A Systematic Mapping on the Role-Permission Relationship in Role Based Access Control Models

Access control is a key component of security in any computer system. In the last two decades, the research on Role Basead Access Control Models was intense. One of the most important components of a Role Based Model is the Role-Permission Relationship. In this paper, the technique of systematic mapping is used to identify, extract and analyze many approaches applied to establish the Role-Permission Relationship. The main goal of this mapping is pointing directions of significant research in the area of Role Based Access Control Models.

Mapping virtual networks onto substrate networks

Network virtualization is a promising technique for building the Internet of the future since it enables the low cost introduction of new features into network elements. An open issue in such virtualization is how to effect an efficient mapping of virtual network elements onto those of the existing physical network, also called the substrate network. Mapping is an NP-hard problem and existing solutions ignore various real network characteristics in order to solve the problem in a reasonable time frame. This paper introduces new algorithms to solve this problem based on 0–1 integer linear programming, algorithms based on a whole new set of network parameters not taken into account by previous proposals. Approximative algorithms proposed here allow the mapping of virtual networks on large network substrates. Simulation experiments give evidence of the efficiency of the proposed algorithms.

T2 mapping and dGEMRIC after autologous chondrocyte implantation with a fibrin-based scaffold in the knee: preliminary results

To assess repair tissue (RT) after the implantation of BioCartII, an autologous chondrocyte implantation (ACI) technique with a fibrin-hyaluronan polymer as scaffold. T2 mapping and delayed Gadolinium Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) were used to gain first data on the biochemical properties of BioCartII RT in vivo.

T2 mapping of hip articular cartilage in healthy volunteers at 3T: a study of topographic variation

PURPOSE: To perform baseline T(2) mapping of the hips of healthy volunteers, focusing on topographic variation, because no detailed study has involved hips. T(2) mapping is a quantitative magnetic resonance imaging (MRI) technique that evaluates cartilage matrix components. MATERIALS AND METHODS: Hips of 12 healthy adults (six men and six women; mean age = 29.5 +/- 4.9 years) were studied with a 3.0-Tesla MRI system. T(2) measurement in the oblique-coronal plane used a multi-spin-echo (MSE) sequence. Femoral cartilage was divided into 12 radial sections; acetabular cartilage was divided into six radial sections, and each section was divided into two layers representing the superficial and deep halves of the cartilage. T(2) of these sections and layers were measured. RESULTS: Femoral cartilage T(2) was the shortest (-20 degrees to 20 degrees and -10 degrees to 10 degrees , superficial and deep layers), with an increase near the magic angle (54.7 degrees ). Acetabular cartilage T(2) in both layers was shorter in the periphery than the other parts, especially at 20 degrees to 30 degrees . There were no significant differences in T(2) between right and left hips or between men and women. CONCLUSION: Topographic variation exists in hip cartilage T(2) in young, healthy adults. These findings should be taken into account when T(2) mapping is applied to patients with degenerative cartilage. J. Magn. Reson. Imaging 2007;26:165-171. (c) 2007 Wiley-Liss, Inc.

T2 mapping in the knee after microfracture at 3.0 T: correlation of global T2 values and clinical outcome - preliminary results

OBJECTIVE: The aim of our study was to correlate global T2 values of microfracture repair tissue (RT) with clinical outcome in the knee joint. METHODS: We assessed 24 patients treated with microfracture in the knee joint. Magnetic resonance (MR) examinations were performed on a 3T MR unit, T2 relaxation times were obtained with a multi-echo spin-echo technique. T2 maps were obtained using a pixel wise, mono-exponential non-negative least squares fit analysis. Slices covering the cartilage RT were selected and region of interest analysis was done. An individual T2 index was calculated with global mean T2 of the RT and global mean T2 of normal, hyaline cartilage. The Lysholm score and the International Knee Documentation Committee (IKDC) knee evaluation forms were used for the assessment of clinical outcome. Bivariate correlation analysis and a paired, two tailed t test were used for statistics. RESULTS: Global T2 values of the RT [mean 49.8ms, standards deviation (SD) 7.5] differed significantly (P<0.001) from global T2 values of normal, hyaline cartilage (mean 58.5ms, SD 7.0). The T2 index ranged from 61.3 to 101.5. We found the T2 index to correlate with outcome of the Lysholm score (r(s)=0.641, P<0.001) and the IKDC subjective knee evaluation form (r(s)=0.549, P=0.005), whereas there was no correlation with the IKDC knee form (r(s)=-0.284, P=0.179). CONCLUSION: These findings indicate that T2 mapping is sensitive to assess RT function and provides additional information to morphologic MRI in the monitoring of microfracture.

