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1.
Phys Med Biol ; 68(14)2023 07 05.
Article in English | MEDLINE | ID: mdl-37321258

ABSTRACT

Objective. Respiration negatively affects the outcome of a radiation therapy treatment, with potentially severe effects especially in particle therapy (PT). If compensation strategies are not applied, accuracy cannot be achieved. To support the clinical practice based on 4D computed tomography (CT), 4D magnetic resonance imaging (MRI) acquisitions can be exploited. The purpose of this study was to validate a method for virtual 4DCT generation from 4DMRI data for lung cancers on a porcine lung phantom, and to apply it to lung cancer patients in PT.Approach. Deformable image registration was used to register each respiratory phase of the 4DMRI to a reference phase. Then, a static 3DCT was registered to this reference MR image set, and the virtual 4DCT was generated by warping the registered CT according to previously obtained deformation fields. The method was validated on a physical phantom for which a ground truth 4DCT was available and tested on lung tumor patients, treated with gated PT at end-exhale, by comparing the virtual 4DCT with a re-evaluation 4DCT. The geometric and dosimetric evaluation was performed for both proton and carbon ion treatment plans.Main results. The phantom validation exhibited a geometrical accuracy within the maximum resolution of the MRI and mean dose deviations, with respect to the prescription dose, up to 3.2% for targetD95%, with a mean gamma pass rate of 98%. For patients, the virtual and re-evaluation 4DCTs showed good correspondence, with errors on targetD95%up to 2% within the gating window. For one patient, dose variations up to 10% at end-exhale were observed due to relevant inter-fraction anatomo-pathological changes that occurred between the planning and re-evaluation CTs.Significance. Results obtained on phantom data showed that the virtual 4DCT method was accurate, allowing its application on patient data for testing within a clinical scenario.


Subject(s)
Four-Dimensional Computed Tomography , Lung Neoplasms , Animals , Swine , Four-Dimensional Computed Tomography/methods , Radiotherapy Planning, Computer-Assisted/methods , Lung Neoplasms/diagnostic imaging , Lung Neoplasms/radiotherapy , Respiration , Radiometry/methods
2.
Annu Int Conf IEEE Eng Med Biol Soc ; 2021: 3761-3764, 2021 11.
Article in English | MEDLINE | ID: mdl-34892054

ABSTRACT

Skull-base chordoma (SBC) is a rare tumour whose molecular and radiological characteristics are still being investigated. In neuro-oncology microstructural imaging techniques, like diffusion-weighted MRI (DW-MRI), have been widely investigated, with the apparent diffusion coefficient (ADC) being one of the most used DW-MRI parameters due to its ease of acquisition and computation. ADC is a potential biomarker without a clear link to microstructure. The aim of this work was to derive microstructural information from conventional ADC, showing its potential for the characterisation of skull-base chordomas. Sixteen patients affected by SBC, who underwent conventional DW-MRI were retrospectively selected. From mono-exponential fits of DW-MRI, ADC maps were estimated using different sets of b-values. DW-MRI signals were simulated from synthetic substrates , which mimic the cellular packing of a tumour tissue with well-defined microstructural features. Starting from a published method, an error-driven procedure was evaluated to improve the estimates of microstructural parameters obtained through the simulated signals. A quantitative description of the tumour microstructure was then obtained from the DW-MRI images. This allowed successfully differentiating patients according to histologically-verified cell proliferation information.Clinical Relevance - The impact on cancer management derives from the expected improvement of radiation treatment quality tailored to a patient-specific non-invasive description of tumour microstructure.


