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。     

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.     

Gadolinium enhanced MR imaging of vascular stents

The feasibility of obtaining in-plane magnetic resonance (MR) vascular images in the presence of a vascular stent and the value of infusing an MR contrast agent during imaging was assessed. Coronal and sagittal MR imaging at 1.5 T was performed on six dogs with tantalum aortic stents using single-section gradient echo (GRE) imaging and MR angiography techniques before and during intravenous infusion of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In-plane gradient echo (GRE) imaging and MR angiography clearly showed flow within the stented vessel as increased signal, with a minimum amount of stent-related artifact. Infusion of Gd-DTPA significantly increased the signal of flowing blood and allowed for better delineation of the stented aortic lumina. Our results demonstrate that in-plane GRE imaging and MR angiography can potentially be used as noninvasive methods for evaluating vascular patency in the presence of MR-compatible endovascular devices. In addition, Gd-DTPA infusion during MR vascular imaging clearly enhances the definition of flowing blood in the lumina of stented vessels.     

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     

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.     

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.     

Hemochromatosis of the pituitary gland: MR imaging

Magnetic resonance imaging of the pituitary gland in a patient with secondary hemochromatosis is described. On T1-weighted images, the anterior lobe had almost no signal intensity, and only the high-signal posterior lobe was seen. These findings are compatible with the distribution of iron deposition and clinical symptoms in hemochromatosis.     

1.5-T MR imaging of pituitary microadenomas: technical considerations and CT correlation

Thirty-seven patients with suspected pituitary tumors were evaluated prospectively with MR imaging at 1.5 T. MR detected a microadenoma at its correct location in all eight patients who underwent transsphenoidal surgery, while CT showed a focal abnormality in the correct location in only four of the eight patients. In patients who were clinically and endocrinologically considered to harbor a microadenoma, MR detected a focal pituitary signal abnormality in 83% and CT demonstrated a focal density abnormality in 42%. Infundibular displacement, focal gland convexity, and sellar-floor abnormality were seen equally well with CT and MR. MR imaging protocol included sagittal T1-weighted spin-echo, coronal inversion-recovery, and coronal spin-echo or cardiac-gated spin-echo images. Although inversion-recovery images were superior in detecting focal pituitary lesions, some microadenomas were better seen on T2-weighted images. Cardiac-gated spin-echo images showed focal pituitary lesions better than ungated images did. Our technique demonstrates MR's superior sensitivity to CT in detecting a pituitary microadenoma.     

Measurement of pituitary gland height with MR imaging

From sagittal magnetic resonance (MR) images with 10 mm slice thickness, the mean vertical height of the pituitary gland in 42 normal patients was found to be 5.4 +/- 0.9 mm. Computed tomographic (CT) scans in the coronal plane showed the same. Measurements of pituitary size in 13 patients with tumors using both CT and MR were also essentially equivalent. The ease, comfort, and accuracy of the MR pituitary measurement supports its use as the examination of choice for measuring pituitary height.     

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.     

The computed tomographic appearance of the normal pituitary gland and pituitary microadenomas.

With the use of axial and coronal computed tomography (CT), the authors compared the density, contrast enhancement, and dimensions of normal pituitary glands and pituitary microadenomas. The normal gland appears homogeneous, nearly isodense with brain tissue, and it enhances uniformly. Its upper surface is concave downward or flat and its height 2-7 mm. The cavernous sinuses, the third, fourth, and sixth cranial nerves, the infundibulum, and the adjacent carotid arteries are well demonstrated by CT. Abnormal height and upward convexity of the gland are reliable signs of prolactinoma; abnormal density and enhancement are suggestive signs. CT findings in prolactin- and ACTH-secreting tumors may differ. CT is more sensitive and more specific than polytomography in the diagnosis of pituitary adenoma.     

MR imaging of physiologic pituitary gland hypertrophy in adolescence

The authors describe a technique for dynamic incremental computed tomography (CT) of the neck with use of slow-power intravenous injection of contrast material. CT scans of the necks of 55 subjects were evaluated with this technique and were found to exhibit adequate opacification of the neck vessels. This method of contrast enhancement enables vessels to be confidently distinguished from enlarged lymph nodes or masses. It also provides information about the boundaries of masses, their vascularity, and their relationship to surrounding structures. In addition, the authors have optimized this technique by reducing contrast material volume while maintaining diagnostic quality.     

