Ulf Teichgräber

Applying value stream mapping techniques to eliminate non-value-added waste for the procurement of endovascular stents

UNLABELLED OJECTIVES: To eliminate non-value-adding (NVA) waste for the procurement of endovascular stents in interventional radiology services by applying value stream mapping (VSM). MATERIALS AND METHODS The Lean manufacturing technique was used to analyze the process of material and information flow currently required to direct endovascular stents from external suppliers to patients. Based on a decision point analysis for the procurement of stents in the hospital, a present state VSM was drawn. After assessment of the current status VSM and progressive elimination of unnecessary NVA waste, a future state VSM was drawn. RESULTS The current state VSM demonstrated that out of 13 processes for the procurement of stents only 2 processes were value-adding. Out of the NVA processes 5 processes were unnecessary NVA activities, which could be eliminated. The decision point analysis demonstrated that the procurement of stents was mainly a forecast driven push system. The future state VSM applies a pull inventory control system to trigger the movement of a unit after withdrawal by using a consignment stock. CONCLUSION VSM is a visualization tool for the supply chain and value stream, based on the Toyota Production System and greatly assists in successfully implementing a Lean system.

Relationship between fetal head station established using an open magnetic resonance imaging scanner and the angle of progression determined by transperineal ultrasound

We investigated the correlation between the angle of progression measured by transperineal ultrasound and fetal head station measured by open magnetic resonance imaging (MRI), the gold standard, in pregnant women at full term.

Quantification of morphologic and hemodynamic severity of coarctation of the aorta by magnetic resonance imaging.

OBJECTIVE As the morpholgic severity of coarctation of the aorta is difficult to assess, especially after previous repair, the value of the technique of multiplanar reconstruction of magnetic resonance imaging data to achieve a 3-dimensional reconstruction of the aortic arch was evaluated and compared to hemodynamic measurements. METHODS AND RESULTS We performed 30 examinations in 27 patients aged from 6 to 54 years, with a mean of 21 years, by magnetic resonance imaging using a 1.5Tesla scanner with a standard body coil. Measurements of flow across the coarctation were performed using phase shift velocity mapping, and peak velocity was calculated at the site of stenosis. Aortic cross-sectional area before, at, and beyond the stenosis was reconstructed 3-dimensionally to calculate a percentage degree of stenosis. Morphologic severity of stenosis was correlated to invasively assessed hemodynamic gradients and morphologic data from biplane angiography in 23 patients. Among the 30 examinations, 24 patients had been previously treated by either surgery, in 17 patients, or balloon dilation, while 6 had native coarctation. 3-dimensional reconstruction was possible in all and better delineated the anatomy concerning the hemodynamic relevance of stenoses even as compared with biplane angiography. The correlation between severity of narrowing assessed by diameter measurements in the biplane angiography and 2-dimensional magnetic resonance imaging was r = 0.94, and multiplanar reformation with 2-dimensional magnetic resonance imaging was r = 0.87 with a tendency of higher grading with the 3-dimensional technique (p = 0.0001). The correlation of 2-dimensional magnetic resonance imaging with invasively measured hemodynamic gradients was r = 0.67 versus r = 0.74 for the areas assessed by multiplanar reformation, indicating that the hemodynamic relevance of a morphological approach to evaluate the degree of a stenosis should better be assessed 3-dimensionally. CONCLUSIONS The 3-dimensional reconstruction of the morphologic severity of coarctation offers additional information over conventional imaging especially in patients with kinking, complex geometry, or collaterals, in whom hemodynamic measurements can become unreliable.

Human birth observed in real-time open magnetic resonance imaging

OBJECTIVE Knowledge about the mechanism of labor is based on assumptions and radiographic studies performed decades ago. The goal of this study was to describe the relationship between the fetus and the pelvis as the fetus travels through the birth canal, using an open magnetic resonance imaging (MRI) scanner. STUDY DESIGN The design of the study used a real-time MRI series during delivery of the fetal head. RESULTS Delivery occurred by progressive head extension. However, extension was a very late movement that was observed when the occiput was in close contact with the inferior margin of the symphysis pubis, occurring simultaneously with gliding downward of the fetal head. CONCLUSION This observational study shows, for the first time, that birth can be analyzed with real-time MRI. MRI technology allows assessment of maternal and fetal anatomy during labor and delivery.

