haemangioma. TREAT-MRA is a robust technique that combines morphological and functional information of the hand vasculature and deals with the very special physiological demands of vascular lesions, such as quick arteriovenous transit time.

Magnetic resonance imaging of experimental atherosclerotic plaque: comparison of two ultrasmall superparamagnetic particles of iron oxide.

PURPOSE: To evaluate a new ultrasmall superparamagnetic particles of iron oxide (USPIO) compound, ferumoxytol, as a marker of macrophage activity in atherosclerotic plaques and to compare it to ferumoxtran-10. MATERIALS AND METHODS: Ten mature heritable hyperlipidemic (WHHL) female Watanabe rabbits served as the animal model for atherosclerosis, four coeval female New Zealand White (NZW) rabbits were the control group. Five WHHL and two NZW received a single intravenous injection (250 micromol/kg) of either ferumoxtran-10 or ferumoxytol and were subjected to daily MR examinations on a 1.5T whole body scanner for the next five days. Development of signal intensity changes and susceptibility effects was assessed. Statistical analysis was based on a nonparametric Wilcoxon-Mann-Whitney-U test by using a P value at the 0.05 significance level. On day 5, the rabbits were sacrificed and the aorta was referred to histopathology, distribution of iron particles in the vessel wall was analyzed. RESULTS: MRI was feasible in all animals. Three days after injection of ferumoxytol the highest luminal signal intensity measurements were observed in the ferumoxytol group; the highest measurements were five days after injection in the ferumoxtran-10 group (P < 0.05). In the WHHL, susceptibility effects presented as homogeneous dark lines parallel to the aortic wall after ferumoxytol and spotted areas void of signal after ferumoxtran-10. None of these findings were observed in the NZW control groups. CONCLUSION: Ferumoxtran-10 and ferumoxytol at a respective dose of 250 mumol/kg appear well suited for atherosclerotic plaque detection with MRI in experimental atherosclerosis. Ferumoxytol warrants further analysis in humans.

The efficacy of gadobenate dimeglumine (Gd-BOPTA) at 3 Tesla in brain magnetic resonance imaging: comparison to 1.5 Tesla and a standard gadolinium chelate using a rat brain tumor model.

OBJECTIVES: The objectives of this study were to analyze the differences in contrast enhancement using gadobenate dimeglumine (Gd-BOPTA or MultiHance) at 3 T versus 1.5 T and to compare Gd-BOPTA with a standard gadolinium chelate, gadopentetate dimeglumine (Gd-DTPA or Magnevist), at 3 T in a rat glioma model. MATERIALS AND METHODS: Twelve rats with surgically implanted gliomas were randomized to either comparing Gd-BOPTA at 1.5 T versus 3 T (n=7) or comparing Gd-BOPTA and Gd-DTPA at 3 T (n=5). Matched T1-weighted spin-echo techniques were used for both comparisons and the order of examinations was randomized. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and lesion enhancement (LE) were evaluated using a region-of-interest analysis. A veterinary histopathologist evaluated all brain specimens. RESULTS: In the evaluation of Gd-BOPTA at 3 T and 1.5 T, there were significant increases in SNR, LE, and CNR at 3 T. Average increases in brain and tumor SNR were 93% (P<0.0001) and 92% (P<0.0001), respectively. CNR increased by 121% (P<0.0001). Comparison of Gd-BOPTA and Gd-DTPA at 3 T demonstrated significantly higher CNR and LE with Gd-BOPTA. CNR increased by 35% (P=0.002). LE increased by 44% (P=0.03). CONCLUSIONS: Gd-BOPTA provides significantly higher CNR at 3 T compared with 1.5 T and also demonstrates significantly higher CNR when compared with a standard Gd-chelate at 3 T. As a result of transient protein binding, Gd-BOPTA may be superior to standard gadolinium chelates in neurologic imaging at 3 T.

Renal arteries: comparison of steady-state free precession MR angiography and contrast-enhanced MR angiography.

All participants provided informed consent to participate in this study, which was approved by the institutional review board. Breath-hold three-dimensional (3D) steady-state free precession (SSFP) magnetic resonance (MR) angiography was compared with 3D contrast material-enhanced MR angiography in patients suspected of having renal artery stenosis. Two radiologists assessed visualization of renal arteries and detection of vascular disease. With SSFP MR angiography, 39 of 41 renal arteries in 19 patients were correctly detected. Relevant stenoses were correctly identified with SSFP MR angiography in two patients. In two patients, SSFP MR angiographic data sets led to false-positive overgrading of vascular disease. Fast breath-hold 3D SSFP MR angiography appears to be feasible for MR angiography of renal arteries.

Total-body 3D magnetic resonance angiography influences the management of patients with peripheral arterial occlusive disease.

High-resolution total-body 3D MR angiography (MRA) has recently become available, revealing additional clinically relevant disease in patients with peripheral arterial occlusive disease (PAOD). However, the actual impact of total-body MRA on patient management in patients with PAOD has not been investigated so far. Two hundred forty-nine consecutive patients with angiographically proven PAOD were prospectively examined by means of contrast-enhanced total-body 3D MRA on a 1.5-T MR scanner. All correlative imaging studies performed within 60 days of total-body MRA were included in the efficacy analysis. Additional clinically relevant disease (luminal narrowing >50%, aneurysmal changes or dissections) was found in 73 segments (52 patients), including the renal arteries (36 segments), carotid arteries (28 segments), subclavian arteries (four segments) and abdominal aortic aneurysms (AAA) (five segments). Of the 73 segments, 36 were deemed necessary for further investigation by means of focused MRA examinations; the diagnosis was confirmed in all cases. Within the 60-day follow-up period, interventional or surgical therapy outside the peripheral arterial tree was performed in nine patients (11 segments), including carotid endatherectomy and renal artery angioplasty. The outlined total-body 3D MRA approach permits a comprehensive evaluation of the arterial system in patients with atherosclerosis and does indeed have an impact on patient management in patients with PAOD.

Whole-body MRI for staging patients with head and neck squamous cell carcinoma.

CONCLUSIONS: Whole-body MRI is feasible for the tumor staging of patients with malignant head and neck tumors and appears to be a quick, reliable and proven alternative in general and for patients with contraindications to CT. This examination minimizes the logistical effort required compared to multimodality strategies. Its economic impact remains to be determined. OBJECTIVE: To assess the performance of whole-body MRI for staging patients with squamous cell carcinoma of the head and neck region. MATERIAL AND METHODS: This was a randomized, prospective clinical study. For tumor staging, 21 patients (mean age 56.7 years; range 43-80 years) with advanced malignant head and neck tumors underwent whole-body MRI in addition to routinely performed imaging investigations, including sonography, chest X-ray, CT of the head, neck and thorax and endoscopy. All investigations were accomplished within a period of 10+/-3 days in a random order. A randomized, blinded, consensus assessment of all the whole-body MRI examinations was performed by two radiologists. The localization and extent of the primary tumor and metastases were documented for whole-body MRI and compared to the standard of reference (all other imaging modalities as well as histology). Point estimates of the diagnostic accuracy of whole-body MRI were calculated. RESULTS: In accordance with the standard of reference, the overall TNM category was correctly determined with whole-body MRI in all 21 patients. However, four patients were classified as having carcinoma of unknown primary, as the primary tumor was not found with any imaging modality. Two patients had mediastinal, pulmonary and hepatic metastases.