Dynamic gadoteridol-enhanced MR imaging in the end of growing long bone of piglets.

BACKGROUND: It is of value to identify the non-invasive means that can accurately reflect the blood supply of epiphysis and is more sensitive in detection of early ischemia of epiphysis than the conventional gadoteridol (Gd)-enhanced SE T1WI. The aim of this study was to evaluate the blood supply of various anatomic regions at the end of normal growing long bone using dynamic Gd-enhanced MR imaging and compare the sensitivities between dynamic Gd-enhanced MR imaging and conventional Gd-enhanced SE T1WI in the detection of decreased blood perfusion of early epiphyseal ischemia. METHODS: Twenty-seven two-week-old piglets were used in this study. For the study of the end of normal growing long bone, unilateral MR imaging of the distal femur and proximal tibia was performed on eleven piglets. The comparison was made among various anatomic regions (physeal and epiphyseal cartilage, metaphyseal spongiosa, the secondary ossification center and metaphysis) using MRI in terms of the enhancement ratio and speed. Their relationships with the histological findings, including RBC/mm(2) and vessel distribution, were evaluated. To examine ischemic femoral head, 16 piglets were divided into two groups, with the control group having 8 piglets (involving 16 normal hips) and an ischemic group having 8 piglets (involving 16 hips with hyperabduction). In the ischemic group, MR imaging was performed on the hips in the hyperabduction immobilized persistently for 30 minutes. After MRI, the piglets were allowed to ambulate freely for 1 day and the same MR scanning was then repeated in a neutral position. The difference in enhancement ratio and speed of the femoral head between the control and ischemic group were evaluated. RESULTS: With regard to the end of normal growing long bone, the enhancement ratio of the metaphyseal spongiosa was greatest among all the anatomic regions (P < 0.001). The enhancement ratio of physeal cartilage was greater than that of epiphyseal cartilage (P < 0. 001), which was the lowest in all tissues (P < 0.001). The enhancement speed of the spongiosa was greater than that of physis but the difference was not significant (P > 0.05). The enhancement speed of physis was greater than that of epiphyseal cartilage (P < 0.05), which was the lowest among all the tissues (P < 0.05). The enhancement ratio and speed were found to be related to the histological findings, including RBC/mm(2) (R > 0.75) and distribution of vessels in the tissues. With ischemic femoral head, the enhancement ratios of physis, anterior part and posterior part of capital femoral epiphysis were significantly lower (P < 0.05) and enhanced more slowly (P < 0.05) than those of normal femoral head on dynamic Gd-enhanced MR imaging. On conventional Gd-enhanced SE T1WI, however, no apparent decrease in enhancement ratio and speed in ischemic hips was found (P < 0.05), when they were compared with those in the normal hips. CONCLUSIONS: Dynamic gadoteridol-enhanced MR imaging can reveal the blood supply in various anatomic regions of the end of normal growing long bone. It is more sensitive than conventional Gd-enhanced SE T1WI in the detection of early epiphyseal ischemia.

Magnetic resonance susceptibility weighted imaging in detecting intracranial calcification and hemorrhage.

BACKGROUND: Computed tomography (CT) is better than routine magnetic resonance imaging (MRI) in detecting intracranial calcification. This study aimed to assess the value of MR susceptibility weighted imaging (SWI) in the detection and differentiation of intracranial calcification and hemorrhage. METHODS: Enrolled in this study were 35 patients including 13 cases of calcification demonstrated by CT and 22 cases of intracerebral hemorrhage. MR sequences used in all the subjects included axial T1WI, T2WI and SWI. The phase shift (PS) of calcification and hemorrhage on SWI was calculated and their signal features on corrected phase images were compared. The sensitivity of T1WI, T2WI and SWI in detecting intracranial calcification and hemorrhage was analyzed statistically. RESULTS: The detection rate of SWI for cranial calcification was 98.2%, significantly higher than that of T1WI and T2WI. It was not significantly different from that of CT (P > 0.05). There were 49 hemorrhagic lesions at different stages detected on SWI, 30 on T2WI and 18 on T1WI. The average PS of calcification and hemorrhage was +0.734 +/- 0.073 and -0.112 +/- 0.032 respectively (P < 0.05). The PS of calcification was positive and presented as a high signal or the mixed signal dominated by a high signal on the corrected phase images, whereas the PS of hemorrhage was negative and presented as a low signal or the mixed signal dominated by a low signal. CONCLUSIONS: SWI can accurately demonstrate intracranial calcification, not dependant on CT. Being more sensitive than routine MRI in detecting micro-hemorrhage, SWI may play an important role in differentiating cerebral diseases associated with calcification or hemorrhage.