Imaging of primary human hepatocytes performed with micron-sized iron oxide particles and clinical magnetic resonance tomography.

Transplantation of primary human hepatocytes is a promising approach in certain liver diseases. For the visualization of the hepa‐tocytes during and following cell application and the ability of a timely response to potential complications, a non‐invasive modality for imaging the transplanted cells has to be established. The aim of this study was to label primary human hepatocytes with micron‐sized iron oxide particles (MPIOs), enabling the detection of cells by clinical magnetic resonance imaging (MRI). Primary human hepatocytes isolated from 13 different donors were used for the labelling experiments. Following the dose‐finding studies, hepatocytes were incubated with 30 particles/cell for 4 hrs in an adhesion culture. Particle incorporation was investigated via light, fluorescence and electron microscopy, and labelled cells were fixed and analysed in an agarose suspension by a 3.0 Tesla MR scanner. The hepatocytes were enzymatically resuspended and analysed during a 5‐day reculture period for viability, total protein, enzyme leakage (aspartate aminotransferase [AST], lactate dehydrogenase [LDH]) and metabolic activity (urea, albumin). A mean uptake of 18 particles/cell could be observed, and the primary human hepatocytes were clearly detectable by MR instrumentation. The particle load was not affected by resuspension and showed no alternations during the culture period. Compared to control groups, labelling and resuspension had no adverse effects on the viability, enzyme leakage and metabolic activity of the human hepatocytes. The feasibility of preparing MPIO‐labelled primary human hepatocytes detectable by clinical MR equipment was shown in vitro. MPIO‐labelled cells could serve for basic research and quality control in the clinical setting of human hepatocyte transplantation.

Perfusion abnormalities of kidney parenchyma: microvascular imaging with contrast-enhanced color and power Doppler ultrasonography--preliminary results.

The purpose of this study was to evaluate the feasibility of microvascular imaging using contrast‐enhanced color and power Doppler sonography. Ten patients with a focal lesion of the kidney were examined. Three patients were investigated with the polymeric butylcyanacrylate‐based contrast agent SHU 563A, and the remaining patients were investigated with the galactose‐based agent Levovist. It was possible to observe the microvascularization with Levovist during the blood pool phase of the agent over a period of 1 to 3 s at 1 min and 2 min after injection. With SHU 563A, microvascular imaging was possible 0.50 s after injection and lasted for 10.35 min. No intratumoral signals were seen in cysts (n = 6) and the investigated abscess. Weak intratumoral polychromatic effects were observed in both renal cell carcinomas in this series. Metastasis could be differentiated from healthy parenchyma due to lack of the polychromatic effect. SHU 563A is appropriate for performing microvascular imaging. The Levovist‐induced polychromatic effects are smaller, of shorter duration, and observable only during the blood pool phase; thus, the expected diagnostic benefit is limited.

Obese patients in an open MRI at 1.0 Tesla: image quality, diagnostic impact and feasibility

ObjectiveTo investigate the performance of an open MRI system at its conceptual limits by examining excessively obese patients who otherwise could not receive adequate imaging examinations.MethodsTwenty-six excessively obese patients (BMI ≥ 35, average age 46) where CT, standard MR or ultrasound examinations were not possible or not conclusive were referred to an open MRI system at 1.0 Tesla. Image quality was measured by SNR and CNR with the integrated body coil for obese patients and optimal body coils for a regular weight control group (average BMI 23, average age 30). MRI findings were evaluated by a diagnostic impact matrix.ResultsSNR and CNR were generally lower in obese patients when the integrated body coil was used compared to the normal weight group with ideal body coils e.g.: For cerebral imaging T2W TSE (<5% for white matter, ca. 30% for grey matter) and T1W SE (ca. 15% for white matter, <5% for grey matter), for spinal imaging T2W TSE (ca. 35% for disc and vertebral body) and T1W SE (about 2% for disc, ca. 10% for vertebral body). Relevant new diagnoses impacting patient’s therapy were identified in 30% (8/26), the particular medical question of the referring physician could be ruled out as possible reason for the medical condition in 53% (14/26).ConclusionIn excessively obese patients where CT, standard MR or ultrasound examination is not possible or not conlusive open MRI system have great potential in diagnostic evaluation, offering lower but sufficient image quality to impact therapy.

