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P Reimer

Publications and source records attributed to P Reimer.

At least 55 records · Page 3Linked to original sources
PubMed1999

Polypoid tumors of the major duodenal papilla: preoperative staging with intraductal US, EUS, and CT--a prospective, histopathologically controlled study.

BACKGROUND: An adenoma-carcinoma sequence also applies to adenomas of the major duodenal papilla. Therefore accurate preoperative diagnosis and tumor staging are essential to select the appropriate patients for adequate treatment. In a prospective, histopathologically controlled study of tumors of the main duodenal papilla, the preoperative diagnostic value of ultrasound (US) catheter probes applied during endoscopic retrograde cholangiopancreatography (ERCP) was investigated. METHODS: Intraductal US was compared with conventional endoscopic ultrasonography (EUS) and computed tomography (CT). In 27 consecutive patients with benign polypoid tumors of the major duodenal papilla (n = 12) and carcinomas of the papilla (n = 15), respectively, the value of these imaging procedures in determining tumor visualization, tumor diagnosis and tumor staging according to the TNM classification was assessed. Every patient underwent surgical resection; histopathologic evaluation of resected specimens served as the reference standard. RESULTS: Intraductal US was significantly superior to EUS and CT in terms of tumor visualization (100% vs 59.3% vs 29.6%, respectively). Sensitivity and specificity rates for intraductal US and EUS were 100% versus 62.5% and 75% versus 50%, respectively. Overall accuracy rate in tumor diagnosis for intraductal US (88.9%; 24 of 27) was significantly (p = 0.05) superior to EUS (56.3%; 9 of 16). The latter did not depict 4 adenomas and 7 carcinomas. Neither intraductal US nor EUS is suitable for detection of distant metastases. CONCLUSION: Intraductal US appears to be the most effective imaging method in visualizing, diagnosing and staging tumors of the major duodenal papilla. Combining ERCP with catheter probe sonography offers a new diagnostic modality that has some potential advantages for local staging of small tumors of the main duodenal papilla. Consequently, minimally invasive techniques for resection of seemingly benign tumors of the papilla or, even more so, of small carcinomas should preferably be based on intraductal US.

Adenocarcinoma↗
PubMed1999

[Can the function of the transjugular intrahepatic portosystemic shunt be evaluated noninvasively by Doppler sonography?].

Transjugular intrahepatic portosystemic shunt (TIPS) is an effective treatment of complications due to portal hypertension. Possible shunt stenosis or shunt occlusion make periodical assessment of stent function necessary. Direct portal venography is the gold standard in morphologic and functional surveillance of TIPS. Controversially discussed is whether Doppler ultrasonography is effective in hemodynamical evaluation of TIPS and sufficient in prediction of shunt dysfunction. In 39 patients, 147 Doppler ultrasonographical examinations were performed and correlated with the results obtained by direct portal venography in TIPS follow-up, 43 of 47 hemodynamically relevant stenoses, including six shunt occlusions, were being diagnosed correctly by Doppler ultrasonography, by assessing maximal flow velocity in portal vein proximal to the TIPS (sensitivity 91.5%; specificity 97%). If Doppler ultrasonographical measurement of maximal flow velocity was performed within the proximal stent itself, sensitivity was only 70.4% and specificity 27%. In conclusion, assessment of portal maximal flow velocity more accurately represents hemodynamical TIPS function than Doppler ultrasonographical measurement within the proximal stent tract itself. Since, according to data presented. Doppler ultrasonography appears to be able to detect hemodynamically significant TIPS stenoses, it might reduce the number of invasive angiographies and thus contribute to more cost-effective follow-up of TIPS patients.

Adolescent↗
PubMed1998

Intracranial vascular stenosis and occlusion: comparison of 3D time-of-flight and 3D phase-contrast MR angiography.

