Three-Dimensional Zero Echo Time Magnetic Resonance Imaging Versus 3-Dimensional Computed Tomography for Glenoid Bone Assessment

Abstract

Purpose: To evaluate the 3-dimensional (3D) zero echo time (ZTE) magnetic resonance imaging (MRI) technique and compare it with 3D computed tomography (CT) for the assessment of the glenoid bone.

Methods: ZTE MRI using multiple resolutions and multislice CT were performed in 6 shoulder specimens before and after creation of glenoid defects and in 10 glenohumeral instability patients. Two musculoskeletal radiologists independently generated 3D volume-rendered images of the glenoid en face. Post-processing times and glenoid widths were measured. Inter-modality and inter-rater agreement was assessed.

Results: Intraclass correlation coefficients (ICCs) for inter-modality assessment showed almost perfect agreement for both readers, ranging from 0.949 to 0.991 for the ex vivo study and from 0.955 to 0.987 for the in vivo patients. Excellent interobserver agreement was found for both the ex vivo (ICCs ≥ 0.98) and in vivo (ICCs ≥ 0.92) studies. For the ex vivo study, Bland-Altman analyses for CT versus MRI showed a mean difference of 0.6 to 1 mm at 1.0-mm³ MRI resolution, 0.3 to 0.6 mm at 0.8-mm³ MRI resolution, and 0.3 to 0.6 mm at 0.6-mm³ MRI resolution for both readers. For the in vivo study, Bland-Altman analyses for CT versus MRI showed a mean difference of 0.6 to 0.8 mm at 1.0-mm³ MRI resolution, 0.5 to 0.6 mm at 0.8-mm³ MRI resolution, and 0.4 to 0.8 mm at 0.7-mm³ MRI resolution for both readers. Mean post-processing times to generate 3D images of the glenoid ranged from 32 to 46 seconds for CT and from 33 to 64 seconds for ZTE MRI.

Conclusions: Three-dimensional ZTE MRI can potentially be considered as a technique to determine glenoid width and can be readily incorporated into the clinical workflow.

Level of evidence: Level II, development of diagnostic criteria (consecutive patients with consistently applied reference standard and blinding).

Figure 1:

Axial CT and ZTE MRI images obtained of the left shoulder of a 38-year-old man. (A) CT, (B) ZTE MRI 1.0 mm, (C) ZTE MRI 0.8 mm and (D) ZTE MRI 0.7 mm axial images all demonstrate high-contrast imaging of the osseous structures, including the glenoid and glenohumeral joint. ZTE, zero echo time.

Figure 2:

Glenoid width measurement method shown in an ex-vivo right scapula (21-year-old donor). (A) 3D CT, (B) 3D ZTE MRI 1.0 mm, (C) 3D ZTE MRI 0.8 mm and (D) 3D ZTE MRI 0.6 mm images with en face view of the glenoid shows the width measurement, defined as the largest anteroposterior measurement in the lower two-thirds of the glenoid, measured perpendicular to the long axis. ZTE, zero echo time.

Figure 3:

Ex-vivo study: Bland-Altman plots of the differences between 3D CT and 3D ZTE MRI for glenoid width measurements. (A), (C), and (E) represent plots at 1, 0.8, and 0.6 mm ZTE resolution for Reader 1, respectively, and (B), (D), and (F) represents those for Reader 2. The solid lines represent the mean differences (bias), and the dashed lines indicate the 95% limits of agreement. It is expected that the limits include 95% of differences between the two measurement methods. Each glenoid at a particular condition is represented by an individual point. Black dots: pre-lesion glenoids. Hollow circles: post-lesion glenoids. ZTE, zero echo time.

Figure 4:

Glenoid width measurement method shown in a left scapula of a 29-year-old man. (A) 3D CT, (B) 3D MRI 1.0 mm, (C) 3D MRI 0.8 mm and (D) 3D MRI 0.7 mm images with en face view of the glenoid shows the width measurement, defined as the largest anteroposterior measurement in the lower two-thirds of the glenoid, measured perpendicular to the long axis. ZTE, zero echo time.

Figure 5:

In vivo study: Bland-Altman plots of the differences between 3D CT and 3D ZTE MRI for glenoid width measurements. (A), (C), and (E) represent plots at 1, 0.8, and 0.7 mm ZTE resolution for Reader 1, respectively, and (B), (D), and (F) represents those for Reader 2. The solid lines represent the mean of all differences (bias), and the dashed lines indicate the 95% limits of agreement. It is expected that the limits include 95% of differences between the two measurement methods. Each study participant is represented by an individual point. ZTE, zero echo time.