Image Fusion of Ultrasound and Magnetic Resonance Imaging for Regional Anesthesia of the Hip: The Influence of MRI Scanning Position for Fusion Accuracy and Post Anesthesia Visualization of Anatomical Distribution of Local Anesthetics
Jennie Maria Christin Strid1, Erik Morre Pedersen2, Olga Vendelbo2, Niels Dalsgaard1, Yousef Nejatbakhsh3, Jens Randel Nyengaard4, Kjeld Søballe5, and Thomas Fichtner Bendtsen1

1Department of Anesthesiology, Aarhus University Hospital, Aarhus C, Denmark, 2Department of Radiology, Aarhus University Hospital, Aarhus C, Denmark, 3Hospital Pharmacy, Aarhus University Hospital, Aarhus C, Denmark, 4Electron Microscopy Lab and Stereology, Institute of Clinical Medicine, Aarhus University, Aarhus C, Denmark, 5Department of Orthopedic Surgery, Aarhus University Hospital, Aarhus C, Denmark

Synopsis

Ultrasound guided lumbar plexus blocks holds the potential for reducing anesthesia related complications in hip surgery in the elderly punctum. The ultrasound guidance is, however, imprecise and associated with epidural spread of local anesthetic due to limited visualization. It is the overall aim of this study to improve the quality of lumbar plexus blocks using Fusion imaging between MRI and ultrasound. Here we report preliminary results of the impact of different MR scanning positions for the accuracy of fusion imaging and report on the feasibility of using gadolinium doped anesthetics for studying the distribution of local anesthetic fluid using MRI.

Purpose

To study primarily the influence of MRI scanning position on ultrasound and MRI fusion imaging accuracy prospectively in elderly volunteers. Secondly to explore the feasibility of using gadolinium doped anesthetics for studying the distribution of local anesthetic injectate following block of the lumbosacral plexus.

Methods

MR imaging in different positions
Under the hypothesis that the lumbosacral plexus remains in the same position during change from the supine position normally used during MRI to the lateral decubitus position normally used for ultrasound guided lumbosacral plexus blocks, we scanned 25 elderly healthy volunteers in the supine and in a lateral decubitus position with a 70 cm bore 1.5T Philips Ingenia scanner. The dS flex coverage posterior coil and a flex coverage anterior coil with 16 elements was used for signal reception. A 3D T2-TSE sequence (VISTA) with an isotropic scanned resolution of 1.2 x 1.2 x 1.2 mm3 (overcontiguos 2.4 mm slices with 1.2 mm spacing), TE 60 ms and TR 1200 ms was used. Coronal images of the spine and its surrounding structures from L1 to S4 using feet-head phase encoding for minimizing artefacts due to respiration and peristaltic (Fig. 1) were obtained with a scan time of 6:26 min.

MR imaging of local anesthetics
Physical compatibility between the gadolinium contrast agent Dotarem® (27.9% gadoterate meglumine) and the local anesthetics 2% lidocaine with 0.0005% epinephrine, 0.75% ropivacaine hydrochloride, and 0.5% bupivacaine hydrochloride was investigated because no documented compatibility of the combination could be found despite previously use.1 After examination for visible color change and particle formation, subvisible particle formation, and pH change, we confirmed that Dotarem® is physical compatible with all three local anesthetics, 2,3 and established a MR imaging protocol for visualizing the spread of local anesthetics.

Image analysis
The images obtained in the supine and in the lateral decubitus positions were rigidly registered (OsiriX, Pixmeo, Switzerland) using the lateral part of the transverse process of L4 and L5, respectively, as reference because this is a key reference point in the ultrasound guided procedure. The distances between the targets of the local anesthetic, spinal nerves L3 and L4, in both positions were measured (Fig. 2). The mean (±SD) or the median (IQR) distance between the spinal nerves in the two positions was calculated depending on the normality of data.