Subject(s)
Chordoma , Chordoma/diagnostic imaging , Diffusion Magnetic Resonance Imaging , Humans , Magnetic Resonance Imaging , Retrospective Studies , Skull
3.
Phys Med ; 90: 123-133, 2021 Oct.
Article in English | MEDLINE | ID: mdl-34628271

ABSTRACT

PURPOSE: Carbon ion radiotherapy (CIRT) is sensitive to anatomical density variations. We examined the dosimetric effect of variable intestinal filling condition during CIRT to ten sacral chordoma patients. METHODS: For each patient, eight virtual computed tomography scans (vCTs) were generated by varying the density distribution within the rectum and the sigmoid in the planning computed tomography (pCT) with a density override approach mimicking a heterogeneous combination of gas and feces. Totally full and empty intestinal preparations were modelled. In addition, five different intestinal filling conditions were modelled by a mixed density pattern derived from two combined and weighted Gaussian distributions simulating gas and feces respectively. Finally, a patient-specific mixing proportion was estimated by evaluating the daily amount of gas detected in the cone beam computed tomography (CBCT). Dose distribution was recalculated on each vCT and dose volume histograms (DVHs) were examined. RESULTS: No target coverage degradation was observed at different vCTs. Rectum and sigma dose degradation ranged respectively between: [-6.7; 21.6]GyE and [-0.7; 15.4]GyE for D50%; [-377.4; 1197.9] and [-95.2; 1027.5] for AUC; [-1.2; 10.7]GyE and [-2.6; 21.5]GyE for D1%. CONCLUSIONS: Variation of intestinal density can greatly influence the penetration depth of charged particle and might compromise dose distribution. In particular cases, with large clinical target volume in very close proximity to rectum and sigmoid colon, it is appropriate to evaluate the amount of gas present in the daily CBCT images even if it is totally included in the reference planning structures.


Subject(s)
Chordoma , Heavy Ion Radiotherapy , Chordoma/diagnostic imaging , Chordoma/radiotherapy , Colon, Sigmoid/diagnostic imaging , Cone-Beam Computed Tomography , Humans , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted , Rectum/diagnostic imaging
5.
Phys Med ; 82: 228-239, 2021 Feb.
Article in English | MEDLINE | ID: mdl-33657472

ABSTRACT

An Eye Tracking System (ETS) is used at CNAO for providing a stable and reproducible ocular proton therapy (OPT) set-up, featuring a fixation light (FL) and monitoring stereo-cameras embedded in a rigid case. The aim of this work is to propose an ETS set-up simulation algorithm, that automatically provides the FL positioning in space, according to patient-specific gaze direction and avoiding interferences with patient, beam and collimator. Two configurations are provided: one in the CT room for acquiring images required for treatment planning with the patient lying on a couch, and one related to the treatment room with the patient sitting in front of the beam. Algorithm validation was performed reproducing ETS simulation (CT) and treatment (room) set-up for 30 patients previously treated at CNAO. The positioning accuracy of the device was quantified through a set of 14 control points applied to the ETS case and localizable both in the CT volume and in room X-ray images. Differences between the position of ETS reference points estimated by the algorithm and those measured by imaging systems are reported. The corresponding gaze direction deviation is on average 0.2° polar and 0.3° azimuth for positioning in CT room and 0.1° polar and 0.4° azimuth in the treatment room. The simulation algorithm was embedded in a clinically usable software application, which we assessed as capable of ensuring ETS positioning with an average accuracy of 2 mm in CT room and 1.5 mm in treatment room, corresponding to gaze direction deviations consistently lower than 1°.


Subject(s)
Proton Therapy , Algorithms , Eye , Humans , Radiotherapy Planning, Computer-Assisted , Software
6.
Med Phys ; 48(4): 1646-1660, 2021 Apr.
Article in English | MEDLINE | ID: mdl-33220073

