## 3 Results  
One representative slice for both homogeneous and heterogeneous spheres for both contrasts and three different acquisition durations (900, 2000, and 7200 s) are shown in Figure 2.  
Quantization level, Q, directly affects all textural features. The relationships between quantization levels and mean textural features (mean of five realizations) for VOItrue is shown in Figure 3. Homogeneity is almost exponentially inversely related to Q, i.e., it exponentially decreases with the increase of Q. The trend is similar for all spheres. Correlation is less affected by Q from 32 and higher irrespective of the size of the sphere. However, the correlation values are very much dependent on the size. There is an approximately linear relationship between Q and contrast. The similar relationship also observed for dissimilarity. For both cases, with the increase of Q, separation among the spheres increases. Energy and entropy have inverse and direct relationships with quantization levels with both of them remaining unchanged for volumes less than 5.58 cm3 and quantization level 32 and higher. For bigger spheres, higher quantization level is required to for both energy and entropy to remain unaffected. It is observed that higher quantization level may represent noise and can make the appearance of homogeneous volumes heterogeneous. On the contrary, low quantization level could remove textural information that would force the appearance of the heterogeneous lesion to be homogeneous. Therefore, it is vital to choose an appropriate Q level without removing the important textural details Overall, it appears that Q level 32 or 64 is the most suitable choice. For this reason, a quantization level of 64 was chosen for further investigation in this study. When a different Q level was used, it is mentioned explicitly. Figure 3: Mean six textural features of five realizations against quantization for VOItrue for all six spheres. (**a**) Homogeneity, (**b**) contrast, (**c**) energy, (**d**) contrast, (**e**) dissimilarity and (**f**) entropy. The features shown here are for 4:1 contrast and 900 s acquisition duration. Figure 4 shows the relationships between textural features and acquisition duration for VOItrue for contrast 2:1. All features remain unchanged with acquisition durations and are reproducible if the true volume is known, except for the smallest one. There are clear separations among volumes for all six textural features. Standard Deviation (SD) reduces with the increase of volume of sphere with energy and entropy is the most reproducible. Figure 5 shows the relationship of textural features with sphere volumes for contrast 4:1. Features extracted from VOIs delineated in the background display the same relationships with the volumes. Homogeneity and entropy are directly related with volumes, i.e., both of them increase with volumes. On the other hand, contrast, dissimilarity, and energy are inversely related to the lesion volumes. Homogeneity, contrast, and dissimilarity are slightly different for the hot spheres and background VOIs of similar sizes. Since background VOIs do not contain edge, it can be interpreted that these three textural measures are more sensitive to the volume edge. However, entropy and energy are almost the same for both spheres and background VOIs. The substantial separation between of correlation between the spheres and background VOIs implies that it is more sensitive to the intensity variations. As the volume increases, all these features reach a plateau at varying rates. The features do not vary with the contrast if VOItrue is known (Figure 6). Figure 4: Six textural features vs. acquisition durations for VOItrue, contrast 2:1, and quantization level 64. (**a**) Homogeneity, (**b**) contrast, (**c**) energy, (**d**) contrast, (**e**) dissimilarity and (**f**) entropy. Figure 5: Six textural features vs. true volume (VOI\({}_{\text{true}}\)) for contrast 4:1, 900 s acquisition, and quantization level 64 for both sphere and background.