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Salpadimos N, Karfopoulos K, Seimenis I, Potiriadis C, Carinou E, Housiadas C. Risk assessment for the optimization of the grid of a telemetric network monitoring system. J Environ Radioact 2023; 268-269:107249. [PMID: 37494791 DOI: 10.1016/j.jenvrad.2023.107249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/11/2023] [Accepted: 07/20/2023] [Indexed: 07/28/2023]
Abstract
The goal of this work was to develop a methodology for risk assessment in case of an accident originating from a nuclear power plant, and consequently, to improve the relevant radiation monitoring network. In specific, the study involved risk estimation in Greece from a transboundary nuclear power plant accident. The tool employed was JRODOS (Java-based Real-time Decision Support), which is a system for off-site emergency management of radioactive material in the environment. This tool, widely used to generate and study scenarios for nuclear accidents worldwide, provides valuable insight to facilitate emergency preparedness and response. The probability of the plume arriving at numerous regions within the country was calculated, along with the maximum dose rates in case of transport. A risk assessment was performed, and geographical regions were prioritized in terms of risk-based environmental radioactivity burden. A total of 29 administrative districts were identified as low to medium-risk regions. Acquired results were used to determine the optimal spatial distribution of detectors for upgrading the existing monitoring network of environmental radioactivity.
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Affiliation(s)
- N Salpadimos
- Greek Atomic Energy Commission (EEAE), Greece; Medical School, National and Kapodistrian University of Athens, Greece.
| | | | - I Seimenis
- Medical School, National and Kapodistrian University of Athens, Greece
| | | | - E Carinou
- Greek Atomic Energy Commission (EEAE), Greece
| | - C Housiadas
- Greek Atomic Energy Commission (EEAE), Greece
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Karnachoriti M, Stathopoulos I, Kouri M, Spyratou E, Orfanoudakis S, Lykidis D, Lambropoulou Μ, Danias N, Arkadopoulos N, Efstathopoulos EP, Raptis YS, Seimenis I, Kontos AG. Biochemical differentiation between cancerous and normal human colorectal tissues by micro-Raman spectroscopy. Spectrochim Acta A Mol Biomol Spectrosc 2023; 299:122852. [PMID: 37216817 DOI: 10.1016/j.saa.2023.122852] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/29/2023] [Accepted: 05/08/2023] [Indexed: 05/24/2023]
Abstract
Human colorectal tissues obtained by ten cancer patients have been examined by multiple micro-Raman spectroscopic measurements in the 500-3200 cm-1 range under 785 nm excitation. Distinct spectral profiles are recorded from different spots on the samples: a predominant 'typical' profile of colorectal tissue, as well as those from tissue topologies with high lipid, blood or collagen content. Principal component analysis identified several Raman bands of amino acids, proteins and lipids which allow the efficient discrimination of normal from cancer tissues, the first presenting plurality of Raman spectral profiles while the last showing off quite uniform spectroscopic characteristics. Tree-based machine learning experiment was further applied on all data as well as on filtered data keeping only those spectra which characterize the largely inseparable data clusters of 'typical' and 'collagen-rich' spectra. This purposive sampling evidences statistically the most significant spectroscopic features regarding the correct identification of cancer tissues and allows matching spectroscopic results with the biochemical changes induced in the malignant tissues.
