[Indications for fetal magnetic resonance imaging]. / Indikationen zur fetalen Magnetresonanztomographie.

Indications to perform fetal magnetic resonance imaging (MRI) are composed of common ones related to methodological problems of ultrasound (US) assessment (such as for instance hydramnios) and special ones. The latter are related to MR capability of high-resolution soft tissue contrast and an extended field of view that allows visualization of the whole fetus, even in later stages of pregnancy. The most important indications include confirmation of US findings, work-up of malformations with respect to individual prognosis and genetic background, differentiation between acquired conditions and malformations, visualization of pathologies that have to be treated surgically immediately after birth, and morphological changes of the placenta.

Visualization of nonstructural changes in early white matter development on diffusion-weighted MR images: evidence supporting premyelination anisotropy.

BACKGROUND AND PURPOSE: Previously, we showed that diffusion-weighted MR imaging depicts evidence of directionally preferential water motion in white matter structures of developing rat brain before and after myelination, and considerably earlier than conventional imaging strategies. Present data augment these imaging and corresponding histologic findings with electron-microscopic corroboration. We additionally report the findings of a 10-day-old rat pup tested functionally by administration of the sodium-channel blocker, tetrodotoxin. METHODS: In two rat pups, drawn from the population reported previously, MR estimates of diffusion anisotropy of the optic nerves and chiasm were compared with histologic and electron microscopy results. To test the hypothesis that "premyelination" directional preference of water motion in white matter structures relates to sodium-channel activity, MR imaging was performed in a 10-day-old rat pup treated with the sodium-channel blocker, tetrodotoxin, and findings were compared with data from an age-matched control. RESULTS: Although diffusion anisotropy was present in optic structures of the youngest animal, myelin-sensitive histologic staining did not show myelin before 12 days; electron microscopy confirmed lack of any myelin or its precursors during the earliest maturational stage. Administration of tetrodotoxin to the 10-day-old rat-pup led to loss of diffusion anisotropy. CONCLUSION: Our findings provide two pieces of supporting data for the hypothesis that nonstructural changes are responsible for early anisotropic diffusion: electron microscopy shows no evidence of myelin despite diffusion anisotropy, and inhibiting the sodium-channel pump appears to remove the directional preference of water motion. Visualization of nonstructural "premyelination" consequences with diffusion-weighted imaging emphasizes its sensitivity and potential in studying early processes of brain development.

Diffusion-weighted MRI of myelination in the rat brain following treatment with gonadal hormones.

Previous studies have demonstrated the ability of high-resolution diffusion-weighted MRI to show maturation of white-matter structures in the developing rat brain. The purpose of this study was to investigate the influence of gonadal steroid hormones on the rate of this development. Starting from their second postnatal day, 16 rat-pups of either sex were repeatedly treated with subcutaneous implants containing 17-beta estradiol or delta-androstene 3,17 dione, respectively. Serial T1-, T2- and diffusion-weighted MRI was performed weekly for 8 weeks using a 4.7 T unit. Maturation of anterior optic pathways and hemisphere commissures was assessed. Diffusion-weighted images were processed to produce "anisotropy index maps", previously shown to be sensitive to white-matter maturation. Compared with untreated rat-pups, estrogen-treated animals showed accelerated, and testosterone-treated animals delayed maturation on anisotropy index maps and histological sections. In all animals, maturational changes appeared earlier on anisotropy index maps than on other MRI sequences or on myelin-sensitive stained sections. Diffusion-weighted imaging, and the construction of spatial maps sensitive to diffusion anisotropy, seem to be the most sensitive approach for the detection of maturational white-matter changes, and thus may hold potential for early diagnosis of temporary delay or permanent disturbances of white-matter development.

Identification of "premyelination" by diffusion-weighted MRI.

OBJECTIVE: The purpose of this study was to compare white matter maturation as demonstrated with diffusion-weighted MRI and with myelin-sensitive histological staining. MATERIALS AND METHODS: The diffusion-, T1-, and T2-weighted SE MRI at 4.7 T was performed weekly in a total of 16 rat pups, aged from 5 days to 8 weeks, 2 animals evaluated per week. Heavily diffusion-weighted sequences were obtained with the diffusion-sensitizing gradient switched alternately in two orthogonal directions. To enhance signal intensity of anisotropic structures, a synthesized image (referred to as the "anisotropy index map") was constructed from the ratio of pairs of images acquired with diffusion sensitization of identical magnitude but orthogonal direction sensitivity. The anisotropy index maps were used for comparison with T1-weighted and heavily T2-weighted SE sequences and histological sections, respectively. RESULTS: The first evidence of diffusion anisotropy on anisotropy index maps preceded initial myelin as well as neurofibril staining by 5-12 days and T2 shortening by 2 weeks. The T1-weighted sequences did not yield visible changes and were not helpful for the assessment of ongoing white matter maturation in this model. CONCLUSION: Magnetic resonance imaging signal intensity changes based on anisotropic water diffusion were demonstrated in regions of unmyelinated cerebral white matter tracts of albino rat pups before the onset of histologically detectable myelin. The ability of in vivo mapping of premyelinating white matter maturation indicates a new diagnostic use of MRI in evaluating cerebral white matter maturation.

