MR imaging of the pituitary gland in infants and children: changes in size, shape, and MR signal with growth and development.

It has been reported that on MR images of the brain in neonates the entire pituitary gland is hyperintense. This is quite different from the well-established observation that portion is isointense. To better understand the development of the neonatal pituitary gland, we studied the timing and magnitude of changes in the size, shape, and MR signal of the pituitary gland in early childhood and infancy. The study included 76 infants and children ages 3 days to 4 years old. In each MR study, the signal intensity of the pituitary gland on T1-weighted coronal (n = 24) and sagittal (n = 76) images was compared with the signal intensity of the pons by using region-of-interest methods. The size and shape of the pituitary glands were recorded. Statistical comparisons were made for signal intensity and size of the pituitary gland between boys and girls and among age groups. The results showed that the MR signal of the posterior lobe remained hyperintense relative to the pons for all age groups represented in our study (through 4 years). However, the signal intensity of the anterior lobe gradually diminished and by approximately age 2 months was isointense with the pons. Thus, by approximately age 2 months the MR signal intensity of the infant's pituitary gland has changed from being entirely hyperintense (as seen in neonates) to isointense in the anterior lobe and hyperintense in the posterior lobe (as seen in adults). In the first 2 months of life the pituitary gland is bulbous in shape; later it has a flatter upper surface. We found no significant changes in the length or signal intensity of the pituitary gland; no differences among sexes in size, shape, or signal intensity were demonstrated. Findings of a bulbous pituitary gland and high MR signal of the entire pituitary are normal in neonates up to 2 months of age. After that, the gland gradually flattens and the MR signal of the anterior lobe decreases until it has characteristics similar to the adult pituitary. Lack of high signal or discovery of a small pituitary gland in a neonate should alert the radiologist to the possibility of pituitary malformation or dysfunction.     

Sequential MR enhancement pattern in normal pituitary gland and in pituitary adenoma.

PURPOSETo measure and evaluate the temporal enhancement characteristics of the normal pituitary gland and pituitary adenoma.METHODSThirty healthy subjects and 10 patients with sellar pituitary adenomas were studied prospectively using dynamic MR imaging with a 5- or 10-sec temporal resolution during a bolus injection of gadolinium.RESULTSQualitative visual analysis demonstrated a consistent sequential pattern of pituitary enhancement in which the posterior lobe enhanced earlier than the anterior lobe by approximately 35 sec. Quantitative analysis revealed that posterior lobe enhancement occurred 9.8 +/- 1.5 sec (mean +/- SEM) before the anterior lobe in healthy subjects, whereas tumor enhancement occurred significantly before the anterior lobe but only slightly before the posterior lobe in patients with adenomas.CONCLUSIONThe sequential enhancement pattern of the normal pituitary gland was found to be consistent with its vascular anatomy. In contrast to previous reports, pituitary adenomas were found to enhance earlier than the anterior lobe. These results suggest that pituitary adenomas have a direct arterial blood supply, similar to that of the posterior pituitary lobe.     

Normal pituitary gland: changes in shape, size, and signal intensity during the 1st year of life at MR imaging

Magnetic resonance images of the pituitary glands in 48 endocrinologically normal neonates and infants were analyzed to determine the changes in pituitary gland size, shape, and signal intensity that occur during the 1st year of life. A progressive increase in the length--but not height--of the gland was seen throughout the 1st year. When corrections for total brain size were made, the pituitary gland was found to diminish in relative cross-sectional area throughout infancy. Upward convexity of the gland was seen in 63% of neonates less than 1 month of age, but in only 4% of infants older than 2 months. Hyperintensity of the adenohypophysis relative to the brain stem was visualized on T1-weighted images in 18 of the 24 (75%) neonates and infants less than 2 months old; this appearance was never seen in older infants. An area of high signal intensity was visualized in the posterior pituitary in 32 of 48 cases (67%), and its visualization was unrelated to age. The neonatal and young infant pituitary gland is thus significantly rounder, brighter, and relatively larger during the first 2 months of life than in later infancy.     

Transection of the pituitary stalk: development of an ectopic posterior lobe assessed with MR imaging

Magnetic resonance (MR) imaging was performed in ten patients with pituitary stalk transection who had idiopathic pituitary dwarfism. Contiguous sagittal T1-weighted images were obtained in all cases, and, in some, axial or coronal images were taken for further evaluation. On MR images, normal anterior and posterior lobes of the pituitary gland can be clearly differentiated because the posterior lobe has a characteristic high intensity on T1-weighted images. In the ten patients, the high-intensity posterior lobe was not seen, but a similar high signal intensity was observed at the proximal stump in seven patients. This high-intensity area is the newly formed ectopic posterior lobe, which secretes antidiuretic hormone just as the posterior lobe would. When the ectopic lobe completely compensates for the impaired posterior lobe, endocrinologic data indicate normal posterior lobe function. However, MR imaging can reveal the transection of the pituitary stalk and formation of the ectopic lobe.     

