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1.
J Hosp Infect ; 143: 1-7, 2024 Jan.
Article in English | MEDLINE | ID: mdl-38529779

ABSTRACT

BACKGROUND: Using robots to handle medical devices in the decontamination area of the Central Sterile Supply Department (CSSD) can reduce risks and address staff shortages. The gripper design must allow reliable cleaning using standard CSSD procedures to avoid build-up of biofilms and possible cross-contamination between different instrument trays and the gripper's functionality. This study explores the design of the robot's gripper regarding cleanability, aiming to determine whether successful cleaning can be achieved even after prolonged drying for a working shift of 8 h. METHODS: We optimized a gripper for cleanability and used it to assess the spread of different test soils depending on different forms of motion. Subsequently, we analysed the cleanability using sheep's blood as test soil, reprocessing the gripper in different assembly configurations after 4 and 8 h of drying, and measuring residual protein. FINDINGS: Based on our investigations, we documented the spread of contamination depending on the type of motion of the gripper's components. Sheep's blood exhibited the highest dispersion among the test soils, permeating through thin crevices. Importantly, all samples displayed residual protein levels below the warning threshold, irrespective of drying time and gripper disassembly or cleaning position. Cleaning in a device-specific optimized position achieved results comparable to cleaning the disassembled individual components. CONCLUSIONS: These findings indicate that cleaning even after one working shift of 8 h and without the labour-intensive disassembly of the gripper is feasible, supporting the future use of robots to handle contaminated medical devices in the CSSD decontamination area.


Subject(s)
Robotics , Humans , Decontamination/methods , Equipment Contamination/prevention & control , Surgical Instruments , Soil
2.
Eur J Med Res ; 28(1): 296, 2023 Aug 25.
Article in English | MEDLINE | ID: mdl-37626380

ABSTRACT

BACKGROUND: Soft-tissue swelling after limb fractures in pediatric patients is well known to be a risk factor for developing acute compartment syndrome (ACS). Clinical assessment alone is uncertain in specific cases. Recently, we proposed a non-invasive ultrasound-based method to objectify muscle compartment elasticity for monitoring. We hypothesize a strong correlation between the soft-tissue swelling after stabilization of upper limb fractures and the compartment elasticity objectified with a novel ultrasound-based approach in pediatric trauma. PATIENTS AND METHODS: In a prospective clinical study, children suffering forearm fractures but not developing an ACS were included. The muscle compartment elasticity of the m. flexor carpi ulnaris was assessed after surgical intervention by a non-invasive, ultrasound-based method resulting in a relative elasticity (RE in %) in both the control (healthy limb) and study group (fractured limb). Soft-tissue swelling was categorized in four different levels (0-3) and correlated with the resulting RE (%). RESULTS: The RE in the study group (15.67%, SD ± 3.06) showed a significantly decreased level (p < 0.001) compared with the control (22.77%, SD ± 5.4). The categorized grade of soft-tissue swelling resulted in a moderate correlation with the RE (rs = 0.474). CONCLUSIONS: The presented study appears to represent a novel approach to assess the posttraumatic pressure changes in a muscle compartment after fracture stabilization non-invasively. In this first clinical study in pediatric cases, our measurement method represents a low-cost, easy, and secure approach that has the potential to substitute invasive measurement of suspected ACS in muscle compartment conditions. Further investigations in lager cohorts are required to prove its daily clinical practicability and to confirm the expected reliability.


