Diagnostic pitfalls in postinterventional intraarterial magnetic resonance angiography after recanalization of femoropopliteal arterial occlusions.

BACKGROUND: Magnetic resonance (MR)-guided vascular interventions are of increasing interest, and, with the use of contrast-enhanced techniques, intraarterial contrast-enhanced MR angiography (ia-ce-MRA) competes with intraarterial digital subtraction angiography (ia-DSA) for the diagnostic evaluation of the infrainguinal vessel tree. PURPOSE: To assess the diagnostic value of ia-ce-MRA and high-resolution T1-weighted (hr-T1w) imaging compared to the gold-standard ia-DSA for residual stenosis and local dissections after femoropopliteal recanalization in patients with peripheral arterial occlusive disease (PAOD). MATERIAL AND METHODS: Eight patients with PAOD and short vessel occlusion of their femoropopliteal arteries underwent recanalization and balloon positioning under DSA. Patients were transferred to a short-bore MR scanner. Percutaneous transluminal angioplasty (PTA) was accomplished under MR fluoroscopy. Pre- and postinterventional ia-ce three-dimensional (3D) gradient-echo MRA with gadopentate dimeglumine was performed using the intraarterial introducer sheath. Maximum intensity projections (MIP) and multiplanar reconstructions (MPR) were calculated from the data set. High-resolution T1w images of the angioplasty region before and after dilatation were acquired. Control ia-DSA images were obtained. RESULTS: The postinterventional angioplasty results for stenosis grading were comparable in ia-MRA and ia-DSA. Only two of five local dissections in ia-DSA were visualized with the ia-ce-MRA runs including MIPs and MPRs. To clearly depict dissection, hr-T1w images were needed. CONCLUSION: Grading of stenotic lesions with ia-ce-MRA after PTA is comparable to ia-DSA. Intraarterial ce-MRA with calculated MIPs and MPRs is only partially sufficient to visualize local dissections after PTA. High-resolution T1w images are required for precise diagnosis of dissections in magnetic resonance tomography.

Total-body contrast-enhanced MRA on a short, wide-bore 1.5-T system: intra-individual comparison of Gd-BOPTA and Gd-DOTA.

Total-body contrast-enhanced MRA (CE-MRA) provides information of the entire vascular system according to a one-stop-shop approach. Short, wide-bore scanners have not yet been used for total-body CE-MRA, probably due to their restricted field of view in the z-direction. The purpose of this feasibility study is to introduce an image protocol for total-body MRA on a short, wide-bore system. The protocol includes five to six table-moving steps and two injection runs. Two pharmacologically different contrast materials (CM) were applied in ten healthy volunteers in view of possible CM-dependent influences on the protocol outcome (Gd-Bopta, Gd-Dota). Differences consisted of significantly higher CNR with Gd-Bopta with a mean of 73.8+/-38.7 versus 69.1+/-34.3 (p=0.008), significantly better arterial visualization values with Gd-Dota with a mean of 1.26+/-0.44 versus 1.53+/-0.73 (p=0.003) and a tendency to less venous overlay with Gd-Dota, mean 1.19+/-0.44 and 1.34+/-0.72, respectively (p=0.065) (two-tailed Wilcoxon matched-pairs test). Overall 94% of the steps were valued as qualitatively excellent or good. The good results with both CM suggest a transfer to further patient evaluation.

Positioning accuracy in a registration-free CT-based navigation system.

In order to maintain overall navigation accuracy established by a calibration procedure in our CT-based registration-free navigation system, the CT scanner has to repeatedly generate identical volume images of a target at the same coordinates. We tested the positioning accuracy of the prototype of an advanced workplace for image-guided surgery (AWIGS) which features an operating table capable of direct patient transfer into a CT scanner. Volume images (N = 154) of a specialized phantom were analysed for translational shifting after various table translations. Variables included added weight and phantom position on the table. The navigation system's calibration accuracy was determined (bias 2.1 mm, precision +/- 0.7 mm, N = 12). In repeated use, a bias of 3.0 mm and a precision of +/- 0.9 mm (N = 10) were maintainable. Instances of translational image shifting were related to the table-to-CT scanner docking mechanism. A distance scaling error when altering the table's height was detected. Initial prototype problems visible in our study causing systematic errors were resolved by repeated system calibrations between interventions. We conclude that the accuracy achieved is sufficient for a wide range of clinical applications in surgery and interventional radiology.

