Magnetic Resonance Exams Research Articles

Quantitative follow‐up of patients with multiple sclerosis using MRI: Technical aspects

A highly reproducible automated procedure for quantitative analysis of serial brain magnetic resonance (MR) images was developed for use in patients with multiple sclerosis (MS). The intracranial cavity (ICC) was identified on standard dual-echo spin-echo brain MR images using a supervised automated procedure. MR images obtained from one MS patient at 24 time points in the course of a 1-year follow-up were aligned with the images of one of the time points. Next, the contents of the ICC in each MR exam were segmented into four tissues, using a self-adaptive statistical algorithm. Misclassifications due to partial voluming were corrected using a combination of morphologic operators and connectivity criteria. Finally, a connectivity detection algorithm was used to separate the tissue classified as lesions into individual entities. Registration, classification of the contents of the ICC, and identification of individual lesions are fully automatic. Only identification of the ICC requires operator interaction. In each MR exam, the program estimated volumes for the ICC, gray matter (GM), white matter (WM), white matter lesions (WML), and cerebrospinal fluid (CSF). The reproducibility of the system was superior to that of supervised segmentation, as evidenced by the coefficient of variation: CSF supervised 45.9% vs. automated 7.7%, GM 16.0% vs. 1.4%, WM 15.7% vs. 1.3%, and WML 39.5% vs 52.0%. Our results demonstrate that this computerized procedure allows routine reproducible quantitative analysis of large serial MRI data sets.J. Magn. Reson. Imaging 1999;9:519–530. © 1999 Wiley-Liss, Inc.

Magnetic resonance imaging of neuroblastoma using current techniques

We evaluated the ability of current magnetic resonance (MR) scanning techniques to detect and stage neuroblastoma in children, using surgical and histopathologic correlation. We prospectively and retrospectively reviewed 16 MR examinations from 14 patients with neuroblastoma (13 patients) or ganglioneuroblastoma (1 patient) and compared these to computed tomography (CT) (5 patients) and pathology (all patients). Sequences included: precontrast T 1-weighted and T 2-weighted images, and gadolinium-enhanced T 1-weighted images. The study time for each MR exam was also calculated. Five primary tumors were intrathoracic paraspinous masses, eight were adrenal, and 1 was presacral. Neural foraminal invasion was demonstrated on MR in four of 14 patients. Three of the four patients had undergone CT and neural foraminal invasion was shown in one. Vascular encasement was demonstrated in five of 14 patients on MR images. Three of the five patients had undergone CT and vascular involvement was shown in two. All cases of neural foramina invasion and vascular encasement were proven at surgery. There were no false positive or false negative MR studies of neural foraminal invasion or vascular encasement. Bone marrow invasion was shown in two of 14 patients on MR images which were confirmed by bone marrow aspirate. No false negative cases of bone marrow invasion was shown. In one patient, CT considered one neuroblastoma to be adrenal in location which was correctly shown to be intrathoracic on MR. The mean study time for MR imaging was 49 min. Current MR techniques are accurate at detecting and staging neuroblastoma, and coverage of chest, abdomen, and pelvis can be performed in less than one hour.

Contrast-enhanced magnetic resonance imaging in a spinal epidural tumor model.