Subject(s)
Forearm , Fractures, Bone , Humans , Child , Forearm/diagnostic imaging , Prospective Studies , Reproducibility of Results , Fractures, Bone/diagnostic imaging , Elasticity , Muscles
3.
Injury ; 52(4): 724-730, 2021 Apr.
Article in English | MEDLINE | ID: mdl-33902865

ABSTRACT

PURPOSE: The development of acute compartment syndrome is a serious threat to trauma patients. The clinical assessment alone is not reliable enough to determine the need for fasciotomy in many cases. The Physician´s assessment of the elasticity of the muscle compartment might be particularly important to objectively evaluate the pressure in this enclosed space. The purpose of this study was to determine the observer´s reproducibility, of compartment elasticity measurements by a novel ultrasonic approach. METHODS: Increasing intra-compartmental pressures (ICP) were simulated in a water filled in-vitro model. Pressure related ultrasound was used to determine the relative elasticity (RE) of soft tissue compartments. A pressure transducing probe head was combined with the ultrasonic probe to obtain cross section views of the simulated compartment and to detect the amount of applied pressure by the observer. In this model, the compartment depth without compression (P0) was set to be 100%. Changes of the compartment depth due to a probe pressure of 80 mmHg (P80) were correlated to P0 and an elasticity quotient as a value for RE (%) was calculated. Twelve blinded observers performed measurements for RE determination (%) under three pressure conditions. Reproducibility was calculated using intraclass correlation coefficient (ICC). RESULTS: Measurements (n = 432) revealed that the RE (%) in the control group was 17,06% (SD+/-2,13), whereas the RE of the group ICP30 significantly decreased to 12,66% (SD+/- 1,19) (p<0,001). The ICP50 group revealed a further significant decrease to 8,43% (SD+/- 0,67) (p<0,001). Repeated measurement of RE and ICP showed a high level of correlation (spearman correlation coefficient: roh=0,922). A RE <14% resulted in a sensitivity of 96% and a specificity of 90,3% for diagnosis of an ICP >30 mmHg. ICCinter was 0,986; 95%, CI: 0,977-0,992 (p<0,001). DISCUSSION: The presented ultrasound-based approach reliably assesses the elasticity in a simulated compartment model. In this pioneer study investigating the inter- and intra-observer reproducibility, this method of measurement appears to be of low cost in addition to being an easy and secure approach that may have the potential to substitute invasive measurement. Further investigations are required to improve its feasibility and to confirm the reliability under clinical conditions.


Subject(s)
Compartment Syndromes , Compartment Syndromes/diagnostic imaging , Elasticity , Humans , Pressure , Reproducibility of Results , Ultrasonography
4.
Injury ; 51(2): 301-306, 2020 Feb.
Article in English | MEDLINE | ID: mdl-31784057

ABSTRACT

PURPOSE: Close monitoring of patients at risk to develop an acute compartment syndrome (ACS) is well known to be essential. There is a relevant risk that clinical assessment alone is not reliable enough. Reliable assessment of the elasticity of the muscle compartment might represent a helpful tool to assess the pressure in this enclosed space. Therefore, the purpose of this study was to determine the feasibility of muscle elasticity measurements by a non-invasive device. METHODS: In a prospective study, patients with elevated intra-compartmental pressure (ICP) were included. An ultrasound-based measurement approach was used to determine the relative elasticity (RE) of both, the affected and unaffected limb. A pressure transducing ultrasonic probe head was combined with the probe to obtain cross section views of the anterior tibial compartment and to detect the observer´s amount of pressure applied on the limb surface. The compartment depth without compression (P0) corresponds to 100%. The difference to the compartment depth with a probe pressure of 80mmHg (P80) on the limb (delta) related to P0 resulted in a value of relative elasticity (%). These values were compared with the invasive needle measurement (mmHg) regarding their intra-individual difference and correlation of the compartmental pressure. RESULTS: In six trauma patients the relative elasticity in their paired limbs showed a significant difference. The RE in the healthy compartments revealed a level of 17.95% (SD+/-5,4), whereas the RE of the affected limbs significantly decreased to a mean of 5,14% (SD+/-2,1) (p < 0,0001). The average values of the repetitively measured RE and the ICP showed a high level of correlation (spearman correlation coefficient: roh = 0,929). The RE less than 10,5% of the anterior tibial compartment had a sensitivity of 95,8% and a specificity of 87,5% to an appropriate diagnosis of ACS. DISCUSSION: The presented study appears to represent a promising approach to reliably assess the pressure in a muscle compartment. In this first clinical study, our measurement method represents a low cost, easy and secure approach that has the potential to substitute invasive measurement. Further investigations and development in lager cohorts are required to improve its practicality and to confirm the reliability.


