Search PubMed⌕ Search

Biomedical subjects

Thomas C Lauenstein

Publications and source records attributed to Thomas C Lauenstein.

At least 37 records · Page 2Linked to original sources
PubMed2004

Whole-body MR imaging: evaluation of patients for metastases.

PURPOSE: To compare the results of whole-body magnetic resonance (MR) imaging with staging based on computed tomographic (CT), dedicated MR imaging, and nuclear scintigraphic results as standard of reference. MATERIALS AND METHODS: Fifty-one patients with known malignant tumors were included in the study. Patients were placed on a rolling table platform capable of moving the patient rapidly through the isocenter of the magnet bore. The thorax and the abdomen were imaged by using fast breath-hold T2-weighted sequences in the transverse plane. After intravenous administration of a paramagnetic contrast agent, three-dimensional gradient-echo data sets were collected in five stations and covered the body from the skull to the knees. Location and size of cerebral, pulmonary, hepatic, and osseous metastases were documented by two experienced radiologists. Whole-body MR imaging findings were compared with results obtained at skeletal scintigraphy, CT, and dedicated MR imaging. RESULTS: The mean examination time for whole-body MR imaging was 14.5 minutes. All cerebral, pulmonary, and hepatic metastases greater than 6 mm in diameter could be identified with whole-body MR imaging. Small pulmonary metastases were missed with MR imaging, which did not change therapeutic strategies, but MR imaging depicted a single hepatic metastasis that was missed with CT. Skeletal scintigraphy depicted osseous metastases in 21 patients, whereas whole-body MR imaging revealed osseous metastases in 24 patients. The additional osseous metastases seen with MR imaging were confirmed at follow-up examinations but did not result in a change in therapy. Whole-body MR imaging performed on a per-patient basis revealed sensitivity and specificity values of 100%. CONCLUSION: Whole-body MR imaging for the evaluation of metastases compared well with the reference techniques for cerebral, pulmonary, and hepatic lesions. Whole-body MR imaging was more sensitive in the detection of hepatic and osseous metastases than were the reference techniques.

Adolescent↗
PubMed2004

Combined small and large bowel MR imaging in patients with Crohn's disease: a feasibility study.

MRI of the small bowel is a new method for the assessment of inflammatory bowel diseases. However, inflammatory bowel disease can affect both the small and large bowel. Therefore, our goal was to assess the feasibility of displaying the small bowel and colon simultaneously by MR imaging. Eighteen patients with inflammatory bowel disease were studied. For small bowel distension, patients ingested a solution containing mannitol and locust bean gum. Furthermore, the colon was rectally filled with water. MR examinations were performed on a 1.5-T system. Before and after intravenous gadolinium administration, a T1w data set was collected. All patients underwent conventional colonoscopy as a standard of reference. The oral ingestion and the rectal application of water allowed an assessment of the small bowel and colon in all patients. By means of MRI (endoscopy), 19 (13) inflamed bowel segments in the colon and terminal ileum were detected. Furthermore, eight additional inflammatory lesions in the jejunum and proximal ileum that had not been endoscopically accessible were found by MRI. The simultaneous display of the small and large bowel by MRI is feasible. Major advantages of the proposed MR concept are related to its non-invasive character as well as to the potential to visualize parts of the small bowel that cannot be reached by endoscopy.

Adult↗
PubMed2004

MR-based full-body preventative cardiovascular and tumor imaging: technique and preliminary experience.

