A parametric study assessing Implicit Solver limits for a generic FEM Simulation of PTA without stent deployment.

This study focuses on the robustness of a generic Finite Element Model (FEM) of Percutaneous Transluminal Angioplasty (PTA) procedure with permanent set. The influence of three different parameters on simulation robustness were investigated: the stenosis percent, the stenosis offset and the arterial caliber. Five arterial calibers are modeled by adapting the ratio between the inner diameter and the wall thickness. Overall, forty configurations were tested with the same simulation settings and boundary conditions. Results shows convergence issues caused by excessive deformations of elements for stenosis above 65% blockage. Moreover, an increasing stenosis offset tends to decrease convergence. Simulation of PTA on small calibers and large calibers are less robust than intermediate e.g., iliac calibers.Clinical Relevance- PTA can benefit from numerical tools to improve the procedure outcomes. A FEM simulation of PTA without stent deployment can predict the permanent strain induced by this surgery for various configurations. However, robustness of the simulation is required to consider its transfer to clinics. This work aims to determine the robustness boundaries of an implicit solver for PTA simulation. It shows that an implicit solver is robust for all artery calibers with a stenosis below 50% blockage. Moreover medium-caliber arteries exhibit better robustness with converging solutions for stenosis reaching 60% blockage.

The influence of angioplasty balloon sizing on acute post-procedural outcomes: a Finite Element Analysis.

Atherosclerosis is one of the most common vascular pathologies in the world. Among the most commonly performed endovascular treatments, percutaneous transluminal angioplasty (PTA) has been showing significantly positive clinical outcomes. Due to the complex geometries, material properties and interactions that characterize PTA procedures, finite element analyses of acute angioplasty balloon deployment are limited. In this work, finite element method (FEM) was used to simulate the inflation and deflation of a semi-compliant balloon within the 3D model of a stenosed artery with two different plaque types (lipid and calcified). Self-defined constitutive models for the balloon and the plaque were developed based on experimental and literature data respectively. Balloon deployment was simulated at three different inflation pressures (10, 12 and 14 atm) within the two plaque types. Balloon sizing influence on the arterial elastic recoil obtained immediately after PTA was then investigated. The simulated results show that calcified plaques may lead to higher elastic recoil ratios compared to lipid stenosis, when the same balloon inflation pressures are applied. Also, elastic recoil increases for higher balloon inflation pressure independent of the plaque type. These findings open the way for a data-driven assessment of angioplasty balloon sizing selection and clinical procedures optimization.Clinical Relevance- The FE model developed in this work aims at providing quantitative evaluation of recoil after balloon angioplasty. It may be useful for both manufacturers and clinicians to improve efficiency of angioplasty balloon device design and sizing selection with respect to plaque geometry and constitution, consequently enhancing clinical outcomes.

Patient-specific and real-time model of numerical simulation of the hemodynamics of type B aortic dissections.

INTRODUCTION: Regular monitoring of uncomplicated type B aortic dissection is essential because 25-30% will progress to aneurysmal form. The predictive factors of this evolution are not clearly defined, but they seem to be correlated with hemodynamic data. HYPOTHESIS: Our goal is to create a patient-specific and real-time model of numerical simulation of the hemodynamics of uncomplicated type B aortic dissections in order to predict the evolution of these pathologies for earlier treatment. METHOD: This model consists in a coupling 0D (hydraulic-electric analogy) - 3D (CT angiography segmentation) of the aortic arch with optimization by comparison to the 2D Phase Contrast MRI data and using Reduced Order Models to drastically reduce computing times. We tested our model on a healthy and a dissected patient. Then we realized different systolic blood pressure scenarios for each case, which we compared. RESULTS: In the dissected patient, the blood pressure at the false lumen wall was less important than the true lumen. Furthermore, the aortic wall shear stress and the velocity fields in aorta increase at the entry and re-entry tears between the two lumens. The simulation of different blood pressures scenarios shows a decrease in all these three parameters related to the decrease of the systolic blood pressure. CONCLUSION: Our model provides reliable patient-specific and real-time 3D rendering. It has also allowed us to realize different flow variation scenarios to simulate different clinical conditions and to compare them. However, the model still needs improvement in view of a daily clinical application.

