Relative Conspicuity of Gadolinium-Based Contrast Agents in Interventional Pain Procedures.

Objective: To assess the relative radiographic conspicuity of gadolinium-based contrast agents (GBCAs) that may be used in spinal injection procedures when iodine-based contrast agents are contraindicated. Methods: Eight GBCAs and three iodinated agents of varying iodine concentrations were radiographed under conditions representative of lumbar spinal injections at four kilovoltage peak (kVp) values. Radiographic contrast of each agent was measured as the percent pixel value difference with respect to background. Results: Gadobutrol (Gadovist, 1 mM/mL) had the highest radiographic contrast among the gadolinium agents tested. Measured radiographic contrast correlated with the molar concentration of gadolinium. Gadobutrol radiographic contrast lies between the contrast of iohexol concentrations of 240 and 140 mgI/mL. All agents have decreasing contrast as kVp increases, but GBCAs decrease less than iodine-based agents. Conclusions: Gadobutrol is the GBCA with the greatest conspicuity for use in spinal injection procedures. It also has the highest molar concentration of gadolinium, and potential neural toxicity from intrathecal delivery must be considered.

Characterizing fluoroscopy based kinematic accuracy as a function of pulse width and velocity.

Fluoroscopic imaging has become increasingly popular to investigate total knee arthroplasty kinematics non-invasively - 3D implant models are aligned with 2D image projections, and optimized via an edge-contour alignment technique. Previous studies have quantified the accuracy of this approach, however they do not always adequately address the impact of image collection parameters. A particularly sensitive parameter is the pulse width, or exposure time per frame. At longer pulse widths, more motion is captured in a single frame; this can lead to image blur and subsequent degradation to image edge quality. Therefore, the comparative accuracy of relative joint kinematics as a function of pulse width and joint velocity needs to be defined. A limits of agreement approach was taken to define the mean differences between optoelectric kinematic measures (gold standard) and fluoroscopic methods at various pulse widths (1, 8 and 16ms) and knee velocities (50, 100 and 225°/s). The mean absolute differences between the optoelectric and fluoroscopic methods for 1ms pulse width were less than 1.5° and 0.9mm. Comparable rotational differences (1.3°) were observed for the 8ms pulse width but had larger translational differences (1.4mm). The 16ms pulse width yielded the greatest mean differences (2.0° and 1.6mm), which increased with knee flexion velocity. The importance of pulse width and velocity should not be overlooked for future studies - this parameter has proven to be a sensitive metric in the quantification of joint motion via fluoroscopy and must be identified and reported in future studies.

Effect of Off-Axis Fluoroscopy Imaging on Two-Dimensional Kinematics in the Lumbar Spine: A Dynamic In Vitro Validation Study.

Spine intersegmental motion parameters and the resultant regional patterns may be useful for biomechanical classification of low back pain (LBP) as well as assessing the appropriate intervention strategy. Because of its availability and reasonable cost, two-dimensional (2D) fluoroscopy has great potential as a diagnostic and evaluative tool. However, the technique of quantifying intervertebral motion in the lumbar spine must be validated, and the sensitivity assessed. The purpose of this investigation was to (1) compare synchronous fluoroscopic and optoelectronic measures of intervertebral rotations during dynamic flexion-extension movements in vitro and (2) assess the effect of C-arm rotation to simulate off-axis patient alignment on intervertebral kinematics measures. Six cadaveric lumbar-sacrum specimens were dissected, and active marker optoelectronic sensors were rigidly attached to the bodies of L2-S1. Fluoroscopic sequences and optoelectronic kinematic data (0.15-mm linear, 0.17-0.20 deg rotational, accuracy) were obtained simultaneously. After images were obtained in a true sagittal plane, the image receptor was rotated in 5 deg increments (posterior oblique angulations) from 5 deg to 15 deg. Quantitative motion analysis (qma) software was used to determine the intersegmental rotations from the fluoroscopic images. The mean absolute rotation differences between optoelectronic values and dynamic fluoroscopic values were less than 0.5 deg for all the motion segments at each off-axis fluoroscopic rotation and were not significantly different (P > 0.05) for any of the off-axis rotations of the fluoroscope. Small misalignments of the lumbar spine relative to the fluoroscope did not introduce measurement variation in relative segmental rotations greater than that observed when the spine and fluoroscope were perpendicular to each other, suggesting that fluoroscopic measures of relative segmental rotation during flexion-extension are likely robust, even when patient alignment is not perfect.

Radiation dose incurred in the exclusion of vascular filling in transforaminal epidural steroid injections: fluoroscopy, digital subtraction angiography, and CT/fluoroscopy.

