Optimization of Scan Time in MRI for Total Hip Prostheses: SEMAC Tailoring for Prosthetic Implants Containing Different Types of Metals.

INTRODUCTION: Magnetic resonance imaging (MRI) of soft tissues after total hip arthroplasty is of clinical interest for the diagnosis of various pathologies that are usually invisible with other imaging modalities. As a result, considerable effort has been put into the development of metal artifact reduction MRI strategies, such as slice encoding for metal artifact correction (SEMAC). Generally, the degree of metal artifact reduction with SEMAC directly relates to the overall time spent for acquisition, but there is no specific consensus about the most efficient sequence setup depending on the implant material. The aim of this article is to suggest material-tailored SEMAC protocol settings. MATERIALS AND METHODS: Five of the most common total hip prostheses (1. Revision prosthesis (S-Rom), 2. Titanium alloy, 3. Müller type (CoNiCRMo alloy), 4. Old Charnley prosthesis (Exeter/Stryker), 5. MS-30 stem (stainless-steel)) were scanned on a 1.5 T MRI clinical scanner with a SEMAC sequence with a range of artifact-resolving slice encoding steps (SES: 2-23) along the slice direction (yielding a total variable scan time ranging from 1 to 10 min). The reduction of the artifact volume in comparison with maximal artifact suppression was evaluated both quantitatively and qualitatively in order to establish a recommended number of steps for each case. RESULTS: The number of SES that reduced the artifact volume below approximately 300 mm(3) ranged from 3 to 13, depending on the material. Our results showed that although 3 SES steps can be sufficient for artifact reduction for titanium prostheses, at least 11 SES should be used for prostheses made of materials such as certain alloys of stainless steel. CONCLUSION: Tailoring SES to the implant material and to the desired degree of metal artifact reduction represents a simple tool for workflow optimization of SEMAC imaging near total hip arthroplasty in a clinical setting. KEY POINTS: Five of the most common total hip prostheses have been investigated in vitro. Tailored SEMAC protocols - in terms of scan duration - have been determined. Tailoring was similar for T1-weighted and inversion recovery SEMAC MRI. The suggested prosthesis-related SEMAC adaptation shortens clinical scan times.

Transthoracic sonography for the detection of pulmonary embolism--a meta-analysis.

PURPOSE: Radiation protection is a major issue since the implementation of MSCT technology and its widespread indication for the detection of various diseases. In a European-wide trial (SECT) meta-analyses of imaging alternatives to CT have been initiated. This paper focuses on the diagnostic performance of transthoracic ultrasound (TUS) for the diagnosis of pulmonary embolism (PE) (5 studies, 652 patients). MATERIALS AND METHODS: Medical literature (from 1990 to 2006) in PubMed and EMBASE databases was searched for articles on studies that used TUS as diagnostic tests for PE. Studies were included if they reported the positive and negative rates of PE diagnoses from TUS compared with the rates of PE in CT, MRI or a combination of diagnostic tests. Two readers assessed the quality of the studies. RESULTS: Pooled sensitivity and specificity of TUS for PE were 80 % (95 % CI: 75 %, 83 %) and 93 % (95 % CI: 89 %, 96 %), respectively. CONCLUSION: In the time of MSCT, TUS is an imaging modality that is no longer part of recent diagnostic algorithms for the diagnosis of PE. Considering the increasing number of requested CT examinations and therefore increasing collective radiation dose, this meta-analysis shows that TUS is a diagnostic alternative for special clinical settings in the work-up of suspected PE that seems to have fallen into oblivion.

Total-body contrast-enhanced MRA on a short, wide-bore 1.5-T system: intra-individual comparison of Gd-BOPTA and Gd-DOTA.

