De Schepper Stijn, Gnanasegaran Gopinath, De Vos Wouter, Van de Casteele Elke, Dickson John C, Van den Wyngaert Tim
Department of Nuclear Medicine, Antwerp University Hospital, Drie Eikenstraat 655, Edegem, 2650, Belgium.
Faculty of Medicine and Health Sciences (MICA - IPPON), University of Antwerp, Wilrijk, Belgium.
EJNMMI Phys. 2024 Aug 23;11(1):74. doi: 10.1186/s40658-024-00676-6.
Unilateral condylar hyperplasia (UCH) of the mandible is a rare condition characterized by asymmetric growth of the mandibular condyles. Bone scintigraphy with SPECT(/CT) is commonly used to diagnose UCH and guide treatment. Still, varying results have been reported using the traditional threshold of 55%:45% in relative tracer uptake. While absolute quantification of uptake on SPECT/CT could improve results, optimal correction and reconstruction settings are currently unknown.
Three anthropomorphic phantoms representing UCH were developed from patient CT volumes and produced using 3D printing technology. Fillable spherical inserts of different sizes (Ø: 8-15 mm) were placed in the condylar positions representing symmetrical and asymmetrical distributions. Recovery coefficients were determined for SPECT/CT using various reconstruction corrections, including attenuation and scatter correction (ACSC), resolution modeling (RM), and partial volume correction (PVC) using phantom measurements. Uptake ratios between condyles and condyle to clivus were evaluated. Finally, the impact of these correction techniques on absolute activity and diagnostic accuracy was assessed in a retrospective patient cohort for the diagnostic threshold of 55%:45%.
The activity was only partially recovered in all spherical inserts (range: 22.5-64.9%). However, RM improved relative recovery by 20.2-62.3% compared to ACSC. In the symmetric phantoms, the 95% confidence interval (CI) of condyle ratios included the diagnostic threshold (57.6%:42.4%) for UCH when using ACSC potentially leading to false positives, but not for ACSCRM datasets. Partial volume corrections coefficients from the NEMA IQ phantom was positionally dependent, with improvements seen performing PVC using coefficients derived from anthropomorphic phantoms. Retrospective application in a patient cohort showed only a weak linear correlation (R²: 0.25-0.67) and large limits of agreement (9.6-12.5%) between different reconstructions. Up to 44% of patients were reclassified using the 55%:45% threshold. Using clinical outcome data, ACSCRM had highest sensitivity (91%; 95% CI 59-100%) and specificity (66%; 95% CI 47-81%), significantly improving specificity (P = 0.038).
Anthropomorphic phantoms were shown to be essential in determining optimal settings for acquisition, reconstruction, and analysis. SPECT/CT reconstructions with attenuation and scatter correction and resolution modeling are recommended and could improve specificity when using the 55%:45% threshold to assess condylar growth.
下颌骨单侧髁突增生（UCH）是一种罕见的病症，其特征为下颌髁突不对称生长。SPECT（/CT）骨闪烁显像常用于诊断UCH并指导治疗。然而，使用传统的55%:45%相对示踪剂摄取阈值报告的结果各异。虽然SPECT/CT上摄取的绝对定量可改善结果，但目前尚不清楚最佳校正和重建设置。
从患者CT容积数据开发出三个代表UCH的人体模型，并使用3D打印技术制作而成。将不同尺寸（直径：8 - 15毫米）的可填充球形插入物放置在髁突位置，分别代表对称和不对称分布。通过人体模型测量，使用各种重建校正方法，包括衰减和散射校正（ACSC）、分辨率建模（RM）和部分容积校正（PVC），确定SPECT/CT的恢复系数。评估髁突之间以及髁突与斜坡之间的摄取比率。最后，在一个回顾性患者队列中，针对55%:45%的诊断阈值，评估这些校正技术对绝对活性和诊断准确性的影响。
所有球形插入物中的活性仅部分恢复（范围：22.5 - 64.9%）。然而，与ACSC相比，RM使相对恢复提高了20.2 - 62.3%。在对称人体模型中，使用ACSC时，髁突比率的95%置信区间（CI）包括UCH的诊断阈值（57.6%:42.4%），这可能导致假阳性，但对于ACSC + RM数据集则不然。来自NEMA IQ人体模型的部分容积校正系数与位置有关，使用源自人体模型的系数进行PVC时可见改善。在患者队列中的回顾性应用显示，不同重建之间仅存在弱线性相关性（R²：0.25 - 0.67）和较大的一致性界限（9.6 - 12.5%）。使用55%:45%阈值时，高达44%的患者被重新分类。使用临床结局数据，ACSC + RM具有最高的敏感性（91%；95% CI 59 - 100%）和特异性（66%；95% CI 4