We compared the value of 3D time-of-flight (TOF) and phase-contrast (PC) MR angiography (MRA) for detection and grading of intracranial vascular steno-occlusive disease. Unenhanced 3D-TOF MRA and 3D-PC MRA (30-60 cm/s velocity encoding) were performed at the level of the circle of Willis in 18 patients, mean age 56 +/- 10 years. Postprocessed images using a maximum-intensity projection reconstruction with multiple targetted projections were analysed. A total of 126 vessels was assessed by PC MRA and 143 by TOF MRA, with digital subtraction angiography (DSA) in 15 patients and/or transcranial Doppler sonography (TCD) in 18 as a standard. Two blinded readers reviewed the MRA, DSA and TCD examinations retrospectively. On DSA and/or TCD the two observers found 32 and 28 steno-occlusive lesions. 3D-TOF MRA was more sensitive than 3D-PC MRA (87% and 86% vs. 65% and 60%) and had a higher negative predictive value (96% vs. 89%). Correct grading of stenoses was achieved in 78 % by 3D-TOF and 65% by 3D-PC MRA.

Adult↗
PubMed1998

Study of susceptibility-induced artefacts in GRASE with different echo train length.

The aim of this study was to evaluate the sensitivity of gradient-and-spin-echo (GRASE) sequences to susceptibility effects. GRASE sequences with 21 and 33 echoes per echo train were compared with a T2-weighted FSE sequence with an echo train length of 5 by means of MRI in phantoms, volunteers (n = 10), and patients (n = 19) with old hemorrhagic brain lesions. All experiments were performed on a 1.0-T clinical MR system (Impact Expert, Siemens AG, Erlangen, Germany) with constant imaging parameters. Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations, of brain areas with physiological iron deposition (red nucleus, substantia nigra), and of areas of old brain hemorrhage were calculated for FSE and GRASE pulse sequences. Areas of old brain hemorrhage were also qualitatively analyzed for the degree of visible susceptibility effects by blinded reading. The CNR of iron oxide tubes and iron-containing brain areas decreased with increasing echo trains of GRASE sequences. The CNR of GRASE sequences decreased when compared with CNR of their FSE counterparts (GRASE 21 echo trains 23.8 +/- 0.8, FSE 5 echo trains 26.7 +/- 0.9; p </= 0.01). Qualitative analysis confirmed these measurements. FSE with an ETL of 5 demonstrated significantly stronger susceptibility effects than their GRASE counterpart with an ETL of 21. The results demonstrate that GRASE sequences do not necessarily compensate for the reduced sensitivity of FSE to susceptibility effects. The complex signal behavior of GRASE makes conventional SE, gradient echo, or FSE sequences containing shorter echo trains preferable when patients with intracranial hemorrhage are clinically evaluated.

Adult↗
PubMed1998

Non-invasive vascular imaging of peripheral vessels.

The purpose of this review is to describe recent advances in non-invasive vascular imaging techniques and to discuss their current clinical applications for imaging of peripheral vessels. Principles for applying ultrasound, CT angiography (CTA), and magnetic resonance angiography (MRA) for non-invasive imaging of peripheral arteries and veins are presented. Clinical applications are reviewed for different vascular diseases, therapy planning, and follow-up studies. Conventional Doppler and color duplex sonography are the most cost-effective procedures to detect or rule out peripheral arterial occlusive disease (PAOD) and to provide specific recommendations for therapy. In the near future, contrast-enhanced MRA (CE MRA) with additional axial two-dimensional time-of-flight studies to search for non-anatomic runoff will replace diagnostic intra-arterial digital subtraction angiography (DSA) for planning of reconstructive surgery with acquisition slabs displaying projections similar to intra-arterial DSA. Color duplex sonography should also be the first non-invasive technique applied for the detection of peripheral aneurysms. Preoperative or preinterventional therapy planning of aneurysms may be performed by CTA or CE MRA. Compression ultrasound is the imaging procedure of choice in deep venous thrombosis (DVT). In the preoperative assessment of venous incompetence, color duplex sonography is the imaging technique which is sufficient in most cases.

Aneurysm↗
PubMed1998

Hepatic MRI with SPIO: detection and characterization of focal liver lesions.

