Sains Malaysiana 46(1)(2017): 67–74

http://dx.doi.org/10.17576/jsm-2017-4601-09

Determination of Optimum Combination of Voxel Size and b-value for Brain Diffusion Tensor Imaging

(Penentuan Gabungan Optimum Saiz Voksel dan Nilai-b untuk Pengimejan Tensor Difusi Otak)

NUR HARTINI MOHD TAIB¹*, WAN AHMAD KAMIL WAN ABDULLAH¹, IBRAHIM LUTFI SHUAIB², ENRICO MAGOSSO² & SUZANA MAT ISA²

¹Department of Radiology, School of Medical Sciences, Universiti Sains Malaysia

Kubang Kerian, Kelantan Darul Naim, Malaysia

²Advanced Medical and Dental Institute, Universiti Sains Malaysia, Kepala Batas, Pulau Pinang

Malaysia

Diserahkan: 20 Mei 2014/Diterima: 8 April 2016

ABSTRACT

Optimum combination of voxel size resolution and b-value for whole brain imaging has been determined. Data images were acquired using a 1.5T magnetic resonance imaging (MRI) system (GE Signa HDxt). Diffusion tensor imaging (DTI) scan was performed on phantom and a human volunteer. Six protocols which consist of various combination of voxel size and b-value were evaluated. Measurement of signal-to-noise ratio (SNR) and DTI parameter indices were carried out for both phantom and in-vivo studies. Due consideration was given to a combination of parameters yielding sufficient SNR with DTI values comparable to those obtained from previous reported studies. For the phantom study, SNR ≥ 20 was found in all of the protocols except for a combination of voxel size of 2.0 × 2.0 × 2.0 mm³ with b-value of 1200 s/mm² (V2.0 B1200) and that of voxel size of 2.0 × 2.0 × 2.0 mm³ with b-value of 1000 s/mm² (V2.0 B1000). For in-vivo study, all protocols presented SNR > 20. It was found that a combination of voxel size of 2.5 × 2.5 × 2.5 mm3 with b-value of 1000 s/mm² (V2.5 B1000) and that of voxel size of 2.5 × 2.5 × 2.5 mm³ with b-value of 700 s/mm² (V2.5 B700) displayed the most comparable ADC and FA values with references. In terms of anatomic coverage, V2.5 B700 was found better than V2.5 B1000 as it assures coverage of the whole brain. In conclusion, a combination of voxel size of 2.5 × 2.5 × 2.5 mm3 with b-value of 700 s/mm² was considered as optimum parameters for brain DTI.

Keywords: Brain imaging; b-value; diffusion tensor imaging; optimization; voxel size

ABSTRAK

Gabungan optimum peleraian saiz voksel dan nilai-b untuk pengimejan seluruh otak telah ditentukan. Data imej telah diperoleh menggunakan sistem pengimejan resonans magnet (MRI) 1.5T (GE Signa HDxt). Imbasan pengimejan tensor difusi (DTI) telah dilakukan ke atas fantom dan seorang sukarelawan. Enam protokol yang terdiri daripada pelbagai gabungan saiz voksel dan nilai-b telah dinilai. Pengukuran nisbah isyarat-hingar (SNR) dan parameter indeks DTI telah dilakukan untuk kajian fantom dan in-vivo. Pertimbangan yang sewajarnya telah diberikan kepada gabungan parameter yang menghasilkan SNR mencukupi dan nilai DTI setara dengan yang diperoleh daripada kajian terdahulu. Untuk kajian fantom, didapati SNR ≥ 20 bagi semua protokol kecuali gabungan saiz voksel 2.0 × 2.0 × 2.0 mm³ dengan nilai-b 1200 s/mm² (V2.0 B1200) dan gabungan saiz voksel 2.0 × 2.0 × 2.0 mm3 dengan nilai-b 1000 s/mm² (V2.0 B1000). Bagi kajian in-vivo, semua protokol menunjukkan SNR > 20. Didapati gabungan saiz voksel 2.5 × 2.5 × 2.5 mm³ dengan nilai-b 1000 s/mm² (V2.5 B1000) dan saiz voksel 2.5 × 2.5 × 2.5 mm³ dengan nilai-b 700 s/mm² (V2.5 B700) telah mempamerkan nilai ADC dan FA paling setara dengan rujukan. Daripada segi liputan anatomi, didapati V2.5 B700 lebih baik daripada V2.5 B1000 kerana ia menjamin liputan seluruh otak. Kesimpulannya, gabungan saiz voxel 2.5 × 2.5 × 2.5 mm³ dengan nilai-b 700 s/mm² dianggap sebagai parameter yang optimum untuk DTI otak.

Kata kunci: Nilai-b; pengimejan otak; pengimejan tensor difusi; pengoptimuman; saiz voksel

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*Pengarang untuk surat-menyurat; email: nhartini@usm.my