Hander T A, Lancaster J L, Kopp D T, Lasher J C, Blumhardt R, Fox P T
Department of Radiology, University of Texas Health Science Center at San Antonio 78284, USA.
Med Phys. 1997 Feb;24(2):327-34. doi: 10.1118/1.597928.
An easy and rapid method for the measurement of the intrinsic spatial resolution of a gamma camera was developed. The measurement is based on the first and second statistical moments of regions of interest (ROIs) applied to bar phantom images. This leads to an estimate of the modulation transfer function (MTF) and the full-width-at-half-maximum (FWHM) of a line spread function (LSF). Bar phantom images were acquired using four large field-of-view (LFOV) gamma cameras (Scintronix, Picker, Searle, Siemens). The following factors important for routine measurements of gamma camera resolution with this method were tested: ROI placement and shape, phantom orientation, spatial sampling, and procedural consistency. A 0.2% coefficient of variation (CV) between repeat measurements of MTF was observed for a circular ROI. The CVs of less than 2% were observed for measured MTF values for bar orientations ranging from -10 degrees to +10 degrees with respect to the x and y axes of the camera acquisition matrix. A 256 x 256 matrix (1.6 mm pixel spacing) was judged sufficient for routine measurements, giving an estimate of the FWHM to within 0.1 mm of manufacturer-specified values (3% difference). Under simulated clinical conditions, the variation in measurements attributable to procedural effects yielded a CV of less than 2% in newer generation cameras. The moments method for determining MTF correlated well with a peak-valley method, with an average difference of 0.03 across the range of spatial frequencies tested (0.11-0.17 line pairs/mm, corresponding to 4.5-3.0 mm bars). When compared with the NEMA method for measuring intrinsic spatial resolution, the moments method was found to be within 4% of the expected FWHM.
开发了一种用于测量γ相机固有空间分辨率的简便快速方法。该测量基于应用于条形模体图像的感兴趣区域（ROI）的一阶和二阶统计矩。这可以估计调制传递函数（MTF）和线扩展函数（LSF）的半高全宽（FWHM）。使用四台大视野（LFOV）γ相机（Scintronix、Picker、Searle、西门子）采集条形模体图像。测试了该方法在γ相机分辨率常规测量中重要的以下因素：ROI放置和形状、模体方向、空间采样和操作一致性。对于圆形ROI，MTF重复测量之间观察到0.2%的变异系数（CV）。对于相对于相机采集矩阵的x轴和y轴，条形方向在-10度至+10度范围内测量的MTF值，观察到CV小于2%。判断256×256矩阵（像素间距1.6毫米）足以进行常规测量，给出的FWHM估计值与制造商指定值相差在0.1毫米以内（差异3%）。在模拟临床条件下，新一代相机中由于操作影响导致的测量变化产生的CV小于2%。确定MTF的矩量法与峰谷法相关性良好，在测试的空间频率范围内（0.11 - 0.17线对/毫米，对应于4.5 - 3.0毫米条形）平均差异为0.03。与NEMA测量固有空间分辨率的方法相比，矩量法的结果在预期FWHM的4%以内。
