Armstrong Ian S, Kelly Matthew D, Williams Heather A, Matthews Julian C
Nuclear Medicine, Central Manchester University Hospitals, Oxford Road, Manchester, UK.
Institute of Population Health, MAHSC, University of Manchester, Manchester, UK.
EJNMMI Phys. 2014 Dec;1(1):99. doi: 10.1186/s40658-014-0099-3. Epub 2014 Nov 30.
The use of maximum standardised uptake value (SUVmax) is commonplace in oncology positron emission tomography (PET). Point spread function (PSF) modelling and time-of-flight (TOF) reconstructions have a significant impact on SUVmax, presenting a challenge for centres with defined protocols for lesion classification based on SUVmax thresholds. This has perhaps led to the slow adoption of these reconstructions. This work evaluated the impact of PSF and/or TOF reconstructions on SUVmax, SUVpeak and total lesion glycolysis (TLG) under two different schemes of post-filtering.
Post-filters to match voxel variance or SUVmax were determined using a NEMA NU-2 phantom. Images from 68 consecutive lung cancer patients were reconstructed with the standard iterative algorithm along with TOF; PSF modelling - Siemens HD·PET (HD); and combined PSF modelling and TOF - Siemens ultraHD·PET (UHD) with the two post-filter sets. SUVmax, SUVpeak, TLG and signal-to-noise ratio of tumour relative to liver (SNR(T-L)) were measured in 74 lesions for each reconstruction. Relative differences in uptake measures were calculated, and the clinical impact of any changes was assessed using published guidelines and local practice.
When matching voxel variance, SUVmax increased substantially (mean increase +32% and +49% for HD and UHD, respectively), potentially impacting outcome in the majority of patients. Increases in SUVpeak were less notable (mean increase +17% and +23% for HD and UHD, respectively). Increases with TOF alone were far less for both measures. Mean changes to TLG were <10% for all algorithms for either set of post-filters. SNR(T-L) were greater than ordered subset expectation maximisation (OSEM) in all reconstructions using both post-filtering sets.
Matching image voxel variance with PSF and/or TOF reconstructions, particularly with PSF modelling and in small lesions, resulted in considerable increases in SUVmax, inhibiting the use of defined protocols for lesion classification based on SUVmax. However, reduced partial volume effects may increase lesion detectability. Matching SUVmax in phantoms translated well to patient studies for PSF reconstruction but less well with TOF, where a small positive bias was observed in patient images. Matching SUVmax significantly reduced voxel variance and potential variability of uptake measures. Finally, TLG may be less sensitive to reconstruction methods compared with either SUVmax or SUVpeak.
在肿瘤正电子发射断层扫描（PET）中，最大标准化摄取值（SUVmax）的应用十分普遍。点扩散函数（PSF）建模和飞行时间（TOF）重建对SUVmax有显著影响，这给那些基于SUVmax阈值制定病变分类明确方案的中心带来了挑战。这可能导致这些重建技术的采用速度较慢。本研究评估了在两种不同的后滤波方案下，PSF和/或TOF重建对SUVmax、SUV峰值和总病变糖酵解（TLG）的影响。
使用NEMA NU - 2体模确定匹配体素方差或SUVmax的后滤波器。对68例连续肺癌患者的图像采用标准迭代算法以及TOF进行重建；PSF建模——西门子HD·PET（HD）；以及将PSF建模和TOF相结合——西门子超高清·PET（UHD），并使用两组后滤波器。对每种重建方式下的74个病变测量SUVmax、SUV峰值、TLG以及肿瘤相对于肝脏的信噪比（SNR(T - L)）。计算摄取量测量值的相对差异，并根据已发表的指南和当地实践评估任何变化的临床影响。
当匹配体素方差时，SUVmax大幅增加（HD和UHD的平均增加分别为 +32% 和 +49%），这可能会影响大多数患者的治疗结果。SUV峰值的增加不太明显（HD和UHD的平均增加分别为 +17% 和 +23%）。仅使用TOF时，这两种测量值的增加幅度要小得多。对于两组后滤波器中的任何一种算法，TLG的平均变化均<10%。在使用两组后滤波器的所有重建中，SNR(T - L)均大于有序子集期望最大化（OSEM）。
将图像体素方差与PSF和/或TOF重建相匹配，特别是在PSF建模以及小病变中，会导致SUVmax显著增加，从而阻碍基于SUVmax的病变分类明确方案的使用。然而，部分容积效应的降低可能会提高病变的可检测性。在体模中匹配SUVmax在PSF重建的患者研究中效果良好，但在TOF中效果较差，在患者图像中观察到较小的正偏差。匹配SUVmax显著降低了体素方差和摄取量测量的潜在变异性。最后，与SUVmax或SUV峰值相比，TLG对重建方法可能不太敏感。