Deformable image registration for dose mapping between external beam radiotherapy and brachytherapy images of cervical cancer.

For locally advanced cervical cancer (LACC), anatomy correspondence with and without BT applicator needs to be quantified to merge the delivered doses of external beam radiation therapy (EBRT) and brachytherapy (BT). This study proposed and evaluated different deformable image registration (DIR) methods for this application. Twenty patients who underwent EBRT and BT for LACC were retrospectively analyzed. Each patient had a pre-BT CT at EBRT boost (without applicator) and a CT and MRI at BT (with applicator). The evaluated DIR methods were the diffeomorphic Demons, commercial intensity and hybrid methods, and three different biomechanical models. The biomechanical models considered different boundary conditions (BCs). The impact of the BT devices insertion on the anatomy was quantified. DIR method performances were quantified using geometric criteria between the original and deformed contours. The BT dose was deformed toward the pre-CT BT by each DIR method. The impact of boundary conditions to drive the biomechanical model was evaluated based on the deformation vector field and dose differences. The GEC-ESTRO guideline dose indices were reported. Large organ displacements, deformations, and volume variations were observed between the pre-BT and BT anatomies. Rigid registration and intensity-based DIR resulted in poor geometric accuracy with mean Dice similarity coefficient (DSC) inferior to 0.57, 0.63, 0.42, 0.32, and 0.43 for the rectum, bladder, vagina, cervix and uterus, respectively. Biomechanical models provided a mean DSC of 0.96 for all the organs. By considering the cervix-uterus as one single structure, biomechanical models provided a mean DSC of 0.88 and 0.94 for the cervix and uterus, respectively. The deformed doses were represented for each DIR method. Caution should be used when performing DIR for this application as standard techniques may have unacceptable results. The biomechanical model with the cervix-uterus as one structure provided the most realistic deformations to propagate the BT dose toward the EBRT boost anatomy.

Patient-Specific Finite-Element Simulation of the Insertion of Guidewire During an EVAR Procedure: Guidewire Position Prediction Validation on 28 Cases.

OBJECTIVE: Validation of a numerical method to compute arterial deformations under the insertion of an "extra-siff" guidewire during Endovascular Repair of Abdominal Aortic Aneurysm. METHODS: We propose the validation of a previously developed simulation method. The model is calibrated using anatomical hypothesis and intraoperative observations. Simulation results are blindly evaluated against 3-D imaging data acquired during the surgical procedure on 28 patients, based on the predicted position of the intraoperative guidewire. RESULTS: Simulation was successfully conducted on the 28 patients. The mean position error given by the Modified Hausdorff Distance for the 28 cases was 3.8 ± 1.9 mm, which demonstrates very good results for most of the cases. CONCLUSION: The work reported here shows that numerical simulation can predict some rather large variations in the vascular geometry due to tools insertion, for a wide variety of aorto-iliac morphologies. This is a new step toward clinically applicable mechanical simulation. SIGNIFICANCE: Validation on 3-D intraoperative data on a large number of cases-robustness on adverse anatomies.

A Nomogram to predict parotid gland overdose in head and neck IMRT.