Comparison of delayed gadolinium enhanced MRI of cartilage (dGEMRIC) using inversion recovery and fast T1 mapping sequences

The delayed Gadolinium Enhanced MRI of Cartilage (dGEMRIC) technique has shown promising results in pilot clinical studies of early osteoarthritis. Currently, its broader acceptance is limited by the long scan time and the need for postprocessing to calculate the T1 maps. A fast T1 mapping imaging technique based on two spoiled gradient echo images was implemented. In phantom studies, an appropriate flip angle combination optimized for center T1 of 756 to 955 ms yielded excellent agreement with T1 measured using the inversion recovery technique in the range of 200 to 900 ms, of interest in normal and diseased cartilage. In vivo validation was performed by serially imaging 26 hips using the inversion recovery and the Fast 2 angle T1 mapping techniques (center T1 756 ms). Excellent correlation with Pearson correlation coefficient R2 of 0.74 was seen and Bland-Altman plots demonstrated no systematic bias.

The template of the primary lymphatic landing sites of the prostate should be revisited: results of a multimodality mapping study

OBJECTIVES: To map the primary prostatic lymphatic landing sites using a multimodality technique. METHODS: Thirty-four patients with organ-confined prostate cancer (cT1-cT2; cN0) underwent single-photon emission computed tomography fused with data from computed tomography (SPECT/CT) (n=33) or magnetic resonance imaging (SPECT/MRI) (n=1) 1h after ultrasound-guided intraprostatic injection of technecium (Tc-99m) nanocolloid. The presence of lymph nodes (LNs) containing Tc-99m was confirmed intraoperatively with a gamma probe. A backup extended pelvic lymphadenectomy (PLND) was performed to preclude missed primary lymphatic landing sites. The SPECT/CT/MRI data sets were used to generate a three-dimensional projection of each LN site. RESULTS: A total of 317 LNs (median, 10 per patient; range, 3-19) were detected by SPECT/CT/MRI, 314 of which were confirmed by gamma probe. With an "extended" PLND, two thirds of all primary prostatic lymphatic landing sites are resected compared with only one third with a "limited" PLND. CONCLUSIONS: The multimodality technique presented here enables precise mapping of the primary prostatic lymphatic landing sites. PLND for prostate cancer should include not only the external and obturator regions as well as the portions medial and lateral to the internal iliac vessels, but also the common iliac LNs at least up to the ureteric crossing, thus removing approximately 75% of all nodes potentially harbouring metastasis.

Laser Doppler imaging for intraoperative human brain mapping

The identification and accurate location of centers of brain activity are vital both in neuro-surgery and brain research. This study aimed to provide a non-invasive, non-contact, accurate, rapid and user-friendly means of producing functional images intraoperatively. To this end a full field Laser Doppler imager was developed and integrated within the surgical microscope and perfusion images of the cortical surface were acquired during awake surgery whilst the patient performed a predetermined task. The regions of brain activity showed a clear signal (10-20% with respect to the baseline) related to the stimulation protocol which lead to intraoperative functional brain maps of strong statistical significance and which correlate well with the preoperative fMRI and intraoperative cortical electro-stimulation. These initial results achieved with a prototype device and wavelet based regressor analysis (the hemodynamic response function being derived from MRI applications) demonstrate the feasibility of LDI as an appropriate technique for intraoperative functional brain imaging.

Piezoelectric alveolar ridge-splitting technique with simultaneous implant placement: a cohort study with 2-year radiographic results

PURPOSE Extended grafting procedures in atrophic ridges are invasive and time-consuming and increase cost and patient morbidity. Therefore, ridge-splitting techniques have been suggested to enlarge alveolar crests. The aim of this cohort study was to report techniques and radiographic outcomes of implants placed simultaneously with a piezoelectric alveolar ridge-splitting technique (RST). Peri-implant bone-level changes (ΔIBL) of implants placed with (study group, SG) or without RST (control group, CG) were compared. MATERIALS AND METHODS Two cohorts (seven patients in each) were matched regarding implant type, position, and number; superstructure type; age; and gender and received 17 implants each. Crestal implant bone level (IBL) was measured at surgery (T0), loading (T1), and 1 year (T2) and 2 years after loading (T3). For all implants, ΔIBL values were determined from radiographs. Differences in ΔIBL between SG and CG were analyzed statistically (Mann-Whitney U test). Bone width was assessed intraoperatively, and vertical bone mapping was performed at T0, T1, and T3. RESULTS After a mean observation period of 27.4 months after surgery, the implant survival rate was 100%. Mean ΔIBL was -1.68 ± 0.90 mm for SG and -1.04 ± 0.78 mm for CG (P = .022). Increased ΔIBL in SG versus CG occurred mainly until T2. Between T2 and T3, ΔIBL was limited (-0.11 ± 1.20 mm for SG and -0.05 ± 0.16 mm for CG; P = .546). Median bone width increased intraoperatively by 4.7 mm. CONCLUSIONS Within the limitations of this study, it can be suggested that RST is a well-functioning one-stage alternative to extended grafting procedures if the ridge shows adequate height. ΔIBL values indicated that implants with RST may fulfill accepted implant success criteria. However, during healing and the first year of loading, increased IBL alterations must be anticipated.

