MR imaging of hypervascular liver tumors: timing optimization during the arterial phase

To analyze the optimal timing strategy for the detection of hypervascular liver tumors during the arterial phase of magnetic resonance (MR) imaging, a test examination after injection of 2 mL of gadopentetate dimeglumine was performed in 47 patients. The time course of the tumor-to-liver contrast-to-noise ratio (CNR) for all studies together was determined relative to the start of injection, the time of peak aortic enhancement, and the time of peak enhancement in the tumor. All studies were grouped together and the highest CNR was transiently observed at the time of peak tumor enhancement. This CNR was significantly higher than those observed at fixed delays after peak aortic enhancement. However, the CNRs at peak tumor enhancement+/-1.5 seconds did not differ significantly from those obtained after peak aortic enhancement. Finally, the CNRs obtained at fixed delays after the start of injection remained significantly lower. In hypervascular liver tumors, a higher CNR can be obtained during the arterial phase when the MR imaging delay is determined relative to the time of peak enhancement in the tumor or the aorta rather than being fixed after the start of contrast material injection. Timing based on the enhancement profile in the tumor rather than in the aorta should be performed only if rapid MR imaging is available with a time resolution of about 1.5 seconds to image the whole liver.     

Assessment of hepatic perfusion parameters with dynamic MRI.

Quantification of hepatic perfusion parameters greatly contributes to the assessment of liver function. The purpose of this study was to describe and validate the use of dynamic MRI for the noninvasive assessment of hepatic perfusion parameters. The signal from a fast T(1)-weighted spoiled gradient-echo sequence preceded by a nonslice-selective 90 degrees pulse and a spoiler gradient was calibrated in vitro with tubes filled with various gadolinium concentrations. Dynamic images of the liver were obtained after intravenous bolus administration of 0.05 mmol/kg of Gd-DOTA in rabbits with normal liver function. Hepatic, aortic, and portal venous signal intensities were converted to Gd-DOTA concentrations according to the in vitro calibration curve and fitted with a dual-input one-compartmental model. With MRI, hepatic blood flow was 100 +/- 35 mL min(-1) 100 mL(-1), the arterial fraction 24 +/- 11%, the distribution volume 13.0 +/- 3.7%, and the mean transit time 8.9 +/- 4.1 sec. A linear relationship was observed between perfusion values obtained with MRI and with radiolabeled microspheres (r = 0.93 for hepatic blood flow [P < 0.001], r = 0.79 for arterial blood flow [P = 0.01], and r = 0.91 for portal blood flow [P < 0.001]). Our results indicate that hepatic perfusion parameters can be assessed with dynamic MRI and compartmental modeling.     

Biodistribution of ultrasmall iron oxide particles in the rat liver

Ferumoxtran, an ultrasmall superparamagnetic iron oxide particle, can be located in several tissue compartments in the liver, namely the extracellular space (blood and interstitium), reticuloendothelial cells, and possibly hepatocytes. To better understand the compartmental distribution of ferumoxtran in the liver, we performed a longitudinal study in the rat using microscopy and magnetic resonance imaging. At light microscopy, no substantial cellular uptake of ferumoxtran was observed before one hour after injection. With a dose of 15 micromol Fe/kg, the number of ferumoxtran particles in the reticuloendothelial cells peaked between one and four hours and with a 150 micromol Fe/kg dose, it peaked between eight and 24 hours. Within hepatocytes, only sparse particles were observed with electron microscopy, at a dose of 150 micromol Fe/kg. Imaging performed up until one hour after ferumoxtran injection showed a significant increase in liver signal intensity on T1-weighted images. These results suggest that ferumoxtran mainly acts as an extracellular agent for at least one hour in the rat and that reticuloendothelial accumulation peaks at later time points. Substantial uptake within hepatocytes did not occur.     

