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Fetal MR imaging often poses a diagnostic challenge for the radiologist. Both fetal anatomy and pathology differ decidedly from pediatric and adult MR imaging. While ultrasound remains the method of choice for screening examinations of the fetus, MR imaging is playing an increasingly important role in the detection and classification of malformations not diagnosable by ultrasonography alone. Recently, advances in fast single-shot MR sequences have allowed high-resolution, high-quality imaging of the moving fetus. Preferable sequences to be applied are a true fast imaging steady precession (true-FISP) or a half-Fourier acquired single-shot turbo spin-echo (HASTE) sequence. Premedication is generally no longer required. In all fetal MR imaging, every aspect of fetal anatomy has to be scrutinized. Subsequently, any abnormalities need to be described and classified. A close collaboration with the referring obstetrician is of paramount importance.

Purpose: Evaluation of the accuracy of a new electromagnetic target system for interventional CT-guided procedures with virtual navigation in a previously acquired helical CT., Material and Methods: The new target system CT-Guide 1010 (Ultraguide, Tirat Hacarmel, Israel) for CT-guided interventions was adapted to the video signal of the Somatom Plus 4 and Volume Zoom (Siemens, Erlangen, Germany). A helical CT-dataset including skin-based sensor cubes was transferred to the integrated navigation system inside the scanner room. 50 image-guided interventions and biopsies were performed outside the gantry using virtual navigation to reach the lesion. The accuracy of the procedures was evaluated using documentation of the needle tip with CT-fluoroscopy, results of histology, and follow-up., Results: The deviation between planned and documented needle tip was 2.2 +/- 2.1 mm in 50 procedures. Time between the end of planning-CT and needle positioning using the system was 13 minutes. There were no complications due to the use of the system., Conclusion: The CT-Guide allows for virtual real-time navigation with high accuracy. Advantages are the free needle angulation without gantry tilt, use of optimal CT perfusion phase for virtual navigation, and reduction of radiation exposure to the patient and interventionalist.

Background and Purpose: Differentiating acute benign from neoplastic vertebral compression fractures can pose a problem in differential diagnosis on routine MR sequences, as signal changes can be quite similar. Our purpose was to assess the value of increasing the diffusion weighting of a diffusion-weighted steady-state free precession (SSFP) sequence for differentiating these two types of vertebral compression fractures., Methods: Twenty-nine patients with 32 acute vertebral compression fractures caused by osteoporosis (n = 15) or malignancy (n = 17) were examined with a diffusion-weighted SSFP sequence, a T1-weighted spin-echo sequence, and a short-inversion-time inversion recovery sequence. The SSFP sequence was performed with increased diffusion weighting (delta = 0.6, 3.0, 6.0, and 9.0 ms). The signal intensities of the fractured vertebral bodies were rated on a five-point scale from markedly hypointense to markedly hyperintense relative to normal adjacent vertebral bodies. Quantitative analysis was performed by region-of-interest measurements and by calculating the bone marrow contrast ratio. Statistical analysis was performed with the Mann Whitney U test and Student's t test., Results: At delta = 3 ms, the osteoporotic fractures yielded hypointense signal in seven cases, isointense signal in six, and hyperintense signal in two. The fractures showed a progressive signal loss with increased diffusion weighting, so that hypointensity was reached in all but one case. All metastatic fractures had hyperintense signal with delta = 3 and 6.0 ms. With delta = 9.0 ms, four fractures became isointense., Conclusion: Increasing diffusion weighting can reduce false-positive hyperintense osteoporotic fractures or make hypointensity more obvious in cases of osteoporotic fractures.