Intraoperative monopolar mapping during 5-ALA-guided resections of glioblastomas adjacent to motor eloquent areas: evaluation of resection rates and neurological outcome.

OBJECT Resection of glioblastoma adjacent to motor cortex or subcortical motor pathways carries a high risk of both incomplete resection and postoperative motor deficits. Although the strategy of maximum safe resection is widely accepted, the rates of complete resection of enhancing tumor (CRET) and the exact causes for motor deficits (mechanical vs vascular) are not always known. The authors report the results of their concept of combining monopolar mapping and 5-aminolevulinic acid (5-ALA)-guided surgery in patients with glioblastoma adjacent to eloquent tissue. METHODS The authors prospectively studied 72 consecutive patients who underwent 5-ALA-guided surgery for a glioblastoma adjacent to the corticospinal tract (CST; < 10 mm) with continuous dynamic monopolar motor mapping (short-train interstimulus interval 4.0 msec, pulse duration 500 μsec) coupled to an acoustic motor evoked potential (MEP) alarm. The extent of resection was determined based on early (< 48 hours) postoperative MRI findings. Motor function was assessed 1 day after surgery, at discharge, and at 3 months. RESULTS Five patients were excluded because of nonadherence to protocol; thus, 67 patients were evaluated. The lowest motor threshold reached during individual surgery was as follows (motor threshold, number of patients): > 20 mA, n = 8; 11-20 mA, n = 13; 6-10 mA, n = 10; 4-5 mA, n = 13; and 1-3 mA, n = 23. Motor deterioration at postsurgical Day 1 and at discharge occurred in 30% (n = 20) and 10% (n = 7) of patients, respectively. At 3 months, 3 patients (4%) had a persisting postoperative motor deficit, 2 caused by vascular injury and 1 by mechanical injury. The rates of intra- and postoperative seizures were 1% and 0%, respectively. Complete resection of enhancing tumor was achieved in 73% of patients (49/67) despite proximity to the CST. CONCLUSIONS A rather high rate of CRET can be achieved in glioblastomas in motor eloquent areas via a combination of 5-ALA for tumor identification and intraoperative mapping for distinguishing between presumed and actual motor eloquent tissues. Continuous dynamic mapping was found to be a very ergonomic technique that localizes the motor tissue early and reliably.

Noninvasive pressure difference mapping derived from 4D flow MRI in patients with unrepaired and repaired aortic coarctation.

PURPOSE To develop a method for computing and visualizing pressure differences derived from time-resolved velocity-encoded three-dimensional phase-contrast magnetic resonance imaging (4D flow MRI) and to compare pressure difference maps of patients with unrepaired and repaired aortic coarctation to young healthy volunteers. METHODS 4D flow MRI data of four patients with aortic coarctation either before or after repair (mean age 17 years, age range 3-28, one female, three males) and four young healthy volunteers without history of cardiovascular disease (mean age 24 years, age range 20-27, one female, three males) was acquired using a 1.5-T clinical MR scanner. Image analysis was performed with in-house developed image processing software. Relative pressures were computed based on the Navier-Stokes equation. RESULTS A standardized method for intuitive visualization of pressure difference maps was developed and successfully applied to all included patients and volunteers. Young healthy volunteers exhibited smooth and regular distribution of relative pressures in the thoracic aorta at mid systole with very similar distribution in all analyzed volunteers. Patients demonstrated disturbed pressures compared to volunteers. Changes included a pressure drop at the aortic isthmus in all patients, increased relative pressures in the aortic arch in patients with residual narrowing after repair, and increased relative pressures in the descending aorta in a patient after patch aortoplasty. CONCLUSIONS Pressure difference maps derived from 4D flow MRI can depict alterations of spatial pressure distribution in patients with repaired and unrepaired aortic coarctation. The technique might allow identifying pathophysiological conditions underlying complications after aortic coarctation repair.