PURPOSES: To generate a nomogram to predict parotid gland (PG) overdose and to quantify the dosimetric benefit of weekly replanning based on its findings, in the context of intensity-modulated radiotherapy (IMRT) for locally-advanced head and neck carcinoma (LAHNC). MATERIAL AND METHODS: Twenty LAHNC patients treated with radical IMRT underwent weekly computed tomography (CT) scans during IMRT. The cumulated PG dose was estimated by elastic registration. Early predictors of PG overdose (cumulated minus planned doses) were identified, enabling a nomogram to be generated from a linear regression model. Its performance was evaluated using a leave-one-out method. The benefit of weekly replanning was then estimated for the nomogram-identified PG overdose patients. RESULTS: Clinical target volume 70 (CTV70) and the mean PG dose calculated from the planning and first weekly CTs were early predictors of PG overdose, enabling a nomogram to be generated. A mean PG overdose of 2.5Gy was calculated for 16 patients, 14 identified by the nomogram. All patients with PG overdoses >1.5Gy were identified. Compared to the cumulated delivered dose, weekly replanning of these 14 targeted patients enabled a 3.3Gy decrease in the mean PG dose. CONCLUSION: Based on the planning and first week CTs, our nomogram allowed the identification of all patients with PG overdoses >2.5Gy to be identified, who then benefitted from a final 4Gy decrease in mean PG overdose by means of weekly replanning.

A versatile intensity-based 3D/2D rigid registration compatible with mobile C-arm for endovascular treatment of abdominal aortic aneurysm.

PURPOSE: Augmented reality-assisted surgery requires prior registration between preoperative and intraoperative data. In the context of the endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm, no satisfactory solution exists at present for clinical use, in particular in the case of use with a mobile C-arm. The difficulties stem in particular from the diversity of intraoperative images, table movements and changes of C-arm pose. METHODS: We propose a fast and versatile 3D/2D registration method compatible with mobile C-arm that can be easily repeated during an EVAR procedure. Applicable to both vascular and bone structures, our approach is based on an optimization by reduced exhaustive search involving a multi-resolution scheme and a decomposition of the transformation to reduce calculation time. RESULTS: Registration was performed between the preoperative CT-scan and fluoroscopic images for a group of 26 patients in order to confront our method in real conditions of use. The evaluation was completed by also performing registration between an intraoperative CBCT volume and fluoroscopic images for a group of 6 patients to compare registration results with reference transformations. The experimental results show that our approach allows obtaining accuracy of the order of 0.5 mm, a computation time of [Formula: see text] and a higher rate of success in comparison with a classical optimization method. When integrated in an augmented reality navigation system, our approach shows that it is compatible with clinical workflow. CONCLUSION: We presented a versatile 3D/2D rigid registration applicable to all intraoperative scenes and usable to guide an EVAR procedure by augmented reality.

Safety and accuracy of endovascular aneurysm repair without pre-operative and intra-operative contrast agent.

BACKGROUND: Severe chronic kidney disease is a major limitation for endovascular aortic aneurysm repair (EVAR). The aim of this study is to assess the safety and accuracy of fusion imaging, when performing EVAR in the absence of pre- and intra-operative contrast agents. METHODS: From October 2013 to February 2014, every patient requiring EVAR and presenting with severe chronic renal impairment underwent a specific pre-operative imaging assessment, based on a non-enhanced CT scan. Centrelines were manually extracted and key points were placed at the landing zones. In house software makes it possible to artificially enhance the contrast between vascular structures and the surrounding tissue, by increasing the values attributed to the vascular structure voxels (500 Hounsfield units). EVAR was performed in a hybrid room (Zeego, Siemens), and the artificially enhanced CT scan was used for the construction of fusion imaging. The 3D vascular volume, together with the centrelines and key points, was overlaid onto the 2D live fluoroscopic image. RESULTS: Six patients (mean age 77.1 years) were treated by EVAR (5 abdominal aneurysms and 1 thoracic aneurysm), using fusion imaging without a contrast agent. The median pre-operative estimated glomerular filtration rate (eGFR) was 17.5 mL/min/1.73 m2. No contrast was used during the procedure. No intra-operative endoleak was observed on the duplex scan. No deterioration was observed in the eGFR at 1 week (eGFR = 21.7, p = .49), nor at 1 month follow up (eGFR = 21, p = .28). The stent graft positioning error was assessed in terms of the difference between the effective and planned landing zones, measured on pre- and post-operative CT scans. The mean error was 1.3 mm at the proximal landing zone, and 6.5 mm at the distal landing zone. CONCLUSION: EVAR without the use of pre-operative and intra-operative contrast agents appears to be safe and accurate for patients with severe chronic kidney disease.