ABSTRACT

PURPOSE: Spatial distortions in magnetic resonance imaging (MRI) are mainly caused by inhomogeneities of the static magnetic field, nonlinearities in the applied gradients, and tissue-specific magnetic susceptibility variations. These factors may significantly alter the geometrical accuracy of the reconstructed MR image, thus questioning the reliability of MRI for guidance in image-guided radiation therapy. In this work, we quantified MRI spatial distortions and created a quantitative model where different sources of distortions can be separated. The generated model was then integrated into a four-dimensional (4D) computational phantom for simulation studies in MRI-guided radiation therapy at extra-cranial sites. METHODS: A geometrical spatial distortion phantom was designed in four modules embedding laser-cut PMMA grids, providing 3520 landmarks in a field of view of (345 × 260 × 480) mm3 . The construction accuracy of the phantom was verified experimentally. Two fast MRI sequences for extra-cranial imaging at 1.5 T were investigated, considering axial slices acquired with online distortion correction, in order to mimic practical use in MRI-guided radiotherapy. Distortions were separated into their sources by acquisition of images with gradient polarity reversal and dedicated susceptibility calculations. Such a separation yielded a quantitative spatial distortion model to be used for MR imaging simulations. Finally, the obtained spatial distortion model was embedded into an anthropomorphic 4D computational phantom, providing registered virtual CT/MR images where spatial distortions in MRI acquisition can be simulated. RESULTS: The manufacturing accuracy of the geometrical distortion phantom was quantified to be within 0.2 mm in the grid planes and 0.5 mm in depth, including thickness variations and bending effects of individual grids. Residual spatial distortions after MRI distortion correction were strongly influenced by the applied correction mode, with larger effects in the trans-axial direction. In the axial plane, gradient nonlinearities caused the main distortions, with values up to 3 mm in a 1.5 T magnet, whereas static field and susceptibility effects were below 1 mm. The integration in the 4D anthropomorphic computational phantom highlighted that deformations can be severe in the region of the thoracic diaphragm, especially when using axial imaging with 2D distortion correction. Adaptation of the phantom based on patient-specific measurements was also verified, aiming at increased realism in the simulation. CONCLUSIONS: The implemented framework provides an integrated approach for MRI spatial distortion modeling, where different sources of distortion can be quantified in time-dependent geometries. The computational phantom represents a valuable platform to study motion management strategies in extra-cranial MRI-guided radiotherapy, where the effects of spatial distortions can be modeled on synthetic images in a virtual environment.


Subject(s)
Radiotherapy, Image-Guided , Computer Simulation , Humans , Magnetic Resonance Imaging , Phantoms, Imaging , Reproducibility of Results
7.
Phys Med ; 69: 164-169, 2020 Jan.
Article in English | MEDLINE | ID: mdl-31918368

ABSTRACT

PURPOSE: To devise a novel Spatial Normalization framework for Voxel-based analysis (VBA) in brain radiotherapy. VBAs rely on accurate spatial normalization of different patients' planning CTs on a common coordinate system (CCS). The cerebral anatomy, well characterized by MRI, shows instead poor contrast in CT, resulting in potential inaccuracies in VBAs based on CT alone. METHODS: We analyzed 50 meningioma patients treated with proton-therapy, undergoing planning CT and T1-weighted (T1w) MRI. The spatial normalization pipeline based on MR and CT images consisted in: intra-patient registration of CT to T1w, inter-patient registration of T1w to MNI space chosen as CCS, doses propagation to MNI. The registration quality was compared with that obtained by Statistical Parametric Mapping software (SPM), used as benchmark. To evaluate the accuracy of dose normalization, the dose organ overlap (DOO) score was computed on gray matter, white matter and cerebrospinal fluid before and after normalization. In addition, the trends in the DOOs distribution were investigated by means of cluster analysis. RESULTS: The registration quality was higher for the proposed method compared to SPM (p < 0.001). The DOO scores showed a significant improvement after normalization (p < 0.001). The cluster analysis highlighted 2 clusters, with one of them including the majority of data and exhibiting acceptable DOOs. CONCLUSIONS: Our study presents a robust tool for spatial normalization, specifically tailored for brain dose VBAs. Furthermore, the cluster analysis provides a formal criterion for patient exclusion in case of non-acceptable normalization results. The implemented framework lays the groundwork for future reliable VBAs in brain irradiation studies.


Subject(s)
Brain Neoplasms/diagnostic imaging , Brain Neoplasms/radiotherapy , Brain/diagnostic imaging , Brain/radiation effects , Meningioma/diagnostic imaging , Meningioma/radiotherapy , Adolescent , Adult , Aged , Cluster Analysis , Contrast Media/chemistry , Humans , Image Processing, Computer-Assisted , Magnetic Resonance Imaging , Middle Aged , Models, Statistical , Radiometry , Reproducibility of Results , Software , Tomography, X-Ray Computed , Young Adult
8.
Phys Med Biol ; 64(20): 205006, 2019 10 10.
Article in English | MEDLINE | ID: mdl-31519018

