[Magnetic resonance angiography in stenosing-occlusive diseases of the carotid arteries: 3D with time of flight versus 3D with phase contrast]

We assessed the comparative sensitivity, specificity and diagnostic accuracy of 3D time of flight (TOF) versus 3D phase contrast (PC) MRA in the study of stenoses/occlusions of the extracranial carotid artery. Fifty-four patients were submitted to MRA because of their symptoms or of signs of cerebrovascular insufficiency. 3D TOF and 3D PC axial slices were acquired with a high field magnet; digital angiography was the gold standard. The parameters of 3D TOF acquisitions were: TR/TE/FA 50/8/20, 1 NEX, 512 x 256 matrix, 16 x 12 FOV, 1 axial slab of 60 slices, 1 mm slice thickness, superior presaturation band, ramp pulse, TA 10-18 minutes. 3D PC parameters were: TR/TE/ FA 25/9/20, 1 NEX, 256 x 128 matrix, 18 x 13 FOV, 1 axial slab of 60 slices, 1 mm slice thickness, VENC 35 cm/s, TA 10-15 minutes. 3D TOF MRA was in agreement with digital angiography in 95.6% of cases (22/23), overestimating a grade 3 stenosis as grade 4 (one case, 4.3%) and underestimating no stenoses. 3D PC MRA was in agreement with digital angiography in 78.2% of cases (18/23), overestimating three stenoses (13%); one grade 1 as grade 2 and two grade 4 as grade 5; two stenoses were underestimated (8.6%); one grade 4 as grade 3 and one grade 4 as grade 2. Sensitivity, specificity and diagnostic accuracy were 91.4%, 98.9% and 95.7% for 3D TOF, versus 83.2%, 97.2% and 92.3% for 3D PC, respectively. The two MRA techniques had different semiology. In spite of outstanding background noise suppression, 3D PC poorly depicted the turbulent flow at the carotid bifurcation in carotid stenoses. Therefore, 3D TOF appears a better technique to study stenoses/occlusions of the extracranial carotid arteries.

[Imaging with magnetic resonance imaging of the operated cervical spine]

The Authors report their personal experience with postoperative neuroradiologic studies in surgical patients with a herniated disk and/or degenerative cervical spondylosis. Twenty-six patients were enrolled: 16 of them underwent anterior diskectomy, 7 posterior decompressive laminectomy and 3 vertebral body removal. The patients were submitted to pre- and postoperative MRI with high field equipment (Signa 1.5 T, General Electrics), using sagittal SE T1- (TR/TE 360/15), PD and T2-weighted (TR/TE/FA 2000/40/120) sequences and T2-weighted GE axial sequences (TR/TE/FA 400/34/30). FSE sequences (TR/TE/ETL 4000/95/8) were used in 15 cases instead of the above T2-weighted SE sequences. The main postoperative MR findings were analyzed. In particular, the morphological and signal features of bone grafts, of vertebral end-plates, of the subchondral bone and of the surgical site were studied. After anterior diskectomy, the most frequent MR features were massive signal changes in the bone graft and lower vertebral plates, which were hypointense in T1 and hyperintense in T2; the adjacent subchondral bone also exhibited signal changes. Other postoperative MR findings accounted for early postoperative mobility (4 cases of persistent myelomalacia and 3 of bone graft fracture with consequent spinal instability) and late mobility (2 cases of herniated disk, 5 of spinal stenosis and one pseudomeningocele). The main limitation of MRI in postoperative cervical spine studies was the presence of ferromagnetic artifacts during SE, and even more GE, sequences; these artifacts were the main cause of misdiagnoses. In our experience, this troublesome limitation was overcome with FSE sequences but diagnostic accuracy remained poor in 4 patients. MRI, thanks to its multiparametric and multiplanar yield, is the gold standard for the examination of several early and late postoperative features and of postoperative mobility in the cervical spine. Moreover, T2-weighted FSE acquisitions are better than conventional SE to this purpose, because examination time is shorter, myelographic effect is improved and the sensitivity to ferromagnetic artifacts reduced.

[Fast spin echo imaging of vertebral metastasis: comparison of fat suppression techniques (FSE-CHESS, STIR-FSE)]

PURPOSES

To investigate the capabilities of fast spin echo (FSE) sequences in diagnosing spinal metastases and to compare two fat-suppression techniques: CHESS (chemical shift selective saturation) and STIR (short T1 inversion recovery). Fat suppression is recommended with FSE sequences because on them, different from conventional spin echo (SE) sequences, fat has high signal intensity in both T1 and T2 weighting, masking such high-signal bone lesions as metastases.

