K. Bohndorf

Muscle cross-section measurement by magnetic resonance imaging.

SummaryMuscle cross-section areas were measured by magnetic resonance imaging (MRI) in the thigh of a human cadaver,. the results being compared with those obtained by photography of corresponding anatomic macroslices. A close correlation was found between MRI and photographic evaluation, differences between the methods ranging from nil to 9.5%, depending on the scan position and the muscle groups. In vivo MRI measurements were performed on 12 female and 16 male students, the objectivity, the test-retest reliability and the variability of the MRI measurements being studied by fixing the scan position either manually or by coronary scan. The latter method appeared to be more objective and reliable. The coefficients of variation for muscle cross-section areas measured by MRI were in the range of those for the planimetry of given cross-section areas. Allowing for differentiation between several small muscle bundles in a given area, MRI proved to be a suitable method to quantify muscle cross-sections for intra- and interindividual analysis of muscle size.

MR imaging of the knee: three-dimensional volume imaging combined with fast processing.

A new examination protocol for patients with suspected meniscal or hyaline cartilage disorders is presented. Knees were imaged with a fast gradient echo imaging sequence with subsequent three-dimensional transformation. Data were transferred to an image processing system that allows reconstruction in any plane desired. Approximately 200 interactively positioned reconstructions are displayed and reviewed in approximately 10 min. Thirty-five patients with suspected meniscal or hyaline cartilage disorders were examined prospectively. All underwent subsequent arthroscopy. The magnetic resonance (MR) diagnosis showed an accuracy of 91.4% compared with arthroscopic findings. Owing to the short imaging time, the proposed procedure permits screening of knee joint disorders with MR.

Stent placement for failed angioplasty of aortic stenoses: Report of two cases

In 2 patients, an aortic stenosis failed to respond adequately to balloon dilatation but was successfully treated by implantation of a self-expandable large caliber endoprosthesis and subsequent balloon angioplasty. Intravascular ultrasound helped to classify the characteristics of the lesion in preparation for intervention.

Follow-up results after stent placement in failing arteriovenous shunts: A three-year experience

Self-expandable endoprostheses were used in 18 failing arteriovenous shunts after unsuccessful balloon dilatation. Technical success was satisfactory with an early patency in 17 of 18 shunts. Thrombosis right after stenting occurred in three shunts but was successfully treated in two. Followup history revealed recurrent events of reobstruction due either to stent or shunt stenoses or thrombosis. Restenosis within the stented segment was responsible for reobstruction in about half the cases. Although patency was low with 27% at 18-month follow-up, repeated intervention established a shunt survival rate of 77% at 18-month follow-up. Stent placement in AV shunts is useful for overcoming acute problems of balloon dilatation but does not prevent restenosis.

Staging of urinary bladder neoplasms with MR imaging: is Gd-DTPA helpful?

This study was performed to investigate whether intravenous administration of Gd-DTPA can improve the accuracy of MR imaging in the detection and staging of bladder neoplasms. In 68 patients with suspected urinary bladder neoplasms, MR examinations were performed with T1-weighted SE sequences before and after intravenous administration of Gd-DTPA. The findings were compared with surgical staging using the TNM classification. Overall staging accuracy of contrast enhanced MR was 46%; if stages Ta-T3a were combined into one group, the accuracy was 69%. Accuracy was low (19%) in tumors without muscular bladder wall invasion (Ta). In cases with extravesical spread (greater than or equal to T3b), the accuracy of staging was 87%. Contrast enhanced MR detected extravesical extension of tumor with a sensitivity of 93% and a specificity of 95%. Contrast enhancement increased the sensitivity for detection of urinary bladder neoplasms from 70% on precontrast T1-weighted scans to 79% on postcontrast scans. In comparison with T2-weighted scans, the Gd-DTPA enhanced T1-weighted scans had better image quality and lower acquisition times.

Gadolinium-enhanced magnetic resonance imaging in the staging of urinary bladder neoplasms.

Magnetic resonance imaging (MRI) proved to be an important diagnostic tool in the correct staging of bladder neoplasms. The advantage of multiplane imaging and high soft-tissue contrast may be extended by the use of MRI contrast media such as the gadoliniumdiethylene-triaminepentaacetic acid complex. In 60 patients with suspected or proved bladder tumors, the results of preoperative gadolinium-enhanced MRI were correlated with the histopathologic findings. The staging accuracy of infiltrating tumors was 83% and sensitivity and specificity 86% and 83%, respectively. Three tumors could only be localized after administration of gadolinium. All active tumors demonstrated significant contrast enhancement after intravenously injected gadolinium. Small papillary tumors or carcinoma in situ remain problematic to preoperative staging procedures. The advantages of gadolinium-enhanced MRI will best be employed in the exact pretherapeutic staging of infiltrative bladder neoplasms or in restaging procedures after chemotherapy and radiotherapy.

