Lumbar Spine Phantom Research Articles

Development of a Head-Mounted Holographic Needle Guidance System for Enhanced Ultrasound-Guided Neuraxial Anesthesia: System Development and Observational Evaluation

BackgroundNeuraxial anesthesia is conventionally performed using a landmark-based technique. Preprocedural ultrasound is often used in challenging clinical scenarios to identify an ideal needle path. The procedure is then carried out by the operator recreating the ultrasound needle path from memory. We suggest that a needle guidance system using the Microsoft HoloLens mixed reality headset, which projects a hologram of the ideal needle path, can assist operators in replicating the correct needle angulation and result in fewer needle passes.ObjectiveThe objective of the study was to develop software for the mixed reality HoloLens headset, which could be used to augment the performance of neuraxial anesthesia, and establish its face validity in lumbar spine phantom models.MethodsWe developed an ultrasound transducer marker and software for the HoloLens, which registers the position and angulation of the ultrasound transducer during preprocedural scans. Once an image of a clear path from skin to the intrathecal space is acquired, a hologram of the ideal needle path is projected onto the user’s visual field. The ultrasound probe is removed while the hologram remains in the correct spatial position to visualize the needle trajectory during the procedure as if conducting real-time ultrasound. User testing was performed using a lumbar spine phantom.ResultsPreliminary work demonstrates that novice (2 anesthesia residents) and experienced operators (5 attending anesthesiologists) can rapidly learn to use mixed reality holograms to perform neuraxial anesthesia on lumbar spine phantoms.ConclusionsOur study shows promising results for performing neuraxial anesthesia in phantoms using the HoloLens. Although this may have wide-ranging implications for image-guided therapies, further study is required to quantify the accuracy and safety benefit of using holographic guidance.Trial RegistrationClinicalTrials.gov NCT04028284; https://clinicaltrials.gov/ct2/show/NCT04028284

Autonomous Spinal Robotic System for Transforaminal Lumbar Epidural Injections: A Proof of Concept of Study.

Phantom study. The aim of our study is to demonstrate in a proof-of-concept model whether the use of a marker less autonomous robotic controlled injection delivery system will increase accuracy in the lumbar spine. Ideal transforaminal epidural injection trajectories (bilateral L2/3, L3/4, L4/5, L5/S1 and S1) were planned out on a virtual pre-operative planning software by 1 experienced provider. Twenty transforaminal epidural injections were administered in a lumbar spine phantom model, 10 using a freehand procedure, and 10 using a marker less autonomous spinal robotic system. Procedural accuracy, defined as the difference between pre-operative planning and actual post-operative needle tip distance (mm) and angular orientation (degrees), were assessed between the freehand and robotic procedures. Procedural accuracy for robotically placed transforaminal epidural injections was significantly higher with the difference in pre- and post-operative needle tip distance being 20.1 (±5.0) mm in the freehand procedure and 11.4 (±3.9) mm in the robotically placed procedure (P < .001). Needle tip precision for the freehand technique was 15.6mm (26.3 - 10.7) compared to 10.1mm (16.3 - 6.1) for the robotic technique. Differences in needle angular orientation deviation were 5.6 (±3.3) degrees in the robotically placed procedure and 12.0 (±4.8) degrees in the freehand procedure (P = .003). The robotic system allowed for comparable placement of transforaminal epidural injections as a freehand technique by an experienced provider, with additional benefits of improved accuracy and precision.

Fused filament fabrication of complex anatomical phantoms with infill-tunable image contrast

Fused filament fabrication (FFF) provides a rapid means of producing anatomical models for biomedical education and training. However, FFF-compatible materials and methods are currently limited for efficient and accurate production of complex phantoms that can mimic the radiological properties of multiple human tissues. It is demonstrated in this research that the computed tomography (CT) contrast can be modified by varying the concentration of bismuth oxide in acrylonitrile butadiene styrene (ABS) filaments and by modifying the infill percentage of the printed models. By using an infill geometry consisting of an encapsulated pore structure, the CT contrast of fat, blood, kidney, liver, trabecular bone, and cortical bone could be successfully displayed without the presence of any artificial artefacts in the images. In addition, a lumbar spine phantom is printed with the infill varied throughout the model to accurately mimic the CT contrast for the trabecular and cortical bone volumes. This research is of particular relevance for FFF-printing of anatomical models for radiology education and image-guided surgical training.

