High-resolution MR imaging of pituitary microadenomas at 1.5 T: experience with Cushing disease

The MR images of 27 patients with clinically and biochemically suspected Cushing disease were evaluated retrospectively in a blinded fashion. The MR interpretation was compared with detailed operative diagrams and operative and pathologic reports. The examinations were performed on a 1.5-T MR system with thin-section sagittal and coronal T1-weighted (short TR/TE) images. Each pituitary half was considered separately (54 "halves"). Twenty-one pituitary halves were considered to have glandular abnormalities on MR. Compared with surgical findings, 17 MR findings were true positives and four were false positives (one pars intermedia cyst, three normal tissue). Of the 33 pituitary halves considered normal on MR, 26 were true negatives and seven were false negatives. MR had an overall sensitivity of 71% and a specificity of 87% for these adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas. A focal glandular hypointensity identified on coronal images was the most sensitive predictor of adenoma location. Sagittal images were not useful in either detection or localization. Upward convexity of the gland and deviation of the stalk were less useful indicators. Abnormalities of the sellar floor were the least reliable. In comparison with the capabilities of CT detection of microadenomas described in the current literature, it appears that high-field thin-section MR of the sella is the most sensitive imaging method for preoperative localization of ACTH-secreting adenomas in patients with Cushing disease.     

Prolactin-secreting pituitary microadenomas: inaccuracy of high-resolution CT imaging

Computed tomographic (CT) and surgical findings were correlated retrospectively in 51 patients with preoperative diagnoses of prolactin-secreting pituitary microadenomas. Thirty-nine had microadenomas at surgery. Twenty-three had identifiable discrete lesions. Of these, 21 had microadenomas and two did not; these two groups could not be distinguished reliably. Six patients with proven microadenomas had normal CT scans. Focal hypodense lesions, sellar floor erosion, infundibulum displacement, gland height greater than 8 mm, and an abnormal diaphragma sellae configuration are neither sensitive nor specific findings of microadenoma. A significant number of patients with proven microadenomas had few or none of these abnormalities. Thus, recognition of prolactin microadenoma may not be possible by CT alone, even with high-resolution direct coronal imaging.     

Evaluation of pituitary microadenomas with dynamic MR imaging.

PURPOSE: To evaluate the use of keyhole dynamic magnetic resonance (MR) imaging in the evaluation of women with borderline hyperprolactinemia. PATIENTS and METHODS: We investigated 30 patients (mean age 31.6+/-4.3 years) with moderate hyperprolactinemia and clinically suspected microadenomas on T1-weighted spin echo (SE) sequences (repetition time (TR)/echo time (TE) 625/15 ms) with keyhole dynamic imaging and contrast enhancement of the pituitary gland. The probability of lesion presence according to MR criteria was ranked on a five-grade scale and compared with standard examinations of the hypophysis before and after intravenous administration of contrast media. RESULTS: The probability for lesion presence showed a trend toward lower scores on standard SE sequences and higher scores with dynamic imaging (P=0.067). CONCLUSION: Dynamic keyhole imaging of the pituitary gland could help establish a diagnosis of microadenomas with a higher probability.     

MR imaging of the brachial plexus: comparison between 1.5-T and 3-T MR imaging: preliminary experience

Objective  

To compare 1.5-T and 3-T magnetic resonance (MR) imaging of the brachial plexus.     

动态MRI对垂体微腺瘤的诊断价值

目的　评价匙孔动态MR对垂体微腺瘤的应用价值。方法　回顾性分析临床有头痛、闭经、泌乳、过度肥胖或肢端肥大等症状的 53例经手术和临床证实的垂体微腺瘤的MR影像资料 ,由2位有经验的影像科医师在相互隔离、不知道临床及实验室资料的情况下对 53例的动态MRI、MR传统增强及冠状面平扫T1 WI分级 ,并得出一致结果。分级标准为 :0级 :垂体内未见异常信号 ;Ⅰ级 :垂体内信号不均匀 ;Ⅱ级 :垂体内见有粟粒、结节或片块状的异常信号区。将动态MR、MR传统增强及平扫图像分级的结果进行比较。结果　本组动态MR垂体内未见异常信号者 (0级 ) 1例 ,垂体内信号不均匀者 (Ⅰ级 ) 2 9例 ,垂体内见有粟粒、结节或片块状的异常信号区者 (Ⅱ级 ) 2 3例 ;MR传统增强 0级 2 6例 ,Ⅰ级 1 7例 ,Ⅱ级 1 0例 ;MR平扫 0级 39例 ,Ⅰ级 1 0例 ,Ⅱ级 4例。本组动态MR检出率为 98 1 % ;传统增强MR检出率为 51 9% ;MR平扫检出率为 2 6 4%。行×列 χ2 检验 ,P <0 0 0 5。表明动态MR能明显提高微腺瘤显示的级别 ,且差异有非常显著性意义。结论　动态MR能明显提高垂体微腺瘤诊断的可靠性 ,降低MR图像模棱两可的出现率。临床怀疑垂体微腺瘤而MR平扫阴性者 ,动态MR应列为常规检查     