T1 weighted 3D gradient echo breathheld mDixon water scans, visualizing the gadolinium doped injectate (Fig. 3), were combined with DWI based visualization (B-values: 0 and 500 s/mm2) of the target nerves. To discriminate between the injectate and the nerves, ADC maps were used. The spread of the injectate could hereafter be compared to sensory blockade after the injection.4 This approach was used in 26 healthy volunteers in a recent prospective randomized controlled crossover trial aiming to compare the effectiveness of the lumbosacral plexus block guided by ultrasound vs. guidance with MRI/ultrasound fused images.

Results

Table 1 (Fig. 5) displays the distances in mm between the spinal nerves in the supine and in the lateral decubitus position recorded on MRI. The initial results of the randomized controlled trial, comparing ultrasound guidance of lumbosacral plexus block with MRI/ultrasound fused images guidance, demonstrated that it was possible to obtain adequate MRI image quality to identify the nervous structures and to perform meaningful MRI/ultrasound fusion guided blocks of the lumbosacral plexus in all volunteers.

Discussion

Only slight displacement were seen of the L3 and L4 spinal nerves in different MRI scanning positions – most likely because the lumbosacral plexus is situated in the posterior part of the major psoas muscle, juxtapositioned to the rigid lumbar vertebral column. Considering fused images can be adjusted in all three planes, we consider these minor displacements to be clinically acceptable. In perspective, elderly patients with a damaged hip can be MRI scanned in a realistic supine position and have a MRI/ultrasound fused images guided lumbosacral plexus block at the L4-L5 level in the lateral decubitus position with a reduced risk of possible detrimental cardiovascular and respiratory side effects. A randomized controlled trial will further explore the possible benefits in effectiveness and safety of lumbosacral plexus blocks guided by MRI/ultrasound fused images.

Conclusion

MRI to be used for MRI/ultrasound fusion based regional anesthesia of the lumbosacral plexus can be performed in a realistic supine position for fusion with ultrasound used in the lateral decubitus position. Detailed analysis of a recently performed prospective randomized controlled crossover study will reveal if MRI/ultrasound imaging guidance are superior to ultrasound imaging guidance for securing effective regional anesthesia of the lumbosacral plexus.

Acknowledgements

Thank you to the colleagues in the research group at Department of Anesthesiology at Aarhus University Hospital, Aarhus C, Denmark.

References

1. Almeida DR, Belliveau MJ, Enright T, Islam O, El-Defrawy SR, Gale J. Anatomic distribution of gadolinium contrast medium by high-resolution magnetic resonance imaging after peribulbar and retrobulbar injections. Arch Ophthalmol 2012;130(6):743-8.

2. European Directorate for the Quality of Medicines & HealthCare. European Pharmacopoeia 8.0. Strasbourg, France: Council of Europe; 2013.

3. Danish Health and Medicines Authority. Summary of product characteristics for lidocaine-adrenaline SAD, injection, solution. Copenhagen, Denmark: Danish Health and Medicines Authority; 2015.

4. Bendtsen TF, Pedersen EM, Haroutounian S, Soballe K, Moriggl B, Nikolajsen L, Hasselstrom JB, Fisker AK, Strid JM, Iversen B, Borglum J. The suprasacral parallel shift vs lumbar plexus blockade with ultrasound guidance in healthy volunteers - a randomised controlled trial. Anaesthesia 2014 Nov;69(11):1227-40.

Figures

An axial image of a 3D T2-TSE sequence (VISTA) obtained in the lateral decubitus position for analysis of displacement of the lumbosacral plexus due to change from the supine to the lateral decubitus position.

Record of the coordinates of a target point in the lumbosacral plexus (spinal nerve L3) in the supine and in the lateral decubitus position using the DICOM viewer OsiriX. An observer blinded for the scanning position made all the recordings.

An axial image from one of the mDIXON T1 gradient echo out-of-phase sequences used for visualizing the spread of local anesthetics added Dotarem (red arrow).

Example of image fusion of MRI and ultrasound of the lumbar region.

Tabel 1. Distance between the target nerves in the supine position to the target nerves in the lateral decubitus position.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
4460