MR Imaging Parameters Research Articles

Behavioural recovery correlated with MRI in a rat experimental stroke model

Primary objective : To characterize a necrotic lesion using MRI and motor recovery using behavioural methods. Research design : Stroke model based on two steps: (1) development of a lesion using MR-imaging parameters and (2) behavioural recovery. Methods and procedures : Seventy male Sprague-Dawley rats were used. A focal lesion of the right sensorimotor cortex was induced photochemically. Main outcomes and results : The maximum volume of oedema and the lesion damage was reached by ¨ 6 hours. In the lesion area, the apparent diffusion coefficient (ADC) increased from 6 hours, then decreased from 24 hours. All animals spontaneously recovered motor function by day 10, despite the continued presence of the cortical lesion. Conclusions : The results show that this model mimics a core lesion, as well as the late phase in a human stroke episode. This model might be used for longitudinal study of the basic mechanisms of motor recovery.

Bone marrow transplantation in patients with multiple myeloma: prognostic significance of MR imaging.

This study in myeloma patients treated with myeloablative therapy and bone marrow transplantation assessed the prognostic value of MR imaging before and after treatment of the bone marrow and the prognostic value of an index reflecting changes on MR images obtained before and after treatment. MR images (T1-weighted images before and after injection of gadolinium and T2(*)-weighted images) of the spine and pelvis were obtained 1 month before and 1 month after marrow transplantation in 25 consecutive patients with stage III myeloma. Pre- and posttreatment MR imaging patterns of marrow involvement (normal, focal, diffuse), number of focal lesions, and a "marrow evolution index" (0-8 on the basis of comparison of the lesions [number, size, contrast enhancement] and of the surrounding marrow background on pre- and posttreatment MR images) were determined. Hematologic and MR imaging parameters were correlated with the quality of response to treatment (complete versus partial remission) and with relapse-free and overall survival. Response quality did not differ among categories of patients determined on the basis of MR images. Individual MR imaging parameters did not correlate with response duration and survival. Patients with a low marrow evolution index had significantly longer relapse-free (p < 10(-3)) and overall survival (p = 0.005) than patients with a high index. Individual MR imaging parameters before and after treatment had no prognostic significance in our series of myeloma patients treated with marrow transplantation. Comparison of MR images before and after treatment using a marrow evolution index may help predict response duration and survival.

Angiogenesis of cervix carcinoma. Contrast enhanced dynamic MRI, histologic quantification of capillary density and lymphatic system infiltration

It was the aim of this project to examine (i) the relationships between contrast-enhanced dynamic MR imaging derived characteristics and histologic microvessel density counts--a recognized surrogate of tumor angiogenesis--from tumors in patients with primary or recurrent cancer of the uterine cervix, and (ii) to correlate these parameters with lymphatic involvement (i.e. lymphatic channels) to assess tumor biological aggressiveness in terms of lymphatic spread. Pharmacokinetic MR imaging parameters (amplitude A, exchange rate constant k21) were derived from contrast-enhanced dynamic MR imaging in thirty-three patients with biopsy proven cancer of the uterine cervix. The pharmacokinetic MR imaging characteristics were correlated to histologic capillary density counts obtained from whole mount specimen. In addition, these data were correlated to the angiogenic activity as a marker for lymphatic system involvement. Pharmacokinetic MR imaging derived parameters (A, k21) showed a weak but significant (p < 0.05) correlation with microvessel density counts. Lymphatic involvement was more comprehensively assessed by the pharmacokinetic parameter k21 compared with histologic microvessel density, resulting in a significantly (p < 0.05) higher overall accuracy (85% vs. 64%), sensitivity (83% vs. 54%), and comparable specificity (89% vs. 89%), respectively. Our first results show that the signal-time curves measured by contrast-enhanced MR imaging are only in part influenced by microvessel density. In addition, MR imaging derived characteristics may assess tumor biological aggressiveness in terms of lymphatic spread (i.e. lymphatic channels) more comprehensively than histologic microvessel density in patients with primary or recurrent cancer of the uterine cervix.

SOFT-TISSUE SARCOMA OF THE EXTREMITIES: MR Appearance of Post-Treatment Changes and Local Recurrences

MR imaging has the potential to provide valuable insights into intratumoral changes following preoperative therapy and has proven beneficial in the diagnosis of recurrent soft-tissue sarcoma of the extremities and differentiation of recurrence from postsurgical/postradiation changes. As advances occur in surgical and adjuvant treatment programs, further refinements of qualitative and quantitative MR imaging parameters should continue to enhance the role of MR imaging in the post-treatment evaluation of patients with soft-tissue sarcoma of the extremities.

MAGNETIC RESONANCE IMAGING OF THE MENISCUS: Advanced Concepts

Magnetic resonance imaging plays a valuable role in the evaluation of the full range of meniscal pathology including the primary diagnosis of meniscal tear, the detection of recurrent tear after resection or repair, and the demonstration of associated injuries and complications. The accuracy of MR imaging in meniscal diagnosis is dependent on the appropriate choice of MR imaging pulse sequences, imaging parameters, and diagnostic criteria. The importance of small details such as protocol parameters and image photography should not be underestimated. The role of new techniques including fast imaging sequences, three-dimensional imaging, and MR arthrography in improving meniscal diagnostic performance is under investigation and appears promising.