Microscale mapping of alteration conditions and potential biosignatures in basaltic-ultramafic rocks on early Earth and beyond

Subseafloor environments preserved in Archean greenstone belts provide an analogue for investigating potential subsurface habitats on Mars. The c. 3.5-3.4 Ga pillow lava metabasalts of the mid-Archean Barberton greenstone belt, South Africa, have been argued to contain the earliest evidence for microbial subseafloor life. This includes candidate trace fossils in the form of titanite microtextures, and sulfur isotopic signatures of pyrite preserved in metabasaltic glass of the c. 3.472 Ga Hooggenoeg Formation. It has been contended that similar microtextures in altered martian basalts may represent potential extraterrestrial biosignatures of microbe-fluid-rock interaction. But despite numerous studies describing these putative early traces of life, a detailed metamorphic characterization of the microtextures and their host alteration conditions in the ancient pillow lava metabasites is lacking. Here, we present a new nondestructive technique with which to study the in situ metamorphic alteration conditions associated with potential biosignatures in mafic-ultramafic rocks of the Hooggenoeg Formation. Our approach combines quantitative microscale compositional mapping by electron microprobe with inverse thermodynamic modeling to derive low-temperature chlorite crystallization conditions. We found that the titanite microtextures formed under subgreenschist to greenschist facies conditions. Two chlorite temperature groups were identified in the maps surrounding the titanite microtextures and record peak metamorphic conditions at 315 ± 40°C (XFe3+(chlorite) = 25-34%) and lower-temperature chlorite veins/microdomains at T = 210 ± 40°C (lower XFe3+(chlorite) = 40-45%). These results provide the first metamorphic constraints in textural context on the Barberton titanite microtextures and thereby improve our understanding of the local preservation conditions of these potential biosignatures. We suggest that this approach may prove to be an important tool in future studies to assess the biogenicity of these earliest candidate traces of life on Earth. Furthermore, we propose that this mapping approach could also be used to investigate altered mafic-ultramafic extraterrestrial samples containing candidate biosignatures.

Facial Nerve Image Enhancement from CBCT using Supervised Learning Technique

Facial nerve segmentation plays an important role in surgical planning of cochlear implantation. Clinically available CBCT images are used for surgical planning. However, its relatively low resolution renders the identification of the facial nerve difficult. In this work, we present a supervised learning approach to enhance facial nerve image information from CBCT. A supervised learning approach based on multi-output random forest was employed to learn the mapping between CBCT and micro-CT images. Evaluation was performed qualitatively and quantitatively by using the predicted image as input for a previously published dedicated facial nerve segmentation, and cochlear implantation surgical planning software, OtoPlan. Results show the potential of the proposed approach to improve facial nerve image quality as imaged by CBCT and to leverage its segmentation using OtoPlan.

Sentinel node mapping using hysteroscopic injection of indocyanine green and laparoscopic near-infrared fluorescence imaging in endometrial cancer staging.

Herein is presented a technique for minimally invasive sentinel node mapping. The patient had apparently early stage endometrial cancer. Sentinel node mapping was performed using a hysteroscopic injection of indocyanine green followed by laparoscopic sentinel node detection via near-infrared fluorescence. This technique ensures delineation of lymphatic drainage from the tumor area, thus achieving accurate detection of sentinel nodes.

A Specific Mapping Study Using Fluorescence Sentinel Lymph Node Detection in Patients with Intermediate- and High-risk Prostate Cancer Undergoing Extended Pelvic Lymph Node Dissection.

Sentinel lymph node (SLN) detection techniques have the potential to change the standard of surgical care for patients with prostate cancer. We performed a lymphatic mapping study and determined the value of fluorescence SLN detection with indocyanine green (ICG) for the detection of lymph node metastases in intermediate- and high-risk patients undergoing radical prostatectomy and extended pelvic lymph node dissection. A total of 42 patients received systematic or specific ICG injections into the prostate base, the midportion, the apex, the left lobe, or the right lobe. We found (1) that external and internal iliac regions encompass the majority of SLNs, (2) that common iliac regions contain up to 22% of all SLNs, (3) that a prostatic lobe can drain into the contralateral group of pelvic lymph nodes, and (4) that the fossa of Marcille also receives significant drainage. Among the 12 patients who received systematic ICG injections, 5 (42%) had a total of 29 lymph node metastases. Of these, 16 nodes were ICG positive, yielding 55% sensitivity. The complex drainage pattern of the prostate and the low sensitivity of ICG for the detection of lymph node metastases reported in our study highlight the difficulties related to the implementation of SNL techniques in prostate cancer. PATIENT SUMMARY There is controversy about how extensive lymph node dissection (LND) should be during prostatectomy. We investigated the lymphatic drainage of the prostate and whether sentinel node fluorescence techniques would be useful to detect node metastases. We found that the drainage pattern is complex and that the sentinel node technique is not able to replace extended pelvic LND.