Increased T1 signal of the residual normal anterior pituitary gland following medical treatment of pituitary prolactinoma

PURPOSE: To illustrate that residual normal pituitary gland may show hyperintense signal on T1-weighted image after medical treatment of pituitary prolactinoma. MATERIAL: and methods. Three patients treated with bromocriptine for a prolactinoma and showing hyperintense signal of the residual normal pituitary tissue on T1-weighted images were studied. In all patients, measurements of the anterior pituitary gland signal (APGS) and the temporal lobe white matter signal (TLWMS) were obtained by a "region of interest" (ROI) on coronal T1-weighted images. The APGS/TLWMS ratios were calculated and compared to those of a control group of 30 normal subjects. RESULTS: In the three patients, the measurements obtained by ROI confirmed the visual impression of high signal of the residual normal pituitary tissue. Ratios were ranging from 1.15 to 1.21, while they were ranging, in the control group from 0.92 to 1.09. CONCLUSION: In patients with prolactin-secreting adenoma seen after medical treatment, high signal of the residual normal pituitary tissue can be observed, probably due to cellular hyperactivity as it can be noticed during some physiological states. This pattern has to be differentiated from other pituitary abnormalities demonstrating T1 hyperintensity such as hemorrhagic changes of a prolactinoma.     

Biliary atresia in neonates and infants: triangular area of high signal intensity in the porta hepatis at T2-weighted MR cholangiography with US and histopathologic correlation

PURPOSE: To correlate a triangular area of high signal intensity in the porta hepatis on T2-weighted magnetic resonance (MR) cholangiograms of biliary atresia with ultrasonographic (US) and histopathologic findings in a portal mass observed during a Kasai procedure. MATERIALS AND METHODS: Twenty-one consecutive neonates and infants (age range, 13-88 days; mean age, 59 days) with cholestasis underwent US and single-shot MR cholangiography. In 12 patients with biliary atresia diagnosed at histopathologic examination, MR cholangiographic findings in the porta hepatis were correlated with US and histopathologic findings in the portal mass. RESULTS: At US, eight of the 12 patients had round, linear, or tubular hypoechoic portions within a triangular cord; MR cholangiography revealed a triangular area of high signal intensity confined to the porta hepatis. Histopathologic examination of the portal mass revealed a cystic or cleftlike lesion surrounded by loose myxoid mesenchyme and platelike fetal bile ducts. Neither the large cystic lesion without ductal epithelium nor the small cleftlike lesion with scanty epithelium demonstrated bile staining. Similar areas of high signal intensity were not seen on T2-weighted images in the remaining patients (four with biliary atresia and nine with neonatal hepatitis). CONCLUSION: In biliary atresia, T2-weighted single-shot MR cholangiography can show a triangular area of high signal intensity in the porta hepatis that may represent cystic dilatation of the fetal bile duct.     

MR signal intensity of parathyroid adenomas: correlation with histopathology

Recent experience has shown that parathyroid adenomas vary in their MR signal intensity, which raises the question of whether the signal intensity is related to different histologic characteristics. In order to address this question, 10 patients who had MR imaging studies (four at 0.35 T, six at 1.5 T) showing large- to medium-sized parathyroid adenomas and who subsequently underwent surgery with histologic proof of the lesion were evaluated. The MR appearance was compared with histologic characteristics. The adenomas were classified into three groups according to the MR appearance: group I, low signal intensity on short TR/TE images, high signal intensity on long TR/TE images (n = 5); group II, low signal intensity on short and long TR/TE images (n = 3); group III, high signal intensity on short and long TR/TE images (n = 2). Histologic analysis revealed that the major features of each group were different. High cellularity without degeneration or fibrosis was observed for all five adenomas from group I. In group II, all three adenomas showed cellular degenerative changes, old hemorrhage with hemosiderin-loaded macrophages, and/or fibrosis. In group III, both adenomas showed evidence of acute hemorrhage without significant degenerative or fibrotic changes. These data suggest that the signal intensity of parathyroid adenomas on T1- and T2-weighted images corresponds at least in part to differences in histologic composition.     

Breast lesions with high signal intensity on T1-weighted MR images

Magnetic resonance imaging of the breast supplies much information concerning the signal characteristics of a lesion. Among these, high signal intensity on non-fat saturated T1-weighted imaging (WI) is a special finding. Such a finding may result from different causes, such as a paramagnetic substance or fatty, bloody or proteinaceous content. In this article, we present hyperintense breast lesions on T1-WI.     