A variety of parenterally administered iron oxides have been developed for contrast-enhanced MRI of the liver. Two different classes of iron oxides are currently clinically approved or in phase 3 trials: superparamagnetic iron oxides (SPIO) with a high R2/R1 relaxivity ratio and short blood half-life (AMI-25 and SH U 555 A), and ultrasmall paramagnetic iron oxides (USPIO) with a lower R2/R1 relaxivity ratio and longer blood half-life (AMI-227). All iron oxides significantly increase tumor-to-liver contrast and allow detection of more lesions than unenhanced MRI on T2-weighted images at a field strength of 0.2-1.5 T. Malignant lesions without phagocytic cells exhibit constant signal on T2-weighted accumulation phase images with all three iron oxides. All iron oxides cause a signal decrease of benign lesions with either phagocytic cells or a significant blood pool on T2-weighted accumulation phase images. The signal decrease of benign lesions is proportional to the Kupffer cell activity or tumor vascularity and is useful for lesion characterization. Another enhancement feature for the differentiation of benign from malignant lesions is ring enhancement of malignant lesions (metastases) on T1-weighted enhanced images either during the perfusion phase with SH U 555 A or during the accumulation phase with AMI-227, which is attributed to the blood pool effects of the compounds. Differentiation of lesions and vessels is easier on enhanced images with angiographic effects than on unenhanced images. Iron oxides improve the quality of two-dimensional MR angiography techniques of the portal venous system by decreasing background signal (liver tissue with all iron oxides) and increasing intravascular signal (AMI-227). The use of iron oxides for hepatic MRI provides an alternative to the existing multistep diagnosis with CT, CT portography, MRI and biopsy.

Contrast Media↗
PubMed1998

[T1-weighted dynamic MRI with new superparamagnetic iron oxide particles (Resovist): results of a phantom study as well as 25 patients].

PURPOSE: Evaluation of the diagnostic usefulness of the T1-effect of Resovist (SPIO) for dynamic MRI of the liver. METHOD: In-vitro measurements of a dilution series with T1-weighted FLASH and SE sequences and investigation of 25 patients with known focal liver lesions with a T2-weighted TSE sequence and a dynamic T1-FLASH sequence. RESULTS: T1-weighted MRI with Resovist in vitro showed a positive enhancement at low concentrations and a negative enhancement at higher concentrations. In-vivo T1-weighted dynamic MRI liver parenchyma demonstrated a positive enhancement 30 s post contrast, followed by a continuous slope of signal intensity and a negative enhancement (> or = 60 s). Spleen, portal venous vessels and haemangiomas showed an early increase in signal intensity followed by a decreasing positive enhancement, but without negative enhancement. During the perfusion phase metastases showed a small but not significant increase in signal intensity. In 80% a positive ring enhancement could be observed around metastases. CONCLUSION: Resovist exhibits a diagnostically useful T1-effect. An evaluation of the perfusion of focal liver lesions during the distribution phase is possible with dynamic T1-weighted MRI. This approach may further improve characterisation of focal liver lesions.

Adult↗
PubMed1998

[Combined use of ECK-triggered 2D-phase contrast MR angiography and 2D-time-of-flight MR angiography for planning and follow up before and after vascular intervention of pelvic and leg arteries].

PURPOSE: To develop a strategy for the complete work-up of vessel lumen and vessel wall for planning and follow-up of radiological interventions of lower extremity arteries. METHODS: A total of 36 patients (21 pre-, 8 post- and 7 pre- and postinterventional) were studied. MRA studies were performed using an ECG-triggered phase contrast technique for the demonstration of intraluminal flow and an axial high resolution time-of-flight technique to assess the vascular wall. All MRA studies were analysed by intraindividual DSA comparison for the assessment of flow and wall structures. RESULTS: Combined MRA techniques provided a good correlation with DSA for the assessment of vascular flow. The kappa test revealed a value of greater than 0.61 for most on the vessel segments proving a good correlation of both methods. Orthogonal high-resolution TOF-MRA provided additional information for the assessment postinterventional wall haematomas and hard plaques. CONCLUSION: Combination of PCA to study flow and axial TOF to study wall pathology improves the usefulness of peripheral MRA.

Adult↗
PubMed1998

Breath-hold gadolinium-enhanced MR angiography of the major vessels at 1.0 T: dose-response findings and angiographic correlation.

