Camera-based respiratory triggering improves the image quality of 3D magnetic resonance cholangiopancreatography

Purpose: To evaluate the performance of a novel camera-based breathing navigation system in respiratory-triggered (CRT) 3D-magnetic resonance cholangiopancreatography (MRCP) at 3T MRI. Methods: Two 3D-MRCP data sets were acquired subsequently within one imaging session with traditional respiratory belt- (BRT) or camera- (CRT) based triggering in 28 patients. Overall image quality, blurring, motion artifacts and discernibility of the pancreaticobiliary tree (PBT) structures were scored on a 4-point scale retrospectively by 2 radiologists. The contrast ratio between the common bile duct and its adjacent tissue was measured by region-of-interest (ROI) analysis. The signal intensity increase at the duct boundaries was quantified by line profiles to objectify blurring and motion artifacts. The extracted respiratory signal curves were analyzed for signal quality and trigger timing. Results: Total scan time was 72 s for both acquisitions. CRT yielded significantly better ratings in image quality, background suppression, blurring and discernibility of PBT structures compared to BRT. Contrast ratios were significantly higher in CRT (0.94 +/- 0.03) than in BRT (0.93 +/- 0.03) exams; paired t test P= 0.0017. Line profile slopes through the common bile duct revealed significantly higher values in CRT (42.23 +/- 8.74% of maximum intensity/mm) compared to BRT (36.06 +/- 8.96% of maximum intensity/mm; paired t test P < 0.0001). Camera-derived respiratory signal curves showed a higher SNR, lower standard deviation of the signal amplitude and less incorrect triggering than the respiratory belt-derived respiratory signal curves. Conclusion: Camera-based respiratory triggering significantly improves image quality of 3D-MRCP compared to conventional respiratory belt triggering.