Recent improvements in hardware and software, lack of side effects, as well as diagnostic accuracy make magnetic resonance imaging a natural candidate for preventative imaging. Thus, the purpose of the study was to evaluate the feasibility of a comprehensive 60-min MR-based screening examination in healthy volunteers and a limited number of patients with known target disease. In ten healthy volunteers (7 men, 3 women; mean age, 32.4 years) and five patients (4 men, 1 woman; mean age, 56.2 years) with proven target disease we evaluated the performance of a comprehensive MR screening strategy by combining well-established organ-based MR examination components encompassing the brain, the arterial system, the heart, the lungs, and the colon. All ten volunteers and five patients tolerated the comprehensive MR examination well. The mean in-room time was 63 min. In one volunteer, insufficient colonic cleansing on the part of the volunteer diminished the diagnostic reliability of MR colonography. All remaining components of the comprehensive MR examination were considered diagnostic in all volunteers and patients. In the five patients, the examination revealed the known pathologies [aneurysm of the anterior communicating artery ( n=1), renal artery stenosis ( n=1), myocardial infarct ( n=1), and colonic polyp ( n=2)]. The outlined MR screening strategy encompassing the brain, the arterial system, the heart, the lung, and the colon is feasible. Further studies have to show that MR-based screening programs are cost-effective in terms of the life-years saved.

Adult↗
PubMed2004

Dual-modality PET/CT scanning with negative oral contrast agent to avoid artifacts: introduction and evaluation.

The authors qualitatively and quantitatively assessed a solution containing 0.2% locust bean gum (LBG) and 2.5% mannitol (mannitol-LBG) dissolved in water to provide a negative oral contrast material in dual-modality positron emission tomography (PET)/computed tomography (CT) scanning. PET/CT was performed in 60 patients with cancer after oral administration of barium, water, or mannitol-LBG. Qualitative and quantitative analyses were conducted to determine bowel distention and a potential influence of the contrast agents on the PET data. Intestinal distention with mannitol-LBG proved superior to that with water or barium. Findings at both quantitative and qualitative analysis revealed apparently increased tracer uptake in the small bowel with barium in comparison to that with mannitol-LBG or water. Mannitol-LBG may, therefore, be used as a negative oral contrast agent at PET/CT scanning because it provides excellent bowel distention while avoiding contrast material-induced PET artifacts.

Administration, Oral↗
PubMed2004

MR colonography: how does air compare to water for colonic distention?

PURPOSE: To prove the feasibility of air-distended magnetic resonance colonography (MRC) and compare it with water-based distention. MATERIALS AND METHODS: In five volunteers, the colon was imaged twice: once after distending the colon with air and a second time after distending the colon with water. A total of 50 patients, who had been referred to colonoscopy for a suspected colorectal pathology were randomized into water-distention (N = 25) and air-distention (N = 25) groups. A contrast-enhanced T1-weighted three-dimensional volume interpolated breath-hold (VIBE) sequence was collected. Comparative analysis was based on qualitative ratings of image quality and bowel distention, as well as contrast-to-noise ratio (CNR) measurements for the colonic wall with respect to the colonic lumen. In addition, patient acceptance was evaluated. RESULTS: Inflammatory changes and colorectal masses were correctly identified on MRC in eight patients each. One 4-mm polyp identified at colonoscopy was missed on water-distended MRC. There were no false positive findings. No significant differences were found between air- and water-distention regarding discomfort levels and image quality. The presence of air in the colonic lumen was not associated with susceptibility artifacts. CNR of the contrast-enhanced colonic wall, as well as bowel distention, were superior on air-distended three-dimensional data sets. CONCLUSION: MRC can be performed using either water or air for colonic distention. Both techniques permit assessment of the colonic wall and identification of colorectal masses. While discomfort levels are similar for both agents, MRC with air provides higher CNR and better colonic distention.

Adult↗
PubMed2004

Dose optimization of mannitol solution for small bowel distension in MRI.

PURPOSE: To optimize the dose of a hydro solution containing 2.5% mannitol and 0.2% locust bean gum (LBG) for small bowel MRI in terms of bowel distension and patient acceptance. MATERIALS AND METHODS: A total of 10 healthy volunteers ingested a hydro solution containing 2.5% mannitol and 0.2% LBG. Four different volumes (1500, 1200, 1000, and 800 ml) were assessed on four different examination days. Small bowel distension was quantified on coronal two-dimensional TrueFISP images by measuring the diameter of eight bowel loops throughout the jejunum and the ileum. In addition, volunteer acceptance was evaluated for every single examination by using a questionnaire. RESULTS: Optimal distension was obtained with either, 1000, 1200, or 1500 ml, with no statistically significant differences in distension between these groups. Administration of 800 ml led to significantly less distension of the small bowel. Significantly less side effects were noted using either 800 or 1000 ml compared to using larger volumes. CONCLUSION: We recommend a dose of 1000 ml mannitol/LBG solution as an oral contrast agent for optimal bowel distension and minimal side effects.