Creation of a three-dimensional printed spine model for training in pain procedures

ObjectiveTechnological developments have made it possible to create simulation models to educate clinicians on surgical techniques and patient preparation. In this study, we created an inexpensive lumbar spine phantom using patient data and analyzed its usefulness in clinical education.MethodsThis randomized comparative study used computed tomography and magnetic resonance imaging data from a single patient to print a three-dimensional (3D) bone framework and create a mold. The printed bones and structures made from the mold were placed in a simulation model that was used to train residents. The residents were divided into two groups: Group L, which received only an audiovisual lecture, and Group P, which received an additional 1 hour of training using the 3D phantom. The performance of both groups was evaluated using pretest and post-test analyses.ResultsBoth the checklist and global rating scores increased after training in both groups. However, some variables improved significantly only in Group P. The overall satisfaction score was also higher in Group P than in Group L.ConclusionsWe have described a method by which medical doctors can create a spine simulation phantom and have demonstrated its efficiency for procedural education.

Validation of a low-cost adjustable, handheld needle guide for spine interventions

&#x0D; Purpose: MR-guided injections are safer for the patient and the physician than CT-guided interventions but require a significant amount of hand-eye coordination and mental registration by the physician. We propose a low-cost, adjustable, handheld guide to assist the operator in aligning the needle in the correct orientation for the injection.&#x0D; Methods: The operator adjusts the guide to the desired insertion angle as determined by an MRI image. Next, the operator aligns the guide in the image plane using the horizontal laser and level gradient. The needle is inserted into the sleeve of the guide and inserted into the patient. To evaluate the method, two operators inserted 5 needles in two facet joints of a lumbar spine phantom. Insertion points, final points and trajectory angles were compared to the projected needle trajectory using an electromagnetic tracking system.&#x0D; Results: On their first attempt, operators were able to insert the needle into the facet joint 85% of the time. On average, operators had an insertion point error of 2.92 ± 1.57 mm, a target point error of 3.39 ± 2.28 mm, and a trajectory error of 3.98 ± 2.09 degrees.&#x0D; Conclusion: A low-cost, adjustable, handheld guide was developed to assist in correctly positioning a needle in MR-guided needle interventions. The guide is as accurate as other needle placement assistance mechanisms, including the biplane laser guides and image overlay devices when used in lumbar facet joint injections in phantoms.

Image guided percutaneous spine procedures using an optical see-through head mounted display: proof of concept and rationale

Background and purposeOptical see-through head mounted displays (OST-HMDs) offer a mixed reality (MixR) experience with unhindered procedural site visualization during procedures using high resolution radiographic imaging. This technical note describes...

Simulation-Based Educational Curriculum for Fluoroscopically Guided Lumbar Puncture Improves Operator Confidence and Reduces Patient Dose

