J. Shinzato

MRI findings of hypothalamic hamartoma : Report of five cases and review of the literature

Hypothalamic hamartoma is a relatively rare congenital malformation, associated with the clinical presentation of precocious puberty of central type. Five cases with hypothalamic hamartoma are reported here, with an emphasis on MR appearance. The most common presentation of hypothalamic hamartoma was a small and well defined mass in the inferior aspect of the hypothalamus, showing isointensity on T1 weighted images and hyperintensity on T2 weighted images compared with the gray matter. The previous reports with MRI description are reviewed and compared with the present results.

Hybrid digital subtraction angiography: Initial clinical experience

Hybrid digital subtraction angiography was performed after modification of a DSA system. Alternate high voltage (110-120 kV) and low voltage (65-70 kV) were obtained within short time intervals of 60-70 ms with a high voltage switching generator. Experimental phantom studies revealed the exposure dose per single image of hybrid subtraction was approximately 30% of that of conventional DSA. The SNR of hybrid subtraction was improved by increasing the exposure dose and application of postprocessing programs. Clinical application of intraarterial and intravenous DSA revealed that soft tissue artifacts were removed surprisingly well, but image quality decreased because of lowered SNR. Frame integration and matched filtering improved image quality of hybrid subtraction.

MRI evaluation of sequential changes of the injured spinal cord

Thirty-seven cases of acute spinal cord injury were studied with MRI and correlated with the neurological findings. Nineteen out of 37 cases were followed by sequential MRI for 10 days to 1 year. Cord abnormalities, including cord compression, cord swelling, and abnormal signal intensities were observed on the initial MR images, followed by various changes, depending on the nature of the initial damage on the subsequent MR images. The most frequent initial changes within the cord included isointensity on both T1- and T2-weighted images or isoin-tensity on T1-weighted images and hyperintensity on T2-weighted images, followed at 2 months by persistence of isointensity on T1-weighted images and hyperintensity on T2-weighted images. The most common final MR appearance was hypointensity on T1-weighted images and hyperintensity on T2-weighted images. The size of the hyperintense area on T2-weighted images was the most important finding in predicting the prognosis of spinal cord injuries.

Comparison of MRI, CT and myelography in the diagnosis of lumbar disc disease

The records of 96 herniated lumbar discs of 94 patients were retrospectively analysed as to the diagnostic accuracy of MRI, myelography and CT myelography. Myelography and CT myelography were able to show certain associated findings, especially nerve root compression, but overall diagnostic accuracy of MRI was better than that of myelography and CT myelography.

The value of MRI in ossification of the posterior longitudinal ligament

One hundred and thirty-seven patients with ossification of the posterior longitudinal ligament (OPLL) were studied with MRI. The detectability of OPLL was greater on T2-weighted images than T1- or proton-density-weighted images. Intermediate or high signal was considered to be bone marrow produced in the ossification. Cord compression was often associated with high signal intensity. Disc degeneration was also frequently associated with OPLL. MRI was valuable in investigation of OPLL.

MR demonstration of meningeal enhancement with gadolinium-DTPA

Meningeal enhancement has been studied with gadolinium (Gd)-DTPA enhanced MRI in 12 normal and 24 abnormal cases. Pial enhancement was observed in meningeal carcinomatosis, while postoperative patients and sinus thrombosis never showed pial enhancement. Postoperative patients showed gradually decreasing dural enhancement over several months. These findings were useful differentiation of meningeal enhancement by Gd-DTPAMRI.

Dynamic MRI of the sellar region

Dynamic MRI, following rapid injection of gadolinium-DTPA, demonstrated progressive enhancement of the normal structures of the sellar and parasellar regions, whereas pituitary tumours and other parasellar tumours showed delayed enhancement. It was possible to differentiate the normal pituitary gland and cavernous sinus from tumours arising and invading the pituitary gland and cavernous sinus.