Spin-echo MR imaging of intracranial hemorrhage

Evaluation of Red Degeneration of Uterine Leiomyoma with Susceptibility-weighted MR Imaging

Purpose:

Red degeneration of uterine leiomyoma (RDL) is a hemorrhagic infarction caused by peripheral venous thrombosis. The peripheral high-intensity rim on T₁-weighted MRI is characteristic for RDL; however, it may not be observed at all the phases of RDL. Susceptibility-weighted MR sequences (SWS) have exquisite sensitivity to blood products, and we hypothesized that the low-intensity rim due to the T2* shortening effects of blood products may be more clearly demonstrated on SWS. The purpose of this study is to evaluate the capability of SWS for the diagnosis of RDL.

Methods:

Surgically proven 15 RDL, which showed suggestive MRI findings (high-intensity rim or entirely high signal intensity on T₁-weighted imaging) were retrospectively evaluated. MRI was qualitatively evaluated for the presence of high-intensity rim around a mass on fat-saturated T₁-weighted images, and low-intensity rim on T₂-weighted images and on SWS (susceptibility-weighted imaging [SWI] or T₂-star-weighted angiography [SWAN]).

Results:

The high-intensity rim on T₁-weighted images, low-intensity rim on T₂-weighted images and on SWS were observed in 47%, 47%, and 100% of RDL, respectively. The other 53% of lesions showed entirely high signal intensity on T₁-weighted images. Pathological examination revealed coagulative necrosis in all 15 lesions.

Conclusion:

SWS may be helpful for the diagnosis of RDL by revealing characteristic peripheral low-intensity rim.

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.

Comparison of MR Imaging and CT in Pituitary Macroadenomas

The findings on mid-field MR imaging and CT were compared retrospectively in 65 patients with pituitary macroadenomas. The evaluation comprised tumour extension and delineation, invasiveness, relationship to adjacent structures, and internal tumoral changes. MR was superior to CT except in the demonstration of bone changes and tumour calcification. The superiority of MR was most pronounced regarding cavernous sinus invasion, tumour relationship to the carotid arteries and optic chiasm, and tumour haemorrhage. Extensive bone changes were visualized with both methods; erosions were often seen only with CT. It is concluded that MR is the preferable method for evaluation of pituitary macroadenomas. CT is useful as a supplementary modality when detailed information on bone anatomy is required, particularly if a transsphenoidal surgical approach is contemplated.

Evaluation of traumatic subarachnoid hemorrhage using susceptibility-weighted imaging

BACKGROUND AND PURPOSE

SWI is an MR imaging technique that is very sensitive to hemorrhage. Our goal was to compare SWI and CT to determine if SWI can show traumatic SAH in different parts of the subarachnoid space.

MATERIALS AND METHODS

Twenty acute TBI patients identified by CT with SAH underwent MR imaging scans. Two neuroradiologists analyzed the CT and SWI data to decide whether there were SAHs in 8 anatomical parts of the subarachnoid space.

RESULTS

Fifty-five areas with SAH were identified by both CT and SWI. Ten areas were identified by CT only and 13 by SWI only. SAH was recognized on SWI by its very dark signal intensity surrounded by CSF signal intensity in the sulci or cisterns. Compared with the smooth-looking veins, SAH tended to have a rough boundary and inhomogeneous signal intensity. In many instances, blood in the sulcus left an area of signal intensity loss that had a "triangle" shape. SWI showed 5 more cases of intraventricular hemorrhage than did CT.

CONCLUSIONS

SAH can be recognized by SWI through its signal intensity and unique morphology. SWI can provide complementary information to CT in terms of small amounts of SAH and hemorrhage inside the ventricles.

MRI of pituitary macroadenomas with reference to hormonal activity

In 115 patients with pituitary macroadenomas, the findings on mid-field MRI were correlated with the hormonal activity of the tumours. Adenomas secreting growth hormone (GH), prolactin (PRL) and clinically nonsecretory adenomas were studied. Tumour size, invasiveness and signal intensity patterns were recorded. Relaxation times and ratios of signal intensity and proton density (relative to the corpus callosum) were analysed in areas of apparently solid tissue in a subgroup of 59 previously untreated patients. Invasiveness was more common in PRL- and GH-secreting adenomas than in the nonsecreting ones. Diffuse invasion of the base of the skull was most common in prolactinomas, and associated with a lower frequency of suprasellar tumour extension. In prolactinomas, a correlation was found between the maximum serum PRL level and tumour size. Haemorrhagic, cystic or necrotic areas were less common in GH-secreting tumours than in the other types. Haemorrhage was more common in prolactinomas than in nonsecreting tumours. MR parameters were similar in prolactinomas and nonsecreting adenomas, but indicated a smaller amount of water in GH-secreting tumours.

Primary intracerebral and subarachnoid hemorrhage. An approach to diagnosis and therapy

The diagnosis of primary intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH) has become easier with the advent of modern imaging techniques. The incidence of ICH has declined, while SAH has remained relatively constant. The prognosis for both disorders remains dismal and the mortality rate is substantially higher than that observed with ischemic stroke. Early imaging with CT or MRI is important for rapid and accurate diagnosis. General medical management in a skilled nursing facility should be available for patients who are not moribund. Therapy for ICH is predominantly supportive and effective medical and surgical intervention remains elusive. For SAH, calcium channel blockers may reduce cerebral ischemic complications related to vasospasm, but effective medical therapy to prevent rebleeding has not been established. Early surgery after SAH should be considered in clinically stable patients. Many challenges remain regarding the prevention and treatment of both these cerebral hemorrhage subtypes.

