Abstract
BackgroundMagnetic resonance imaging (MRI) has limited accuracy in detecting pelvic lymph node (PLN) metastasis. This study aimed to examine the use of intravoxel incoherent motion (IVIM) in classifying pelvic lymph node (PLN) involvement in cervical cancer patients.MethodsFifty cervical cancer patients with pre-treatment magnetic resonance imaging (MRI) were examined for PLN involvement by one subspecialist and one non-subspecialist radiologist. PLN status was confirmed by positron emission tomography or histology. The tumours were then segmented by both radiologists. Kruskal-Wallis tests were used to test for differences between diffusion tumour volume (DTV), apparent diffusion coefficient (ADC), pure diffusion coefficient (D), and perfusion fraction (f) in patients with no malignant PLN involvement, those with sub-centimetre and size-significant PLN metastases. These parameters were then considered as classifiers for PLN involvement, and were compared with the accuracies of radiologists.ResultsTwenty-one patients had PLN involvement of which 10 had sub-centimetre metastatic PLNs. DTV increased (p = 0.013) while ADC (p = 0.015), and f (p = 0.006) decreased as the nodal status progressed from no malignant involvement to sub-centimetre and then size-significant PLN metastases. In determining PLN involvement, a classification model (DTV + f) had similar accuracies (80%) as the non-subspecialist (76%; p = 0.73) and subspecialist (90%; p = 0.31). However, in identifying patients with sub-centimetre PLN metastasis, the model had higher accuracy (90%) than the non-subspecialist (30%; p = 0.01) but had similar accuracy with the subspecialist (90%, p = 1.00). Interobserver variability in tumour delineation did not significantly affect the performance of the classification model.ConclusionIVIM is useful in determining PLN involvement but the added value decreases with reader experience.
Highlights
Magnetic resonance imaging (MRI) has limited accuracy in detecting pelvic lymph node (PLN) metastasis
FDG-PET/CT, which has been shown to have high accuracy [11] in identifying PLN involvement, is used clinically to determine the nodal status but imparts substantial radiation burden with its high cost and limited availability. It can be useful in identifying non-invasive imaging features of the primary tumour on MRI that are associated with the presence of PLN metastases in cervical cancer
Tumour characteristics diffusion tumour volume (DTV) increased while apparent diffusion coefficient (ADC), D, and f decreased as the nodal status progressed from no malignant involvement to sub-centimetre and size-significant PLN involvement, though the differences in D among the different groups were not significant (Table 2 and Fig. 4)
Summary
Magnetic resonance imaging (MRI) has limited accuracy in detecting pelvic lymph node (PLN) metastasis. MRI is used to evaluate the primary tumour extent and at the same time to assess lymph node involvement, in which the diagnosis of the latter relies on size- and morphology-based criteria on T2weighted (T2W) images [5,6,7] These criteria have shortcomings in that they are susceptible to false positives due inflammatory enlarged lymph nodes [8, 9] and false negatives due to difficulties in detecting subcentimetre metastatic PLNs [10]. FDG-PET/CT, which has been shown to have high accuracy [11] in identifying PLN involvement, is used clinically to determine the nodal status but imparts substantial radiation burden with its high cost and limited availability It can be useful in identifying non-invasive imaging features of the primary tumour on MRI that are associated with the presence of PLN metastases in cervical cancer
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