Pituitary adenomas and normal pituitary tissue: enhancement patterns on gadopentetate-enhanced MR imaging

A dynamic study of magnetic resonance (MR) imaging was used to obtain successive heavily T1-weighted coronal images (spin-echo [SE] 100/15 [repetition time msec/echo time msec]) of normal pituitary glands and pituitary adenoma immediately after patients were given an intravenous bolus injection of gadopentetate dimeglumine. The images were obtained every minute for 5-8 minutes at 1.5 T. Usual T1-weighted images (SE 600/15) were also obtained before and after the dynamic study was performed. The study group consisted of 18 patients, 10 with normal pituitary glands, and eight with pituitary adenoma. Normal pituitary glands showed maximum enhancement on the first or second image following the administration of gadopentetate dimeglumine, followed by gradual signal reduction through the later images, whereas pituitary adenomas reached a peak of enhancement later and showed slower signal reduction than normal pituitaries. The difference of enhancement patterns between the normal pituitary gland and the pituitary adenoma produced prominent image contrast on the first or second image after administration of gadopentetate dimeglumine, which improved the visualization of one microadenoma and four normal pituitary glands that had been displaced by large adenomas. Dynamic MR imaging is a useful diagnostic procedure not only for detection of microadenomas, but also for visualization of pituitary glands that have been displaced by large pituitary adenomas.     

Post-traumatic diabetes insipidus: MR demonstration of pituitary stalk rupture

We report the magnetic resonance findings in a case of post-traumatic diabetes insipidus (DI). They consisted of pituitary stalk rupture shown on both coronal and sagittal planes with associated disappearance of the normal high signal intensity of the posterior lobe on T1 images. This last sign, previously described in nontraumatic DI, appears to represent a finding indicating nonfunctioning neurohypophysis.     

The hypoglossal canal: normal MR enhancement pattern.

PURPOSETo review the anatomy of the hypoglossal canal and present the normal precontrast and postcontrast MR appearance of axial posterior fossa images.METHODSThirty-one axial MR examinations of the normal posterior fossa were retrospectively reviewed.RESULTSThe hypoglossal canals are well seen on 3-mm-thick axial MR images of the posterior fossa (28 [90%] of 31 patients). Symmetric intense intracanalicular enhancement after intravenous administration of gadopentetate dimeglumine is routine, typically with minor anterior extension into the nasopharyngeal region (28 [100%] of 28). A linear filling defect traversing the enhanced canal often is seen (21 [75%] of 28) and may represent hypoglossal nerve rootlets. Circumferential enhancement of the meninges at the level of the foramen magnum was a common finding (19 [64%] of 28).CONCLUSIONEnhancement within the hypoglossal canal with anterior extension beneath the skull base is a normal finding. This pattern is characteristic enough on MR imaging to aid interpretation of skull base lesions and to exclude the possibility of a mass within the hypoglossal canal.     

Normal pituitary stalk size in children: CT study

A retrospective study was undertaken of 1005 normal contrast-enhanced head computed tomographic (CT) scans in children to determine normal standards for pituitary stalk diameter, basilar artery diameter, and their ratio for age and gender. The pituitary stalk enlarges with age, and girls have larger stalks than do boys after age 8. The pituitary stalk-to-basilar artery ratio is easily estimated visually. Ratios greater than or equal to 1 are unusual in normal children. A ratio greater than or equal to 1 should prompt direct measurement of the stalk and comparison with age-matched normal values. If the stalk measurement is greater than 2 SD above the age-matched mean, it is presumably abnormal and deserves further evaluation for numerous possible pathologic conditions including histiocytosis X, pituitary adenoma, hypothalamic lesions, Rathke cleft cysts, metastases, sarcoidosis, hypothyroidism, and infection.     