MR imaging of intracranial hemorrhage in neonates and infants at 2.35 Tesla

The variations of the relative signal intensity and the time dependent changing contrast of intracranial hemorrhages on high-field spin-echo magnetic resonance images (MRI) were studied in 28 pediatric patients. For T1-weighted images, a repetition time (TR) of 500 ms and an echo time (TE) of 30 or 23 ms was used. The corresponding times for T2-weighted images were TR 3000 ms and TE 120 ms. Intracranial hematomas, less than 3 days old, were iso- to mildly hypointense on short TR/TE scans and markedly hypointense on long TR/TE scans (acute stage). In the following four days the signal of the hematomas became hyperintense on short TR/TE scans, beginning in the periphery and proceeding towards the center. On long TR/TE scans the signal remained markedly hypointense (early subacute stage). 7-14 days old hematomas were of high signal intensity on short TR/TE scans. On long TR/TE scans they appeared hypointense in the center and hyperintense in the periphery (late subacute stage). By the end of the second week the hematomas were of high signal intensity on all pulse sequences (chronic stage). Chronic hematomas were surrounded by a parenchymal rim of hypointensity on long TR/TE scans. 28 neonates and infants (with 11 follow-up examinations) of 31.5-70.6 weeks postconceptional age (PCA), with an intracranial hemorrhage were examined. The etiologies of the hemorrhages were: asphyxia (17 cases), brain infarct (2), thrombocytopenia (1), clotting disorder (1) and unknown origin (7). The aim of this study was to describe the appearance of intracranial hemorrhages in neonates and infants with MRI at 2.35 Tesla using spine-cho sequences.

The role of imaging in the management of cerebral and ocular ischaemia

The last decade has seen several major technological advances in vascular neuroradiology, the most clinically significant of which have been the facility to image the brain and the extracranial carotid bifurcation noninvasively with accuracy and safety. Another major advance has been unequivocal evidence from formal statistical overviews that antiplatelet therapy, particularly aspirin, reduces the risk of serious vascular events by about 25%. These advances have changed clinical practice such that most patients presenting with symptoms suggestive of cerebral ischaemia should now have cranial CT to exclude intracerebral hemorrhage, not only because the causes and prognosis of cerebral ischaemia differ from those of intracerebral hemorrhage, but because many patients with cerebral ischaemia should be considered for antiplatelet therapy. Besides the use of long term antiplatelet therapy and control of vascular risk factors, other acute treatment options are limited with the possible exception of anticoagulation, thrombolysis, cytoprotective agents and carotid endarterectomy. If, as seems likely, the current clinical trials show that carotid endarterectomy plus medical therapy improve upon the stroke-free survival of patients treated medically, at least in symptomatic patients with severe stenosis, the number of carotid endarterectomies performed will increase considerably because carotid bifurcation disease is the most common cause of cerebral and ocular ischemic events. It will then be even more important to be able to obtain accurate anatomical and physiological information about the extracranial and intracranial circulations with utmost safety. Duplex ultrasound is currently the noninvasive screening method of choice for carotid bifurcation disease because it is available, relatively cheap, and reasonably accurate. It not only images the vessel lumen and degree of stenosis, but also the morphology of the vessel wall and associated plaque, the relevance of which is still uncertain in the pathogenesis of cerebral and ocular ischaemia. A major limitation of duplex sonography is that it cannot reliably distinguish tight stenosis from occlusion and it does not image the proximal or distal carotid circulation. The aim of newer techniques will be to distinguish tight extracranial carotid stenosis from occlusion and to provide anatomical, physiological and pathological information about the intracranial circulation and ischemic lesions (in view of potential for thrombolytic therapy of major intracranial vessel occlusion) with safety and reproducible accuracy.

Computed tomography versus magnetic resonance imaging. Of the pediatric central nervous system. Techniques, indications, and examples

The techniques for computed tomography and magnetic resonance imaging are described. Indications are given for the two procedures as well as the rationale for selection of one or the other in evaluation of the pediatric central nervous system. The benefits derived from each one are illustrated by a series of representative reproductions.

Magnetic resonance imaging of subarachnoid hemorrhage

Magnetic resonance (MR) imaging of subarachnoid hemorrhage (SAH) due to a ruptured aneurysm has been evaluated in relation to CT findings on 30 patients. In the acute stage, particularly less than 24 hours after the bleeding episode (25 patients), SAH appeared of high intensity relative to the surrounding brain on a T-2 weighted SE image but isointense where the corresponding CT scan showed blood clot of attenuation value over 60 H. A T-2 weighted SE image was able to reveal subtle evidence of SAH not visible on the CT scan. The T-1 weighted IR image was not as sensitive. Blood clot (HU greater than 60) appeared isointense, but mild and moderate SAH (HU less than 60) was indistinguishable from normal CSF. MR imaging was also sensitive to subacute and chronic SAH (5 patients). Three out of four SAH appearing normal on CT showed high intensity on T-2 weighted images. Thirteen out of 24 aneurysms (54%) larger than 5 mm in diameter on angiography were detected on T-2 weighted images. Smaller aneurysms less than 4 mm were not visualized. MR imaging was able to indicate the ruptured one in cases of multiple aneurysms by showing hemorrhagic lesions more clearly than CT. We conclude that MR imaging is very helpful for diagnosing SAH, particularly when CT is normal, and in indicating aneurysm location as well as rupture site.