Purpose To develop a fast and accurate mono-exponential fitting algorithm based on AutoRegression on Linear Operations (ARLO) of data, and to validate its accuracy and computational speed by comparing it with the conventional Levenberg-Marquardt (LM) and Log-Linear (LL) algorithms. Methods ARLO, LM and LL performances for T2* mapping were evaluated in simulation and in vivo imaging of liver (n=15) and myocardial (n=1) iron overload patients and the brain (2 healthy volunteers). Results In simulations, ARLO consistently delivered accuracy similar to LM and significantly superior to LL. In in vivo mapping of T2* values, ARLO showed excellent agreement with LM, while LL showed only limited agreements with ARLO and LM. Compared to LM and LL in the liver, ARLO was 125 and 8 times faster using our Matlab implementations, and 156 and 13 times faster using our C++ implementations. In C++ implementations, ARLO reduced the online whole-brain processing time from 9 min 15 sec of LM and 35 sec of LL to 2.7 sec, providing T2* maps approximately in real time. Conclusion Due to comparable accuracy and significantly higher speed, ARLO can be considered as a valid alternative to the conventional LM algorithm for online T2* mapping.
Dynamic QSM can be used to perform 4D mapping of contrast agent concentration in contrast-enhanced magnetic resonance imaging. The perfusion parameters derived from this 4D contrast agent concentration map were in good agreement with those obtained using arterial spin labeling.
Background: The purpose of this study was to evaluate breast tissue expanders with magnetic ports for safety in patients undergoing abdominal/pelvic magnetic resonance angiography before autologous breast reconstruction. Methods: Magnetic resonance angiography of the abdomen and pelvis at 1.5 T was performed in 71 patients in prone position with tissue expanders with magnetic ports labeled “MR Unsafe” from July of 2012 to May of 2014. Patients were monitored during magnetic resonance angiography for tissue expander–related symptoms, and the chest wall tissue adjacent to the tissue expander was examined for injury at the time of tissue expander removal for breast reconstruction. Retrospective review of these patients’ clinical records was performed. T2-weighted fast spin echo, steady-state free precession and gadolinium-enhanced spoiled gradient echo sequences were assessed for image artifacts. Results: No patient had tissue expander or magnetic port migration during the magnetic resonance examination and none reported pain during scanning. On tissue expander removal (71 patients, 112 implants), the surgeons reported no evidence of tissue damage, and there were no operative complications at those sites of breast reconstruction. Conclusion: Magnetic resonance angiography of the abdomen and pelvis in patients with certain breast tissue expanders containing magnetic ports can be performed safely at 1.5 T for pre–autologous flap breast reconstruction perforator vessel mapping. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.
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