Experimental Research And Clinical Application Of A SLEEK Sequence

Purpose: To investigate the relation between blood suppression inversion time (BSP TI) and the blood flow velocity (V) in an invitro study and to improve the vessel visibility of using a suitable BSP TI in SLEEK sequence.MATERIALS AND METHODS: A round plastic container was taked (diameter: 15cm), in which a catheter (interior diameter: 2mm) simulated as vessel was imbedded by pork fat. The catheter was connected to a high pressure injector which injected saline (simulated as blood flow) with the velocity=0.1,0.2,0.5,1.0,2.0,3.0,4.0ml/s respectively. For every rate, four SLEEK scans were carried out using various BSP TI with100,500,800,1100ms . All other scan parameters were identical. All images with SLEEK were evaluated and the SNR of simulated vessel were measured by two experienced radiologists using a joint reading performed in consensus. Lastly, the relation between BSP TI and V in invitro experiment was analyzed. Results: All SLEEKs were successfully undergone. For the SLEEK images with BSP TI =100ms, the saline rate with 3.0ml/s was presented primarily as high intensity in the catheter and with 4.0ml/s was showed the most high SNR(0.927) in it. For images with BSP TI =500ms, the rate with 2.0ml/s was presented firstly as high intensity and with 3.0ml/s was showed the most high SNR (1.732). For images with BSP TI =800ms, the rate with 0.5ml/s was presented firstly as high intensity and with 1.0ml/s was showed the most high SNR(2.256). For images with BSP TI =1100ms, the rate with 0.2ml/s was displayed firstly as high intensity and with 1.0ml/s was described the most high SNR(1.875).Conclusion: A negative relation was found between BSP TI and V in our study. A suitable BSP TI helps to improve the ability of delineating vessel with SLEEK for various blood flow rate. PURPOSE: To reveal the decisive factors influencing blood suppression inversion time (BSP TI) and to investigate whether a suitable BSP TI can help to improve renal arterial visibility for hypertension subjects in a new non-contrast enhanced magnetic resonance angiography (NCE-MRA) using a spatial labeling with multiple inversion pulses (SLEEK).MATERIALS AND METHODS: The study protocol was approved by the local Research Ethics Committee. Informed consent was obtained from all subjects. A total of 95 subjects underwent SLEEK for showing renal artery at 1.5T MRI system including 10 volunteers and 85 consecutive hypertension patients. Firstly, various BSP TIs would be carried out in SLEEK to determine BSP TI values for displaying clearly renal arterial in 10 volunteers. Secondly, the same BSP TIs value as above would be undergone in those hypertension patients. Then, renal artery was evaluated and a suitable BSP TI to increase arterial visibility was determined for each patient by two experienced radiologist in their consensus. All information including respiratory rate (RR), cardiac rate (CR), BSP TI, the suitable BSP TI, the finding of renal artery, age, sex and weight would be recorded and the relationships between BSP TI and other elements were determined via a retrospective study.Results: BSP TIs of visualizing distinctly renal artery were 800ms, 1100ms or 1400ms for 10 volunteers. For hypertension subjects, a suitable BSP TI in SLEEK may increase the renal arterial visibility and the BSP TI was impacted by RR and CR. The negative correlation between BSP TI and RR, CR was found and the related coefficient respectively was 0.50727 (P<0.0001) and 0.35275(P=0.0013). BSP TI has no noticeable correlation with Sex (P=0.1373), age (P= 0.2301), weight (p=0.2455) and the renal artery findings (P=0.0535). The suitable BSP TI was 800ms in SLEEK for more clearly displaying renal artery when RR was 17-19bpm (95% CI) and CR was74-82bpm (95% CI); the suitable BSP TI was 1100ms when RR was 14-15bpm (95% CI) and CR was71-77bpm (95% CI); he suitable BSP TI was 1400ms when RR was 13-16bpm (95% CI) and CR was62-69bpm (95% CI).Conclusion: The negative correlation between BSP TI and RR, CR was found and a suitable BSP TI can improve the visibility of renal artery in SLEEK scan. It is helpful to evaluate renal artery and to raise working efficiency. Materials and Methods: NC-MRA using SLEEK was carried out on a 1.5 T MR system for assessing renal arteries in 50 patients with hypertension. Then all patients underwent computed tomography angiography (CTA) within1-7days. The ability to present the renal arteries and diplay renal artery disease with SLEEK were evaluated by two experienced radiologists, and were compared with CTA results using a joint reading performed in consensus.Results: 46 patients were undergone successfully SLEEK. A total of 119 renal arteries were assessed including 86 normal, 26 stenoses, 7 Fibromuscular dysplasia (FMD) on CTA in these 46 hypertension patients. The excellent correlation between SLEEK and CTA was found in presenting the renal artery stenosis (RAS) degree (Rs=0.851, p<0.05). SLEEK was superior to CTA in demonstrating the third and fourth order segmental branches in the renal parenchyma (P<0.05). SLEEK has the advantage of avoiding certain interferences from vertebra, atherosclerotic plaques and early venous system enhancement.Conclusions: NC-MRA using SLEEK represents a non-renal complication, relatively inexpensive, and reliable diagnostic method for evaluating renal artery disease and displaying segmental branches in the renal parenchyma. It can be as an alternative choice of CTA for screening renal artery diseases, especially in those hypertension subjects with renal insufficiency.