ABSTRACT
PURPOSE: To investigate the feasibility of high-dose dobutamine stress (HDDS) imaging using SSFP sequences at 3âT employing patient-adaptive local RF-shimming using a dual-source RF transmission system. MATERIALS AND METHODS: 13 Patients underwent a HDDS protocol on a 3âT MRI scanner (Achieva 3.0T-TX, Philips Healthcare), equipped with a dual-source RF transmission system. SSFP cine sequences using patient-adaptive local RF-shimming (RF-S) were compared to cine images acquired without additional shimming. Image quality was evaluated on a 4-point grading scale and number of non-diagnostic segments assessed. Contrast (CN) between myocardium (SIM) and blood pool (SIB) was calculated [(SIB-SIM)/(SIB+SIM)]. RESULTS: Image quality both at rest and maximum stress was significantly improved with RF-S (ED:3.56±0.5 vs. 3.23±0.63; ES:3.4±0.5 vs. 3.1±0.7) compared to no RF-S (ED:2.9±0.72 vs. 2.15±0.78; ES:2.64±0.74 vs. 1.95±0.76; p<0.01). The amount of non-diagnostic segments was significantly reduced when using RF-S at rest and stress (3 vs. 39; 19 vs. 78, p<0.05). All HDDS studies were diagnostic if performed with RF-S (n=13/13) in comparison to conventional shimming (n=5/13). Image contrast was improved for SSFP sequences with RF-S (0.53±0.08) compared to conventional images (0.46±0.09, p=0.06). CONCLUSION: Patient-adaptive local RF-shimming using a dual-source RF transmission system allows for reliable SSFP imaging in a clinical high-dose dobutamine stress protocol at 3âT. RF-S significantly improves image quality and reduces the number of non-diagnostic myocardial segments.
Subject(s)
Algorithms , Coronary Occlusion/pathology , Dobutamine/administration & dosage , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Magnetic Resonance Imaging, Cine/methods , Exercise Test/methods , Feasibility Studies , Female , Humans , Male , Middle Aged , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
OBJECTIVE: We prospectively evaluated the feasibility and technical features of MR-guided lumbosacral injection procedures in open high-field MRI at 1.0 T. METHODS: In a CuSO(4).5H(2)O phantom and five human cadaveric spines, fluoroscopy sequences (proton-density-weighted turbo spin-echo (PDw TSE), T1w TSE, T2w TSE; balanced steady-state free precession (bSSFP), T1w gradient echo (GE), T2w GE) were evaluated using two MRI-compatible 20-G Chiba-type needles. Artefacts were analysed by varying needle orientation to B(0), frequency-encoding direction and slice orientation. Image quality was described using the contrast-to-noise ratio (CNR). Subsequently, a total of 183 MR-guided nerve root (107), facet (53) and sacroiliac joint (23) injections were performed in 53 patients. RESULTS: In vitro, PDw TSE sequence yielded the best needle-tissue contrasts (CNR = 45, 18, 15, 9, and 8 for needle vs. fat, muscle, root, bone and sclerosis, respectively) and optimal artefact sizes (width and tip shift less than 5 mm). In vivo, PDw TSE sequence was sufficient in all cases. The acquisition time of 2 s facilitated near-real-time MRI guidance. Drug delivery was technically successful in 100% (107/107), 87% (46/53) and 87% (20/23) of nerve root, facet and sacroiliac joint injections, respectively. No major complications occurred. The mean procedure time was 29 min (range 19-67 min). CONCLUSION: MR-guided spinal injections in open high-field MRI are feasible and accurate using fast TSE sequence designs.