A spinal epidural tumor model was developed, using the VX-2 adenocarcinoma in rabbits, to assess the strengths and weaknesses of magnetic resonance (MR) as a cross-sectional imaging modality for the evaluation of epidural neoplastic disease. High-resolution MR images were acquired both before and after intravenous gadolinium chelate injection, assessing lesion detectability and efficacy of imaging technique. An adenocarcinoma tumor (VX-2) was produced in the epidural space of six New Zealand White rabbits and subsequently studied on a 1.5 tesla whole body MR scanner. VX-2 tumor tissue was removed from the thigh of a carrier rabbit, minced, and screened. Under fluoroscopic guidance, 0.2 mL of the tumor preparation was then injected into the epidural space of the experimental rabbits. The injection was performed at the L5-6 level using an epidural needle and polyethylene tubing sleeved within the needle. The rabbits were imaged using a circular small parts surface coil 5 to 15 days after the epidural injection. In all six animals, one complete MR exam was obtained within the time frame of days 9 to 11. T1- and T2-weighted axial scans were obtained before contrast injection, with the T1 scans acquired both with and without fat saturation. Postcontrast T1 scans also were obtained, using fat saturation, after the injection of 0.1 and 0.3 (cumulative dose) mmol/kg gadoteridol (Gd HP-DO3A; ProHance) in all animals. The film images were interpreted in a prospective fashion by a single neuroradiologist who was masked to imaging technique and contrast dosing. The digital data was analyzed by region of interest measurement. At the end of the imaging studies, the animals were sacrificed and the epidural lesion confirmed by gross and microscopic exam. On a prospective masked read of the MR films, epidural tumor was depicted best on postcontrast fat saturation T1-weighted scans using a cumulative contrast dose of 0.3 mmol/kg. Substantial contrast enhancement of the tumor was observed in all instances on postcontrast scans. The precontrast T1-weighted scan was least efficacious for lesion identification and differentiation from the compressed spinal cord. Depending on the pulse sequence used, one (T2-weighted) to three (T1-weighted without fat saturation) of the lesions could not be identified prospectively on precontrast scans. Lesion growth with time after implantation was chronicled by MR imaging, accompanied by progression of symptoms. On region of interest analysis, differentiation of epidural tumor from normal cord was greatest (11.6 +/- 6.1) on postcontrast scans using a cumulative contrast dose of 0.3 mmol/kg. The level of differentiation achieved was twice that of postcontrast scans using a contrast dose of 0.1 mmol/kg (5.9 +/- 3.6). These results were superior on statistical analysis to that with all other scan techniques (P = 0.002-0.0005). Cord and tumor could not be differentiated on the basis of signal intensity, with any statistical significance, using precontrast T1 and T2 scans. The lesions were confirmed in each animal by gross and microscopic exam. On inspection of the gross specimen, the tumors were noted to be located in the epidural space and to cause cord compression. On microscopic exam, the tumor was composed of epithelial cells that were moderately pleomorphic. In the New Zealand White rabbit, an epidural tumor could be created consistently using the described percutaneous approach. These lesions are suitable for MR imaging studies, examining lesion detectability and efficacy of imaging technique. The lesions created in the current study could not be diagnosed prospectively in all cases on precontrast T1 and T2 scans images. Postcontrast scans were most efficacious for diagnosis and lesion delineation, with high-dose (0.3 mmol/kg) scans superior to standard dose (0.1 mmol/kg).

Genetic basis of endocrine disease. 6. Molecular basis of familial human growth hormone deficiency.

T HE GENE encoding GH-N (GHl) and those genes encoding chorionic somatomammotropin (CSH1,2) hormones reside in a 50,000 base-pair (50 kb) gene cluster on human chromosome 17 (Fig. 1) (1). The GH2 gene also resides in this cluster and encodes a protein (GH-V) that is expressed in the placenta rather than in the pituitary and differs from the primary sequence of GH-N by 13 amino acids. The CSH1,2 genes encode proteins of identical sequences, whereas the CSH pseudogene (CSHPl) encodes a protein differing by 13 amino acids and contains a mutation that should alter its pattern of messenger RNA (mRNA) splicing and thus the primary sequence of the resulting protein (1, 2). The extensive homology (92-98%) between the immediate flanking, intervening, and coding sequences of these 5 genes suggests that this multigene family arose through a series of gene duplication events (1, 3, 4). These duplications are thought to have arisen from successive unequal recombinations between Alu family repeats. This method of gene amplification is analogous to the Alu-Alu recombinations that cause deletions of the human @globin and low density lipoprotein receptor genes (5, 6). Expression of the GHl gene is controlled by cis and truns factors. The former include the CAT and TATA promoter components located 85 and 30 bp, respectively, upstream from the GHl gene’s origin of transcription. In addition, there are cis sequences that bind the Pit-I transacting factor. Thus, Pit-l factor binds to and activates the promoters of the GHl and PRL genes and also affects differentiation of thyrotropes (7). The frequency of GH deficiency is estimated to range from l/4,000-l/10,000 in various studies (8-11). Most cases are sporadic and are assumed to arise from cerebral insults or defects that include cerebral edema, chromosome anomalies, histiocytosis, infections, radiation, septo-optic dysplasia, trauma, or tumors affecting the hypothalamus or pituitary (1). Magnetic resonance exams detect hypothalamic or pituitary anomalies in about 12% of patients who have isolated GH deficiency (IGHD) (12).

