  Ultra-low field (ULF) MRI is a promising method for inexpensive medical
imaging with various additional advantages over conventional instruments such
as low weight, low power, portability, absence of artifacts from metals, and
high contrast. Anatomical ULF MRI has been successfully implemented with
SQUIDs, but SQUIDs have the drawback of cryogen requirement. Atomic
magnetometers have sensitivity comparable to SQUIDs and can be in principle
used for ULF MRI to replace SQUIDs. Unfortunately some problems exist due to
the sensitivity of atomic magnetometers to magnetic field and gradients. At low
frequency, noise is also substantial and a shielded room is needed for
improving sensitivity. In this paper, we show that at 85 kHz, the atomic
magnetometer can be used to obtain anatomical images. This is the first
demonstration of any use of atomic magnetometers for anatomical MRI. The
demonstrated resolution is 1.1x1.4 mm2 in about six minutes of acquisition with
SNR of 10. Some applications of the method are discussed. With several measures
it is also possible to increase sensitivity to reach resolution 1x1 mm2, which
is typical in medical imaging.