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Affiliation(s)
- M Karnachoriti
- School of Applied Mathematical and Physical Sciences, National Technical University Athens, 15780 Zografou, Athens, Greece; Department of Medicine, Democritus University of Thrace, 68100 Alexandroupolis, Greece
| | - I Stathopoulos
- 2(nd) Department of Radiology, Medical School, National & Kapodistrian University of Athens, 15772 Athens, Greece
| | - M Kouri
- Department of Medicine, Democritus University of Thrace, 68100 Alexandroupolis, Greece; 2(nd) Department of Radiology, Medical School, National & Kapodistrian University of Athens, 15772 Athens, Greece; Medical Physics Program, University of Massachusetts Lowell, MA 01854, United States
| | - E Spyratou
- Department of Medicine, Democritus University of Thrace, 68100 Alexandroupolis, Greece; 2(nd) Department of Radiology, Medical School, National & Kapodistrian University of Athens, 15772 Athens, Greece
| | - S Orfanoudakis
- School of Applied Mathematical and Physical Sciences, National Technical University Athens, 15780 Zografou, Athens, Greece; Alpha Information Technology S.A., Software & System Development, 68131 Alexandroupolis, Greece
| | - D Lykidis
- Laboratory of Histology-Embryology, Medical Department, Democritus University of Thrace, Alexandroupolis, Greece
| | - Μ Lambropoulou
- Laboratory of Histology-Embryology, Medical Department, Democritus University of Thrace, Alexandroupolis, Greece
| | - N Danias
- 4(th) Department of Surgery, School of Medicine, Attikon University Hospital, Univ. of Athens, 12462 Athens, Greece
| | - N Arkadopoulos
- 4(th) Department of Surgery, School of Medicine, Attikon University Hospital, Univ. of Athens, 12462 Athens, Greece
| | - E P Efstathopoulos
- 2(nd) Department of Radiology, Medical School, National & Kapodistrian University of Athens, 15772 Athens, Greece
| | - Y S Raptis
- School of Applied Mathematical and Physical Sciences, National Technical University Athens, 15780 Zografou, Athens, Greece
| | - I Seimenis
- Medical School, National and Kapodistrian University of Athens, 11527 Athens, Greece
| | - A G Kontos
- School of Applied Mathematical and Physical Sciences, National Technical University Athens, 15780 Zografou, Athens, Greece.
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Sharma R, Tsiamyrtzis P, Webb A, Seimenis I, Loukas C, Leiss E, Tsekos N. DEEP LEARNING IN UPSCALING LOW QUALITY MR IMAGES: A COMPARISON STUDY OF THREE UNET ARCHITECTURES WITH AND WITHOUT PRIOR EMPLOYMENT. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03169-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Papadogiannis P, Karavasilis E, Papathanasiou M, Seimenis I, Efstathopoulos E. MRI TEXTURE ANALYSIS AS A TOOL FOR DIAGNOSIS, ASSESSMENT AND MONITORING OF MULTIPLE SCLEROSIS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03153-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Dimakopoulou A, Karnachoriti M, Spyratou E, Seimenis I, Venetis S, Lambropoulou M, Efstathopoulos E, Kontos A. RAMAN SPECTRA OF HUMAN COLORECTAL TISSUES BY VARYING THE EXCITATION WAVELENGTHS FROM 514 NM TO 785 NM: DEFINING THE OPTIMUM LASER LINES FOR CANCER DETECTION. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03150-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Archontakis P, Papagiannis P, Seimenis I, Pantelis E. OPTIMIZATION OF THE IMAGING DOSE IN CYBERKNIFE CLINICAL APPLICATIONS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03037-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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7
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Avgoullas K, Ploussi A, Papagiannis I, Avramidis D, Tsoutsinos A, Maragou A, Efstathopoulos E, Seimenis I. EVALUATION OF ORGAN AND EFFECTIVE DOSES DURING PEDIATRIC RADIOFREQUENCY ABLATIONS USING DIFFERENT COMPUTATIONAL TOOLS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03114-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Velonis M, Koutchouras P, Papavasileiou P, Papanastasiou E, Zapros A, Hatziioannou K, Emfietzoglou D, Seimenis I. CHARACTERISTICS OF GAFCHROMIC XR-SP2 SELF-DEVELOPING FILMS FOR QUALITY ASSURANCE MEASUREMENTS IN KV IMAGING. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03045-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Velonis M, Papavasileiou P, Papanastasiou E, Zapros A, Hatziioannou K, Seimenis I. CBCT DOSE ESTIMATION IN IMAGE GUIDED RADIOTHERAPY: A MONTE-CARLO STUDY. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03100-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Koumatzidis D, Seimenis I, Constantinidis T, Adamopoulos A. CYCLIC RECURRENCE, QUARANTINE AND VACCINATION POLICIES IN EPIDEMIOLOGY MATHEMATICAL MODELS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03157-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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11
