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At least 775 records · Page 43Linked to original sources
PubMed2004

Lumbar spine stabilization with a thoracolumbosacral orthosis: evaluation with video fluoroscopy.

STUDY DESIGN: L3-L5 vertebral body motion was tracked fluoroscopically as individuals performed flexion-extension movements wearing different thoracolumbosacral orthoses (TLSOs). OBJECTIVE: To assess the effect of custom fitted TLSOs on lumbar vertebral body motion. SUMMARY OF BACKGROUND DATA: Several methods have been used to evaluate dynamic vertebral motion in vivo. Controversy remains regarding the utility of a TLSO in decreasing intervertebral motion in the lumbar spine. METHODS: Dynamic motion of the vertebral bodies was assessed fluoroscopically under four conditions: without a brace, with a custom fitted TLSO, with the TLSO and thigh extender at 0 degrees or 15 degrees. Intervertebral motion, i.e., the rotation of one vertebral body with respect to the adjacent body in the sagittal plane, throughout the flexion-extension cycle was used to assess the effect of each condition. RESULTS: The TSLO reduced both the total L3-L5 range of motion and the intervertebral motion at each individual level. Total rotation at L3 with respect to horizontal was reduced from 70 degrees without a brace to 50 degrees with a TLSO. Use of the thigh extender provided an additional reduction to 10 degrees. There was no difference between the 0 degrees and 15 degrees settings. Intervertebral motion was reduced by 40% at both L3-L4 and L4-L5 when comparing no brace to TLSO and an additional 15% when a thigh extender was added. CONCLUSIONS: A custom molded TLSO reduces both total L3-L5 motion and intervertebral motion in the lower lumbar spine. These effects are enhanced if a thigh extender is used.

Adult↗
PubMed2006

Radiation exposure during pedicle screw placement in adolescent idiopathic scoliosis: is fluoroscopy safe?

STUDY DESIGN: With institutional review board approval, prospective data were collected during fluoroscopically guided pedicle screw placement. OBJECTIVE: To estimate a surgeon's radiation exposure with all screw constructs during surgery to repair idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: To our knowledge, there is no established consensus regarding the safety of radiation exposure during fluoroscopically guided procedures. METHODS: A surgeon was outfitted intraoperatively with a thermoluminescent dosimeter to estimate radiation exposure to his whole body and thyroid gland. RESULTS: The index surgeon is projected to receive 13.49 mSv of whole body ionizing radiation and 4.31 mSv of thyroid gland irradiation annually. The National Council on Radiation Protection's current recommendations set lifetime dose equivalent limits for classified workers (radiologists) at 10 mSv per year of life and at 3 mSv for nonclassified workers (spinal surgeons). At the levels estimated, a surgeon beginning his/her career at age 30 years would exceed the lifetime limit for nonclassified workers in less than 10 years. The National Council on Radiation Protection limits the single-year maximum safe dosage to the thyroid to 500 mSv; the yearly exposure estimated here is significantly less. CONCLUSIONS: The spinal surgeon's intraoperative radiation exposure may be unacceptable. Spinal surgeons should be considered classified workers and monitored accordingly. Methods to lower radiation dosage seem strongly indicated.

Adolescent↗
PubMed2004

Magnetic resonance-guided placement of aortic stents grafts: feasibility with real-time magnetic resonance fluoroscopy.

PURPOSE: The artifact behavior of different aortic stent-grafts was evaluated with real-time magnetic resonance (MR) imaging, and the feasibility of real-time MR-guided stent-graft placement in the abdominal aorta was tested. MATERIALS AND METHODS: Seven different stent-grafts and their deployment systems were analyzed in an in vitro setting regarding their artifacts on different real-time MR images with cartesian, spiral, and radial k-space filling. The device and the real-time sequence with the fewest artifacts were used for an in vivo study in a swine model. In four animals, a straight aortic stent-graft was placed in the infrarenal abdominal aorta under real-time MR guidance. Results were controlled with MR angiography, multislice spiral computed tomography, and digital subtraction angiography. RESULTS: The in vitro study proved only one of the seven stent grafts (including deployment systems) to be suitable for real-time MR-guided intervention. MR-guided placement of the stent-grafts was possible in all animals. In one animal, the stent-graft dislocated during withdrawal of the deployment system as a result of a mismatch between stent-graft diameter and size of the infrarenal aorta. CONCLUSION: Real-time MR-guided placement of stent-grafts in the abdominal aorta with use of commercially available standard instruments is feasible. However, for clinical use, dedicated devices and deployment systems producing less artifacts are required.

