Estimation of average flow in ungated 3D phase contrast angiograms

Three dimensional (3D) phase contrast angiograms contain velocity data, which is discarded after the reconstruction of the projections. In extension to earlier work on velocity quantification with ungated 2D phase data, this paper shows that a useful estimate of the average velocity and flow rate can be extracted from ungated 3D phase contrast angiograms. Simulations and experiments in a phantom and in vivo were performed. For pulsatile flow and strong spin saturation, an over-estimation of the flow rate at the net in-flow end of the imaging volume and underestimation at the net out-flow end was observed. Imaging at lower RF tip angles yielded flow rates close to the correct value within the entire imaging volume. In contrast to ungated 2D experiments, the flow rates determined by repeated 3D experiments showed no variation.     

The patella and tibial condyle position after combined and after closing wedge high tibial osteotomy

High tibial osteotomy changes the patella and tibial condyle position, which makes the subsequent total knee replacement technically demanding. From 1 January 1993 to 31 December 2000, combined osteotomy [After the first osteotomy made 2 cm distally to the joint line, a bone wedge is removed based laterally. Its tip ends at the center of the tibial condyle (half bone wedge). The distal part of the tibia is placed into the valgus position and the half bone wedge is placed into the gap opened medially.] was performed on 103 knees and closing wedge osteotomy was performed on 47 consecutive knees. Eighty combined (group A) and 41 closing wedge (group B) osteotomy were studied. All knees were assessed radiologically before surgery, in the 10th postoperative week, in the 12th postoperative month and at the time of the final follow-up (in group A—66.15 months, in group B—66.61 months). We examined the change of the femorotibial angle, of the patellar height according to the method of Insall and Salvati, of the tibial slope angle according to the method of Bonnin, of the tibial condylar offset according to the method of Yoshida and of the distance between the lateral tibial plateau and the top of the fibular head. In group A and B, the recurrence of the varus deformity was not noted and valgus alignment did not increase in any case. In group-A, the Insall–Salvati ratio remained unchanged in 65% of knees. The tibial slope angle decreased in both groups. There was correlation between the change of the tibial condylar offset and the angle of the correction in both groups. There was correlation between the change of the distance between the lateral tibial plateau and the top of the fibular head. After combined osteotomy, the transposition of the tibial condyle and the decrease of the distance between the lateral tibial plateau and the top of the fibular head was less than after closing wedge osteotomy, although the average angle of correction was more after combined osteotomy (11.835°), than after closing wedge osteotomy (9.465°). Theoretically, the recurrence of the varus deformity, the increase of the valgus alignment and (in majority of cases) the shortening of the patellar tendon do not compromise the likelihood of successful conversion to the subsequent total knee replacement, either after combined or after closing wedge osteotomy. The combined osteotomy does not lead to considerable transposition of the tibial condyle and to considerable lateral tibial bone loss; therefore, theoretically, the combined osteotomy does not impair the subsequent total knee replacement.     

Dentition planning with image-based occlusion analysis

Purpose To develop an easy-to-use, dentition planning method which is based on three-dimensional (3D) computer planning technology to replace conventional plaster-cast occlusion planning techniques. Methods The optimal dental occlusion is defined according to the condition of centric occlusion, i.e. after bringing occlusal surfaces of mandibular and opposing maxillary arches into identical 3D position. This identical position of occlusal surfaces represents the common reference frame for the 3D manipulation of all graphical elements. The planning procedure involves the following steps: (1) the optimal occlusal surface is approximated as triangle and localized both on the maxilla and mandible; (2) the original volumetric model is resampled according to the occlusal orientations; (3) the program reads in the models of ideal upper and lower dental arches from files, reshapes those to the patient anatomy and visualizes the local alignment on separate panels for mesiodistal and faciolingual inclinations. The final goal of the proposed method is to combine the requirements of functional and aesthetic designs and create an input for orthodontics, implantology and maxillofacial surgery. Results In the present study the optimal dental occlusion is created by image resampling after bringing the occlusal surfaces of mandibular and opposing maxillary arches into identical 3D position. This identical position of occlusal surfaces represents the common reference frame for manipulation of all graphical elements. Conclusions The proposed graphical environment was able to fit the elements of the ideal dentition curve to patient computed tomography under predefined centric occlusion. Rotation and scaling transformations of teeth were possible in the reformatted volumetric views about any of the axes of the teeth’s own reference space.     

