Application of Cellular Microstructural Diffusion MRI (Cell size imaging) in rectal lesions: a preliminary study

Peisi Kou ¹ Liangjie Lin ² Ying Li ¹ Hui Qin ³ Kun Zhang ¹ Wenhua Zhang ¹ Juan Li ¹ Yong Zhang ¹ Jingliang Cheng ^1*

• ¹ Department of MRI, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
• ² Clinical and Technical Support, Philips Healthcare, Beijing, China, Beijing, China
• ³ Department of Pathology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan Province, China

Objectives: To explore the value of cellular microstructural mapping by IMPULSED (imaging microstructural parameters using limited spectrally edited diffusion) method in evaluating the histological type and prognostic factors of rectal lesions.Sixty-six patients with rectal tumors were enrolled in this study. All subjects underwent MRI scans including conventional diffusion weighted imaging (DWI) and the IMPULSED MRI scans of oscillating gradient spin-echo (OGSE) and pulse gradient spin-echo (PGSE) sequences. Parameters including mean cell diameter (dmean), intracellular fraction (vin), extracellular diffusivity (dex), cellularity, and apparent diffusion coefficient (ADC) values were measured in different histopathologic types, grades, stages, and structure invasion statuses. The receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic power. The sensitivity, specificity, and the AUCs were calculated.Results: Our preliminary results illustrated that malignant lesion showed higher vin and cellularity, lower dex and ADC values compared to benign lesion, while no significant difference was seen for dmean. Vin and cellularity of rectal common adenocarcinoma (AC) were significantly higher than those of rectal mucinous adenocarcinoma (MC) were lower in AC. In AC group, the dmean had significant difference between negative and positive tumor budding (TB). No significant difference of dmean, vin, dex, cellularity or ADC values was observed in AC with different grade, T stage, N stage, perineural and lymphovascular invasion. The ROC curves showed that the area under the curves (AUCs) of vin, dex, cellularity, and ADC values (ADCPGSE, ADC17Hz, and ADC of conventional DWI) for distinguishing malignant and benign lesion were 0.803, 0.757, 0.948, 0.807, 0.908 and 0.905, respectively. The AUCs of vin, dex, cellularity, and ADC values (ADCPGSE, ADC17Hz, ADC33Hz, and ADC of conventional DWI) in distinguishing AC from MC were 0.887, 0.802, 0.906, 0.896, 0.896, 0.781 and 0.991, respectively. The AUC of the dmean for evaluating TB status was 0.726. The AUC of ADC from conventional DWI for evaluating WHO grade was 0.739. Conclusion: Cellular microstructural mapping by the IMPULSED method has great potential in preoperative evaluation of rectal lesions. It could be helpful in differentiating malignant and benign lesions, distinguishing AC from MC, and in predicting the TB status.