Fluoroscopic Measurements Research Articles

Predicting urethral area from video‐urodynamics in women with voiding dysfunction

Mathematical models are useful for developing predictive parameters for characterizing the biomechanics of voiding dysfunction. The goal of this project was to test a one-dimensional steady flow model used to predict the minimum cross-sectional urethral area from urodynamic data. Nine adult female subjects underwent video-urodynamic testing. By using Bernoulli's formula and the Torricelli theorem, the minimum urethral area was predicted from pressure and flow rate at the moment of maximum flow rate during voiding. This prediction was compared with the minimum cross-sectional area of the urethra, which was calculated from minimum urethral diameter as measured from fluoroscopy, assuming a circular cross-section. The maximum flow rate during voiding was 14.4 +/- 3.0 mL/sec. Mean bladder, abdominal, and detrusor pressures simultaneous with maximum flow rate were 63 +/- 7, 29 +/- 6, and 33 +/- 6 cm H(2)O, respectively. Mean minimum cross-sectional area of the urethra from fluoroscopy was 8.0 +/- 2.0 mm(2). Mean minimum cross-sectional area of the urethra predicted by the mathematical model was 5.0 +/- 1.0 mm(2) using bladder pressure and 7.0 +/- 2.0 mm(2) using detrusor pressure. There were no significant differences between the three cross-sectional area measures. However, when area predictions were expressed as percentage of fluoroscopic measurements, the estimate from detrusor pressure (97 +/- 13%) was significantly larger than the estimate from bladder pressure (69 +/- 7%). A steady flow model is accurate enough on average to describe urine flow in the urethra. However, it may not be sufficiently accurate to aid in diagnosis of individuals.

Incision placement for intramedullary tibial nailing: an anatomic study.

For intramedullary nailing of tibial shaft fractures, a recent study has determined that the entry site should be just medial to the lateral tibial spine at the anterior margin of the articular surface. Gaining access to this site is often through a medial parapatellar or transpatellar approach. Several studies have indicated that a transpatellar approach may contribute to anterior knee pain. Our study sought to use anatomic measurement to determine the ideal incision site for insertion of an intramedullary tibial nail. DESIGN Part I: survey of Orthopaedic Trauma Association (OTA) members. Part II: anatomic study. A Level I trauma center in Sacramento, California. Part I: OTA members. Part II: a group of 56 healthy volunteers. Part I: questionnaire sent to OTA members. Part II: clinical examination and radiographic analysis. Part I: responses to questionnaire. Part II: anatomic measurements. Part I: based on a questionnaire, OTA members use at least one or more approaches to access their preferred tibial nail entry site. Fifty-seven percent use only one type of approach in all cases. Part II: the authors performed a clinical and radiographic study in 56 volunteers (112 knees) to determine the relationship of the lateral tibial spine to the patellar tendon. On the basis of this information, the tendon was divided into thirds to account for the three most common surgical approaches. The entry site was in the lateral zone in 29 knees, the middle zone in 75 knees, and the medial zone in 8 knees. If divided equally into purely a medial or lateral zone to avoid a transpatellar approach, the starting point fell into the medial zone in 42 knees and the lateral zone in 70 knees. Individual variations in patellar tendon anatomy should be considered when choosing the proper entry site for tibial nailing. Based on the assumption that the ideal entry point for tibial nailing is just medial to the tibial spine at the anterior margin of the articular surface, a preoperative fluoroscopic measurement before incision can guide the surgeon as to whether a medial parapatellar, transpatellar, or lateral parapatellar approach provides the most direct access to this entry site. The routine use of a single approach for all tibial nails may no longer be justified.

In vivo kinematics of cruciate-retaining and -substituting knee arthroplasties

A fluoroscopic measurement technique has been used to provide detailed three-dimensional kinematic assessment of knee arthroplasty function during a step-up activity. Three groups of knee arthroplasty subjects with excellent clinical outcomes and similar ranges of motion were evaluated. Each group received different prosthetic components and surgical treatments of the posterior cruciate ligament (PCL). Group 1 had relatively flat articular surfaces with retention of the bony insertion of the PCL, group 2 had similar articular geometry but recessed the PCL without retaining the bony insertion, and group 3 had prostheses with greater sagittal conformity and post/cam substitution of the sacrificed PCL. Although none of the knees exhibited normal knee kinematics, the ranges of axial rotation and condylar translation for group 1 were similar to ranges previously reported for normal and anterior cruciate-deficient knees. Axial rotations and condylar translations decreased when the PCL was surgically recessed or substituted. The smallest kinematic ranges were observed in group 3. The results indicate that both prosthetic component selection and surgical technique have a significant effect on prosthetic knee kinematics during functional activities.