Size and shape of the pituitary gland during pregnancy and post partum: measurement with MR imaging

Cranial magnetic resonance (MR) imaging was performed in 38 pregnant and postpartum women and 30 nonpregnant age-matched control subjects to establish standards for pituitary gland size and shape during this period. Gland height and infundibulum width were measured on midline T1-weighted sagittal images. Gland convexity or concavity was graded qualitatively. Throughout pregnancy, gland height increased linearly by approximately 0.08 mm/wk. No gland exceeded 10 mm in height during pregnancy. Increases in gland convexity also correlated with progression of pregnancy. The largest glands were seen in the immediate postpartum period; during this period, five of 12 glands measured 10.0-11.8 mm. Beyond the first week post partum, glands rapidly returned to normal size, apparently regardless of the status of breast-feeding. The mean diameter of the infundibulum was 2.2 mm (range, 0.8-4.0 mm). The pituitary gland enlarges throughout pregnancy but should probably not exceed 10 mm during most of this period. Size of up to 12 mm may be acceptable immediately post partum.     

Gd-DTPA-enhanced MR imaging of pituitary macroadenomas.

In a study comprising 40 patients with pituitary macroadenomas, MR imaging was performed before and after administration of Gd-DTPA. Before contrast administration T1- and T2-weighted images were obtained, and after the injection, frontal and/or sagittal T1-weighted images. Tumour extension and delineation, relationship to adjacent structures, and signal intensity patterns were evaluated. Compared with pre-contrast T1-weighted images only, post-contrast images provided considerable additional information, but not infrequently this information could also be extracted from pre-contrast T2-weighted images. Post-contrast images were superior regarding the tumour relationship to the cavernous sinus and to the normal pituitary tissue. T2-weighted images were helpful in the diagnosis of degenerative changes, in particular intratumoural haemorrhage. A positive correlation was found between the T2 value (from dual echo sequences) and the degree of enhancement in areas with an appearance of solid tumour tissue, and the enhancement was significantly lower in GH-secreting tumours than in non-secreting ones. It is concluded that the use of Gd-DTPA is often justified in pituitary macroadenomas, particularly in pre-operative evaluation.     

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.     

MR imaging of hepatocellular carcinoma: relationship between lesion size and imaging findings, including signal intensity and dynamic enhancement patterns

PURPOSE: To assess the relationship between lesion size and MR imaging findings of pathologically-proven hepatocellular carcinoma (HCC). MATERIALS AND METHODS: In a retrospective, single-center study, 37 consecutive patients were identified between 1999 and 2005 that underwent preoperative MRI and surgical resection of HCC. A total of 47 lesions (mean size = 6.85 cm, range = 1-25 cm) were assessed for signal intensity (SI), enhancement patterns, and secondary morphologic features. Interobserver rating, percentage enhancement, and contrast-to-noise-ratio (CNR) were determined. Lesions were assessed for combinations of typical MRI features. Regression analysis was used to assess relations between MRI findings and tumor size. RESULTS: On fat-suppressed T2-weighted (T2w) fast-spin-echo, smaller lesions had lower SI compared to larger lesions (P < 0.05). In the arterial phase, smaller lesions showed significantly higher percentage enhancement compared to larger lesions (P < 0.05). In the delayed phase, smaller lesions showed less pronounced washout (P < 0.05). Heterogeneity of the lesions, including fatty infiltration, internal nodules, or mosaic pattern, was observed significantly more frequently in larger lesions (P < 0.001). The classic combination of high T2w signal, strong arterial enhancement, and delayed phase washout was present in 23 of 44 lesions (52%). CONCLUSION: Smaller HCC often showed lower SI on T2w, more intense arterial enhancement, and less pronounced delayed washout compared to larger HCC.     

Combined pituitary hormone deficiency and PROP-1 mutation in two siblings: a distinct MR imaging pattern of pituitary enlargement

Mutations of the PROP-1 gene are the most frequent genetic defect in patients with combined pituitary hormone insufficiency. We present the cases of 2 siblings with PROP-1 mutations whom we observed longitudinally. Their initial pituitary MR imaging examinations showed identical findings: an enlarged adenohypophysis, with striking hypointensity on T2-weighted images and slight hyperintensity on T1-weighted images. In one of the children, the follow-up MR imaging obtained 3 years after hormonal replacement revealed a decrease in the size of the anterior pituitary lobe.     

