Papanastasiou Emmanouil, Moralidis Efstratios, Siountas Anastasios
Department of Medical Physics, AHEPA University Hospital, Aristotle University Medical School, Thessaloniki, Greece.
Hell J Nucl Med. 2017 May-Aug;20(2):154-159.
In cardiac I-123 (I) imaging downscatter from high energy emissions degrades the image and introduces distortion of semi-quantitative analysis when using a low energy collimator. The effect of a triple energy window (TEW) scatter correction technique, using windows immediately above and below the principal window centered on 159keV, was examined.
A hemispherical cardiac phantom was inserted into a cylindrical phantom and both were filled with radioactive I water solutions. Phantoms were submitted to planar and tomographic scintigraphy under various acquisition and processing conditions, including the use of medium energy (ME) and low energy (LE) collimation.
In planar imaging, there was a distance dependent count loss with the LEHR collimator which was partly restored with TEW correction. There was minimal dependence of count rate with distance in using ME collimation. Conversely, the heart to background (H/B) ratio increased with increasing distance with the LEHR collimator, but in applying the TEW correction that ratio paralleled the minimally affected values obtained with the ME collimation. In tomographic imaging the acquired H/B ratio was lower with LE collimation alone, in comparison to the ME collimator, but it was raised significantly when applying the TEW scatter correction. Quantitative measurements also depended on the background method and the reconstruction algorithm applied.
In cardiac I imaging with a LE collimator the use of TEW scatter correction provides a semi-quantitative assessment comparable to that attained with ME collimation and may moderate inter-institutional inconsistencies.
在心脏碘 - 123（I）成像中，当使用低能准直器时，高能发射产生的散射会降低图像质量，并导致半定量分析出现失真。研究了一种三能窗（TEW）散射校正技术的效果，该技术使用以159keV为中心的主能窗上方和下方紧邻的能窗。
将半球形心脏模型插入圆柱形模型中，两者均填充放射性碘水溶液。在各种采集和处理条件下，包括使用中能（ME）和低能（LE）准直，对模型进行平面和断层闪烁显像。
在平面成像中，使用低能高分辨率（LEHR）准直器时存在与距离相关的计数损失，通过TEW校正可部分恢复。使用ME准直时，计数率与距离的相关性最小。相反，使用LEHR准直器时，心脏与本底（H/B）比值随距离增加而升高，但应用TEW校正后，该比值与ME准直时受影响最小的值相当。在断层成像中，与ME准直器相比，单独使用LE准直时采集到的H/B比值较低，但应用TEW散射校正后显著提高。定量测量还取决于本底方法和应用的重建算法。
在使用LE准直器进行心脏碘成像时，使用TEW散射校正可提供与ME准直相当的半定量评估，并可能减少机构间的差异。
