Intermanual interactions in discrete and periodic bimanual movements with same and different amplitudes

In two experiments we compared intermanual interactions in discrete and periodic movements with same and different amplitudes. In the first experiment there was only a weak amplitude assimilation in first cycles of movements with 1, 3, and 10 cycles, but a strong assimilation in later cycles. Whereas movement times of concurrent short-amplitude and long-amplitude movements were different in first cycles, in the later cycles they were essentially identical. In the second experiment the timed-response procedure was used to study the specification of same and different amplitudes of discrete reversal movements and periodic movements with three cycles. Differences in the time courses of amplitude specifications were only small. In periodic movements a dependence of amplitudes on the preparation interval was seen not only in the first cycles, but also in the later ones. However, in the later cycles the characteristic dependence of assimilation effects and intermanual correlations on the preparation interval was absent. Taken together, these findings strongly suggest that intermanual interactions arise transiently in the specification of both discrete and periodic movements, and that additional kinds of interactions become effective during execution of periodic movements.     

Improved correlation of histological data with DCE MRI parameter maps by 3D reconstruction, reslicing and parameterization of the histological images

Due to poor correlation of slice thickness and orientation, verification of radiological methods with histology is difficult. Thus, a procedure for three-dimensional reconstruction, reslicing and parameterization of histological data was developed, enabling a proper correlation with radiological data. Two different subcutaneous tumors were examined by MR microangiography and DCE-MRI, the latter being post-processed using a pharmacokinetic two-compartment model. Subsequently, tumors were serially sectioned and vessels stained with immunofluorescence markers. A ray-tracing algorithm performed three-dimensional visualization of the histological data, allowing virtually reslicing to thicker sections analogous to MRI slice geometry. Thick slices were processed as parameter maps color coding the marker density in the depth of the slice. Histological 3D reconstructions displayed the diffuse angioarchitecture of malignant tumors. Resliced histological images enabled specification of high enhancing areas seen on MR microangiography as large single vessels or vessel assemblies. In orthogonally reconstructed histological slices, single vessels were delineated. ROI analysis showed significant correlation between histological parameter maps of vessel density and MR parameter maps (r=0.83, P=0.05). The 3D approach to histology improves correlation of histological and radiological data due to proper matching of slice geometry. This method can be used with any histological stain, thus enabling a multivariable correlation of non-invasive data and histology.Kiessling and Le-Huu contributed equally.     

Quantification of aortic elasticity: development and experimental validation of a method using computed tomography

Aortic distensibility depending on aortic cross-sectional area changes is an important parameter for the grading of vascular diseases. This study measured aortic area changes by multidetector computed tomography. An image reconstruction algorithm was developed to assess aorta diameter and area as a function of the cardiac cycle with sufficient time resolution along the entire length of the aorta by four-detector row computed tomography. The algorithm was tested on porcine aortic specimens and compared with an optical reference method. The error of the relative vessel area change comparing the two methods was found to be about 3%. Initial tests on patient datasets indicate that clinical application is feasible. The proposed method has the advantage that it can easily be integrated into a modified routine CT angiography study and allows the measurement of aortic cross-sectional area changes.     

Novel spherical phantoms for Q‐ball imaging under in vivo conditions

For the validation of complex diffusion imaging techniques like q‐ball imaging that aim to resolve multiple fiber directions, appropriate phantoms are highly desirable. However, previous q‐ball imaging phantoms had diffusion anisotropies well below those of in vivo white matter. In this work, fiber phantoms of well‐defined geometry are presented. The fibers are wound on a spherical spindle yielding high packing densities and consequently high diffusion anisotropies (fractional anisotropy 0.93 ± 0.02 at b = 500 s/mm²). Phantoms with 90° and 45° crossing angle were constructed both with two crossing types. In the “stacked” crossing, two fiber strings were wound consecutively to simulate two touching fibers, in the “interleaved” crossing, fibers were wound alternately. The stacked crossing allows the alteration of partial volumes, whereas the interleaved crossing provides constant partial volumes, allowing e.g. the easy alteration of the SNR by varying the slice thickness. Exemplary q‐ball imaging validation measurements using different b‐values and slice thicknesses are presented. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Simulation-based comparison of two approaches frequently used for dynamic contrast-enhanced MRI