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Theocharis S, Pappas E, Seimenis I, Petrokokkinos L, Dellios D, Paraskevopoulou C, Kollias G, Karaiskos P. PHANTOM-BASED DISTORTION EVALUATION IN 3T T2-WEIGHTED MR IMAGES FOR CRANIAL STEREOTACTIC RADIOSURGERY AND RADIOTHERAPY TREATMENT PLANNING. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03190-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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12
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Avgoullas K, Ploussi A, Papagiannis I, Avramidis D, Tsoutsinos A, Maragou A, Efstathopoulos E, Seimenis I. EFFECTIVE DOSE AND CANCER RISK ESTIMATION IN PEDIATRIC PATIENTS UNDERGOING RADIOFREQUENCY CATHETER ABLATION FOR SUPRAVENTRICULAR TACHYCARDIA TREATMENT. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03113-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Karnachoriti M, Spyratou E, Orphanoudakis S, Lambropoulou M, Seimenis I, Efstathopoulos E, Raptis Y, Kontos A. RAMAN SCATTERING AS A TOOL FOR DIAGNOSIS OF COLORECTAL CANCER CURRENT STATUS AND PRACTICAL EXPERIMENTAL SOLUTIONS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03018-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Kouri M, Spyratou E, Benetis S, Seimenis I, Kontos A, Lambropoulou M, Efstathopoulos E. ADVANCED RAMAN SPECTROSCOPY: A ‘‘GUIDING LIGHT’’ TOWARDS CANCER DIAGNOSIS AND SURGERY. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03017-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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15
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Gkotsis D, Vlachopoulou A, Dimos K, Despotopoulos E, Kapsalaki E, Seimenis I. EFFECTIVE AND TIME-EFFICIENT IN VIVO 1H-MRS IN NEURO-ONCOLOGY: A PRACTICAL GUIDE FOR NON-EXPERTS. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03061-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Abissi P, Lymperopoulou G, Koutoulidis V, Grigoropoulos P, Papagiannis P, Seimenis I, Fiebich M, Agrokostas V. EVALUATION OF RADIATION BURDEN AND ASSOCIATED RISK IN SMOLDERING MULTIPLE MYELOMA PATIENTS MONITORED USING REPEATED CT IMAGING. Phys Med 2022. [DOI: 10.1016/s1120-1797(22)03047-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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17
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Archontakis P, Papagiannis P, Seimenis I, Pantelis E. PO-1536 Imaging dose distributions from CyberKnife robotic image guided radiotherapy. Radiother Oncol 2022. [DOI: 10.1016/s0167-8140(22)03500-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Velonis M, Papanastasiou E, Hatziioannou K, Siountas A, Kamperis E, Papavasileiou P, Seimenis I. Dose optimisation of 2D x-ray image acquisition protocols in image-guided radiotherapy. Phys Med 2021. [DOI: 10.1016/s1120-1797(22)00402-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Pappas E, Seimenis I, Kouris P, Lampropoulos K, Karaiskos P. Stereotactic radiosurgery for multiple brain metastases: does MR/CT co-registration improve target localization accuracy compared to the MR-only approach? Phys Med 2021. [DOI: 10.1016/s1120-1797(22)00374-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Dellios D, Seimenis I, Pappas E, Karaiskos P, Kollias G. Evaluation of MR image correction schemes for accurate lesion localization in intracranial stereotactic radiosurgery. Phys Med 2021. [DOI: 10.1016/s1120-1797(22)00132-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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21
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Busoni S, Bock M, Chmelik M, Colgan N, De Bondt T, Hanson LG, Israel M, Kugel H, Maieron M, Mazzoni LN, Seimenis I, Vestergaard P. ADDENDUM to EFOMP Policy statement No.14 "The role of the Medical Physicist in the management of safety within the magnetic resonance imaging environment: EFOMP recommendations". Phys Med 2021; 89:303-305. [PMID: 34492497 DOI: 10.1016/j.ejmp.2021.07.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- S Busoni
- Medical Physics Department, Firenze University Hospital - AOU Careggi, Firenze, Italy.