Subject(s)
Compartment Syndromes/diagnosis , Elasticity/physiology , Lower Extremity/diagnostic imaging , Ultrasonography/instrumentation , Acute Disease , Aged , Aged, 80 and over , Case-Control Studies , Compartment Syndromes/physiopathology , Feasibility Studies , Humans , Lower Extremity/physiology , Middle Aged , Muscle, Skeletal/diagnostic imaging , Muscle, Skeletal/physiology , Pressure , Prospective Studies , Reproducibility of Results , Sensitivity and Specificity
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2019: 5278-5282, 2019 Jul.
Article in English | MEDLINE | ID: mdl-31947048

ABSTRACT

Patient transport is a physically demanding task for paramedics. The risk of injuries is high and the early retirement rate in emergency medical services is among the highest compared to other industries. The aim of the SEBARES project is to reduce the workloads for paramedics by introducing a self-balancing patient-transport system with a stair climbing mechanism, which is externally guided by a paramedic. In an earlier study a prototype for flat terrain was set up with a sliding mode controller for the self-balancing mechanism. The performance of the prototype without a patient was evaluated in respect of the ergonomic requirements of the paramedic/user. Furthermore, a simulative study demonstrated a considerable impact of an uncooperative passenger on the self-stabilizing mechanism. Although control of self-stabilizing human transporters in general are well researched, possible negative influences of passengers are currently neglected during modelling and control design. For the described patient-transport application uncooperative behavior is very common. Therefore, this experimental study focuses on the impact of uncooperative patients on the dynamic behavior and influences on controller robustness. The prototype of the transport aid was adapted and 128 trials were conducted with 8 subjects who had to perform 4 different scenarios to simulate uncooperative passengers. The tasks were repeated with different parameter values to evaluate the robustness of a sliding mode controller. The results showed that increasing the robustness can reduce the average force on the paramedic's handle from 60 N to 35 N, while the passenger was performing cyclic movements of the upper body. However, a drawback of high robustness is the occurrence of chattering around the control reference. Further studies will consider adaptive controller design.


Subject(s)
Emergency Medical Services , Emergency Medical Technicians , Workload , Ergonomics , Humans , Transportation of Patients
6.
J Hand Surg Eur Vol ; 43(2): 179-186, 2018 Feb.
Article in English | MEDLINE | ID: mdl-26307143

ABSTRACT

Neither the complex motions of the scapholunate joint, nor the kinematic changes that occur as a result of injury to it, are fully understood. We used electromagnetic tracking within affected bones to evaluate the physiologic motions in the planes of flexion and extension, and of radial and ulnar deviation of human cadaver wrists, before and after complete transection of the scapholunate ligaments. Despite individual variance between each wrist, we were able to establish a pattern in the changes that occurred after scapholunate ligament injury. During the motions examined, the scaphoid showed an increase in translational deviation in almost all motion axes. In contrast, the movement of the lunate seemed to be impaired, especially in radial-ulnar deviation.


Subject(s)
Carpal Joints/physiopathology , Joint Instability/physiopathology , Ligaments, Articular/physiopathology , Lunate Bone/physiopathology , Range of Motion, Articular/physiology , Scaphoid Bone/physiopathology , Cadaver , Humans , Joint Instability/diagnostic imaging , Joint Instability/etiology , Weight-Bearing
7.
Int J Comput Assist Radiol Surg ; 10(1): 11-7, 2015 Jan.
Article in English | MEDLINE | ID: mdl-24817062

