Bin Song^{1}

Objective: To investigate the value of preoperative diffusion-weighted magnetic resonance imaging for predicting aggressive histological features in papillary thyroid cancer (PTC). Methods: The mean, minimum apparent diffusion coefficient (ADCmean and ADCmin) and ADC value of the solid component (ADCsolid) were compared among different aggressive histological groups. Analyses of receiver-operating characteristic curve were also performed. Results: The ADC value in the low aggressive PTC were significantly higher than in high aggressive PTC. ADCmin values had the best performance. Conclusion: ADCmin values derived from DWI could be used as quantitative predictors of aggressive histological features in PTC.

Fig.1. Three
different aggressive thyroid papillary carcinoma and region of interest
selection in the DWI and ADC map
High aggressive PTC without
hobnail variants in a 59-year-old man, of which ADCmin was 0.77×10−3
mm2/s (A, B, C, D, E),
low aggressive PTC in a 41-year-old woman, of which ADCmin was 1.12×10−3
mm2/s (F, G, H, I, J),
and hobnail variants PTC in a 29-year-old woman with ADCmin values of 1.25×10−3
mm2/s (K, L, M, N, O).
Axial DWI images with b value of 800 s/mm2 (A, F, K), zoomed DWI images with ROIs of ADCmean, ADCmin, and
ADCsolid (B, G, L), ADC map (C, H, M), zoomed ADC map with ROIs of
ADCmean, ADCmin, and ADCsolid (D, I, N),
and microscopic image (hematoxylin-eosin stain; original magnification, x100 (E, J, O). In the zoomed DWI images and
ADC map, the largest irregular circle represent ADCmean, medium size circle
represent ADCsolid, and small circles represent ADCmin. E. Photomicrograph of histological specimens shows higher
cellularity, enlarged nuclei, and higher nuclear/cytoplasmic ratio； J. Photomicrograph of
histological specimen showing relatively low cellularity and nuclear/cytoplasmic
ratio；
o.
Photomicrograph of histological specimen showing loosely or individually arranged cancer cells and enlarged gap in tumors.
ADC = apparent diffusion coefficient; PTC = papillary thyroid carcinoma; DWI=
Diffusion-weighted imaging; ADCmean=the mean ADC value; ADCmin= the minimum ADC
value; ADCsolid= the ADC value of the solid component; ROIs = regions of
interest.

Fig.2.
Flowchart
illustrates study group selection
MRI= magnetic resonance
imaging. PTC = papillary thyroid carcinoma. n*= the number of patients. n= the
number of lesions.

Fig.3.
Bland–Altman
plots demonstrates the measurements of the ADCmean, ADCmin, and ADCsolid
values, and demonstrating inter-observer conformity
Plot A shows the results of the ADCmean value between the two observers,
and plot B shows the results of the
ADCsolid value between the two observers, and plot C shows the results of the ADCmin value between the two observers.
The solid line indicates mean difference and the dash line indicates 95% limits
of agreement. ADC=apparent diffusion coefficient; ADCmean=the mean ADC value;
ADCmin= the minimum ADC value; ADCsolid= the ADC value of solid component.

Fig.4 Box
plots illustrating the distribution of the arithmetic means of ADCmean, ADCmin,
and ADCsolid values for the low aggressive PTC, high aggressive PTC without
hobnail variants, and hobnail variants PTC group
The center boxes represent the
values from the lower to upper quartile (25-75 percentiles). The lines include
all values except for outliers represented by dotted circles. A dotted circle
defines a value that is smaller than the lower quartile minus 1.5 times the
interquartile range, or larger than the upper quartile plus 1.5 times the
interquartile range. ADC = apparent diffusion coefficient; PTC = papillary
thyroid carcinoma; ADCmean=the mean ADC value; ADCmin= the minimum ADC value;
ADCsolid= the ADC value of solid component.

Fig.5 ROC
curve of the different ADC values (ADCmean, ADCmin, ADCsolid) used to
distinguish high aggressive PTC without hobnail variants from low aggressive
PTC and size of the lesion used to
distinguish hobnail variants PTC from low aggressive PTC.
A. The
AUC of the different ADC values (ADCmean, ADCmin, ADCsolid) were 0.758 (blue
line), 0.851 (yellow line), 0.787 (green line), respectively. B. The AUC for size of
the lesion between the low aggressive PTCs and hobnail variants
PTC group was 0.896. ROC = Receiver operator characteristic. ADC =
apparent diffusion coefficients. PTC = papillary thyroid carcinoma. AUC = area
under the curve. ADCmean=the mean ADC value. ADCmin= the minimum ADC value.
ADCsolid= the ADC value of solid component.