The effect of MR contrast medium dose on pituitary gland enhancement, microlesion enhancement and pituitary gland-to-lesion contrast conspicuity

Introduction The purpose of this study was to compare the differences in gland enhancement, microlesion enhancement and gland–lesion contrast ratio in patient groups in which half-dose (HD), standard-dose (SD) and double-dose (DD) contrast medium was used in pituitary MR imaging.Methods Pituitary gland enhancement and microlesion enhancement were measured and gland–lesion contrast ratios were calculated in 18 patients receiving HD (0.05 mmol/kg), 9 receiving SD (0.1 mmol/kg) and 13 receiving DD (0.2 mmol/kg) contrast medium. Gland enhancement and microlesion enhancement over baseline were determined employing DICOM region of interest measurements and compared after normalization to temporal lobe white matter. Contrast ratios and differences were also calculated and compared.Results Gland enhancement and lesion enhancement were greater with larger contrast medium doses (gland: HD 50%, SD 99%, DD 132%; microlesion: HD 19%, SD 54%, DD 86%). The gland–lesion contrast ratios were similar with the three doses (25.6%), reflecting expected similar fractional contrast medium distributions in spite of different doses. The signal difference between gland and microlesion, therefore, was a fixed percentage of gland enhancement (ΔS approximately 26%) with greater signal differences with larger contrast medium doses.Conclusion Greater gland-to-lesion signal differences with larger contrast medium doses would likely improve pituitary microlesion visualization and margin characterization aiding in microlesion detection as well as preoperative planning.     

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.     

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.     

Gd-DTPA-enhanced MR imaging of pituitary adenomas

Eleven previously nonoperated patients with suspected pituitary microadenomas were scanned on a 1.5-T GE system before and after administration of IV gadolinium-DTPA (0.1 mmol/kg). Six patients had Cushing disease, four had hyperprolactinemia, and one had acromegaly. Surgical confirmation was available in all cases, and these findings were correlated with results of CT and venous sampling, when available. The normal pituitary gland, infundibulum, and cavernous sinuses enhance immediately after the administration of gadolinium-DTPA, allowing contrast between the enhancing normal glandular tissue and low-intensity microadenomas. Contrast-enhanced MR detected a lesion not seen on the unenhanced images in two patients with Cushing disease and in one patient with hyperprolactinemia. Tumor delineation was improved with gadolinium administration in two additional cases. In six patients, administration of gadolinium did not significantly alter the precontrast interpretation. Adenomas were found at surgery in all 11 patients. The tumor was correctly localized on MR in four of the six patients with Cushing disease, resulting in an accuracy of 66.7%. In another patient, although a focal lesion was detected on MR, location of the adenoma at surgery was discrepant with the MR findings and was therefore considered a false-positive study. In the single false-negative examination, both pre- and postcontrast MR failed to detect a surgically confirmed microadenoma suspected on both contrast-enhanced CT and venous sampling. Correct localization of the adenoma was achieved in all of the five non-Cushing patients, yielding an accuracy of 100%. Immediate T1-weighted coronal scans were most useful in detecting intrasellar disease. Delayed scans obtained 30 min after injection did not improve the differentiation of pituitary gland from microadenoma.(ABSTRACT TRUNCATED AT 250 WORDS)     

垂体大腺瘤的MRI影像分析

目的:探讨垂体大腺瘤的MRI影像特征。方法:回顾性分析过去10年经临床病理证实17例垂体大腺瘤的MRI平扫及增强表现。结果:垂体大腺瘤表现为鞍区肿块,T1WI呈等或略低信号,T2WI呈等或略高信号,正常垂体未见显示。海绵窦侵袭性垂体腺瘤3例,2例伴有出血,“腰身”显示6例。结论:MR对垂体大腺瘤有定性诊断价值.术前可有效地观察其形态大小信号及与周围组织关系。     

Solitary fibrous tumor of the pleura: MR appearance and enhancement pattern

PURPOSE: The aim of the current study was to characterize the MR appearance of solitary fibrous tumor of the pleura (SFTP). METHOD: Twenty-two consecutive patients with histologically confirmed SFTP were retrospectively evaluated with MRI. RESULTS: Tumors demonstrated low signal intensity (n = 18, 82%), iso signal intensity (n = 2, 9%), and high signal intensity (n = 2, 9%) on T1-weighted images. On T2-weighted images, tumors were observed as low signal intensity (n = 10, 45%), high signal intensity (n = 2, 9%), and mixed signal intensity (n = 10, 45%). Solid component in the proliferation of tumor cells corresponded to low signal intensity in 12 tumors (55%) on T2-weighted images. On gadolinium-enhanced T1-weighted images, inhomogeneous enhancement (n = 18, 82%), nodular enhancement (n = 6, 27%), and homogeneous enhancement (n = 4, 18%) were observed. The enhanced lesion within the tumors had dense tumor tissue and dilated microvessels in the pathologic specimen. CONCLUSION: SFTP shows variable appearance and enhancement pattern on MRI according to morphologic tumor heterogeneity.