ABSTRACT

PURPOSE: Identification of viable myocardial tissue is important for patients with a low left ventricular ejection fraction, since revascularization is effective only if the affected region is viable. After cineangiographic identification of occluded coronary vessels, the myocardial viability is usually determined using cardiac MRI or SPECT. Alternatively, myocardial deformation imaging by echocardiography has been introduced that allows detection of viable myocardium directly within the catheterization laboratory. Multimodality fusion of coronary angiograms and echocardiograms was developed to match viable regions with areas affected by occluded vessels. METHODS: Identification of corresponding myocardial regions in both coronary angiograms and ultrasound scans was performed using multimodality image fusion. Geometrically correct superposition of these images was done to allow direct identification of the involved myocardial regions. An electromagnetic tracking system was used as a common base for co-registration of the images. The system was tested using a phantom test device in a cardiac catheterization laboratory. RESULTS: A 2D projection error of 3.8±1.1 mm was achieved in trials using a cardiac phantom test object. CONCLUSIONS: Superimposition of the occluded coronary artery and the regional myocardial viability was achieved using automated multimodality fusion of coronary angiograms and stress echocardiograms with in vitro experiments. This system is promising for integrated single step angiography and angioplasty that may reduce procedure time, cost and length of hospitalization. Further testing in vivo is needed to verify and validate the system in a clinical setting.


Subject(s)
Coronary Angiography , Echocardiography, Stress , Heart/diagnostic imaging , Multimodal Imaging/methods , Myocardium , Ventricular Dysfunction, Left/diagnosis , Aged , Female , Humans , Middle Aged , Tomography, Emission-Computed, Single-Photon , Ventricular Dysfunction, Left/diagnostic imaging , Ventricular Function, Left/physiology
8.
Z Orthop Unfall ; 152(6): 603-15, 2014 Dec.
Article in German | MEDLINE | ID: mdl-25531522

ABSTRACT

A consideration of the patient-specific biomechanical situation in the context of the surgical planning of total hip arthroplasty is highly recommended and may have a positive impact on the therapeutic outcome. In current clinical practice, surgical planning is based on the status of the individual hip and its radiographic appearance. Several authors proposed different biomechanical modeling approaches for the calculation of the resultant hip force R on the basis of parameters gathered from plain radiography. The comparative study presented in this paper shows that the biomechanical models by Pauwels, Debrunner, Blumentritt and Iglic provide a good approximation of the magnitude of R when compared to the in vivo data from instrumented prostheses. In contrast, the Blumentritt model resulted in abnormally high values. However, the computational results for the orientation of R show a high variability of all modeling approaches and seem to depend more on the model used than on patient-specific parameters.


Subject(s)
Arthroplasty, Replacement, Hip/methods , Biomechanical Phenomena/physiology , Hip Joint/physiopathology , Patient Care Planning , Humans , Models, Theoretical , Patient-Specific Modeling , Range of Motion, Articular/physiology
9.
Article in German | MEDLINE | ID: mdl-25367174

ABSTRACT

Due to increasing automation, the number and complexity of technical components have increased in the medical context (e.g., in the clinic or in the home care sector) in recent years. Besides new effective and efficient therapeutic and diagnostic options, these devices entail a wide range of functions and very complex (often computer-based) user interfaces that may lead to human-induced risk potential. A systematic and early human risk analysis and a usability evaluation allow medical device manufacturers to identify and control risks within the human-machine interaction very efficiently. At the Department of Medical Engineering in the Helmholtz Institute for Biomedical Engineering at the RWTH Aachen University, a formal-analytical methodology and a corresponding software tool for prospective human-risk analysis and model-based usability evaluation has been developed. Based on a twofold approach, user interactive process sequences and their potential impacts on the overall process are identified and the resulting use-related risks are assessed. For this, the tasks are categorized (in system and user tasks) and modeled and temporally related within the framework of a high-level task analysis. Within a subsequent cognitive low-level task analysis, potentially critical parallel process sequences are then tested in order to detect a potential resource overload of the user. The subsequent corresponding human-risk analysis is developed according to a knowledge base (checklist) of taxonomies related to human error. The HiFEM (human-function effect modeling) methodology is universally applicable and can be used for the evaluation of human-computer interfaces as well as for the analysis of purely mechanical control interfaces and simple hand-held instruments (such as a scalpel and implant). In a comparative study, the HiFEM method clearly outperforms the classic FMEA (failure modes and effects analysis) process with regard to effectiveness, efficiency, learnability, and user satisfaction. Especially small and medium-sized enterprises that constitute the medical device industry can be supported by the new methodology in the context of risk management according to ISO 14971 as well as usability engineering in accordance with IEC 62366 and IEC 60601-1-6 as well as EN ISO 9241.