| | - M Bock
- Radiology - Medical Physics Dpt., University Medical Center Freiburg, Freiburg, Germany
| | - M Chmelik
- Department of Technical Disciplines in Health Care, Faculty of Health Care, University of Prešov, Prešov, Slovakia
| | - N Colgan
- Galway University Hospital, National University of Ireland Galway, Galway, Ireland
| | - T De Bondt
- Vinçotte - Controlatom, Vilvoorde, Belgium; De Bondt Consulting BV, Antwerp, Belgium
| | - L G Hanson
- Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Amager and Hvidovre, Copenhagen, Denmark; Section for Magnetic Resonance, DTU Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - M Israel
- Department of Hygiene, Medical Ecology and Professional Diseases, Medical University - Pleven, Bulgaria; Department of Physical Factors, National Centre of Public Health and Analyses, Sofia, Bulgaria
| | - H Kugel
- University Clinic for Radiology, University Hospital Muenster, Muenster, Germany
| | - M Maieron
- Health Physics Department, Azienda Sanitaria Universitaria Integrata di Udine, Udine, Italy
| | - L N Mazzoni
- Health Physics Unit, AUSL Toscana Centro, Pistoia, Italy
| | - I Seimenis
- School of Medicine, National and Kapodistrian University of Athens, Athens, Greece
| | - P Vestergaard
- Indkøb & Medicoteknik, Region Midtjylland, Aarhus, Denmark
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Psarras M, Ploussi A, Carinou E, Brountzos E, Spiliopoulos SC, Palialexis K, Kelekis A, Filippiadis D, Seimenis I, Efstathopoulos EP. RADIATION DOSES TO THE EYE LENS AND FOREHEAD OF INTERVENTIONAL RADIOLOGISTS: HOW HIGH AND ON WHAT GROUNDS? Radiat Prot Dosimetry 2020; 190:150-157. [PMID: 32626896 DOI: 10.1093/rpd/ncaa097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 05/05/2020] [Accepted: 06/10/2020] [Indexed: 02/05/2023]
Abstract
The aim of the study was to measure and evaluate the radiation dose to the eye lens and forehead of interventional radiologists (IRs). The study included 96 procedures (lower-limb percutaneous transluminal angioplasties, embolisations/chemoembolisations and vertebroplasties) performed by 6 IRs. A set of seven thermoluminescence dosemeters was allocated to each physician. The highest dose per procedure was found for the left eye lens of the primary operator in vertebroplasties (1576 μSv). Left and right eye doses were linearly correlated to left and right forehead doses, respectively. A workload-based estimation of the annual dose to participating IRs revealed that the occupational dose limit for the eye lens can be easily exceeded. The left eye dose of ΙRs must be routinely monitored on a personalised basis. Τhe left eye dose measurement provides a reliable assessment of the ipsilateral forehead dose, along with valid estimations for the right eye and right forehead doses.