High signal intensity of the posterior pituitary gland on T1-weighted MR images. Correlation with plasma vasopressin concentration to water deprivation

PURPOSE: To evaluate the effect of water deprivation on the signal intensity of the posterior pituitary gland on T1-weighted MR images and correlate the signal intensity with the plasma vasopressin concentration. MATERIAL AND METHODS: Fifteen rabbits were studied: Group 1 (n=10) was deprived of water for 9 days and Group 2 (n=5) was replenished water for 7 days after 7-day water deprivation. MR imaging and plasma vasopressin measurement by radioimmunoassay were made before and after water deprivation and replenishment. Sequential changes of the signal intensity ratio of the posterior lobe to the pons and plasma vasopressin concentration were correlated. RESULTS: Before water deprivation, the hyperintense posterior lobe was demonstrated in all rabbits. During water deprivation, the signal intensity ratio decreased and vasopressin concentration increased gradually. On the contrary, the signal intensity ratio increased and vasopressin concentration decreased with water replenishment. The signal intensity ratio correlated well with the plasma vasopressin concentration (p<0.05). CONCLUSION: There was a negative, linear correlation between the signal intensity ratio of the posterior pituitary gland on T1-weighted MR images and plasma vasopressin concentration to water deprivation. The results support that the high signal intensity of the posterior pituitary gland on T1-weighted MR images is attributed to the normal content of vasopressin-neurosecretory granules.     

MR imaging in thyroid disorders: correlation of signal intensity with Graves disease activity

Thirty-six patients with a variety of thyroid disorders and eight healthy subjects were studied with T1- and T2-weighted magnetic resonance (MR) imaging. Solid benign nodules, malignant tumors, and inflammatory conditions were not distinguishable by thyroidal MR signal intensity, but almost all patients with Graves disease had a moderate to marked diffuse increase in signal intensity at both settings. Quantitative evaluation showed that in these patients, the thyroid-muscle signal intensity contrast ratio was linearly related to both the serum thyroxine (T4) level and the 24-hour radioactive iodine uptake. In three patients treated with iodine 131, this contrast ratio rose or fell in parallel with the serum T4 level and 24-hour radioactive iodine uptake. Either parenchymal changes or increased vascularity in Graves disease, or both, could produce these findings. In patients without Graves disease, signal intensity was not correlated with serum T4 levels. These findings suggest that MR signal intensity may reflect the activity of the stimulatory process in Graves disease and may therefore be a useful measure of thyroid function in this disorder, with both diagnostic and prognostic value.     

Malignant lesions of the liver with high signal intensity on T1-Weighted MR images

Our purpose was to identify the histologic types of malignant liver lesions with high signal intensity (SI) on T1-weighted images and to describe the MR imaging features. Thirteen patients with malignant liver lesions high in SI on T1-weighted images were studied with a 1.5-T MR imager using pre- and serial postcontrast spoiled gradient-echo (SGE) sequences (all patients), T2-weighted fat-suppressed spin-echo sequences (all patients), precontrast T1-weighted fat-suppressed spin-echo sequences (five studies in five patients), and precontrast out-of-phase SGE sequences (seven studies in six patients). Images were reviewed retrospectively to determine number of lesions; lesion size; SI of lesions on T1-weighted, T2-weighted, and fat-attenuated T1-weighted images; distribution of high SI in lesions on T1-weighted images; and tumor enhancement pattern. Seven patients had multiple tumors high in SI on T1-weighted images and six patients had solitary tumors. Seventy-two lesions were less than 1.5 cm in diameter and 35 lesions were more than 1.5 cm in diameter. Nine patients had solid malignant lesions and four patients had cystic malignant lesions. All tumors more than 1.5 cm in diameter were heterogeneously high in SI on T1-weighted images, and all tumors less than 1.5 cm were completely homogeneous or homogeneous with a small central hypointense focus. All tumors were more conspicuous on T1-weighted fat-attenuated images, both on excitation spoiled fat-suppressed spin-echo or on out-of-phase SGE images with the exception of one fat-containing hepatocellular carcinoma (HCC). In one patient with melanoma metastases and one patient with multiple myeloma nodules, appreciably more lesions were detected on out-of-phase SGE images. Causes of hyperintensity were considered to be either fat, melanin, central hemorrhage, or high protein content, all of which may be seen in a variety of tumors. Fat-attenuation techniques are helpful in the detection of these lesions.     

Articular cartilage: correlation of histologic zones with signal intensity at MR imaging

Zones of high and low signal intensity on magnetic resonance (MR) images of articular cartilage were correlated with the four histologic zones normally found in such cartilage. Grossly normal articular cartilage from knees and ankles of a fresh cadaver were used in the study. The three zones identified on MR images included a low-intensity zone near the articular surface, a zone of higher signal intensity next to that, and a second zone of low intensity that was deep to the two others. The location of the superficial low-intensity zone corresponded to dense, tangentially oriented layers of collagen in the superficial histologic zone. Higher signal intensity deep to the superficial low-intensity zone correlated with cartilage in the transitional zone. The deep low-intensity zone correlated with a combination of deep radiate and calcified cartilage and cortical bone. Results of this study indicate that, with high resolution, MR imaging may demonstrate three zones of differing signal intensity in articular cartilage. The superficial low-intensity zone may be a useful marker of the surface of normal articular cartilage.     