METHODS

Ninety metastatic lesions in 32 patients were studied with T1-weighted SE and T2-weighted FSE sequences with and without fat suppression (FSE-CHESS and STIR-FSE). Quantitative analyses (metastasis size, signal intensity, margins and conspicuity) and qualitative analyses (artifacts and fat saturation homogeneity) were carried out of both fat-suppression sequences. Signal-to-noise (S/N) and contrast-to-noise (C/N) ratios were calculated in 20 metastatic lesions. The results were analyzed with the chi 2 method and the paired t-test.

RESULTS

Both fat-suppression FSE sequences were more sensitive to focal lesions (100%) than T1-weighted SE sequences (96.6%). Lesion signal was higher than that of surrounding bone in 95.5% of fat-suppressed images, which facilitated the recognition of spinal metastases. On the contrary, conspicuity was higher (73.3%) and the margins more definite (68.8%) on T1-weighted SE than on T2-weighted FSE sequences. Fat suppression was more apparent on STIR-FSE than on FSE-CHESS sequences, even with no significant difference in C/N ratio.

CONCLUSION

Both STIR-FSE and FSE-CHESS sequences are rapid and useful techniques to obtain fat saturation in FSE images. CHESS saturation is selective on fat signal, while STIR suppresses the signal of all the substances with the same short T1 as fat.

Accidental intrathecal injection of ionic water-soluble contrast medium: report of a case, including treatment

We report a patient who inadvertently received a small amount of meglumine diatrizoate intrathecally. The physiopathology and treatment of this kind of accident are discussed.

Technical note: CT scout views of the cervical spine in severely head-injured patients

The objective of this study was the validation of a CT multiprojection scout view method for the evaluation of cervical spine integrity in severely head-injured patients. Following brain CT, 130 consecutive patients underwent anteroposterior, laterolateral, and 45 degrees right and left oblique scout views of the cervical spine. The method allowed direct and prompt detection of traumatic lesions of the cervical spine in ten cases without moving the patients from the scanner table.

Cerebral magnetic resonance imaging: normal parameters of central nervous system in the pediatric age

Normal standards are required in order to evaluate minimal morphological changes in CNS disorders in childhood. We therefore investigated several morphometric parameters (white matter evaluation, ventricular and periencephalic liquoral spaces, septocaudate distance, Evans index, morphological evaluation of corpus callosum, Chamberlain line) in 52 non-neurological subjects by cerebral MRI.

[The reduction of ferromagnetic artifacts by using a fast-spin-echo sequence in the postoperative assessment of degenerative diseases of the cervical spine]

This study was aimed at investigating if fast spin echo (FSE) pulse sequences can increase the diagnostic capabilities of MRI in the patients with degenerative disease of the postoperative cervical spine, considering their lower magnetic susceptibility than that of conventional spin echo (SE) sequences. The patient population consisted of 15 patients submitted to diskectomy after Cloward and Caspar. MR images were acquired with a 1.5-T unit (Signa, General Electric) with T2-weighted FSE versus conventional T1- and T2-weighted SE images. Thanks to fewer metallic artifacts, FSE images of the postoperative cervical spine yielded more pieces of information than conventional SE sequences in demonstrating the spine and its content. The best results were obtained in the patients with canal stenosis (8 patients) and myelomalacia (2 patients). In addition, the myelographic effect, another major semiologic feature of the FSE technique, provided further diagnostic information in these patients. Moreover, shorter examination times resulted in better patients tolerance, especially in those with recent surgery. Finally, reducing motion, blood flow or CSF flow artifacts definitely improved FSE image quality.

[Magnetic resonance myelography with a fast-spin-echo sequence]