Detection of Lymphomatous Bone Marrow Involvement With Magnetic Resonance Imaging

Abstract We reviewed magnetic resonance (MR) staging examinations of 98 patients with malignant lymphoma who failed other therapy and were under evaluation for bone marrow transplantation. MR scan results were compared with blind posterior iliac crest aspirations and biopsies. Images of vertebral, pelvic, and femoral marrow were obtained using a standard T1-weighted, short repetition time (TR), short time to echo (TE) (TR700/TE22), spin-echo (T1-SE) method in 92 patients and short TI inversion recovery (STIR) technique (TR1,500/TE36/TI100) in all. On standard T1-SE sequence, normal marrow is bright due to the predominance of marrow fat, and tumor is dark. With STIR images, water containing tumor has a very high signal intensity in a dark (fat suppressed) background. Thirteen patients had positive MR scans and marrow biopsies, whereas 49 had negative MR scans and biopsies. Of 36 discordant MR/histology results, 10 had positive biopsies and negative MR exams; eight of these had microscopic infiltration (less than or equal to 5%) with tumor. MR detected marrow tumor either in the crests or elsewhere in 25 of 75 (33%) patients with negative study biopsies. We could confirm marrow involvement in 15 of these 25 (60%) by clinical methods. Therefore, up to one third of the patients evaluated with routine biopsies may have occult marrow tumor detectable by MR exam. In patients with negative marrow biopsies, especially those with Hodgkin's disease or intermediate to high-grade non-Hodgkin's lymphomas, MR scans found focal lesions distant from the crests. Biopsy better detected lower grade microscopic involvement. We conclude that optimal marrow staging of lymphoma patients incorporates both biopsy and MR imaging.

Detection of lymphomatous bone marrow involvement with magnetic resonance imaging [see comments

We reviewed magnetic resonance (MR) staging examinations of 98 patients with malignant lymphoma who failed other therapy and were under evaluation for bone marrow transplantation. MR scan results were compared with blind posterior iliac crest aspirations and biopsies. Images of vertebral, pelvic, and femoral marrow were obtained using a standard T1-weighted, short repetition time (TR), short time to echo (TE) (TR700/TE22), spin-echo (T1-SE) method in 92 patients and short TI inversion recovery (STIR) technique (TR1,500/TE36/TI100) in all. On standard T1-SE sequence, normal marrow is bright due to the predominance of marrow fat, and tumor is dark. With STIR images, water containing tumor has a very high signal intensity in a dark (fat suppressed) background. Thirteen patients had positive MR scans and marrow biopsies, whereas 49 had negative MR scans and biopsies. Of 36 discordant MR/histology results, 10 had positive biopsies and negative MR exams; eight of these had microscopic infiltration (less than or equal to 5%) with tumor. MR detected marrow tumor either in the crests or elsewhere in 25 of 75 (33%) patients with negative study biopsies. We could confirm marrow involvement in 15 of these 25 (60%) by clinical methods. Therefore, up to one third of the patients evaluated with routine biopsies may have occult marrow tumor detectable by MR exam. In patients with negative marrow biopsies, especially those with Hodgkin's disease or intermediate to high-grade non-Hodgkin's lymphomas, MR scans found focal lesions distant from the crests. Biopsy better detected lower grade microscopic involvement. We conclude that optimal marrow staging of lymphoma patients incorporates both biopsy and MR imaging.

Magnetic resonance analysis of suprasellar tumors of childhood.

A retrospective analysis of the magnetic resonance (MR) images in 53 pediatric patients with pathologically proven suprasellar tumors was performed, in an attempt to identify the characteristic MR features of these tumors and assess the capability of MR to predict a histologic differentiation. The tumors analyzed included 29 astrocytomas, 11 craniopharyngiomas, 4 germinomas, 3 pituitary adenomas with suprasellar extension, 2 teratomas, 1 spindle cell tumor, 1 primitive neuroectodermal tumor, 1 arachnoid cyst and 1 chordoma of the clivus with suprasellar extension. Thirty patients received intravenous Gd-DTPA as part of their MR exam. Certain MR features, while not pathognomonic, are quite helpful in the differentiation of craniopharyngiomas from chiasmatic/hypothalamic astrocytomas. Presence of a high signal intensity component on T1-weighted images, cyst formation with macrocystic predominance, irregular, heterogeneous solid portion, and smooth ring cyst wall enhancement represent the key characteristics of craniopharyngiomas. Solid predominance with microcysts, long T1 and T2 relaxation times, intense enhancement after contrast administration and extension along the posterior optic pathways are the typical MR findings of chiasmatic/hypothalamic astrocytomas. Presence of diabetes insipidus in correlation with the MR findings of a well-marginated, round or lobular tumor with prolonged T1 and T2 relaxation times, which enhances strongly after Gd-DTPA administration may be the clue in the diagnosis of suprasellar germinomas. Teratomas can be separated from other pediatric suprasellar neoplasms on the basis of internal heterogeneity with presence of fat, calcium and various soft tissue densities. Tumors invading the suprasellar cistern by extension are easily differentiated by identification of the primary site of origin. The above features, while not pathognomonic, are quite helpful in making a specific diagnosis.