<
h4 class=""
h4"">Backg
roundh4>Repetitive t
ransc
ranial magnetic stimulation (
rTMS) is used to t
reat neu
rological and psyc
hiat
ric diso
rders suc
h as
dep
ression and addiction amongst ot
he
rs. Neu
ro-imaging by means of SPECT is a non-invasive manne
r of evaluating
regional ce
reb
ral blood flow (
rCBF) c
hanges, w
hic
h a
re assumed to
reflect c
hanges in neu
ral activity.<
h4 class=""
h4"">Objectiveh4>
rCBF changes induced by rTMS are evaluated by comparing stimulation on/off in different stimulation paradigms using microSPECT of the rat brain.<h4 class=""h4"">Methodsh4>
Rats (n?=?6) were injected with 10?mCi of 99mTc-HMPAO during application of two rTMS paradigms (1?Hz and 10?Hz, 1430?A at each wing of a 20?mm figure-of-eight coil) and sham. SPM- and VOI-based analysis was performed.<h4 class=""h4"">Resultsh4>
rTMS caused widespread significant hypoperfusion throughout the entire rat brain. Differences in spatial extent and intensity of hypoperfusion were observed between both stimulation paradigms: 1?Hz caused significant hypoperfusion (P?<?0.05) in 11.9 % of rat brain volume while 10?Hz caused this?in?23.5 % ; the minimal t-value induced by 1?Hz was??24.77 while this was??17.98 due to 10?Hz. Maximal?percentage of hypoperfused volume due to 1?Hz and 10?Hz was reached at tissue experiencing 0.03-0.15?V/m.<h4 class=""h4"">Conclusionh4>
High-frequency (10?Hz) stimulation causes more widespread hypoperfusion, while 1?Hz induces more pronounced hypoperfusion. The effect of rTMS is highly dependent on the electric field strength in the brain tissue induced by the TMS coil. This innovative imaging approach can be used as a fast screening tool in quantifying and evaluating the effect of various stimulation paradigms and coil designs for TMS and offers a means for research and development.