Subject(s)
Equipment Failure Analysis/methods , Equipment and Supplies/classification , Man-Machine Systems , Medical Errors/prevention & control , Risk Assessment/methods , Software , Germany , Meaningful Use/classification
10.
Z Orthop Unfall ; 152(2): 161-9, 2014 Apr.
Article in German | MEDLINE | ID: mdl-24760456

ABSTRACT

BACKGROUND: The hand represents one of the most complex joint mechanisms of the human body. The hand is also an important communication medium. The spectrum of today's hand injuries reaches from minor damage up to complex traumata with loss of several functional aspects. Enormous subsequent economic costs result. The therapeutic re-establishment of the equilibrium between maximum stress and the actual applied stress is the condition for a lifelong joint function. MATERIAL AND METHODS: A literature review about biomechanical wrist models was realised. The previous models found in the literature were systematically analysed as well as verifying their suitability for clinical use regarding pathological changes, therapy approaches and modelling/simulation approaches, respectively, of wrist injuries. RESULTS: The return of the wrist joint biomechanics to the normal condition is a key factor for a successful therapy. Furthermore, it is important for the re-establishment of an unimpaired joint function. Currently, there exist only simplified descriptions and models of the wrist joint, approximated by technical joints and furthermore, they are partially contradictory. Therefore, no uniform validated biomechanical wrist model exists as yet. CONCLUSION: Regarding the arising complex clinical problems, however, a valid biomechanical wrist joint model would be necessary as assistance, in order to improve the success of systematised therapies on the basis of computer-aided model-based planning and intervention.


Subject(s)
Carpal Bones/physiology , Models, Biological , Muscle Contraction/physiology , Muscle, Skeletal/physiology , Range of Motion, Articular/physiology , Wrist Joint/physiology , Computer Simulation , Humans
11.
Ultrasonics ; 54(1): 131-6, 2014 Jan.
Article in English | MEDLINE | ID: mdl-23896623

ABSTRACT

OBJECTIVE: Applying shock waves to the heart has been reported to stimulate the heart and alter cardiac function. We hypothesized that shock waves could be used to diagnose regional viability. METHOD: We used a Langendorff model to investigate the acute effects of shock waves at different energy levels and times related to systole, cycle duration and myocardial function. RESULTS: We found only a small time window to use shock waves. Myocardial fibrillation or extrasystolic beats will occur if the shock wave is placed more than 15 ms before or 30 ms after the onset of systole. Increased contractility and augmented relaxation were observed after the second beat, and these effects decreased after prolonging the shock wave delay from 15 ms before to 30 ms after the onset of systole. An energy dependency could be found only after short delays (-15 ms). The involved processes might include post-extrasystolic potentiation and simultaneous pacing. CONCLUSION: In summary, we found that low-energy shock waves can be a useful tool to stimulate the myocardium at a distance and influence function.


Subject(s)
Heart Rate/physiology , Heart Rate/radiation effects , Heart/physiology , Heart/radiation effects , Myocardial Contraction/physiology , Myocardial Contraction/radiation effects , Ultrasonic Therapy/methods , Animals , Blood Pressure/physiology , Blood Pressure/radiation effects , Dose-Response Relationship, Radiation , High-Energy Shock Waves , In Vitro Techniques , Male , Radiation Dosage , Rats , Rats, Sprague-Dawley
12.
Herz ; 39(5): 586-92, 2014 Aug.
Article in English | MEDLINE | ID: mdl-23793836

