OBJECTIVE Histopathological examination (HPE) is the current gold standard for assessing chemotherapy response to tumor, but it is possible only after surgery. The purpose of the study was to develop a noninvasive, imaging-based robust method to delineate, visualize, and quantify the proportions of necrosis and viable tissue present within the tumor along with peritumoral edema before and after neoadjuvant chemotherapy (NACT) and to evaluate treatment response with correlation to HPE necrosis after surgery. METHODS The MRI dataset of 30 patients (N = 30; male:female = 24:6; age = 17.6 ± 2.7 years) with osteosarcoma was acquired using 1.5 T Philips Achieva MRI scanner before (baseline) and after 3 cycles of NACT (follow-up). After NACT, all patients underwent surgical resection followed by HPE. Simple linear iterative clustering supervoxels and Otsu multithresholding were combined to develop the proposed method-SLICs+MTh-to subsegment and quantify viable and nonviable regions within tumor using multiparametric MRI. Manually drawn ground-truth ROIs and SLICs+MTh-based segmentation of tumor, edema, and necrosis were compared using Jacquard index (JI), Dice coefficient (DC), precision (P), and recall (R). Postcontrast T1W images (PC-T1W) were used to validate the SLICs+MTh-based necrosis. SLICs+MTh-based necrosis volume at follow-up was compared with HPE necrosis using paired t test (p ≤ 0.05). RESULTS Active tumor, necrosis, and edema were segmented with moderate to satisfactory accuracy (JI = 62-78%; DC = 72-87%; P = 67-87%; R = 63-88%). Qualitatively and quantitatively (DC = 74 ± 9%), the SLICs+MTh-based necrosis area correlated well with the hypointense necrosis areas in PC-T1W. No significant difference (paired t test, p = 0.26; Bland-Altman plot, bias = 2.47) between SLICs+MTh-based necrosis at follow-up and HPE necrosis was observed. CONCLUSION The proposed multiparametric MRI-based SLICs+MTh method performs noninvasive assessment of NACT response in osteosarcoma that may improve cancer treatment monitoring, planning, and overall prognosis. KEY POINTS • The simple linear iterative clustering supervoxels and Otsu multithresholding-based technique (SLICs+MTh) successfully estimates the proportion of necrosis, viable tumor, and edema in osteosarcoma in the course of chemotherapy. • The proposed technique is noninvasive and uses multiparametric MRI to measure necrosis as an indication of anticancer treatment response. • SLICs+MTh-based necrosis was in satisfactory agreement with histological necrosis after surgery.

中文翻译：

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使用多参数 MR 成像基于 SLIC-supervoxels 对新辅助化疗治疗的骨肉瘤的反应评估。

目的 组织病理学检查 (HPE) 是目前评估肿瘤化疗反应的金标准，但只有在手术后才有可能。该研究的目的是开发一种无创、基于成像的稳健方法来描绘、可视化和量化肿瘤内坏死和存活组织以及新辅助化疗 (NACT) 前后肿瘤周围水肿的比例，并评估治疗与手术后 HPE 坏死相关的反应。方法 使用 1.5 T Philips Achieva MRI 扫描仪在 3 个 NACT 周期之前（基线）和之后（遵循-向上）。NACT 后，所有患者均接受手术切除，然后进行 HPE。将简单的线性迭代聚类超体素和 Otsu 多阈值相结合，开发了所提出的方法 - SLICs + MTh 到使用多参数 MRI 对肿瘤内的可行和不可行区域进行细分和量化。使用 Jacquard 指数 (JI)、Dice 系数 (DC)、精度 (P) 和召回率 (R) 比较了手动绘制的真实 ROI 和基于 SLICs+MTh 的肿瘤、水肿和坏死分割。对比后 T1W 图像 (PC-T1W) 用于验证基于 SLICs+MTh 的坏死。使用配对 t 检验 (p ≤ 0.05) 将随访时基于 SLICs + MTh 的坏死体积与 HPE 坏死进行比较。结果 活动性肿瘤、坏死和水肿以中等至令人满意的准确度进行分割（JI = 62-78%；DC = 72-87%；P = 67-87%；R = 63-88%）。定性和定量 (DC = 74 ± 9%)，基于 SLICs+MTh 的坏死区与 PC-T1W 中的低信号坏死区相关性很好。没有观察到随访时基于 SLICs+MTh 的坏死和 HPE 坏死之间的显着差异（配对 t 检验，p = 0.26；Bland-Altman 图，偏差 = 2.47）。结论 提出的基于多参数 MRI 的 SLICs+MTh 方法对骨肉瘤中的 NACT 反应进行无创评估，可能会改善癌症治疗监测、计划和总体预后。要点 • 简单的线性迭代聚类超体素和基于 Otsu 多阈值的技术 (SLICs+MTh) 成功地估计了化疗过程中骨肉瘤的坏死、存活肿瘤和水肿的比例。• 所提议的技术是无创的，并使用多参数 MRI 来测量坏死作为抗癌治疗反应的指标。