Funktionelle MRT des Hörzentrums

Examination of the sense of hearing is a technically difficult undertaking especially with functional magnetic resonance imaging because the machine causes a high noise level during the measurement. This article describes the technical conditions which, nevertheless, allow the auditory capabilities to be tested. Furthermore, every switch point of the auditory pathway and the cortical areas involved, which are technically accessible in an investigation of the sense of hearing are pictorially described.     

Funktionelle MRT der Niere zur Erfassung strahleninduzierter Nierensch?digungen

The diagnosis of radiation-induced (especially chronic) renal alterations/damage is difficult and currently relies primarily on clinical evaluation. The importance of renal diagnostic evaluation will increase continuously due to the increasing number of long-term survivors after radiotherapy. This article evaluates the potentia diagnostic contribution of magnetic resonance (MR) imaging with a focus on functional MRI. The following functional MRI approaches are briefly presented and evaluated: blood oxygenation level-dependent imaging (BOLD), diffusion-weighted imaging (DWI) or diffusion tensor imaging (DTI), MR perfusion measurements and (23)Na imaging. In summary, only DWI and contrast-enhanced MR perfusion currently seem to be suitable approaches for a broader, clinical implementation. However, up to now valid data from larger patient studies are lacking for both techniques in regard to radiation-induced renal alterations. The BOLD and (23)Na imaging procedures have a huge potential but are currently neither sufficiently evaluated with regard to radiation-induced renal alterations nor technically simple and reliable for implementation into the clinical routine.     

Klinische MRT bei 3 Tesla: Aktueller Stand

Zusammenfassung Während die klinische MRT zumeist bei Feldstärken von bis zu 1,5 Tesla (T) durchgeführt wird, sind seit jüngster Zeit zugelassene klinische 3-T-Ganzkörper-MR-Systeme verfügbar. Deren Verbreitung wächst schneller als erwartet. Während sich die Aufstellungsbedürfnisse und Handhabung dieser Systeme nicht mehr wesentlich von denen mit kleineren Feldstärken unterscheidet, bestehen jedoch Unterschiede im praktischen Einsatz. Für die Bildgebung bei 3 T lässt sich das erhöhte Signal-zu-Rausch-Verhältnis (SNR) sowohl zu verbesserter räumlicher Auflösung oder schnellerer Bildaufnahme nutzen. Nachteilig führt dies zu einer Erhöhung der Empfindlichkeit auf Feldinhomogenitäten und veränderten Relaxationszeiten, die zu Kontraständerungen führen. Für die MR-Spektroskopie liegt der Vorteil in der Erhöhung des SNR und der spektralen Auflösung. Der Anstieg der pro Hochfrequenzanregung deponierten Energie macht darüber hinaus die Anwendung spezieller Strategien zur Reduktion der spezifischen Absorptionsrate (SAR) notwendig. Dieser Artikel gibt einen Überblick über den aktuellen Stand der MTR bei 3 T.     

MRT des Ösophagus

Esophageal disease is common. Fluoroscopy with or without fast cine-sequences is able to depict swallowing dynamics precisely and therefore is used in cases with swallowing disturbance, achalasia or diverticula etc. It is performed in addition to primary endoscopy. There is no evidence based indication for MRI in these settings as it is not to rule out post-surgical fistula and incompetence. Endoscopy and endosonography are gold standard for the depiction as well as staging of esophageal tumors hence differentiation of the esophageal wall layers and detection of suspicious lymph nodes is possible. And from both, biopsies may be taken. New techniques as OCT (optical coherence tomography) can demonstrate in situ carcinoma and therefore helps to decide for limited treatments as mucosectomy. For today multimodular treatment strategies in esophageal carcinoma the T-stage will lead to the treatment decision whereas the nodal-stage will give information about the prognosis. As a matter of fact endoscopy is unable to pass a stenosis esophageal tumor in up to 50% of the cases and will therefore not be able to give precise information on both T- and N-stage resulting in a good indication for MRI. Fetal MRI of the chest is a new topic in which MRI seems to be superior to ultrasonography.     

Bestimmung links- und rechtsventrikulärer Volumenejektionsfraktionen (VEF) mittels MRT bei 1,0 T

PURPOSE: To evaluate method- and user effects as well as the required time in the determination of left- and right ventricular ejection fractions in comparing manual and semiautomatic border detection of the endocardium. METHODS: In 22 patients with varying cardiac diseases endocardial borders were detected either manually or semi-automatically (seeded ROI) and subsequently the right and left ventricular volume ejection fractions were computer-calculated. Two investigators defined the endocardial borders for both ventricles using both methods. For statistical analysis two-factorial analyses of variance were performed for the four variables: VEF right ventricle, VEF left ventricle, required time right ventricle, required time left ventricle (SAS, Anova). RESULTS: There was no user or method effect detectable for both ventricles. The required time for both ventricles also did not reveal a user effect, but there was a dramatic method effect concerning a reduction of the required time for analysis for both ventricles > 50%. CONCLUSIONS: The semiautomatic mode for detecting the endocardial borders in determining right and left ventricular ejection fractions did not demonstrate results differing from the results of the manual method, but is significantly superior concerning the time required for analysing ejection fractions of both ventricles with a reduction of over 50%. This might significantly reduce the expenditure for personnel.     

