[Non-electrocardiogram-gated and Non-contrast-enhanced Magnetic Resonance Angiography of the Lower Limb Arteries Using Three-dimensional Multishot T1-weighted Fast-field Echo-Echo Planar Imaging].

We performed a non-electrocardiogram-gated and non-contrast-enhanced magnetic resonance angiography (MRA) of the lower limb arteries using three-dimensional multishot T1-weighted fast-field echo-echo planar imaging (3D multishot T1-FFE-EPI), and it was optimized the protocol. The image distortion for the change in the EPI factor was calculated using 3.0 T-MRI and MRI phantom. We also calculated the signal-to-noise ratio (SNR) of the femoral artery with a change in the flip angle on images of 8 healthy volunteers. Furthermore, the optimal EPI factor was determined from the SNR of the femoral artery and the contrast ratio between the femoral artery and the adductor magnus. Two radiological technologists performed a retrospective visual assessment of the pelvis, thigh, and leg of 10 patients who underwent lower limb non-contrast-enhanced MRA and contrast-enhanced tomography angiography (CTA). The optimum flip angle and EPI factor were 25° and 3, respectively. In the visual assessment of clinical cases, there was no significant difference between the non-contrast-enhanced MRA and contrast-enhanced CTA in the pelvis and the leg (p=0.52 and p=0.88, respectively). In the thigh, non-contrast-enhanced MRA was significantly higher (p=0.02), namely, the ability to visualize the lower limb arteries was not much difference between this method and contrast-enhanced CTA. Our method without electrocardiogram gated and contrast medium is expected for screening tests or detailed examinations.

[Optimization of black blood CINE for mobile plaque].

For examining carotid plaque, black blood (BB) magnetic resonance (MR) imaging can diagnose plaque components based on MR signals. Dynamic images for evaluating the mobility of carotid plaque may also be useful as an adjunct to the diagnosis of carotid plaque. The aim of this study was to find optimal parameters for dynamic images using the black blood technique (BB CINE). All experiments were acquired using electrocardiographically (ECG)-gated T1 turbo field echo (T1 TFE) combined with the regional saturation technique (REST) and improved motion-sensitized driven equilibrium (iMSDE) at 1.5 tesla (T). The following parameters were investigated. (1) Four fat suppression techniques: spectral presaturation with IR (SPIR), the principle of selective excitation technique (PROSET) with a binomial excitation of 1-1 (PROSET1-1), PROSET1-2-1 and PROSET1-3-3-1; (2) TFE factors 1 and 2; and (3) flow velocity encoding (venc) of 1, 3, 5, 10 and 15 cm/s for iMSDE. The results showed the optimal parameters for BB CINE to be PROSET1-2-1, TFE factor 2, and flow venc of 3-5 cm/s for iMSDE.