Biomedical subjects

T C Lauenstein

Publications and source records attributed to T C Lauenstein.

10 recordsLinked to original sources

PubMed2006

Dark lumen MR colonography: can high spatial resolution VIBE imaging improve the detection of colorectal masses?

PURPOSE: To assess whether the detection of colorectal lesions can be improved using high spatial resolution VIBE imaging. MATERIALS AND METHODS: 48 patients underwent same-day dark lumen MR colonography (MRC) and conventional colonoscopy (CC) as the standard for the detection of colorectal masses. MRC was performed using contrast-enhanced standard and high spatial resolution T1-weighted 3D VIBE sequences. The findings and the image quality of the standard and high spatial resolution VIBE sequences were compared qualitatively and quantitatively. The findings of both sequences regarding colorectal lesions were compared to those of a subsequently performed colonoscopy. RESULTS: The high spatial resolution VIBE sequence significantly improved the quantitative image quality (CNR 54.0 vs. 36.8). However, high spatial resolution VIBE imaging did not detect more colorectal lesions than the standard VIBE sequence. In addition, none of the sequences employed was able to detect lesions with a diameter of less than 5 mm (CC 40 lesions). However, 13 colorectal lesions with a diameter of greater than 5 mm were detected by both sequences (CC 15). CONCLUSION: High spatial resolution VIBE imaging did not improve the detection of colorectal masses and MRC fails to detect colorectal lesions with a diameter of less than 5 mm.

Adult↗

PubMed2005

Magnetic resonance colonography for the detection of inflammatory diseases of the large bowel: quantifying the inflammatory activity.

INTRODUCTION: The purpose of this study was to assess the diagnostic accuracy of magnetic resonance colonography (MRC) for its ability to detect and quantify inflammatory bowel disease (IBD) affecting the colon. Endoscopically obtained histopathology specimens were used as the standard of reference. MATERIALS AND METHODS: Fifteen normal subjects and 23 patients with suspected IBD of the large bowel underwent MRC. Three dimensional T1 weighted data sets were collected following rectal administration of water prior to and 75 seconds after intravenous administration of paramagnetic contrast (gadolinium-BOPTA). The presence of inflammatory changes in patients was documented based on bowel wall contrast enhancement, bowel wall thickness, presence of perifocal lymph nodes, and loss of haustral folds. All four criteria were quantified relative to data obtained from normal subjects and summarised in a single score. This MRC based score was compared with histopathological data based on conventional endoscopic findings. RESULTS: MRC correctly identified 68 of 73 segments found to reveal IBD changes by histopathology. All severely inflamed segments were correctly identified as such and there were no false positive findings. Based on the proposed composite score, MRC detected and characterised clinically relevant IBD of the large bowel with sensitivity and specificity values of 87% and 100%, respectively, for all investigated colonic segments. CONCLUSION: MRC may be considered a promising alternative to endoscopic biopsy in monitoring IBD activity or assessing therapeutic effectiveness.

Adult↗

PubMed2004

Real time high resolution magnetic resonance imaging for the assessment of gastric motility disorders.

BACKGROUND: The aim of this study was to evaluate whether patients with increased or decreased gastric motility can be differentiated from healthy volunteers by means of real time magnetic resonance imaging (MRI). PATIENTS AND METHODS: Ten healthy volunteers, 10 patients with gastroparesis, and 10 patients with functional pylorospasm/peptic pyloric stenosis underwent real time MRI. All patients were examined on two separate days; once prior to therapy and once after adequate therapy. Antral motility was quantified by calculating the gastric motility index. RESULTS: Patients with gastroparesis showed a lower motility index compared with the reference volunteer group while the mean motility index of the patient group with pylorospasm was more than three times higher than that of the reference value of the volunteer group. However, the gastric motility index in the patient group with gastroparesis increased, and in the group with functional pylorospasm/peptic pyloric stenosis it decreased significantly after therapy. CONCLUSION: Real time MRI is a reliable tool for assessment of gastric motion. Furthermore, differences in gastric motility index in patients with increased or decreased gastric motility could be evaluated and quantified. Due to the non-invasive character of MRI, this imaging modality may be an attractive alternative to conventional invasive diagnostic tools for gastric motility disorders and therapeutic monitoring.

Adult↗

PubMed2003

[State of the art of MR colonoscopy].

MR colonoscopy is suitable for colorectal cancer screening. This imaging modality is non-invasive, has no harmful side effects and provides a high diagnostic accuracy. MR colonoscopy has been found to be highly sensitive and specific in detecting colorectal lesions > 10 mm in size. Since colonic polyps are difficult to differentiate from residual stool, colonic cleansing has been unavoidable but reduces patient acceptance. Cleansing of the bowel can be avoided if the signal of stool is rendered different from its surrounding. This can be achieved by adding an agent to the food that tags the feces (fecal tagging). This article describes current techniques of MR colonoscopy as well as first results with fecal tagging.

Aged↗

PubMed2003

Dark lumen magnetic resonance colonography: comparison with conventional colonoscopy for the detection of colorectal pathology.