PURPOSE: To find the appropriate contrast agent dose for gadolinium-enhanced magnetic resonance (MR) angiography by using individual measurement of contrast agent transit times in a randomized study. MATERIALS AND METHODS: A total of 34 patients with disease of the aorta or its major branches or both were randomly assigned to receive a dose of 0.1, 0.2, or 0.3 mmol of gadopentetate dimeglumine per kilogram of body weight. Initially, contrast agent transit times were measured with use of a turbo fast-low-angle-shot sequence. Subsequently, a three-dimensional fast imaging with steady-state precession sequence (7.3-msec repetition time, 2.8-msec echo time) was used for breath-hold MR angiography. Gadopentetate dimeglumine was injected with an MR-compatible power injector. Efficacy was evaluated by measurement of vessel enhancement and by clinical correlation of MR angiograms with x-ray angiograms. RESULTS: Evaluation of contrast agent transit time was possible in all patients with the test doses, which provided contrast-enhanced MR angiograms of constant quality. Neither vessel enhancement nor diagnostic information was significantly different across the these study groups. CONCLUSION: The clinical gadolinium dose of 0.1 mmol/kg is sufficient for diagnostic assessment of the aorta and its major branches at contrast-enhanced MR angiography. High-dose studies appear not to be required for these large vessels.

Adult↗
PubMed1998

T1 effects of a bolus-injectable superparamagnetic iron oxide, SH U 555 A: dependence on field strength and plasma concentration--preliminary clinical experience with dynamic T1-weighted MR imaging.

PURPOSE: To investigate the field strength dependency of relaxivity values with SH U 555 A, concentration-dependent T1 effects, and findings at dynamic T1-weighted magnetic resonance (MR) imaging in patients with focal liver lesions. MATERIALS AND METHODS: Longitudinal relaxivity (r1) with SH U 555 A was measured in human plasma (0.02-300.00 MHz), and transverse relaxivity (r2) was measured at 10, 20, and 40 MHz. Second, a dilution series in human plasma was used at 1-T, T1-weighted, spin-echo or fast low-angle shot (FLASH) imaging. In 22 patients with focal liver lesions, imaging with the latter sequence was performed with a dose of SH U 555 A of 10 mumol Fe/kg. RESULTS: The r1 of SH U 555 A decreased with increasing field strength, but was higher at high field strengths than r1 values for gadolinium chelates. Enhancement calculations for different iron concentrations in human plasma demonstrated positive enhancement at concentrations less than 700 mumol Fe/L. Enhancement increased with the degree of T1 weighting and was highest for the FLASH sequence with the shortest TE (+81.4% with 300 mumol Fe/L). Enhancement was positive in the liver for at least 30 seconds and in the spleen for at least 480 seconds. CONCLUSION: Signal intensity changes at dynamic T1-weighted MR imaging after bolus injection of SH U 555 A can be explained by dynamic changes in iron-plasma concentration.

Contrast Media↗
PubMed1998

[Can noninvasive gadolinium 3D MR subtraction angiography of visceral arteries replace conventional intra-arterial catheter angiography?].

Classic catheter angiography is compared with 3D gadolinium MR angiography for evaluation of the vascular anatomy of the celiac trunk, liver supplying arteries, and the portal venous system. Based on 10 patients, this study shows the value of this new non-invasive method of angiography for the diagnosis of visceral vascular anatomy. For this diagnosis MR angiography is expected to replace conventional angiography in the near future.

Angiography↗
PubMed1997

[High dose chemotherapy with autologous stem cell transplantation].

Subsequent stem cell transplantation makes it possible to increase the dose of oncological chemotherapy by a factor of between three- and ten-fold. For primary treatment, the superiority of this approach vis-a-vis standard doses seems to be highly likely in the case of recurrent highly malignant lymphomas, metastatic mamma carcinomas and plasmacytomas. To date, however, the most favorable time point for high-dose chemotherapy has not yet been definitively established-not has the patient group most likely to benefit or the most effective combination of cytostatics to be used. For this reason, such treatment, even of these diseases, should not be applied outside of controlled studies, and must be viewed even more critically in the case of other diseases for which data from randomized studies are not yet available. Despite a relatively low overall level of toxicity, peripheral blood stem cell transplantation (PBSCT) still has a mortality rate--even in large centers--of 2 to 5%. Any such treatment should therefore be given only in controlled studies and in suitable centers.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

Scintigraphic evaluation of hepatic blood flow after intrahepatic portosystemic shunt (TIPS).