Fluoroscopically guided lumbar puncture (FGLP) is a commonly performed procedure with increased success rates relative to bedside technique. However, FGLP also exposes both patient and staff to ionizing radiation. The purpose of this study was to determine if the use of a simulation-based FGLP training program using an original, inexpensive lumbar spine phantom could improve operator confidence and efficiency, while also reducing patient dose. A didactic and simulation-based FGLP curriculum was designed, including a 1-hour lecture and hands-on training with a lumbar spine phantom prototype developed at our institution. Six incoming post-graduate year 2 (PGY-2) radiology residents completed a short survey before taking the course, and each resident practiced 20 simulated FGLPs using the phantom before their first clinical procedure. Data from the 114 lumbar punctures (LPs) performed by the six trained residents (prospective cohort) were compared to data from 514 LPs performed by 17 residents who did not receive simulation-based training (retrospective cohort). Fluoroscopy time (FT), FGLP success rate, and indication were compared. There was a statistically significant reduction in average FT for the 114 procedures performed by the prospective study cohort compared to the 514 procedures performed by the retrospective cohort. This held true for all procedures in aggregate, LPs for myelography, and all procedures performed for a diagnostic indication. Aggregate FT for the prospective group (0.87 ± 0.68 minutes) was significantly lower compared to the retrospective group (1.09 ± 0.65 minutes) and resulted in a 25% reduction in average FT (P = .002). There was no statistically significant difference in the number of failed FGLPs between the two groups. Our simulation-based FGLP curriculum resulted in improved operator confidence and reduced FT. These changes suggest that resident procedure efficiency was improved, whereas patient dose was reduced. The FGLP training program was implemented by radiology residents and required a minimal investment of time and resources. The LP spine phantom used during training was inexpensive, durable, and effective. In addition, the phantom is compatible with multiple modalities including fluoroscopy, computed tomography, and ultrasound and could be easily adapted to other applications such as facet injections or joint arthrograms.

A robust and inexpensive phantom for fluoroscopically guided lumbar puncture training.

This report describes the creation process for an inexpensive, durable, lumbar spine phantom for use in fluoroscopically guided lumbar puncture (LP) training. The LP phantom prototype was made from a polyvinyl chloride lumbar spine model embedded in a translucent rectangular block of commercially available thermoplastic polymer gel. Radiology residents with limited previous experience performing LP used the phantom for 20 simulated procedures to gain confidence before starting patient procedures. The residents completed surveys detailing their experiences with the phantom. Quantitative evaluation of the phantom using fluoroscopy and computed tomography suggested good physical agreement with human anatomy. Six board-certified radiologists viewed the phantom under live fluoroscopy and indicated that the phantom represented human anatomy with sufficient accuracy. Furthermore, surveys from resident trainees indicated that the thermoplastic tissue substitute simulated the texture and resistance of human soft tissue reasonably well for the purposes of clinical training. The total material cost of the LP phantom prototype was approximately US $148.00. This novel spine phantom can be produced with relatively low cost when compared with similar commercially available products. The phantom offers reasonable visual and tactile agreement to human anatomy and may be useful for improving the confidence of physician trainees. The LP phantom is durable and can easily be repaired by reheating the polymer tissue substitute.

Low-dose computed tomography of the lumbar spine: a phantom study on imaging parameters and image quality

Lumbar spine radiography has limited diagnostic value but low radiation dose compared with computed tomography (CT). The average effective radiation dose from lumbar spine radiography is about 1.1 mSv. Low-dose lumbar spine CT may be an alternative to increase the diagnostic value at low radiation dose, around 1 mSv. To determine the optimal settings for low-dose lumbar spine CT simultaneously aiming for the highest diagnostic image quality possible. An ovine lower thoracic and lumbar spine phantom, with all soft tissues around the vertebrae preserved except the skin, was placed in a 20 L plastic container filled with water. The phantom was scanned repeatedly with various technical settings; different tube potential, reference mAs, and with different convolution filters. Five radiologists evaluated the image quality according to a modification of the European guidelines for multislice computed tomography (MSCT) quality criteria for lumbar spine CT 2004. In a visual comparison the different scans were also ranked subjectively according to perceived image quality. Image noise and contrast were measured. A tube potential of 120 kV with reference mAs 30 and medium or medium smooth convolution filter gave the best image quality at a sub-millisievert dose level, i.e. with an effective dose comparable to that from lumbar spine radiography. Low-dose lumbar spine CT thus opens a possibility to substitute lumbar spine radiography with CT without obvious increase in radiation dose.

