Ligamentum flavum: appearance on sagittal and coronal MR images

The appearance of the ligamentum flavum on sagittal and coronal magnetic resonance (MR) images has not been described in detail in the radiologic literature. The authors reviewed correlative MR images and anatomic sections obtained with a cryomicrotome in 20 cadavers in order to analyze anatomic relationships, variations, and progressive degenerative changes of the ligamentum flavum in the lumbar region. MR imaging showed the ligamentum flavum as an intermediate-signal-intensity structure on images obtained with short and long repetition times (TRs). Sagittal short TR images were effective for evaluating relationships between the ligamentum flavum, spinal canal, and nerve roots. Degenerative changes in the ligamentum flavum appeared as changes in shape or thickness of the ligaments on MR images. Calcification and fat infiltration, which were well depicted on anatomic sections, were not visualized on MR images.     

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)     

Clinical usefulness of artronix brain scanner multiplanar coronal and sagittal brain images

Summary The Artronix 1100 head scanner is a promising unit which allows reconstitution of the images in coronal and sagittal planes from the axial slice. The clinical usefulness of coronal and sagittal images thus obtained is illustrated and discussed.     

Usefulness of the dynamic gadolinium-enhanced magnetic resonance imaging with simultaneous acquisition of coronal and sagittal planes for detection of pituitary microadenomas

Objective

Does dynamic gadolinium-enhanced imaging with simultaneous acquisition of coronal and sagittal planes improve diagnostic accuracy of pituitary microadenomas compared with coronal images alone?

Methods

Fifty-six patients underwent 3-T sella MRI including dynamic simultaneous acquisition of coronal and sagittal planes after gadolinium injection. According to conspicuity, lesions were divided into four scores (0, no; 1, possible; 2, probable; 3, definite delayed enhancing lesion). Additional information on supplementary sagittal images compared with coronal ones was evaluated with a 4-point score (0, no; 1, possible; 2, probable; 3, definite additional information). Accuracy of tumour detection was calculated.

Results

Average scores for lesion detection of a combination of two planes, coronal, and sagittal images were 2.59, 2.32, and 2.18. 6/10 lesions negative on coronal images were detected on sagittal ones. Accuracy of a combination of two planes, of coronal and of sagittal images was 92.86%, 82.14% and 75%. Six patients had probable or definite additional information on supplementary sagittal images compared with coronal ones alone (10.71%).

Conclusion

Dynamic MRI with combined coronal and sagittal planes was more accurate for detection of pituitary microadenomas than routinely used coronal images. Simultaneous dynamic enhanced acquisition can make study time fast and costs low.

Key Points

? We present a new dynamic MRI technique for evaluating pituitary microadenomas ? This technique provides simultaneous acquisition of contrast enhanced coronal and sagittal images.? This technique makes the diagnosis more accurate and reduces the examination time.? Such MR imaging only requires one single bolus of contrast agent.

     

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.     

MR imaging of intrasellar meningiomas simulating pituitary adenomas

Over 3 1/2 years, 401 magnetic resonance studies were performed for suspected sellar-parasellar masses. Twenty-nine pituitary macroadenomas and 12 meningiomas were detected. Among the meningiomas there were three whose MR appearance simulated that of a pituitary tumor. In none of these cases was the diaphragma sellae visualized. Furthermore, in one case the prolactin level was elevated. A preoperative diagnosis of pituitary tumor resulted in an inappropriate surgical approach being used initially for its removal (transsphenoidal). Thus, nonvisualization of the diaphragma sellae and elevated prolactin levels do not exclude a nonpituitary origin of a sellar-parasellar tumor. Other methods for preoperative differentiation are discussed.     

Neurosarcoidosis: gadolinium-enhanced MR imaging

Two cases of neurosarcoidosis studied by Gd-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging are reported. Both patients demonstrated multifocal white matter abnormalities that were clustered near regions of intense meningeal enhancement. Presumed spread of neurosarcoidosis along Virchow-Robin spaces was demonstrated, as evidenced by contrast enhancement along the course of vessels supplying some of the white matter abnormalities.     

Diagnosis of early-stage rheumatoid arthritis: usefulness of unenhanced and gadolinium-enhanced MR images at 3 T

Forty-one consecutive unclassified arthritis patients with polyarthralgia including wrist joint were evaluated with 3-T MRI as possible early-stage rheumatoid arthritis (RA). After prospective follow-up, 21 of 41 patients fulfilled the American College of Rheumatology (ACR) criteria. Synovitis was detected in all 21 RA patients (sensitivity=100%) with postcontrast MRI and in 14 patients (67%) with unenhanced MRI when none of them fulfilled ACR diagnostic criteria. Fat-suppressed intermediate-weighted fast spin-echo (FSE) image showed high detection rate of synovitis and bone erosion, whereas FIESTA image clearly delineated joint fluid and bone trabeculae. MRI at 3 T is a potentially powerful tool for discriminating and managing early-stage RA patients.     

