Performance of Apparent Diffusion Coefficient Values and Conventional MRI Features in Differentiating Tumefactive Demyelinating Lesions From Primary Brain Neoplasms

Abstract

Objective: Tumefactive demyelinating lesions (TDLs) remain one of the most common brain lesions to mimic a brain tumor, particularly primary CNS lymphoma (PCNSL) and high-grade gliomas. The purpose of our study was to evaluate the ability of apparent diffusion coefficient (ADC) values and conventional MRI features to differentiate TDLs from PCNSLs and high-grade gliomas.

Materials and methods: Seventy-five patients (24 patients with TDLs, 28 with PCNSLs, and 23 with high-grade gliomas) with 168 brain lesions (70 TDLs, 68 PCNSLs, and 30 high-grade gliomas) who underwent DWI before surgery or therapy were included in the study. Minimum ADC (ADC(min)) and average ADC (ADC(avg)) values were calculated for each lesion. ANOVA and ROC analyses were performed. ROC analyses were also performed for the presence of incomplete rim enhancement and for the number of lesions. Multiple-variable logistic regression with ROC analysis was then performed to evaluate performance in multiple-variable models.

Results: ADC(min) was statistically significantly higher (p < 0.01) in TDLs (mean, 0.886; 95% CI, 0.802-0.931) than in PCNSLs (0.547; 95% CI, 0.496-0.598) and high-grade gliomas (0.470; 95% CI, 0.385-0.555). (All ADC values in this article are reported in units of × 10(-3) mm(2)/s.) ADC(avg) was statistically significantly higher (p < 0.01) in TDLs (mean, 1.362; 95% CI, 1.268-1.456) than in PCNSLs (0.990; 95% CI, 0.919-1.061) but not in high-grade gliomas (1.216; 95% CI, 1.074-1.356). Multiple-variable models showed statistically significant individual effects and superior diagnostic performance on ROC analysis.

Conclusion: TDLs can be diagnosed on preoperative MRI with a high degree of specificity; MRI features of incomplete rim enhancement, high ADC values, and a large number of lesions individually increase the probability and diagnostic confidence that a lesion is a TDL.

Keywords: apparent diffusion coefficient (ADC); diffusion; primary CNS lymphoma (PCNSL); tumefactive demyelinating lesion (TDL); tumefactive demyelination.

Fig. 1

MRI of 36-year-old man with tumefactive demyelinating lesion (TDL). A–E, Axial DW image (A), axial T2-weighted FLAIR image (B), axial gadolinium-enhanced T1-weighted image (C), axial apparent diffusion coefficient (ADC) map (D), and axial ADC map (E) with ROI (outline, E) drawn on it after review of all images. ROI was drawn to include whole lesion and includes rim of reduced diffusion seen on DW image (A) and ADC maps (D and E) and corresponding to incomplete rim of contrast enhancement seen on gadolinium enhanced T1-weighted image (C). Minimum ADC (ADC_min) measured 0.764, and average ADC (ADC_avg) measured 1.620. Relatively younger age of patient and high ADC_min, high ADC_avg, and incomplete rim of contrast enhancement all suggest TDL. Diagnosis of TDL was proven at biopsy.

Fig. 2

MRI of tumefactive demyelinating lesions (TDLs) and brain neoplasms. Axial T2 FLAIR (A), axial DWI (B), axial ADC map (C), and axial post-gadolinium T1 (D) MR images from an 88 year old female patient with biopsy proven primary central nervous system lymphoma. Note the corresponding relatively low ADC values visible on the ADC map (C). ADC_min measured 0.580 and ADC_avg measured 1.067, supporting the diagnosis. Axial T2 FLAIR (E), axial DWI (F), axial ADC map (G), and axial post-gadolinium T1 (H) MR images from a 45 year old female patient with a tumefactive demyelinating lesion. Note the corresponding relatively high ADC values visible on the ADC map (G). ADC_min measured 1.150 and ADC_avg measured 1.460, supporting the diagnosis. Axial T2 FLAIR (I), axial DWI (J), axial ADC map (K), and axial post-gadolinium T1 (L) MR images from a 71 year old female patient with biopsy proven glioblastoma. Note the corresponding relatively low ADC values visible on the ADC map. ADC_min measured 0.431 and ADC_avg measured 1.399 consistent with the results of our study.