Time-of-flight MR angiography: comparison of 3.0-T imaging and 1.5-T imaging--initial experience

Intracranial three-dimensional time-of-flight (TOF) magnetic resonance (MR) angiography was performed in seven healthy volunteers and eight patients with both 1.5-T and 3.0-T MR systems with standard and high spatial resolutions (true voxel sizes, 0.48 x 0.75 x 2.00 mm and 0.30 x 0.44 x 1.00 mm, respectively). Superior image quality and significantly better depiction of small vessel segments and vascular disease were observed at high-spatial-resolution 3.0-T TOF MR angiography but not at standard 1.5-T or standard 3.0-T TOF MR angiography (P <.01, respectively). Intracranial high-spatial-resolution TOF MR angiography at 3.0-T imaging provides diagnostic improvement in studies of cerebrovascular disease.     

Diffusion-tensor fiber tractography: intraindividual comparison of 3.0-T and 1.5-T MR imaging

PURPOSE: To prospectively evaluate the depiction of brain fiber tracts at 3.0- versus 1.5-T diffusion-tensor (DT) fiber tractography performed with parallel imaging. MATERIALS AND METHODS: Institutional review board approval was obtained, and each subject provided written informed consent. Subjects were 30 healthy volunteers (15 men, 15 women; mean age, 28 years; age range, 21-46 years). Single-shot spin-echo echo-planar magnetic resonance (MR) sequences with parallel imaging were applied. Four fiber tracts were reconstructed: corticospinal tract (CST), superior longitudinal fasciculus (SLF), corpus callosum (CC), and fornix. Two neuroradiologists compared 3.0- and 1.5-T tractography in terms of fiber tract depiction by using five depiction scores (scores 0-4) and numbers of reconstructed tract fibers and in terms of lateral asymmetry in the CST by using numbers of reconstructed fibers. The Wilcoxon signed rank test was applied for statistical analysis. RESULTS: Visual scores for both CST hemispheres (P < .001), the right SLF (P = .005), the CC (P = .01), and the right fornix (P = .04) were higher at 3.0-T DT tractography. Larger numbers of CST (right, P = .008; left, P < .001), SLF (right, P = .001; left, P = .02), and fornix (bilaterally, P = .02) tract fibers were depicted at 3.0 T. The asymmetry index for the CST was lower (P < .001) at 3.0 T. Visual scores for the left SLF and the left fornix and numbers of CC tract fibers were not significantly different. CONCLUSION: Depiction of most fiber tracts was improved at 3.0-T DT tractography compared with depiction at 1.5-T tractography.     

MR imaging of pituitary adenoma: CT, clinical, and surgical correlation

Twenty-five patients with suspected pituitary adenoma were evaluated prospectively with CT and MR. Nine patients underwent transsphenoidal surgery, and three of these showed a documented decrease in size of mass on bromocriptine therapy. CT was more sensitive than MR for detecting focal lesions (seven vs three) and sellar-floor erosion (12 vs six). MR was superior to CT in identifying infundibular abnormalities (seven vs six), focal abnormalities of the diaphragma sellae (10 vs seven), cavernous sinus invasion (four vs two), and optic chiasm compression (six vs zero). Thus, MR may be the procedure of choice for optimal identification and localization of macroadenoma. For patients with suspected microadenoma, however, this preliminary series indicates that CT remains the radiographic procedure of choice.     

MR of corticotropin-secreting pituitary microadenomas.

PURPOSETo assess the accuracy of MR in the preoperative identification of corticotropin-secreting pituitary microadenomas.METHODSTwenty-six patients with clinical and biochemical evidence of pituitary-driven Cushing disease in whom MR of the seller region was performed were selected for this study. The MR examinations were retrospectively evaluated by a neuroradiologist who was aware of the presence of an adenoma at surgery but not of location and size of the lesion.RESULTSConsidering the whole group of MR examinations performed either without (n = 26) or without and with intravenous injection of gadopentetate dimeglumine (n = 16), overall 20 MR studies were judged to show disease. Seventeen of 26 microadenomas were adequately shown and located by MR (true-positive, 65.4%). In three cases the sides of the microadenomas were misjudged (false-positive, 11.5%). Six patients had negative MR studies (false-negative, 23%). Twelve of the 16 patients studied after gadopentetate dimeglumine injection had true-positive MR findings (75%).CONCLUSIONSIn our experience the accuracy of MR in detecting corticotropin-secreting microadenomas as small as 2 to 3 mm is 65% to 75%. Although precontrast images provide diagnostic information, the microadenoma can be better seen with administration of contrast material.     