In patients with liver cirrhosis a transjugularly placed intrahepatic portocaval shunt (TIPS) is a non-surgical portosystemic device which aims to reduce portal venous pressure. In comparison with Doppler sonography, we evaluated in 28 patients the diagnostic impact of liver perfusion scintigraphy (with technetium-99m diethylene triamine penta-acetic acid) in the assessment of changes in the hepatic blood flow after TIPS shunting. The arterial and portal contributions to hepatic flow were calculated from the areas under the biphasic time-activity curve. In the course of TIPS shunting, patency is threatened by reocclusion. Angiography is the gold standard for TIPS shunt reassessment. However, there is a need for a less invasive diagnostic procedure, such as scintigraphy or Doppler sonography, for the early detection of shunt insufficiency. Scintigraphy demonstrated that prior to TIPS shunting the portal venous contribution to hepatic perfusion was reduced to 29.2%, this reduction being due to portal hypertension. After TIPS placement a significant increase in portal venous perfusion was observed (38.2%; P<0.02). TIPS shunt occlusion was identified in patients by a significant reduction in the scintigraphically measured portal venous contribution to hepatic blood flow. Hepatic perfusion scintigraphy appears to be a valuable method to determine the immediate effect of TIPS on hepatic blood flow. Post-TIPS follow-up studies of hepatic haemodynamics by liver perfusion scintigraphy appear able to contribute to the detection of TIPS shunt occlusion before the clinical consequences of this complication have become apparent.

Blood Flow Velocity↗
PubMed1997

[Phase-contrast MR angiography of the lower extremity. Comparison of methods and clinical application].

PURPOSE: To investigate whether phase-contrast MRA is a clinically suited approach to examine arteries of the pelvis and lower extremities. METHODS: The study was divided into two parts, a volunteer study and patient study. Three MRA techniques-2D TOF with venous saturation, 3D magnitude contrast and 2D phase contrast with ECG triggering-were intraindividually compared in 15 volunteers and evaluated by three blinded readers. Subsequently, a total of 230 vessel segments of 45 MRA studies using ECG-triggered phase contrast were compared with intraarterial DSA. All vessel segments were scored by three blinded readers using a five-point scale with DSA serving as the gold standard. RESULTS: ECG-triggered phase contrast provided better image quality than the other MRA techniques as assessed by the Friedman test. Clinical studies demonstrated a significant correlation of DSA and MRA as assessed by the Spearman correlation and kappa statistics for individual readers. CONCLUSION: MRA of the pelvis and lower extremities may be performed with 2D ECG-triggered phase-contrast MRA within a reasonable time frame (< 30 min). MRA slabs provide orientation similar to that with DSA projections and good to very good correlation of vessel pathology as shown by kappa statistics.

Angiography, Digital Subtraction↗
PubMed1997

Enhancement characteristics of liver metastases, hepatocellular carcinomas, and hemangiomas with Gd-EOB-DTPA: preliminary results with dynamic MR imaging.

Our objective was to study Gd-EOB-DTPA for the characterization of focal liver lesions by means of dynamic MR imaging. A double-blind and randomized dose-ranging phase-2 clinical trial was performed in 31 patients (liver metastases n = 23, hepatocellular carcinoma n = 4, and hemangioma n = 4) at a field strength of 1.0 Tesla. Gd-EOB-DTPA (Schering AG, Berlin, Germany) was administered as an IV bolus (12.5, 25, or 50 micromol/kg body weight) with dynamic T1-weighted MRI during the distribution and cellular uptake of the contrast agent at multiple time points up to 45 min post contrast. Dynamic changes in tumor signal intensity, tumor-liver contrast, enhancement patterns, side effects, and adverse events were evaluated. Monitoring of vital signs revealed no significant changes during bolus injection of Gd-EOB-DTPA. Liver metastases demonstrated an inhomogeneous uptake of Gd-EOB-DTPA during the distribution phase with a washout effect on delayed images > 3 min and highest tumor-liver contrast 20 and 45 min post contrast. Hepatocellular carcinomas showed prolonged enhancement as compared with metastases and hemangiomas. Hemangiomas exhibited an early peripheral-nodular enhancement with subsequent partial or complete filling, persisting enhancement < 10 min following injection of Gd-EOB-DTPA, and delayed washout as compared with liver metastases. Initial clinical experience suggests that Gd-EOB-DTPA as a bolus injectable hepatobiliary MR contrast agent may offer useful features for the characterization of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1997

Application of a stable cell culture assay for the functional assessment of novel MR contrast agents.