ABSTRACT

Magnetic-resonance linear-accelerator (MR-LINAC) systems integrating in-room magnetic-resonance-imaging (MRI) guidance are a currently emerging technology. Such systems address the need to provide frequent imaging at optimal soft-tissue contrast for treatment guidance. However, the use of MRI-guidance in radiotherapy should address imaging-related spatial distortions, which may hinder accurate geometrical characterization of the treatment site. Since spatial encoding relies on well-defined magnetic fields, accurate modeling of the magnetic field alterations due to [Formula: see text]-inhomogeneities, gradient nonlinearities, and susceptibilities is needed. In this work, the modeling of susceptibility induced distortions is considered. Dedicated susceptibility measurements are reported, aiming at extending the characterization of different tissues for MRI-guided extra-cranial radiotherapy applications. A digital 4D anthropomorphic phantom, providing time-resolved anatomical changes due to breathing, is exploited as reference anatomy to quantify spatial distortions due to variations in tissue susceptibility. Sub-millimeter values can be attributed to susceptibility-induced distortions, with maximum values up to 2.3 mm at a gradient strength of 5 mT m-1. Improvements in susceptibility simulation for extra-cranial sites are shown when including specifically the contributions from lung, liver and muscular tissues.


Subject(s)
Magnetic Resonance Imaging/methods , Magnetic Resonance Imaging/standards , Phantoms, Imaging , Radiotherapy Planning, Computer-Assisted/methods , Radiotherapy, Image-Guided/methods , Soft Tissue Neoplasms/radiotherapy , Algorithms , Animals , Liver/radiation effects , Lung/radiation effects , Magnetic Fields , Muscle, Skeletal/radiation effects , Particle Accelerators , Respiration , Swine
9.
Phys Med Biol ; 64(18): 185013, 2019 09 19.
Article in English | MEDLINE | ID: mdl-31323645

ABSTRACT

MRI-treatment units enable 2D cine-MRI centred in the tumour for motion detection in radiotherapy, but they lack 3D information due to spatio-temporal limits. To derive time-resolved 3D information, different approaches have been proposed in the literature, but a rigorous comparison among these strategies has not yet been performed. The goal of this study is to quantitatively investigate five published strategies that derive time-resolved volumetric MRI in MRI-guided radiotherapy: Propagation, out-of-plane motion compensation, Fayad model, ROI-based model and Stemkens model. Comparisons were performed using an MRI digital phantom generated with six different patient-derived motion signals and tumour-shapes. An average 4D cycle was generated as well as 2D cine-MRI data with corresponding 3D in-room ground truth. Quantitative analysis was performed by comparing the estimated 3D volume to the ground truth available for each 2D cine-MRI sample. A grouped patient statistical analysis was performed to evaluate the performance of the selected methods, in case of tumour tracking or motion estimation of the whole anatomy. Analyses were also performed based on patient characteristics. Quantitative ranking of the investigated methods highlighted that Propagation and ROI-based model strategies achieved an overall median tumour centre of mass 3D distance from the ground truth of 1.1 mm and 1.3 mm, respectively, and a diaphragm distance below 1.6 mm. Higher errors and variabilities were instead obtained for other methods, which lack the ability to compensate for in-room variations and to account for regional changes. These results were especially evident when further analysing patient characteristics, where errors above 2 mm/5 mm in tumour/diaphragm were found for more irregular breathing patterns in case of out-of-plane motion compensation, Fayad and Stemkens models. These findings suggest the potential of the proposed in silico framework to develop and compare strategies to estimate time-resolved 3DMRI in MRI-guided radiotherapy.