A major application of Magnetic Resonance Imaging (MRI) consists in the "myelographic effect", characterized by high signal intensity of the CSF, which permits to visualize spinal subarachnoid spaces and nerve root sheaths. Such new ultrafast pulse sequences as fast spin echo (FSE) further enhance CSF high signal intensity. In addition, suppressing background with the fat suppression technique and with maximum intensity projection (MIP), a particular algorithm already used in MR angiography, FSE sequences yield 3D myelography-like images. Our study was aimed at assessing the clinical role and the reliability of this technique. Our preliminary experience is based on 21 patients with pain in the lower back and legs and on 5 healthy volunteers; all the myelography-like images were obtained with a 1.5-T MR system (Signa, General Electric). The parameters for FSE myelography-like images included: TR = 6000, TE = 200, ETL = 32, thickness = 3 mm, matrix = 256 x 224, Nex = 4, FOV = 20 cm, fat presaturation, no phase wrap, acquisition time = 2 min 58 s. MR myelography sequences were acquired after a standard FSE T1/T2-weighted exam. MR-myelography results confirmed the diagnosis of disk herniation made on conventional T1/T2-weighted images, especially in thecal sac compression and/or amputation of nerve root sheaths. MR myelography appeared to be especially useful in migrated disk herniation or in abnormal origin of nerve roots. Moreover, it allowed full and panoramic visualization of the subarachnoid spaces and excellent definition of the thecal sac, nerve roots and nerve root sheaths. In one patient only movement artifacts affected image quality. To conclude, even though it fails to yield any functional information, MR myelography appears to be an easy, rapid and noninvasive support to conventional MRI of the lumbar spine, to replace conventional myelography.

Brain involvement in myotonic dystrophy: MRI features and their relationship to clinical and cognitive conditions

A prospective, case-control study was carried out on 25 patients with myotonic dystrophy (MyD) and 25 healthy subjects using brain magnetic resonance imaging (MRI). The frequency and severity of white matter hyperintense lesions (WMHL) and brain atrophy in MyD patients were compared with their clinical features and cognitive impairment using an extensive neuropsychological battery. Eighty-four per cent of MyD patients showed WMHL, compared with 16% of controls (p < 0.0001). These lesions involved all cerebral lobes, without hemispheric prevalence. Twenty-eight per cent of MyD patients also showed particular WMHL at their temporal poles. Myotonic patients had significantly more cortical atrophy than controls. No relationship between atrophy and WMHL was found on the MRI scans. The extent of brain abnormalities (WMHL or atrophy) was not correlated to age, disease duration, physical disability or severity of neuropsychological impairment. Central nervous system abnormalities revealed by MRI appear to be an almost constant feature of MyD, but they are not found to be related to clinical or cognitive parameters. Their nature is still unclear: some of them, located at the temporal poles, seem to be characteristic of the disease, while others small, diffuse WMHLs, similar to the age related alterations revealed by MRI occurring during young and adult age in MyD patients.

MRI and pathological examination of post-mortem brains: the problem of white matter high signal areas

We examined 21 brains from individuals more than 65 years of age by MRI and neuropathological methods to study the frequency and morphology of white matter changes. There were 16 brains from neurologically normal subjects (Group 1) while the remaining 5 (Group 2) had neurological disturbances. In Group 1 MRI showed high signal areas in the periventricular white matter in 12 brains and in the deep white matter in 9. All had focal areas, with confluent zones in 4; 3 cystic infarcts were also detected. Neuropathology in this Group showed periventricular changes of variable extent in all cases, vacuolated myelin around the perivascular spaces in 14 and degenerate myelin in 4. Macroscopic inspection showed 3 cystic lacunar infarcts, while areas of recent infarction were present on histology in 2. Four of the Group 2 brains had periventricular MRI changes; high signal areas in deep white matter were focal in 2 and confluent in 1. Cystic infarcts were detected in 3 cases. Neuropathology showed periventricular changes in all the brains; in 4 myelin around the perivascular spaces was vacuolated while degenerate myelin was demonstrated in 1. There were also old (1) and recent (2) lacunar infarcts. High signal areas in the white matter thus have different histological backgrounds but only in a minority of cases do they seem to be of pathological significance and, as a rule, they are not related to the presence of neurological disturbances. Correlative MRI-neuropathological studies are helpful for characterising abnormalities detected by techniques, like MRI, which are sensitive but not very specific.

Stroke in a young woman due to spontaneous bilateral internal carotid dissection. A case report

The present paper reports the case of a young woman who experienced an ischemic stroke due to the spontaneous dissection and occlusion of both internal carotid arteries, with recanalisation one year after the event. It is underlined that this form is not clinically different from the unilateral form, and that it is often associated with a favourable prognosis. In addition to the characteristic angiographic findings, the paper also highlights the importance of the combined use of MR, MR angiography and echo-Doppler imaging during diagnosis and follow up.

[Magnetic resonance in the pathologic evaluation of the isolated human brain]

The purpose of this study was to evaluate the interest of MRI of excised human brains before traditional pathological examination. MRI was performed on 40 formalin fixed brain specimen; the brains were placed on tap water in a plastic box, and submitted to standard MRI, 3D FT volume acquisition and multislice SE T1, PD and T2 weighted. The results of 3D FT volume acquisition were used for multiplanar reconstruction of planes according to the direction of anatomical structures. Our experience demonstrate that preliminary MRI of excised brains is possible because it does not alternate the results of following standard pathological examinations; the dissection may be focused on the MRI demonstrated pathology. MRI allows to correlate the results of the pathological examination of a slice with the state of the whole brain. An interesting option is the use of this method for medico-legal purpose.