A new pencil beam model for photon dose calculations in heterogeneous media.

The pencil beam method is commonly used for dose calculations in intensity-modulated radiation therapy (IMRT). In this study, we have proposed a novel pencil model for calculating photon dose distributions in heterogeneous media. To avoid any oblique kernel-related bias and reduce computation time, dose distributions were computed in a spherical coordinate system based on the pencil kernels of different distances from source to surface (DSS). We employed two different dose calculation methods: the superposition method and the fast Fourier transform convolution (FFTC) method. In order to render the superposition method more accurate, we scaled the depth-directed component by moving the position of the entry point and altering the DSS value for a given beamlet. The lateral components were thus directly corrected by the density scaling method along the spherical shell without taking the densities from the previous layers into account. Significant computation time could be saved by performing the FFTC calculations on each spherical shell, disregarding density changes in the lateral direction. The proposed methods were tested on several phantoms, including lung- and bone-type heterogeneities. We compared them with Monte Carlo (MC) simulation for several field sizes with 6 MV photon beams. Our results revealed mean absolute deviations <1% for the proposed superposition method. Compared to the AAA algorithm, this method improved dose calculation accuracy by at least 0.3% in heterogeneous phantoms. The FFTC method was approximately 40 times faster than the superposition method. However, compared with MC, mean absolute deviations were <3% for the FFTC method.

Intraoperative tracking of aortic valve plane.

The main objective of this work is to track the aortic valve plane in intra-operative fluoroscopic images in order to optimize and secure Transcatheter Aortic Valve Implantation (TAVI) procedure. This paper is focused on the issue of aortic valve calcifications tracking in fluoroscopic images. We propose a new method based on the Tracking-Learning-Detection approach, applied to the aortic valve calcifications in order to determine the position of the aortic valve plane in intra-operative TAVI images. This main contribution concerns the improvement of object detection by updating the recursive tracker in which all features are tracked jointly. The approach has been evaluated on four patient databases, providing an absolute mean displacement error less than 10 pixels (≈2mm). Its suitability for the TAVI procedure has been analyzed.

CT-scan images preprocessing and segmentation to improve bioprosthesis leaflets morphological analysis.

The visualization of bioprosthesis leaflet morphology might help to better understand the underlying mechanism of dysfunction in degenerated aortic bioprosthesis. Because today such visualization of bioprosthesis leaflet morphology is intricate to impossible with other imaging techniques, we hypothesized that the processing of multi-detector CT images would allow better visualization of the prosthetic valve leaflets after biological aortic valve replacement. The purpose of our study was to prospectively evaluate patients with a degenerated aortic bioprosthesis, waiting for reoperation, by using 64-slice CT to evaluate prosthetic leaflets morphology. A semi-automatic segmentation of pre-operative tomodensitometric images was conducted, using 2 different implementations of the region growing algorithm. Here we report all segmentation steps (selection of the region of interest, filtering, segmentation). Studied degenerated aortic bioprostheses were represented by two Carpentier-Edwards Supra Annular Valve (porcine leaflets), one Edwards Perimount (pericardial leaflets) and one Medtronic Mosaic (porcine leaflets). Both segmentation methods (Isotropic Region Growing and Stick Region Growing) allowed a semi-automatic segmentation with 3D reconstruction of all bioprosthetic components (stent, leaflets, degeneration/calcifications). Explanted bioprosthesis CT images were also processed and used as reference. Segmentation results were compared by means of quantitative criteria. Semi-automatic segmentation using region growing algorithm seems to provide an interesting approach for the morphological characterization of degenerated aortic bioprostheses. We believe that in the next future CT scan images segmentation may play an important role to better understand the mechanism of dysfunction in failing aortic bioprostheses. Moreover, bioprostheses 3D reconstructions could be integrated into preoperative planning tools to optimize valve-in-valve procedure.