ABSTRACT

Seismocardiography (SCG) is a noninvasive technique for recording cardiac vibrations. Changes in these waves have been correlated with chronic and acute alterations in myocardial function. This analysis is complex and clinical integration limited. The current study aimed to simplify the utilization of SCG by fast Fourier transformation for a reliable discrimination between different intra- and postoperative causes of hypotension (i.e., myocardial ischemia or hypovolemia). We operated on nine pigs and recorded SCG at baseline, at hypovolemia (occlusion of the inferior vena cava), and at ischemia (occlusion of the right coronary artery). In conclusion, SCG enables detection and differentiation of ischemia and hypovolemia as important causes of altered myocardial function during and after surgery. Thus, this simple and noninvasive diagnostic tool may be used intra- and postoperatively to identify patients at risk.


Subject(s)
Ballistocardiography/methods , Electrocardiography/methods , Myocardial Contraction/physiology , Myocardial Ischemia/diagnosis , Myocardial Ischemia/physiopathology , Ventricular Dysfunction, Left/diagnosis , Ventricular Dysfunction, Left/physiopathology , Animals , Diagnosis, Differential , Disease Models, Animal , Fourier Analysis , Heart Rate/physiology , Hemodynamics/physiology , Myocardial Ischemia/etiology , Postoperative Complications/diagnosis , Postoperative Complications/etiology , Postoperative Complications/physiopathology , Swine , Ventricular Dysfunction, Left/etiology
15.
J Mol Med (Berl) ; 90(12): 1391-406, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23090009

ABSTRACT

Ischemia/reperfusion injury (IRI) is crucial in the pathology of major cardiovascular diseases, such as stroke and myocardial infarction. Paradoxically, both the lack of oxygen during ischemia and the replenishment of oxygen during reperfusion can cause tissue injury. Clinical outcome is also determined by a third, post-reperfusion phase characterized by tissue remodeling and adaptation. Increased levels of reactive oxygen species (ROS) have been suggested to be key players in all three phases. As a second paradox, ROS seem to play a double-edged role in IRI, with both detrimental and beneficial effects. These Janus-faced effects of ROS may be linked to the different sources of ROS or to the different types of ROS that exist and may also depend on the phase of IRI. With respect to therapeutic implications, an untargeted application of antioxidants may not differentiate between detrimental and beneficial ROS, which might explain why this approach is clinically ineffective in lowering cardiovascular mortality. Under some conditions, antioxidants even appear to be harmful. In this review, we discuss recent breakthroughs regarding a more targeted and promising approach to therapeutically modulate ROS in IRI. We will focus on NADPH oxidases and their catalytic subunits, NOX, as they represent the only known enzyme family with the sole function to produce ROS. Similar to ROS, NADPH oxidases may play a dual role as different NOX isoforms may mediate detrimental or protective processes. Unraveling the precise sequence of events, i.e., determining which role the individual NOX isoforms play in the various phases of IRI, may provide the crucial molecular and mechanistic understanding to finally effectively target oxidative stress.


Subject(s)
NADPH Oxidases/metabolism , Reperfusion Injury/enzymology , Reperfusion Injury/metabolism , Animals , Humans , Oxidative Stress/physiology , Reactive Oxygen Species/metabolism
16.
Unfallchirurg ; 115(9): 802-10, 2012 Sep.
Article in German | MEDLINE | ID: mdl-21327810

