
14-11SQUID Magnetometers
Magnetic elds from active electrical sources in the body can be measured passively and externally to
the body (i.e., noninvasively) by placing the magnetometer (actually rst- or second-order gradiometers)
in cl
ose
pr
oximity
to th
e
bo
dy’s
su
rface
. As me
ntioned,
th
e
us
e
of gr
adiometers
ca
n
al
low
me
asurements
to be ma
de
in un
shielded
en
vironments
at se
nsitivities
be
low
5 fT
/√Hz
. i
s
te
chnique
is ap
plicable
to
me
asurement
o
f
t
he
h
eart,
b
rain,
a
nd
s
keletal
m
uscles
.
14.5.1 Magnetoencephalography
e magnetic analog to electroencephalography (EEG), MEG, has the advantage of being (in the case of
depth electrodes) noninvasive ...