Purpose  

The purpose was to compare two approaches for the acquisition and analysis of dynamic-contrast-enhanced MRI data with respect to differences in the modelling of the arterial input-function (AIF), the dependency of the model parameters on physiological parameters and their numerical stability. Eight hundred tissue concentration curves were simulated for different combinations of perfusion, permeability, interstitial volume and plasma volume based on two measured AIFs and analysed according to the two commonly used approaches. The transfer constants (Approach 1) K ^trans and (Approach 2) k _ep were correlated with all tissue parameters. K ^trans showed a stronger dependency on perfusion, and k _ep on permeability. The volume parameters (Approach 1) v _e and (Approach 2) A were mainly influenced by the interstitial and plasma volume. Both approaches allow only rough characterisation of tissue microcirculation and microvasculature. Approach 2 seems to be somewhat more robust than 1, mainly due to the different methods of CA administration.     

Optically detunable,inductively coupled coil for self‐gating in small animal magnetic resonance imaging

An inductively coupled coil concept is presented, which improves the compensation of physiological motion by the self‐gating (SG) technique. The animal is positioned in a conventional volume coil encompassing the whole animal. A small, resonant surface coil (SG‐coil) is placed on the thorax so that its sensitive region includes the heart. Via inductive coupling the SG‐coil amplifies selectively the MR signal of the beating heart. With an optical detuning mechanism, this coupling can be switched off during acquisition of the MR image information, whereas it is active during SG data sampling to provide the physiological information. In vivo experiments on a mouse show an amplification of the SG signal by at least 40%. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Real-time X-ray-based 4D image guidance of minimally invasive interventions

Objective

A new technology is introduced that enables real-time 4D (three spatial dimensions plus time) X-ray guidance for vascular catheter interventions with acceptable levels of ionising radiation.

Methods

The enabling technology is a combination of low-dose tomographic data acquisition with novel compressed sensing reconstruction and use of prior image information. It was implemented in a prototype set-up consisting of a gantry-based flat detector system. In pigs (n?=?5) angiographic interventions were simulated. Radiation dosage on a per time base was compared with the “gold standard” of X-ray projection imaging.

Results

Contrary to current image guidance methods that lack permanent 4D updates, the spatial position of interventional instruments could be resolved in continuous, spatial 4D guidance; the movement of the guide wire as well as the expansion of stents could be precisely tracked in 3D angiographic road maps. Dose rate was 23.8 μGy/s, similar to biplane standard angiographic fluoroscopy, which has a dose rate of 20.6 μGy/s.

Conclusion

Real-time 4D X-ray image-guidance with acceptable levels of radiation has great potential to significantly influence the field of minimally invasive medicine by allowing faster and safer interventions and by enabling novel, much more complex procedures for vascular and oncological minimally invasive therapy.

Key Points

? Real-time 4D (three spatial dimensions plus time) angiographic intervention guidance is realistic. ? Low-dose tomographic data acquisition with special compressed sensing-based algorithms is enabled. ? Compared with 4D CT fluoroscopy, this method reduces radiation to acceptable levels. ? Once implemented, vascular interventions may become safer and faster. ? More complex intervention approaches may be developed.     

Improved Detection and Analysis of Sensed and Paced Events in Dual Chamber Pacemakers with Extended Memory Function A Prospective Multicenter Trial in 626 Patients