Total-body contrast-enhanced MRA (CE-MRA) provides information of the entire vascular system according to a one-stop-shop approach. Short, wide-bore scanners have not yet been used for total-body CE-MRA, probably due to their restricted field of view in the z-direction. The purpose of this feasibility study is to introduce an image protocol for total-body MRA on a short, wide-bore system. The protocol includes five to six table-moving steps and two injection runs. Two pharmacologically different contrast materials (CM) were applied in ten healthy volunteers in view of possible CM-dependent influences on the protocol outcome (Gd-Bopta, Gd-Dota). Differences consisted of significantly higher CNR with Gd-Bopta with a mean of 73.8+/-38.7 versus 69.1+/-34.3 (p=0.008), significantly better arterial visualization values with Gd-Dota with a mean of 1.26+/-0.44 versus 1.53+/-0.73 (p=0.003) and a tendency to less venous overlay with Gd-Dota, mean 1.19+/-0.44 and 1.34+/-0.72, respectively (p=0.065) (two-tailed Wilcoxon matched-pairs test). Overall 94% of the steps were valued as qualitatively excellent or good. The good results with both CM suggest a transfer to further patient evaluation.

[Hypertension and hyperhidrosis. Pheochromocytoma]. / Hypertonie und Schwitzen. Phaochromozytom.

A 39-year-old woman was referred to our hypertension clinic with refractory hypertension. The patient history gave certain clues for pheochromocytoma. The diagnosis was proven with elevated metanephrines and computer tomography. The tumor was surgically removed.

[Kissing osteochondroma of the lower limb]. / Kissing Osteochondrom--wenn Knochen sich küssen.

As definition, a "kissing" osteochondroma is a typical new bony formation with erosion on the adjacent paired bone, provoked by pressure of the outgrowth. Further diagnostics for incidentally diagnosed solitary osteochondroma should be performed only in cases where malignant transformation is suspected.

Intracranial hypotension due to leakage of cerebrospinal fluid: could myelography be a therapeutic option?

Spontaneous intracranial hypotension (SIH) is an uncommon condition caused by cerebrospinal fluid leakage. We report of a 29-year-old woman with typical symptoms in whom initial cranial MRI and CT were normal . A clinical diagnosis of SIH, but the symptoms did not resolve with conservative therapy or a lumbar epidural blood patch. Repeat MRI revealed (indirect) findings consistent with SIH but failed to directly demonstrate a cerebrospinal fluid fistula. Subsequent CT myelography revealed leakage of contrast medium into the epidural space bilaterally along the nerve roots at C3-7. Following the myelography the patient reported dramatic clinical improvement with complete resolution of symptoms. The adhesive quality of the myelographic contrast medium might have precipitated closure of the meningeal tears. Myelography may be not only of diagnostic value but also therapeutic in SIH.

Functional outcome after surgical treatment of intramedullary spinal cord tumors: experience with 78 patients.

OBJECTIVE: To analyze factors with impact on the functional outcome for patients with surgically treated intramedullary spinal cord tumors (IMSCT) and to point out characteristics of the different histological entities. SETTING: Neurosurgical Department, University of Essen, Germany. METHODS: Between 1990 and 2000, a consecutive series of 78 patients were referred to our institution and underwent surgical treatment. There were 46 (59%) male and 32 (41%) female patients. Mean age was 43.3 years. Functional outcome was analyzed depending on histological features, age, tumor localization and the extension of involved spinal segments. The mean follow-up period was 34.4 months. Operative removal of the IMSCT was performed under standard microsurgical conditions with intraoperative monitoring of somatosensory-evoked potentials (SSEP). RESULTS: The most frequently involved localization was the cervical and cervicothoracic region (55%) followed by the thoracic region (32%) and the medullar conus (13%). The most frequent IMSCTs were neuroepithelial tumors in 44 patients (56.5%) including 32 patients with ependymomas, 15 astrocytomas, and two lesions without further histological classification. Non-neuroepithelial tumors included 10 metastases, nine cavernomas, eight hemangioblastomas, one dermoidal cyst and one enterogenetic cyst. Complete tumor removal was achieved in 65 cases (83.3%) and subtotal resection in nine cases. In four cases a biopsy was performed only. The overall postoperative neurological state was improved or unchanged in 51 patients (65.4%) and worsened in 27 patients (34.6%). A favorable functional outcome was observed in 94.1% of patients with vascular tumors, in 61.3% of patients with low-grade neuroepithelial tumors and in 53.3% of patients with malignant tumors. CONCLUSIONS: The strongest predicting factor of functional outcome was the preoperative neurological condition beyond the histological differentiation of the IMSCT. Although there was no outcome difference with respect to the age and tumor extension, thoracically located IMSCTs proved to harbor an increased risk of postoperative surgical morbidity.

