Pseudocontinuous arterial spin labeling (pCASL) was incorporated into a quiescent-interval slice-selective (QISS) pulse sequence in order to facilitate vessel-selective nonenhanced MR angiography (MRA). The technique was evaluated for selective imaging of the left ventricle and ascending aorta, as well as for selective imaging of the abdominal veins.Nonenhanced QISS MRA has previously been applied in several vascular territories, including the peripheral, renal, carotid, and coronary arteries^1-3. Thick (e.g. 10cm) saturation pulses are used to suppress unwanted vascular signal (e.g. veins for peripheral MRA). However, in other clinical scenarios anatomic considerations may hinder the efficacy of saturation pulses. For instance, it can be problematic to apply thick saturation pulses to one cardiac chamber without inadvertently suppressing signal in a different cardiac chamber, given that the cardiac chambers are closely apposed. For imaging of the abdominal veins, it may not be possible to apply a sufficiently thick saturation pulse to fully suppress aortic signal given high systolic flow velocities. We propose an alternative approach using pseudocontinuous arterial spin-labeling (pCASL), which repeated applies RF pulses to a relative thin labeling region in order to produce downstream inversion of flowing spins. When incorporated into the quiescent interval of a QISS pulse sequence, the pCASL RF pulses span the period of rapid systolic blood flow, thus ensuring maximal downstream distribution of the labeled spins. We used this method to selectively image the ascending aorta and abdominal veins.The pCASL QISS technique (Figure 1) was applied in healthy volunteers at 1.5T (Magnetom Avanto, Siemens Healthcare). The sequence consisted of a breath-hold ECG-gated radial balanced steady-state free precession acquisition that was preceded by an in-plane saturation RF pulse and pseudocontinuous labeling (1.5ms repetition time, 50 degree flip angle). For single-shot QISS, 20 slices were acquired per breath-hold compared with 10 slices for two-shot QISS. 96 radial views were accumulated per slice, TR/TE=3.2-3.8/1.6ms, flip 180 degrees, 0.8mm in-plane spatial resolution, 2-3mm slice thickness. For selective imaging of the left ventricle and ascending aorta, the pseudocontinuous labeling plane (~3cm thickness) was applied obliquely through the right atrium and right ventricle for 500-600ms prior to the radial bSSFP readout. Care was taken to avoid overlapping the label with the left cardiac chambers and ascending aorta. The abdominal veins were imaged after applying pCASL axially through the distal descending thoracic aorta in order to suppress signal in the abdominal aorta. The percentage reduction in vascular signal was computed with respect to a non-pCASL acquisition.Figures 2 and 3 show maximum intensity projection images obtained with the pCASL QISS technique. With pseudocontinuous labeling of the right atrium and right ventricle (Figure 2), the left ventricle, aortic root and ascending aorta arch were well delineated, while the pulmonary arteries and right cardiac chambers appeared uniformly dark. The signal intensities of the right atrium and pulmonary arteries were reduced 73% and 70% respectively by pCASL. Pseudocontinuous labeling of the distal descending thoracic aorta (Figure 3) suppressed abdominal aortic signal by 72% and provided excellent depiction of the portal and systemic abdominal veins.pCASL QISS provides a flexible option for vessel-selective nonenhanced MRA. Selective suppression of unwanted vascular signal was achieved without inadvertent suppression of signal in target vessels. Scan time is the same as for standard QISS. In addition the examples provided, the method may have applications in the imaging of cardiac shunts and valvular heart disease.