Electromagnetic tracking for registration and navigation in endovascular aneurysm repair: a phantom study.

OBJECTIVE: To assess the feasibility of using an electromagnetic tracking for both registration and navigation in endovascular aneurysm repair. MATERIALS AND METHODS: A registration process was implemented to align computed tomography (CT) data and electromagnetic tracking data. Two abdominal aortic aneurysm (AAA) phantoms were used, a rigid plastic AAA model (phantom A) and a soft silicon AAA model (phantom B). A pre-procedural CT volume was acquired for each phantom. Intra-operative simulation was performed by placing each phantom in the magnetic field of the tracking device. Using a modified electromagnetic catheter, a set of three-dimensional positions was acquired in the phantom's aortic lumen. Pre-procedural CT images and intra-procedural tracked positions were registered. Four reference points were used to calculate the registration accuracy of phantom A. Three surgeons simulated catheterisation of the left renal artery with phantom B using only image-guided procedure software. RESULTS: The mean registration error was 1.3 mm (range 0.88-1.89). The median time for left renal catheterisation was 22 s (range 15-59). CONCLUSION: Registration of CT data and electromagnetic tracking data is feasible using catheter positions in the aorto-iliac structure as landmark. This navigation system could reduce X-ray exposure time and the use of contrast medium injections.

[Mid-ventilation position planning: optimal model for dose distribution in lung tumour]. / Planification selon la position moyenne du cycle respiratoire : modèle de planification optimale pour une distribution de dose dans les tumeurs pulmonaires.

PURPOSE: The dose distribution for lung tumour is estimated using a 3D-CT scan, and since a person breathes while the images are captured, the dose distribution doesn't reflect the reality. A 4D-CT scan integrates the motion of the tumour during breathing and, therefore, provides us with important information regarding tumour's motion in all directions, the motion volume (ITV) and the time-weighted average position (MVP). PATIENT AND METHODS: Based on these two concepts, we have estimated, for a lung carcinoma case a 3D dose distribution from a 3D-CT scan, and a 4D dose distribution from a 4-D CT scan. To this, we have applied a non-rigid registration to estimate the cumulative dose. RESULTS: Our study shows that the 4D dose estimation of the GTV is almost the same when made using MVP and ITV concepts, but sparring of the healthy lung is better done using the MPV model (MVP), as compared to the ITV model. This improvement of the therapeutic index allows, from a projection on the theoretical maximal dose to PTV (strictly restricted to doses for the lungs and the spinal cord), for an increase of about 11% on the total dose (maximal dose of 86 Gy for the ITV and 96 Gy for the MVP). CONCLUSION: Further studies with more patients are needed to confirm our data.

[From image-guided radiotherapy to dose-guided radiotherapy]. / De la radiothérapie guidée par l'image à la radiothérapie guidée par la dose.

PURPOSE: In case of tumour displacement, image-guided radiotherapy (IGRT) based on the use of cone beam CT (tomographie conique) allows replacing the tumour under the accelerator by rigid registration. Anatomical deformations require however replanning, involving an estimation of the cumulative dose, session after session. This is the objective of this study. PATIENTS AND METHODS: Two examples of arc-intensity modulated radiotherapy are presented: a case of prostate cancer (total dose=80 Gy) with tomographie conique (daily prostate registration) and one head and neck cancer (70 Gy). For the head and neck cancer, the patient had a weekly scanner allowing a dose distribution calculation. The cumulative dose was calculated per voxel on the planning CT after deformation of the dose distribution (with trilinear interpolation) following the transformation given by a non-rigid registration step (Demons registration method) from: either the tomographie conique (prostate), or the weekly CT. The cumulative dose was eventually compared with the planned dose. RESULTS: In cases of prostate irradiation, the "cumulative" dose corresponded to the planned dose to the prostate. At the last week of irradiation, it was above the planned dose for the rectum and bladder. The volume of rectal wall receiving more than 50 Gy (V50) was 20% at the planning and 26% at the end of treatment, increasing the risk of rectal toxicity (NTCP) of 14%. For the bladder wall, V50 were 73% and 82%, respectively. In head and neck, the "cumulative" dose to the parotid exceeded the planned dose (mean dose increasing from 46 Gy to 54 Gy) from the 5th week of irradiation on, suggesting the need for replanning within the first 5 weeks of radiotherapy. CONCLUSION: The deformable registration estimates the cumulative dose delivered in the different anatomical structures. Validation on digital and physical phantoms is however required before clinical evaluation.

