PubMed Health⌕ Search

Biomedical subjects

D Kivelitz

Publications and source records attributed to D Kivelitz.

17 recordsLinked to original sources
PubMed2006

Cine magnetic resonance imaging of the small bowel: comparison of different oral contrast media.

PURPOSE: To evaluate several substances regarding small bowel distension and contrast on balanced steady-state free precession (bSSFP) cine magnetic resonance (MR) images. MATERIAL AND METHODS: Luminal contrast was evaluated in 24 volunteers after oral application of two different contrast agent groups leading to either bright lumen (pineapple, blueberry juice) or dark lumen (tap water, orange juice) on T1-weighted images. Bowel distension was evaluated in 30 patients ingesting either methylcellulose or mannitol solution for limiting intestinal absorption. Fifteen patients with duodeno-jejunal intubation served as the control. Quantitative evaluation included measurement of luminal signal intensities and diameters of four bowel segments, qualitative evaluation assessed luminal contrast and distension on a five-point scale. RESULTS: Quantitative and qualitative evaluation of the four contrast agents revealed no significant differences regarding luminal contrast on bSSFP images. Quantitative evaluation revealed significantly lower (P<0.05) small bowel distension for three out of four segments (qualitative evaluation: two out of four segments) for methylcellulose in comparison to the control. Mannitol was found to be equal to the control. CONCLUSION: Oral ingestion of tap water or orange juice in combination with mannitol is recommended for cine MR imaging of the small bowel regarding luminal contrast and small bowel distension on bSSFP sequences.

Administration, Oral↗
PubMed2003

[Left ventricular pseudoaneurysm after mitral valve replacement].

We report about a woman with a rare complication after mitral valve replacement 24 years ago. The patient had a massive hemorrhage some hours after operation. We performed invasive diagnostics because of an increasing pressure gradient across the prosthesis and revealed a left ventricular pseudoaneurysm. Before the planned reoperation the patient died suddenly. As the cause of death, we assumed a rupture of the pseudoaneurysm.

Adult↗
PubMed2003

[MR angiography of the coronary arteries: comparison of the blood pool contrast medium Gadomer and Gd-DTPA in pigs].

AIM: To investigate the signal-enhancing effects of the macromolecular contrast medium Gadomer in MR angiography of the coronary arteries compared to Gd-DTPA. MATERIAL AND METHODS: A total of 15 MRI examinations of the heart were performed in pigs at 1.5 T using a pulse-triggered, segmented 3D FLASH sequence with data acquisition during breathhold before and up to 30 min after contrast medium injection. Gadomer was investigated at two doses (0.05 and 0.1 mmol Gd/kg), Gd-DTPA at one (0.3 mmol Gd/kg) (n = 5 examinations per dose). Standard sequences without magnetization preparation were supplemented by sequences with magnetization saturation applied before data acquisition before and immediately after contrast medium injection. Analysis comprised quantitative determination of blood and myocardium signal to noise (S/N) and contrast to noise (C/N) and qualitative assessment of several parameters of image quality and coronary artery visualization. RESULTS: Gadomer leads to a significant C/N increase between blood and myocardium compared to the unenhanced examination and the increase is longer-lasting than that produced by Gd-DTPA (Gd-DTPA: only directly after injection; Gadomer: up to 5 min post injection at 0.05 mmol Gd/kg, up to 10 min at 0.1 mmol Gd/kg). The qualitative evaluation shows that visualization of the coronary arteries and branch vessels is significantly better with Gadomer at both doses than with Gd-DTPA. Magnetization saturation increases the C/N in combination with Gd-DTPA and at the higher dose of Gadomer with the latter producing a higher increase in C/N values. CONCLUSION: Gadomer is a suitable contrast medium for MR angiography of the coronary arteries with the dose of 0.1 mmol Gd/kg being superior to 0.05 mmol Gd/kg due to a longer imaging window.

Animals↗
PubMed2001

Coronary magnetic resonance angiography: experimental evaluation of the new rapid clearance blood pool contrast medium P792.

