Biomedical subjects

C C Nolte-Ernsting

Publications and source records attributed to C C Nolte-Ernsting.

8 recordsLinked to original sources

PubMed1998

[MR-micturating cystourethrography using radical k-space sampling].

PURPOSE: To investigate the feasibility of micturating cystourethrography (MCU) by means of real-time MR imaging with radial k-space sampling. METHODS: The MR-MCU was performed in 7 adult male patients subsequent to a gadolinium(Gd)-DTPA-enhanced excretory MR-urography. The Gd-enhancement of the urethra was visualized by MR-fluoroscopy using a T1-weighted gradient-echo-sequence with radial k-space sampling and a slice thickness of 10 mm. RESULTS: The proposed technique allowed in all 7 patients a dynamic realtime imaging of the Gd-flow inside the urethra during micturition. The normal anatomy of the entire course of the urethra was demonstrated in each patient, while simultaneously the relation to the prostate and pelvic floor became visible. Furthermore, the urinary bladder could be assessed by interactive repositioning of the slice orientation in any preferred direction. The ureters could also be visualized due to the persisting Gd-enhancement of the upper urinary tract after the preceding MR-urography. CONCLUSIONS: MR-MCU using Gd-DTPA and radial k-space data acquisition is a novel imaging modality for a real-time visualization of the urethra during micturition without radiation exposure. This method also allows the assessment of the bladder, the pelvic floor, and the Gd-filled upper urinary tract which suggests a potential for the diagnosis of vesicoureteral reflux and urinary incontinence.

Adult↗

PubMed1998

[MRI-guided percutaneous nephrostomy of the contrast-enhanced, nondilated upper urinary tract: initial experimental results].

PURPOSE: To evaluate technique and practicability of MR-guided percutaneous nephrostomy (MRPCN) in an animal model. METHODS: In three domestic pigs, a unilateral percutaneous nephrostomy tube was placed into the nondilated collecting system using exclusively MR-guidance with a standard 1.5 T scanner. The urinary tract was visualized by intravenous injection of Gd-DTPA and low-dose furosemide. The entire interventional procedure was controlled using a T1-weighted "dual stack" 2 D TFE sequence in two orthogonal planes. RESULTS: In all three animals, the puncture needle was safely directed into the nondilated target calyx. Even slight deviations of the needle from the optimal path were readily detected on both MR image planes which enabled immediate correction. This technique successfully achieved a "first attempt" puncture of the targeted calyx in each animal. Over a nitinol guidewire a 5 F catheter was placed into the renal pelvis. Its dysprosium labelled tip was accurately delineated on contrast-enhanced MR images. CONCLUSIONS: Percutaneous nephrostomy under MR guidance is a very feasible technique for puncturing the nondilated pelvicalyceal system. This procedure offers some advantages over the current standard modalities.

Animals↗

PubMed1998

[Real-time MRI with radial k-radial scanning technique for control of angiographic interventions].

PURPOSE: To test the feasibility of real-time MR controlled guidance of field-inhomogeneity catheters in vitro and in vivo as a first step to MR-guided angiographic interventions. METHODS: Applying a combination of radial scanning with the sliding window reconstruction technique, a frame rate of 23 low resolution images per second was achieved. Field inhomogeneity catheters were steered through a flow phantom and into the renal arteries of a pig. RESULTS: It was possible to visualize flow or, respectively, vessels and to depict catheter movements. This enabled real-time MR-guidance of the catheter into the renal arteries of the flow phantom and into those of the pig. CONCLUSIONS: The new technique yields a sufficiently high temporal resolution for MR-guidance of catheters through vessels.

Angiography↗

PubMed1998

Gadolinium-enhanced excretory MR urography after low-dose diuretic injection: comparison with conventional excretory urography.

PURPOSE: To evaluate the clinical utility and morphologic accuracy of gadolinium-enhanced excretory magnetic resonance (MR) urography after low-dose diuretic injection and to correlate the results with those of conventional urography. MATERIALS AND METHODS: In 71 patients with urologic symptoms, excretory MR urography was performed after intravenous injection of 5-10 mg furosemide and, 30-60 seconds later, 0.1 mmol of gadopentetate dimeglumine per kilogram of body weight. The MR urograms were interpreted by three radiologists, who were blinded to the clinical outcome, and subsequently compared with conventional urograms. RESULTS: Injection of furosemide before contrast material led to rapid, uniform gadolinium distribution inside a sufficiently distended collecting system such that there was no excessive concentration of gadolinium in the urine. In patients with normal or moderately reduced excretory function, this effect allowed complete visualization of the urinary tract within 5-20 minutes of contrast material injection while minimizing gadolinium-related endoluminal T2* effects. The clinical course helped verify almost all MR urographic results. The MR urographic technique was significantly superior to conventional urography in the assessment of the ureters and bladder (P < .0001). Delineation of small caliceal abnormalities is still problematic. The best depiction of the pelvicaliceal system was obtained with fat-suppressed MR imaging, although it was still slightly inferior to conventional urography (P < .05). CONCLUSION: Gadolinium-enhanced excretory MR urography performed after low-dose diuretic injection is a promising and accurate alternative to conventional excretory urography for imaging the morphology of the urinary tract.