Fig. 2

MRI of tumefactive demyelinating lesions (TDLs) and brain neoplasms. Axial T2 FLAIR (A), axial DWI (B), axial ADC map (C), and axial post-gadolinium T1 (D) MR images from an 88 year old female patient with biopsy proven primary central nervous system lymphoma. Note the corresponding relatively low ADC values visible on the ADC map (C). ADC_min measured 0.580 and ADC_avg measured 1.067, supporting the diagnosis. Axial T2 FLAIR (E), axial DWI (F), axial ADC map (G), and axial post-gadolinium T1 (H) MR images from a 45 year old female patient with a tumefactive demyelinating lesion. Note the corresponding relatively high ADC values visible on the ADC map (G). ADC_min measured 1.150 and ADC_avg measured 1.460, supporting the diagnosis. Axial T2 FLAIR (I), axial DWI (J), axial ADC map (K), and axial post-gadolinium T1 (L) MR images from a 71 year old female patient with biopsy proven glioblastoma. Note the corresponding relatively low ADC values visible on the ADC map. ADC_min measured 0.431 and ADC_avg measured 1.399 consistent with the results of our study.

Fig. 3

Boxplot of minimum apparent diffusion coefficient (ADC_min) values for each lesion group. ADC_min values are statistically significantly higher for tumefactive demyelinating lesions (TDLs) than for primary CNS lymphomas (PCNSLs) (p < 0.01) and high-grade gliomas (p < 0.01) with one-way ANOVA using Tukey-Kramer pairwise test. Box centered at mean ADC_min; middle line in boxes = median ADC_min; upper and lower lines of boxes = upper and lower quartiles, respectively; whiskers = highest value to lowest value excluding any statistical outliers; circle = outside value, greater than upper quartile plus 1.5 times interquartile range.

Fig. 4

Boxplot of average apparent diffusion coefficient (ADC_avg) values for each lesion group. ADC_avg values are statistically significantly higher for tumefactive demyelinating lesions (TDLs) than for primary CNS lymphomas (PCNSLs) (p < 0.01) but not for high-grade gliomas (p > 0.05) with one-way ANOVA using Tukey-Kramer pairwise test. Box centered at mean ADC_avg; middle line in boxes = median ADC_avg; upper and lower lines of boxes = upper and lower quartiles, respectively; whiskers = highest value to lowest value excluding any statistical outliers; circle = outside value, greater than upper quartile plus 1.5 times interquartile range; triangle = far out value, greater than upper quartile plus 3 times interquartile range.

Fig. 5

Performance of single-variable models for diagnosis of tumefactive demyelinating lesions (TDLs). Youden index J is defined as sensitivity ‒ (1 ‒specificity) and is highest vertical distance from line where AUC > 0.5 (diagonal line). A, Graph shows results of ROC analysis using minimum apparent diffusion coefficient (ADC_min) to diagnose TDLs. B, Graph shows results of ROC analysis using average ADC (ADC_avg) to diagnose TDLs. C, Graph shows results of ROC analysis using incomplete rim enhancement to diagnose TDLs. D, Graph shows results of ROC analysis using number of lesions to diagnose TDLs.

Fig. 6

Performance of multiple-variable models for diagnosis of tumefactive demyelinating lesions (TDLs). Youden index J is defined as sensitivity ‒(1 ‒ specificity) and is highest vertical distance from line where AUC > 0.5 (diagonal line). Thresholds refer to calculated probabilities from logistic regression equations. A, Graph shows results of ROC analysis using minimum apparent diffusion coefficient (ADC_min), incomplete rim enhancement, and number of lesions to diagnose TDLs. B, Graph shows results of ROC analysis using average ADC (ADC_avg), incomplete rim enhancement, and number of lesions to diagnose TDLs. C, Graph shows results of ROC analysis using incomplete rim enhancement and number of lesions to diagnose TDLs.