MR‐guided sclerotherapy of low‐flow vascular malformations using T2‐weighted interrupted bSSFP (T2W‐iSSFP): Comparison of pulse sequences for visualization and needle guidance. Issue 2 (6th January 2014) - Xu, Di
Abstract Purpose Image‐guided treatment of low‐flow vascular (venous or lymphatic) malformations presents a challenging visualization problem, regardless of the imaging modality being used for guidance. The purpose of this study was to employ a new magnetic resonance imaging (MRI) sequence, T2‐weighted interrupted balanced steady‐state free precession (T2W‐iSSFP), for real‐time image guidance of needle insertion. Materials and Methods T2W‐iSSFP uses variable flip angle balanced steady‐state free precession (bSSFP, a.k.a. SSFP) to establish T2‐weighting and fat suppression. Swine (n = 3) and patients (n = 4, three female, all with venous malformations) were enrolled in the assessment. T2‐weighted turbo spin echo (T2‐TSE) with spectral adiabatic inversion recovery (SPAIR), SPAIR‐T2‐TSE or T2‐TSE for short, was used as the reference. T2‐weighted half Fourier acquired single shot turbo spin echo (T2‐HASTE) with SPAIR (SPAIR‐T2‐HASTE, T2‐HASTE for short), fat saturated bSSFP (FS‐SSFP), and T2W‐iSSFP were imaged. Numeric metrics, namely, contrast‐to‐noise ratio (CNR) efficiency (CNR divided by the square root of acquisition time) and local sharpness (the reciprocal of edge width), were used to assess image quality. MR‐guided sclerotherapy was performed on the same patients using real‐time T2W‐iSSFP to guide needle insertion. Results Comparing the visualization of needles in the images of swine, the local sharpness (mm−1) was: 0.21 ± 0.06 (T2‐HASTE), 0.48 ± 0.02 (FS‐SSFP), and 0.49 ± 0.03 (T2W‐iSSFP). T2W‐iSSFP is higher than T2‐HASTE (P < 0.001). For the patient images, their CNR efficiencies were: 797 ± 66 (T2‐HASTE), 281 ± 44 (FS‐SSFP), and 860 ± 29 (T2W‐iSSFP). T2W‐iSSFP is higher than FS‐SSFP (P < 0.02). The frame rate of T2W‐iSSFP was 2.5–3.5 frames per second. All MR‐guided sclerotherapy procedures were successful, with all needles (six punctures) placed in the targets. Conclusion T2W‐iSSFP provides effective lesion identification and needle visualization. This new pulse sequence can be used for MR‐guided sclerotherapy of low‐flow vascular malformations. It may have potential use in other MR‐guided procedures where heavily T2‐weighted real‐time images are needed. J. Magn. Reson. Imaging 2015;41:525–535.© 2013 Wiley Periodicals, Inc.