Fig 1.
Measuring the three diameters of a right lateral retropharyngeal node.
This image was obtained from a 48-year-old NPC woman with a lateral retropharyngeal lymph node (yellow circled) on a T2-weighted MRI. (a) In axial plane, the MAAD (10.6 mm) should be measured first, and the MIAD (6.2 mm) should then be measured in the perpendicular direction. (b) Coronal plane of image showing that the MACD (16.9 mm) of the node can be measured using an electronic caliper easily. NPC, nasopharyngeal cancer; MIAD, minimal axial diameter; MAAD, maximal axial diameter; MACD, maximal coronal diameter.
Fig 2.
Stage I flowchart of MRI follow-up.
Diagnostic results of MRI follow-up for 663 nodes in 335 patients with data on three diameters from MRI.
Fig 3.
Scatter plots of the MIAD in stage I.
Scatter plots of the minimal axial diameter (MIAD) for positive nodes (○) and negative nodes (×) with their optimal cutoff value shown by the line.
Fig 4.
ROC curves of parameters in stage I.
Receiver operating characteristic curves of the three nodal diameters: minimal axial diameter (MIAD), maximal axial diameter (MAAD), and maximal coronal diameter (MACD). The MACD is a much less valid criterion because the area under the curve is obviously lower than that of the other two diameters (without any 95% confidence interval overlapping of its area under curve to that of MIAD and MAAD).
Fig 5.
Stage II flowchart of MRI follow-up.
Diagnostic results of MRI follow-up for 410 nodes in 219 patients with data on four parameters from MRI and PET/CT.
Fig 6.
ROC curves of parameters in stage II.
ROC curves of the three nodal diameters: MIAD, MAAD, MACD, and NSUV. Some overlap of 95%CIs of the area under the curves of the MIAD, MAAD, and NSUV is evident. MIAD, minimal axial diameter; MAAD, maximal axial diameter; MACD, maximal coronal diameter.
Table 1.
Results of NN and expert evaluation for stage I.
Table 2.
Accuracy, sensitivity, specificity, and positive and negative predictive values of the NN and expert evaluation in the stage II comparison.
Table 3.
Accuracy comparison of the NN for 205 nodes and expert evaluation for 141 nodes for 15 combinations of four parameters.
Fig 7.
With the method of brute force attack, nodes were determined to be positive according to an MIAD ≥ 6.1 mm. Note that the combination approach increased the accuracy by only 0.4% [from 89.1% (590/663) to 89.4% (593/663)] by correcting three false negative errors. MIAD, minimal axial diameter; MAAD, maximal axial diameter; MACD, maximal coronal diameter.
Fig 8.
The proposed approach determined through brute force attack: The combination of the MIAD, MAAD, MACD, and NSUV prevented the false positive diagnosis of as many as 6 in 45 nodes (13.3%). MIAD, minimal axial diameter; MAAD, maximal axial diameter; MACD, maximal coronal diameter; NSUVmean, mean standard uptake value.
Fig 9.
Bootstrap sampling method for comparing the stage II parameter combination versus the MIAD alone.
Comparison of the combination method and the MIAD alone by sampling 100 cases and simulating 100 repetitions to obtain the median of accuracy and plot the line chart (if the sampling data have a Gaussian distribution, then the median can be replaced by the mean; thus, t = 42.57 and p < 10−64). MIAD, minimal axial diameter; MAAD, maximal axial diameter; MACD, maximal coronal diameter; NSUVmean, nodal mean standard uptake value.