NASA Human Research Program Investigators' Workshop (2012)
4004.pdf
SONOGRAPHIC ASTRONAUT VERTEBRAL EXAMINATION
K. M. Garcia1, D. Peck2, M. Van Holsbeeck2, A. E. Sargsyan1, D. Ebert1, M. Campbell3, D. R. Hamilton1, S. A.
Dulchavsky2
1
Wyle Integrated Science and Engineering, Houston Texas, 2Henry Ford Health Systems, Detroit, MI, 3Wayne State
University, Detroit, Michigan
BACKGROUND
A significant number of astronauts have reported back pain during spaceflight. Severe pain could interfere with the
crew performance and mission objectives. The lengthening of the vertebral column due to disc unloading,
expansion, and loss of spinal curvature has not been fully evaluated in microgravity. The preferred terrestrial means
of spinal evaluation is currently MRI, however ultrasound is the only imaging modality available on ISS. The
investigation team has completed studies exploring the ability of ultrasound to measure inter-vertebral disc space in
healthy volunteers and has established optimal MRI specifications to allow wide viewing properties of cervical and
lumbar vertebral units. The goal of these investigations are to develop a reproducible methodology for the
performance of cervical and lumbar ultrasonography, and to evaluate the accuracy of ultrasound inter-vertebral disc
space measurements. These methods will allow rapid quantification of changes in the vertebral unit during longterm microgravity exposure. This project is funded through NASA Grant NNX10AM34G.
METHODS
An MRI of the cervical spine was obtained on 5 subject volunteers using a 3 Tesla Magnetron (GE Medical,
Milwaukee, WS, USA). Localized cervical spine ultrasound exams were optimized then performed on these
volunteers with a GE Logiq e portable ultrasound machine using a 4 MHz curvilinear probe (GE Medical:
Milwaukee, WS, USA). Ultrasound imaging of the cervical inter-vertebral disc spaces was done with the probe in a
left para-median sagittal position using the carotid artery as an acoustic window. Localization of the cervical intervertebral disc spaces was obtained by visualizing the course of the vertebral artery lateral to the distal carotid at the
bulb bifurcation and directing the ultrasound from an anterior to posterior approach. Accuracy of the ultrasound
measurements were evaluated by comparing the results with the subjects' MRI. Multiple expert musculoskeletal
sonographers performed the ultrasound examinations to assess inter-operator variability. The inter-vertebral disc
spaces were sequentially identified from thoracic 1 (T1) to cervical 5 (C5). Point-to-point caliper measurements
were made between the boney spinal landmarks of each identifiable inter-vertebral space, from the trailing edge of
the top of each vertebra to the leading edge of the next vertebra in the midline. Preliminary quantification of the
vertebral musculature was also done from the MRI examinations. Fusion technology, which couples MRI and
ultrasound examinations, was also investigated to assess this method for medical use in space.
RESULTS
An optimized MRI protocol was developed which allowed an exam of excellent image quality to be completed in
less than 30 minutes. There were no appreciable differences in inter-vertebral disc space measurements with flexionextension of the head. An optimized ultrasound measurement technique was established which correlated the paramedian ultrasound image with the MRI to allow correlative measurements. Ultrasound operators were able to easily
obtain excellent images of the anterior cervical vertebra through vascular windows as bright acoustically dense
objects. The inter-vertebral disc spaces were readily identified for assessment and measurement. Measurements were
reproducible among multiple sonographers with the inter-operator standard deviation averaging 0.03mm.
Volumetric measurements of the vertebral musculature were quantified for the experimental subjects.
CONCLUSIONS
We have developed a reproducible MRI and ultrasound imaging methodology for the evaluation of spinal anatomy.
This technique can be used to assess microgravity associated changes in inter-vertebral disc anatomy, alterations in
the vertebral musculature, and symptomatic cervical spine pathology. We are currently evaluating musculoskeletal
ultrasound in patients with cervical spine pathology and developing just-in-time educational tools to allow nonexpert operators to perform this technique for space medical use during ISS and exploration class spaceflight.