Whole-body fluorine-18 fluordeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in staging of advanced uveal melanoma.

Fluorine-18 fluordeoxyglucose positron emission tomography (FDG-PET) is an useful tool in diagnosing and monitoring of malignant cutaneous melanoma. However, the feasibility and usefulness of FDG-PET in uveal melanoma is not yet established. We present a patient with suspected advanced uveal melanoma who underwent combined FDG-PET/computed tomography (CT) for staging. FDG-PET/CT images demonstrated vital intraocular tumor. Anatomical assignment of the malignancy to the choroid was possible by means of the coregistered computed tomography. Furthermore, PET revealed an unknown otherwise undetected vital liver metastasis. We conclude that combined FDG-PET/CT has potential to further improve staging and therapy planning in patients with advanced uveal melanoma.

[Intracranial aneurysms: pathogenesis, rupture risk, treatment options]. / Intrakranielle Aneurysmen: Entstehung, Rupturrisiko, Behandlungsoptionen.

Non-invasive or minimal invasive imaging techniques, such as CTA and MRA, are widely used and lead to an increasing number of incidentally diagnosed intracranial aneurysms. This review answers questions regarding pathogenesis, risk of rupture and treatment options. In conclusion, treatment guidelines based on the individual's risk profile are presented.

Magnetic resonance imaging of nude mice with heterotransplanted high-grade squamous cell carcinomas: use of a low-loaded, covalently bound Gd-Hsa conjugate as contrast agent with high tumor affinity.

RATIONALE: Malignant tumors often show an increased uptake and metabolism of plasma proteins, especially albumin. OBJECTIVES: Determine whether the accumulation of low loaded Gd-albumin improves visualization of malignant tumors by MRI. METHODS: Twelve nude mice with heterotransplanted squamous cell carcinomas were studied. The signal intensity of tumor, blood, liver, kidney and muscle tissue was studied in MR images after application of Gd-albumin during a period of 144 hours. MRI results were histologically correlated after simultaneously injection of Gd- and fluorescein-labeled albumins in 9 nude mice. RESULTS: Although liver and kidney had a maximum increase in signal intensity within 30 minutes, tumors showed a delayed 51% increase in the 24 hours after application. Histologic and fluorescence evaluation demonstrated albumin localization in tumors predominantly in stroma and necroses. CONCLUSIONS: Gd-albumin is efficiently accumulated in SCC transplants. MRI with low loaded Gd-albumin may offer relevant opportunities for recognizing tumors sensitive to a therapy with cyostic drug-labeled albumins.

Aneurysmal rupture during embolization with Guglielmi detachable coils: causes, management, and outcome.

BACKGROUND AND PURPOSE: Aneurysmal rupture during endovascular treatment is one of the most feared complications of endovascular aneurysm therapy. The purpose of this study was to determine the frequency, causes, management, and outcome of aneurysmal rupture that occurred during treatment with Guglielmi detachable coils (GDCs) in an unselected series of patients with ruptured cerebral aneurysms. METHODS: Between July 1997 and December 2000, we treated 164 acutely ruptured cerebral aneurysms with GDCs. All charts were reviewed, and patients with aneurysmal rupture occurring during embolization were identified. RESULTS: Five patients had an intraprocedural aneurysmal rupture. In one patient, rupture was due to guidewire perforation of the wall. In two patients, the microcatheter itself perforated the aneurysm. In another two patients, rupture occurred during placement of the first coil. Endovascular packing was continued in all patients. One patient died as a result of the aneurysmal rupture. No negative long-term effects were observed in the remaining four patients. In summary, we observed intraprocedural aneurysmal rupture in 3% of our patients, with a mortality rate of 20% and no long-term morbidity. CONCLUSION: Aneurysmal rupture during endovascular treatment with GDCs is a rare event; clinical severity may be variable. Embolization of the aneurysm can be continued in most cases, and most patients with treatment-related subarachnoid hemorrhage survive without serious sequelae.

Monocrystalline iron oxide nanoparticles: possible solution to the problem of surgically induced intracranial contrast enhancement in intraoperative MR imaging.