[High dose for prostate irradiation with image guided radiotherapy: contribution of intensity modulation arctherapy]. / Haute dose dans la prostate par radiothérapie guidée par l'image: apport de l'arcthérapie avec modulation d'intensité du faisceau.

PURPOSE: To compare two Intensity Modulated Radiation Therapy (IMRT) techniques for prostate cancer: the Volumetric Modulated Arc Therapy (VMAT) and the "Step and Shoot" technique (S&S). MATERIALS AND METHODS: VMAT and S&S plans (RX 18MV) were created and compared (Wilcoxon test) for 10 patients. The dosimetric goal of both treatments was to deliver 46 Gy to the seminal vesicles and 80 Gy to the prostate, while respecting the dose constrains in the organs at risk of toxicity. For one patient, the two techniques were compared for dose painting and escalation in target volumes defined on MRI and registered thanks to intraprostatic fiducials. RESULTS: VMAT, compared to S&S, offered: an increase of the PTV2s (prostate) volume receiving 77 to 80 Gy and a decrease of V(82) and V(83); a decrease of V(4) to V(6), V(16) to V(23), and V(69) to V(73) for the rectal wall; a decrease of V(25) for the bladder wall; a decrease of V(21) to V(43) for the femoral heads; a decrease of V(26) to V(44) and V(72) to V(80) but an increase of V(1) to V(21) and V(49) to V(60) for the healthy tissues. The Conformal Index "COIN" was better with VMAT than S&S (0.60 to 0.66). The delivered MU were significantly reduced with VMAT (8% mean) as well as the delivery time (4 min to 1.5 min). VMAT allowed delivering theorically 90Gy in the peripheral zone and 100 Gy in the tumor. CONCLUSION: In case of prostate irradiation, VMAT shows improvement compared with S&S. In particular, organs at risk are better spared, the delivery time is shortened and the number of delivered UM is decreased.

[Quantification of the volumetric benefit of image-guided radiotherapy (IGRT) in prostate cancer: margins and presence probability map]. / Bénéfice volumétrique de la radiothérapie guidée par l'image dans les cancers prostatiques : marges et cartographies de probabilité de présence.

PURPOSE: To quantify the prostate and seminal vesicles (SV) anatomic variations in order to choose appropriate margins including intrapelvic anatomic variations. To quantify volumetric benefit of image-guided radiotherapy (IGRT). PATIENTS AND METHODS: Twenty patients, receiving a total dose of 70 Gy in the prostate, had a planning CT scan and eight weekly CT scans during treatment. Prostate and SV were manually contoured. Each weekly CT scan was registered to the planning CT scan according to three modalities: radiopaque skin marks, pelvis bone or prostate. For each patient, prostate and SV displacements were quantified. 3D maps of prostate and SV presence probability were established. Volumes including minimal presence probabilities were compared between the three modalities of registration. RESULTS: For the prostate intrapelvic displacements, systematic and random variations and maximal displacements for the entire population were: 5mm, 2.7 mm and 16.5mm in anteroposterior axis; 2.7 mm, 2.4mm and 11.4mm in superoinferior axis and 0.5mm, 0.8mm and 3.3mm laterally. Margins according to van Herk recipe (to cover the prostate for 90% of the patients with the 95% isodose) were: 8mm, 8.3mm and 1.9 mm, respectively. The 100% prostate presence probability volumes correspond to 37%, 50% and 61% according to the registration modality. For the SV, these volumes correspond to 8%, 14% and 18% of the SV volume. CONCLUSIONS: Without IGRT, 5mm prostate posterior margins are insufficient and should be at least 8mm, to account for intrapelvic anatomic variations. Prostate registration almost doubles the 100% presence probability volume compared to skin registration. Deformation of SV will require either to increase dramatically margins (simple) or new planning (not realistic).

