MR Imaging Diagnosis of Posterior Cruciate Ligament Injury: Importance of Ancillary Findings

PURPOSE: To evaluate the importance of two ancillary findings of anterior tibial plateau bruise/fracture and popliteus muscle strain on MR diagnosis of posterior cruicate ligament injury. MATERIALS AND METHODS: We retrospectively evaluated 48 patients with confirmed posterior cruciate ligament tear. We studied the incidence of anterior tibial plateau injury and popliteus muscle strain, and the specificity of popliteus muscle strain with or without bony injury. RESULTS: A complete tear of the posterior cruciate ligament was noted in 37 cases, a partial tear in 11. Anterior tibial plateau lesion was found in 21 of 48 cases (44%); This total was made up of 17/37 PCL complete tears (46%) and 4/11 partial tears (36%). The difference in the incidence of complete and partial tears is not statisticially significant. Popliteus muscle injury was found in 20 of 48 cases (42%), the total consisted of 19/37 PCL complete tears (51%) and 1/11 partial tears (10%). The incidence of 42% is relatively high, approximating that of bony injury. The difference in the incidence of complete and partial tears is statistically significant (p<0.006). Specificity for posterior cruciate ligament tear is 69% (20/29), and when concomitant with anterior tibial plateua injury is 94% (16/17). CONCLUSION: As in the case of anterior cruciate ligament injury, these documented ancillary findings of anterior tibial plateau and popliteus muscle injuries are very helpful when MR diagnosis of posterior cruciate ligament injury itself and differentiation of partial and complete rupture are doubtful.

Comparison of Compression Methods of Radiological Images for the Personal Archive

PURPOSE: This study was performed to evaluate the usefulness of compression of radiologic images by using personal computer(PC) and the clinically acceptable compression ratio for personal archiving. MATERIALS AND METHODS: The 300 images of total 60 cases including 10 cases each of plain radiograph, angiography, barium study, US, CT, and MRI were obtained from video camera recorder and were digitalized at image board of PC with 628 x430 matrix and archived to 8 bit gray scale for BMP, TIFF, PCX, GIF, 16 bit color for TGA, and 8 bit gray scale and 24 bit color for JPEG. We compared the image quality on each of the 6 image file formats and various compression ratios by using a ROC(receiver operating characteristic) analysis. RESULTS: The file size order was TGA, BMP, PCX, TIFF, GIF, and the smallest JPEG. The excution time for compression and decompression of images ranged from 10 to 20 seconds and from 4 to 7 seconds, respectively. The compression ratio for TGA and TIFF, PCX, and GIF was less than 1.5:1 whereas it was more than 3:1 for JPEG. The higher the compression ratio of JPEG, the more degradation of image quality occurred although compression ratio below 20:1 made no considerable difference. In the remainder, the image quality was same before and after the compression. The digital images of US, CT, and MR showed lower degradation of image quality than plain radiograph, angiography, and barium study. CONCLUSION: The clinically acceptable limiting compression ratio of JPEG was 20: 1 which would be adequate for managing the large volume of image database on a PC-based digital imaging system.

Normal Variation of Focal T2 Hyperintensities in Anterior Parietal Periventricular white Matter: Another 'Terminal Zones of IV!yelination'

PURPOSE: It has been known that there are several areas of T2 hyperintensities in normal white matter of brain, such as terminal zones of myelination, ependymitis granularis, ones of posterior internal capsule, and perivascular space. The aim of our study is to demonstrate another region of T2 hyperintensities in normal pediatric age group. MATERIALS AND METHODS: We have studied brain MR for 10 normal volunteers and 35 patients without having intracranial lesions in pediatric age group(3-19 years). RESULTS: In 5 among 45 cases, focal T2 hyperintensities were seen in the parietal periventricular white matter beneath the postcentral gyri. They were noted as poorly defined, 5--10mm sized areas of increased signal intensities on T2 weighted axial images. They were also characterized by bilateral, posteromedially oriented, short band-like or oval areas. Interestingly, they were directly continuous with the T2 hyperintensity of posterior internal capsule. In spite of the relatively high frequency in the pediatric population as in our study, this finding has not been reported in the asymptomatic adults. CONCLUSION: The results show that the bilateral anterior parietal hyperintense areas may be another terminal zones of delayed myelination affecting the parietopontine tract. They should be differentiated from pathologic T2 hyperintensities by their characteristic findings.

The Role and Importance of T1 Weighted Axial Image on the Diagnosis of Anterior Cruciate Ligament Tear

PURPOSE: The study is for the evaluation of the role and importance of the T1- weighed axial image on the MR diagnosis of the anterior cruciate ligament(ACL) tear. MATERIALS AND METHODS: We reviewed the axial findings of injured ACL on MR images of arthroscopically confirmed 41 patients. The points of