Medical technology integration: CT, angiography, imaging-capable OR-table, navigation and robotics in a multifunctional sterile suite.

Technology integration is an enabling technological prerequisite to achieve a major breakthrough in sophisticated intra-operative imaging, navigation and robotics in minimally invasive and/or emergency diagnosis and therapy. Without a high degree of integration and reliability comparable to that achieved in the aircraft industry image guidance in its different facets will not ultimately succeed. As of today technology integration in the field of image-guidance is close to nonexistent. Technology integration requires inter-departmental integration of human and financial resources and of medical processes in a dialectic way. This expanded techno-socio-economic integration has profound consequences for the administration and working conditions in hospitals. At the university hospital of Basel, Switzerland, a multimodality multifunction sterile suite was put into operation after a substantial pre-run. We report the lessons learned during our venture into the world of medical technology integration and describe new possibilities for similar integration projects in the future.

Robotically assisted CT-based procedures.

Since the beginning of 2007 the first six robotically assisted CT-based clinical punctures were performed with a new CE-certified assistance device with CT and MRI compatibility. The cases treated include bone and soft-tissue interventions, closed reduction and percutaneous fixation of pelvic fractures, radiofrequency ablation (RFA) and drainage within a Multifunctional Image-Guided Therapy Suite (MIGTS) under interdisciplinary conditions. The device was successfully integrated within the operating room environment of the MIGTS. The results of the robotically assisted CT-based procedures are promising. Even though further experience is needed in view of team experience, decrease of intervention time and system modifications, the first clinical cases demonstrate the feasibility of the system for various application types. The support offered by the device for trajectory planning, insertion point recognition, and needle guidance is especially beneficial for complex punctures with small target volumes or off-plane trajectories.

[Quality management of interdisciplinary treatment of polytrauma. Possibilities and limits of retrospective routine data collection]. / Qualitätssicherung interdisziplinärer Polytraumaversorgung. Möglichkeiten und Grenzen retrospektiver Standarderfassung.

BACKGROUND: The purpose of this study was to evaluate the quality of interdisciplinary multiple trauma management using routinely taken data. METHODS: A retrospective analysis of all multiple traumatized patients [Injury Severity Score (ISS)>15] in a university hospital (n=172; time period 01.01.1997-31.12.1999) was carried out concerning epidemiological and clinical variables and hospital outcome (p<0.05). RESULTS: The overall mortality was 22% [n=38; expected Trauma Injury Severity Score (TRISS) mortality 29%]. Significant parameters for worse outcome in univariate analysis were age>74 years, hypotension, decreasing hemoglobin level and prothrombin time, decreased Glasgow Coma Scale and the number of erythrocyte or plasma concentrates received in the initial period of treatment. The comparison of our results with the data of the German Association for Trauma Surgery registry demonstrated comparable results with respect to management sequence and outcome. CONCLUSIONS: In the quality management of multiple trauma patients retrospective analysis of routinely registered parameters can be a reliable and practical alternative to time-consuming prospective studies when based on prognostic relevant data. Such a procedure allows a preliminary critical comparison with other centers.

Effect of bolus length of intraarterial injections on contrast-enhanced MR-angiography in patients.

PURPOSE: To perform MR-guided interventions, repetitive injections of contrast agent in the arterial system are necessary. By reducing the intraarterial bolus length during image acquisition and consecutively reducing the gadolinium-chelate-based contrast agent dose, we focus on a comparable vascular depiction. The tradeoff in reducing bolus length is vascular depiction. MATERIALS AND METHODS: Intraarterial gadolinium-chelate injection was performed to depict the femoropopliteal artery and infrapopliteal arteries in six patients. Six measurements with a bolus length of 20% to 100% of the total acquisition time were performed (three-dimensional [3D] Turbo-fast low-angle shot (FLASH) sequence, 1.5 T). Contrast-to-noise ratio (CNR) was determined and a consensus reading of vascular depiction was performed. RESULTS: CNR values comparable 100% of bolus length were obtained for the femoropopliteal artery at >or=40% and for the infrapopliteal arteries at >or=60%. Qualitative analysis demonstrated that a bolus length of >or=60% is necessary to reveal a good diagnostic vascular depiction. CONCLUSION: Quantitatively, a reduction of intraarterial gadolinium-chelate dosage in patients is possible down to 40% in the femoropopliteal artery and to 60% in the infrapopliteal arteries to acquire a CNR comparable to 100% of bolus length. Qualitatively, however, the bolus length can only be reduced down to 60% for both level to produce a good diagnostic vascular depiction and is, for diagnostic purposes, the limiting factor.