The diagnostic value of magnetic resonance imaging for the detection of tumor recurrence in patients with carcinoma of the ovaries.

Disease status during follow-up evaluation of patients with carcinoma of the ovaries is the main criterion for the selection of appropriate management. A cohort analysis was performed to investigate if magnetic resonance imaging (MRI) could improve noninvasive assessment of disease status in patients with carcinoma of the ovaries during follow-up examination. Twenty-four women with carcinoma of the ovaries after primary surgical treatment with subsequent platinum containing chemotherapy were entered into the study. MRI was performed in addition to sonography and computed tomography (CT). Patients without evidence of disease underwent restaging laparotomy. Sensitivity of sonography, CT and MRI was 50, 63 and 75 percent, respectively. Combination of CT and MRI revealed a 75 percent sensitivity rate. Specificity for sonography, CT and MRI was 100, 94 and 94 percent, respectively, and for the combination of CT and MRI, 88 percent. Positive and negative predictive value and accuracy of these methods were 100, 80 and 83 percent for sonography; 83, 83 and 83 percent for CT; 86, 88 and 88 percent for MRI, and 75, 88 and 83 percent for the combination of CT and MRI. In one instance of false-negative sonographic and CT results, MRI detected recurrence located in postoperative scar tissue. In one instance, MRI did not add essential information to the other imaging methods. Therefore, MRI as a time- and cost-intensive procedure should be reserved for instances in which there are doubtful findings arising with other diagnostic tools, rather than as an indispensable routine procedure in the follow-up evaluation of patients with carcinoma of the ovaries.

MR assessment of brain maturation: comparison of sequences.

PURPOSE: To evaluate the role of short-inversion-time inversion-recovery (STIR) sequences in assessment of brain maturation. METHODS: Twenty-seven infants and young children with normal neurologic development were examined by 1.5-T MR using a circularly polarized head coil. Axial T1-weighted and T2-weighted and spin-echo and STIR images were obtained. Signal intensity of different anatomic structures at individual sequences was classified relatively to reference sites and temporal sequence of signal intensity was observed. RESULTS: Signal intensity changes on T1-weighted and T2-weighted spin-echo sequences occurred at ages described in various previous publications. On STIR images intensity changes became apparent at a time between T1-weighted and T2-weighted images. The advantages of the STIR sequence were improved assessment of myelination of subcortical cerebral white matter from 6 to 14 months and good contrast between white matter lesions and cerebrospinal fluid. CONCLUSION: Our results suggest that from 0 to 6 months myelination can be assessed best using a combination of T1-weighted and T2-weighted images; from 6 to 14 months a combination of T2-weighted and STIR images seems to be advantageous; after 14 months the use of only T2-weighted sequences is sufficient. After 14 months STIR images may be useful in detecting small periventricular white matter lesions or in cases with retarded myelination and isointensity between gray matter and white matter.

Posturographic measurement of body sway in survivors of severe closed head injury.

Postural imbalance was measured in 39 survivors of severe closed head injury 7 to 66 months after head injury using a posturographic platform. The results were compared with those derived from age-matched healthy control subjects. Severe postural imbalance, particularly in an anteroposterior direction, was found in 16 patients, whereas 9 patients showed moderate imbalance and 14 patients showed normal results in the posturographic investigation. Low initial Glasgow Coma Scale scores and deep parenchymal brain lesions demonstrated by magnetic resonance imaging were shown to be significant indicators of subsequent severe postural imbalance. The duration of posttraumatic amnesia, the localization and size of cortical contusions and subcortical white matter lesions, on the contrary, were not associated with postural imbalance in the long-term outcome.

Cranial MR imaging and cerebral 99mTc HM-PAO-SPECT in patients with subacute or chronic severe closed head injury and normal CT examinations.

