Mortazi Aliasghar, Udupa Jayaram K, Hosseini Mahdie, Tong Yubing, Torigian Drew A
Medical Image Processing Group, Department of Radiology, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA, 19104, USA.
Eur J Nucl Med Mol Imaging. 2025 Jun 23. doi: 10.1007/s00259-025-07423-8.
Quantification of skin diseases such as cutaneous lymphoma or psoriasis is important for pretreatment planning and response assessment. Currently, this quantification relies on clinical assessments, which are cumbersome, error-prone, and subject to inter-reader variability. FDG-PET/CT is a widely used molecular imaging technique for non-invasive detection and quantification of metabolically active disorders, providing biomarkers of disease extent, severity, and therapeutic response. However, skin disease quantification from PET/CT images remains challenging, error-prone, and labor-intensive.
We proposed a novel comprehensive methodology called virtual Cutaneous Area Severity Index (vCASI) to quantitatively assess the extent and severity of metabolically active skin disease from FDG-PET/CT images. Firstly, we used an automated body region localization method, followed by a standardization technique for PET images to reduce interscan measurement variability. Then, we generated skin shell PET images and developed a standardized Maximum Intensity Projection (MIP) rendering technique to enable reproducible 3D visualization of the skin with the disease. Finally, we introduced and validated a new quantitative scoring system (vCASI score) to measure the extent and severity of skin disease via these renderings.
Correlations between vCASI scores and reference standard ground-truth assessments increased following the standardization of PET images, further improved with the use of adjusted mean of maximum percentile intensity values as the reference point for MIP rendering, and reached as high as 0.605. Additionally, correlations between repeated vCASI score assessments for the torso, thorax, abdomen, and pelvis exceeded 0.85, demonstrating high repeatability.
The vCASI methodology allows for accurate and reproducible quantitative assessment of the extent and severity of metabolically active skin diseases, such as cutaneous lymphoma and psoriasis, from FDG-PET/CT images. It addresses the challenges related to body region localization, non-standardness of PET images, robust visualization, and standardized display of PET images to detect and quantify skin disease. Additionally, it overcomes the lack of a practical and validated scoring system for quantifying skin disease on PET images. We demonstrated that the vCASI scoring system has high repeatability and good accuracy, and is optimized by the proposed methodology.
对皮肤淋巴瘤或银屑病等皮肤疾病进行量化对于治疗前规划和疗效评估至关重要。目前，这种量化依赖于临床评估，而临床评估繁琐、容易出错且存在阅片者间的差异。氟代脱氧葡萄糖正电子发射断层显像/计算机断层扫描（FDG-PET/CT）是一种广泛应用的分子成像技术，用于非侵入性检测和量化代谢活跃性疾病，可提供疾病范围、严重程度和治疗反应的生物标志物。然而，从PET/CT图像中对皮肤疾病进行量化仍然具有挑战性，容易出错且劳动强度大。
我们提出了一种名为虚拟皮肤面积严重程度指数（vCASI）的新型综合方法，用于从FDG-PET/CT图像定量评估代谢活跃性皮肤疾病的范围和严重程度。首先，我们使用了一种自动身体区域定位方法，随后采用PET图像标准化技术以减少扫描间测量的变异性。然后，我们生成皮肤外壳PET图像，并开发了一种标准化的最大强度投影（MIP）渲染技术，以实现对患有疾病的皮肤进行可重复的三维可视化。最后，我们引入并验证了一种新的定量评分系统（vCASI评分），通过这些渲染图来测量皮肤疾病的范围和严重程度。
PET图像标准化后，vCASI评分与参考标准真实评估之间的相关性增加，使用调整后的最大百分强度值均值作为MIP渲染的参考点进一步提高了相关性，最高达到0.605。此外，对躯干、胸部、腹部和骨盆的重复vCASI评分评估之间的相关性超过0.85，表明具有高重复性。
vCASI方法能够从FDG-PET/CT图像中准确且可重复地定量评估代谢活跃性皮肤疾病（如皮肤淋巴瘤和银屑病）的范围和严重程度。它解决了与身体区域定位、PET图像的非标准化、稳健可视化以及PET图像标准化显示以检测和量化皮肤疾病相关的挑战。此外，它克服了缺乏实用且经过验证的PET图像皮肤疾病量化评分系统的问题。我们证明vCASI评分系统具有高重复性和良好的准确性，并通过所提出的方法进行了优化。