MRI study of the corpus callosum using the Talairach grid

The authors show how the Talairach grid may be applied to MRI for the study of the topography of the corpus callosum. Thirty-eight patients with malformative syndromes and 53 controls were studied to demonstrate the reliability of this method.

[Three-dimensional computerized modelling of anatomical structures by computerized tomography imaging]

The authors built an automatic CT-driven device by which 3D models of biologic structures can be obtained. Original bidimensional densitometric data are recorded on tape and transferred to a mechanical computer-driven arm capable of cutting polystyrene slices reproducing the original biologic structures by means of an original software. The aim of our research was to assess the feasibility of such a device from a practical point of view and to analyze and solve related problems, in order to use the experience thus gained to develop more complex systems. We deliberately set up a device both technologically advanced and simple to be used even by non-specifically trained operators. The system capabilities open new perspectives in many application fields, such as surgery (stereotactic procedures, the making of personalized prostheses, plastic surgery, procedures planning and simulation), treatment (stereotactic radiotherapy), diagnostics (stereotactic biopsy) and educational use.

Electrophysiological and cognitive effects of lumbar myelography with iopamidol: comparison with diagnostic lumbar puncture

To assess the influence of contrast medium on cortical function, we studied 20 patients undergoing lumbar myelography with iopamidol and 10 patients undergoing diagnostic lumbar puncture (controls). The examinations performed before and 6 and 24 h after myelography (or lumbar puncture) included a neuropsychological battery and an electrophysiological evaluation. In the patients cranial CT was performed thrice to assess passage of contrast medium from the cerebrospinal fluid into the brain. Neither patients nor controls had significantly different scores on neuropsychological testing after the diagnostic examinations. A transient slowing of basal EEG activity could be detected in 2 patients and 3 controls 6 h after the lumbar puncture. In 3 patients CT showed a transient increase in density of the brain. None of the parameters studied was significantly affected by myelography with iopamidol. CT findings support the hypothesis of early clearance of iopamidol from brain tissue, explaining its low neurotoxicity.

[The current role of neuroradiology in evaluating malformation syndromes]

CT and MRI play complementary roles in the study of malformation syndromes in pediatric age: CT in particular is indispensable for adequately assessing the skeletal picture in subjects suffering from cranio-facial malformations, while MRI allows a morphological study and supplies informations on the maturation state of the white matter.

Morphological studies of the corpus callosum by MRI in children with malformative syndromes

A morphological analysis of the corpus callosum has been carried out in an MRI study of 34 children with malformative syndromes and 35 normal children. We used a new morphometric method based on measurement of five specific angles. Values outside the range of normality have been found in patients with malformations of the skull, including turricephaly, acrocephaly and frontonasal dysplasia. The results have confirmed the reliability of this method for study of the conformation of the corpus callosum and of its topographical relations with the other cerebral structures.

Acute monophasic focal demyelinating diseases of the central nervous system: longitudinal clinico-neuroradiological study of two patients

We report the clinical features and laboratory-instrumental findings in two patients with acute monophasic demyelinating disease with focal clinical expression: one case of incomplete cervical transverse myelitis and one of focal supratentorial encephalitis. We describe the clinical course and evolution of the neuroradiological findings (CT and MRI) and discuss their pathological meaning and diagnostic value.

Haemodynamic changes following carotid occlusion: MRI angiography and transcranial Doppler patterns

To see the signal changes in MR angiography (MRA) when occlusions or severe stenoses of carotid arteries occur and to relate these data with the velocity values provided by transcranial Doppler sonography (TCD), 20 patients showing symptomatic or asymptomatic unilateral carotid obstructions underwent both MRA and TCD after digital angiography investigation. No MRA signal was recorded immediately downstream from the carotid occlusion. Low flow velocity values in the carotid siphon and middle cerebral artery (MCA) ipsilateral to the carotid obstruction were associated with altered MRA signals corresponding to the same vessels. Turbulence phenomena induced by reversed flow in the anterior cerebral artery induced MRA signal impairments. In carotid occlusions, there may be a relationship between the MRA patterns and the flow velocity variations detected by TCD, but the two approaches have to be applied together since they provide complementary information.