Administration, Oral↗
PubMed2004

HASTE MRI versus chest radiography in the detection of pulmonary nodules: comparison with MDCT.

OBJECTIVE: The purpose of our study was to compare the diagnostic accuracy of an ultrafast ECG-triggered black blood-prepared HASTE sequence with chest radiography for the detection of pulmonary nodules. SUBJECTS AND METHODS. Sixty-four patients with various primary malignancies who had undergone radiography and MDCT of the chest also underwent ECG-triggered black blood-prepared HASTE MRI of the lung. MR images and radiographs were interpreted separately. The number, location, and size of detected lesions were recorded, and each hemithorax was classified as affected or not affected on the basis of a grade reflecting the conspicuity of nodular involvement. Sensitivity, specificity, and positive and negative predictive values for the detection of pulmonary nodules with diameters of 5 mm or larger were determined, using MDCT findings as the standard of reference. Lesions with diameters smaller than 5 mm were not evaluated. Additional lesion-by-lesion comparisons between MDCT and MRI findings were performed. RESULTS: MDCT confirmed pulmonary lesions in 32 patients, whereas HASTE MRI revealed lesions in 30 patients and chest radiography, in 19 patients. MDCT revealed 226 nodules in 32 patients, whereas MRI HASTE revealed 227 lesions in 30 patients. Conspicuity scale-based sensitivity and specificity for chest radiography were 55.8% and 92.4%, respectively, whereas HASTE MRI had a sensitivity of 93.0% and a specificity of 96.2%. Positive and negative predictive values for chest radiography were 80% and 79.3%, respectively, and for HASTE MRI, 93.0% and 96.2%, respectively. The sensitivity of HASTE MRI increased with lesion size, ranging from 94.9% for nodules between 5 and 10 mm in diameter to 100% for lesions exceeding 3 cm in diameter. CONCLUSION: ECG-triggered black blood-prepared HASTE MRI is reliable for detecting pulmonary nodules exceeding 5 mm and has proven significantly more accurate than conventional chest radiography. The technique appears useful as an adjunct to MRI of the heart, great vessels, or chest, potentially increasing the diagnostic yield of MRI examinations.

Electrocardiography↗
PubMed2003

Oral contrast agents for small bowel MRI: comparison of different additives to optimize bowel distension.

The purpose of this study was to compare two osmotic carbohydrate sugar alcohols (mannitol 2.5% and sorbitol 2.5%, 2.0%, and 1.5% watery solutions) in combination with 0.2% locust bean gum (LBG) for small bowel distension for MR imaging. Small bowel distension was quantified on coronal 2D TrueFISP images by measuring the diameters of 16 small bowel loops in each of 12 healthy subjects (age range 31-55 years). Additionally, the grade of small bowel distension was rated qualitatively. Patient acceptance concerning nausea, vomiting, flatulence, and diarrhea was noted for each solution, and all results were compared by a Wilcoxon test or t test, respectively. The ingestion of water combined with LBG and either 2.5% mannitol or 2.0% sorbitol showed the best distension of the small bowel. The lowest side effect rate was observed following ingestion of sorbitol in a concentration of 2.0 and 1.5%. Based on these data, we recommend a combination of LBG and 2% sorbitol use for optimal bowel distension and minimal side effects resulting in enhanced patient acceptance.

Administration, Oral↗
PubMed2003

Optimization of oral contrast agents for MR imaging of the small bowel.

