Purpose: To develop a new pulse sequence called timeresolved angiography with stochastic trajectories (TWIST) Dixon for dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Materials and Methods:The method combines dual-echo Dixon to generate separated water and fat images with a k-space view-sharing scheme developed for 3D TWIST. The performance of TWIST Dixon was compared with a volume interpolated breathhold examination (VIBE) sequence paired with spectrally selective adiabatic inversion Recovery (SPAIR) and quick fat-sat (QFS) fat-suppression techniques at 3.0T using quantitative measurements of fat-suppression accuracy and signal-to-noise ratio (SNR) efficiency, as well as qualitative breast image evaluations. Results:The water fraction of a uniform phantom was calculated from the following images: 0.66 6 0.03 for TWIST Dixon; 0.56 6 0.23 for VIBE-SPAIR, and 0.53 6 0.14 for VIBE-QFS, while the reference value is 0.70 measured by spectroscopy. For phantoms with contrast (Gd-BOPTA) concentration ranging from 0-6 mM, TWIST Dixon also provides consistently higher SNR efficiency (3.2-18.9) compared with VIBE-SPAIR (2.8-16.8) and VIBE-QFS (2.4-12.5). Breast images acquired with TWIST Dixon at 3.0T show more robust and uniform fat suppression and superior overall image quality compared with VIBE-SPAIR. Conclusion:The results from phantom and volunteer evaluation suggest that TWIST Dixon outperforms conventional methods in almost every aspect and it is a promising method for DCE-MRI and contrast-enhanced perfusion MRI, especially at higher field strength where fat suppression is challenging.

With proper parameters, TWIST-Dixon provides higher perceived SNR, more accurate fat suppression, and better overall image quality for breast DCE-MRI without sacrificing accuracy in the enhancement estimation.

Metal implants introduce artifacts of different types and sizes, according to the different fat-suppression techniques used. The dual-echo Dixon technique produces a larger central void, allowing the implant to be easily identified, but presents a smaller overall artifact volume by obscuring less area in the image, according to a quantitative phantom study.

Dixon water-only images provided more reliable estimation of T1, Gd, and pharmacokinetic parameters when fat was present.

The purpose of this study is to develop and evaluate a displacement-encoded pulse sequence for simultaneous perfusion and strain imaging. Displacement-encoded images in two to three myocardial slices were repeatedly acquired using a single-shot pulse sequence for 3 to 4 min, which covers a bolus infusion of Gadolinium contrast. The magnitudes of the images were T 1 weighted and provided quantitative measures of perfusion, while the phase maps yielded strain measurements. In an acute coronary occlusion swine protocol (n 5 9), segmental perfusion measurements were validated against microsphere reference standard with a linear regression (slope 0.986, R 2 5 0.765, Bland-Altman standard deviation 5 0.15 mL/min/g). In a group of ST-elevation myocardial infarction patients (n 5 11), the scan success rate was 76%. Shortterm contrast washout rate and perfusion are highly correlated (R 2 5 0.72), and the pixelwise relationship between circumferential strain and perfusion was better described with a sigmoidal Hill curve than linear functions. This study demonstrates the feasibility of measuring strain and perfusion from a single set of images. Magn Reson Med 64:787-798, 2010. V C 2010 Wiley-Liss, Inc. Key words: ischemia; viability; myocardial perfusion; strain; first pass; DENSE Regional contractile function and perfusion are two key indices in the diagnosis and prognosis of ischemic heart disease. MRI can accurately assess myocardial wall motion and strain through several techniques, including tagged MRI (1-4), velocity-encoded MRI (5), and displacement-encoded MRI (6-8). Contrast-enhanced imaging, including first-pass (9-15) and delayed hyperenhancement MRI (16-21), provides information on the perfusion and viability status of the myocardial tissue. Whether the clinical situation is to assess the efficacy of reperfusion strategy with greater accuracy or to recognize patients who would require further therapy, the knowledge of both regional myocardial function and perfusion is helpful in differentiating among the various scenarios.An MRI pulse sequence capable of measuring myocardial perfusion and strain in a single data set, which thus far has not been generally possible in humans, would save scan time and facilitate perfusion-function correlation by eliminating the problem of registration. Imaging techniques that combine myocardial strain and delayed hyperenhancement imaging have been reported by several groups (22,23). However, these techniques employed interleaved acquisition of multiple images, which are combined into single-strain and delayed hyperenhancement images; therefore, they are not suited for first-pass perfusion imaging due to the time constraints.The purpose of this study is to develop a pulse sequence for simultaneous perfusion and strain imaging, to validate the perfusion measurement in a swine model, and to assess its performance in a group of acute myocardial infarction patients.The pulse sequence is a single-shot, multislice displacement-encoded (DENSE) (7) sequence. It was used to collect displace...