Subject(s)
Lung Neoplasms/diagnostic imaging , Lung Neoplasms/radiotherapy , Lung/diagnostic imaging , Magnetic Resonance Imaging, Cine , Radiotherapy, Image-Guided/methods , Computer Simulation , Humans , Motion , Phantoms, Imaging , Reproducibility of Results , Respiration
10.
Phys Med Biol ; 63(22): 22TR03, 2018 11 20.
Article in English | MEDLINE | ID: mdl-30457121

ABSTRACT

High precision conformal radiotherapy requires sophisticated imaging techniques to aid in target localisation for planning and treatment, particularly when organ motion due to respiration is involved. X-ray based imaging is a well-established standard for radiotherapy treatments. Over the last few years, the ability of magnetic resonance imaging (MRI) to provide radiation-free images with high-resolution and superb soft tissue contrast has highlighted the potential of this imaging modality for radiotherapy treatment planning and motion management. In addition, these advantageous properties motivated several recent developments towards combined MRI radiation therapy treatment units, enabling in-room MRI-guidance and treatment adaptation. The aim of this review is to provide an overview of the state-of-the-art in MRI-based image guidance for organ motion management in external beam radiotherapy. Methodological aspects of MRI for organ motion management are reviewed and their application in treatment planning, in-room guidance and adaptive radiotherapy described. Finally, a roadmap for an optimal use of MRI-guidance is highlighted and future challenges are discussed.


Subject(s)
Magnetic Resonance Imaging , Movement , Radiotherapy, Image-Guided/methods , Humans , Neoplasms/diagnostic imaging , Neoplasms/physiopathology , Neoplasms/radiotherapy , Radiotherapy Planning, Computer-Assisted
11.
Eur J Dent Educ ; 22 Suppl 1: 3-9, 2018 Mar.
Article in English | MEDLINE | ID: mdl-29601680

ABSTRACT

The constant change of information and technology advancement as well as the impact of social media has radically changed the world and education and, in particular, the needs of students, organisations and disadvantaged communities who share the aim of training and providing quality healthcare services. Dental organisations and education centres around the world have recognised the importance of networking in delivering effective education to students, healthcare professionals and communities. Networking is one way to meet the challenges of delivering healthcare education and services. This can be achieved by sharing of resources, expertise, knowledge and experience to benefit all the stakeholders in healthcare delivery. The joint ADEE/ADEA Meeting in London on 8-9 May 2017 has facilitated discussions amongst dental educators from all over the world during a workshop on "Global Networking: the how and why for dental educators." The aim of this workshop was to determine how can dental educators worldwide network to share ideas, experience, expertise and resources to improve both the curricula and the teaching and learning environment. A pre-conference survey was designed and implemented to identify the domains of interest and needs of participants. A structured questionnaire was administered, and this information was used to guide discussions on three main themes: curricula, faculty development and mobility of faculty and students. Four questions were then defined to help group leaders to frame discussions in the four working groups. The four groups engaged in parallel discussions, with the ideas recorded and collated by group leaders, which later served for the thematic analysis across the groups to draw the key points discussed. Overall, a great desire and potential to create a global networking to share and gain support and expertise at individual and organisational level was apparent and the working group has proposed an action plan, acknowledging that it requires great planning, effort and commitment.


Subject(s)
Education, Dental/organization & administration , Interinstitutional Relations , Societies, Dental/organization & administration , Curriculum , Europe , Faculty, Dental , Humans , United States
12.
Eur J Dent Educ ; 21 Suppl 1: 28-35, 2017 Dec.
Article in English | MEDLINE | ID: mdl-29205776

ABSTRACT

It is often the case that good teachers just "intuitively" know how to teach. Whilst that may be true, there is now a greater need to understand the various processes that underpin both the ways in which a curriculum is delivered, and the way in which the students engage with learning; curricula need to be designed to meet the changing needs of our new graduates, providing new, and robust learning opportunities, and be communicated effectively to both staff and students. The aim of this document is to draw together robust and contemporaneous methods of teaching, learning and assessment that help to overcome some of the more traditional barriers within dental undergraduate programmes. The methods have been chosen to map specifically to The Graduating European Dentist, and should be considered in parallel with the benchmarking process that educators and institutions employ locally.