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Affiliation(s)
- M Psarras
- 2nd Department of Radiology, Medical Physics Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - A Ploussi
- 2nd Department of Radiology, Medical Physics Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - E Carinou
- Greek Atomic Energy Commission (GAEC), 15310, Agia Paraskevi, Attiki, Greece
| | - E Brountzos
- 2nd Department of Radiology, Interventional Radiology Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - S C Spiliopoulos
- 2nd Department of Radiology, Interventional Radiology Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - K Palialexis
- 2nd Department of Radiology, Interventional Radiology Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - A Kelekis
- 2nd Department of Radiology, Interventional Radiology Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - D Filippiadis
- 2nd Department of Radiology, Interventional Radiology Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
| | - I Seimenis
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Athens, 115 27, Greece
| | - E P Efstathopoulos
- 2nd Department of Radiology, Medical Physics Unit, National and Kapodistrian University of Athens, Attikon University Hospital, 12462, Athens, Greece
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Gkotsis DE, Gotsis ED, Lymperopoulou G, Karaiskos P, Seimenis I. Determination of the R 2* relaxation rate constant for estimating hepatic iron concentration: A customized approach that considers liver fat infiltration. Phys Med 2020; 76:150-158. [PMID: 32679410 DOI: 10.1016/j.ejmp.2020.06.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 06/05/2020] [Accepted: 06/23/2020] [Indexed: 10/23/2022] Open
Abstract
PURPOSE Α customized approach to determine R2* relaxation rate for hepatic iron concentration (HIC) estimation is presented, and is evaluated in the context of concurrent liver fat infiltration. METHODS The proposed method employs a customized acquisition protocol, featuring a 16-echo, gradient-echo sequence, and a bi-exponential least squares fitting that considers baseline noise and uses a cosine function to correct for fat-induced signal oscillation. 193 patients with wide-ranging HIC and liver fat fraction (FF) were imaged at 1.5 T. In severely iron-overload patients, a four-echo train technique was applied to enforce all 16 echoes in the 1.2-4.0 ms range. Acquired data were compared to corresponding results obtained with the IDEAL IQ method. RESULTS Techniques employed to counter the rapid signal decay in iron-overloaded liver, such as the offset and the truncation methods, have to be combined with the appropriate calibration curve to provide reliable HIC estimation. When high grade steatosis and siderosis co-exist, fat-suppression may downgrade siderosis. A high correlation was observed between data obtained with the proposed technique and the IDEAL IQ method, except from the high R2* region. However, systematic differences were detected. In the concurrent presence of high FF and non-severe iron overload, it is postulated that the bi-exponential model may attribute patient siderosis grading more accurately than IDEAL IQ, while simultaneously providing reliable FF estimation. CONCLUSIONS The proposed approach is widely available and seems capable of providing reliable R2* measurements regardless of liver steatosis grading, whilst it succeeds in averting significant R2* underestimation in severely iron-overloaded liver.
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Affiliation(s)
- D E Gkotsis
- National and Kapodistrian University of Athens, Medical School, Department of Medical Physics, Greece
| | | | - G Lymperopoulou
- National and Kapodistrian University of Athens, Medical School, 1(st) Department of Radiology, Greece
| | - P Karaiskos
- National and Kapodistrian University of Athens, Medical School, Department of Medical Physics, Greece
| | - I Seimenis
- National and Kapodistrian University of Athens, Medical School, Department of Medical Physics, Greece.