First results of the introduction of DRGs in Germany and overview of experience from other DRG countries

In spite of numerous discussions and programs aimed at reducing public health care costs in Germany, the country has seen a massive increase in health care costs at an annual average rate of 7% since 1972. When German policymakers decided to reform the health care system by passing legislative measures on 22 December 1999, one of the key elements was to oblige hospitals and health insurance providers to replace the existing retrospective and procedural reimbursement system with a new prospective and diagnostic system based on diagnosis-related groups (DRGs). German policymakers are hoping to accomplish two feats with the introduction of DRGs: firstly, to improve the profitability of the health care system, and secondly, to improve the quality of health care services because DRGs require documentation and coding, which leads to increased transparency and allows for an external comparison of rendered services (benchmarking), as well as for an analysis and assessment of how appropriate and how successful the rendered services were in each particular case. Although the intentions underlying the introduction of DRGs are unquestionable, it remains to be determined whether the introduction has negative effects as well, and to which extent these negative effects have shown up so far. Hence the purpose of our survey will be to provide an extensive and systematic overview of results from other countries, along with preliminary results from Germany. In order to judge the trade-off between the desired and negative effects in a DRG system, we will define the set of parameters that determine the incentives of health care agents in such a system before surveying the economic and medical literature in light of these parameters in Section 3 and summarizing the results in Section 4. In view of the literature analysed, we find that the introduction of DRGs hasstarted a tendency towards a reduction in costs and towards a focus on profitability. If the legislator takes the necessary actions to reduce possible negative effects like manipulation and upcoding, the introduction of G-DRGs will lead to an increase in economic effectiveness and efficiency, while bringing more transparency into the quality of medical services at the same time.

Non-invasive quantification of liver perfusion with dynamic computed tomography and a dual-input one-compartmental model

Various liver diseases lead to significant alterations of the hepatic microcirculation. Therefore, quantification of hepatic perfusion has the potential to improve the assessment and management of liver diseases. Most methods used to quantify liver perfusion are invasive or controversial. This paper describes and validates a non-invasive method for the quantification of liver perfusion using computed tomography (CT). Dynamic single-section CT of the liver was performed after intravenous bolus administration of a low-molecular-mass iodinated contrast agent. Hepatic, aortic and portal-venous time-density curves were fitted with a dual-input one-compartmental model to calculate liver perfusion. Validation studies consisted of simultaneous measurements of hepatic perfusion with CT and with radiolabelled microspheres in rabbits at rest and after adenosine infusion. The feasibility and reproducibility of the CT method in humans was assessed by three observers in 10 patients without liver disease. In rabbits, significant correlations were observed between perfusion measurements obtained with CT and with microspheres (r=0.92 for total liver perfusion, r=0.81 for arterial perfusion and r=0.85 for portal perfusion). In patients, total liver plasma perfusion measured with CT was 112+/-28 ml.min(-1).100 ml(-1), arterial plasma perfusion was 18+/-12 ml.min(-1).100 ml(-1) and portal plasma perfusion was 93+/-31 ml.min(-1).100 ml(-1). The measurements obtained by the three observers were not significantly different from each other (P>0.1). Our results indicate that dynamic CT combined with a dual-input one-compartmental model provides a valid and reliable method for the non-invasive quantification of perfusion in the normal liver.     

A randomized comparison of the value of additional stenting after optimal balloon angioplasty for long coronary lesions: final results of the additional value of NIR stents for treatment of long coronary lesions (ADVANCE) study