BACKGROUND AND PURPOSE: Intraoperative MR imaging is increasingly being used to control the extent of surgical resection; however, surgical manipulation itself causes intracranial contrast enhancement, which is a source of error. Our purpose was to investigate the potential of monocrystalline iron oxide nanoparticles (MIONs) to solve this problem in an animal model. METHODS: In male Wistar rats, surgical lesions of the brain were produced. The animals underwent MR examination immediately afterward. In the first group, a paramagnetic contrast agent was administered, whereas the second group of animals received MIONs 1 day before surgery. In a third group of animals, malignant glioma cells were stereotactically implanted in the caudoputamen. Two weeks later, MIONs were IV injected and the tumor was (partially) resected. Immediately after resection, MR examination was performed to determine the extent of residual tumor. RESULTS: Surgically induced intracranial contrast enhancement was seen in all animals in which a paramagnetic contrast agent was used. Conversely, when MIONs had been injected, no signal changes that could be confused with residual tumor were detected. In the animals that had undergone (partial) resection of experimental gliomas, MR assessment of residual tumor was possible without any interfering surgically induced phenomena. CONCLUSION: Because MIONs are stored in malignant brain tumor cells longer than they circulate in the blood, their use offers a promising strategy to avoid surgically induced intracranial contrast enhancement, which is known to be a potential source of error in intraoperative MR imaging.

[Can superparamagnetic contrast media improve MRI-tomographic images of experimental gliomas?]. / Verbessern superparamagnetische Kontrastmittel die MR-tomographische Abgrenzbarkeit experimenteller Gliome?

PURPOSE: To investigate whether the margins of microscopic tumors can be delineated better with monocrystalline iron oxide nanoparticles (MION), a superparamagnetic contrast medium, than with Gd-DTPA by magnetic resonance imaging (MRI). METHODS: MRI and histological examinations were conducted in 28 Wistar rats with sterotactically implanted gliomas (C6 gliomas). Of the 28 animals, 14 were examined after intravenous administration of MION [nine animals received 179 mmol Fe/kg body weight (dose 1), and five, 893 mmol Fe/kg (dose 2)]. The other 14 animals were examined first after i.v. administration of Gd-DTPA (0.2 mmol/kg) and then after i.v. administration of MION. The extent of the tumors as seen on MRI and at histological study were compared. RESULTS: Iron particles were identified microscopically in tumor cells and in the tumoral interstitium. After administration of MION at dose 1, the contrast-enhanced area of tumor was 1.55-fold greater than the extent of tumor identified by histological study, at dose 2,2.15-fold. Compared with Gd-DTPA the area of contrast enhancement was greater by a factor of 1.38 with MION administration at dose 1 and by a factor of 1.91 at dose 2. CONCLUSION: MION provides intra- and extracellular contrast enhancement. The area of the contrast-enhanced tumor is dose-dependently greater with MION than with Gd-DTPA and also greater than the extent of tumor seen at histological study.

[Effect of brain edema on the recurrence pattern of malignant gliomas]. / Einfluss des Hirnödems auf das Rezidivwachstum maligner Gliome.

PURPOSE: To assess the influence of initial preoperative brain edema in malignant gliomas on regrowth patterns. SUBJECTS AND METHODS: 79 patients with histologically verified supratentorial malignant glioma were prospectively studied by magnetic resonance imaging (MRI) before and every 2-3 months after surgery. The median follow-up time was 11 months. We correlated the configuration of the initial vasogenic edema on T2-weighted images with tumor regrowth patterns on contrast-enhanced T1-weighted images. RESULTS: 35/47 tumor regrowths (75%) imitated the initial edema configuration, while 11/47 occurred within the initial tumor bed; in one case tumor recurrence was multilocal. CONCLUSION: In glioblastoma, tumor regrowth patterns correlate positively with the configuration of the initial vasogenic brain edema. The initial, "presurgical" peritumoral edema should thus be considered when planning further treatment.

[Follow-up monitoring with magnetic resonance tomography after decompressive trephining in experimental "malignant" hemispheric infarct]. / Magnetresonanztomographisches Verlaufsmonitoring nach Entlastungstrepanation beim experimentellen "malignen" Mediainfarkt.