Gd-DTPA enhanced high resolution MR imaging of pituitary adenomas

Thirty-eight patients with surgically or biochemically confirmed pituitary adenomas were examined on a 1.5 T MRI system by means of spin echo technique with 3 mm slice thickness. T1 weighted sagittal and coronal sections were obtained before and after the administration of Gd-DTPA. Compared with the normal pituitary anterior lobe, 8% of the adenomas were hyperintense, 45% were isointense, 42% were hypointense and 5% were inhomogeneously intense. After Gd-DTPA administration, 13% enhanced to a greater degree, 10% to the same, and 57% to a lesser degree than the normal pituitary tissue. Twenty percent showed inhomogeneous enhancement. In 10%, there was evidence of adenoma only in the enhanced images. The delineation of the adenoma from the cavernous sinus was improved from 47% in unenhanced scans to 91% after Gd-DTPA administration.     

Normal pituitary gland: coronal MR imaging of infundibular tilt

To determine the prevalence of pituitary infundibular deviation or tilt as a normal variant, coronal magnetic resonance (MR) images of 50 patients who had been examined for reasons other than pituitary disease were evaluated retrospectively. Forty-six percent of the patients had a more or less pronounced tilt of the pituitary stalk. This tilt was due to developmental lateral eccentricity of the pituitary gland in relationship to the midline of the brain in 34% and to ontogenic eccentric insertion of the pituitary infundibulum off the midline of the gland in the other 12%. This high frequency of stalk deviation in patients without pituitary disease suggests that such displacement by itself should not be used to support the presence of pituitary microadenoma on MR images or computed tomograms.     

Gadolinium DTPA in a MR study of expansive lesions of the cranial base

Twenty-five patients were investigated by MR imaging in order to evaluate the diagnostic value of Gadolinium (Gd)-DTPA in skull-base tumors. The patients were studied with standard acquisition techniques (T1, mixed and T2-weighted images) without contrast medium. The images obtained were then compared with the T1-weighted images obtained after intravenous injection of Gd-DTPA. The contrastographic results in the different types of acquisition were evaluated. Thanks to the extraordinary increase in contrast resolution it provides, Gd-DTPA allowed the precise evaluation of the lesion and of its perfect spatial definition in all cases. Our experience demonstrated that Gd-DTPA considerably increases the sensitivity of the technique in this anatomical region. On the contrary, as regards the nature of the lesion, the signal did not significantly vary after the iv injection of Gd-DTPA in the various kinds of lesion. In addition to the important diagnostic advantages of Gd-DTPA, its excellent tolerability and the absence of side-effects must be stressed.     

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.     

Magnetic susceptibility artifact in spin-echo MR imaging of the pituitary gland.

PURPOSE: To evaluate the magnetic susceptibility effect on spin-echo MR images of the pituitary gland. METHODS: Air-in-water phantom experiments and studies in normal volunteers were performed using various sampling bandwidth (8.3-33.3 kHz) spin-echo sequences with the polarity of the readout gradient normal or reversed. RESULTS: Attachment of a sphenoid septum to the sellar floor was the major factor in the appearance of the inferior surface of the pituitary gland. Patterns of distortion and/or artifactual signal intensities, related to the presence or absence of the attachment, were accentuated on the images with narrower bandwidth. A "spearhead shape" deformity of the sphenoid sinus was observed both in the air-in-water phantom experiment, and when no sphenoid septum was present. When a sphenoid septum was present, two spearhead shapes side by side were present. High-intensity artifacts were seen where the sellar floor was misplaced into the pituitary gland. CONCLUSION: Knowledge of the patterns of distortion and high-intensity artifact is important in the diagnosis of pituitary lesions.     

Mucosa-associated lymphoid tissue lymphoma of the pituitary gland: MR imaging features

We report the MR features in a previously healthy patient with mucosa-associated lymphoid tissue lymphoma of the pituitary gland. The MR images showed a homogeneously enhancing solid mass in the sellar region and both parasellar regions; this mass extended through the bilateral foramina ovale along the third branches of the trigeminal nerves. The mass completely encircled the cavernous segments of both internal carotid arteries without narrowing the lumen. Gadopentetate dimeglumine-enhanced T1-weighted MR images showed homogeneous, strong enhancement of the mass.     

Dynamic contrast-enhanced MR imaging of the pituitary gland with fast spin-echo technique

Preliminary work has demonstrated that dynamic contrast material—enhanced magnetic resonance imaging improves the detection sensitivity for pituitary microadenomas. The authors present a new method of obtaining dynamic contrastenhanced pituitary images with a short TR/TE fast spin-echo technique. This approach allows acquisition of contrast-enhanced spin-echo images with high temporal and spatial resolution. The new technique is applied in a small group of patients and control subjects.