Acute cervical spine trauma: evaluation with 1.5-T MR imaging

Twenty-one patients with acute neurologic deficits following cervical spine trauma were evaluated with magnetic resonance (MR) imaging (n = 21), computed tomography enhanced with intrathecal contrast material (CT myelography) (n = 18), myelography (n = 13), cervical spine radiography (n = 21), and intraoperative sonography (n = 7). MR imaging proved superior to other modalities in demonstrating parenchymal spinal cord injuries and cervical intervertebral disk herniation. Although both T1- and T2-weighted studies appear necessary to evaluate the anatomic relationship of the spinal cord, thecal space, intervertebral disks, and surrounding osseous and ligamentous structures, T2-weighted sequences were more sensitive than T1-weighted studies for detection of spinal cord injury. CT myelography was superior to MR imaging in demonstrating cervical spine fractures. In most cases, myelography revealed no information that was not apparent from both CT and MR imaging studies. Preliminary experience with MR imaging of acute cervical spine trauma suggests that it should be the study of choice in symptomatic patients who are otherwise clinically stable. CT may still be required in selected patients to evaluate complex fractures.     

MRI同层动态增强对垂体微腺瘤的诊断价值

目的:分析垂体微腺瘤的MRI同层动态增强特征。方法:对60例临床怀疑为垂体微腺瘤的病人行同层动态增强MRI扫描,并绘出时间-信号强度曲线图。结果:60例病人中共检出垂体微腺瘤39例,同层动态增强后,垂体微腺瘤的MRI表现为圆或椭圆形的低或稍低信号,似“充盈缺损”;垂体微腺瘤的最大信号强度,多出现在注入对比剂后32-96s,以64s最明显。结论:同层MRI动态增强对垂体微腺瘤的诊断有较高价值。     

Adnexal masses: MR imaging observations at 1.5 T, with US and CT correlation

To assess the role of 1.5-T magnetic resonance (MR) imaging in evaluation of the adnexa, 43 consecutive examinations that revealed 61 adnexal masses were retrospectively reviewed. T1- and T2-weighted images in coronal, axial, and/or sagittal planes were included. Available ultrasound (US) (n = 30) and/or computed tomographic (CT) (n = 9) scans were then correlated with the MR images. On T2-weighted images at least part of all adnexal masses was of higher signal intensity than surrounding muscle and adipose tissue, and therefore the adnexal masses were best seen with these sequences. T1-weighted imaging improved tissue characterization by revealing signal characteristics of fat in teratomas and characteristics of blood in endometriomas or hemorrhagic cysts, pelvic inflammatory disease, ovarian carcinomas, serous cystadenomas, and teratomas. MR imaging provided additional information or increased diagnostic confidence in 25 of 30 patients who underwent US or CT. MR imaging is a promising problem-solving modality after US in the study of adnexal abnormalities.     

MR imaging of prolactin-secreting microadenomas

Eight proven and three presumed prolactin-secreting microadenomas were studied with magnetic resonance (MR) imaging. All 11 cases had CT evidence of a tumor. Technical factors for MR included use of 1.3-1.5 T MR systems, 3 mm slice thickness, short repetition time (TR) (T1-weighted) and long TR (T2-weighted) spin-echo pulse sequences. Six microadenomas were demonstrated with MR. Four tumors had a long T1 and long T2, one had a long T1 and short T2, and one bromocriptine-treated tumor had a short T1 and short T2. MR failed to delineate the focal mass within the pituitary gland in the other five patients. The cause of the MR failures was not determined; however, tumor size did not appear to be a factor. MR signals arising from microadenomas are variable and possibly related to the activity of the prolactin-secreting cells. Correlation of findings from MR imaging, spectroscopy, and electron microscopy may lead to an understanding of the variable MR appearance of microadenomas.     

Gadolinium DTPA enhanced MR imaging of ACTH-secreting microadenomas of the pituitary gland

Gadolinium diethylenetriamine pentaacetic acid (DTPA) enhanced magnetic resonance imaging was performed in eight patients with Cushing disease and surgically proven pituitary microadenomas. A 1.5 T scanner was used with 3 mm contiguous slices. Short repetition times (TR), short echo times (TE), and long TR, long TE sequences were obtained before and serially after intravenous administration of Gd-DTPA. Three of eight (38%) microadenomas were undetectable both without and with Gd-DTPA: one post-Gd-DTPA scan was false positive on the side opposite the adenoma. Hemihypophysectomy based on a petrosal sinus adrenocorticotropic hormone (ACTH) gradient cured all three patients. Two microadenomas (25%) were visible as hypointense foci following Gd-DTPA but not on unenhanced scans. The remaining three microadenomas (38%) were seen before and after Gd-DTPA on T1-weighted images. In this small series of ACTH-producing microadenomas, one-third were seen on unenhanced 1.5 T scans, one-third were seen only after Gd-DTPA, and one-third were not imaged even with Gd-DTPA enhancement.     