ABSTRACT

INTRODUCTION: The aim of this study was the evaluation of a new computer-assisted planning and navigation system based on 2D-fluoroscopy for guidewire insertion in order to perform cannulated screw placement into the femoral neck. The image acquisition process was supported by a radiation-saving procedure called Zero-dose C-arm navigation. MATERIAL AND METHODS: In the context of a sawbone study, we performed insertion of 3 cannulated screws positioned under navigation control as well as using the conventional technique in 12 sawbones. Both procedures were performed using open and closed techniques. RESULTS: The computer-assisted technique significantly reduced the amount of intraoperative fluoroscopic images (open technique: -14±3 images, closed technique: -29.4±6 images). Drilling attempts were reduced in the computer-assisted groups (open technique: -1.2±1 attempts, closed technique: -1.7±1.5 attempts) and the femoral neck area covered by the screws was greater in the navigation-assisted groups (open technique: +32.1±16.3 mm(2), closed technique: +32.6±14.9 mm(2)), There was no difference concerning parallelism of the screws or perforation of femoral neck or head. The operation time was significantly longer in the navigation-assisted groups (open technique: +24.2±2.1 min, closed technique: +22.8±5.8 min). CONCLUSION: The addition of computer-assisted planning and surgical guidance supported by Zero-dose C-arm navigation can be useful for the fixation of medial femoral neck fractures with cannulated screws. Further studies with the goal of reducing the operation time are indispensable before integrating this navigation system into the clinical workflow.


Subject(s)
Bone Screws , Femur Neck/diagnostic imaging , Femur Neck/surgery , Image Interpretation, Computer-Assisted/methods , Prosthesis Implantation/methods , Surgery, Computer-Assisted/methods , Tomography, X-Ray Computed/methods , Fiducial Markers , Humans , Reproducibility of Results , Sensitivity and Specificity
17.
NMR Biomed ; 25(4): 514-22, 2012 Apr.
Article in English | MEDLINE | ID: mdl-21874657

ABSTRACT

The aim of this study was to determine the value of different magnetic resonance (MR) protocols to assess early tumor response to chemotherapy. We used a murine tumor model (TLT) presenting different degrees of response to three different cytotoxic agents. As shown in survival curves, cyclophosphamide (CP) was the most efficient drug followed by 5-fluorouracil (5-FU), whereas the etoposide treatment had little impact on TLT tumors. Three different MR protocols were used at 9.4 Tesla 24 h post-treatment: diffusion-weighted (DW)-MRI, choline measurement by (1) H MRS, and contrast-enhanced MRI using ultrasmall iron oxide nanoparticles (USPIO) targeted at phosphatidylserine. Accumulation of contrast agent in apoptotic tumors was monitored by T(2) -weighted images and quantified by EPR spectroscopy. Necrosis and apoptosis were assessed by histology. Large variations were observed in the measurement of choline peak areas and could not be directly correlated to tumor response. Although the targeted USPIO particles were able to significantly differentiate between the efficiency of each cytotoxic agent and best correlated with survival endpoint, they present the main disadvantage of non-specific tumor accumulation, which could be problematic when transferring the method to the clinic. DW-MRI presents a better compromise by combining longitudinal studies with a high dynamic range; however, DW-MRI was unable to show any significant effect for 5-FU. This study illustrates the need for multimodal imaging in assessing tumor response to treatment to compensate for individual limitations.


Subject(s)
Antineoplastic Agents/therapeutic use , Choline/analysis , Dextrans , Diffusion Magnetic Resonance Imaging/methods , Liver Neoplasms/diagnosis , Liver Neoplasms/drug therapy , Magnetic Resonance Spectroscopy/methods , Magnetite Nanoparticles , Animals , Apoptosis/drug effects , Biomarkers, Tumor/analysis , Cell Line, Tumor , Liver Neoplasms/metabolism , Mice , Protons , Reproducibility of Results , Sensitivity and Specificity , Treatment Outcome
18.
Article in English | MEDLINE | ID: mdl-23366789

ABSTRACT

The intracranial pressure (ICP) waveform contains important diagnostic information. Changes in ICP are associated with changes of the pulse waveform. This change has explicitly been observed in 13 infusion tests by analyzing 100 Hz ICP data. An algorithm is proposed which automatically extracts the pulse waves and categorizes them into predefined patterns. A developed algorithm determined 88 %±8 % (mean ±SD) of all classified pulse waves correctly on predefined patterns. This algorithm has low computational cost and is independent of a pressure drift in the sensor by using only the relationship between special waveform characteristics. Hence, it could be implemented on a microcontroller of a future electromechanic hydrocephalus shunt system to control the drainage of cerebrospinal fluid (CSF).


