Fig 1.
MRI = magnetic resonance imaging.
Table 1.
Results of standard MRI analysis and diagnostic performance for treatment response of osteosarcoma.
Fig 2.
Bland-Altman plots of ADC measurements derived from single-section ROIs between two readers.
(A) pretreatment 2D ADCminimum, (B) posttreatment 2D ADCminimum, (C) pretreatment 2D ADCmean, and (D) posttreatment 2D ADCmean. The unit of ADC is μm2/sec. pre- = pretreatment; post- = posttreatment; ADCmin = ADCminimum.
Table 2.
Comparison of 2D ADC measurement for treatment response of osteosarcoma.
Table 3.
Comparison of 3D ADC measurement for treatment response of osteosarcoma.
Fig 3.
MRI of fibroblastic osteosarcoma and applying ADC values derived from single-section ROI can complement diagnostic ability.
(A) Axial fat-suppressed (FS) contrast-enhanced T1-weighted image (T1WI) before treatment shows a tumor in proximal tibia with extraosseous lesions (arrows). (B) DWI (b of 800 sec/mm2) with ADC map before treatment shows 2D ADCminimum and 2D ADCmean of 870μm2/sec and 1011μm2/sec, respectively. (C) ADC histogram derived from whole-tumor volume before treatment shows 3D ADCmean of 943μm2/sec, 3D ADCskewness of 1.54, and 3D ADCkurtosis of 6.83. (D) Axial FS contrast-enhanced T1WI after treatment shows the little change in size with heterogeneously enhancing extraosseous lesion (thick arrow), interpreted as equivocal in both readers. (E) DWI with ADC map after treatment shows 2D ADCminimum and 2D ADCmean of 1542μm2/sec and 2107μm2/sec, respectively, indicating a good responder. (F) ADC histogram derived from whole-tumor volume after treatment shows 3D ADCmean of 1994μm2/sec, 3D ADCskewness of -0.82, and 3D ADCkurtosis of 3.43. The percent change of 2D ADCminimum and 2D ADCmean present as 77.2% and 105.6%, respectively. At histopathology, the tumor showed more than 95% necrosis, demonstrating a good responder.
Fig 4.
MRI of osteoblastic osteosarcoma and applying ADC values derived from single-section ROI can complement diagnostic ability.
(A) Axial fat-suppressed (FS) contrast-enhanced T1-weighted image (T1WI) before treatment shows a tumor in proximal tibia with extraosseous lesion (thick arrow). (B) DWI (b of 800 sec/mm2) with ADC map before treatment shows 2D ADCminimum and 2D ADCmean of 880μm2/sec and 1179μm2/sec, respectively. (C) ADC histogram derived from whole-tumor volume before treatment shows 3D ADCmean of 1472μm2/sec, 3D ADCskewness of 0.55, and 3D ADCkurtosis of 2.26. (D) Axial FS contrast-enhanced T1WI after treatment shows marked decrease in extraosseous lesion (thick arrow) with heterogeneously enhancement (thin arrow), interpreted as good responder in reader 2. (E) DWI with ADC map after treatment shows 2D ADCminimum and 2D ADCmean of 1047μm2/sec and 1395μm2/sec, respectively, indicating a poor responder. (F) ADC histogram derived from whole-tumor volume after treatment shows 3D ADCmean of 1500μm2/sec, 3D ADCskewness of 0.10, and 3D ADCkurtosis of 3.15. The percent change of 2D ADCminimum and 2D ADCmean presents as 19.0% and 18.3%, respectively. The histopathology demonstrates a poor treatment response (necrosis = 32%).
Table 4.
Diagnostic performances of 2D ADC measurement for treatment response.
Fig 5.
MRI of osteoblastic and chondroblastic osteosarcoma, lack of pretreatment DWI, indicating that ADC values derived from whole-tumor volume can reinforce diagnostic ability.
(A) Axial fat-suppressed (FS) contrast-enhanced T1-weighted image (T1WI) before treatment shows a tumor with extraosseous lesion (thick arrow) in distal femur. (B) Axial FS contrast-enhanced T1WI after treatment shows slight decrease in extraosseous tumor size (thick arrow), interpreted as equivocal in reader 1. (C) DWI (b of 800 sec/mm2) with ADC map after treatment shows 2D ADCminimum and 2D ADCmean of 1235μm2/sec and 1968μm2/sec, respectively. Posttreatment values are also equivocal because of neighboring cutoff values and lack of pretreatment DWI. (D) ADC histogram derived from whole-tumor volume after treatment shows 3D ADCmean of 1864μm2/sec, 3D ADCskewness of 0.185, and 3D ADCkurtosis of 4.14, suggesting a poor responder. The histopathologic finding demonstrates a poor treatment response (necrosis = 70%).
Table 5.
Diagnostic performances of 3D ADC measurement for treatment response.
Fig 6.
ROC comparison between three prediction models for both readers.
AUC is increased by adding parameters to standard MRI. The 1st model: standard MRI alone, the 2nd model: standard MRI with posttreatment 2D ADCmean, the 3rd model: standard MRI with posttreatment 2D ADCmean and posttreatment 3D ADCskewness. post- = posttreatment; 2D = single-section ROI; 3D = whole-tumor volume; ROC = receiver operating characteristic; AUC = areas under the curve.