Eighteen patients in the subacute or chronic state following severe closed head injury with normal cranial CT scans were examined by MR and 99mTc HM-PAO SPECT. Correlations were sought between these 2 imaging modalities and the clinical outcome, as defined by the Glasgow Outcome Scale (GOS) score. Both MR and SPECT revealed cerebral damage in all patients examined but structural and functional alterations did not coincide topographically in 64.9% of lesions. Nevertheless, complementary injury patterns suggesting poor recovery were found; cortical contusions and diffuse axonal injury (MR) in conjunction with cortical and thalamic hypoperfusion (SPECT) were noticed in 8 out of 12 patients with unfavorable outcome (GOS = III and IV). The synthesis of MR and SPECT information clearly enhanced the ability both to accurately assess posttraumatic brain damage and to improve patients' outcome prediction.

Polymyositis: MRI-appearance at 1.5 T and correlation to clinical findings.

The thigh regions of 10 patients suffering from polymyositis were examined by magnetic resonance imaging (MRI) at 1.5 T; follow-up examinations were performed in all patients. MRI findings were correlated with findings at physical examination and serological parameters. In four patients focal areas of hyperintensity on T2-weighted (T2W) spin echo (SE) images were found within muscles. They were not detectable on T1-weighted (T1W) images. In three of these cases enhancement within the musculature was seen following i.v. administration of Gd-DTPA on T1W images. In another five patients there was varied replacement of muscle by fatty tissue. In one patient the muscle appeared completely normal. On follow-up three patients showed definite changes in imaging findings; two correlated well with clinical and biochemical findings while the third exhibited massive deterioration clinically with mild improvement on imaging. Seven patients exhibited no change on MRI; four of these had shown a significant clinical change in the course of the disease, whilst three were clinically stable. In our small series MRI using SE technique (T1W and T2W) and contrast enhancement to date seems to be of limited value for the assessment of muscular changes during therapy. The i.v. use of Gd-DTPA did not add to MRI's diagnostic value in this series.

CT and MR accuracy in the detection of tumor recurrence in patients treated for ovarian cancer.

OBJECTIVE: The aim of this prospective study was to evaluate the accuracy of clinical examinations (palpation/determination of serum tumor-associated antigen CA125 level), CT, and MRI in the detection of tumor recurrence in patients with treated ovarian cancer. MATERIALS AND METHODS: Twenty-four patients who had been treated for ovarian carcinoma were prospectively examined by clinical means (palpation/serum tumor-associated antigen CA125 level), CT, and MRI to assess their accuracy in detecting recurrent disease; results were correlated with surgical/bioptic/pathoanatomic findings. Nine patients had relapse; 15 women were disease-free. RESULTS: Examinations were true-negative in 14 patients (on palpation/CA125, CT, and MRI) and true-positive in 9 on palpation/CA125, in 6 on CT, and in 7 patients on MRI. False-positive examinations occurred in one patient on palpation/CA125, CT, and MRI and false-negative in zero on palpation/CA125, in three on CT, and in two on MRI, a sensitivity of 100% for palpation/CA125, 66.6% for CT, and 77.7% for MRI and a specificity of 93.3% for palpation/CA125, CT, and MRI. Accuracy of palpation/CA125 examinations was 95.8% in comparison with 83.3% for CT and 87.5% for MRI. CONCLUSION: Our results suggest that in the follow-up of ovarian cancer patients, assessment of serum tumor-associated antigen CA125 level is accurate in the determination of patients with tumor recurrence. Computed tomography is the primary imaging modality to prove macroscopic disease recurrence and can spare these patients from invasive restaging second-look laparotomy; MRI should be performed in women with questionable macroscopic recurrent tumor and negative CT examination. Neither CT nor MRI can confidently exclude microscopic disease.

Superparamagnetic particles as oral contrast medium in magnetic resonance imaging of patients with treated ovarian cancer--comparison with plain MRI.

In 23 patients with treated ovarian cancer, 24 magnetic resonance (MR) examinations of the abdomen and pelvis were performed before and after administration of an oral superparamagnetic contrast medium. Depiction of bowel loops was judged sufficient in 47% with plain scans and in 85% with enhanced scans. Minor artefacts attributed to the agent were noted in 32% of examinations and were classified as disturbing in 8%. The diagnostic information obtained after contrast enhancement was estimated to be superior to that from plain MRI in 20% of patients. The use of oral contrast medium did not alter the MR diagnosis of "tumour recurrence" or "disease-free" in any patient. Our results suggest that superparamagnetic iron oxide is an effective and reliable approach to negative bowel contrast enhancement, increasing the confidence level when distinguishing intestines from solid structures.

Wilson's disease: evidence of subgroups derived from clinical findings and brain lesions.

Using exploratory factor analysis, we prospectively investigated neuropsychiatric symptoms and structural brain lesions of 47 patients with proven Wilson's disease and identified three subgroups. The first subgroup clinically exhibited bradykinesia, rigidity, cognitive impairment, and an organic mood syndrome and by MRI showed a dilatation of the third ventricle. The second subgroup was characterized by ataxia, tremor, reduced functional capacity, and focal thalamic lesions. The third subgroup showed dyskinesia, dysarthria, an organic personality syndrome, and focal lesions in the putamen and in the pallidum.

