Jin Yuan, Kong Huafu, Stodilka Rob Z, Wells R Glenn, Zabel Pamela, Merrifield Peter A, Sykes Jane, Prato Frank S
Imaging Program, Lawson Health Research Institute, and Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
Phys Med Biol. 2005 Oct 7;50(19):4445-55. doi: 10.1088/0031-9155/50/19/001. Epub 2005 Sep 13.
In this work, we determined the minimum number of detectable 111In-tropolone-labelled bone-marrow-derived stem cells from the maximum activity per cell which did not affect viability, proliferation and differentiation, and the minimum detectable activity (MDA) of 111In by SPECT. Canine bone marrow mesenchymal cells were isolated, cultured and expanded. A number of samples, each containing 5x10(6) cells, were labelled with 111In-tropolone from 0.1 to 18 MBq, and cell viability was measured afterwards for each sample for 2 weeks. To determine the MDA, the anthropomorphic torso phantom (DataSpectrum Corporation, Hillsborough, NC) was used. A point source of 202 kBq 111In was placed on the surface of the heart compartment, and the phantom and all compartments were then filled with water. Three 111In SPECT scans (duration: 16, 32 and 64 min; parameters: 128x128 matrix with 128 projections over 360 degrees) were acquired every three days until the 111In radioactivity decayed to undetectable quantities. 111In SPECT images were reconstructed using OSEM with and without background, scatter or attenuation corrections. Contrast-to-noise ratio (CNR) in the reconstructed image was calculated, and MDA was set equal to the 111In activity corresponding to a CNR of 4. The cells had 100% viability when incubated with no more than 0.9 MBq of 111In (80% labelling efficiency), which corresponded to 0.14 Bq per cell. Background correction improved the detection limits for 111In-tropolone-labelled cells. The MDAs for 16, 32 and 64 min scans with background correction were observed to be 1.4 kBq, 700 Bq and 400 Bq, which implies that, in the case where the location of the transplantation is known and fixed, as few as 10,000, 5000 and 2900 cells respectively can be detected.
在本研究中，我们根据不影响细胞活力、增殖和分化的单个细胞最大活性，确定了可检测到的111铟-托酚酮标记的骨髓源干细胞的最小数量，以及通过单光子发射计算机断层扫描（SPECT）检测111铟的最小可检测活性（MDA）。分离、培养并扩增犬骨髓间充质细胞。将若干样本（每个样本含5×10⁶个细胞）用0.1至18MBq的111铟-托酚酮进行标记，之后对每个样本的细胞活力进行为期2周的检测。为确定MDA，使用了人体躯干模型（DataSpectrum公司，北卡罗来纳州希尔斯伯勒）。将一个202kBq的111铟点源置于心脏区域表面，然后向模型及所有区域注满水。每三天进行三次111铟SPECT扫描（持续时间：16、32和64分钟；参数：128×128矩阵，360度有128个投影），直至111铟放射性衰减至无法检测的量。使用有序子集期望最大化（OSEM）算法对111铟SPECT图像进行重建，重建过程有无背景、散射或衰减校正。计算重建图像中的对比度噪声比（CNR），将MDA设定为对应CNR为4时的111铟活性。当与不超过0.9MBq的111铟（标记效率80%）孵育时，细胞活力为100%，这相当于每个细胞0.14Bq。背景校正提高了对111铟-托酚酮标记细胞的检测限。经背景校正后，16、32和64分钟扫描的MDA分别为1.4kBq、700Bq和400Bq，这意味着在移植位置已知且固定的情况下，分别可检测到低至10000、5000和2900个细胞。