MRT des Sprunggelenks Vergleich eines Ganzkörper-Mittelfeldgeräts (1,0 T) mit einem dedizierten Niederfeldgerät (0,2 T)

PURPOSE: Comparison of ankle joint injuries with different MR systems and at different field strengths. METHOD: Ten patients with acute ankle injuries were examined using mid-field (1.0 T) and dedicated low-field (0.2 T) MR units. Findings of ligamentous injury, sinus tarsi involvement, bone injury, and tendon injury were correlated. RESULTS: There was no significant difference between mid- and low-field MR imaging for ligamentous injuries (chi 2 = 0.0395), sinus tarsi changes bone injuries (chi 2 = 0.0507; critical value = 5,991). CONCLUSION: This study showed good agreement in pathological findings in ankle injury on mid-field and low-field MR imaging.     

环形表面线圈MRT定量的可行性研究

通过实验研究探讨３ｉｎ表面线圈磁化传递率定量的可行性。方法 应用临床ＭＲ机及其所属３ｉｎ环形表面线圈，对５只大白鼠和胶质溶液模型分别进行扫描，并测量不同浓度的胶质模型和大白鼠桥脑及额叶的ＭＴＲ值，分析其性。结果随着远离线圈表面距离的增加，虽然图像的信号逐渐减低，但是ＭＲＴ值不发生变化。     

CT und MRT der Hüftprothese

Metal-induced artifacts impair image quality of computed tomography (CT) and magnetic resonance imaging (MRI) in patients with hip prostheses. Due to new developments in metal artifact reduction both methods can now be used for evaluation of a painful hip prosthesis. Iterative reconstruction algorithms and dual-energy scans are among the newer CT techniques for artifact reduction, while slice-encoding for metal artifact correction (SEMAC) and multi-acquisition variable-resonance image combination (MAVRIC) have introduced substantial improvements for MRI. Loosening of the hip prosthesis, osteolysis from small wear particles and pseudotumors in metal-on-metal prostheses are specific pathologies in patients with total hip arthroplasty. Other causes of painful hip prostheses are infections, fractures, tendinopathies, tendon ruptures, muscle and nerve alterations and heterotopic ossifications.     

Erworbene ZNS-Läsionen im fetalen MRT

Acquired central nervous system (CNS) lesions are often subtle; therefore, the prenatal diagnosis of these lesions is extremely important. The fetal ultrasound examination and magnetic resonance imaging (MRI) are two important imaging methods that give an insight into these types lesions. The method of choice during pregnancy is still fetal ultrasound; however, fetal MRI is important when there are certain pathologies, e.g. periventricular leukomalacia (PVL) or malformations of the vein of Galen. In this manner clinicians can plan further therapy after childbirth in advance (e.g. cerebral angiography or embolization).     

Funktionelle Störungen des unteren Harntrakts im Kindesalter

Functional disorders of the lower urinary tract as well as vesicoureteral reflux involved in the disease complex of urinary tract infection/permanent renal parenchymal damage can be considered predisposing or risk factors. Two main forms can be distinguished, i.e., unstable bladder and dysfunctional voiding, while transitional forms between the two exist. Functional disorders of the lower urinary tract obstruct spontaneous resolution of vesicoureteral reflux. They are found in about 50% of cases in all children with urinary tract infection and are associated with an increased risk of developing renal parenchymal scars. They are observed during the newborn period up to school age. In the first few months of life, particularly boys with bilateral high-grade reflux and congenital renal parenchymal damage are affected. At later ages girls are also affected, but in this age group bladder instability predominates. Incontinence as the leading clinical symptom appears in approximately 70% of all cases and is closely correlated with chronic constipation. Imaging procedures in addition to urodynamic methods are of decisive importance for diagnosis and treatment, but noninvasive approaches such as sonography should be given preference.     

Ultraschallgestützte Bildfusion mittels CT und MRT

Abdominal ultrasound is often the first-line imaging modality for assessing focal liver lesions. Due to various new ultrasound techniques, such as image fusion, global positioning system (GPS) tracking and needle tracking guided biopsy, abdominal ultrasound now has great potential regarding detection, characterization and treatment of focal liver lesions. Furthermore, these new techniques will help to improve the clinical management of patients before and during interventional procedures. This article presents the principle and clinical impact of recently developed techniques in the field of ultrasound, e.g. image fusion, GPS tracking and needle tracking guided biopsy and discusses the results based on a feasibility study on 20?patients with focal hepatic lesions.