求英譯中,不要機(jī)譯的.
Ittakes only a tiny magnetic field to see clear through a person’s head,a new study shows.A method called ultra-low field magneticresonance imaging (MRI) has captured its first,blurry shots of a human brain,revealing activity as well as structure.
MRI scanners image the human body by detecting how hydrogenatoms respond to magnetic fields.Theytypically require fields of a few tesla—about 10,000 to 100,000 times strongerthan the Earth’s magnetic field.The powerful magnets necessary make scannerspricey and also dangerous for people with metal implants.
Thenew device hits a sample with a 30 millitesla magnetic field,about 100 timesweaker than is normally used in MRI.The device then uses a 46 microteslamagnetic field—about the same as the Earth’s magnetic field—to capture imagesof the sample.
The first target for the device wasthe head of lead researcher Vadim Zotev of Los Alamos
National Laboratory in New Mexico,US.
“Thecost of MRI can be reduced dramatically,” Zotev says.The new set-up usesseveral ultra-sensitive sensors called superconducting quantum interferencedevices (SQUIDs),which have to be kept at very low temperatures.“The mostexpensive part of our system is the liquid helium cryostat,which costs about$20,000,” Zotev adds.