Haemorrhage in intracerebral arteriovenous malformations: detection with MRI and comparison with clinical history.

Fifty-one patients with 59 angiographically proven cerebral arteriovenous malformations (AVMs) were examined by high-field MRI to detect blood breakdown products. Results were correlated with the history of intracranial bleeding. Evidence of previous episodes of haemorrhage was seen in 10 of 12 patients (83.3%) with verified bleeding, in 4 of 9 patients (44.4%) with symptoms which could suggest bleeding and in 6 of 30 patients (20%) with negative histories. Because of the known rebleeding rate and the increased risk of associated complications, identification of the subgroup who had had haemorrhage and should therefore be considered for surgery may be beneficial. MRI can make a contribution to management by demonstrating prior haemorrhage in patients with an inadequate clinical history.

Case report: lipoma of the liver--ultrasound, CT and MR imaging.

A case of lipoma of the liver is presented; ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI) findings are reviewed and compared with previous reports. The ultrasound pattern and appearance of the tumour in CT as well as MRI are discussed.

CT in pancreatic involvement of non-Hodgkin lymphoma.

In an attempt to evaluate characteristic CT features of primary pancreatic involvement in non-Hodgkin lymphoma (NHL), scans of 10 patients were reviewed retrospectively and compared to 50 patients with histologically proved different neoplasms of the pancreas. Setting the correct diagnosis of NHL would be essential for planning of treatment and prognosis. CT findings of NHL were characteristic but not specific. Nevertheless, the presence of a homogeneous pancreatic mass with a diameter of 7 cm or more, infiltrating surrounding tissue accompanied by retroperitoneal and/or mesenteric lymphadenopathy strongly suggests NHL. CT-guided needle biopsy can help to establish the diagnosis of pancreatic NHL.

MR contrast arthrography (MRA) in osteochondrosis dissecans.

Osteochondrosis dissecans (OCD) is a lesion that characteristically affects the articular cartilage and subchondral bone with the potential of fragmentation and separation. Exact assessment of cartilaginous and subchondral bony changes is mandatory for the planning of adequate treatment. Therefore, we examined 25 knees using spin echo (SE) and gradient echo (GE) sequences on a 1.5 T superconducting unit prior to and following intraarticular administration of 40 ml of a 2 mmol/L Gd-DTPA solution (MR arthrography). For evaluation (staging) a modified Clanton and DeLee scheme was employed. Verification by arthroscopy or arthrotomy was available in 24 cases. A correct diagnosis of OCD with regard to its type prior to intraarticular injection of Gd-DTPA was possible in 39.3% using T1-weighted SE sequences and in 57.4% on GE sequences. After intraarticular administration of Gd-DTPA, the rate of correct diagnoses improved to 92.9% on T1-weighted SE sequences and 100% on GE sequences. Magnetic resonance arthrography appears to be helpful for the exact assessment of the articular cartilage overlying OCD lesions as well as for the differentiation between partial and complete separation of cartilaginous or osteocartilaginous fragmentations.

High-resolution real-time sonography and MR imaging in assessment of osteocartilaginous exostoses.

High-resolution real-time ultrasonography (US) and MR imaging, using both spin-echo (SE) and gradient-echo (GE) sequences, were performed prospectively in 14 patients with solitary osteocartilaginous exostoses to assess cartilage cap thickness and bursa formation. Results were compared to surgical and histopathologic findings in all cases. Both US and MR imaging were useful in evaluating exostotic cartilage cap thickness, which is supposed to be the most reliable sign of malignant transformation. Hyaline cartilage matrix had distinctive features in US and MR imaging caused by its specific histologic composition. The formation of bursae over the protruding exostoses, which results in pain and clinically could raise the suspicion of growth and malignant transformation, was demonstrated best using GE sequences. MR imaging was thus superior to US in the detection of bursa formation.

[The percutaneous catheter drainage of pancreatic pseudocysts]. / Perkutane Katheterdrainage von Pankreaspseudozysten.

The results of CT/US-guided percutaneous drainage in 35 patients with pancreatic pseudocysts are reported. 27 patients recovered without surgery and no further treatment was required. 8 patients required a subsequent surgery due to recurrence. The role of CT/US-guided percutaneous drainage in pancreatic pseudocysts as well as an analysis of the technical aspects associated with a successful procedure are discussed. Although US may be used, we believe CT is safer and allows more precise localisation and guidance in the treatment of pseudocysts.