Dark-lumen magnetic resonance colonography.
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Clinical Trials as Topic↗
Biomedical subjects
Thomas Lauenstein
Publications and source records attributed to Thomas Lauenstein.
Dark-lumen magnetic resonance colonography in patients with suspected sigmoid diverticulitis: a feasibility study.
To assess dark-lumen magnetic resonance colonography (MRC) for the evaluation of patients with suspected sigmoid diverticulitis. Forty patients with suspected sigmoid diverticulitis underwent MRC within 72 h prior to conventional colonoscopy (CC). A three-dimensional T1-weighted volumetric interpolated breath-hold examination sequence was acquired after an aqueous enema and intravenous administration of gadolinium-based contrast agents. All MRC data were evaluated by two radiologists. Based on wall thickness and focal uptake of contrast material and pericolic reaction including mesenteric infiltration on T1-weighted sequence the sigmoid colon was assessed for the presence of diverticulitis. MRC classified 17 of the 40 patients as normal with regard to sigmoid diverticulitis. However, CC confirmed the presence of light inflammatory signs in four patients which were missed in MRC. MRC correctly identified wall thickness and contrast uptake of the sigmoid colon in the other 23 patients. In three of these patients false-positive findings were observed, and MRC classified the inflammation of the sigmoid colon as diverticulitis whereas CC and histopathology confirmed invasive carcinoma. MRC detected additionally relevant pathologies of the entire colon and could be performed in cases where CC was incomplete. MRC may be considered a promising alternative to CC for the detection of sigmoid diverticulitis.
Aged↗
Colonography by magnetic resonance imaging.
Dark-lumen magnetic resonance colonography has been shown to be an appropriate diagnostic tool for the detection of colorectal pathologies. This review describes the underlying techniques of dark-lumen magnetic resonance colonography concerning data acquisition, image interpretation and diagnostic accuracy for the detection of colorectal pathologies. In addition, techniques to improve patients' acceptance are discussed.
Barium Sulfate↗
Real-time high-resolution MRI for the assessment of gastric motility: pre- and postpharmacological stimuli.
PURPOSE: To determine the practicality of MRI using a new real-time sequence for the assessment of gastric motion, and quantify the effects of motility-modifying substances. MATERIALS AND METHODS: Six healthy volunteers ingested 400 mL of a high-calorie liquid nutrient. Two-dimensional real-time TrueFISP sequences were acquired for up to 30 minutes following the ingestion. The acquisition plane was chosen parallel to the axis of the gastric antrum. The examination was performed on three separate days with and without i.v. administration of 10 mg metoclopramide or 20 mg scopolamine. A motility index was calculated for each real-time data set. RESULTS: Delineation of the gastric lumen proved easy and robust. The intravenous application of motility-modifying agents resulted in significant changes in the motility index. The administration of metoclopramide resulted in an average increase of the index by a factor of 1.5, whereas the application of scopolamine led to a decrease of the index by a factor of 3.0. CONCLUSION: TrueFISP MRI performed well in depicting the gastric lumen and assessing gastric motility. Furthermore, we were able to evaluate and quantify the effect of motility-modifying agents. The noninvasive nature of MRI makes this imaging modality an attractive alternative to conventional invasive diagnostic tools for gastric motility disorders and monitoring of therapy.
Adult↗
Impact of diet on stool signal in dark lumen magnetic resonance colonography.
PURPOSE: To examine the magnetic resonance (MR) properties of different foods and their effect on the colonic stool signal to potentially support fecal tagging strategies for dark lumen MR colonography (MRC). MATERIALS AND METHODS: T1 relaxation times of 120 different foods (partially diluted with sufficient water) were determined by use of a multi-flip-angle two-dimensional gradient echo (GRE) sequence and correlated to the foods' signal in a three-dimensional GRE volumetric interpolated breath-hold examination (VIBE) sequence. Different dilutions of six foods were examined. VIBE stool signal was determined in six volunteers under two different conditions: after a three-day diet of short T1 food and of long T1 food, respectively. RESULTS: Most foods exhibit short to very short T1 relaxation times. T1 correlates well with the fat-saturated VIBE signal except for fatty products. Diluted food exhibits T1 times similar to water; concentrated food strongly varies according to their T1 values. No significant difference in stool signal could be found in the in vivo examination comparing the two diets. CONCLUSION: According to our results, a restricted diet strategy to reduce fecal signal for dark lumen MRC is unlikely to be successful. Moreover, the stool signal reduction found in the other fecal tagging studies can be explained at least to a great extent by the relative content of other material with long T1 relaxation times, such as water or oral barium.
Colon↗
MR colonography with fecal tagging: comparison between 2D turbo FLASH and 3D FLASH sequences.
The objective of this study was to compare inversion recovery turbo 2D fast low-angle shot (FLASH) and 3D FLASH sequences for fecal-tagged MR colonography studies. Fifteen consecutive patients with indications for colonoscopy underwent MR colonography with fecal tagging. An inversion recovery turbo-FLASH sequence was applied and compared in terms of artifacts presence, efficiency for masking residual stool, and colonic wall conspicuity with a fat-saturated 3D FLASH sequence. Both sequences were acquired following administration of paramagnetic contrast agent. Contrast-to-noise ratio and relative contrast between colonic wall and lumen were calculated and compared for both sequences. Turbo 2D FLASH provided fewer artifacts, higher efficiency for masking the residual stool, and colonic wall conspicuity equivalent to 3D FLASH. An inversion time of 10 ms provided homogeneously low signal intensity of the colonic lumen. Contrast to noise between colonic wall and lumen was significantly higher in the 3D FLASH images, whereas differences in relative contrast were not statistically significant. An optimized inversion-recovery 2D turbo-FLASH sequence provides better fecal tagging results and should be added to the 3D FLASH sequence when designing dark-lumen MR colonography examination protocols.
Barium Sulfate↗
Visualization of swallowing using real-time TrueFISP MR fluoroscopy.
The aim of this study was to evaluate the ability of different real-time true fast imaging with steady precession (TrueFISP) sequences regarding their ability to depict the swallowing process and delineate oropharyngeal pathologies in patients with dysphagia. Real-time TrueFISP visualization of swallowing was performed in 8 volunteers and 6 patients with dysphagia using a 1.5 T scanner (Magnetom Sonata, Siemens, Erlangen Germany) equipped with high-performance gradients (amplitude 40 mT/m). Image quality of four different real-time TrueFISP sequences (TR 2.2-3.0 ms, TE 1.1-1.5 ms, matrix 63 x 128-135 x 256, field of view 250 mm(2), acquisition time per image 139-405 ms) was evaluated. Water, yoghurt, and semolina pudding were assessed as oral contrast agents. Functional exploration of the oropharyngeal apparatus was best possible using the fastest real-time TrueFISP sequence (TR 2.2 ms, TE 1.1 ms, matrix 63 x 128). Increased acquisition time resulted in blurring of anatomical structures. As the image contrast of TrueFISP sequences depends on T2/T1 properties, all tested foodstuff were well suited as oral contrast agents, but image quality was best using semolina pudding. Real-time visualization of swallowing is possible using real-time TrueFISP sequences in conjunction with oral contrast agents. For the functional exploration of swallowing high temporal resolution is more crucial than spatial resolution.
Adult↗