Best duplex-sonographic criteria for the assessment of renal artery stenosis--correlation with intra- arterial pressure gradient.

PURPOSE: Colour coded duplex sonography (DS) is widely used for the assessment of renal artery stenosis (RAS). Different criteria have been specified for the detection of significant RAS. The aim of our study was to compare routinely used DS criteria, both with intra-arterial pressure gradients and arteriographic degree of stenosis, and to validate different cut-off points of these DS criteria for the assessment of haemodynamically significant RAS. MATERIALS AND METHODS: We retrospectively analysed forty-nine patients (median age 67 years, 29 male) with RAS documented by duplex sonography, referred for renal arterial subtraction arteriography and intra-arterial pressure measurement (93 renal arteries). DS measurement of peak systolic velocity (PSV) in the main renal artery, the renal/aortal velocity ratio (RAR) and the side-to-side differences of the intrarenal resistive indices (DeltaRI) were correlated to intra-arterial pressure measurements and arteriographic degree of stenosis. Receiver operating characteristics (ROC) were used to determine the best cut-off value of DS criteria. RESULTS: 39 (41 %) renal arteries had normal findings or non significant stenosis < 50 %, 23 (25 %) had a diameter reduction between 50 % and 69 %, and 31 (33 %) > or = 70 %. The systolic pressure gradient showed good correlation with the arteriographic degree of RAS (r = 0.77, p < 0.001) and the PSV measured by duplex sonography (r = 0.67, p < 0.001). Mean systolic pressure gradient was 24 mmHg at 50 % stenosis and 23 mmHg at PSV of 200 cm/sec. A PSV of > or = 200 cm/sec provided a sensitivity of 92 % and specificity of 81 % for detecting RAS of > or = 50 %. Similar results were found for RAR > or = 2.5 with a sensitivity of 92 % and specificity of 79 %. These cut-off values have a negative predictive value of 100 % for excluding high-grade RAS of > or = 70 %. A DeltaRI of > or =0.05 has low sensitivity of 31 %, but a high specificity of 97 % for detecting RAS of > or = 50 %. CONCLUSION: DS measurements and the severity of arteriographic diameter reduction correlate well with systolic pressure gradients. Clinically expedient DS criteria for detecting RAS of > or = 50 % are a PSV of > or = 200 cm/sec or a RAR of > or =2.5. These criteria allow reliable exclusion of severe RAS of > or = 70 %.

Extensive iatrogenic aortic dissection during renal angioplasty: successful treatment with a covered stent-graft.

An extensive iatrogenic aortic type B dissection during percutaneous transluminal renal angioplasty (PTRA) for bilateral renal artery stenosis was treated with a covered stent placed in the right renal artery. Control angiography confirmed closure of the entry. Postprocedural CT demonstrated a thick intramural hematoma (IMH) up to the left subclavian artery. CT follow-up at 8 months showed an almost complete resorption of the IMH. While medical treatment is the standard therapy for type B dissections, closure of the intimal tear with a covered stent may be an additional option in extensive cases during PTRA.

Multiple-trauma management: standardized evaluation of the subjective experience of involved team members.