Os acromiale: evaluation of markers for identification on sagittal and coronal oblique MR images

 An os acromiale is a developmental abnormality of ossification involving the anterior acromion which may contribute to impingement and rotator cuff disease. When axial MR sections do not include the acromioclavicular joint, the diagnosis of this often subtle abnormality will rest on its recognition on oblique coronal and sagittal images where it mimics the acromioclavicular joint. The identification of this anomaly is important as it frequently alters the type of surgical procedure utilized in symptomatic patients. We evaluate several imaging features which may be used to diagnose an os acromiale in these cases.     

MR imaging of cavernous sinus involvement by pituitary adenomas

The ability of high-resolution MR imaging (1.5 T) to detect invasion of the cavernous sinuses by pituitary adenoma was determined through a retrospective review of 74 patients. These patients were divided into three groups: 25 normal subjects, 24 subjects with invasive pituitary adenomas, and 25 subjects with noninvasive pituitary adenomas. A fourth group of 30 patients, who subsequently underwent surgery for pituitary adenoma, was evaluated prospectively by MR for the presence or absence of cavernous sinus invasion. Several features were analyzed: (1) the detectability of the medial and lateral dural margins of the cavernous sinus (2) the size and variation in intensity of compartments within the cavernous sinus (3) the relationship of endocrine function to the surgical and MR appearance of the cavernous sinus and (4) carotid artery displacement or encasement by tumor. The normal cavernous sinuses were usually symmetric, but their sizes varied. The lateral dural margin of the cavernous sinus was always recognized on MR as a linear, discrete, low-intensity area. The medial dural margin (pituitary capsule) was seen on MR in only two of the 25 normal patients. In all 24 patients with cavernous sinus invasion involvement was unilateral and was most common with laterally positioned prolactin or adrenocorticotropic hormone secretory adenomas. Invasion of the cavernous sinus was suspected by MR in only two of the 13 invasive microadenomas and was questionable in three. In 10 of the 11 macroadenomas with surgically proved dural invasion, MR demonstrated an asymmetric increase in size and intensity of the superior and inferior cavernous sinus compartments. Noninvasive macroadenomas compressed and displaced the cavernous sinus bilaterally. The prospective MR evaluation of 30 patients undergoing surgery for pituitary tumor revealed a sensitivity for predicting cavernous sinus invasion of 55%, a specificity of 85.7%, a positive predictive value of 62.5%, and a negative predictive value of 81.8%. No feature permitted certain distinction between invasive and noninvasive microadenomas, as the medial dural wall of the cavernous sinus could not be reliably identified. The most specific sign of cavernous sinus invasion was carotid artery encasement.     

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.     

MR imaging of the thorax: a comparison of axial, coronal, and sagittal imaging planes

We performed direct multisection coronal and sagittal magnetic resonance (MR) images in addition to axial images to determine the value and limitations of coronal and sagittal planes compared with axial planes. Ninety-four MR examinations of the thorax were performed with a 0.3 T permanent magnet system (Fonar) by spin echo technique. The MR axial images were found superior to coronal in demonstrating prevascular adenopathy (one case), pretracheal nodes (nine cases), left paraaortic nodes (three cases), subcarinal nodes (three cases), and small pleural effusions (three cases). The coronal or sagittal planes were better to determine relationship of a mass at the lung apex (five cases) or an abnormality at the lung base (five cases). The anteroposterior displacement or compromise of great vessels and bronchi was best displayed on the axial plane whereas craniocaudal displacement of above structures was best seen on the coronal plane. The axial images were found most informative and we suggest that they be performed routinely. Coronal or sagittal planes may be added in selected cases.     

Dynamic gadolinium-enhanced rapid acquisition spin-echo MR imaging of the liver

Rapid acquisition spin-echo (RASE) magnetic resonance (MR) imaging allows for coverage of the entire liver with highly T1-weighted SE images during a single 23-second breath-holding period. The RASE sequence was implemented in conjunction with rapid intravenous injection of gadopentetate dimeglumine to enable performance of dynamic contrast material-enhanced MR imaging of the liver. Prospective evaluation of 24 patients with 62 liver lesions 1 cm or greater in diameter was performed. Images obtained with RASE were devoid of respiratory-related ghost artifacts or edge blurring. The dynamic contrast-enhanced RASE technique resulted in contrast-to-noise and contrast-to-artifact values and time efficiency measures significantly greater (P less than .05) than those obtained with use of conventional T1- and T2-weighted pulse sequences, indicating a higher likelihood for lesion detectability. Lesion conspicuity was maximal during or immediately following bolus administration of gadopentetate dimeglumine, with lesions often becoming obscured at delayed postcontrast imaging.     