Magnetic resonance elastography of the breast: correlation of signal intensity data with viscoelastic properties

OBJECTIVES: We sought to investigate the potential value of magnetic resonance (MR) elastography to improve the differentiation between benign and malignant tumors. MATERIAL AND METHODS: Measurements of 5 patients with 6 malignant lesions, 11 patients with benign lesions, and 4 patients with no lesions at all were performed at 1.5 Tesla. After breast MR imaging, MR elastography was performed as a targeted measurement. Low-frequency mechanical waves (65 Hz) were transmitted into the breast tissue using an oscillator and were displayed by means of a MR sequence within the phase of the MR image. After reconstruction, the viscoelastic information was correlated with the signal intensity and morphology data. RESULTS: All examinations were technically successful realized in approximately 25 minutes. Malignant tumors documented higher values of elasticity than benign corresponding with signal intensity and morphologic data. CONCLUSION: A good separation exists between benign and malignant lesions in elasticity, corresponding with specific signal intensity and morphologic data. Further clinical studies with a larger number of patients are needed for extended validation.     

Hyperintense signal of the posterior pituitary on T1-weighted MR images: an experimental study

The origin of the hyperintense signal (HIS) of the pituitary gland posterior lobe (PL) on T1-weighted magnetic resonance (MR) images was investigated. Six rabbits were imaged on a 1.5 T device before and after 2 weeks' feeding of hypertonic saline solution (phase I). Two were killed soon after the second imaging; the pituitary gland was examined histochemically for neurosecretory granules containing antidiuretic hormone (ADH). The other four rabbits were given regular water for another 2 weeks (phase II) and then were again imaged. The plasma ADH level was monitored at each imaging session. In all subjects, the signal intensity of the PL decreased at the end of phase I, and the HIS reappeared at the end of phase II. The neurosecretory granules in the PL significantly diminished in number in phase I. Plasma ADH levels significantly increased in phase I and returned to their normal range in phase II. These clear correlations between MR findings and hormonal and histochemical results strongly suggest that the source of the HIS of the PL is the neurosecretory granules containing ADH.     

Unimpinged and impinged anterior cruciate ligament grafts: MR signal intensity measurements

Regionalized magnetic resonance (MR) signal intensities were quantitatively measured in impinged and unimpinged anterior cruciate ligament (ACL) grafts. Images were obtained with a 1.5-T imager, and signal intensity was measured in the proximal, middle, and distal thirds of the graft. In 15 unimpinged ACL grafts, the signal intensity remained low and did not vary during the 1st year of graft implantation (45 images). In contrast, 17 impinged ACL grafts showed an increase in signal intensity in the distal two-thirds of the graft that persisted 1-3 years after implantation (P less than .001). Unimpinged grafts were placed in tibial tunnels posterior and parallel to the slope of the intercondylar roof. Reconstructions with anterior tibial tunnels resulted in graft impingement that caused increases in graft signal intensity. This increase demonstrates a clear association between surgical technique and the subsequent MR appearance of the graft.     

Signal intensity of decussation of the superior cerebellar peduncle on sagittal T1WI: correlation with age and gender

PurposeDecussation of the superior cerebellar peduncle (DSCP) usually shows low signal intensity (SI) on midsagittal T1-weighted imaging (T1WI) in neurologically normal brain. However, the SI change of DSCP with age and gender is not identified. This study aimed to investigate the relationship between SI of the DSCP and age and gender in healthy subjects.Materials and methodsSpin-echo (SE) midsagittal T1WI of 120 neurologically normal subjects (52 men, 68 women; age range: 4–64 years, mean age: 31 years) were evaluated retrospectively. Contrast-to-noise ratio (CNR) of the DSCP compared with that of the superior midbrain was calculated. One-way analysis of variance and bivariate correlation analysis were performed to evaluate the effects of gender and age.ResultsThe CNR was significantly lower in the DSCP than in the superior midbrain (P<.001). The CNR of DSCP was not correlated with gender (P=.118) and age (P=.764).ConclusionThe low SI of DSCP on midsagittal T1WI showed no correlation with gender or age in healthy subjects.     