BACKGROUND: The purpose of this study was to assess the feasibility and usefulness of a new magnetic resonance (MR) colonography technique for the detection of colorectal pathology in comparison with conventional colonoscopy as the standard of reference. PATIENTS AND METHODS: A total of 122 subjects with suspected colorectal disease underwent "dark lumen" MR colonography. A contrast enhanced T1w three dimensional VIBE sequence was collected after rectal administration of water. The presence of colorectal masses and inflammatory lesions were documented. Results were compared with those of a subsequently performed colonoscopy. RESULTS: MR colonography was found to be accurate regarding detection of clinically relevant colonic lesions exceeding 5 mm in size, with sensitivity and specificity values of 93%/100%. CONCLUSION: Dark lumen MR colonography can be considered as a promising alternative method for the detection of colorectal disease. In addition, it allows assessment of extraluminal organs.

Adolescent↗

PubMed2003

Virtual magnetic resonance colonography.

Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques.

Colorectal Neoplasms↗

PubMed2001

0.5 M Gd chelate (Magnevist) versus 1.0 M Gd chelate (Gadovist): dose-independent effect on image quality of pelvic three-dimensional MR-angiography.

To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto-iliac disease underwent a mono-station three-dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA, Erlangen, Germany) twice, once using Gadovist 1.0 and the other time using Magnevist as the contrast agent. All subjects received a fixed volume of Gadovist 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist 1.0-enhanced three-dimensional MRA data sets were characterized by significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values compared to 0.5 M Magnevist-enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist 1.0 exam led to better delineation of the arterial morphology, especially of small vessels.

Adult↗

PubMed2001

Magnetic resonance colonography for colorectal cancer screening.

Colorectal cancer screening has vast potential. Beyond considerations of cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further enhance patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. This article will describe the techniques underlying MR colonography and early clinical experience with fecal tagging techniques.

Colonography, Computed Tomographic↗

PubMed2001

Dark lumen MR-colonography: initial experience.

PURPOSE: The aim of this study was to assess a new strategy of MR colonography for the detection of colonic polyps/malignancy. The technique is based on a rectal enema with water in combination with the intravenous application of a paramagnetic contrast agent. METHODS: Twelve subjects were included in this study either due to suspected colorectal tumors or for screening purposes. For MR colonography the colon was filled with approximately 3000 ml of tap water while Gadobenate dimeglumine (0.2 mmol/kg) was injected intravenously. A T1w GRE sequence was acquired before and 75 sec after the contrast administration only in prone position. Three patient underwent the "bright lumen" MRC as well. All MR examinations were performed at least five days prior to conventional colonoscopy and the results of both modalities were compared. RESULTS: The colonic filling with water resulted in a homogeneously low signal throughout the colonic lumen in all twelve subjects. Intravenous injection of gadolinium caused avid enhancement of the colonic wall. Similarly lesions arising from the colonic wall enhanced avidly. Dark lumen MR colonography correctly identified five polyps in four patients. Bright lumen MRC showed in one patient false positive results. CONCLUSION: The new MR colonography concept based on a dark colonic lumen and a bright, contrast enhanced colonic wall turned out to be a promising alternative to the traditional MRC based on a bright lumen concept. The new technique suggests a higher accuracy in detecting polyps, a better evaluation of other parenchymal organs as well as a reduced time needed for data acquisition and analysis.

Adult↗

PubMedDate not supplied

Fecal tagging: MR colonography without colonic cleansing.

Colorectal cancer, mostly arising (>90%) from preexisting adenomatous polyps, continues to be the second leading cause of cancer death. Magnetic resonance colonography (MRC) permits accurate detection of colonic polyps with a diameter larger than 10 mm. Because residual colonic stool cannot be differentiated from polyps, MRC requires a clean colon. However, the rigors associated with colonic cleansing considerably reduce patient acceptance. The need for colonic cleansing could be eliminated, if stool were to acquire a signal intensity different from polyps and identical to the enema used to fill and distend the colon. In principle, there are two approaches to this concept of fecal tagging: dark polyps surrounded by bright stool and a bright enema, and bright polyps surrounded by dark stool and a dark enema. The first approach has been evaluated with some success. Gadolinium (Gd)-DOTA was administered as an oral contrast agent with meals preceding MRC based on the administration of a Gd-based enema. The high cost of Gd-based contrast has limited the clinical utility of this technique. In the second approach patients are provided with barium as an oral fecal tagging agent to render stool dark, and barium for the enema is used to distend the colon during MRC. The colonic wall and polyps arising from it can be made visible after intravenous administration of Gd-based extracellular contrast. This method provides sufficient contrast between the darkened colonic lumen and the brightly enhanced colonic wall to permit virtual endoscopic rendering. Preliminary results showed an exact correlation with findings of conventional endoscopy and surgery. Fecal tagging obviates bowel cleansing and therefore should enhance patient acceptance for MR colonoscopy. Barium as the tagging agent is promising because it is inexpensive, commercially available, and characterized by an excellent safety profile.

Barium Sulfate↗