Effect on small-bowel distention of additives to water as contrast agents for magnetic resonance (MR) imaging was assessed. Oral contrast agents included water and water in combination with mannitol, a bulk fiber laxative, locust bean gum, and a combination of mannitol and locust bean gum. Filling of the small bowel was quantified on coronal images obtained with two-dimensional true fast imaging with steady-state precession sequence; bowel diameters were measured. Ingestion of water with locust bean gum and mannitol provided the best distention of the small bowel. MR imaging of the small bowel with oral administration of water can be improved with addition of osmotic and nonosmotic substances that lead to decreased water resorption.

Administration, Oral↗
PubMed2003

Detection of atherosclerosis: systemic imaging for systemic disease with whole-body three-dimensional MR angiography--initial experience.

In 100 consecutive patients with peripheral vascular disease whole-body three-dimensional magnetic resonance (MR) angiography was performed by using the rolling table platform system with a 1.5-T MR unit and five three-dimensional MR angiographic data sets during 72 seconds (0.2 mol per kilogram of body weight of gadobenate dimeglumine). Apart from the proved peripheral vascular disease, additional clinically relevant disease was found in 33 segments in 25 patients as follows: renal arterial narrowing (n = 15), carotid arterial stenosis (n = 12), subclavian arterial stenosis (n = 2), and abdominal aortic aneurysms (n = 4). Confirmatory studies performed in 11 patients in this study revealed no false-positive or false-negative findings at examination.

Adult↗
PubMed2003

MRI of the liver: can True FISP replace HASTE?

PURPOSE: To determine the diagnostic accuracy of two fast breath-hold magnetic resonance (MR) imaging sequences, half-Fourier acquired single turbo spin-echo (HASTE) and true fast imaging with steady state precession (TrueFISP), for the detection and characterization of focal liver lesions MATERIALS AND METHODS: A total of 186 patients with suspected focal liver lesions were enrolled in this study. All patients underwent the same standardized study protocol including HASTE and TrueFISP. A consensus reading based on all available image data served as a standard of reference for classifying lesions into cysts, hemangiomas, focal nodular hyperplasia, or malignant/other lesions. All malignant lesions, as well as hepatic adenomas and abscesses, were histologically verified. Each separated by an eight-week interval, HASTE and TrueFISP images were retrospectively reviewed in random order for the detection and characterization of focal hepatic lesions. Finally, a receiver operating characteristic (ROC) analysis was calculated. RESULTS: HASTE images had an overall sensitivity of 0.86 and a specificity of 0.91, whereas TrueFISP showed an overall sensitivity and specificity of 0.79 and 0.83, respectively (p>0.1). CONCLUSION: Neither HASTE nor TrueFISP alone are sufficient for the detection and characterization of hepatic lesions.

Female↗
PubMed2003

Assessment of normal, inflammatory, and tumor-bearing lymph nodes with contrast-enhanced interstitial magnetic resonance lymphography: preliminary results in rabbits.

PURPOSE: To assess different gadolinium (Gd)-based contrast agents for interstitial magnetic resonance (MR) lymphography in normal, inflammatory, and tumor-bearing lymph nodes in rabbits. MATERIALS AND METHODS: Three paramagnetic contrast agents were assessed: a standard extracellular 0.5 M Gd-chelate, gadoterate meglumine (Gd-DOTA), and two macromolecular agents, P792 and P760 (all Guerbet, Aulnay-sous-Bois, France). A volume of 0.5 mL of each agent were injected subcutaneously into the dorsal footpads of six rabbits (three groups, 18 rabbits). Imaging was performed prior to as well as two weeks following induction of either reactive (complete Freund adjuvant) or tumorous (VX2 tumor) lymph nodes. T1-weighted three-dimensional gradient-echo and maximum intensity projection (MIP) images were obtained up to 120 minutes as well as 24 hours after administration of the different compounds. Signal-to-noise ratios (SNRs) of enhancing lymph nodes were calculated. The different compounds were compared regarding nodal enhancement over time, depiction of regional nodes, and lymphatic vessels. Furthermore, enhancement patterns were compared between normal, inflammatory, and metastasized nodes. RESULTS: Inguinal and iliac lymph nodes and lymph vessels revealed enhancement following interstitial injection of all evaluated compounds. For all agents, inflammatory lymph nodes revealed no significantly different SNRs compared to normal nodes (P > 0.2), whereas tumorous nodes showed signal voids and significantly lower SNRs (P < 0.05). Compared to P760 and P792, depiction of tumor-bearing nodes with Gd-DOTA was less reliable. CONCLUSION: Interstitial MR lymphography with P760 and P792 allows differentiation of tumor-bearing lymph nodes from reactive inflammatory and normal nodes based on a contrast uptake pattern assessed qualitatively as well as quantitatively.

