Optimization of brain MRA with contrast injection in 1.5 Tesla by high power RF

 Background and purpose: In brain MRA, selecting suitable parameters for imaging requires accurate measures, because the image quality depends on the location of arteries, veins and also the velocity differences of blood, due to the low flow of the blood in veins and small arteries.It is suggested to use paramagnetic contrast media. Hence in present study, we investigated the imaging optimization of brain vessels using contrast media in 1.5 Tasla high field power RF. Material and method: for image optimization after determining approximately T1at blood with contrast injection 0.1mmol/kg of Gd-DTPA , calculated relative signal of blood in T1=300,600,900,1200 ms by using parameter TR=20ms and TE=7ms, decrease T1,resulting increasing of Ernest angle and relative signal was shown .then, MRA was obtained in three groups, each including five volunteer patients by using parameters TR=20ms,TE=7ms and flip angle 10,20&30 degrees in two series without and during contrast injection. Then calculation C/N after measured signal of carotid, M.C.A, thorcolar herofili and SD in standard deviation of noise in air. by measurement it was shown that in 20 degrees flip angle, C/N maximize. At the last stage, three series MRA, without, during c.i and 15minutes after c.i where obtained in 20 patient volunteers by using parameters TR=20ms & TE=7ms and flip angle 20 degrees and calculated C/N. Results: we saw the highest C/N in during c.i MRA after statistical analysis. to be onfirm that if the difference between mean of C/N ratio is meaningfully we mutually compared them by paired t-student test. For clinical study, in obtained images, 1 vein and 2 arteries were graded in 5 definite levels. Conclusion: Results indicated an important effect of paramagnetic contrast media on better observing of small arteries and vein. The best quality was taken during c.i , but in some arteries contrast media had not any benefit in improving the quality. By taking advantage of the increased S/N provided by 3T magnets over conventional 1.5T magnets and converting this additional S/N into higher temporal resolution through acceleration strategies, intracranial time-resolved MRA becomes feasible. Several approaches to MR angiography (MRA), using different contrast mechanisms, have been developed, including time-of-flight (TOF), phase contrast (PC), T2-preparation, and contrast-enhanced (CE) MRA. Of these techniques, all can produce high-quality static images, but only first-pass multiphase CE-MRA is capable of capturing the dynamic filling of vessels, similar to conventional radiographic digital subtraction angiography (DSA).