Stefan M. Lupkiewicz

A framework for three-dimensional time-varying reconstruction of the human left ventricle: sources of error and estimation of their magnitude.

Abstract This report summarizes development of a computer/ultrasound system to graphically reconstruct the contracting human left ventricle in three dimensions and calculate indices of cardiac performance. The three-dimensional reconstruction is performed by realignment of five cross-sectional two-dimensional echograms along a single longitudinal section. The spatial position of the cross sections is recorded by a specially developed indexing arm. Cross sections are then realigned perpendicular to the long axis and parallel to each other by the computer. Points at 30° intervals are chosen from the inner and outer muscle boundaries of a cross section and connected by straight lines. Thus areas can be calculated simply by summation of triangular areas with vertices at the origin. Volumes can then be calculated using a modified Simpsons rule. To test these computer programs three hypothetical time-varying computer-generated left ventricular models were developed. Effects of six major anticipated sources of error were determined by systemic introduction of simulated measurement errors into data for these hypothetical models. These results demonstrate that this system is practical for the three-dimensional reconstruction of the left ventricle, that volumes and derived indices of ventricular performance can be calculated, and that anticipated sources of error result in relatively small deviations from true values.

Evaluation of a three-dimensional reconstruction to compute left ventricular volume and mass☆

This study tests the accuracy of a model to calculate left ventricular volume (LVV) and muscle volume (MV) when optimal data were used. These volumes were calculated using endocardial and epicardial borders traced from photos of cross sections of 20 animal (dog, goat and pig) hearts. A pyramid summation algorithm was used to perform a 3-dimensional (3-D) reconstruction based on 5 short-axis views, thus providing computer volume estimates. These were compared with the true (T) ventricular volumes determined by water filling of the cavity and the true MV based on weight. Because each heart was sliced in 5 planes, the appropriateness of the algorithm for MV could be tested for 6 regions. The pyramid summation algorithm consistently underestimated MV at the base and apex, but was accurate from the midmitral valve to the inferior papillary muscle region. Consequently, the total MV was computed as the midventricular MV, plus base and apex volumes computed from regression equations. Results showed that 3-D reconstruction resulted in a regression of LVVT = 1.02LVV3D + 10.30 ml with r = 0.987 for the chamber of MVT = 1.05 MV3D - 9.78 ml, with r = 0.967. It is concluded that the pyramid summation algorithm can accurately estimate volumes from spatially registered short-axis data with 95% prediction limits about the mean of the data of +/- 10 ml for left ventricular chamber volume and +/- 17.6 ml for MV.

Internal derangement of the TMJ: Changes associated with mandibular repositioning and orthodontic therapy

Because of its apparent success in relieving symptoms, especially pain, anterior mandibular repositioning therapy is a popular mode of nonsurgical treatment for patients with painful, clicking internal derangement of the temporomandibular joint. Posterior open bites are a frequent consequence of such therapy and may necessitate either continued appliance wear or closure by equilibration, prosthetics, or orthodontics. The anatomic and functional changes that occur subsequent to mandibular repositioning during orthodontic closure of the posterior open bite are not well understood. A case of a patient with a Class II, deep bite malocclusion and painful internal derangement of the TMJ is presented. Transcranial and cephalometric radiographs, arthrograms, and mandibular movement recordings were obtained before treatment and after both repositioning therapy and orthodontic treatment. Regarding occlusal improvement and pain relief, the treatment was successful. However, not all of the changes that occurred during repositioning therapy were maintained after orthodontic treatment. The strategy used in this case (mandibular repositioning/orthodontic finishing) was evaluated by an examination of these anatomic and functional changes with a discussion centered on the possible mechanisms involved.