Tool/tissues interaction modeling for transluminal angioplasty simulation.

In this paper, a simulation environment is described for balloon dilation during percutaneous transluminal angioplasty. It means simulating tool/tissues interactions involved in the inflation of a balloon by considering patient specific data. In this context, three main behaviors have been identified: soft tissues, crush completely under the effect of the balloon, calcified plaques, do not admit any deformation but could move in deformable structures and blood vessel wall and organs, try to find their original forms. A deformable soft tissue model is proposed, based on the Enhanced ChainMail method to take into account tissues deformation during dilatation. We improved the original ChainMail method with a "forbidden zone" step to facilitate tool/tissues interactions. The simulation was implemented using five key steps: 1) initialization of balloon parameters; 2) definition of the data structure; 3) dilatation of the balloon and displacement approximation; 4) final position estimation by an elastic relaxation; and 5) interpolation step for visualization. Preliminary results obtained from patient CT data are reported.

Depth-map-based scene analysis for active navigation in virtual angioscopy.

This paper presents a new approach dealing with virtual exploratory navigation inside vascular structures. It is based on the notion of active vision in which only visual perception drives the motion of the virtual angioscope. The proposed fly-through approach does not require a premodeling of the volume dataset or an interactive control of the virtual sensor during the fly-through. Active navigation combines the on-line computation of the scene view and its analysis, to automatically define the three-dimensional sensor path. The navigation environment and the camera-like model are first sketched. The basic stages of the active navigation framework are then described: the virtual image computation (based on ray casting), the scene analysis process (using depth map), the navigation strategy, and the virtual path estimation. Experimental results obtained from phantom model and patient computed tomography data are finally reported.

[Glossary of terms used by radiologists in image processing]. / Lexique des termes utilisés dans le traitement des images à l'usage des médecins radiologues.

We give the definition of 166 words used in image processing. Adaptivity, aliazing, analog-digital converter, analysis, approximation, arc, artifact, artificial intelligence, attribute, autocorrelation, bandwidth, boundary, brightness, calibration, class, classification, classify, centre, cluster, coding, color, compression, contrast, connectivity, convolution, correlation, data base, decision, decomposition, deconvolution, deduction, descriptor, detection, digitization, dilation, discontinuity, discretization, discrimination, disparity, display, distance, distorsion, distribution dynamic, edge, energy, enhancement, entropy, erosion, estimation, event, extrapolation, feature, file, filter, filter floaters, fitting, Fourier transform, frequency, fusion, fuzzy, Gaussian, gradient, graph, gray level, group, growing, histogram, Hough transform, Houndsfield, image, impulse response, inertia, intensity, interpolation, interpretation, invariance, isotropy, iterative, JPEG, knowledge base, label, laplacian, learning, least squares, likelihood, matching, Markov field, mask, matching, mathematical morphology, merge (to), MIP, median, minimization, model, moiré, moment, MPEG, neural network, neuron, node, noise, norm, normal, operator, optical system, optimization, orthogonal, parametric, pattern recognition, periodicity, photometry, pixel, polygon, polynomial, prediction, pulsation, pyramidal, quantization, raster, reconstruction, recursive, region, rendering, representation space, resolution, restoration, robustness, ROC, thinning, transform, sampling, saturation, scene analysis, segmentation, separable function, sequential, smoothing, spline, split (to), shape, threshold, tree, signal, speckle, spectrum, spline, stationarity, statistical, stochastic, structuring element, support, syntaxic, synthesis, texture, truncation, variance, vision, voxel, windowing.