OBJECTIVES: We sought to investigate the clinical benefit of additional stent implantation after achieving an optimal result of balloon angioplasty (BA) in long coronary lesions (>20 mm). BACKGROUND: Long coronary lesions are associated with increased early complications and late restenosis after BA. Stenting improves the early outcome, but stent restenosis is also related to both lesion length and stent length. METHODS: A total of 437 patients with a single native lesion 20 to 50 mm in length were included and underwent BA, using long balloons matched to lesion length and vessel diameter (balloon/artery ratio 1.1) to achieve a diameter stenosis (DS) <30% by on-line quantitative coronary angiography (QCA). "Bail-out stenting" was performed for flow-limiting dissections or >50% DS. Patients in whom an optimal BA result was achieved were randomized to additional stenting (using NIR stents) or no stenting. The primary end point was freedom from major adverse cardiac events (MACE) at nine months, and core laboratory QCA was performed on serial angiograms. RESULTS: Bailout stenting was necessary in 149 patients (34%) and was associated with a significantly increased risk of peri-procedural infarction (p < 0.02). Among the 288 randomized patients, the mean lesion length was 27+/-9 mm, and the vessel diameter was 2.78+/-0.52 mm. The procedural success rate was 90% for the 143 patients assigned to BA alone (control group), as compared with 93% in the 145 patients assigned to additional stenting (stent group), which resulted in a superior early minimal lumen diameter (0.54 mm, p < 0.001) and led to reduced angiographic restenosis (27% vs. 42%, p = 0.022). Freedom from MACE at nine months was 77% in both groups. CONCLUSIONS: A strategy of provisional stenting for long coronary lesions led to bailout stenting in one-third of patients, with a threefold increase in peri-procedural infarction. Additional stenting yielded a lower angiographic restenosis rate, but no reduction in MACE at nine months.     

Hemodynamic effects of intravenous diltiazem with impaired left ventricular function

The acute hemodynamic effects of intravenous diltiazem were studied in 8 patients with coronary artery disease, left ventricular (LV) failure (New York Heart Association functional class III), a rest ejection fraction (EF) less than 40% or a cardiac index less than 2.4 liters/min/m2. Hemodynamic measurements and LV angiograms were performed at rest before and after the administration of diltiazem, 0.5 mg/kg, administered at a speed of 5 mg/min. Diltiazem treatment induced a decrease in heart rate from 68 +/- 12 to 55 +/- 9 beats/min (p less than 0.001). Mean aortic pressure decreased from 94 +/- 14 to 81 +/- 15 mmHg (p less than 0.05). Thus, the pressure-rate product significantly decreased under the influence of the drug, from 8,791 +/- 2,465 to 6,342 +/- 1,808 beats mm Hg/min, (p less than 0.001). Diltiazem induced no significant change of LV end-diastolic pressure, pulmonary wedge pressure, cardiac index and LV stroke work index. Systemic vascular resistance decreased (p less than 0.01), whereas pulmonary vascular resistance showed no change. End-systolic volume diminished (p less than 0.02), which accounts for the increase of stroke volume and ejection fraction (p less than 0.001). Disorders of regional contractility were not aggravated by diltiazem, and even improved in individual cases. Thus, intravenous diltiazem may be used safely in patients with heart failure. However, in view of the marked bradycardic effects seen in some cases, heart rate should be carefully monitored.     

Reliability of a novel procedure to monitor the flexibility of lower limb muscle groups in highly-trained adolescent athletes

ObjectivesTo evaluate the reliability level of an innovative method using a standardized stretch force to assess the flexibility of lower limb muscle groups in highly-trained adolescent athletes and to examine whether interchanging the examiners affects the reliability of the measures.DesignRandomized test–retest study.Setting and participantsIn ten athletes, the flexibility of eight lower limb muscle groups was examined on two occasions on both sides and in two phases: a video capture by three distinct operators and an analysis by three distinct analysers. The reliability of the measures was assessed by the coefficient of variation (CV, 90% CI). Between-analysers and between-operators standardized differences (i.e., Cohen's d) were calculated.ResultsCV (%, 90% CI) were 8.3% (7.5; 9.3) for quadriceps, 3.3% (3.0; 3.7) for hamstrings, 7.2% (6.5–8.0) for adductors, 5.7% (5.1; 6.3) for gastrocnemius, 4.5% (4.0; 5.0) for soleus, 2.6% (2.3; 2.9) for hip flexors, 9.6% (8.6; 10.8) for hip medial rotators and 12.4% (12.2; 14.0) for hip lateral rotators. There was no substantial (i.e., Cohen's d < 0.2) difference in CV between all the possible operators/analysers combinations.ConclusionThis method has a moderate-to-good reliability level and is examiner-independent. It may be implemented in future injury prevention programs, in order to monitor the flexibility of highly-trained adolescent athletes.