To our knowledge no comparative studies investigating patients' acceptance of different MR systems have been published. We therefore studied a number of subjective criteria to evaluate both patients' acceptance of and subjective conditions during magnetic resonance imaging (MRI) studies. MRI studies were performed using four separate systems. Two were conventional body MR systems operating at 1.0 or 1.5 Tesla, another was a 0.2 Tesla open whole-body MR system, and the last was a 0.2 Tesla MR system dedicated to the study of extremities. Forty patients for each MR system (total of 160 patients) participated in a standardized, written interview focusing on aspects of their subjective condition, including their perception and acceptance of different factors relevant to the study on respective MR systems. The patients' subjective condition and acceptance was predominantly positive for all MR systems. Differences between MR systems were noted with respect to noise, width of patient gantry, comfort of patient positioning and degree of well-being. Such differences, however, do not lend preference to the use of one particular type of MR system. Therefore, the choice of MR system should be based on the technical features required for the intended studies.

Laser-induced interstitial thermo-therapy (LITT) was introduced as a minimally invasive form of therapy for tumors in different anatomic regions. However, in the orofacial region, it has not been used so far for inoperable T4 carcinomas. Since vascular and neural structures are often close to the tumor or are even involved, online monitoring of LITT is necessary. The aim of our study was to establish a method of monitoring LITT with MRI (magnetic resonance imaging) in the orofacial region. Five patients with T4 carcinomas of the orofacial region underwent LITT under anesthesia. A 1.5 T whole-body imager with a circular polarized head coil was used. Before and after the intervention, the region of interest was studied using T1- and T2-weighted sequences in axial and coronal planes, with and without contrast enhancement (intravenous Gd-DTPA). Temperature distribution was monitored with a T1-weighted 2D-FLASH (fast low angle shot) sequence. The positioning of the optical fibers was monitored with MRI. Nd:YAG laser equipment was used for laser application. The necrosis was best seen on contrast-enhanced MRI. Immediately after LITT, the outcome could be determined by MRI. We proposed that MRI-guided LITT be used for neoplasms in the orofacial region at advanced stages.

Die Magnetresonanz-Urographie (MRU) stellt eine sichere, röntgenstrahlenfreie Bildgebungsmethode ohne bekannte schädi-gende Effekte dar. Sie erlaubt morphologische und funktionelle Aussagen über die ableitenden Harnwege aufgrund von zwei unterschiedlichen Abbildungsprinzipien. Stark T2-gewichtete Aufnahmen (RARE-, TurboSpin-Echo-und HASTE/single-shot FSE-Sequenzen) erzeugen einen starken Kontrast zwischen unbewegten oder sehr langsam flieûenden Körperflüssigkeiten (Urin, Zerebrospinalflüssigkeit) und soliden Geweben und schnell flieûenden Körperflüssigkeiten (Blut). Mit HASTE-Aufnahmen, die die Harnwege in unter einer Minute abbilden, kann auch die Morphologie der Nieren, der Ureteren und der Blase beurteilt werden. Damit kann bei Harnleiterobstruktionen sowohl die Obstruktionshöhe als auch die Obstruktionsursache festgestellt werden. Funktionelle Aussagen über die Nieren und ableitenden Harnwege erfordern hingegen entweder die Anwendung von Schleifendiuretika oder den Einsatz kontrastverstärkter, T1-gewichteter Aufnahmen. Das Kontrastmittel (Gadoliniumchelate) ist jodfrei und kann auch bei eingeschränkter Nierenfunktion oder bekannten allergischen Kontrastmittelreaktionen sowie bei Schilddrüsenüberfunktion eingesetzt werden. Aufgrund der noch hö-heren Kosten kann und wird die MR-Urographie nicht die konventionelle Infusionsurographie ersetzen. Bei ausgewählten Fragestellungen, bei Patienten mit absoluten oder relativen Kontraindikationen für die konventionelle Infusionsurographie sowie im Rahmen anderer Magnetresonanzuntersuchungen des Abdomens und Beckens bietet sich die MRU jedoch als wertvolle Alternativmethode an.

MRI allows rather precise recognition of intraprostatic alterations after LITT, including volume changes over a period of up to 1 year after therapy that can be predicted immediately after LITT. While laser energy deposition in the prostate can be monitored by MRI with T1-weighted FLASH sequences as a function of temperature alteration, it is not possible to determine the lesion margins immediately from the FLASH images. Online temperature development map generation will be necessary to influence on-going LITT procedures with MRI.

Although rare in a general population, gallstone ileus accounts for 25% of nonstrangulated small bowel obstructions in patients over the age of 65. The radiographic picture and ultrasound of small bowel obstruction and the presence of air in the biliary tree are suggestive for the diagnosis of a gallstone ileus. In our patient, the computed tomography and ultrasound findings confirmed the diagnosis and led to a prompt and directed surgical intervention. In patients with comorbid factors a two-step approach with enterolithotomy in a first and cholecystectomy in a second operation should be the therapeutic strategy of choice.