A study on the effects of a calcium drug on the bone mineral density (BMD) by using dual-energy X-ray Absorptiometry (DXA)

Measurements of osteoporosis might contain errors caused by the calcium drug used in the prevention and the treatment of osteoporosis. This study conducted a lumbar spine phantom experiment to examine whether a calcium drug can influence the measured values of the bone mineral density (BMD) because of the drug taken by a real patient remaining undigested in the stomach. Dual-energy X-ray Absorptiometry (DXA) was used to measure the BMD for a calcium-drug in an equipment-dedicated lumbar spine phantom and 10 patients selected for the BMD measurement. Three types of drugs that are prescribed in actual clinical practice calcium drugs were used for the phantom experiment, and the drugs were divided into a fixed dose, 1/2 of the fixed dose, 1/4 of the fixed dose and 1/8 of the fixed dose. Without the drugs included, the phantom was scanned 60 times continuously to calculate the baseline BMD. The BMD was measured as the calcium drug coated with paraffin was placed in the lumbar vertebra 2 and the soft tissue region of the phantom. To determine when the drug was invisible to the naked eye are measured, the BMD at different drug dilutions. The measurements were conducted three times to calculate the mean. In the patient experiment, patients were selected who visited hospital after taking the drug before measuring the BMD. After a certain time had passed, the BMD was measured again to examine the difference in images and the change in BMD values due to the calcium-drug intake. The BMD measurements of lumbar 1–4 in the phantom were higher, with statistical significant, than the least significant change (LSC) in the bone region for all three drugs (Ca carbonate, Ca citrate and Ca cholecalciferol), showing a significant increase. On the other hand, there was no significant change in the soft tissue. When Ca Cholecalciferol was used in a fixed dose, the BMD of L2 increased by 11.6%, showing the largest increase among the drugs examined, but only a 2.8% increase in the BMD of L1–L4 was observed. The dependence of the results on the degree of dilution of the calcium drug showed that the three drugs had values that exceeded the LSC significantly. The measured the BMD was higher in 7 out of 10 patients when the patients took the calcium drug than when they did not. In addition, one of the patients showed a 3.6% increase in BMD. In addition, the calcium drug appeared in the image in two of the patients who showed an increase in the BMD. This confirmed that the drug remained undigested, with a certain amount of it remaining in the body system. Overall, the measured BMD is affected when the calcium drug taken by a real patient remains undigested in the stomach.

Augmented Reality Visualization With Image Overlay for MRI-Guided Intervention: Accuracy for Lumbar Spinal Procedures With a 1.5-T MRI System

The purpose of this study was to prospectively evaluate the accuracy of an augmented reality image overlay system in MRI-guided spinal injection procedures. An augmented reality prototype was used in conjunction with a 1.5-T MRI system. A human lumbar spine phantom was used in which 62 targets were punctured to assess the accuracy of the system. Sixty anatomic targets (facet joint, disk space, and spinal canal) were punctured to assess how the accuracy of the system translated into practice. A visualization software interface was used to compare planned needle paths and final needle locations on coregistered CT images (standard of reference). Outcome variables included entry error, angle error, depth error, target error, successful access of anatomic targets, number of needle adjustments, and time requirements. Accuracy assessments showed entry error of 1.6 ± 0.8 mm, angle error of 1.6° ± 1.0°, depth error of 0.7 ± 0.5 mm, and target error of 1.9 ± 0.9 mm. All anatomic targets (60 of 60 insertions) were successfully punctured, including all 20 facet joints, all 20 disks, and all 20 spinal canals. Four needle adjustments (6.7%) were required. Planning of a single needle path required an average of 55 seconds. A single needle insertion required an average of 1 minute 27 seconds. The augmented reality image overlay system evaluated facilitated accurate MRI guidance for successful spinal procedures in a lumbar spine model. It exhibited potential for simplifying the current practice of MRI-guided lumbar spinal injection procedures.

