4D rotational x-ray imaging of wrist joint dynamic motion.

Current methods for imaging joint motion are limited to either two-dimensional (2D) video fluoroscopy, or to animated motions from a series of static three-dimensional (3D) images. 3D movement patterns can be detected from biplane fluoroscopy images matched with computed tomography images. This involves several x-ray modalities and sophisticated 2D to 3D matching for the complex wrist joint. We present a method for the acquisition of dynamic 3D images of a moving joint. In our method a 3D-rotational x-ray (3D-RX) system is used to image a cyclically moving joint. The cyclic motion is synchronized to the x-ray acquisition to yield multiple sets of projection images, which are reconstructed to a series of time resolved 3D images, i.e., four-dimensional rotational x ray (4D-RX). To investigate the obtained image quality parameters the full width at half maximum (FWHM) of the point spread function (PSF) via the edge spread function and the contrast to noise ratio between air and phantom were determined on reconstructions of a bullet and rod phantom, using 4D-RX as well as stationary 3D-RX images. The CNR in volume reconstructions based on 251 projection images in the static situation and on 41 and 34 projection images of a moving phantom were 6.9, 3.0, and 2.9, respectively. The average FWHM of the PSF of these same images was, respectively, 1.1, 1.7, and 2.2 mm orthogonal to the motion and parallel to direction of motion 0.6, 0.7, and 1.0 mm. The main deterioration of 4D-RX images compared to 3D-RX images is due to the low number of projection images used and not to the motion of the object. Using 41 projection images seems the best setting for the current system. Experiments on a postmortem wrist show the feasibility of the method for imaging 3D dynamic joint motion. We expect that 4D-RX will pave the way to improved assessment of joint disorders by detection of 3D dynamic motion patterns in joints.

Objective computerized determination of the minimum cross-sectional area of the nasal passage on computed tomography.

OBJECTIVES/HYPOTHESIS: Current methods that measure cross-sectional areas of the nasal passage on computed tomography (CT) do not determine the minimum cross-sectional area that may be an important factor in nasal airway resistance. Objective measurement of the dimensions of the nasal passage may help in the diagnosis, as well as the choice and evaluation of surgical treatment for upper airway insufficiencies. STUDY DESIGN: Retrospective and clinical study. METHODS: Software was developed that automatically calculates the minimum cross-sectional area of the nasal passage on CT. RESULTS: Evaluation shows that the minimization algorithm in the software reliably calculates the position and orientation of the oblique plane on which the minimum cross-section lies. CONCLUSION: The developed method may be used for objective and observer-independent evaluation of surgical treatment options.

Investigation of training needs for functional endoscopic sinus surgery (FESS).

The use of simulators for training FESS may in the future offer substantial advantages like increased exposure to difficult scenarios, reduced learning curves, and reduced costs. Training simulators may range from very simple, involving only visual simulation, to more complex, involving haptic simulation or force feedback. To effectively employ these training means, insight is needed into the training needs for FESS procedure. A study was carried out to investigate which subtasks of FESS are hardest to perform and have the longest learning curve. A questionnaire was distributed among two groups of Ear, Nose and Throat (ENT) surgeons participating in a basic, as well as in an advanced sinus surgery course. Results showed that tasks related to spatial orientation are judged as hardest, whereas manual tasks are considered less difficult. These results suggest that simulators will not necessarily need haptic feedback to train the most important knowledge and skills needed for FESS.

Effects of head-slaved navigation and the use of teleports on spatial orientation in virtual environments.

The type of navigation interface in a virtual environment (VE)--head slaved or indirect--determines whether or not proprioceptive feedback stimuli are present during movement. In addition, teleports can be used, which do not provide continuous movement but, rather, discontinuously displace the viewpoint over large distances. A two-part experiment was performed. The first part investigated whether head-slaved navigation provides an advantage for spatial learning in a VE. The second part investigated the role of anticipation when using teleports. The results showed that head-slaved navigation has an advantage over indirect navigation for the acquisition of spatial knowledge in a VE. Anticipating the destination of the teleport prevented disorientation after the displacement to a great extent but not completely. The time that was needed for anticipation increased if the teleport involved a rotation of the viewing direction. This research shows the potential added value of using a head-slaved navigation interface--for example, when using VE for training purposes--and provides practical guidelines for the use of teleports in VE applications.

Evaluation of vascular and interventional procedures with time-action analysis: a pilot study.

PURPOSE: To provide an objective method to measure the efficiency of vascular and interventional procedures. MATERIALS AND METHODS: The time-action analysis method is defined for peripheral vascular and interventional procedures. A taxonomy of actions is defined, geared specifically toward these procedures. The actions are: start-up/wrap-up, exchange, navigate, image, diagnose, treat, handle material, wait, compress puncture site, and unclassified. The recording method and analysis techniques are described. To show the type of data that can be obtained, the time-action analysis of 30 procedures is presented. RESULTS: The results provide a detailed picture of the time spent on various actions. Of all actions, the most time is spent on compressing the puncture site (18.5%), whereas the highest frequency of actions are for exchange of catheters, guide wires, and sheaths (20.4 times per procedure). Radiation exposure can be analyzed in detail, which can yield directions for possible reduction. For instance, 5.2%-8.3% of the total radiation exposure occurs during preparation of imaging to adjust the position of the patient table and set the image intensifier diaphragm. CONCLUSION: Time-action analysis provides an objective measurement method to monitor and evaluate vascular and interventional procedures. Potential applications and limitations of the technique are discussed.