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Sains Malaysiana 45(10)(2016): 1525–1530
Optimization of Number of Scans for a Sparse
Temporal Sampling (STS) Functional Magnetic Resonance Imaging
(fMRI) (Pengoptimuman
Bilangan Imbasan
untuk Pengimejan Resonans Magnet Kefungsian (fMRI)
Pensampelan Temporal Berjarak
(STS)) AHMAD NAZLIM
YUSOFF1*,
KHAIRIAH
ABDUL
HAMID2,
HAMDI
HAMZAH3,
MAZLYFARINA
MOHAMAD1,
SITI
ZAMRATOL-MAI
SARAH
MUKARI4,5 & WAN
AHMAD
KAMIL
WAN
ABDULLAH6 1Diagnostic Imaging & Radiotherapy
Program, School of Diagnostic and Applied Health Sciences Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Jalan
Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia 2Medical Imaging Department, School
of Health Sciences,
KPJ University College Lot PT 17010, Persiaran
Seriemas, Kota Seriemas,
71800 Nilai, Negeri
Sembilan, Malaysia 3KPJ Ipoh Specialist Hospital, 26,
Jalan Raja Dihilir,
30350 Ipoh, Perak Darul Ridzuan Malaysia 4Audiology Program, School of Rehabilitation
Sciences, Faculty of Health Sciences Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia 5Institute of Ear, Hearing and Speech, Faculty of Health Science,
Universiti Kebangsaan Malaysia, Jalan
Temerloh, 53200 Kuala Lumpur, Malaysia 6Universiti Sains
Malaysia, 16150 Kubang Kerian,
Kelantan Darul Naim, Malaysia Diserahkan: 8 Oktober
2015/Diterima: 19 Februari
2016 ABSTRACT High sensitivity signal detection
for a sparse temporal sampling (STS)
functional magnetic resonance imaging (fMRI) is compensated by the increase
in the number of scans (Ns) and consequently the scan time.
A long scan time would result in fatigue and restlessness in
participants, while a short scan time is undesirable for an
STS-fMRI
due to insufficient Ns for averaging. The purpose of this
study was to determine the Ns practically sufficient for a
sparse fMRI study. Eighteen participants were presented with white
noise during a sparse fMRI scan. The height extent of
activation was determined via t
statistics and region of interest (ROI) based percentage of signal
change (PSC). The t statistics and PSC for
Heschl’s gyrus (HG)
and superior temporal gyrus (STG) during which the participants
listened to the white noise were calculated for different number
of scans which were 6, 12, 18, 24, 30 and 36. The t statistics
and PSC
values calculated for the bilateral HG and STG qualitatively
indicated a minimal change over Ns = 12 to 36. Both ROIs
showed a consistent common right lateralization of activation
for all Ns,
indicating the right-hemispheric dominance of auditory cortex
in processing white noise stimulus. It was proposed that for
a sparse fMRI study,
Ns
may practically fall between 12 and 36. Keywords: Auditory cortex;
functional MRI; percentage of signal change; SPM;
t statistics ABSTRAK Pengesanan isyarat berkepekaan
tinggi bagi
pengimejan resonans magnet kefungsian (fMRI) pensampelan
temporal berjarak (STS)
dipampas oleh peningkatan
bilangan imbasan
(Ns)
dan seterusnya
masa imbasan. Masa imbasan yang lama boleh mengakibatkan kelesuan dan resah gelisah
dalam diri
pesakit, manakala masa imbasan yang singkat tidak diterima dalam STS-fMRI disebabkan bilangan Ns yang
tidak mencukupi
untuk pemurataan. Tujuan kajian ini adalah
untuk menentukan
Ns yang
secara praktiknya
mencukupi untuk kajian fMRI berjarak.
Lapan
belas peserta kajian
diperdengarkan bunyi
hingar putih semasa
imbasan fMRI berjarak.
Takat
tinggi pengaktifan ditentukan melalui statistik t dan peratus
perubahan isyarat
(PSC)
berasaskan kawasan
diminati (ROI). Statistik t dan PSC untuk girus Heschl (HG)
dan girus temporal superior (STG)
semasa peserta
kajian mendengar hingar putih dihitung
untuk bilangan
imbasan berbeza iaitu 6, 12, 18, 24, 30 dan 36.
Statistik t
dan PSC yang dihitung
untuk HG dan
STG
bilateral secara kualitatif
menunjukkan perubahan
minimum merentasi Ns =
12 ke 36. Kedua-dua ROI memperlihatkan pengaktifan lateralisasi kanan biasa yang tekal untuk semua
Ns,
menunjukkan kedominanan
hemisfera kanan bagi korteks auditori
dalam memproses
stimulus hingar putih. Dicadangkan bahawa untuk kajian
fMRI
berjarak, Ns secara praktiknya boleh mengambil nilai antara 12 dan 36. Kata kunci: Korteks
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