Australian e-Health Research Centre, CSIRO, Brisbane, Australia.
Australian e-Health Research Centre, CSIRO, Brisbane, Australia.
Neuroimage. 2020 Jul 15;215:116807. doi: 10.1016/j.neuroimage.2020.116807. Epub 2020 Apr 9.
BACKGROUND AND AIMS: Preterm birth imposes a high risk for developing neuromotor delay. Earlier prediction of adverse outcome in preterm infants is crucial for referral to earlier intervention. This study aimed to predict abnormal motor outcome at 2 years from early brain diffusion magnetic resonance imaging (MRI) acquired between 29 and 35 weeks postmenstrual age (PMA) using a deep learning convolutional neural network (CNN) model. METHODS: Seventy-seven very preterm infants (born <31 weeks gestational age (GA)) in a prospective longitudinal cohort underwent diffusion MR imaging (3T Siemens Trio; 64 directions, b = 2000 s/mm). Motor outcome at 2 years corrected age (CA) was measured by Neuro-Sensory Motor Developmental Assessment (NSMDA). Scores were dichotomised into normal (functional score: 0, normal; n = 48) and abnormal scores (functional score: 1-5, mild-profound; n = 29). MRIs were pre-processed to reduce artefacts, upsampled to 1.25 mm isotropic resolution and maps of fractional anisotropy (FA) were estimated. Patches extracted from each image were used as inputs to train a CNN, wherein each image patch predicted either normal or abnormal outcome. In a postprocessing step, an image was classified as predicting abnormal outcome if at least 27% (determined by a grid search to maximise the model performance) of its patches predicted abnormal outcome. Otherwise, it was considered as normal. Ten-fold cross-validation was used to estimate performance. Finally, heatmaps of model predictions for patches in abnormal scans were generated to explore the locations associated with abnormal outcome. RESULTS: For the identification of infants with abnormal motor outcome based on the FA data from early MRI, we achieved mean sensitivity 70% (standard deviation SD 19%), mean specificity 74% (SD 39%), mean AUC (area under the receiver operating characteristic curve) 72% (SD 14%), mean F1 score of 68% (SD 13%) and mean accuracy 73% (SD 19%) on an unseen test data set. Patch-based prediction heatmaps showed that the patches around the motor cortex and somatosensory regions were most frequently identified by the model with high precision (74%) as a location associated with abnormal outcome. Part of the cerebellum, and occipital and frontal lobes were also highly associated with abnormal NSMDA/motor outcome. DISCUSSION/CONCLUSION: This study established the potential of an early brain MRI-based deep learning CNN model to identify preterm infants at risk of a later motor impairment and to identify brain regions predictive of adverse outcome. Results suggest that predictions can be made from FA maps of diffusion MRIs well before term equivalent age (TEA) without any prior knowledge of which MRI features to extract and associated feature extraction steps. This method, therefore, is suitable for any case of brain condition/abnormality. Future studies should be conducted on a larger cohort to re-validate the robustness and effectiveness of these models.
背景与目的:早产会增加发生神经运动发育迟缓的风险。早期预测早产儿的不良结局对于早期干预至关重要。本研究旨在使用深度学习卷积神经网络(CNN)模型,从胎龄 29 至 35 周(PMA)之间获取的早期脑弥散磁共振成像(MRI)预测 2 岁时的异常运动结局。
方法:77 名极早产儿(胎龄<31 周)前瞻性纵向队列接受弥散 MRI(3T 西门子 Trio;64 个方向,b=2000 s/mm)。2 年校正年龄(CA)时的运动结局采用神经感觉运动发育评估(NSMDA)进行测量。评分分为正常(功能评分:0,正常;n=48)和异常评分(功能评分:1-5,轻度-重度;n=29)。对 MRI 进行预处理以减少伪影,上采样至 1.25mm 各向同性分辨率,并估计各向异性分数(FA)图。从每张图像中提取的斑块被用作训练 CNN 的输入,其中每个图像斑块预测正常或异常结局。在后处理步骤中,如果至少有 27%(通过网格搜索确定,以最大程度地提高模型性能)的斑块预测异常结局,则将图像分类为预测异常结局。否则,它被认为是正常的。使用 10 折交叉验证来估计性能。最后,生成模型对异常扫描斑块预测的热图,以探索与异常结局相关的位置。
结果:对于基于早期 MRI 的 FA 数据识别运动异常的婴儿,我们在未见到的测试数据集上实现了平均灵敏度 70%(标准偏差 SD 19%)、平均特异性 74%(SD 39%)、平均 AUC(接受者操作特征曲线下的面积)72%(SD 14%)、平均 F1 分数 68%(SD 13%)和平均准确率 73%(SD 19%)。基于斑块的预测热图显示,模型最常将运动皮层和躯体感觉区域周围的斑块识别为与异常结局相关的位置,准确率高达 74%。小脑部分、枕叶和额叶也与 NSMDA/运动结局不良高度相关。
讨论/结论:本研究建立了一种基于早期脑 MRI 的深度学习 CNN 模型,用于识别有后期运动障碍风险的早产儿,并识别出预测不良结局的脑区。结果表明,可以在接近足月等效年龄(TEA)之前,从弥散 MRI 的 FA 图中识别出有风险的婴儿,而无需任何有关要提取哪些 MRI 特征以及相关特征提取步骤的先验知识。因此,该方法适用于任何脑部状况/异常情况。未来应在更大的队列中进行研究,以重新验证这些模型的稳健性和有效性。
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