Background and Purpose: Stroke symptoms are caused in 10 to 15% by intracerebral hemorrhage. From the clinical examination it is often impossible to differentiate intracerebral hemorrhage from cerebral ischemia. To exclude intracerebral hemorrhage as the cause of clinical symptoms a CT is usually performed. The aim of our study was a direct comparison of the sensitivity of Computed Tomography and MRI using different MR sequences for the detection of acute intracerebral hemorrhage., Methods: In 8 male Wistar rats intracerebral hemorrhage was induced by infusion of collagenase into the caudate nucleus. After 1hour the brains were subsequently imaged with CT and MRI using T2- and T1-weighted Spin Echo sequences, diffusion-weighted sequences, T2*-weighted gradient echo sequences and FLAIR-sequences. Visibility of the intracerebral hemorrhage was examined using a scoring system from 1 = not visible to 5 = excellent visible. Finally, the intracerebral hemorrhage was verified by histological staining., Results: In all animals, intracerebral hemorrhage was visible in T2*-weighted gradient echo and diffusion weighted MR images 1 h after infusion of collagenase. T2- and PD-weighted SE images were positive in 7/8 rats. T1-weighted images revealed signal changes in 5/8 rats, and FLAIR sequence was positive in 8/8 rats. In CT intracerebral hemorrhage was only visible in 3/8 rats. When measuring the increase of Hounsfield units within the suspected hemisphere we saw a mean increase of 7% compared to the normal hemisphere in 3/8 rats., Conclusions: In this animal model, T2*-weighted magnetic resonance imaging proved to be the most sensitive imaging modality in the detection of acute intracerebral hemorrhage and is by far more sensitive than CT.

We report bilateral oedema and haemorrhagic transformation in the basal ganglia of a 59-year old woman with severe diabetic ketoacidosis. Lack of cerebral vascular autoregulation, followed by blood-brain barrier disruption due to the so-called breakthrough mechanism is presumed to be the cause.

Background and Purpose: Recently, the diagnostic and therapeutic importance of repeat radiologic imaging in stroke patients has been questioned. The aim of this study was to show the therapeutic and diagnostic consequences of both repeat brain imaging and follow-up vascular imaging in this group of patients., Methods: Neuroradiologic images and reports as well as clinical records of 317 patients (209 men and 108 women; mean age, 63 years) were reviewed retrospectively to determine the number of modifications made to the diagnosis and therapeutic regimen and to the classification of neuroradiologic findings., Results: Two hundred thirty-eight repeat imaging procedures were performed in 171 patients. Of these, 76 were vascular imaging examinations (11 CT angiograms, 13 MR angiograms, 52 digital subtraction angiograms) and 162 were cross-sectional brain imaging studies (54 MR images, 108 CT scans). Forty of the 76 vascular imaging procedures and 77 of the 162 repeat cross-sectional brain imaging studies led to important diagnostic modifications with consequences for the patients' therapy and prognosis., Conclusion: Our study establishes that vascular imaging methods as well as cross-sectional brain imaging used as repeat imaging procedures in stroke patients can have important diagnostic and therapeutic consequences. We believe that repeat imaging in selected subgroups will be cost-effective.

Purpose: To evaluate the relative value of magnetic resonance (MR) imaging versus computed tomography (CT) in the diagnosis of inflammatory paranasal sinus disease., Materials and Methods: In 30 patients suspected of having or known to have inflammation of the paranasal sinuses, both coronal CT and coronal T1-weighted, three-dimensional, gradient-echo MR imaging of the paranasal sinuses were performed. Visualization of anatomic details, kind and extent of inflammatory disease, and artifacts from dental work were scored. The scores were compared by using the Wilcoxon matched pairs signed rank test. Interexamination agreement between the two methods was calculated by using a kappa analysis., Results: Most bone structures of the infundibular complex were significantly better visualized at CT than at MR imaging. Orbital and brain anatomy were visualized better at MR imaging than at CT. No artifacts from dental work occurred in diagnostically relevant regions at MR imaging. There was a substantial to almost perfect agreement between CT and MR imaging for every kind and extent of the disease except for mucosal thickening in the maxillary and frontal sinuses, in the nasal cavity, and in the infundibulum., Conclusion: CT is superior to MR imaging in the depiction of fine bony details and anatomic variants and thus is superior to MR imaging in helping plan functional endoscopic sinus surgery. However, there are patient groups in which MR imaging can be used as a primary tool in screening for sinusitis.