Table 1.
Response thresholds derived from retrospective test-retest data.
Figure 1.
Similarity between volumes of interest (VOI) obtained using A50 and various registration strategies.
Box plots of Dice similarity coefficients (DSC) for early (A, C, F) and late (B, D, G) response assessments. DSC were obtained using all VOI (A, B), lung VOI (C, D) or liver VOI (E, F). The mean is illustrated by a square, outliers by dots, and minimum and maximum values by crosses. Abbreviations: A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Figure 2.
Sagittal images of a patient with a bone metastasis.
Top row: baseline (left) and early response (right) PET/CT images. Bottom row: volumes of interest (shown in red) projected onto the baseline (first image) and early response scans (other images) that were obtained using (from left to right): A50 defined on baseline scan, A50 defined on early response scan, and global rigid PET, local rigid CT, non-rigid PET and non-rigid CTPET image registration. All images are shown using the same colour scales. Abbreviations: SUV, standardized uptake values; HU, hounsfield units; A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Figure 3.
Correlation between Dice similarity coefficients and metabolically active tumour volume or tracer uptake heterogenity.
Correlation between Dice similarity coefficients (DSC) obtained using non-rigid PET registration and (A) absolute MATV response values obtained using A50, (B) absolute baseline MATV values obtained using A50, (C) absolute AUC response values obtained using A50, (D) absolute AUC response values obtained using non-rigid PET registration. The two lines represent the trend lines. Note that one data point for late response assessments falls outside the scale of subfigure B (DSC: 0.37, MATV: 500 ml). Abbreviations: MATV, metabolically active tumour volume; AUC, area under a cumulative SUV-volume histogram curve; A50; 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Table 2.
Correlation (R2) of DSC with MATV, AUC or the absolute differences in MATV or AUC between baseline and response scans.
Figure 4.
Effects on responses of various quantitative measures obtained using A50 and various registration strategies.
Box plots illustrating the effects of various registration strategies on early (A, C, E, G, I and K) and late (B, D, F, H, J and L) responses derived from maximum standardized uptake value (SUVmax; A, B), SUVmean (C, D), SUVpeak (E, F), metabolically active tumour volume (MATV; G, H), total lesion glycolysis (TLG; I, J) or area under a cumulative SUV-volume histogram curve (AUC; K, L). Responses were calculated as the values of the (early or late) response scans divided by the values of the baseline scan times 100%. The mean is illustrated by a square, outliers by dots, and minimum and maximum values by crosses. Note that one data point for A50 falls outside the scale of subfigure G (447%). Abbreviations: A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Table 3.
Absolute values of various quantitative measures obtained with A50.
Table 4.
ICC and p-values calculated from response data obtained with various registration strategies and A50.
Figure 5.
Response classifications for early and late response assessments.
Response classifications for early (left part of each subfigure) and late (right part of each subfigure) response assessments based on maximum standardized uptake value (SUVmax; A), SUVmean (B), SUVpeak (C), metabolically active tumour volume (MATV; D), total lesion glycolysis (TLG; E) or area under a cumulative SUV-volume histogram curve (AUC; F). The response values were obtained using A50, local or global rigid image registration, or non-rigid image registration. Abbreviations: PMD, progressive metabolic disease; SMD, stable metabolic disease; PMR, partial metabolic response; IUH, an increase in tracer uptake heterogeneity; SUH, stable tracer uptake heterogeneity; DUH, a decrease in tracer uptake heterogeneity; A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Figure 6.
Sagittal images of a patient with a small lung metastasis.
Top row: baseline (left) and early response (right) PET/CT images. Bottom row: volumes of interest (shown in red) projected onto the baseline (first image) and early response scans (other images) that were obtained using (from left to right): A50 defined on baseline scan, A50 defined on early response scan, and local rigid PET, non-rigid PET and non-rigid CTPET image registration. All images are shown using the same colour scales. Abbreviations: SUV, standardized uptake values; HU, hounsfield units; A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Figure 7.
Axial images of a patient with liver metastases.
Top row: baseline (left) and early response (right) PET/CT images. Bottom row: volumes of interest (shown in red) projected onto the baseline (first image) and early response scans (other images) that were obtained using (from left to right): A50 defined on baseline scan, A50 defined on early response scan, and local rigid PET, non-rigid PET and non-rigid CTPET image registration. All images are shown using the same colour scales. Abbreviations: SUV, standardized uptake values; HU, hounsfield units; A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Figure 8.
Coronal images of a patient with a large liver metastasis showing heterogeneous tracer uptake.
Top row: baseline (left) and early response (right) PET/CT images. Bottom row: volumes of interest (shown in red) projected onto the baseline (first image) and early response scans (other images) that were obtained using (from left to right): A50 defined on baseline scan, A50 defined on early response scan, and local rigid PET, non-rigid PET and non-rigid CTPET image registration. All images are shown using the same colour scales. Abbreviations: SUV, standardized uptake values; HU, hounsfield units; A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.
Figure 9.
Coronal images of a patient with a liver metastasis that showed an increased metabolically active tumour volume.
Top row: baseline (left) and late response (right) PET/CT images. Bottom row: volumes of interest (shown in red) projected onto the baseline (first image) and late response scans (other images) that were obtained using (from left to right): A50 defined on baseline scan, A50 defined on late response scan, and local rigid PET, non-rigid PET and non-rigid CTPET image registration. All images are shown using the same colour scales. Abbreviations: SUV, standardized uptake values; HU, hounsfield units; A50, 3 dimensional (semi-)automatic isocontour method at 50% of the maximum pixel value that corrects for local background.