Scientists and clinicians studying multiple sclerosis.Multiple sclerosis (MS) is an inflammatory and demyelinating disease that affects brain and spinal cord. White matter lesions are the hallmark of MS. MS lesions are routinely visualized with dual-echo and fluid-attenuated inversion recovery (FLAIR) imaging¹. FLAIR is particularly popular because it suppresses the cerebrospinal fluid, enhancing the contrast of periventricular lesions. Visualization of the veins running through MS lesions can provide additional discriminatory information about the diseases². However, veins are not readily detectable on FLAIR. T2*-weighted imaging (or susceptibility-weighted imaging; SWI) are sensitive techniques to detect veins and iron accumulation. Combined information from the SWI/T2* and FLAIR, by multiplying the two images, was employed in the FLAIR-SWI³ and the FLAIR*⁴ techniques to generate images that show both the lesions and the veins running through them. These techniques are promising. However, patient motion between the scans necessitates image registration, with the associated image-blurring resulting from numerical interpolation. This added complication is a barrier toward the clinical application of this method. To overcome the problem of motion in between the two sequences, we propose an interleaved sequence to simultaneously acquire FLAIR and SWI.Figue1 shows the proposed interleaved 3D FLAIR/SWI pulse sequence. An inversion recovery sequences with a variable-flip-angle turbo-spin echo (TSE) readout module is interleaved with a train of EPI-accelerated gradient echo (EPI-GRE) pulses. Two delay intervals (TD1 and TD2) are inserted before the start of the FLAIR and EPI-GRE modules, respectively. The delay allows the magnetization to recover before the FLAIR module to preserve the FLAIR image contrast, while the delay before the EPI-GRE module helps the magnetization approach steady state values in the GRE readout, thus minimizing k-space weighting and improving the point spread function. As a demonstration of the utility of this sequence in patients with neurological disorders, three relapsing-remitting MS patients were enrolled in an IRB-approved study and were scanned on a 3.0 T Philips Ingenia system (Philips, Best, The Netherlands). The imaging protocol included a standard 3D FLAIR sequence with the following parameters: TR/TE/TI = 4800 ms/304 ms/1650 ms, voxel size =1x1x1 mm³, FOV = 256x256x180 mm³, and NEX=2. The turbo-spin-echo readout included a train of 167, 40° refocusing pulses with 6 startup ramp-down pulses. 3D T2*-weighted images were obtained with a GRE sequence with TR/TE = 48 ms/25 ms, flip angle = 20°, EPI factor = 15, voxel size = 0.7x0.7x0.5 mm³ with the same FOV. Next, the interleaved FLAIR/SWI acquisition was collected using identical scan parameters with the following differences: every FLAIR readout module was interleaved with a train of 45 GRE pulses. The delay periods were set at TD1=2090 ms, and TD2=1345 ms. All images were Fourier interpolated (or reconstructed) to 0.5x0.5x0.5 mm³ grid. A minimum-intensity projection image of the T2* images (4-mm slab) was created and multiplied by the FLAIR image to create a susceptibility-weighted FLAIR (swFLAIR) image.The total scan duration to acquire 3D FLAIR and 3D T2*w datasets was 7:56 min, which increased to 9:12 min for the interleaved sequence (~15% longer scan time). Figure 2 shows an example of swFLAIR images acquired with the conventional and with the proposed interleaved technique. As can be seen from this figure, tissue contrast and image quality of FLAIR and T2* images with interleaved acquisition are comparable to those from the separate acquisitions. The computed swFLAIR image is similar between these two methods. A vein running through an MS lesion (arrows) can be equally seen on both scans.We demonstrated the feasibility of an interleaved sequence for simultaneous acquisition of FLAIR and SWI images. The interleaved sequence produces self-registered images and eliminates the need for extensive post-processing. In addition, careful selection of the sequence delays could provide another mechanism for controlling the vein-lesion contrast. This sequence enables clinical investigation of venous-related pathology in MS.