Quantitative imaging of iodine-131 distributions in brain tumors with pinhole SPECT: a phantom study.
Quantitative imaging of iodine-131 distributions in brain tumors with pinhole SPECT: a phantom study.
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发表时间：
1998-05
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通讯作者：
Mark F. Smith;D. Gilland;R. Coleman;R. Jaszczak
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作者：
Mark F. Smith;D. Gilland;R. Coleman;R. Jaszczak
开发了一种定量成像131 I在脑肿瘤中分布的方法，该方法通过瘤内给药活性，并使用脑肿瘤模型的针孔SPECT进行研究。方法针孔SPECT的灵敏度和分辨率进行了表征，使用131 I点源采集高分辨率铅（1.4 mm直径孔径）和钨（1.0 mm直径孔径）针孔插入。SPECT扫描是从充满水的圆柱体中的脑肿瘤模型获得的。肿瘤模型由填充有131 I溶液的球体组成，以模拟放射性标记的单克隆抗体的瘤内给药。两个球体分别为20.5和97 ml，另外两个同心球体模拟了具有高活性壳（71.5 ml）和低活性核（21 ml）的肿瘤。准直器焦距为16 cm，针孔到旋转中心的距离为13 cm。滤波反投影重建算法结合散射和衰减补偿。SPECT肿瘤活性和浓度使用来自参考点源扫描的比例因子来估计。结果：系统对旋转中心点源的灵敏度分别为28.4cts/sec（-1）MBq（-1）（铅芯）和13.6cts/sec（-1）MBq（-1）（钨芯）。旋转中心的SPECT分辨率（FWHM）为8.1-11.9 mm（电极导线）和6.7-10.3 mm（钨）。SPECT的总肿瘤活性估计值在真实活性的17%以内。对于20.5 ml球体，小感兴趣区域（ROI）中的SPECT活性浓度估计值平均为-20%，97 ml球体为-11%，壳为-39%，壳-芯体模的芯为+20%。活动溢出由于有限的空间分辨率和系统响应函数的尾部偏置的估计。由于更好的分辨率，使用钨插入物（2.3）比使用铅插入物（1.9）更好地估计了4.1的壳-核活性浓度比。结论针孔SPECT是一种很有前途的显像和定量脑肿瘤大小区域总131 I活度的技术。相对误差较大的活动浓度估计在小ROI比总活动估计。
UNLABELLED A method of quantitatively imaging 131I distributions in brain tumors from intratumoral administration of activity was developed and investigated using pinhole SPECT of brain tumor phantoms. METHODS Pinhole SPECT sensitivity and resolution were characterized using 131I point-source acquisitions with high-resolution lead (1.4-mm diameter aperture) and tungsten (1.0-mm diameter aperture) pinhole inserts. SPECT scans were obtained from brain tumor phantoms in a water-filled cylinder. The tumor phantoms consisted of spheres filled with an 131I solution to model intratumoral administration of radiolabeled monoclonal antibodies. Two spheres were 20.5 and 97 ml, and two other concentric spheres modeled a tumor with a high-activity shell (71.5 ml) and a low-activity core (21 ml). The collimator focal length was 16 cm and the distance from the pinhole to the center of rotation was 13 cm. The filtered backprojection reconstruction algorithm incorporated scatter and attenuation compensation. SPECT tumor activities and concentrations were estimated using scaling factors from reference point-source scans. RESULTS System sensitivities for point sources at the center of rotation were 28.4 cts/sec(-1) MBq(-1) (lead insert) and 13.6 cts/sec(-1) MBq(-1) (tungsten insert). SPECT resolutions (FWHM) at the center of rotation were 8.1-11.9 mm (lead) and 6.7-10.3 mm (tungsten). Total tumor activity estimates from SPECT were within 17% of the true activities. SPECT activity concentration estimates in small regions of interest (ROIs) averaged -20% for the 20.5-ml sphere, -11% for the 97-ml sphere, -39% for the shell and +20% for the core of the shell-core phantom. Activity spillover due to limited spatial resolution and the tails of the system response functions biased the estimates. The shell-to-core activity concentration ratio of 4.1 was better estimated with the tungsten insert (2.3) than with the lead insert (1.9) due to better resolution. CONCLUSION Pinhole SPECT is a promising technique for imaging and quantifying total 131I activity in regions the size of brain tumors. Relative errors were greater for activity concentration estimates in small ROIs than for total activity estimates.