Waitches G, Zawin J K, Poznanski A K
Department of Radiology, Children's Memorial Hospital, Chicago, IL.
AJR Am J Roentgenol. 1994 Jun;162(6):1399-406. doi: 10.2214/ajr.162.6.8192007.
The purpose of this study was to reassess the normal sequence and rate of marrow conversion in the femora of children as depicted on MR imaging.
We retrospectively analyzed 81 T1-weighted MR images of the femur for the appearance and distribution of hematopoietic (red) and fatty (yellow) marrow. Eighty-one children 2 days to 15 years old with no known bone marrow abnormalities were divided into four age groups. The signal intensity and homogeneity of the marrow in the proximal epiphysis, proximal metaphysis, diaphysis, distal metaphysis, distal epiphysis, and greater trochanter were compared with the signal intensity and homogeneity of surrounding muscle and fat and graded by two observers. In select cases, region-of-interest measurements of marrow, subcutaneous fat, and muscle were obtained to validate the visual grading system.
Conversion of hematopoietic to fatty marrow in the femur followed a well-defined sequence, occurring first in the proximal and distal epiphyses, followed by the diaphysis, distal metaphysis, and then the proximal metaphysis. Although high-signal-intensity fatty marrow could be seen within the femoral diaphysis as early as 3 months of age, fatty marrow with various degrees of heterogeneity was routinely seen in this region by 12 months of age. After 5 years of age, the femoral diaphysis showed homogeneous high signal intensity. These findings are in contrast to previously published data that describe homogeneous red marrow within the femoral diaphysis during the first year of life and homogeneous yellow marrow visualized by 10 years of age.
The normal age-related sequence of femoral marrow conversion we saw on MR images conforms to the sequence described in previously published reports, but this transformation, particularly in the diaphysis, occurs significantly earlier in life than has been previously reported. This discrepancy might be explained partially by the sensitivity of signal intensity in the femoral marrow to alterations in window and level settings.
本研究的目的是重新评估磁共振成像（MR成像）所示儿童股骨骨髓转换的正常顺序和速率。
我们回顾性分析了81例股骨的T1加权MR图像，以观察造血（红）骨髓和脂肪（黄）骨髓的外观及分布。81例年龄在2天至15岁、无已知骨髓异常的儿童被分为四个年龄组。将近端骨骺、近端干骺端、骨干、远端干骺端、远端骨骺和大转子处骨髓的信号强度及均匀性与周围肌肉和脂肪的信号强度及均匀性进行比较，并由两名观察者进行分级。在部分病例中，获取骨髓、皮下脂肪和肌肉的感兴趣区测量值，以验证视觉分级系统。
股骨造血骨髓向脂肪骨髓的转换遵循明确的顺序，首先发生在近端和远端骨骺，随后是骨干、远端干骺端，然后是近端干骺端。尽管早在3个月大时就可在股骨干内见到高信号强度的脂肪骨髓，但到12个月大时，该区域通常可见不同程度不均匀的脂肪骨髓。5岁以后，股骨干表现为均匀的高信号强度。这些发现与先前发表的数据不同，先前数据描述在生命的第一年股骨干内为均匀的红骨髓，10岁时可见均匀的黄骨髓。
我们在MR图像上观察到的股骨骨髓转换与年龄相关的正常顺序符合先前发表报告中描述的顺序，但这种转换，尤其是在骨干，在生命中发生的时间比先前报道的要早得多。这种差异可能部分是由于股骨骨髓信号强度对窗宽和窗位设置变化的敏感性所致。
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