PenMesh—Monte Carlo Radiation Transport Simulation in a Triangle Mesh Geometry

We have developed a general-purpose Monte Carlo simulation code, called penMesh, that combines the accuracy of the radiation transport physics subroutines from PENELOPE and the flexibility of a geometry based on triangle meshes. While the geometric models implemented in most general-purpose codes--such as PENELOPE's quadric geometry--impose some limitations in the shape of the objects that can be simulated, triangle meshes can be used to describe any free-form (arbitrary) object. Triangle meshes are extensively used in computer-aided design and computer graphics. We took advantage of the sophisticated tools already developed in these fields, such as an octree structure and an efficient ray-triangle intersection algorithm, to significantly accelerate the triangle mesh ray-tracing. A detailed description of the new simulation code and its ray-tracing algorithm is provided in this paper. Furthermore, we show how it can be readily used in medical imaging applications thanks to the detailed anatomical phantoms already available. In particular, we present a whole body radiography simulation using a triangulated version of the anthropomorphic NCAT phantom. An example simulation of scatter fraction measurements using a standardized abdomen and lumbar spine phantom, and a benchmark of the triangle mesh and quadric geometries in the ray-tracing of a mathematical breast model, are also presented to show some of the capabilities of penMesh.

Bone Densitometry Within Titanium Lumbar Interbody Fusion Cages

The use of lumbar fusion cages to augment interbody arthrodesis has become popular. Previous studies have shown that titanium cages may obscure information within and around the cage, confounding assessments of fusion. Densitometry within cages, if possible, could be an important outcome variable for comparing different cage augmented fusion treatments. The purpose of this feasibility study was to (1) validate CT-based (computer tomography-based) density evaluations within titanium cages in a phantom model, and (2) demonstrate that intrametal cage lucencies can be produced by CT reconstruction artifacts and do not necessarily represent bone fragmentation or fibrous and cartilaginous tissue. An anthropomorphic lumbar spine phantom was used. Dual titanium cages were inserted into 6 anterior-middle column replicas, and the cages were filled with 10, 100, or 400 mg/cc hydoxyapatiite equivalent material. The column replicas were composed of either fibrous/cartilaginous tissue equivalent material or trabecular bone equivalent material. Column replicas were placed within the phantom and imaged with CT. Direct axial and reformatted sagittal and coronal images were evaluated for artifact. Region of interest analysis was performed for intracage density. Intracage CT values calculated from axial, sagittal, and coronal images were directly related to the true CT values of the materials (r = 0.99, P < 0.0001). CT was used to distinguish between fibrous tissue and bone within cages. CT values within cages overestimated the intracage materials' true values (paired t test, P < 0.001). Intracage CT values were correctable and could be converted to bone mineral content. Intracage CT values were not affected by adjacent anterior-middle column material differences (fibrous/cartilaginous tissue vs. trabecular bone) (paired t test, P > 0.05). Lucent streaking within and adjacent to cages was similar to clinical images. In this phantom-based study, densitometry was performed within titanium cages, even in the presence of CT artifact. These results support further pursuit of this potential assessment tool.

10 Axial Rotation Significantly Affects DXA Lumbar Spine Phantom BMD Measurements

10 Axial Rotation Significantly Affects DXA Lumbar Spine Phantom BMD Measurements

Effect of x-ray tube potential on image quality and patient dose for lumbar spine computed radiography examinations

A study was conducted to investigate the effect of increasing x-ray tube voltage on patient dose and image quality during computed radiography (CR) examination of the lumbar spine. Images of a pelvis - lumbar spine phantom were obtained at three different tube voltages using two CR systems. The images were evaluated by image scores (IS) using the image quality criteria proposed by the Commission of the European Communities (CEC), by measuring the signal-to-noise ratio and the contrast-to-noise ratio. The entrance surface dose (ESD) to the phantom was also measured using ionisation chambers and the resulting gonad dose (G) and effective dose (E) were calculated. The CEC recommended tube voltages can be exceeded with CR systems for lumbar spine radiography. The ESD, G and E decreased by 25%-50% with both CR systems when tube voltage was increased. Although the decrease in IS was statistically significant (P < 0.05) the images obtained with the 3 tube voltages were diagnostically acceptable. The balance between image quality and patient dose can be optimised by using higher x-ray tube voltages for lumbar spine CR examinations.