Angiography, Digital Subtraction↗
PubMed1996

Accurate measurement of three-dimensional knee replacement kinematics using single-plane fluoroscopy.

A simple extension of a previously reported object recognition technique has been used to implement a six-degree-of-freedom position/orientation estimator for the measurement of knee replacement motion from two-dimensional (2-D) fluoroscopic images. Computer modeling studies and controlled mechanical tests were performed to assess the accuracy of the technique. The results indicate that knee rotations can be measured with an accuracy of approximately one degree and that sagittal plane translations can be measured with an accuracy of approximately 0.5 mm. The measurement technique is uniquely well suited for performing dynamic kinematic measurements on individuals with knee replacements, and for performing comparative studies among subjects with different designs of knee replacements.

Computer Simulation↗
PubMed2005

Fluoroscopy-based 3-D reconstruction of femoral bone cement: a new approach for revision total hip replacement.

In revision total hip replacement the removal of the distal femoral bone cement can be a time consuming and risky operation due to the difficulty in determining the three-dimensional (3-D) boundary of the cement. We present a new approach to reconstruct the bone cement volume by using just a small number of calibrated multiplanar X-ray images. The modular system design allows the surgeon to react intraoperatively to problems arising during the individual situation. When encountering problems during conventional cement removal, the system can be used on demand to acquire a few calibrated X-ray images. After a semi-automatic segmentation and 3-D reconstruction of the cement with a deformable model, the system guides the surgeon through a free-hand navigated or robot-assisted cement removal. The experimental evaluation using plastic test implants cemented into anatomic specimen of human femoral bone has shown the potential of this method with a maximal error of 1.2 mm (0.5 mm RMS) for the distal cement based on just 4-5 multiplanar X-ray images. A first test of the complete system, comparing the 3-D-reconstruction with a computed tompgraphy data set, confirmed these results with a mean error about 1 mm.

Arthroplasty, Replacement, Hip↗
PubMedDate not supplied

Fluoroscopy-assisted placement of peritoneal dialysis catheters by nephrologists.

In the early 1950s and 1960s, peritoneal dialysis (PD) was used primarily to treat patients with acute renal failure. Continuous ambulatory peritoneal dialysis (CAPD) was introduced in 1976 and continues to gain popularity as an effective method of renal replacement therapy for patients with end-stage renal disease (ESRD). The PD catheter is inserted into the abdominal cavity either by a surgeon, interventional radiologist, or nephrologist. We have adopted a percutaneous approach with fluoroscopic guidance for PD catheter insertion that is easy, safe, and provides good patency and infection rate results. In this article we describe the technique and our results. From August 2000 to May 2003, 34 PD catheters out of 36 were successfully inserted using the percutaneous fluoroscopic technique in selected patients referred from the nephrology clinic. All the PD catheters were placed in our Interventional Nephrology Vascular Suite by nephrologists.

Catheterization↗
PubMed2005

Theoretical accuracy of model-based shape matching for measuring natural knee kinematics with single-plane fluoroscopy.

Quantification of knee motion under dynamic, in vivo loaded conditions is necessary to understand how knee kinematics influence joint injury, disease, and rehabilitation. Though recent studies have measured three-dimensional knee kinematics by matching geometric bone models to single-plane fluoroscopic images, factors limiting the accuracy of this approach have not been thoroughly investigated. This study used a three-step computational approach to evaluate theoretical accuracy limitations due to the shape matching process alone. First, cortical bone models of the femur tibia/fibula, and patella were created from CT data. Next, synthetic (i.e., computer generated) fluoroscopic images were created by ray tracing the bone models in known poses. Finally, an automated matching algorithm utilizing edge detection methods was developed to align flat-shaded bone models to the synthetic images. Accuracy of the recovered pose parameters was assessed in terms of measurement bias and precision. Under these ideal conditions where other sources of error were eliminated, tibiofemoral poses were within 2 mm for sagittal plane translations and 1.5 deg for all rotations while patellofemoral poses were within 2 mm and 3 deg. However, statistically significant bias was found in most relative pose parameters. Bias disappeared and precision improved by a factor of two when the synthetic images were regenerated using flat shading (i.e., sharp bone edges) instead of ray tracing (i.e., attenuated bone edges). Analysis of absolute pose parameter errors revealed that the automated matching algorithm systematically pushed the flat-shaded bone models too far into the image plane to match the attenuated edges of the synthetic ray-traced images. These results suggest that biased edge detection is the primary factor limiting the theoretical accuracy of this single-plane shape matching procedure.

Algorithms↗