Abstract：
BACKGROUND: The delineation of intraprostatic lesions is vital for correct delivery of focal radiotherapy boost in patients with prostate cancer (PC). Errors in the delineation could translate into reduced tumour control and potentially increase the side effects. The purpose of this study is to compare PET-based delineation methods with histopathology.
METHODS: The study population consisted of 15 patients with confirmed high-risk PC intended for prostatectomy. [68Ga]-PSMA-PET/MR was performed prior to surgery. Prostate lesions identified in histopathology were transferred to the in vivo [68Ga]-PSMA-PET/MR coordinate system. Four radiation oncologists manually delineated intraprostatic lesions based on PET data. Various semi-automatic segmentation methods were employed, including absolute and relative thresholds, adaptive threshold, and multi-level Otsu threshold.
RESULTS: The gross tumour volumes (GTVs) delineated by the oncologists showed a moderate level of interobserver agreement with Dice similarity coefficient (DSC) of 0.68. In comparison with histopathology, manual delineations exhibited the highest median DSC and the lowest false discovery rate (FDR) among all approaches. Among semi-automatic approaches, GTVs generated using standardized uptake value (SUV) thresholds above 4 (SUV > 4) demonstrated the highest median DSC (0.41), with 0.51 median lesion coverage ratio, FDR of 0.66 and the 95th percentile of the Hausdorff distance (HD95%) of 8.22 mm.
CONCLUSIONS: Manual delineations showed a moderate level of interobserver agreement. Compared to histopathology, manual delineations and SUV > 4 exhibited the highest DSC and the lowest HD95% values. The methods that resulted in a high lesion coverage were associated with a large overestimation of the size of the lesions.
METHODS: The study population consisted of 15 patients with confirmed high-risk PC intended for prostatectomy. [68Ga]-PSMA-PET/MR was performed prior to surgery. Prostate lesions identified in histopathology were transferred to the in vivo [68Ga]-PSMA-PET/MR coordinate system. Four radiation oncologists manually delineated intraprostatic lesions based on PET data. Various semi-automatic segmentation methods were employed, including absolute and relative thresholds, adaptive threshold, and multi-level Otsu threshold.
RESULTS: The gross tumour volumes (GTVs) delineated by the oncologists showed a moderate level of interobserver agreement with Dice similarity coefficient (DSC) of 0.68. In comparison with histopathology, manual delineations exhibited the highest median DSC and the lowest false discovery rate (FDR) among all approaches. Among semi-automatic approaches, GTVs generated using standardized uptake value (SUV) thresholds above 4 (SUV > 4) demonstrated the highest median DSC (0.41), with 0.51 median lesion coverage ratio, FDR of 0.66 and the 95th percentile of the Hausdorff distance (HD95%) of 8.22 mm.
CONCLUSIONS: Manual delineations showed a moderate level of interobserver agreement. Compared to histopathology, manual delineations and SUV > 4 exhibited the highest DSC and the lowest HD95% values. The methods that resulted in a high lesion coverage were associated with a large overestimation of the size of the lesions.
摘要：
背景：前列腺内病变的勾画对于前列腺癌（PC）患者正确实施局灶性放疗增强至关重要。勾画中的错误可以转化为降低的肿瘤控制并潜在地增加副作用。这项研究的目的是比较基于PET的勾画方法与组织病理学。
方法：研究人群由15例确诊高危PC患者组成，拟进行前列腺切除术。[68Ga]-PSMA-PET/MR在手术前进行。将组织病理学中鉴定的前列腺病变转移到体内[68Ga]-PSMA-PET/MR坐标系中。四名放射肿瘤学家根据PET数据手动描绘了前列腺内病变。采用了各种半自动分割方法，包括绝对阈值和相对阈值，自适应阈值，和多级Otsu阈值。
结果：肿瘤学家描绘的总肿瘤体积（GTT）显示出适度的观察者间一致性，Dice相似系数（DSC）为0.68。与组织病理学相比，在所有方法中,人工勾画的DSC中位数最高,而错误发现率(FDR)最低.在半自动方法中，使用超过4(SUV>4)的标准化摄取值(SUV)阈值生成的GTV显示最高的中值DSC(0.41),中位病变覆盖率为0.51，FDR为0.66，Hausdorff距离的第95百分位数（HD95%）为8.22mm。
结论：人工描述显示，观察者之间的协议处于中等水平。与组织病理学相比，手动描绘和SUV>4表现出最高的DSC和最低的HD95%值。导致高病变覆盖率的方法与对病变大小的过度估计有关。
方法：研究人群由15例确诊高危PC患者组成，拟进行前列腺切除术。[68Ga]-PSMA-PET/MR在手术前进行。将组织病理学中鉴定的前列腺病变转移到体内[68Ga]-PSMA-PET/MR坐标系中。四名放射肿瘤学家根据PET数据手动描绘了前列腺内病变。采用了各种半自动分割方法，包括绝对阈值和相对阈值，自适应阈值，和多级Otsu阈值。
结果：肿瘤学家描绘的总肿瘤体积（GTT）显示出适度的观察者间一致性，Dice相似系数（DSC）为0.68。与组织病理学相比，在所有方法中,人工勾画的DSC中位数最高,而错误发现率(FDR)最低.在半自动方法中，使用超过4(SUV>4)的标准化摄取值(SUV)阈值生成的GTV显示最高的中值DSC(0.41),中位病变覆盖率为0.51，FDR为0.66，Hausdorff距离的第95百分位数（HD95%）为8.22mm。
结论：人工描述显示，观察者之间的协议处于中等水平。与组织病理学相比，手动描绘和SUV>4表现出最高的DSC和最低的HD95%值。导致高病变覆盖率的方法与对病变大小的过度估计有关。
