Abstract
Fetal and neonatal MR imaging is increasingly used as a complementary diagnostic tool to sonography. MR imaging is an ideal technique for imaging fetuses and neonates because of the absence of ionizing radiation, the superior contrast of soft tissues compared with sonography, the availability of different contrast options, and the increased FOV. Motion in the normally mobile fetus and the unsettled, sleeping, or sedated neonate during a long acquisition will decrease image quality in the form of motion artifacts, hamper image interpretation, and often necessitate a repeat MR imaging to establish a diagnosis. This article reviews current techniques of motion compensation in fetal and neonatal MR imaging, including the following: 1) motion-prevention strategies (such as adequate patient preparation, patient coaching, and sedation, when required), 2) motion-artifacts minimization methods (such as fast imaging protocols, data undersampling, and motion-resistant sequences), and 3) motion-detection/correction schemes (such as navigators and self-navigated sequences, external motion-tracking devices, and postprocessing approaches) and their application in fetal and neonatal brain MR imaging. Additionally some background on the repertoire of motion of the fetal and neonatal patient and the resulting artifacts will be presented, as well as insights into future developments and emerging techniques of motion compensation.
Highlights
AND SCOPE In pediatric, neonatal, and fetal MR imaging examinations, image quality is governed mainly by the SNR and the presence of motion artifacts: the lower the SNR and the more prominent the motion artifacts, the lower the quality of MR images will be
These techniques are useful in minimizing motion artifacts in fetal and neonatal MR imaging, they are not always practical due to the extra time required for patient preparation and/or data acquisition
Real-time motion correction offers many added benefits: It requires no postprocessing because motion is monitored throughout the scan and the scanner gradients are simultaneously adjusted to “track” the object by using the knowledge of its motion, it can effectively correct for through-plane motion because it reduces spin-history effects, and the desired imaging volume is fully covered throughout the scan.[60]
Summary
AND SCOPE In pediatric, neonatal, and fetal MR imaging examinations, image quality is governed mainly by the SNR and the presence of motion artifacts: the lower the SNR and the more prominent the motion artifacts, the lower the quality of MR images will be. Clinical demand for MR imaging of both the neonatal and fetal brain is on the increase. Mild hypothermia has become standard practice for neonates with hypoxicischemic encephalopathy in many countries, and MR imaging is recommended to assess the extent of brain injury posttreatment.[8] ongoing studies[9] are assessing the potential role of brain MR imaging in the routine evaluation of the preterm infant at term-equivalent age. Numerous studies have shown that MR imaging provides complementary information to sonography scans of the fetal brain.[10,11,12] All these potential applications herald further demand for neonatal and fetal brain MR imaging, making motion compensation in the MR imaging of this population a priority
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