Singh Michael D, Contreras-Sánchez Héctor A, Vitkin Alex
University of Toronto, Department of Medical Biophysics, Temerty Faculty of Medicine, Toronto, Ontario, Canada.
University of Toronto, Department of Radiation Oncology, Temerty Faculty of Medicine, Toronto, Ontario, Canada.
J Biomed Opt. 2025 Dec;30(Suppl 3):S34105. doi: 10.1117/1.JBO.30.S3.S34105. Epub 2025 Sep 5.
Tumor tissues exhibit contrast with healthy tissue in circular degree of polarization (DOP) images via higher magnitude circular DOP values and increased helicity-flipping. This phenomenon may enable polarimetric tumor detection and surgical/procedural guidance applications.
Depolarization metrics have been shown to exhibit differential responses to healthy and cancer tissue, whereby tumor tissues tend to induce less depolarization; however, the understanding of this depolarization-based contrast remains limited. Therefore, we investigate depolarization signals from tumor tissue and non-tumor tissue.
Mice ( ) with human pancreatic ductal adenocarcinoma (PDAC) xenografts enable polarimetric comparison between tumor tissue and non-tumor tissues. Modified signed-value DOP equations aid in the interpretation of DOP images, which encode helicity-flipping and co-linearity as negative values, but still yield the same magnitudes as conventional DOP calculations.
Linear DOP is greater in magnitude than circular DOP across both tissue types; however, circular DOP yields greater contrast between tumor and non-tumor tissues. Circular DOP values are higher in magnitude and more negative (i.e., more helicity-flipping) in tumors, whereas linear DOP values exhibit similar behavior; however, they are only slightly higher in magnitude and slightly more negative (i.e., more co-linearity) in tumors.
Circular DOP images yield useful contrast between human PDAC xenografts and surrounding healthy skin in live mice. Each tumor region exhibited higher magnitude circular DOP (and total DOP) values, as previously observed. We noted three indications of Rayleigh scattering in the tumor tissue: (1) linear DOP > circular DOP, (2) helicity-flipping > helicity-preservation, and (3) co-linear intensity > cross-linear intensity. Rayleigh scatterers have been found to be highly polarization preserving; thus, we posit that higher DOP in tumor tissues may arise from an increased presence of Rayleigh scatterers. Furthermore, circular DOP may yield greater contrast between tumor and non-tumor via its well-observed sensitivity to scatterer size. Further investigation is warranted to test these hypotheses.
肿瘤组织在圆偏振度（DOP）图像中与健康组织形成对比，表现为更高的圆DOP值幅度和增加的螺旋度翻转。这种现象可能有助于偏振肿瘤检测及手术/操作引导应用。
已证明去偏振指标对健康组织和癌组织表现出不同反应，即肿瘤组织往往引起较少的去偏振；然而，对这种基于去偏振的对比度的理解仍然有限。因此，我们研究肿瘤组织和非肿瘤组织的去偏振信号。
携带人胰腺导管腺癌（PDAC）异种移植瘤的小鼠能够对肿瘤组织和非肿瘤组织进行偏振比较。修改后的符号值DOP方程有助于解释DOP图像，该图像将螺旋度翻转和共线性编码为负值，但仍产生与传统DOP计算相同的幅度。
在两种组织类型中，线性DOP的幅度均大于圆DOP；然而，圆DOP在肿瘤组织和非肿瘤组织之间产生更大的对比度。肿瘤中的圆DOP值幅度更高且更负（即更多的螺旋度翻转），而线性DOP值表现出类似的行为；然而，它们在肿瘤中的幅度仅略高且略负（即更多的共线性）。
圆DOP图像在活体小鼠的人PDAC异种移植瘤与周围健康皮肤之间产生了有用的对比度。如先前观察到的，每个肿瘤区域均表现出更高幅度的圆DOP（和总DOP）值。我们注意到肿瘤组织中瑞利散射的三个迹象：（1）线性DOP>圆DOP，（2）螺旋度翻转>螺旋度保持，以及（3）共线强度>交叉线强度。已发现瑞利散射体具有高度的偏振保持性；因此，我们推测肿瘤组织中较高的DOP可能源于瑞利散射体的增加。此外，圆DOP可能因其对散射体大小的良好观察到的敏感性而在肿瘤和非肿瘤之间产生更大的对比度。有必要进行进一步研究以检验这些假设。