OBJECTIVE: This study seeks to measure the radiation dose incurred in the evaluation of vascular filling during transforaminal epidural steroid injections (TFESI) using conventional fluoroscopy (CF), digital subtraction angiography (DSA), and multislice, pulsed computed tomography fluoroscopy (CT/F). METHODS: Three portable C-arms and a fixed multipurpose C-arm were evaluated. The radiation dose rate was measured using an anthropomorphic phantom during CF and DSA in anterior-posterior positions for cervical and lumbar TFESIs. Effective doses were calculated for 5-second exposures. The effective doses incurred in the cervical and lumbar spine during two CT/F exposures were calculated based on the reported volume CT dose index and dose length product. RESULTS: DSA imaging increased the effective dose incurred over CF with portable C-arms (medium dose rate) by 2.5-4.3 fold for cervical TFESI and 2.3-4.2 fold for lumbar TFESI. The incremental dose incurred with DSA ranged from 4.0 to 7.7 µSv in the cervical region and from 22-38 µSv in the lumbar spine. CT/F increased the incurred dose 19-fold in the cervical region and 8.0-fold in the lumbar region (incremental doses 49 µSv and 140 µSv, respectively) relative to CF. CONCLUSION: The use of DSA imaging to exclude vascular uptake during TFESI increases radiation dose over CF. CT/F incurs additional dose beyond most DSA. Minimizing radiation dose by limiting DSA and CT/F use to spine segments or clinical situations involving higher risk may be desirable. However, the incremental radiation doses incurred by DSA or CT/F are of such low magnitude that health risks cannot currently be estimated.

Effective use of radiation shields to minimize operator dose during invasive cardiology procedures.

OBJECTIVES: This study sought to measure the protection from scatter radiation offered to the primary physician by a variety of available shields and to provide best practice guidelines for shield use during invasive cardiology procedures. BACKGROUND: It is accepted that exposure to radiation includes a predicted increase in cancer risk. In the cardiac interventional laboratories, radiation shields are widely available; however, proper use of the shields to optimize protection during cardiac interventional procedures is not well understood. METHODS: The protection from scatter radiation offered by a variety of shields used alone and in combination was measured. Protection was assessed from air-kerma measurements of scatter radiation from a phantom performed without and with the shields. Protection was assessed for 3 patient- access locations (right jugular vein, right femoral artery, and left anterior chest) and for elevations ranging from 25 to 175 cm from the floor. The influence of precise placement of the ceiling-mounted upper body shield was specifically assessed. RESULTS: The utility and protection of shielding varied for the 3 access points and with elevation. For femoral artery access locations, the shields can provide at least 80% protection from scatter at all elevations; however, protection depends substantially on upper body shield position. A disposable radiation-absorbing pad can provide 35% to 70% upper body protection for procedures during which the upper body shield cannot be used effectively. CONCLUSIONS: Radiation shields can provide substantial protection from radiation during cardiac interventional procedures. Shields must be thoughtfully and actively managed to provide optimum protection. Best practice guidelines for shield use are provided.

Video fluoroscopic analysis of the effects of three commonly-prescribed off-the-shelf orthoses on vertebral motion.

STUDY DESIGN: Fluoroscopic assessment of the effects of commercially available spinal orthotics on lumbar vertebral motion as subjects performed flexion and extension maneuvers. OBJECTIVE: To quantitate the effects of 3 commonly available, off-the-shelf, soft, and semirigid spinal orthoses on lumbar spinal motion. SUMMARY OF BACKGROUND DATA: Commercially available soft and semirigid orthoses are widely prescribed for patients with low back pain and, at times, following surgery. Despite this use, surprisingly little is known about the magnitude of their effects on lumbar vertebral motion. METHODS: Ten subjects (6 men and 4 women) with an average age of 27.0 +/- 5.3 years, underwent videofluoroscopic imaging as they performed a full flexion/extension cycle. Assessments, during which the subjects were unbraced or wearing either a soft lumbrosacral orthosis (LSO), a semirigid LSO, or a semirigid thoracolumbrosacral orthosis (TLSO) were performed in random order. Images were obtained at a rate of 3.75 Hz and digitally processed to determine the sagittal rotation of the L3-L5 vertebral bodies. RESULTS: Each of the braces produced a statistically significant reduction in overall lumbar motion during the flexion maneuver (P = 0.007) but none had a detectable effect during extension. Relative effectiveness varied by vertebral level. At the L3-L4 level, only the TLSO had a statistically significant effect on intervertebral flexion movement (32%, P = 0.003). At the L4-L5 level all the orthoses were effective (and statistically indistinguishable) in their ability to reduce intervertebral flexion movements ranging from 48% for the semirigid TLSO to about 15% to 20% for the 2 LSOs. No effects were noted for any of the orthoses at the L5-S1 level. CONCLUSION: Commercially available soft and semirigid orthotics can have significant effects on lumbar vertebral body motion at the L3-L4 and L4-L5 levels.