The signal-enhancing characteristics of a new monodisperse monogadolinated macromolecular MR contrast medium (P792) were evaluated for magnetic resonance angiography (MRA) of the coronary arteries. A total of 15 cardiac examinations were performed in pigs at 1.5 T using a 3D gradient-echo sequence. Images were acquired during breath-hold before and up to 35 min after IV injection of Gd-DTPA (0.3 mmol Gd/kg), Gd-BOPTA (0.2 mmol Gd/kg), and P792 (13 micromol Gd/kg). An increase in the signal-to-noise ratio (SNR) of 97% +/- 17%, 108% +/- 37%, and 109% +/- 31% in coronary arteries and of 82% +/- 19%, 82% +/- 24%, and 28% +/- 18% in myocardium, respectively, was measured during the first postcontrast acquisition. The blood-to-myocardium signal-difference-to-noise ratio (SDNR) was significantly higher for P792 than for the other Gd compounds (P <.05) for up to 15 min after injection. Qualitative assessment showed that visualization of the coronary arteries and their branches was significantly better for P792 compared to the low-molecular Gd compounds (P <.05). The blood pool contrast medium P792 is well suited for MRA of the coronary arteries.

Animals↗
PubMed2001

Patent ductus venosus: diagnosis by MR angiography.

We report a 15-year-old boy with patent ductus venosus in whom the diagnosis was made by MR angiography. A patent ductus venosus Arantii is a rare form of portosystemic shunt. Only a few cases have been reported in adults and children. The diagnosis is usually made by US and digital subtraction angiography. In our patient, the diagnosis was first made by MR angiography. This demonstrates the excellent diagnostic potential of the method in paediatric patients.

Adolescent↗
PubMed2001

Gadolinium-enhanced MR angiography of the breast: is breast cancer associated with ipsilateral higher vascularity?

The aim of this study was to assess a possible association between breast malignancy and ipsilateral higher vascularity on gadolinium-enhanced MR angiography. One hundred six patients were examined by dynamic gadolinium-enhanced 3D MR imaging. Magnetic resonance angiographic views were generated by image subtraction and maximum intensity projection. The study included 85 patients with unilateral malignant breast neoplasms and 21 with unilateral benign lesions. Three blinded readers independently reviewed the MR angiograms after masking the lesions and the corresponding contralateral sites. The readers were asked to determine whether vascularity was higher on the right side, higher on the left side, or equal on both sides. The results were analyzed by the Kappa statistic and Pearson's chi-square test. The blood vessels of the breasts were clearly seen in all cases. There was good agreement among the observers (kappa > 0.54) in assessing vascularity on both sides. Breasts harboring malignant neoplasms were found to have a higher vascularity than the contralateral breasts (p < 0.005). This sign of malignancy had a sensitivity of 76.5%, a specificity of 57%, and an accuracy of 72.6%. Blood vessels of the breast can be depicted by MR angiography. Unilateral malignant neoplasms are associated with a higher ipsilateral vascularity. In conjunction with other indications of malignancy on gadolinium-enhanced MR images, a higher ipsilateral vascularity may serve as an additional sign of malignancy.

Adult↗
PubMed2001

A post-processing protocol for three-dimensional visualization of the inner ear using the volume-rendering technique based on a standard magnetic resonance imaging protocol.

A superior diagnostic quality compared to other post-processing (PP) techniques for three-dimensional (3D) inner ear imaging has been attributed to volume rendering (VR). We defined and assessed a VR protocol for 3D visualization of the inner ear in a routine imaging setting. Following definition of a VR protocol by using lower threshold values, surface shading, perspective views and related parameters, standardized 3D views of the inner ear were generated and evaluated in 32 patients suffering from sensorineural or combined hearing loss. Comprehensive inner ear visualization was achieved in 28 patients by means of two 3D shaded-surface views. Incomplete data acquisition (1/32), motion and pulsation artefacts (2/32) and interposed fluid-retaining mastoid cells (1/32) were responsible for non-diagnostic image quality in 4/32 patients. In 5/32 patients modifications of the PP protocol involving the threshold value and depth-cueing parameters helped to establish diagnostic image quality. Mean post-processing time amounted to 5.8 min per site. 3D imaging with the VR technique is suitable for routine inner ear assessment if direct VR, predefined PP protocols and standardized labyrinthine views are used.

