THE VERTEBRAL VENOUS SYSTEM IN HEALTHY AND SCOLIOTIC ADOLESCENT SPINES - A 3D MRI INVESTIGATION.
Caroline A. Grant1, Nicolas Newell1, Maree T. Izatt1, Bethany E. Keenan1, Damon D. Bennett2, Geoffrey N. Askin1, Robert D. Labrom1, Mark J. Pearcy1
PAEDIATRIC SPINE RESEARCH GROUP
1 Paediatric
Spine Research Group, Queensland University of Technology and Mater Health Services Ltd, Queensland, Australia 2 MRI Department, Mater Health Services Ltd, Queensland, Australia
INTRODUCTION
AIS .
The venous drainage system within vertebral bodies (VBs) has been well documented previously in cadaveric specimens(1). Advances in 3D imaging and image processing now allow for in vivo quantification of larger venous vessels, such as the basivertebral vein(2).
CONTROL
RESULTS and DISCUSSION Vascular networks were observed in an average of 6 VBs per subject (range 2-11 AIS, and 4-8 control) most commonly between T9-L2. Vasculature was seen in a clear transverse plane, centrally located within the vertebra, with vessel size in the order of 1.5-2.5mm in diameter.
T9
AIM To examine differences in venous distribution within the VB of Adolescent Idiopathic Scoliosis (AIS) subjects and healthy adolescent controls.
n=11
T10
METHODS Fifteen AIS patients (age 11-16, Cobb angle 17-66°) were recruited along with 15 healthy controls (age 10-13) (with ethics approval) to undergo 3D MRI of the thoraco-lumbar spine using a 3 Tesla, T1-weighted 3D gradient echo sequence (voxel size of 0.5x0.5x0.5mm).
aligned to the plane using the Aaro and then aligned to this most posterior point
In the AIS group in contrast, this pattern is not evident. Replication is seen by some individuals, but others show dramatically different patterns, sometimes not following this basic tree structure at all.
n=15
n=15
T11
Using Amira Filament Editor (Amira v5.6, FEI, Oregon, USA), five transverse slices through each VB were examined simultaneously (Figure 1a) and the resulting observable vascular network traced (Figure 1b). Each VB was assessed, and a vascular network recorded when observable. A local coordinate system was created in each VB of the basivertebral vein, with the axes defined Dahlborn method(3). The vascular network, was coordinate system, with the origin shifted to the (Figure 1b).
n=10
n=15
n=15
Only very slight differences were seen in the right/left distribution of vessels in the control and AIS subjects (Figure 3).
Figure 3 - Percentage distribution of the length of vasculature in the right, centre and left regions of the vertebral bodies, in the control and AIS groups
T12
The length of the vascular network on the left and right sides (with a small central region) of the VB was calculated. A polar coordinate system was then created to examine the spatial patterning of the networks (Figure 1b). Data were grouped by vertebral level across the controls and AIS subjects (Figure 2).
Spatial patterning of the vasculature is shown in Figure 2, for the levels from T9-L2 of the AIS (left column) and control groups (right column). Particular attention should be paid to levels T11-L2. In the control group T11 shows a very clear pattern, with three strong branches, and an additional minor branch. There is a very high level of consistency in this pattern between individuals. Following down the spine, this 4 branch pattern becomes 3 branches at T12, then two broad branches at L1, and finally two narrower, flatter branches at L2.
CONCLUSION n=15
n=14
L1
a
Observation and quantification of the basivertebral vein in vivo is possible using 3D MRI. While right/left distribution differences were small between groups, spatial patterning differences were seen. Strong spatial patterning was seen in the control group, that was not replicated in the AIS subjects, with large differences being evident between individuals.
n=15
n=12
L2
Further investigation into associations between pattern replication and curve progression or severity are therefore warranted. This will be investigated along with the changes in these patterns during growth in a follow up study.
REFERENCES 1. Crock, H. V., & Yoshizawa, H. (1977) The Blood Supply of the Vertebral Column and Spinal Cord in Man., Springer-Verlag, New York 2. Demondion, X. et al. (2000) Surgical and Radiologic Anatomy, 22(3-4), 151–156. 3. Aaro, S., & Dahlborn, M. (1981) Spine, 6(5), 460–467. Figure 1 - (a) Five slices of the MRI stack, viewed simultaneously (b) movie file: (Frame 1) tracing of the visible vasculature in the 5 slice stack and conversion to a set of points, (Frame 2) local coordinate system generation, (Frame 3) captured points converted to a polar coordinate system. The orientation of all images are as per medical imaging, with the right side of the body shown on the left side of the image.
n=5
n=10
Figure 2 - Polar plots of recorded vascular networks in vertebral levels T9 – L2. Each colour represents a unique individual. The AIS group is shown on the left, and the control group on the right. Axes are in degrees from 0-180, with the radial distance in mm.
ACKNOWLEDGEMENTS Professor Graeme Pettit for mathematical advice and support, HPC and Research Support Group at QUT for the software and computational resources.
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