The purpose of this study was to apply a new cell culture assay that preserves hepatocyte orientation and differentiation for screening of MR contrast agents with hepatocyte specificity. Cultured hepatocytes were sandwiched between two layers of collagen, preserving both hepatocyte function and morphology over a prolonged period of time. Plain and rhodaminated monocrystalline iron-oxide particles (MION and MION-rh) and asialoglycoprotein receptor-specific rhodaminated asialofetuin coupled to MION (MION-ASF-rh) were prepared. Dose-dependent competition experiments of these agents were performed with D(+)-galactose to determine the specificity of galactose-mediated cell uptake. To assess the impact of cell integrity on cell uptake dose-dependent functional experiments with two hepatotoxins (ethanol and CCl4) were performed. Normal cell cultures showed significantly higher fluorescent-light emission after incubation with hepatocyte-directed ASF-MION-rh than after incubation with MION-rh. Competition experiments of ASF-MION with galactose showed a dose-dependent decrease in calibrated fluorescent-light emission. Cell cultures treated with hepatotoxins demonstrated a dose-dependent reduction in calibrated fluorescent-light emission following incubation with ASF-MION-rh. The validated assay system allows assessment not only of hepatocyte specificity, but also of hepatocyte damage. Because the assay can be applied to cells from any species (rat, pig, human), it may represent an ideal test system prior to clinical trials of new hepatocyte-directed MR contrast agents.

Animals↗
PubMed1997

Artificially produced cartilage lesions in small joints: detection with optimized MRI-sequences.

The purpose of this study was to evaluate different magnetic resonance imaging (MRI) pulse sequences in the detection of artificial cartilage lesions in small joints using an animal model. A total of 32 artificial cartilage lesions were created in the knee joints of 20 rabbits. Twenty lesions were produced 4 weeks and 12 lesions 1 h before the MRI examination, performed in an extremity coil at 1.0 T. All joints were examined with five imaging sequences: (1) a conventional T1-weighted spin-echo (SE)-sequence (repetition time [TR] 600 ms, echo time [TE] 15 ms), (2) a T2-weighted turbo-SE-sequence (TR 2000 ms, TE 85 ms), (3) a two-dimensional (2D) gradient echo (GE)-sequence (TR 440 ms, TE 10 ms, flip angle 60 degrees) and (4,5) two three-dimensional (3D) GE-sequences (TR 40 ms, TE 7 ms, flip angle 40 degrees, with fat suppression (FS) and TR 30 ms, TE 9 ms, flip angle 40 degrees). Two examinations had to be excluded because of insufficient image quality and the remaining examinations were analyzed by two experienced radiologists. The MRI images were correlated with the pathologic findings and anatomical structures were scored according to a 5-level scale. Direct comparison of the pathological and MRI findings showed that 19 of the 30 artificially induced cartilage lesions were detected with the FS 3D GE-sequence, 13 with the 2D GE-sequence, 11 with the 3D GE-sequence, 3 with the T1-weighted SE-sequence, and 2 with the T1-weighted SE-sequence. The highest percentage of artificial cartilage lesions was demonstrated using a fat-suppressed 3D GE-sequence. However, the analysis of cartilage defects in small joints with optimized sequences as well as clinical routine hardware and software had limitations. Therefore a pilot study was performed analyzing newly developed high resolution FS 3D GE images obtained from 5 rabbit knees with 10 cartilage lesions at 1.5 T. Two sequences were used with 1.0 and 0.5 mm slice thickness, a matrix of 256 x 256 and 512 x 256 and a field of view of 12 x 6 and 8 x 6 cm. In this small subset detection rates were substantially higher than in the 30 rabbit knees examined before.

Animals↗