Subject(s)
Education, Dental/standards , Educational Measurement , Learning , Teaching , Clinical Competence , Competency-Based Education , Curriculum , Education, Dental/organization & administration , Europe , Feedback , Humans , Models, Educational
13.
Br Dent J ; 222(10): 809-817, 2017 May 26.
Article in English | MEDLINE | ID: mdl-28546591

ABSTRACT

In Italy healthcare is provided for all Italian citizens and residents and it is delivered mainly by public providers, with some private or private-public entities. Italy's public healthcare system - the Servizio Sanitario Nazionale (SSN) - is organised by the Ministry of Health and administered on a devolved regional basis. It is financed by general taxation that provides universal coverage, largely free of charge at the point of service. The central government establishes the basic national health benefits package, which must be uniformly provided throughout the country, through services guaranteed under the NHS provision called LEA - (Livelli Essenziali di Assistenza [Essential Level of Assistance]) and allocates national funds to the regions. The regions, through their regional health departments, are responsible for organising, administering and delivering primary, secondary and tertiary healthcare services as well as preventive and health promotion services. Regions are allowed a large degree of autonomy in how they perform this role and regarding decisions about the local structure of the system. Complementary and supplementary private health insurance is also available. However, as in most other Mediterranean European countries, in Italy oral healthcare is mainly provided under private arrangements. The public healthcare system provides only 5-8% of oral healthcare services and this percentage varies from region to region. Oral healthcare is included in the Legislation on Essential levels of care (LEAs) for specific populations such as children, vulnerable people (medically compromised and those on low income) and individuals who need oral healthcare in some urgent/emergency cases. For other people, oral healthcare is generally not covered. Apart from the national benefits package, regions may also carry out their own initiatives autonomously, but must finance these themselves. The number of dentists working in Italy has grown rapidly in the last few years. In December 2014, there were 59,324 practicing dentists with a ratio of one dentist every 1025 inhabitants, about 90,000 dental chair-side assistants, about 26,000 dental technicians and about 4000 dental hygienists. To enrol in an Italian dental school a student must pass a competitive national entrance examination after obtaining a high school leaving certificate. For entry in the 2015-2016 cycle, there were 792 places for dentistry. In comparison with dental schools in other EU member states, the number of dental students per school is low with an average of 20 students per year, per school and a range of 10 to 60. The aims of this paper are to give a brief description of the organisation of healthcare in Italy, to outline the system for the provision of oral healthcare in Italy and to explain and discuss the latest changes.


Subject(s)
Delivery of Health Care/organization & administration , Adolescent , Adult , Aged , Child , Child, Preschool , Dental Care/organization & administration , Dental Care/statistics & numerical data , Dental Caries/epidemiology , European Union/organization & administration , Health Expenditures , Health Services Accessibility , Humans , Insurance, Dental , Italy/epidemiology , Middle Aged , National Health Programs/organization & administration , Quality of Health Care , Young Adult
14.
Orthod Craniofac Res ; 20(2): 119-125, 2017 May.
Article in English | MEDLINE | ID: mdl-28414874

ABSTRACT

INTRODUCTION: Of the variables used by in vitro studies of resistance to sliding (RS) in orthodontics, sliding velocity (SV) of the wire is often the one farthest from its clinical counterpart. We investigated whether velocity influences the RS at values approximating the orthodontic movement. METHODS: A SS self-ligating bracket with a NiTi clip was fixed onto a custom-made model. Different shaped orthodontic SS wires of four sizes and two types (round, 0.020″ and 0.022″; rectangular, 0.016″×0.022″ and 0.017″×0.025″) were tested using an Instron® testing machine. Wires were pulled at four velocities (1×10-2  mm/s, 1×10-3  mm/s, 1×10-4  mm/s, 1×10-5  mm/s). Shapiro-Wilk test was used to evaluate the normal distribution of the data; two-way ANOVA was performed to compare means in the RS with wire characteristics and SV. Significance level was set at P<.05. RESULTS: RS was higher for rectangular wires, and for those with larger diameters. Lower SV was associated with lower RS, with wire type and size having an interaction effect. The RS relatively to SV can be represented as: RS ∝ α[ln(SV)]+ß, where α and ß are constants. CONCLUSIONS: At very low SV and low normal forces, SV influences the RS of SS archwires in orthodontic brackets, and the proportionality is logarithmic. Although respecting these parameters in vitro is challenging, quantitative evaluations of RS should be carried out at clinically relevant velocities if aiming at translational application in the clinical scenario.