MR imaging of pituitary adenomas after gamma knife stereotactic radiosurgery

OBJECTIVE: The purpose of this study was to evaluate the response of pituitary adenomas to radiosurgery as manifested by changes in size and appearance on serial MR imaging. MATERIALS AND METHODS: Over a mean follow-up period of 36 months, changes in 44 pituitary adenomas were assessed on 147 enhanced MR imaging studies. Prior surgery had been performed in 36 tumors (82%). RESULTS: At the time of radiosurgery, mean tumor volume was 5.9 +/- 0.8 cm(3) (mean diameter, 2.2 cm). The mean reduction in volume at last follow-up was 41% (+/- 5%, p < 0.001), and a decrease in tumor volume of 25-100% was observed in 34 tumors (77%). Mean reduction in tumor volume at 6 months after radiosurgery was 9% (p = 0.095); at 1 year, 24% (p < 0.001); at 2 years, 34% (p < 0.001); at 3 years, 41% (p < 0.001); and at 4 years, 50% (p = 0.008). Six months after radiosurgery a slight and transient increase in size was observed in 21% of tumors. During follow-up, neither decreased contrast enhancement nor cyst development was associated with changes in tumor volume. CONCLUSION: Tumor control was observed for most pituitary adenomas after radiosurgery and occurred gradually over a period of several years. A small increase in tumor size might be observed in the first 6 months after radiosurgery. In most cases, reductions in tumor size were not accompanied by a change in contrast enhancement or cyst formation.     

MR imaging features of thyrotropin-secreting pituitary adenomas at initial presentation

OBJECTIVE: We report the MR imaging characteristics of thyrotropin-producing pituitary adenomas at their initial presentation and also report the role of MR imaging in predicting surgical outcome in these rare tumors. MATERIALS AND METHODS: We reviewed the records and MR images of 21 patients with thyrotropin-producing pituitary adenomas from 1984 to 1999. The imaging features of these tumors were examined, including enhancing characteristics and tumor volumes. A staging system of tumor invasion was designed by grading cavernous and sphenoid sinus invasion and suprasellar extension. A cumulative invasion score was then used as a predictor of short-term surgical outcome. RESULTS: Twenty patients had macroadenomas, and one patient had a microadenoma. In 17 of 21 patients, the thyrotropin-producing pituitary adenoma was clearly visualized as a hypoenhancing mass compressing the normal pituitary gland. Conversely, in four patients, the pituitary gland was not discernible because of complete distortion by the adenoma. Thyrotropin-producing pituitary adenomas were large and showed a tendency to invade surrounding structures. Tumor volume ranged from 0.42 to 94.2 cm(3) (mean +/- SD, 16.0 +/- 17.8 cm(3)). The mean score of tumor invasion was 4.77 +/- 2.06 of a maximal possible value of 9.0. A high staging score was found to be predictive of an unfavorable response to surgery. CONCLUSION: Thyrotropin-producing pituitary adenomas are usually large tumors at initial presentation with hypoenhancing features compared with normal pituitary tissue; they tend to be invasive. Greater amounts of invasion correlate with incomplete surgical removal of the tumor and continued hormonal secretion.     

Dynamic sagittal half-Fourier acquired single-shot turbo spin-echo MR imaging of the temporomandibular joint: initial experience and comparison with sagittal oblique proton-attenuation images

BACKGROUND AND PURPOSE: Our aim was to assess dynamic half-Fourier acquired single-shot turbo spin-echo (HASTE) MR imaging of the temporomandibular joint (TMJ) using parallel imaging, in comparison with static proton density (Pd) imaging. MATERIALS AND METHODS: Thirty-four TMJs from 17 subjects (7 volunteers, 10 patients) were imaged in a multichannel head coil on a 1.5 T magnet by using a 35-second dynamic sagittal HASTE acquisition (TR/TE, 1180/65 msec; matrix, 128 x 128; section thickness, 7 mm; 30 images) and sagittal oblique Pd in closed- and open-mouthed positions (TR/TE, 1800/12 msec; matrix, 256 x 256; section thickness, 2 mm; 15 sections). Images were reviewed by 3 readers and rated for confidence of disk position, presence of motion artifact, range of motion, and presence of disk displacement on a 5-point scale. Consensus review of cases was also performed to assess disk dislocation and limited range of motion. RESULTS: More static examinations were rated as having motion artifact (19.6% versus 6.9%, P=.016), limited range of motion (30.4% versus 17.7%, P=.016), and disk dislocations (31.4% versus 22.6%, P=.071). Confidence ratings were higher on dynamic examinations (4.11 versus 3.74, P=.018). Chi-squared tests demonstrated no significant difference in consensus reviews of the 2 examination types. CONCLUSION: Dynamic HASTE TMJ MR imaging is a time-efficient adjunct to standard MR imaging protocols, producing fewer motion artifacts, additional range of motion information, and a dynamic assessment of disk position, when compared with static imaging. Further study is needed to evaluate the role of this sequence in diagnosing disk displacement.