Radiological Interventions for Correction of Central Venous Port Catheter Migrations

PurposeThe purpose of this study was to evaluate radiological-interventional central venous port catheter corrections in migrated/malpositioned catheter tips.Materials and MethodsThirty patients with migrated/malpositioned port catheter tips were included in this retrospective analysis. To visualize the catheter patency a contrast-enhanced port catheter series was performed, followed by transfemoral port catheter correction with various 5-F angiographic catheters (pigtail; Sos Omni), gooseneck snares, or combinations thereof.ResultsOne patient showed spontaneous reposition of the catheter tip. In 27 of 29 patients (93%), radiological-interventional port catheter correction was successful. In two patients port catheter malposition correction was not possible, because of the inability to catch either the catheter tip or the catheter in its course, possibly due to fibrin sheath formation with attachment of the catheter to the vessel wall. No disconnection or port catheter dysfunction was observed after correction.ConclusionsWe conclude that in migrated catheter tips radiological-interventional port catheter correction is a minimally invasive alternative to port extraction and reimplantation. In patients with a fibrin sheath and/or thrombosis port catheter correction is often more challenging.

Imaging of single human carcinoma cells in vitro using a clinical whole-body magnetic resonance scanner at 3.0 T

The purpose of the present study was to examine whether single human carcinoma cells labeled with iron oxide nanoparticles could be detected by magnetic resonance (MR) imaging on a clinical 3‐T scanner using a surface coil only. WiDr human colon carcinoma cells were loaded with two kinds of iron oxide nanoparticles differing by coating and size: aminosilan‐coated (MagForce) and carboxy‐dextran‐coated particles (Resovist). The latter were preferred by the colon carcinoma cell line used here and taken up much faster (12 h) than the smaller carboxydextran‐coated Resovist (48 h). Labeled single carcinoma cells, distributed in an agarose gel in a monodisperse layer as controlled by light microscopy, became detectable as punctuate signal extinctions when using a small circularly polarized surface coil in conjunction with a T2*‐weighted GE sequence at 3 T. The threshold for the detectability of labeled colon carcinoma cells ranged at a load of 4–5 μg iron/106 cells. Obviating the need for special hardware additions, this study opens a new lane for single‐cell tracking on clinical 3‐T MR scanners amenable to patient studies. Magn Reson Med 53:1187–1192, 2005.

Sonographically guided venous puncture and fluoroscopically guided placement of tunneled, large-bore central venous catheters for bone marrow transplantation—high success rates and low complication rates

Background and objectiveTraditionally, large lumen, tunneled central venous catheters have been implanted by surgeons. We used a technique of sonographically guided jugular venous puncture and fluoroscopically guided catheter placement to achieve a high rate of technical success and to reduce complication rates.Materials and methodsBetween June 2002 and December 2006, 186 Patients have been referred to the Radiology Department for 211 implantations of large-lumen, tunneled, central venous catheters. Insertions were performed under maximum sterile barrier in the angio suite using combined sonographic guidance for puncture of the internal jugular vein and fluoroscopy for placement of a triple lumen 12.5 F catheter (Hickman, BARD Murray Hill, NJ, USA).All interventions were performed under local anesthesia without need for anesthesiologic surveillance. Peri- and postinterventional complications were recorded using standardized international recommendations.ResultsCatheter implantation was technically successful in 207 of 211 cases (98.1%). Technical failure resulted in four patients due to chronic occlusions of the superior vena cava. No major complications were recorded. Four (1.9%) accidental arterial punctures occurred periinterventionally; 24 (11.4%) early complications (bleeding, dysfunction, catheter rupture, and infection) and ten (4.7%) late complications (infection, dysfunction) were recorded. A clinically suspected catheter infection required catheter removal in 21 (10%) cases; 11 of 13 non-infectious catheter complications (bleeding, dysfunction, rupture) could be treated successfully by interventional-radiological treatment.ConclusionPercutaneous implantation of large-lumen, tunneled, central venous catheters can be achieved with a high technical success rate and a low complication rate under combined sonographic and fluoroscopic guidance. In cases of mechanical complications, catheter rescue by interventional techniques is possible in the vast majority of cases.