Scientific Session 18 — Neuroradiology - Head and NeckThursday, May 4, 2017
3210. Anatomic Demonstration of Retropharyngeal Space in Ultrashort TE MRI of the Cervical Spine
Siriwanarangsun P1,2*, Ariyachaipanich A1,3, Statum S1,4, Bae W1, Chung C1,4 1. University of California San Diego, La Jolla, CA; 2. Siriraj Hospital Mahidol University, Bangkok, Thailand; 3. King Chulalongkorn Memorial Hospital Chulalongkorn University, Bangkok, Thailand; 4. VA San Diego Health System, San Diego, CA
Address correspondence to P. Siriwanarangsun (firstname.lastname@example.org)
Objective: Retropharyngeal space is a potential space posterior to the pharynx that is implicated in deep neck infection and neoplastic spreading. These conditions can lead to life-threatening complication because of rapid progression. The diagnosis is based on both clinical and imaging diagnosis, but the anatomy is not readily seen using conventional MRI such as T2-weighted spin-echo sequences. The purpose of the study was to determine if anatomic boundaries of the retropharyngeal space including the visceral fascia, alar fascia, and prevertebral fascia can be identified as trilaminar appearance on ultrashort TE and conventional T2-weighted spin-echo MRI.
Materials and Methods: Nine cervical spines were examined at 3 T (MR750, GE Healthcare) with sagittal ultrashort TE (TR/TE, 10/0.05) and T2-weighted spin-echo (TR/TE, 3500/100) sequences (FOV, 24 cm; matrix, 384 × 384 for ultrashort TE and 320 × 288 for T2-weighted spin-echo images; slice thickness, 2.8–3 mm; number of slices, 16–18). Two cases were excluded because of motion artifact. The remaining cases (patient age range, 20–75 years) were evaluated by two musculoskeletal radiologists. They recorded the number of fascia at each prevertebral region (C2–C7 levels, 42 levels total) in each sequence and the occurrence of trilaminar fascia (consistent with visceral, alar, and prevertebral fascia) in two or more consecutive vertebral levels to assess the continuity of the trilaminar morphology. The fascial morphology must have been visible in at least two consecutive sagittal slices to be valid. Interobserver variability was determined using the kappa statistic. The frequency of occurrence of trilaminar fascia in ultrashort TE images was compared with that in spin-echo T2-weighted images using the chi-square test.
Results: First, we found that a greater number of trilaminar fascia can be identified (p < 0.0001) on ultrashort TE (23 of 84 levels, both observers) than T2-weighted spin-echo (3 of 84) images. The levels where the trilaminar fascia were found most frequently in ultrashort TE images were C2 (4 of 14 levels), C3 (9 of 14) and C4 (9 of 14). Interobserver agreement for the morphology of fascia at each vertebral level was excellent for ultrashort TE (κ = 0.86) and substantial for T2-weighted spin-echo images (κ = 0.69). Secondly, we found a greater continuity (p = 0.02) of the trilaminar fascia in ultrashort TE (5 of 7 cases) than in T2-weighted spin-echo (0 of 7 cases) data, with excellent agreement (κ = 1.0).
Conclusion: Retropharyngeal space is a thin structure that is hard to evaluate using conventional T2-weighted spin-echo imaging. Ultrashort TE imaging appears to be sensitive for identifying the retropharyngeal space with good interobserver variability. Cadaveric study is needed to further validate these findings.