BACKGROUND AND OBJECTIVE: Staff attitude plays a pivotal role in quality management. The objective of the present study was to further define how interdisciplinary emergency hospital staff experience their daily work and the extent to which the professional speciality and training of an individual influences his/her assessment of multiple-trauma team performance. METHODS: The clinical staff involved in multiple-trauma emergency management of a university hospital was asked to answer a confidential questionnaire. Factorial analysis was used to identify 8 major dimensions from a total of 53 items. RESULTS: The questionnaire was returned by 128 team members. All professional groups were most dissatisfied with the dimensions 'education and training', 'work sequence between specialities' and 'communication between specialities'. Assessment of the quality of in-hospital emergency-trauma management differed significantly between professional specialities (ANOVA, F=5.2; P=0.028); surgeons gave the highest ratings for all but one dimension. Having taken an Advanced Trauma Life Support (ATLS) course influenced significantly the total rating of multiple-trauma treatments of anaesthetists and surgeons (F=5.5; P=0.024). CONCLUSIONS: The perceptions of interdisciplinary trauma team members without the completion of an ATLS training course were that they did not communicate enough with each other and that there were differences between their expectations and reality. The differences and the communication deficits were overcome in team members who had passed an ATLS course.

Percutaneous cervical vertebroplasty in a multifunctional image-guided therapy suite: hybrid lateral approach to C1 and C4 under CT and fluoroscopic guidance.

A 76-year-old patient suffering from two painful osteolytic metastases in C1 and C4 underwent percutaneous vertebroplasty by a hybrid technique in a multi-functional image-guided therapy suite (MIGTS). Two trocars were first placed into the respective bodies of C1 and C4 under fluoroscopic computed tomography guidance using a lateral approach. Thereafter, the patient was transferred on a moving table to the digital subtraction angiography unit in the same room for implant injection. Good pain relief was achieved by this minimally invasive procedure without complications. A hybrid approach for vertebroplasty in a MIGTS appears to be safe and feasible and might be indicated in selected cases for difficult accessible lesions.

[Interdisciplinary emergency room management of trauma patients from the standpoint of coworkers]. / Interdisziplinäres Schockraum-Management unfallchirurgischer Patienten aus der Sicht der Mitarbeitenden.

INTRODUCTION: The purpose of this study was to examine whether staff questionnaire evaluation is useful for quality control in the emergency room (ER) setting. METHODS: Consecutive anonymous questionnaires (Likert scale 1-5) were filled out by the involved medical staff in all ER trauma cases in a university hospital from July 2002 to December 2003 (analysis of variance, P<0.05). RESULTS: In 171 ER cases, 844 staff members responded. Main criticisms concerned time management or satisfaction with personal ER training (Likert <4). Consultants rated the quality of their training significantly higher than younger doctors, two thirds of consultants vs one third of residents having passed an Advanced Trauma and Life Support course (P<0.001). Depending on responders' professional specialties and whether the situation concerned multiple trauma (Injury Severity Score >15), a significant systematic difference resulted. CONCLUSION: Our standardized staff questionnaire evaluation was revealed to be a discriminative instrument for quality management of trauma cases in the ER. To confirm these findings, correlation with clinical outcome data and further validation of the method are needed.

Displaced anterior column acetabular fracture: closed reduction and percutaneous CT-navigated fixation.

The purpose of this study is to demonstrate the feasibility of computer-tomography-navigated closed reduction and percutaneous fixation (CRPF) in a patient with an externally rotated left acetabular fracture. After a follow-up of 18 months the patient was pain-free and had a normal range of motion in both hip joints. Radiologically, the fracture was fully consolidated, remodelled, and there were no signs of osteoarthritis. To our knowledge, CT-navigated CRPF of a rotated acetabular fracture has not been reported before. Further studies regarding the feasibility of the method are warranted.

Delayed union of a sacral fracture: percutaneous navigated autologous cancellous bone grafting and screw fixation.

Delayed or non-union of a sacral fracture is a serious clinical condition that may include chronic pain, sitting discomfort, gait disturbances, neurological problems, and inability to work. It is also a difficult reconstruction problem. Late correction of the deformity is technically more demanding than the primary treatment of acute pelvic injuries. Open reduction, internal fixation (ORIF), excision of scar tissue, and bone grafting often in a multi-step approach are considered to be the treatment of choice in delayed unions of the pelvic ring. This procedure implies the risk of neurological and vascular injuries, infection, repeated failure of union, incomplete correction of the deformity, and incomplete pain relief as the most important complications. We report a new approach for minimally invasive treatment of a delayed union of the sacrum without vertical displacement. A patient who suffered a Malgaigne fracture (Tile C1.3) was initially treated with closed reduction and percutaneous screw fixation (CRPF) of the posterior pelvic ring under CT navigation and plating of the anterior pelvic ring. Three months after surgery he presented with increasing hip pain caused by a delayed union of the sacral fracture. The lesion was successfully treated percutaneously in a single step procedure using CT navigation for drilling of the delayed union, autologous bone grafting, and screw fixation.