Subject(s)
Orthodontic Appliance Design , Orthodontic Brackets , Orthodontic Wires , Dental Stress Analysis , Friction , In Vitro Techniques , Materials Testing , Stainless Steel
15.
Phys Med Biol ; 61(2): 872-87, 2016 Jan 21.
Article in English | MEDLINE | ID: mdl-26740517

ABSTRACT

In-room cine-MRI guidance can provide non-invasive target localization during radiotherapy treatment. However, in order to cope with finite imaging frequency and system latencies between target localization and dose delivery, tumour motion prediction is required. This work proposes a framework for motion prediction dedicated to cine-MRI guidance, aiming at quantifying the geometric uncertainties introduced by this process for both tumour tracking and beam gating. The tumour position, identified through scale invariant features detected in cine-MRI slices, is estimated at high-frequency (25 Hz) using three independent predictors, one for each anatomical coordinate. Linear extrapolation, auto-regressive and support vector machine algorithms are compared against systems that use no prediction or surrogate-based motion estimation. Geometric uncertainties are reported as a function of image acquisition period and system latency. Average results show that the tracking error RMS can be decreased down to a [0.2; 1.2] mm range, for acquisition periods between 250 and 750 ms and system latencies between 50 and 300 ms. Except for the linear extrapolator, tracking and gating prediction errors were, on average, lower than those measured for surrogate-based motion estimation. This finding suggests that cine-MRI guidance, combined with appropriate prediction algorithms, could relevantly decrease geometric uncertainties in motion compensated treatments.


Subject(s)
Magnetic Resonance Imaging, Cine/methods , Motion , Radiotherapy, Computer-Assisted/methods , Regression Analysis , Support Vector Machine
16.
Gynecol Obstet Fertil ; 43(4): 271-7, 2015 Apr.
Article in French | MEDLINE | ID: mdl-25819393

ABSTRACT

OBJECTIVES: The first aim of this study was to evaluate the access of independent midwives to the technical facilities of a level-1 maternity hospital, with a follow-up of 2 years. The second aim was to evaluate the transfer of clinical responsibility, when a patient stops being managed by the independent midwife to be taken care of by the hospital team. PATIENTS AND METHODS: A retrospective study including 51 patients. Analysis of maternal and perinatal data. RESULTS: Of the 51 births, there were 42 vaginal deliveries without intervention (82.35%), 3 instrumental deliveries (5.88%), 6 caesarean sections (11.76%). The midwife-led care was completed in 70.59% of cases. The rate of transfer of clinical responsibility during labor was 25.49%. We conducted a neonatal transfer due to a respiratory distress syndrome. DISCUSSION AND CONCLUSION: The access to technical support appears as an opportunity for independent midwives to establish a special relationship with their patients. However, this device preserves the possibility of a traditional hospital care when needed. This way, access to the technical support is a safe alternative that has the consent of the users (patients and midwives) as well as of the entire hospital team. Moreover, such device allowed an increase of 5% per year of our obstetrical activity with an estimated increase of 10% per year.


Subject(s)
Hospitals, Maternity , Medical Staff Privileges , Midwifery , Adult , Cesarean Section , Delivery, Obstetric , Female , Humans , Obstetrics , Personnel, Hospital , Pregnancy , Retrospective Studies
17.
Br J Dermatol ; 170(2): 382-91, 2014 Feb.
Article in English | MEDLINE | ID: mdl-24024734

ABSTRACT

BACKGROUND: Sun exposure is responsible for long-term clinical skin changes such as photoageing, photodamage and photocancers. Ultraviolet (UV)A wavelengths stimulate the production of reactive oxygen species (ROS) that may contribute to photoageing. To protect against oxidative stress, skin cells have developed several defence systems, including ROS and metal ion scavengers and a battery of detoxifying, haem-degrading and repair enzymes. Melatonin's antioxidant activity is the result of three different but complementary actions: (i) a direct action due to its ability to act as a free radical scavenger; (ii) an indirect action that is a consequence of melatonin's ability to reduce free radical generation (radical avoidance); and (iii) its ability to upregulate antioxidant enzymes. OBJECTIVES: In this study, we focused our attention on the prevention of photodamage, choosing melatonin as an antioxidant agent. METHODS: In the present study we analysed the effects of pretreatment of murine fibroblasts cells (NIH3T3) with melatonin (1 mmol L(-1) ) followed by UVA irradiation (15 J cm(-2) ). Thereafter, changes in components of the extracellular matrix and in some antioxidant enzymes (inducible and constitutive haem oxygenase) were evaluated. RESULTS: We observed that UVA radiation caused altered expression of extracellular matrix proteins and induced the expression of inducible haem oxygenase. This increase was not sufficient to protect the cells from damage. Instead, melatonin pretreatment led to increased expression of haem-degrading enzymes and suppression of UVA-induced photodamage. CONCLUSIONS: These results suggest that melatonin, as a modifier of the dermatoendocrine system, may have utility in reducing the effects of skin ageing.