Artifacts↗
PubMed2001

Assessment of the arteriovenous cerebrovascular system by multi-slice CT. A single-bolus, monophasic protocol.

PURPOSE: We present a protocol for the non-invasive angiographic assessment of the arterial and venous cerebrovascular (CV) system by multi-slice CT. MATERIAL AND METHODS: Data acquisition was performed in a multi-slice CT scanner with a scan range from the carotid bifurcation to the vertex and manual scan start following i.v. administration of 120 ml iodinated contrast medium with a flow rate of 4 ml/s. This protocol was applied in 12 patients with symptoms of acute CV insuffiency. RESULTS: In all patients, comprehensive imaging of the arteriovenous CV system was achieved including the common carotid bifurcation, the third segment of the major cerebral arteries, the dural sinus and the internal cerebral veins. Various CV pathologies, such as a territorial artery occlusion, a thrombotic obstruction of the internal carotid artery, an intracranial arteriovenous malformation and a sinus vein thrombosis, were successfully evaluated. CONCLUSION: Comprehensive assessment of the arteriovenous CV system is possible by the use of a single-bolus, monophasic multi-slice scan technique.

Adult↗
PubMed2001

The active magnetic resonance imaging stent (AMRIS): initial experimental in vivo results with locally amplified MR angiography and flow measurements.

RATIONALE AND OBJECTIVES: Magnetic resonance (MR) is limited by artifacts in vessels after stenting. An active MR imaging stent (AMRIS) allows for artifact-free imaging with local improvement in signal-to-noise ratio (SNR). In a rabbit model, we evaluated the imaging properties by MR angiography (MRA) and flow measurements. METHODS: The AMRIS was placed in the abdominal aorta of five rabbits. At 1.5 T, MRA (three-dimensional fast low-angle shot) was performed before and after intravenous injection of an iron oxide-based, blood-pool contrast medium (dose, 50 micromol Fe/kg), and flow measurements were performed (electrocardiographically triggered phase-contrast cine gradient-echo sequence). Mean SNRs were calculated and flow volume curves were generated. RESULTS: The SNR was 6.0 +/- 0.6 (outside the stent) versus 12.3 +/- 1.1 (inside the stent, P < 0.05) for plain MRA, 21.2 +/- 0.6 versus 40.6 +/- 5.2 (P < 0.05) for contrast-enhanced MRA, and 5.4 +/- 0.4 versus 13.7 +/- 2.1 (P < 0.05) for the magnitude images of flow measurements. Flow volume curves within and distal to the stent were comparable. CONCLUSIONS: By using the AMRIS as a vascular stent, the stented vessel segment can be examined with enhanced signal intensity on MRI.

Animals↗
PubMed2001

Magnetic resonance imaging of stentless xenografts for reconstruction of right ventricular outflow tract.

The objective was to overcome allograft shortage during the Ross operation; stentless xenografts were carefully evaluated for hemodynamic behavior and valve deterioration during medium term follow-up. Between January 10, 1994 and January 4, 1996 nine adult patients (age 31-51 years) underwent aortic valve replacement with an autologous pulmonary valve and right ventricular outflow tract reconstruction with the Edwards Prima or Medtronic Freestyle xenograft. One patient was dead early and one late, both from noncardiac reasons. Forty-eight to 66 months follow-up was available for 7 patients and was performed with physical examination in the outpatient clinic, transthoracic echocardiography (TTE), and magnetic resonance imaging (MRI). Two patients received 29-mm valves and the remaining 27-mm valves. No reoperation became necessary during follow-up. Preoperative left ventricular ejection fraction ranged from 20% to 84%, median 61%, mean 59% +/- 18%. At latest follow-up left ventricular ejection fraction was 49% to 70%, median 57%, mean 58% +/- 8%. TTE showed no calcification of the xenograft wall or cusps. MRI revealed good autograft function with no evidence of stenosis in any patient. Four patients showed no and three trivial regurgitation. Right ventricular outflow tract-stenosis could not be seen in any patient. Calculated gradients of the xenograft valves ranged from 2 to 6 mm Hg, median 3 mm Hg (mean 3.1 +/- 2.4 mm Hg) and calculated EOA ranged from 2.0 to 4.0 cm(2), median 2.8 cm(2). MRI supported these findings and showed pliable xenograft cusps in all patients. Right ventricular function was well preserved in all patients. In adult patients right ventricular outflow tract reconstruction with stentless xenografts can be performed safely and intermediate-term results are encouraging. During medium-term (5-7 years) follow-up no calcification or deterioration of valve function occurred with excellent hemodynamic behavior.

