Journal List > Prog Med Phys > v.24(3) > 1098384

Park, Yu, Kim, Lee, and Kim: A Low-Dose High-Resolution SPECT System with CdTe for Small-Animal Imaging Applications: A GATE Simulation Study

Abstract

Dedicated single-photon emission computed tomography (SPECT) systems based on pixelated semiconductors are being developed for studying small animal models of human disease. To clarify the possibility of using a SPECT system with CdTe for a high resolution low-dose small animal imaging, we compared the quality of reconstructed images from pixelated CdTe detector to those from a small SPECT system with NaI(Tl). The CdTe detector was 44.8×44.8 mm and the pixels were 0.35×0.35×5 mm. The intrinsic resolution of the detector was 0.35 mm, which is equal to the pixel size. GATE simulations were performed to assess the image quality of both SPECT systems. The spatial resolutions and sensitivities for both systems were evaluated using a 10 MBq 99mTc point source. The quantitative comparison with different injected dose was performed using a voxelized MOBY phantom, and the absorbed doses for each organ were evaluated. The spatial resolution of the SPECT with NaI(Tl) was about 1.54 mm FWHM, while that of the SPECT with a CdTe detector was about 1.32 mm FWHM at 30 mm. The sensitivity of NaI(Tl) based SPECT was 83 cps/MBq, while that of the CdTe detector based SPECT was 116 cps/MBq at 30 mm. The image statistics were evaluated by calculating the CNR of the image from both systems. When the injected activity for the striatum in the mouse brain was 160 Bq/voxel, the CNR of CdTe based SPECT was 2.30 while that of NaI(Tl) based SPECT was 1.85. The CNR of SPECT with CdTe was overall higher than that of the NaI(Tl) based SPECT. In addition, the absorbed dose was higher from SPECT with CdTe than those from NaI(Tl) based SPECT to acquire the same quantitative values. Our simulation results indicated that the SPECT with CdTe detector showed overall high performance compared to the SPECT with NaI(Tl). Even though the validation study is needed, the SPECT system with CdTe detector appeared to be feasible for high resolution low-dose small animal imaging.

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Fig. 1.
CdTe 반도체 검출기(model PID-350, AJAT, Finland) (a), 소동물용 평행다공형 콜리메이터 (b), 평행다공형 콜리메이터의 구조 (c).
pmp-24-162f1.tif
Fig. 2.
Ultra-Micro Hot spot 팬텀 (a), 팬텀의 횡단면 (b), 팬텀의 시뮬레이션 (c).
pmp-24-162f2.tif
Fig. 3.
MOBY 팬텀.
pmp-24-162f3.tif
Fig. 4.
MOBY brain 팬텀 (a), Mouse brain SPECT획득을 위한 GATE 시뮬 레이션 (b).
pmp-24-162f4.tif
Fig. 5.
DoseActor tool을 사용한 MOBY 팬텀의 흡수선량을 계산 획득 과정.
pmp-24-162f5.tif
Fig. 6.
검출기 종류에 따른 두 SPECT 시스템의 공간 분해능 비교.
pmp-24-162f6.tif
Fig. 7.
검출기 종류에 따른 두 SPECT 시스템의 민감도 비교.
pmp-24-162f7.tif
Fig. 8.
CdTe-based SPECT (a), NaI(Tl)-based SPECT (b)에서 획 득한 Ultra-Micro Hot spot 팬텀의 재구성 영상.
pmp-24-162f8.tif
Fig. 9.
Ultra-Micro Hot spot 팬텀의 재구성 영상의 프로파일.
pmp-24-162f9.tif
Fig. 10.
CdTe-based SPECT (a), NaI(Tl)-based SPECT (b)의 Mouse brain 재구성 영상.
pmp-24-162f10.tif
Fig. 11.
Striatum의 흡수선량에 따른 두 SPECT 시스템의 CNR 비교.
pmp-24-162f11.tif
Table 1.
주입 방사선량에 따른 흡수선량 및 두 시스템에서의 CNR.
Injected activity (Bq/voxel) Absorbed dose for striatum (mGy) CNR of CdTe detector CNR of NaI detector
40 1.29 1.76 1.42
80 2.45 1.98 1.66
120 3.75 2.04 1.79
160 5.04 2.30 1.85
200 6.57 2.59 2.00
240 7.47 2.63 2.03
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