Adult↗

PubMed1997

[Flow direction-sensitive spin-echo MR angiography].

New blood pool contrast agents yield a significant shortening of T1 of blood. Consequently, the usual techniques of time-of-flight and phase-contrast angiographies cannot produce angiograms sensitive to one flow direction, even if saturation slabs are applied. It was our aim to test the hypothesis of displaying arterial and venous flow selectively with a specially designed spin echo sequence even after administration of contrast agents. Parallel slice selective 90-degree and 180-degree pulses were applied. The distance between slices could be varied. It was attempted to obtain MR angiographies that were flow sensitive for one direction only. We performed flow phantom studies without the use of contrast media and first in vivo experiments in pigs after administration of iron oxide particles. With our modified spin echo sequence unidirectional flow can be displayed, whereas stationary tissue is totally suppressed. There are no special demands for the hardware and no additional postprocessing needs to be performed. The locally off-centred 90-degree and 180-degree pulses are responsible for this. Exclusively, protons excited by the 90-degree pulse and flowing into the slice of the 180-degree pulse will be refocused and only such protons will give rise to signal in the images.

Animals↗

PubMed1996

Optimizing joint imaging: MR imaging techniques.

For optimizing MR imaging of the joints, a sophisticated knowledge of MR system hard- and software conditions and coil technologies, sequence and contrast preparation techniques, and the use of paramagnetic contrast agents is necessary. This review article discusses the basic principles of the appropriate use of surface coils as well as the different conventional and fast imaging sequences, including three-dimensional (3D) MR imaging. In addition, the applications of contrast agents as well as the most important contrast preparation techniques are reviewed.

Humans↗

PubMed1996

MRI of degenerative bone marrow lesions in experimental osteoarthritis of canine knee joints.

OBJECTIVE: The objective of this study was to determine the value of MRI in the detection of degenerative bone marrow abnormalities in an animal osteoarthritis model. DESIGN: In 10 dogs with experimentally induced unilateral osteoarthritis of the knee, MRI was performed using two-dimensional spin-echo (2D-SE) and three-dimensional gradient-echo (3D-GE) imaging. Contrast enhanced T1-weighted 2D-SE sequences were also obtained after injection of gadolinium-DTPA. The results were compared with the gross and histopathologic findings and with radiography. RESULTS: Histopathologic specimens revealed 21 osteosclerotic lesions and 5 intraosseous cysts. On 2D-SE images, 24 of 26 lesions were detected, while 21 of 26 lesions were identified on 2D-GE sequences. Radiography, including conventional tomography, demonstrated 9 of 26 lesions. Regardless of the sequence weighting, all osteosclerotic lesions appeared hypointense on MRI. Signal loss in bone sclerosis resulted primarily from the reduction of intact fat marrow, the increased bone density being of secondary importance. Quantitative signal analysis allowed approximate estimation of the grade of sclerosis. On postcontrast images, sclerotic bone remained hypointense, although significant but non-specific enhancement relative to the normal fat marrow was observed. The extent of contrast enhancement did not correlate with the grade of osteosclerosis. All five cysts were readily diagnosed by MRI. Cysts displayed either central or marginal contrast enhancement within their cavities. CONCLUSIONS: MRI provides a sensitive method for the diagnosis of osteoarthritic bone abnormalities, allowing their differentiation from most non-degenerative subarticular lesions.

Animals↗

PubMed1995

[The MRT of osteophytosis in experimental gonarthrosis].

PURPOSE: The value of MRI for the detection of knee osteophytosis was determined in an animal osteoarthritis model. METHODS: 10 dogs with experimentally induced unilateral osteoarthritis of the knee were investigated with MRI including 2-D-spin echo (SE) and 3-D-gradient echo (GE) imaging. The results were correlated with gross and histopathologic findings and with radiography. RESULTS: Osteophyte formation appeared early in the osteoarthritic process. Pathological analysis yielded 65 osteophytes. With 3-D-GE imaging, 91% of the osteophytes were detected, while 68% were visible on 2-D-SE images. With two-level radiography, 43% of the osteophytes were diagnosed. Additional use of tunnel view and conventional tomography increased the detection rate to 65%. Independent of the imaging technique, MRI revealed three different signal patterns of the osteophyte bone structure. Compared with the histologically evident fat marrow content and the grade of bone sclerosis, best agreement was achieved with 2-D-SE sequences. However, a discrepancy remained in 22%. A fibrocartilaginous layer at the osteophyte surface could be delineated especially on 3-D-GE images. CONCLUSIONS: MRI provides the highest standard in non-invasive diagnosis of osteophytes in the knee. 3-D-GE imaging in particular can demonstrate early and small osteophyte formation.

Animals↗