“Gold standard” data for evaluation and comparison of 3D/2D registration methods

Evaluation and comparison of registration techniques for image-guided surgery is an important problem that has received little attention in the literature. In this paper we address the challenging problem of generating reliable “gold standard” data for use in evaluating the accuracy of 3D/2D registrations. We have devised a cadaveric lumbar spine phantom with fiducial markers and established highly accurate correspondences between 3D CT and MR images and 18 2D X-ray images. The expected target registration errors for target points on the pedicles are less than 0.26 mm for CT-to-X-ray registration and less than 0.42 mm for MR-to-X-ray registration. As such, the “gold standard” data, which has been made publicly available on the Internet (http://lit.fe.uni-lj.si/Downloads/downloads.asp), is useful for evaluation and comparison of 3D/2D image registration methods.

Quantitative MR imaging of lumbar intervertebral discs and vertebral bodies: Methodology, reproducibility, and preliminary results

Since relaxation times are influenced by the hydration of the tissue and the chemical environment of the water molecules, T 1 and T 2 measurements (quantitative MRI) could be used as an indicator for the water content and the biochemical composition of lumbar intervertebral discs. The discriminating power of quantitative MRI for tissue characterization in individuals (for clinical diagnosis) and in cohorts (e.g. for investigations on disc physiology or composition) relies on the reproducibility in relation to the expected tissue differences. We therefore investigated the reproducibility in vitro (lumbar spine phantom) and in vivo (10 volunteers). To estimate the differences between normal and pathologic tissues in vivo, 100 normal and 20 herniated intervertebral discs were examined by quantitative MRI in a first application of our method. The relaxation times were calculated from a set of 20 images obtained with five singe-slice/multi-echo sequences at different TR values on a commercial whole-body system (1.5 T). We have found a satisfactory reproducibility in vitro ( T 1: 1.9%; T 2: 6.2%), while the reproductibility was less satisfactory in vivo ( T 1: 16.4%; T 2: 13.4%). Calculated from theses values, differences in relaxation times of various tissues must exceed 486 ms for T 1 and 24 ms for T 2 (tolerance limits) to allow discrimination with a 95% confidence in individuals. We observed statistically significant ( p = 0.001) mean differences between normal ( n = 100) and herniated ( n = 20) intervertebral discs (ΔT 1: 196 ms; ΔT 2: 15 ms). Although statistical significant in cohorts, a discrimination of normal and herniated intervertebral discs is limited by quantitative MRI in individuals, since the differences are smaller than the tolerance limits necessary for a reliable clinical diagnosis. However, our results indicate that variations in the disc hydration and/or composition can be noninvasively detected by quantitative MRI in studies of cohorts with sufficient accuracy.

In vitro comparability of dual energy X-ray absorptiometry (DEXA) bone densitometers

Six Hologic QDR-1000 DEXA bone densitometers at different centers across the USA were compared to determine the intermachine variability. Nine scans in succession were acquired on each machine using a single anthropomorphic lumbar spine phantom (manufactured by Hologic). Values for BMC, area, and BMD were recorded for each measurement. Means, standard deviations (SD), and coefficients of variation (CV) were calculated for each machine. All the CVs (BMC, area, BMD) were less than 1% (range 0.3%-0.6%). The CV of the means at the six sites were 0.4%, 0.6%, and 0.5% for BMC, area, and BMD, respectively. Although several significant differences for BMC, area, and BMD were noted by ANOVA between machines at different sites, the difference between the highest and lowest means of the individual machines was only 1.1%, 1.31%, and 1.07% for BMC, area, and BMD. The small variations between the DEXA systems are encouraging for researchers involved in multicenter trials in which data are pooled.