Jentzen Walter, Görges Rainer, Freudenberg Lutz, Eising Ernst G, Müller Stefan P, Bockisch Andreas
Clinic for Nuclear Medicine, University of Duisburg/Essen, Germany.
Nucl Med Commun. 2008 Apr;29(4):398-404. doi: 10.1097/MNM.0b013e3282f81394.
The influence of various geometric factors on I uptake measurements for solitary thyroid nodule was systematically investigated to derive an approach, based on routinely performed ultrasound examinations, to correct for the effect of geometric variations.
The influence of size, shape, and position of a thyroid nodule, neck-to-detector distance and neck curvature on the uptake value was analyzed with a three-dimensional model. Uptake measurements using a tissue-equivalent neck phantom were carried out to verify the calculated correction factors and also to check the influence of scatter. Sonograms of 92 patients with solitary nodules were analyzed to correct for geometric variations.
The correction factors were independent of the size and shape of the nodule, and the activity distribution of the solitary nodules can be approximated by a point source. The correction factors were mainly determined by the nodular depth and by the accuracy of the neck-to-detector distance and were affected to a lesser extent by the lateral position of the nodule as well as the curvature of the neck. The effect of scatter can be neglected if the energy window largely excludes Compton scatter, as is the case in the I uptake measurement. The ultrasound-derived correction factors ranged from 0.85 to 1.25.
The proposed approach is capable of correcting for the geometric variation for a solitary nodule and can be easily applied in routine clinics. The accuracy of absorbed dose in radioiodine therapy can be improved in particular for nodules located well beneath the neck surface.
系统研究各种几何因素对孤立性甲状腺结节碘摄取测量的影响，以基于常规超声检查得出一种方法，用于校正几何变化的影响。
使用三维模型分析甲状腺结节的大小、形状和位置、颈部至探测器距离以及颈部曲率对摄取值的影响。使用组织等效颈部模型进行摄取测量，以验证计算出的校正因子，并检查散射的影响。分析92例孤立性结节患者的超声图像，以校正几何变化。
校正因子与结节的大小和形状无关，孤立性结节的活性分布可近似为点源。校正因子主要由结节深度以及颈部至探测器距离的准确性决定，结节的横向位置和颈部曲率对其影响较小。如果能量窗很大程度上排除了康普顿散射，如碘摄取测量的情况，则散射的影响可以忽略不计。超声得出的校正因子范围为0.85至1.25。
所提出的方法能够校正孤立性结节的几何变化，并且可以很容易地应用于常规临床。特别是对于位于颈部表面下方较深处的结节，放射性碘治疗中吸收剂量的准确性可以得到提高。