Adult↗
PubMed2000

Multifocal nodular fatty infiltration of the liver mimicking metastatic disease on CT: imaging findings and diagnosis using MR imaging.

The aim of this study was to describe the MR appearance of multifocal nodular fatty infiltration of the liver (MNFIL) using T1-weighted in-phase (IP) and opposed-phase (OP) gradient-echo as well as T2-weighted turbo-spin-echo sequences with fat suppression (FSTSE) and without (HASTE). Magnetic resonance imaging examinations at 1.5 T using T1-weighted IP and OP-GRE with fast low angle shot (FLASH) technique, and T2-weighted FSTSE, T2-weighted HASTE of 137 patients undergoing evaluation for focal liver lesions were reviewed. Five patients were identified in whom CT indicated metastatic disease; however, no liver malignancy was finally proven. Diagnosis was confirmed by biopsy (n = 3), additional wedge resection (n = 1) or follow-up MRI 6-12 months later (n = 5). Regarding the identified five patients, the number of focal liver lesions was 2 (n = 2) and more than 20 (n = 3). The MR imaging characteristics were as follows: OP-image: markedly hypointense (n = 5); IP image: isointense (n = 2) or slightly hyperintense (n = 3); T2-weighted FSTSE-image: isointense (n = 5); T2-weighted HASTE image isointense (n = 1); slightly hyperintense (n = 4). On OP images all lesions were sharply demarcated and of almost spherical configuration (n = 5). Further evaluation by histology or follow-up MR imaging did not give evidence of malignancy in any case. Histology revealed fatty infiltration of the liver parenchyma in three patients. Magnetic resonance follow-up showed complete resolution in two patients and no change in three patients. Multifocal nodular fatty infiltration can simulate metastatic disease on both CT and MR imaging. The combination of in-phase (IP) and opposed-phase (OP) gradient-echo imaging can reliably differentiate MNFIL from metastatic disease.

Aged↗
PubMed1999

Ferric ammonium citrate as a positive bowel contrast agent for MR imaging of the upper abdomen. Safety and diagnostic efficacy.

PURPOSE: To evaluate the safety and diagnostic efficacy of two different doses of ferric ammonium citrate as a paramagnetic oral contrast agent for MR imaging of the upper abdomen. MATERIAL AND METHODS: Ninety-nine adult patients referred for MR imaging for a known or suspected upper abdominal pathology were included in this randomized multicenter double-blind clinical trial. Imaging was performed with spin-echo (T1- and T2-weighted) and gradient-echo (T1-weighted) techniques before and after administration of either 1200 mg or 2400 mg of ferric ammonium citrate dissolved in 600 ml of water. Safety analysis included monitoring of vital signs, assessment of adverse events, and laboratory testing. Efficacy with regard to organ distension, contrast distribution, bowel enhancement and delineation of adjacent structures was graded qualitatively. RESULTS: No serious adverse events were reported for either of the two concentrations. A total of 31 minor side effects were noted, of which significantly more occurred in the higher dose group (p<0.01). The diagnostic confidence in defining or excluding disease was graded as better after contrast administration for 48% of all images. Marked or moderate enhancement of the upper gastrointestinal tract was achieved at both doses in 69.5% of cases with no evident difference between the two doses. The higher dose tended to show better results in terms of the contrast assessment parameters. CONCLUSION: Ferric ammonium citrate is a safe and effective oral contrast agent for MR imaging of the upper abdomen at two different dose levels. The higher dose showed a tendency toward better imaging results while the lower dose caused significantly fewer side effects. Therefore the 1200 mg dose can be recommended in view of the risk-to-benefit ratio.