Three-dimensional CT and MR imaging in congenital dislocation of the hip: clinical and technical considerations

Three-dimensional (3D) CT and 3D magnetic resonance (MR) imaging were performed in four patients with congenital dysplasia of the hip. Two patients were studied by 3D CT and two by 3D MR. Prior to volume segmentation, two-dimensional (2D) MR image preprocessing was used to correct for nonuniform signal intensity distribution from local variations in field strength and coil response. An unsharp mask of the original MR scan was computed by extreme blurring of the image to suppress the details of the object. The unsharp mask was divided into the image on a pixel-by-pixel basis. For improved object contrast first and second echo images were combined in a 1:2 ratio. To add an additional feature for volume segmentation, 2D MR image homogeneity was computed based on 3 X 3 pixel neighborhoods. Volume segmentation was performed using one feature for CT, i.e., attenuation range, and two features for MR, i.e., signal intensity and image homogeneity range. Three dimensional CT and 3D MR demonstrated the 3D relationships of femoral heads and acetabula. Three-dimensional CT was limited to patients who had ossified femoral heads, whereas 3D MR demonstrated the cartilaginous femoral head. The extent of acetabular coverage on which the mode of therapy is based was shown. Three-dimensional MR permitted imaging without gonadal irradiation. The 2D MR image preprocessing described here should provide even better results in objects with greater contrast, i.e., nonosseus structures, and those of larger size with relation to image degradation from partial volume effect.     

Evaluation of the acetabular labrum at 3.0-T MR imaging compared with 1.5-T MR arthrography: preliminary experience

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. The purpose of this study was to prospectively compare imaging of the acetabular labrum with 3.0-T magnetic resonance (MR) imaging and 1.5-T MR arthrography. Eight patients (four male, four female; mean age, 38 years) with hip pain suspicious for labral disease were examined at both MR arthrography and MR imaging. Presence of labral lesions, paralabral cysts, articular cartilage lesions, subchondral cysts, osteophytes, and synovial herniation pits was recorded. There was arthroscopic correlation of findings in five patients. MR imaging depicted four surgically confirmed labral tears that were identified at MR arthrography, as well as one that was not visualized at MR arthrography. MR imaging helped identify all other pathologic conditions that were diagnosed at MR arthrography and helped identify one additional surgically confirmed focal articular cartilage lesion. These results provide encouraging support for evaluation with 3.0-T MR imaging over 1.5-T MR arthrography.     

Diffusion tensor MR imaging and fiber tractography: technical considerations

This second article of the 2-part review builds on the theoretic background provided by the first article to cover the major technical factors that affect image quality in diffusion imaging, including the acquisition sequence, magnet field strength, gradient amplitude, and slew rate as well as multichannel radio-frequency coils and parallel imaging. The sources of many common diffusion image artifacts are also explored in detail. The emphasis is on optimizing these technical factors for state-of-the-art diffusion-weighted imaging and diffusion tensor imaging (DTI) based on the best available evidence in the literature. An overview of current methods for quantitative analysis of DTI data and fiber tractography in clinical research is also provided.     

MR imaging of the wrist: comparison between 1.5- and 3-T MR imaging--preliminary experience

Institutional review board approval and informed consent were obtained from 25 healthy volunteers and 15 consecutive patients with chronic wrist pain or suspected carpal mass, and 1.5- and 3-T magnetic resonance (MR) imaging of the wrist was prospectively performed with comparable sequence parameters and surface coils of the same geometric design. Imaging protocols at both field strengths included a T1-weighted spin-echo sequence, two intermediate-weighted fast SE sequences with different echo times and with and without fat saturation, and a three-dimensional fast field-echo sequence. The contrast-to-noise ratio (CNR) between muscle and bone and between bone and cartilage was calculated for both field strengths. The visibility of various anatomic structures, including the triangular fibrocartilage complex, carpal ligaments, nerves, and cartilage, was analyzed with a four-point grading scale. CNRs were significantly higher on 3-T MR images than on 1.5-T MR images (P < .001; analysis of variance) for all sequences. Visibility of the triangular fibrocartilage complex and intercarpal ligaments and cartilage was significantly better on 3-T MR images than on 1.5-T MR images (paired sign test).