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Pappas E, Kalaitzakis G, Boursianis T, Zoros E, Zourari K, Pappas EP, Makris D, Seimenis I, Efstathopoulos E, Maris TG. Dosimetric performance of the Elekta Unity MR-linac system: 2D and 3D dosimetry in anthropomorphic inhomogeneous geometry. ACTA ACUST UNITED AC 2019; 64:225009. [DOI: 10.1088/1361-6560/ab52ce] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Pappas E, Kalaitzakis G, Seimenis I, Pappas E, Maris T. Clinical IMRT Irradiation with an MR-Linac System: A Methodology and Preliminary Results for a Real-Time Verification of Spatial Accuracy of Dose Delivery. Int J Radiat Oncol Biol Phys 2019. [DOI: 10.1016/j.ijrobp.2019.06.565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Kotini A, Birbilis T, Anninos P, Seimenis I. Magnetoencephalography and normal pressure hydrocephalus: A case report. J Integr Neurosci 2018:JIN078. [PMID: 29689731 DOI: 10.3233/jin-180078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A 82-year-old male experiencing headaches, dementia, urinary incontinence and gait instability was diagnosed with normal pressure hydrocephalus (NPH) and underwent a resting state magnetoencephalography (MEG) examination. MEG data were recorded in a magnetically shielded room with a whole-head 122 channel biomagnetometer. Following MEG, a ventriculoperitoneal (VP) shunt was placed in his head and greatly improved his symptomatology. Spontaneous MEG recordings revealed lower magnetic fields at frontal and frontotemporal regions compared to central and posterior regions. This finding correlated well with the significant ventricular distention, and specifically the enlargement of the frontal horns of the lateral ventricles, observed in presurgical CT. The regional pattern of MEG signal decrease in NPH seems to be quite different from that encountered in brain atrophy. In the latter case, a more generalized distribution of low magnetic fields is observed, possibly reflecting the high sensitivity of MEG to activity originating in sulci. Acquired data suggest that MEG may be able to differentiate between NPH and brain atrophy. Furthermore, MEG could potentially constitute a non-invasive, non-imaging tool, useful in the selection of patients with NPH to undergo shunt surgery. The findings of this study warrant further research in patient groups before firm conclusions can be drawn.
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Affiliation(s)
- A Kotini
- Laboratory of Medical Physics, Medical School, Democritus University of Thrace, Alexandroupolis, 68100, Greece
| | - T Birbilis
- Department of Neurosurgery, Medical School, Democritus University of Thrace, Alexandroupolis, 68100, Greece
| | - P Anninos
- Laboratory of Medical Physics, Medical School, Democritus University of Thrace, Alexandroupolis, 68100, Greece
| | - I Seimenis
- Laboratory of Medical Physics, Medical School, Democritus University of Thrace, Alexandroupolis, 68100, Greece
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Pappas EP, Dellios D, Seimenis I, Moutsatsos A, Georgiou E, Karaiskos P. Review and comparison of geometric distortion correction schemes in MR images used in stereotactic radiosurgery applications. ACTA ACUST UNITED AC 2017. [DOI: 10.1088/1742-6596/931/1/012031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Pappas EP, Seimenis I, Moutsatsos A, Georgiou E, Nomikos P, Karaiskos P. Characterization of system-related geometric distortions in MR images employed in Gamma Knife radiosurgery applications. Phys Med Biol 2016; 61:6993-7011. [DOI: 10.1088/0031-9155/61/19/6993] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Unan M, Seimenis I, Webb A, Tsekos N. A method for fast 3D imaging of contrast enhanced vessels or catheters using magnetic resonance projections. Phys Med 2016. [DOI: 10.1016/j.ejmp.2016.07.527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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Gotsis E, Gkotsi D, Pissakas G, Seimenis I. In vivo proton MR spectroscopy of gliomatosis cerebri: Diagnosis and exploration of tumor metabolism. Phys Med 2016. [DOI: 10.1016/j.ejmp.2016.07.525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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Hatziioannou K, Badiavas K, Papanastasiou E, Seimenis I, Loukidis G, Iakovou I. Absorbed dose estimation to family members of patients treated with radioiodine for thyroid cancer. Phys Med 2016. [DOI: 10.1016/j.ejmp.2016.07.220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Seimenis I, Kourmpasi N, Kalaitzakis G, Pappas E. EP-1381: Assessment of the effect of spatial dose delivery inaccuracies on DVHs: a simulation hypophysis study. Radiother Oncol 2015. [DOI: 10.1016/s0167-8140(15)41373-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Birbilis T, Anninos P, Seimenis I, Adamopoulos A, Kotini A. MEG localization of spike sources in human patients with brain tumors. J Integr Neurosci 2014; 13:519-28. [DOI: 10.1142/s0219635214500150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Loizou CP, Petroudi S, Seimenis I, Pantziaris M, Pattichis CS. Quantitative texture analysis of brain white matter lesions derived from T2-weighted MR images in MS patients with clinically isolated syndrome. J Neuroradiol 2014; 42:99-114. [PMID: 24970463 DOI: 10.1016/j.neurad.2014.05.