Abdomen↗
PubMed1999

Safety of implantable coronary stents during 1H-magnetic resonance imaging at 1.0 and 1.5 T.

The safety of most available implantable intracoronary stents during magnetic resonance imaging (MRI) has not been sufficiently tested. Minor, but possibly clinically significant, increases in temperature have not been excluded. We measured temperature changes of 14 different stents clinically in use or currently tested for release on the world market. Stents were examined in 1.0- and 1.5-T MR scanners with multiple sequences used in routine cardiac and thoracic MRI examinations ("clinical worst case") and after implantation of the stents into the coronary arteries of excised pig hearts (1.5-T scanner only). We used a highly sensitive infrared camera with a thermal resolution of 10 mK and did not see significant heating of any stent during the examinations. We conclude that MRI is safe in patients with the currently available intracoronary stents.

Animals↗
PubMed1992

Comparison between high-field-strength MR imaging and CT for screening of hepatic metastases: a receiver operating characteristic analysis.

The diagnostic performance of high-field-strength magnetic resonance (MR) imaging (1.5 T) for detection of liver metastases was compared with that of computed tomography (CT). All patients (n = 52) underwent preoperative screening for metastases by means of MR imaging with T1-weighted, proton-density-weighted, and T2-weighted pulse sequences and CT scanning with unenhanced, incremental dynamic bolus-enhanced, and delayed contrast medium-enhanced techniques. Diagnostic performance was evaluated by means of receiver operating characteristic analysis in which 800 images (400 with and 400 without lesions) and five readers (4,000 observations) were used; images were obtained from patients (n = 39) in whom the same anatomic levels were available for all MR imaging and CT studies. Direct comparison between the best MR imaging technique (T2-weighted spin-echo imaging [repetition time, 2,000 msec; echo time, 70 msec]) and the best CT technique (incremental dynamic bolus CT) showed a strong trend of superiority of T2-weighted MR imaging over incremental dynamic bolus CT. No highly statistically significant difference (P greater than or equal to .01), however, was found between these two techniques.

Esophageal Neoplasms↗
PubMed1991

Detection of hepatic masses in patients with carcinoma: comparative sensitivities of sonography, CT, and MR imaging.

To evaluate the sensitivity of sonography, CT, and MR imaging in the detection of hepatic masses in carcinoma patients, we conducted a prospective study of 75 consecutive patients with gastrointestinal tumors who were admitted for surgical resection of the primary tumor. Sonography was performed with convex transducers of 3.5 and 5.0 MHz. Three noninvasive CT techniques were used: unenhanced CT scans, the incremental bolus dynamic scanning technique, and delayed scanning 4-6 hr after bolus injection of 60 g of iodine. MR images (1.5 T) were acquired as presaturated T1- and T2-weighted spin-echo sequences and as breath-holding fast low-angle shot (FLASH) 60 degrees and FLASH 15 degrees sequences. As it is difficult to distinguish benign from malignant masses solely on the basis of morphologic criteria, the techniques for each imaging method were designed to detect and not to characterize hepatic lesions. Each examination was interpreted blindly, and the results were compared with surgical findings, intraoperative sonography, and biopsy of the liver as the gold standard. All focal hepatic masses verified at surgery, malignant or benign, were included in the analysis. Sixty-five (68%) of 95 focal hepatic masses were detected by CT, 60 lesions (63%) by MR, and 50 lesions (53%) by sonography. Although lesions 1-2 cm were shown almost equally well by CT and MR (74% and 77%, respectively), the detection rate of smaller lesions (less than 1.0 cm) decreased more drastically with MR (31%) than with CT (49%). Sonography had a sensitivity of only 20% with the smaller lesions. All imaging techniques had a sensitivity of 100% for focal hepatic masses larger than 2.0 cm. Our results show that CT has a higher overall sensitivity (68%) than MR and sonography for the detection of focal hepatic masses. When the results of the three procedures are combined, the overall sensitivity is 77%. This is unsatisfactorily low, as CT and MR have a size threshold of about 1.0 cm and are relatively unreliable for the detection of smaller lesions.

Adenocarcinoma↗