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Objective To evaluate the imaging characteristics of chondromalacia patellae(CMP)in low-field MR and the value of MR in diagnosis.Methods 37 cases with CMP proved by arthroscopy and/or operation were carefully examined by 0.3 Tesla permanent magnet MR unit.The results of MRI were retrospectively analyzed according to that of arthroscopy and operation to search for the MR imaging manifestations of different degrees of patellae cartilage injuries in CMP.Results According to the golden-standard by arthroscopy and operation as for CMP,the overall diagnostic accuracy of MRI was 79.4%,with 28.6% accuracy in the early phase,92.6% in the late phase of CMP.Conclusion Low-field MR imaging is accurate in diagnosing CMP in the late phase and should be suggested as a useful nontraumatic imaging modality in the assessment of CMP before arthroscopy and operation.
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Objective To study the influence of CRT brightness on image reading. Methods Both physical testing and compared viewing were used in the study. (1) Setting the CRT brightness at high and low grade (the blank brightness of CRT was 112 cd/m 2 and 82 cd/m 2, respectively). (2) 21 films with the density ranging from 0.27 to 2.71 were digitized by a scanner and displayed on the CRT. The brightness of CRT that varied with film density was measured by a bright meter, then the relation chart between CRT brightness and the film density was drawn. (3) Thirteen films on which there were many small and low contrast signals were viewed on CRT by three doctors. The tested data were calculated by statistics (? 2 test, the difference was significantly marked when P 0.05), but the signals viewed in the lung were 87 and 29, and the difference was significantly marked (? 2=53.73, P