Subject(s)
Antioxidants/pharmacology , Fibroblasts/radiation effects , Melatonin/pharmacology , Ultraviolet Rays/adverse effects , Animals , Caspase 3/metabolism , Collagen Type I/metabolism , Collagen Type II/metabolism , Cytochromes c/metabolism , Fibroblasts/metabolism , Fibronectins/metabolism , Fluorescent Antibody Technique , Heme Oxygenase-1/metabolism , Mice , NIH 3T3 Cells , Skin/cytology , Skin/metabolism , Skin/radiation effects , Transforming Growth Factor beta1/metabolism
19.
Article in English | MEDLINE | ID: mdl-23367428

ABSTRACT

We propose the use of Scale Invariant Feature Transform (SIFT) as a method able to extract stable landmarks from 4D images and to quantify internal motion. We present a preliminary validation of the SIFT method relying on expert user identification of landmarks and then apply it to 4D lung CT and liver MRI data. Results demonstrate SIFT capabilities as an operator-independent feature tracking method.


Subject(s)
Image Interpretation, Computer-Assisted/methods , Liver/pathology , Lung/diagnostic imaging , Magnetic Resonance Imaging/methods , Pattern Recognition, Automated/methods , Tomography, X-Ray Computed/methods , Algorithms , Computer Simulation , Humans , Models, Statistical , Movement , Normal Distribution , Software , Time Factors
20.
Minerva Stomatol ; 59(11-12): 653-61, 2010.
Article in English, Italian | MEDLINE | ID: mdl-21217630

ABSTRACT

The pycnodysostosis is a genetically determined, autosomal recessive osteosclerosis, due to deficiency of cathepsin K. It is characterized by short stature, massive skull, hands and feet with short terminal phalanges, dysplastic nails. Oral and maxillofacial manifestations include hypoplasia of the mandible and maxillary sinus, obtuse mandibular gonial angle deciduous teeth and permanent impacts, or malposition, frequent overcrowding, periodontal lesions. Bone sclerosis is already detectable in X-rays during childhood, often present open fontanelles and sutures, wormian bones; frequent pathological fractures. This article presents the case of a male patient, Caucasian, age 9 years and 11 months suffer from pycnodysostosis, mutation of the gene in heterozygotes p.R241X, already followed at the Pediatric Endocrinology Clinic of the Spedali Civili of Brescia. After evaluation at the Department of Maxillofacial Surgery of the Spedali Civili of Brescia, for surgical reasons required a cone beam computed tomography (CBCT) scanner with NewTom 3G, was presented to our observation at the Department of Orthodontics of the Dental Clinic of the University of Brescia. CBCT findings including detailed information about the anatomy of the upper and lower jaw, dental elements, their relationship with the surrounding anatomical structures and the spatial position. The only radiographic examination currently available that obtains 3D images and the volume of the life-size area, without exposing patient to dose of radiation from a classic multi-layer CT is CBCT that, even through the 3D reconstructions with dedicated programs can make a correct diagnosis, prognosis and treatment in patients with maxillofacial dysmorphism. This examination allows to obtain images from around the skull that permit a complete orthodontic diagnosis, not only restricted to the area of surgical interest, taking into account the reports of the dental arches to each other and with surrounding structures.


Subject(s)
Cone-Beam Computed Tomography , Pycnodysostosis/diagnostic imaging , Child , Humans , Male , Orthodontics
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