Patients and Methods: This prospective study analyzed the incidence of atrial arrhythmias in a population of 626 patients in 173 medical centers of eleven European countries and Japan with indication for a dual chamber pacemaker system. The accuracy of the new Automatic Interpretation for Diagnosis Assistance (AIDA) program which is included in Chorus pacemakers was evaluated and the AIDA analysis was compared to and proven with Holter monitoring. Data stored in the pacemakers' memories for the first 24 hours (D1) were compared with simultaneously recorded 24-hour surface electrocardiograms, and data stored over the following 28 days (D28) were examined against reported intercurrent symptoms. Results: At D1, atrial arrhythmias were detected by AIDA in 60 out of 626 patients (12%), consisting of atrial fibrillation (n = 29), atrial flutter (n = 4), and miscellaneous arrhythmias (n = 17), and closely corroborated by Holter monitoring (sensitivity 93.7%, specificity 94.9%). At D28, 149 out of 386 patients (49%) had had episodes of automatic mode switch prompted by atrial arrhythmias. Symptoms were reported by 81 patients (54%), 92 (62%) had no histories of atrial arrhythmias, and 57 patients (38%) were neither symptomatic nor had histories of atrial arrhythmias. An inverse relationship was found between the number of atrial paced events and the occurrence of atrial arrhythmias (p < 0.001). A history of atrial arrhythmias and older age were associated with a higher risk of atrial arrhythmias (p < 0.05). In contrast, gender, hypertension, concomitant heart disease, or type of atrial lead fixation system were not related with the occurrence of atrial arrhythmias. Conclusion: AIDA allowed to confirm, or disprove, the occurrence of atrial arrhythmias as a source of symptoms reported during long-term follow-up. It could also be used to examine the efficacy of antiarrhythmic therapy, and be of assistance when weighing the needs for anticoagulation in patients experiencing asymptomatic atrial arrhythmias. Patienten und Methode: Die vorliegende prospektive Studie untersucht die Inzidenz von Vorhofarrhythmien in einer Population von 626 Patienten mit der Indikation zur Implantation eines Zwei-Kammer-Schrittmachersystems, durchgeführt in 173 medizinischen Zentren in elf europäischen Ländern und in Japan. Die Genauigkeit des neuen Programms zur Automatischen Interpretation der Diagnose-Analyse (Automatic Interpretation for Diagnosis Assistance, AIDA) für Chorus-Herzschrittmacher wurde evaluiert und die AIDA-Analyse mit dem Langzeitelektrokardiogramm (Holter) verglichen und überprüft. Die im Schrittmacher gespeicherten Daten der ersten 24 Stunden (D1) wurden mit einem simultan aufgezeichneten 24-Stunden-Langzeitelektrokardiogramm verglichen. Die Daten der folgenden 28 Tage (D28) wurden in Bezug auf die vom Patienten angegebenen Symptome untersucht. Ergebnisse: Im Zeitraum von D1 wurden bei 60 von 626 Patienten (12%) Vorhofarrhythmien mit dem AIDA-Programm erfasst, bei denen es sich um Vorhofflimmern (n = 29), Vorhofflattern (n = 4) und gemischte Vorhofarrhythmien (n = 17) handelte. Die Auswertung der Langzeitelektrokardiogramme bestätigte die Diagnose mit einer Sensitivität von 93,7% und einer Spezifität von 94,9%. Im Zeitraum von D28 zeigten 149 von 386 Patienten (49%) eine Episode einer Vorhofarrhythmie, die zu einem Wechsel in den Fallback-Modus führte. Symptome wurden von 81 Patienten (54%) angegeben: 92 Patienten (62%) hatten bisher in der Vorgeschichte keine Vorhofarrhythmien, 57 Patienten (38%) hatten bisher weder Symptome noch Vorhofarrhythmien. Eine inverse Beziehung zwischen der Anzahl stimulierter Vorhofereignisse und dem Auftreten von Vorhofarrhythmien konnte nachgewiesen werden (p < 0,0001). Eine Historie von Vorhofarrhythmien sowie höheres Lebensalter waren assoziiert mit einem höheren Risiko für das Auftreten von Vorhofarrhythmien (p < 0,05). Im Gegensatz dazu zeigte sich für die Faktoren Geschlecht, Bluthochdruckkrankheit, begleitende Herzerkrankung oder die Art der Fixierung der Vorhofelektrode (passiv oder aktiv) kein Bezug zum Auftreten von Vorhofarrhythmien. Schlussfolgerung: Das AIDA-Programm erlaubt das Auftreten von Vorhofarrhythmien als Ursache von Symptomen in der Nachsorge zu bestätigen oder zu widerlegen. Es kann auch genutzt werden, um die Effektivität einer antiarrhythmischen Therapie zu untersuchen und die Notwendigkeit einer Antikoagulation bei Patienten mit asymptomatischen Vorhofarrhythmien abzuwägen.     

Surgical management of type III thoracic shotgun injury

Summary Reporting the case of a short-range severe thoracic shotgun injury the differentiated management of this trauma is discussed. Indication for operative exploration under emergency conditions is hemorrhagic shock, perforation of esophagus/stomach and pericardial tamponade. Even under a toxicological point of view there is no indication for emergency revisions.