Acute ischemia in the complete territory of the carotid or the middle cerebral artery may lead to cerebral edema with raised intracranial pressure and progression to coma and death. Although clinical data suggest benefit for patients undergoing decompressive surgery for massive space occupying hemispheric stroke, little data about the effects of this procedure on morbidity and outcome is available. The experimental data support an early surgical approach. For early and probably most effective treatment of severe, space-occupying cerebral ischemia, the "malignant" character of the brain edema has to be recognized early after onset of vessel occlusion. Hereby magnetic resonance imaging (MRI) may allow to determine the clinical significance of brain edema early after onset, simultaneously allowing to monitor the evolution of ischemia. We performed serial SE-MRI in rats with acute hemispheric infarctions treated by decompressive craniectomy. Focal cerebral ischemia was induced in 36 rats using an endovascular occlusion technique. Decompressive craniectomy was performed 4 and 24 hours after vessel occlusion in groups of 12 animals each. Twelve animals were not treated by decompressive craniectomy (control group). Four, 24, 48, 72 and 168 hours after MCAO all animals were examined with conventional T1- and T2-weighted SE-MRI. Shift of the midline structures and compression of the ventricles were scored. Changes in weight and neurological performance were measured daily. The infarction volume was calculated by triphenyltetrazolium chloride staining 168 hours after MCAO. While mortality in the untreated group was 33.3%, none of the animals treated by a decompressive craniectomy died (mortality 0%). Neurological behaviour, weight loss and infarction volume were significantly better in the animals treated by early decompressive craniectomy (p < 0.05). Four hours after MCAO all untreated animals showed a massive shift of the midline structures and a massive compression of the ventricles; only 7 of 12 animals treated early by craniectomy showed mild mass effects. Correlation of the histological brain damage with T2-weighted MRI 4 hours after MCAO was poor (r = 0.41); later than 24 hours there was a good correlation (r > 0.7). Our results suggest that decompressive craniectomy in malignant cerebral ischemia reduces mortality and significantly improves outcome. If performed early after vessel occlusion, it also significantly reduces infarction size. In the acute phase of hemispheric infarction conventional SE-MRI is not sensitive in estimation of infarction size. Later than 24 hours, conventinal SE-MRI proved to be useful in monitoring brain edema and infarction size in this rat model of malignant hemispheric stroke.

[Acute ischemic cerebral infarct: prospective serial observations by magnetic resonance imaging]. / Der akute ischämische Hirninfarkt: Eine prospektive, serielle Untersuchung mit der Magnetresonanztomographie.

AIM: Serial observations of acute ischaemic cerebral infarcts by MRI in order to define signal patterns, contrast uptake, oedema and secondary haemorrhage over a period of three months. METHODS: Prospective serial examinations of 34 patients with acute cerebral ischaemia who were examined during the first 48 hours, on days 3 or 4, 7, 14, 21, 28 and after three months by MRI (spin echo TR/TE 2200/100/20, 500/20, +/- Gd). RESULTS: T2 weighted spin echo sequences showed the highest sensitivity (88%) during the first 8 hours of cerebral ischaemia when compared with other spin echo sequences. Parenchymal contrast enhancement showed a distinct peak during the second and third weeks. The use of contrast did not improve diagnosis of an infarct during any stage. 87% of lesions showed haemorrhage at some stage. Vascular enhancement was observed in 25% of infarcts during the first 24 hours and was still present after three months in 20%. Parenchymal and vascular enhancement, and haemorrhage correlate with the size of the infarct. CONCLUSION: Focal cerebral ischaemia produces an abnormality of the blood-brain barrier, oedema and finally necrosis, depending on the severity and duration of the lesion. Haemorrhage in 87% was considerably more common than has been described previously. Vascular enhancement is not an early sign of an infarct, contrary to what has been described in the literature.

Basilar artery embolism. Clinical syndrome and neuroradiologic patterns in patients without permanent occlusion of the basilar artery.