Increased T2 signal intensity in the distal clavicle: incidence and clinical implications

Objective. The objectives of the current study were (1) to quantify the incidence of increased T2 signal in the distal clavicle and (2) to assess the clinical significance of this finding in patients with chronic acromioclavicular (AC) joint pain. Design and patients. Eight patients (five male and three female, 15–41 years of age) with disabling shoulder pain localized to the AC joint and marked increased T2 signal in the distal clavicle are presented. These eight patients underwent MR examination over a 25 month period (August 1996 to September 1998). The dictated reports of all shoulder MR examinations conducted over this same time period were reviewed retrospectively for the presence of signal abnormality in the distal cla-vicle. Clinical data and, in five patients, findings at shoulder arthroscopy or open surgery, were correlated with the results of MR imaging. One patient underwent arthroscopy on both shoulders. Results. The selected eight patients each presented clinically with disabling shoulder pain localized to the AC joint. One patient is presented twice, as both shoulders were symptomatic (n=9). Plain film examination (9/9) failed to indicate a structural cause of shoulder pain in any of the patients. MR examination demonstrated abnormally increased T2 signal in the distal clavicle in all nine cases and no other cause for AC joint pain. Three patients responded to a course of conservative therapy. Six experienced refractory pain despite conservative therapy. Resection of the distal clavicle was performed in five of the six cases. All patients who underwent resection of the distal clavicle experienced complete resolution of AC joint pain. A retrospective review of the dictated reports for all shoulder MR imaging examinations performed at out institution over a 25 month period (August 1996 to September 1998; n=761) demonstrated a 12.5% incidence of abnormally increased T2 signal in the distal clav-icle. Conclusions. Increased T2 signal in the distal clavicle is a relatively common finding (12.5%) on MR imaging examinations of the shoulder and in most cases is of no clinical significance. However, in patients with chronic AC joint pain and no other abnormality on plain film or MR imaging, increased T2 signal may represent an early manifestation of, or a process similar to, osteolysis of the distal clavicle. Patients with this presentation who continue to suffer from disabling pain following conservative therapy may benefit from surgical resection of the distal clavicle. Received: 7 February 2000 Revision requested: 21 March 2000 Revision received: 14 August 2000 Accepted: 17 August 2000     

MRI of blood flow: correlation of image appearance with spin-echo phase shift and signal intensity

Phase-sensitive imaging was used to correlate signal distribution with phase shift and velocity distribution in spin-echo magnetic resonance imaging (MRI). Flow-dependent, changing intensity patterns that were seen in a constant-flow phantom study were explained by the simultaneous effects of inflow signal enhancement, first-echo dephasing, and outflow signal loss occurring during laminar flow. In clinical studies, first-echo dephasing was shown during laminar flow in the inferior vena cava. Turbulent flow was demonstrated in the descending thoracic aorta during late systolic flow, and turbulent dephasing-rephasing was shown in the abdominal aorta.     

Papillary renal cell carcinoma showing high signal intensity on T2-weighted magnetic resonance images: radiological-pathological correlation

Papillary renal cell carcinoma (PRCC) is the second most common class of renal cell carcinoma. PRCCs have typically been reported to demonstrate homogeneous, low-intensity signals in T2-weighted magnetic resonance imaging (MRI) scans and rarely high-intensity signals. We reported two cases of PRCC with high signal intensity on T2-weighted images. These two cases were accompanied by a small amount of hemosiderin deposition and intense edema in the tumor.     

Correlation of high signal intensity of the pituitary stalk in macroadenoma and postoperative diabetes insipidus

BACKGROUND AND PURPOSE: High signal intensity (HSI) at the pituitary stalk is reported in pituitary adenomas. Our purpose was to clarify how and when this HSI formed, its long-term fate, and its relation to the function of infundibuloneurohypophyseal (INH) system. METHODS: Twenty-two patients with pituitary adenoma and supradiaphragmatic extension underwent 1.5-T MR imaging. Patients were assigned to two groups A (n = 18; those with stalk tip HSI) and B (n = 4; those without HSI) on postoperative T1-weighted images. Endocrine status was postoperatively evaluated and compared in both groups. RESULTS: Group A patients did not have postoperative permanent diabetes insipidus (DI). Preoperative images in 17 patients revealed linear or ovoid HSI on the adenoma surface immediately above the diaphragma sellae. Of these, two with a poorly developed diaphragma sellae had HSI near the median eminence and inside the sella turcica. HSI was not apparent in the remaining patient with a giant, irregularly shaped adenoma. In group B, three patients had permanent DI. No patient had HSI on preoperative images. CONCLUSION: Postoperative pituitary stalk HSI is derived from preoperative supradiaphragmatic HSI on the adenoma surface. The suspected mechanism is blockage of the hypophyseal-pituitary axis, with an accumulation of neurosecretory granules at the diaphragmatic level. Diaphragmatic shape may influence the location of HSI. The shape and location of HSI are essentially stable for years after surgery. No patients with permanent DI had HSI before or after surgery. HIS at the pituitary stalk tip is a useful landmark for predicting functional integrity of the INH system in patients with a large pituitary adenoma.