Three-point Dixon chemical-shift imaging for evaluating articular cartilage defects in the knee joint on a low-field-strength open magnet.

OBJECTIVE: The purpose of our study was to assess the value of a modified three-point Dixon MR technique for evaluating articular cartilage defects in the knee joint on a low-field-strength open magnet, correlated with arthroscopy. SUBJECTS AND METHODS: Twenty consecutive patients who underwent both MR imaging and arthroscopy of the knee joint for suspected internal derangement were examined. A modified three-point Dixon MR sequence with a single radiofrequency echo single-scan method for water and fat separation with correction of the static field inhomogeneities was performed on a 0.35-T open magnet to obtain fat suppression. The MR images were prospectively evaluated for the presence and grade of articular cartilage defects. RESULTS: Uniform fat suppression was obtained in all patients using the modified three-point Dixon technique. Fifty-nine cartilage abnormalities were identified in 19 patients on the basis of arthroscopy. Forty-seven of 59 arthroscopically proven abnormalities were prospectively detected on MR imaging. Compared with arthroscopy, the overall sensitivity of the modified three-point Dixon technique in detecting cartilage lesions was 80% and the specificity was 73%. Sixty-five percent of the cartilage abnormalities were graded identically on MR imaging and arthroscopy. CONCLUSION: The modified three-point Dixon sequence is a useful technique for achieving fat suppression in the knee joint on a 0.35-T open magnet. It is a sensitive and specific technique for the assessment of cartilage abnormalities in the knee.

MR imaging of the wrist in rheumatoid arthritis using gadobenate dimeglumine.

OBJECTIVE: To determine the dosage of gadobenate dimeglumine (Gd-BOPTA) necessary for MRI of rheumatoid arthritis of the wrist. DESIGN AND PATIENTS: Seven wrists inflamed with rheumatoid arthritis were imaged using a dedicated 0.2-T MR unit. Four cumulative dosages of 0.0125, 0.025, 0.05 and 0.1 mmol/kg body weight (BW) Gd-BOPTA were tested. Three-dimensional T1-weighted gradient-recalled echo sequences (GRE; TR: 100 ms, TE: 18 ms, flip angle 90 degrees , 4:55 min) were acquired prior to an intravenous injection and after each additional dosage of Gd-BOPTA. Relative enhancement, signal-difference-to-noise ratios (SDNRs) and the size of the inflamed tissue were quantified. Three radiologists independently evaluated the image quality, the size and the contrast of the enhancing tissue. RESULTS: The readers agreed on a dose of 0.05 mmol/kg BW as satisfactory for the evaluation of the size of the inflammatory tissue and for determination of bone involvement (kappa = 0.9, P < 0.001). Highly inflammatory pannus was depicted with adequate image contrast using 0.025 mmol/kg BW Gd-BOPTA. According to the SDNR and relative enhancement findings, a dose of 0.05 mmol/kg BW suffices for both off-center and centered regions of tissue inflammation (t-test, P < 0.05). CONCLUSION: Gadolinium-BOPTA is an alternative contrast agent for MRI of rheumatoid disease. This study shows that a dose of 0.05 mmol/kg BW suffices at low field strength.

Harmonic GHz surface-acoustic-wave filters with unidirectional transducers.

The fabrication of fundamental-mode surface-acoustic-wave (SAW) filters for gigahertz frequencies requires an elaborate photolithographic process. In order to reduce process demands or to increase the possible frequency range, interdigital transducers can be designed to work on spatial harmonics. However, harmonic filters are known to be unattractive because of their high insertion loss. It is shown that harmonic gigahertz filters made with unidirectional transducers can have moderate insertion loss. Two third-harmonic filters at 1.4 GHz and 2.5 GHz, using two-phase unidirectional transducers, are described. A simple model for calculating the input impedance of harmonic surface-transverse-wave (STW) transducers is presented.