Percutaneous thrombectomy of the acutely thrombosed dialysis graft: in vitro evaluation of four devices.

Percutaneous recanalization of completely thrombosed hemodialysis grafts was simulated in a flow model. Thrombus removal was performed by 1) a Trac-Wright catheter; 2) an ultrasound-driven, oscillating probe aspiration thrombectomy (US-OAT) device; 3) an electric motor-driven oscillating probe aspiration thrombectomy (EM-OAT) device; and 4) a rotating spiral aspiration thrombectomy (RAT) device. All devices were able to restore a continuous lumen of the shunt model within 1–5 min, but residual layers of wall-adherent adherent thrombi remained attached, particularly to the inner curvature of the shunt loop. Clot removal rate was 95% for the Trac-Wright catheter, 73% for the US-OAT device, 68% for the EM-OAT device (straight tip catheter), 88% for the EM-OAT device (angulated tip catheter), and 51% for the RAT device. Effluent particle rates for particles >100 μm were 3.6% for the Trac-Wright catheter, 0.6% for US-OAT, and less than 0.1% for the other devices. Compared with the Trac-Wright catheter, the balance of clot-removing efficiency and creation of effluent particles favored the electric oscillating device with the angulated tip catheter, which had a slightly reduced, but still efficient, clot-removing capability and produced almost no effluent particles.

New "mesh basket" for percutaneous removal of wall-adherent thrombi in dialysis shunts.

A new basket, developed for percutaneous removal of wall-adherent thrombi, was tested in model thrombosed hemodialysis shunts, and clinically in two polytetrafluoroethylene grafts and one Brescia-Cimino shunt after recanalization by aspiration thrombectomy. The residual wall-adherent thrombus was removed by one or two passes with the mesh basket. The occlusion material was firmly captured within the mesh and was removed through an 8F sheath without hardly any material being sheared off from the basket. The device adapts well even to tortuous vessel segments and exerts a gentle brush effect. It may prove to be a valuable adjunct to aspiration thrombectomy or to balloon catheter embolectomy.

Gadolinium-DTPA-enhanced MRI of intraocular tumors

The value of gadolinium-enhanced MRI in 30 patients with intraocular lesions has been evaluated. Seventeen patients had a uveal melanoma, two a ciliary body melanoma, three had uveal metastases, one lymphoma, four had senile macula degenerations, and three uveal nevi. Twelve of 17 patients with melanoma were followed up by MRI after ruthenium plaque therapy on 2-4 occasions. Melanomas showed high precontrast signal intensities and only a slight enhancement after intravenous Gd-DTPA was given. After ruthenium plaque therapy precontrast signal intensities (SI) decreased while a moderate signal increase on postcontrast scans was noted. Scars or tumor residues were better delineated on enhanced images. All other tumors than melanotic melanomas showed low SI on precontrast scans and a high signal increase after Gd-DTPA administration. Small amelanotic tumors were better delineated on postcontrast scans. In addition Gd-DTPA-enhanced MRI allowed differentiation between tumor and hemorrhage. No signal increase after Gd-DTPA application was seen in subretinal or vitreous hemorrhages of varying ages.

Technical aspects and results of percutaneous transluminal angioplasty in Brescia-Cimino dialysis fistulas

Our experience with percutaneous transluminal angioplasty for treatment of stenoses and occlusions in surgically created arteriovenous fistulas (Brescia-Cimino) is reported. Methodological aspects are emphasized. Forty-nine PTAs were performed in 36 patients, in 3 combined with the use of a vascular metallic endoprosthesis (Wallstent). The initial success rates for stenoses and occlusions and occlusions were 91% and 77%, respectively. Long stenoses and occlusions (>4 cm) showed significantly worse initial results (55%) as compared to short ones (95%). Of the primarily successfully treated shunts, 90% are still functioning after a mean follow-up time of 8 months. The results indicate that PTA may replace surgical intervention as the primary method for treatment of insufficient flow for internal arteriovenous shunts, provided fresh thrombi are not the cause of the occlusion. Metallic endoprostheses and the use of atherectomy catheters were shown to be a valuable adjunct to classical PTA in selected cases.