The objective of this study was to clarify the clinical and radiologic features, risk factors, and prognosis of basilar embolism without permanent basilar artery occlusion. Forty-five patients (mean age, 59 years) with basilar artery embolism participated in the study. Patients with basilar artery occlusion were excluded. The Glasgow Coma Scale (GCS) score on admission was < 7 in five patients, 7 to 12 in 11 patients, and > 12 in 29 patients. Etiologic factors were cardiac arrhythmia (17 patients), vertebral artery occlusion (12 patients), cervical spine trauma (4 patients), embolism following angiography (2 patients), and surgery (1 patient). MRI was performed in 17 patients and CT in 39 patients. Radiologic examinations were initially normal in 14 patients and remained normal in three patients. Final infarct localization was the thalamus (36 patients), cerebellum (20 patients), posterior cerebral artery territory (21 patients), midbrain (12 patients), and pons (8 patients). Eight to 12 weeks after stroke 12 patients were without clinical signs (Glasgow Outcome Scale [GOS] 1), 15 patients had minor neurologic deficits (GOS 2), 10 were severely disabled (GOS 3), and eight patients had died (GOS 5). Outcome correlated with GCS on admission (p < 0.0001) and with the number of ischemic lesions (p = 0.0001). The typical syndrome is an acute loss of consciousness followed by multiple brainstem symptoms. Usually, clinical symptoms improve rapidly and, in some patients, completely. Compared with basilar occlusion, basilar embolism has a relatively low mortality and outcome is frequently excellent.

[Unilateral trigeminal nerve hypoplasia]. / Einseitige Trigeminushypoplasie.

BACKGROUND: Isolated unilateral corneal anaesthesia represents a very rare clinical entity. The underlying cause may be a hypoplasia of the trigeminal nerve. HISTORY AND CLINICAL FINDINGS: A 7 year old otherwise healthy boy presented with mixed conjunctival injection of the left eye, fluorescein-positive punctuate epithelial keratopathy of the cornea and a central corneal ulcer OS. History revealed intermittent, painless redness of the left eye since the age of 4. Trigeminal defects caused by trauma or infection could be ruled out. Tyndall's phenomena was positive. There was no corneal sensitivity on the left side and facial sensitivity was reduced in all branches of the trigeminal nerve. All other ophthalmologic examination results were normal. Magnetic resonance tomography showed a hypoplastic left trigeminal nerve. Mesenchymal syndromes could be ruled out by neuropediatric examination. THERAPY AND CLINICAL COURSE: Treatment with prednisolone and antibiotic ointment and eye patching were performed. The ulcer healed completely and artificial tear substitution was given for prophylaxis. Follow-up examinations after 4 and 6 years showed no signs of inflammation. Biomicroscopy showed only mild fluorescein-positive corneal epitheliopathy. CONCLUSIONS: In cases with painless intermittent keratoconjunctivitis, sometimes associated with corneal ulceration, in early childhood, one should consider acquired or congenital trigeminal anaesthesia. This condition requires life-long corneal ulcer prophylaxis and regular ophthalmologic exams.

[CT angiography in dissections of the internal carotid artery. Value of a new examination technique in comparison with DSA and Doppler ultrasound]. / CT-Angiographie bei Dissektionen der A. carotid interna. Wertigkeit einer neuen Untersuchungstechnik im Vergleich zur DSA und Dopplersonographie.

PURPOSE: To evaluate the role of CT angiography (CTA) in the diagnosis of dissection of the internal carotid artery (ICA). METHODS: In 21 patients who were clinically or sonographically suspected of having a dissection of the ICA, we performed CTA covering the extracranial course of the ICA. Our technique included spiral scanning (Picker PQ 2000), slice thickness 3 mm, index 1.5 mm, pitch factor 1.25, tube voltage 130 kV, amperage 125 mA, i.v. bolus injection of 100 ml nonionic contrast medium, injection rate 4 ml/s and scan delay 15 s. Spiral data were processed using a workstation (Picker Voxel Q) to calculate 3D "angiographic" reconstructions, maximal intensity projections and multiplanar reconstructions. In 20 of the 21 patients transfemoral angiography was performed, and in all patients cw-Doppler ultrasonography of the carotid arteries was performed. RESULTS: Sensitivity of CTA in acute extracranial dissection of the ICA was 100% (14/14). One patient had a pseudoaneurysm of the ICA, two patients had excessive kinking and one patient showed an atheromatous carotid ulcer. DSA could confirm this in all cases. One intracranial ICA dissection, not covered by the scan field, was missed by CTA. CTA source images demonstrated mural thickening and eccentric luminal narrowing in cases of dissection. 3D reconstructions showed tapering of the ICA. CONCLUSION: CTA is a reliable tool in the diagnosis of ICA dissection. Further studies comparing CTA, MRI and duplex ultrasound are necessary.