Bernd Bittersohl MD, Presenter: Nothing to Disclose

Klaus A. Siebenrock MD, PhD, Abstract Co-Author: Nothing to Disclose

Martin Beck MD, Abstract Co-Author: Nothing to Disclose

Timothy Hughes PhD, Abstract Co-Author: Employee, Siemens AG

Stefan F. Werlen MD, Abstract Co-Author: Nothing to Disclose

Tallal Charles Mamisch MD, Abstract Co-Author: Research Consultant, Siemens AG, Erlangen, Germany

To evaluate the value of 3D T2* mapping quantification based on gradient echo (GRE) MRI for diagnosis of early osteoarthritic changes in femoroacetabular impingement (FAI.) Standard MRI and fast T1 mapping using contrast administration (dGEMRIC) were used for comparison.

33 FAI patients and 8 normal volunteers with no clinical signs of FAI or other hip disorder were examined at 1.5T. The MR protocol included standard sequences post gadolinium administration (axial T1 weighted 2D TSE, coronal PD weighted 2D TSE, sagittal PD weighted 2D TSE, radial positioned intermediate weighted 2D TSE), and a dual flip angle 3D GRE sequence (VIBE) for T1 assessment (TR/TE/FA = 25/3,6/35°-10°, 0.78mm slice-thickness, 200mm FOV, 512x512 matrix.) Pre contrast agent administration, a 3D GRE sequence (MEDIC) of 6 echoes to obtain T2*-mapping was performed: TR/TE/FA ~ 600/5.7, 9.8, 14, 18.1, 22.2, 26.4/20°, 0.78mm slice- thickness, 200mm FOV, 512x512 matrix. The cartilage was classified normal, mildly changed or severely degenerated on standard MRI and correlated with T1 (dGEMRIC) and T2* findings in 7 radial positions from anterior to superior to posterior. Measurements were stated as mean and standard deviation. Quantitative assessment was performed using ANOVA. For correlation of standard MRI, T1-, and T2*- mapping, the two-tailed Spearman test was utilized.

287 regions were investigated. 45 regions were excluded due to total cartilage loss. Between each cartilage grade statistical difference was found for both techniques, as well in the volunteer group as in FAI patients. Within the patient group 98 regions were classified normal, 29 mildly-, and 79 severely degenerated. Mean T2* values ranged from 33.5ms (normal) to 29.3ms (severe.) Mean T1 range: 548.0ms (normal) to 489.6ms (severe.) Spearman’s correlation analyses revealed correlation factors of -.234 between T2* and standard MRI, and -.506 between dGEMRIC and standard MRI. Intra-observer reproducibility was 0.96 (T2* and dGEMRIC.) Inter-observer agreement: 0.93 / 0.91 (T2* / dGEMRIC.)

T2* mapping at 1.5T using the fast GRE technique is a feasible non-contrast technique and provides information about cartilage’ status within the hip.

T2* mapping may be an alternative to the use of contrast agent for precise cartilage diagnosis and enables 3D acquisition with high spatial resolution.

Bittersohl, B, Siebenrock, K, Beck, M, Hughes, T, Werlen, S, Mamisch, T, Feasibility of T2* Mapping for the Evaluation of Hip Joint Cartilage at 1.5 T Using a Three-dimensional, Gradient Echo Sequence.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6020425.html