Cardiovascular effects of the calcium sensitizer, levosimendan, in heart failure induced by rapid pacing in the presence of aortic constriction.

1. The haemodynamic effects of a novel cardiotonic drug, levosimendan, which has both calcium-sensitizing and phosphodiesterase III (PDE III) inhibitory properties, were studied in conscious dogs in which heart failure had been induced by prolonged cardiac pacing in the presence of aortic constriction. These effects were compared with those in sham-operated dogs with essentially normal cardiac function. 2. Eighteen mongrel dogs were instrumented for the measurement of left ventricular pressure (LVSP, LVEDP) and contractile function (dP/dt; dP/dt/P). In twelve dogs a balloon catheter, positioned in the thoracic aorta, was inflated producing an approximate 60% reduction in effective aortic diameter. Twenty min later rapid ventricular pacing (240 beats mean-1) was commenced and maintained for 48 h by means of a bipolar pacing electrode introduced into the right ventricle. This electrode served also for recording changes in the endocardial electrogram in the absence of pacing. Six of these dogs were used to evaluate the haemodynamic changes of pacing-induced heart failure; a further six of these dogs the haemodynamic changes elicited by levosimendan under these conditions. Six sham-operated dogs (group 2) served as controls. 3. In six dogs (group 1) the haemodynamic alterations were assessed after the development of heart failure. In the presence of aortic constriction, 48 h continuous rapid cardiac pacing resulted in a marked deterioration in left ventricular function which remained stable for at least 48 h after cessation of pacing. Thus, there was a marked reduction in LVSP (15%), +dP/dtmax (35%), -dP/dtmax (36%) and also in dP/dt/P (29%), whereas LVEDP was increased considerably (from 6.4 +/- 1.4 to 20.0 +/- 2.2 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Incidence over 10% of premature deliveries in Hungary (based on the experience in Borsod-Abaúj-Zemplń County)

The incidence over 10% of premature delivery in Hungary was studied. The cause which motivated this work was the fact that despite of several preventive and therapeutic measures the incidence e.g. in BAZ county surpassed even the average of the country. Professors of clinics in different countries of Europe as well as medical societies dealing with this question have been consulted about the matter of whether it was sufficient to consider a neonate a premature infant and the delivery a premature one solely on the basis of birth weight (under 2.500 g). Data of BAZ county proved that this determination was misleading and proposals are made concerning the modification on the basis of the examinations of the authors.     

Development and results of valve replacement surgery at the Városmajor Clinic 1976-1990 (retorospective clinical analysis)]

In Hungary valve replacement is still a major indication for heart surgery in adults. In the Cardiovascular Surgical Clinic of Semmelweis Medical University of Budapest from 1976 to 1990 2435 patients were operated for valve disease. Majority of the cases had single (aortic n = 856, mitral n = 912) or double (aortic + mitral n = 513) valve replacement. Over this 15 years period there have been many alterations in patients characteristics and surgical technique as well. In spite of the increasing mean age of patients the operative mortality has decreased (in the last 5 years period it was 2.7%, 5.5% and 7.9% in the three groups respectively). At the same time the number of patients requiring valve re-replacement or combined valve + coronary procedure has increased. The use of bioprosthetic valves has fallen below 10 percent from the 60--80 percent observed between 1976--1980. The analysis showes excellent surgical results in the field of valve replacement in Hungary.     

Mistyping of angiotensinogen M235T alleles.

Conflicting results are to be found in the literature on the relationship between the M235T polymorphism of the angiotensinogen (AGT) gene and hypertension. The controversy may be due to insufficient numbers of subjects, the variability of the inclusion criteria and the different genotype analysis methods used. We have experienced that the most frequently used, original polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) method involves significant uncertainties when the TT genotype is determined, independently of the restriction digestion. To make the determination more accurate, we improved the PCR by designing a new antisense primer containing only one mismatch instead of the two in the original protocol and also by adding DMSO to the PCR reaction mixture. The original and our improved methods were compared by using DNA from 123 patients: parallel determinations resulted in values of 33 MM, 90 MT and 0 TT with the original method and of 33 MM, 56 MT and 34 TT with the improved RFLP protocol. In summary, a plausible explanation for some of the conflicting data published on AGT M235T polymorphism may be that inaccuracies arose during the determination of the genotype.