Bill Pass MBBCh, Presenter: Nothing to Disclose

Andrew J. Grainger MRCP, FRCR, Abstract Co-Author: Speaker, General Electric Company Equipment support, Siemens AG

Philip Robinson MBChB, Abstract Co-Author: Nothing to Disclose

Our institution’s standard 1.5T protocol for knee MRI comprises orthogonal 3 plane fat saturated (fs) proton density (PD), coronal T1 and sagittal T2 (fs) imaging. Our aim was to assess whether a single isotropic 3D fast spin-echo (FSE) PD(fs) sequence reconstructed in 3 planes could replace the 3 PD FS sequences in our standard protocol.

MRI studies of 95 knees were independently and prospectively interpreted by two experienced musculoskeletal radiologists over two separate readings at least 3 weeks apart. A 3D FSE PD(fs) sequence was added to our routine MRI protocol for the recruited patients with the images reconstructed at 2.5 mm in axial, coronal and sagittal planes and presented as individual sequences. 2.5 mm was selected following a separate pilot study to determine the optimal slice thickness. One observer read the conventional sequences first and for the second read replaced the 3 PD sequences with the reconstructed 3D sequences. The second reader performed the same two reads in opposite order. Following each read the observer was allowed to review the 3D data set and perform multi-planar reformats to see if this altered confidence. Menisci and ligaments were graded for the presence of a tear and articular cartilage for damage. Statistical analysis to calculate accuracy was performed comparing to our standard sequence as the reference standard.

We found that the accuracy for assessment of the menisci and cartilage surfaces was markedly reduced when using the reformatted 3D sequences. The reporting accuracy was as follows; medial meniscus (MM) = 90.9%, lateral meniscus (LM) = 93.7%, anterior cruciate ligament (ACL) = 98.9% and cartilage surfaces = 85.8%. Agreement between the two readers was also reduced using the 3D sequence (Standard protocol: MM kappa=0.91, LM =0.89, ACL= 0.98, cartilage= 0.84; 3D protocol: MM=0.86, LM=0.77, ACL=0.94, cartilage= 0.64).  

Use of a 3D PD FSE sequence reconstructed in 3 planes gives reduced accuracy in comparison with conventional 3 plane PD FS sequences when evaluating menisci and cartilage surfaces with a 1.5T MRI scanner. The present study indicates a decreased level of concordance between readers for the reconstructed 3D (SPACE) sequence.

At 1.5T a 3D PD FSE sequence reconstructed in 3 planes demonstrates reduced accuracy and confidence in reporting in comparison with conventional 3 plane PD FS sequences.

Pass, B, Grainger, A, Robinson, P, Can a Single Isotropic 3D FSE Sequence Replace 3 Plane Standard PD FS Knee MRI Imaging at 1.5T?.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14006116.html