Animals↗
PubMed2003

Intraindividual comparison of gadopentetate dimeglumine, gadobenate dimeglumine, and gadobutrol for pelvic 3D magnetic resonance angiography.

RATIONALE AND OBJECTIVES: To compare the effect on image quality of a 1.0 mol/L gadolinium chelate with that of two 0.5 mol/L gadolinium compounds. MATERIALS AND METHODS: Five healthy volunteers underwent a mono-station 3D MRA exam (Siemens SONATA, Erlangen, Germany) four times using four separate gadolinium preparations. All subjects first received a fixed volume of undiluted gadobutrol (1 mol/L), which corresponded to a dose between 0.1 and 0.15 mmol/kg body weight. This gadobutrol dosage was then diluted with saline into twice the volume and administered as a bolus at twice the injection rate. For Gd-DTPA and Gd BOPTA, because these contrast agents are 0.5 mol/L preparations, the volume and flow rate were doubled to match diluted gadobutrol volume and concentration. Quantitative and qualitative analysis of the angiographic data sets was performed on nine arterial segments. RESULTS: Image quality was rated diagnostic for all image data sets without statistically significant differences between any of the compounds (P > 0.3). Quantitative measurements of Gd BOPTA (SNR: 81.15; CNR: 68.91) and both standard and diluted forms of gadobutrol (SNR: 84.33; CNR: 71.62; SNR(diluted): 79,23; CNR(diluted): 66.26) yielded significantly higher results (P < 0.02) in comparison with Gd-DTPA (SNR: 49.55; CNR: 38.24). The difference between either form of gadobutrol and Gd BOPTA was not shown to be statistically significant (P > 0.3), whereas both the SNR and CNR of standard gadobutrol were significantly higher than diluted gadobutrol. CONCLUSION: Gadobutrol- and Gd BOPTA-MRA exams lead to improved delineation of the pelvic arterial morphology compared with MRA exams performed with Gd-DTPA.

Adult↗
PubMed2003

Time-resolved three-dimensional MR imaging of gastric emptying modified by IV administration of erythromycin.

OBJECTIVE: The aim of our study was to assess the effect of IV erythromycin on gastric emptying and subsequent small-bowel filling using three-dimensional (3D) MR imaging in both healthy subjects and patients with functional dyspepsia. SUBJECTS AND METHODS: Six healthy volunteers and six patients with symptoms of functional dyspepsia ingested 10 mL of gadopentetate dimeglumine mixed into 500 mL of a liquid nutrient. On two separate days, gastric emptying was determined using 3D volume measurements that were obtained every 5 min for as long as 25 min on 3D T1-weighted gradient-echo MR imaging with and without the use of IV erythromycin. Gastric volumes and filling of the small bowel were quantified on the 3D data sets using semiautomatic software. RESULTS: Delineation of the bright gastric lumen proved easy. After 25 min, a significant decrease in gastric volumes could be seen in examinations performed with and without erythromycin. In healthy volunteers, gastric volumes decreased significantly more after the administration of erythromycin. In three patients with functional dyspepsia, MR imaging revealed reduced rates of gastric emptying. The administration of erythromycin resulted in a significantly faster rate of gastric emptying in two of those three patients. CONCLUSION: Three-dimensional MR imaging is a feasible method of assessing gastric volumes and diagnosing delayed gastric emptying. In patients with reduced rates of gastric emptying, 3D MR imaging may be an appropriate tool with which to monitor therapeutic approaches, such as the use of prokinetic agents like erythromycin.

