[en] Objective: To analyze the pattern of normal bone marrow on whole body diffusion weighted imaging (WB-DWI) and its influence factors. Methods: A total of 98 healthy volunteers (male 47 and female 51). All volunteers underwent WB-DWI at 1.5 T MR scan. The ADC value, the signal intensity on DWI obtained with a b value of 800 s/mm"2 (SI_D_W_I), and the signal intensity on short time inversion recovery images (SI_S_T_I_R) of thoracic vertebrae, lumber vertebrae,bilateral head of femur, bilateral neck of femur, bilateral superior segment of femur, bilateral inferior segment of femur, bilateral ilium,bilateral head of humerus, bilateral scapula were measured and compared with ANOVA test and Student-Newman-Keuls test. The normal appearance of bone marrow on WB-DWI was assessed. The relationship between the SI_D_W_I and the ADC, and the SI_D_W_I and the SI_S_T_I_R of bone marrow were analyzed. The ADC of bone marrow between male and female were compared. Spearman correlation analysis was performed for different age groups. Results: (1) Bone marrow signal intensity was different among 98 healthy volunteers. Bone marrow in 69 healthy volunteers (female 24, male 45) showed low to intermediate signal intensity, whereas in the remaining 29 healthy volunteers (female 27, male 2) showed high signal intensity. (2) The SI_D_W_I of thoracic vertebrae (median 44.54), lumber vertebrae (median 35.01), head of femur (median 13.61), neck of femur (median 16.00), superior segment of femur (median 21.45), ilium (median 25.77), head of humerus (median 18.35), scapula (median 36.12) was positively correlated with the ADC [(0.55 ±0.08) × l0"-"3, (0.53 ±0.08) × 10"-"3, (0.30 ± 0.10) × 10"-"3,(0.42 ± 0.16) × 10"-"3, (0.74±0.14) ×l0"-"3, (0.49±0.10) ×10"-"3, (0.36±0.13) ×10"-"3, (0.49±0.11) × 10"-"3 mm"2/s]and the SI_S_T_I_R (median 61.81, 64.99, 53.27, 69.08, 73.10, 66.35, 73.16, 79.81), r=0.513 and 0.695, 0.741 and 0.764, 0.443 and 0.489, 0.641 and 0.656, 0.510 and 0.648, 0.475 and 0.715, 0.366 and 0.446, 0.437 and 0.739; P<0.01. (3) There was significant difference of the ADC of bone marrow in different bone, F=138.69, P<0.01. Student-Newman-Keuls test revealed that no significant difference was found in the ADC between thoracic vertebrae and lumbar vertebrae, ilium and scapula, head of humerus and inferior segment of femur (P>0.05), and significant difference was found in the ADC values between the remaining two groups (P<0.05). The bones associated with decreasing ADC values were superior segment of femur, thoracic vertebrae and lumber vertebrae, ilium and scapula, neck of femur, head of humerus,head of femur and inferior segment of femur. (4) The ADC values of bone marrow of female subjects in thoracic vertebrae [(0.59 ±0.07) × 10"-"3 mm"2/s],lumber vertebrae [(0.58 ±0.06) × 10"-"3 mm"2/s], head of femur (median 0.33 × 10"-"3 mm"2/s), neck of femur (median 0.53 × 10"-"3 mm"2/s), superior segment of femur (median 0.81 × 10"-"3 mm"2/s), inferior segment of femur (median 0.32 ×10"-"3 mm"2/s), ilium [(0.52 ± 0.09 ) × 10"-"3 mm"2/s], head of humerus (median 0.42 × 10"-"3 mm"2/s), scapula [(0.53 ± 0.09) × 10"-"3 mm"2/s] were significantly higher than those of male subjects [(0.51 ±0.07) × 10"-"3, (0.48 ±0.07) × 10"-"3, median 0.23 × 10"-"3, median 0.31 × 10"-"3, median 0.66 × 10"-"3, median 0.23 × 10"-"3, (0.46 ±0.10) × 10"-"3, median 0.27 × 10"-"3, (0.45 ±0.11) × 10"-"3 mm"2/s]. (5) There was significant negative correlation between the ADC values of bone marrow and age in thoracic vertebrae, lumber vertebrae, head of femur, neck of femur, superior segment of femur, ilium, head of humerus for female subjects, r=-0.549, -0.629, -0.329, -0.524, -0.338, -0.548 and -0.416, respectively, P<0.05. There was no significant correlation between ADC values and age in inferior segment of femur and scapula for female subjects and all the regions for male subjects (P>0.05). Conclusions: The ADC and the SI_S_T_I_R of bone marrow correlates with the SI_D_W_I. The ADC values of bone marrow is affected by age and sex, and is different for different bones. (authors)

[en] Highlights: • Sr promotes micro-galvanic corrosion and undermining of Mg₁₇Sr₂ phases. • Sr increases weight loss rate but inhibits localized corrosion of Mg-Zn-Mn alloy. • Corrosion depth/second phase spacing keep constant as added Sr content exceeds 1.0 wt.%. • The optimum Sr content is 1.01.5 wt.% in Mg-1Zn-1 Mn alloy. -- Abstract: Effect of Sr on microstructure and corrosion behavior of biodegradable Mg-1Zn-1Mn-xSr alloy is investigated. Decrease in second phase spacing and linear increase of Mg₁₇Sr₂ fraction are observed with increasing Sr content. Corrosion rate increases linearly with increasing Sr content from 0 to 1.5 wt.% because of the enhanced micro-galvanic corrosion. Undermining of Mg₁₇Sr₂ and α-Mg grains results in the dramatic increase in corrosion rate at a high Sr content (3.0 wt.%). Localized corrosion is inhibited by alloying with Sr, yielding an optimum Sr content of 1.01.5 wt.% with comprehensive consideration of uniform/localized corrosion resistance and biomedical adaptability.