Here we describe a new hyperpolarization approach for magnetic resonance imaging applications at 1.5 T. Proton signal enhancements of more than 20 were achieved with a newly designed multimode microwave resonator situated inside the bore of the imager and used for Overhauser dynamic nuclear polarization of the water proton signal. Different from other approaches in our setup the hyperpolarization is achieved continuously by liquid water flowing through the polarizer under continuous microwave excitation. With an available flow rate of up to 1.5 ml/min, which should be high enough for DNP MR angiography applications in small animals like mice and rats. The hyperpolarized liquid cooled to physiological temperature can be routed by a mechanical switch to a quartz capillary for injection into the blood vessels of the target object. This new approach allows hyperpolarization of protons without the need of an additional magnet and avoids the losses arising from the transfer of the hyperpolarized solution between magnets. The signal-to-noise improvement of this method is demonstrated on two- and three-dimensional phantoms of blood vessels.

Objectives: The aim of this study was to compare 2 advanced robotic angiography systems for real-time image guidance in terms of radiation dose and image quality (IQ) during conventional transarterial chemoembolization (C-TACE) of hepatic malignant tumors. Materials and Methods: One hundred six patients (57 women/49 men; mean age, 60 ± 11 years) who had undergone C-TACE using 2 generations of robotic angiography platforms for image guidance were included in this retrospective study. Patients were divided into 2 groups (n = 53, respectively): group 1 (first generation) and group 2 (second generation). Radiation dose for fluoroscopy and digital subtraction angiography (DSA) was compared between first-generation and second-generation angiography equipment, respectively. Among several features of the second-generation compared with the first-generation system, improvements included a refined crystalline detector system for enhanced noise reduction and advanced CARE filter software for lowering radiation dose. Radiation dose was measured using an ionization chamber. Image quality was assessed by 3 radiologists using 5-point Likert scales. Results: Both groups were comparable in terms of number and location of lesions, as well as body weight, body mass index, and anatomical variants of feeding hepatic arteries (all P > 0.05). Dose-area product (DAP) for fluoroscopy was significantly lower in group 2 (1.4 ± 1.1 Gy•cm 2 ) compared with group 1 (2.8 ± 3.4 Gy•cm 2 ; P = 0.001). For DSA, DAP was significantly lower (P = 0.003) in group 2 (2.2 ± 1.2 Gy•cm 2 ) versus group 1 (4.7 ± 2.3 Gy•cm 2 ). Scores for DSA IQ indicated significant improvements for group 2 by 30% compared with group 1 (P = 0.004). Regarding fluoroscopy, scores for IQ were 76% higher in group 2 compared with group 1 (P = 0.001). Good to excellent interrater agreement with Fleiss kappa coefficients of κ = 0.75 for group 1 and κ = 0.74 for group 2 were achieved. Conclusions: Most recent generation robotic angiography equipment allows for considerable radiation dose reductions while improving IQ in fluoroscopy and DSA image guidance during C-TACE treatment.

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