Subject(s)
Electrodes, Implanted , Hydrocephalus/physiopathology , Intracranial Pressure/physiology , Signal Processing, Computer-Assisted , Algorithms , Arterial Pressure , Humans , Hydrocephalus/cerebrospinal fluid , Pattern Recognition, Automated , Wavelet Analysis
19.
Proc Inst Mech Eng H ; 225(5): 477-86, 2011 May.
Article in English | MEDLINE | ID: mdl-21755777

ABSTRACT

Pertrochanteric femoral fractures are common and intramedullary nailing is an accepted method for their surgical treatment. Accurate placement of the implant is essential to ensure fixation. The conventional technique can require multiple guide wire passes, and relies heavily on fluoroscopy. A computer-assisted planning and navigation system based on two-dimensional fluoroscopy for guide wire placement in the femoral neck has been developed, in order to perform intramedullary pertrochanteric fracture fixation using the proximal femoral nail (PFNA). The planning process was supported by a 'zero-dose C-arm navigation' system. The PFNA was inserted into 12, intact, femoral sawbones guided by the computer-based navigation, and into 12, intact, femoral sawbones using a conventional fluoroscopic-assisted technique. Guide wire and subsequent blade placement in the femoral neck was evaluated. The computer-assisted technique achieved a significant decrease in the number of required fluoroscopic images and in the number of guide wire passes. The obtained average blade placement accuracy in the femoral neck was equivalent to the conventional technique. The operation time was significantly longer in the navigation-assisted group. The addition of computer-assisted planning and surgical guidance to the intramedullary nailing of pertrochanteric femoral fractures offers a number of clinical benefits based on the results of this sawbone study. Further studies including fractured sawbones and cadaver models with extension of the navigation process to all steps of PFNA introduction and with the goal of reducing operation time are indispensable before integration of this navigation system into clinical practice.


Subject(s)
Bone Nails , Femur/surgery , Fluoroscopy/methods , Surgery, Computer-Assisted/methods , Humans , Models, Biological
20.
Rofo ; 183(6): 536-42, 2011 Jun.
Article in German | MEDLINE | ID: mdl-21506071

ABSTRACT

PURPOSE: Dynamic hip screw (DHS) insertion for the fixation of lateral femoral neck fractures is an accepted surgical treatment method. A computer-assisted planning and navigation system based on 2D fluoroscopy has been developed for guidewire insertion in order to perform screw placement. The image acquisition process was supported by a radiation-saving procedure called "zero-dose C-arm navigation". The aim of this study was to evaluate this new system. MATERIALS AND METHODS: In the context of a sawbone study, we inserted dynamic hip screws. The procedure was performed under navigation control and in the conventional technique in 12 sawbones. Both procedures were performed in an open and closed technique. RESULTS: The computer-assisted technique significantly reduced the number of intraoperative fluoroscopic images (open technique: -8.1 ± 0.5; p < 0.001 - closed technique: -12.3 ± 3.7; p < 0.001) and the number of guidewire passes (open technique: -1.3 ± 1.2; p < 0.05 - closed technique: -1.5 ± 1.2; p < 0,05). There was no difference with respect to precision in both groups. The operation time was significantly longer in the navigation-assisted groups (open technique: + 14.6 ± 5.4 min; p < 0.001 - closed technique: + 13 ± 3 min; p < 0.001). CONCLUSION: The addition of computer-assisted planning and surgical guidance supported by "zero-dose C-arm navigation" may be useful for the fixation of lateral femoral neck fractures by the DHS as it reduces the amount of fluoroscopic images and requires fewer drill tracks. Further studies with the goal of reducing the operation time are necessary.


Subject(s)
Bone Screws , Femoral Neck Fractures/surgery , Fluoroscopy , Surgery, Computer-Assisted/standards , Fluoroscopy/standards , Humans , Reproducibility of Results
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