Equilibrium-phase high spatial resolution contrast-enhanced MR angiography at 1.5T in preoperative imaging for perforator flap breast reconstruction spatial resolution imaging. The main reason for these poor results was the poor image quality of first-pass imaging. First pass imaging was only able to identify half the number perforator branches found with steady state imaging. In many cases, these missed perforator branches with first pass imaging turned out to be the single best perforator branch according to steady state imaging. This explains the large mis-match between first pass and steady state imaging. Image quality in equilibrium-phase imaging was high on the other hand. All equilibrium-phase high spatial resolution examinations were of diagnostic quality and in 13 out of 23 patients the image quality was qualified as excellent (i.e. there were no disturbing artifacts in the region of the single best perforator branch and high signal intensity was found both in the intramuscular and subcutaneous course of the perforator branch), whereas in 10 patients there were minor motion artifacts that did not interfere with the diagnostic accuracy of the exam. In first-pass acquisitions, however, severe motion artifacts due to the inability of patients to sustain a breath hold during acquisition resulted in 10 non-diagnostic examinations. Another important problem with first-pass imaging was the lack of signal in the intramuscu- lar part of perforator branches. Due to this problem, none of the first-pass acquisitions were of excellent image quality. Besides, signal-to-noise and contrast-to-noise ratios for equilibrium-phase imaging were significantly higher as compared to first-pass imaging. The superior diagnostic accuracy and image quality of equilibrium-phase imaging is probably the result of the relatively high spatial and contrast resolution compared to first-pass imaging. First-pass imaging was able to identify low signal intensity perforator branches within subcutaneous fat tissue, as the low signal intensity of the vessel fascia ensured a strong contrast with the high signal intensity of surrounding fat tissue. However, the intramuscular course of these perforator branches could not be determined due to the lack of intraluminal signal enhancement. However, the exact length and precise intramuscular course of the perforator branch is important as branches that course through muscle over extended lengths are difficult to dissect and associated with more postoperative pain. Equili- brium-phase imaging with a blood pool contrast agent shows that a longer TR and lower flip angle as well as higher spatial resolution results in better contrast resolution (proven by the significant increase in VNR and VBR for equilibrium-phase imaging) and higher sensitivity for identifying small caliber perforator branches respectively. Motion artifacts caused by breathing reduced image quality both in equili- 126
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