Three-dimensional sampling perfection with application-optimised contrasts using a different flip angle evolutions sequence for routine imaging of the spine: preliminary experience

Abstract

Objectives: The bulk of spinal imaging is still performed with conventional twodimensional sequences. This study assesses the suitability of three-dimensional sampling perfection with application-optimised contrasts using a different flip angle evolutions (SPACE) sequence for routine spinal imaging. Methods: 62 MRI examinations of the spine were evaluated by 2 examiners in consensus for the depiction of anatomy and presence of artefact. We noted pathologies that might be missed using the SPACE sequence only or the SPACE and a sagittal T 1 weighted sequence. The reference standards were sagittal and axial T 1 weighted and T 2 weighted sequences. At a later date the evaluation was repeated by one of the original examiners and an additional examiner. Results: There was good agreement of the single evaluations and consensus evaluation for the conventional sequences: k.0.8, confidence interval (CI).0.6-1.0. For the SPACE sequence, depiction of anatomy was very good for 84% of cases, with high interobserver agreement, but there was poor interobserver agreement for other cases. For artefact assessment of SPACE, k50.92, CI50.92-1.0. The SPACE sequence was superior to conventional sequences for depiction of anatomy and artefact resistance. The SPACE sequence occasionally missed bone marrow oedema. In conjunction with sagittal T 1 weighted sequences, no abnormality was missed. The isotropic SPACE sequence was superior to conventional sequences in imaging difficult anatomy such as in scoliosis and spondylolysis. Conclusion: The SPACE sequence allows excellent assessment of anatomy owing to high spatial resolution and resistance to artefact. The sensitivity for bone marrow abnormalities is limited. Conventional MRI protocols of the spine often consist of T 1 weighted and T 2 weighted sagittal and axial sequences. The axial images are acquired as blocks or parallel to an intervertebral disc space.A number of imaging centres use three-dimensional (3D) T 2 weighted sequences for imaging of the spine; however, these sequences are used for assessment in the axial plane only [1,2]. With older sequence types there have been compromises in the signal-to-noise ratio, spatial resolution and contrast resolution, although the advantage of the 3D reconstruction ability has been recognised [3,4]. Various sequences have been assessed for suitability, with particular emphasis on the depiction of the intervertebral foramina [1,4,5]. There has also been interest in imaging the whole spine with T 2 weighting-based 3D sequences [6].The 3D sampling perfection with application-optimised contrasts using different flip angle evolutions (SPACE) sequence is a turbo spin-echo T 2 weighted 3D sequence using variable flip angles for refocusing instead of the conventional 180 u refocusing pulse.The aim of this study was to assess the suitability of the 3D SPACE sequence for imaging of the spine. The isotropic 3D SPACE sequence was evaluated in its delineation of anatomy and pathology, particularly in anatomically difficult locations. The capacity to ...

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