1. The Impact of Airway Management Strategies on
MR Image Quality in Pediatric and Adult Patients
eP-190
David Z. Ferson, M.D.1, F. Eymen Ucisik-Keser M.D. 1,2, Yussra Hamid1, Linda Chi, M.D2.
1 The University of Texas MD Anderson Cancer Center Department of Anesthesiology and Perioperative Medicine, Houston, Texas, USA
2 The University of Texas MD Anderson Cancer Center Department of Diagnostic Radiology, Houston, Texas, USA

2. No conflicts of interest to disclose

3. Introduction
Magnetic resonance imaging (MRI) is instrumental for the evaluation of central nervous system (CNS) pathology.
A major drawback of MRI is long acquisition time, during which the patient must lay still within the small bore of the magnet. Almost all pediatric patients and many adult patients undergoing MRI studies are unable to cooperate and require sedation or general anesthesia.

4. Introduction
Propofol is the preferred agent for deep sedation and general anesthesia in the MRI setting due to its short half-life. However, it frequently leads to pharyngeal muscle relaxation, transient airway obstruction, resulting in snoring and subsequent head micromotion.
Any motion, including micromotion of the head causes unwanted artifacts, thus lowering the diagnostic value of CNS MRI studies.
To mitigate airway obstruction due to pharyngeal muscle relaxation, various airway devices are available.

5. Purpose
The purpose of our study was to determine the effectiveness of different airway management techniques in overcoming micromotion-induced MRI artifacts.
We retrospectively evaluated the image quality of serial CNS MRI studies in 9 patients for whom different airway management techniques were used.

6. Materials and Methods Study period: September 2007 - August 2015
After obtaining IRB approval, we conducted a retrospective review of the CNS MRI studies of patients at our institution who met all of the following inclusion criteria:
(1) Undergone sedation or GA
(2) At least 5 serial MRI studies
(3) At least one MRI session with an airway device and one session without an airway device
(4) Only one type of airway device per session

7. Materials and Methods – MRI Quality Scoring System
To determine the image quality of each MRI sequence, we developed a 5-point scoring system with the following scores: 1 - Very poor quality, nondiagnostic 2 - Poor quality, minimal diagnostic value 3 - Acceptable quality 4 - Good quality diagnostic 5 - Excellent quality 1
Very poor quality 2
Poor quality 3
Acceptable quality 4
Good quality 5
Excellent quality

8. Materials and Methods – MRI Quality Scoring System
6 standard MRI sequences were analyzed:
Axial T2
Axial fluid-attenuated inversion recovery (FLAIR)
Axial T1 precontrast
Axial T1 postcontrast
Coronal T1 postcontrast
Sagittal T1 postcontrast

9. Materials and Methods – MRI Quality Scoring System
A combined score ranging from 6 to 30 was assigned to each MRI session.

10. Materials and Methods – Airway Management Techniques
Information regarding patient characteristics and the airway management technique used to maintain a patent airway were collected from the electronic medical records.
The airway management techniques used in the study participants were
No airway device (NAD)
Oral airway
Nasal airway
Supraglottic airway (SGA)
Tracheal tube

11. Materials and Methods – Statistical Analysis
Linear mixed model was used to test if there was significant difference in image quality between different airway management techniques. All tests were two-sided and p-values of 0.05 or less were considered statistically significant. Statistical analysis was carried out using SAS version 9 (SAS Institute, Cary, NC).
If a statistical analysis using linear mixed model could not be performed due to small sample size, and thereby an estimated mean score could not be calculated, simple arithmetic mean was used for comparison.

12. Results 85 MRI studies in 4 pediatric and 5 adult patients
4 females and 5 males, with ages 10 months - 72 years
Each line graph above represents a study patient. The combined scores for each MRI session (ranging from 10 to 30) is demarcated on the horizontal axis. Each MRI session for a given patient is depicted by a symbol which identifies the particular airway management technique used.

13. Results Airway Management Technique No. of Studies
Combined Score (Arithmetical mean)
Combined Score (Estimated mean ± SE)
NAD 48
21.6
22.0 ± 0.97
Supraglottic 27
27.6
27.3 ± 1.04
Oral 4
20.3
N/A
Nasal
15.3
Tracheal 2
29.5
P<
Arithmetical means and estimated means of combined scores for each airway management technique. The numbers of nasal, oral and tracheal airway devices were small, thus they didn’t reach the power to perform a statistical analysis. For this reason, estimated means are not available for these groups. SE: Standard error. N/A: Not available

14. Results
We performed statistical analysis on the two largest cohorts: NAD and SGA studies.
The estimated mean combined scores:
22.0 (range: 11-30) for NAD
27.3 (range: 23-30) for the SGAs.
Combined score improved by 5.3 (p-value <0.0001)

15. Results No airway device Combined score of 12 out of 30
Supraglottic airway (arrow) Combined score of 27 out of 30
Serial MRI studies from the patient 7.

16. Results
Figure shows distribution of the combined scores for NAD and SGA groups.
Note the trend for higher scores, better MRI quality, with the use of SGAs.

17. Conclusion
Anesthesia-related airway obstruction causes micromotion of the head, which can greatly affect the diagnostic value of MRI studies.
Different airway management strategies vary in their influence on the quality of MRI images.
The use of SGAs improves the image quality significantly and consistently.

18. Conclusion
The studies using nasal, oral or tracheal airway devices were few in number, thus statistical analysis could not be performed.
However, we observed several trends:
Oral and nasal airways did not improve the image quality compared to NAD.
Image quality was equivalent with the use of the tracheal tube and SGA, which suggests that the less invasive SGA may be preferred in the MRI environment in patients at low risk for aspiration.

19. Conclusion
To determine which airway devices and anesthetic practices are optimal for patients undergoing MRI studies, there is a need for future randomized controlled trials comparing different types of SGA devices.

20. Acknowledgements
We thank Yiwen Yang, M.S., and Wei (Auston) Wei, M.S., for the statistical analysis; Richard F. Carlson, M.D., and Zafer Keser, M.D., for serving as scientific advisors and reviewing the manuscript; and Dawn Chalaire for scientific editing.

21. Author contacts: David Z. Ferson: dferson@mdanderson.org
T. Linda Chi: