Hutton B F, Osiecki A, Meikle S R
Department of Medical Physics, Westmead Hospital, Sydney, Australia.
Eur J Nucl Med. 1996 Oct;23(10):1300-8. doi: 10.1007/BF01367584.
Meaningful comparison of single-photon emission tomographic (SPET) reconstructions for data acquired over 180 degrees or 360 degrees can only be performed if both attenuation and scatter correction are applied. Convolution subtraction has appeal as a practical method for scatter correction; however, it is limited to data acquired over 360 degrees. A new algorithm is proposed which can be applied equally well to data acquired over 180 degrees or 360 degrees. The method involves estimating scatter based on knowledge of reconstructed transmission data in combination with a reconstructed estimate of the activity distribution, obtained using attenuation correction with broad beam attenuation coefficients. Processing is implemented for planes of activity parallel to the projection images for which a simplified model for the scatter distribution may be applied, based on the measured attenuation. The appropriate broad beam (effective) attenuation coefficients were determined by considering the scatter buildup equation. It was demonstrated that narrow beam attenuation coefficients should be scaled by 0.75 and 0.65 to provide broad beam attenuation coefficients for technetium-99m and thallium-201 respectively. Using a thorax phantom, quantitative accuracy of the new algorithm was compared with conventional transmission-based convolution subtraction (TDCS) for 360 degrees data. Similar heart to lung contrasts were achieved and correction of 180 degrees data yielded a 10.4% error for cardiac activity compared to 5.2% for TDCS. Contrast for myocardium to ventricular cavity was similarly good for scatter-corrected 180 degrees and 360 degrees data, in contrast to attenuation-corrected data, where contrast was significantly reduced. The new algorithm provides a practical method for correction of scatter applicable to 180 degrees myocardial SPET.
只有在同时应用衰减校正和散射校正的情况下，才能对180度或360度采集的数据进行单光子发射断层扫描（SPET）重建的有意义比较。卷积减法作为一种散射校正的实用方法具有吸引力；然而，它仅限于360度采集的数据。提出了一种新算法，该算法可同样适用于180度或360度采集的数据。该方法涉及基于重建的透射数据的知识，并结合使用宽束衰减系数进行衰减校正获得的活度分布的重建估计来估计散射。基于测量的衰减，对与投影图像平行的活动平面进行处理，对于这些平面可以应用散射分布的简化模型。通过考虑散射积累方程确定了合适的宽束（有效）衰减系数。结果表明，窄束衰减系数应分别乘以0.75和0.65，以提供锝-99m和铊-201的宽束衰减系数。使用胸部模型，将新算法的定量准确性与传统的基于透射的卷积减法（TDCS）用于360度数据的情况进行了比较。获得了相似的心脏与肺部对比度，180度数据校正后心脏活动的误差为10.4%，而TDCS为5.2%。与衰减校正数据相比，散射校正的180度和360度数据中心肌与心室腔的对比度同样良好，在衰减校正数据中对比度显著降低。新算法为适用于180度心肌SPET的散射校正提供了一种实用方法。
