| Objective: To explore the emerging time, location, normal appearances and character of development of the secondary ossification center of distal ulna with MRI examination and compare the results with X-ray examination to find the differences between the two results,which are expected to obtain the determinant indicator for epiphysis heterolysis that can also be a new indicator for bone age determination with MRI ,and lay a foundation for clinical diagnosis of epiphysis injuries.Methods: Fifty-seven healthy boys volunteers were studied right wrist joint by using 1.5 Tesla ultraconduct magnetic resonance and CR. These cases were divided into 5 groups according to the age, from 5 years-old group to 9 years-old group. There are 9 cases in five-year group, 12 cases in six-year group, 14 in seven-year group, 14 in the eight-year group and 8 in the nine-year group. Every group were scanned right wrist joint by MRI and then examined by CR.MRI scanning parameters with FLASH2D+FS gradient echo added fat-suppression sequence were as follows:TR 669ms,TE ms,Flip angle 60,distance 0mm,thickness 3.0mm,scanning layers ranging from 14 to 18,scanning matrix 307×512,twice signal collection,soft coil wrapping the wrist joints tested. The forearm is straight with palm down. the joints were scanned from coronal and Y axes. The CR parameters are as follows: Voltage 60KV, Electric current 6～8mA, Time of exposure 1.5ms,distance 50cm.Read the photos of MRI and CR, find the differences of the two results. The emerging age of ossification center was determined if at a certain age a center emerged more than 50%in the youngest group.Results: No secondary ossification centers of distal ulna of right wrists were obsevered at X-ray images in the five-year group. At the MRI images, the epiphytical cartilage of distal ulna was characteristic with high signal density, the appearances of which were looked like mature distal part of ulna. The metaphysis is low signal. In the six-year group, there were no secondary ossification centers at the X-ray images, and the MRI images were the same to five-year group. In the seven group 21.4%of the cases (3 cases)were obsevered the secondary ossification center at X-ray images, which was like a grain and at the line of metaphysis of the distal radius. At the MRI images, the secondary ossification center was low signal, which was in the high signal intensity epiphytical cartilage and was near the metaphysis of distal ulna, not at the center of epiphytical cartilage. Two cases was not obsevered the secondary ossification center at the X-ray images, but at MRI images there was a low signal intensity zone in the cartilage of epiphysis, which paralleled metaphysis .There were no secondary ossification centers at another nine cases. In the eight-year group,57.1%of the cases (8 cases)were obsevered the secondary ossification centers at X-ray images. The MRI images were looked like the seven-year group, but the area of secondary ossification center was larger than the seven-year group; There are two kinds of signal zone at the area between secondary ossification center and the metaphysis at MRI images: The high signal density around the ossification and the low signal density near to the metaphysis; The area is the growth plate; Four case was not obsevered the secondary ossification center at the X-ray images, but at MRI images there was a line-like low signal intensity zone in the cartilage of epiphysis. There were no secondary ossification centers at another two cases; In the nine-year group,87.5%of the cases(7 cases) were obsevered the secondary ossification centers at the X-ray images or the MRI images; The images of the secondary ossification centers at X-ray was looked like a disk, the center of which was depressed; And at MRI images, it was band-like low signal ,and the cartilage of epiphysis which was high signal density ,was thicker than the eight group. There was one case which had no the secondary ossification centers at X-ray, the distal part of ulna was high signal density epiphytical cartilage.Conclusion: 1.The cartilage of epiphysis of distal ulna were characteristic with high signal at MR image, the appearances of which was looked like mature distal part of ulna, but it was not visible at X-ray image. 2. Before the secondary ossification center of distal ulna emerges, there was a low signal intensity zone in the cartilage of epiphysis, which was not visible at X-ray image. So the secondary ossification center of distal ulna could be visible earlier at MR image than X-ray image. Because an intact provisional calcification zone means the normal development of cartilage, so it will help us research the early development of cartilage.3.When the secondary ossification center emerge, it had millet-like low signal intensity in the high signal intensity epiphytical cartilage. At MR Image. , the secondary ossification center was near the metaphysis of distal ulna, not in the center of the epiphytical cartilage. The secondary ossification center could also be visible at X-ray image. |
PDF Full Text Request