Adult↗
PubMed2003

Comprehensive time-resolved MRI of peripheral vascular malformations.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of MRI and MR angiography for the assessment of peripheral vascular malformations compared with the usefulness of conventional duplex sonography, venography, and arteriography. SUBJECTS AND METHODS. Nineteen patients (age range, 8-64 years; 11 males and eight females) with clinically diagnosed or suspected angiodyplastic abnormalities of the extremities were examined on a 1.5-T whole-body MR scanner. Using parameters based on a fast localizer sequence, we acquired transverse or coronal T1-, T2-, short tau inversion recovery (STIR), and contrast-enhanced T1-weighted images. Dynamic contrast-enhanced three-dimensional (3D) gradient-echo MRIs were acquired to determine the extent and type of the arteriovenous malformation for each patient. MR data sets were evaluated for lesion depiction, determination of the extent of the malformation, involvement of neighboring structures, vascular detail, and treatment planning. Results were compared with findings from duplex sonography, venography, and intraarterial digital subtraction angiography. RESULTS: All MRIs were of diagnostic quality and revealed 12 venous vascular malformations, four arteriovenous malformations, and three hemangiomas. The STIR sequence was helpful for determining the extent of the vascular malformation, which was often underestimated using contrast-enhanced 3D MR angiography alone, whereas dynamic contrast-enhanced 3D MR angiography was required for classifying the type of the lesion. MR angiography was inferior to conventional angiography for revealing vascular detail and for planning intervention. CONCLUSION: MRI and MR angiography appear to be valuable for the assessment of vascular malformations of the extremities. The protocol for imaging such malformations should combine dynamic contrast-enhanced 3D gradient-echo MRI with STIR sequences. However, digital subtraction angiography and venography are still required for definitive treatment decisions.

Adolescent↗
PubMed2002

Whole-body MRI using a rolling table platform for the detection of bone metastases.

The aim of this study was to compare the results of whole-body MRI using a recently developed rolling table platform with findings of nuclear scintigraphy in patients with bone metastases. Twenty-six patients with known or suspected bone metastases who had undergone radionuclide scintigraphy were examined by MRI. Patients were placed on a rolling table platform with integrated phased-array surface coils [BodySURF (system for unlimited field of view)] capable of pulling the patient through the isocenter of the magnet. Using a five-station approach three different image sets (T1-weighted gradient recalled echo, half-Fourier acquired single-shot turbo spin echo, and short tau inversion recovery) were collected in the coronal plane. In addition, the spine was imaged in the sagittal plane. The MRI findings were compared with the results obtained by scintigraphy. The whole-body MR examination lasting merely 40 min was feasible in all 26 patients. The MRI revealed excellent correlation with scintigraphy regarding metastatic lesions. A total of 60 regions with metastatic lesions were identified on bone scintigraphy. Fifty-three regions were detected on identical locations by MRI. The regions missed by MRI were located mainly in ribs and skull. The MRI could identify additional bone metastases in spine, pelvis, and femur. The MRI screening for bone metastases correlated well with bone scintigraphy. Use of the rolling table platform permits rapid imaging based on three different contrast mechanisms of the entire skeletal system.

Adult↗
PubMed2002

Magnetic resonance colonography with fecal tagging: an innovative approach without bowel cleansing.

To date, virtual colonography mandates bowel cleansing in a manner similar to colonoscopy. Because more than half of patients undergoing bowel preparation complain about negative side effects, patient acceptance is negatively impacted. To assure high patient acceptance of MR colonography, bowel cleansing needs to be eliminated. This can be accomplished by fecal tagging, a concept based on altering the signal intensity of stool by adding contrast-modifying substances to regular meals. This article describes different fecal tagging approaches and points out both advantages and limitations of these strategies.

Barium Sulfate↗