Effect of alcohols on catalysis by dodecyl sulfate micelles

We studied the kinetics of the acid denitrosation of N-nitroso-N-methyl-p-toluenesulfonamide when catalyzed by sodium dodecyl sulfate (SDS) or hydrogen dodecyl sulfate (HDS) micelles in the presence of one of eight alcohols, with equimolar alcohol and surfactant concentrations. In preliminary experiments, the effects of the alcohols on micellar structure were investigated by conductimetric determination of micellar ionization and, in some cases, by fluoroscopic measurement of mixed micelle aggregation numbers

Lumbar posterior ligament involvement during extremely heavy lifts estimated from fluoroscopic measurements

The mechanical role of the lumbar posterior ligaments during lifting tasks remains controversial. This study was designed to assess the ligament and disc contribution in resisting trunk flexion moment during extremely heavy lifts performed by national class powerlifters. Direct measurements of lumbar vertebrae kinematics in sagittal plane were obtained from videofluoroscopy utilizing multiple digitizing, correction for optical distortions and digital filtering. Four experienced powerlifters executed three trials, resulting in about 72 mA s of total radiation exposure. In the first trial, joint angles were measured when subjects fully flexed their spines to a point where the passive tissues resisted the flexor moment creating myoelectric silence in the extensor musculature. Next, two conventional deadlift style lifts were executed with the barbell load ranging from 183.7 to 210.9 kg. Four vertebral corners were digitized at a sampling rate of 30 Hz. The relative intervertebral joint angles, distance between the ligament attachment points, shearing and compressive displacements were calculated from a rigid body motion approach. Analysis revealed that except for one trial of one subject, they accomplished their lifts with an amount of lumbar flexion between 1.5 and 13° less than they demonstrated during full flexion. Resultant ligament lengths at the beginning of the lifts ranged from 56.1 to 99.8% of their lengths when the trunk was fully flexed. It was concluded that ligaments did not strain sufficiently to contribute substantial resistance to the trunk flexion moment, relegating this responsibility to the musculature.

Effects of magnetic fields on the light yield of scintillators

We describe studies of the light yield of scintillators as a function of an externally applied magnetic field. The studies involved using fluoroscopic measurements, measuring indices of refraction, employing a wide variety of sources from fission fragments to cosmic rays, and making measurements as a function of the scintillator type and thickness and of the direction of the applied field. We observed the light yield to increase with increasing magnetic field, independent of geometry or direction of the magnetic field. The effect was much larger in acrylic scintillator than in polyvinyltoluene or polystyrene-based scintillator. We believe that the change in the light yield is due to a local light saturation of the material. As the magnetic field increases, the low-energy electrons spiral away from each other and the light yield increases.

Videofluoroscopic assessment of muscle fiber shortening in the in situ canine diaphragm

We tested the hypothesis that dynamic shortening of the costal diaphragm can be accurately estimated from measurements of the radiographic width of the zone of apposition (WZapp) by studying seven supine anesthetized dogs. Both muscle fiber length, represented by the distance between implanted radiopaque markers, and WZapp were measured from digitized recordings of fluoroscopic images utilizing interactive computer software. The WZapp was highly correlated with the length of costal fibers during active respiration in all animals (mean R2 = 0.94). The accuracy in the prediction of fiber length and shortening during breathing is enhanced by inclusion of additional variables describing the displacement of the abdominal wall and the resting geometric orientation of the fibers. We conclude that dynamic fluoroscopic measurement of WZapp is a valuable technique for estimating dynamic diaphragm fiber length and shortening. Depending on the experimental circumstances, WZapp may be a more easily acquired indicator of diaphragm shortening than other variables that have been previously utilized. As such, it may provide a suitable approach to assess active shortening of the diaphragm in humans.

Fluoroscopic measurement of tibial torsion in adults

Three methods based on the fluoroscopic technique for measurement of tibial torsion were analyzed. The measurements were performed bilaterally in 100 normal adults. The values for bilateral tibial torsion were recorded and the values for the difference in torsion between the right and left tibia were calculated. The standard error of all investigated methods was found to be lower than published figures for computerized tomography and ultrasonic methods. The method found to be most convenient for routine use also presented the best repeatability. With this method, the standard error of a single determination of tibial torsion was estimated to be 0.7 degrees.

Capabilities of a Real-Time Digital Video Processor

Advances in high speed video digitizing and digital processing hardware combined with stored microprocessor programs has led to the development of compact, portable and relatively low cost equipment capable of performing a number of useful realtime operations on fluoroscopic video. Through its ability to compute, store and display difference images as well as perform electronic image integration in real-time the equipment described in this paper can aid in diagnosis of diseased blood-vascular systems. Perhaps more importantly, the rapid acquisition of quantitative high resolution imagery combined with subsequent digital image analysis provides the basis for quantitative near realtime presentation of quantitative parameters such as ejection fraction, wall motion and blood velocity. In addition to a description of the design and operation of the unit, preliminary experimental data are presented showing its performance capabilities in conjunction with medical fluoroscopic signals. Extensions of this technology to additional fluoroscopic image measurements are pointed out.