[Evaluation of whole body MRI and diffusion-weighted MRI in detecting intranodal lesions in patients with lymphoma].

OBJECTIVE: To evaluate the whole body MRI and diffusion-weighted MRI in detecting intranodal lesions in patients with lymphoma. METHODS: Whole body MRI and diffusion-weighted MRI (DWI) were performed in 23 patients with histologically proven lymphoma. A conventional coronal MRI scan from head to inguinal groove was done for whole body scanning. In the DWI, axial MRI scans were performed after segmentation based on SENSE technique, and all images were merged into whole body image reconstruction by software. RESULTS: 417 lymph nodes were detected by MRI in the 23 patients. The overall positive rate of whole body MRI and DWI was 79.1% and 89.7%, respectively. It was 70.9% versus 85.2% and 79.4% versus 90.1% for the lymph nodes of < 2 cm and 2-3 cm in diameter, with a significant difference between the two methods (P < 0.01). However, it was 94.7% versus 97.9% for the lymph nodes of > 3 cm in diameter, not significantly different between the two methods (P > 0.05). Both methods had similar sensitivity in detecting the lymph nodes in the neck, supraclavicular and infraclavicular fossae, mediastinum and axillary fossa. However, the positive rate of whole body MRI was 51.2%, 43.8% and 52.2%, significantly less sensitive than 83.7%, 71.9% and 87.0%, respectively, by DWI in detecting the lymph nodes in the retroperitoneal space, pelvic cavity and inguinal groove (all P < 0.01). CONCLUSION: Both whole body MRI and diffusion-weighted MRI have a relative high sensitivity in detecting intranodal lesions for patients with lymphoma, showing a certain value in clinical application.

[Correlation between magnetic resonance diffusion weighted imaging and cell density in astrocytoma].

OBJECTIVE: To evaluate the apparent diffusion coefficients (ADC) in magnetic resonance diffusion weighted imaging with echo-planar technique in depicting the tumor cellularity and grading of astrocytoma. METHODS: Thirty-four astrocytoma patients including 18 male and 16 female with age from 10 to 73 years (mean 38.4 years) were examined by MRI and eventually proved by surgical resection and pathological examination. Of them, 26 had low-grade (grade I, II) astrocytoma and 8 high-grade (grade III, IV) astrocytoma. ADC value of astrocytoma was determined on magnetic resonance diffusion weighted images. Cellularity of the astrocytoma was analyzed using Adobe Photoshop 7.0.1 software. RESULTS: The mean ADC value (in units of 10(-4) mm(2)/s) of the high-grade astrocytomas (7.34 +/- 2.95) was significantly lower than that of the low-grade astrocytomas (13.76 +/- 3.31) (t = 4.91, P < 0.001). The mean cellularity of the high-grade astrocytomas (19.81 +/- 9.73)% was significantly higher than that of the low-grade astrocytomas (4.74 +/- 2.96)% (t = 4.32, P = 0.003). ADC value of the astrocytoma was significantly and negatively correlated with its cellularity (r = -0.535, P = 0.001). CONCLUSION: ADC value of astrocytoma is significantly and negatively correlated with its cellularity. Magnetic resonance diffusion weighted imaging may well be highly potential in predicting the degree of astrocytoma.

[The study of magnetic resonance sialography in diagnosing parotid diseases].

OBJECTIVE: To study the feasibility of diagnosing parotid disease with magnetic resonance sialography (MRS) and to select the optimal scanning sequence. METHODS: Twenty-three patients with parotid gland disease and 5 normal adults received sialography using magnetic resonance imaging technique and several sequences (including IR-FSE, FSE, SS-IR-FSE, SS-FSE) were used. After first scanning, the patients were scanned respectively 3 and 10 minutes after buccal application of vitamin C. And MR images of duct obtained. The images of parotid duct system were analysed and evaluated according to their displaying effects. Qualitative diagnosis was made based on MRI and those diagnosis were compared with pathological diagnosis after operation. RESULTS: Images of MR sialography clearly displayed the main duct and its branches of parotid gland and the pathological changes of duct, such as narrow, expanded, stoppage. Of the scanning sequences, IR-FSE was superior to others in manifesting the parotid gland duct (P < 0.05). The performance of images after being given vitamin C did not significantly improve the displaying effect. The accurate rate of qualitative diagnosis was 95.6%. CONCLUSIONS: MR sialography can clearly display the parotid ducts and their pathological changes. The accurate rate of qualitative diagnosis of parotid disease was higher than that X-ray sialography.