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Revised: 04/18/2014] [Accepted: 05/04/2014] [Indexed: 01/21/2023]
Abstract
INTRODUCTION This study investigates the application of texture analysis methods on brain T2-white matter lesions detected with magnetic resonance imaging (MRI) for the prognosis of future disability in subjects diagnosed with clinical isolated syndrome (CIS) of multiple sclerosis (MS). METHODS Brain lesions and normal appearing white matter (NAWM) from 38 symptomatic untreated subjects diagnosed with CIS as well as normal white matter (NWM) from 20 healthy volunteers, were manually segmented, by an experienced MS neurologist, on transverse T2-weighted images obtained from serial brain MR imaging scans (0 and 6-12 months). Additional clinical information in the form of the Expanded Disability Status Scale (EDSS), a scale from 0 to 10, which provides a way of quantifying disability in MS and monitoring the changes over time in the level of disability, were also provided. Shape and most importantly different texture features including GLCM and laws were then extracted for all above regions, after image intensity normalization. RESULTS The findings showed that: (i) there were significant differences for the texture futures extracted between the NAWM and lesions at 0 month and between NAWM and lesions at 6-12 months. However, no significant differences were found for all texture features extracted when comparing lesions temporally at 0 and 6-12 months with the exception of contrast (gray level difference statistics-GLDS) and difference entropy (spatial gray level dependence matrix-SGLDM); (ii) significant differences were found between NWM and NAWM for most of the texture features investigated in this study; (iii) there were significant differences found for the lesion texture features at 0 month for those with EDSS≤2 versus those with EDSS>2 (mean, median, inverse difference moment and sum average) and for the lesion texture features at 6-12 months with EDSS>2 and EDSS≤2 for the texture features (mean, median, entropy and sum average). It should be noted that whilst there were no differences in entropy at time 0 between the two groups, significant change was observed at 6-12 months, relating the corresponding features to the follow-up and disability (EDSS) progression. For the NAWM, significant differences were found between 0 month and 6-12 months with EDSS≤2 (contrast, inverse difference moment), for 6-12 months for EDSS>2 and 0 month with EDSS>2 (difference entropy) and for 6-12 months for EDSS>2 and EDSS≤2 (sum average); (iv) there was no significant difference for NAWM and the lesion texture features (for both 0 and 6-12 months) for subjects with no change in EDSS score versus subjects with increased EDSS score from 2 to 5 years. CONCLUSIONS The findings of this study provide evidence that texture features of T2 MRI brain white matter lesions may have an additional potential role in the clinical evaluation of MRI images in MS and perhaps may provide some prognostic evidence in relation to future disability of patients. However, a larger scale study is needed to establish the application in clinical practice and for computing shape and texture features that may provide information for better and earlier differentiation between normal brain tissue and MS lesions.
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Affiliation(s)
- C P Loizou
- Department of Computer Science, School of Sciences, Intercollege, 92, Ayias Phylaxeos Street, PO Box 51604, 3507 Limassol, Cyprus.
| | - S Petroudi
- Department of Computer Science, University of Cyprus, Nicosia, Cyprus.
| | - I Seimenis
- Medical Physics Laboratory, Medical School, Democritus University, Alexandroupolis, Greece.
| | - M Pantziaris
- Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
| | - C S Pattichis
- Department of Computer Science, University of Cyprus, Nicosia, Cyprus.
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Pappas E, Moutsatsos A, Karaiskos P, Pantelis E, Georgiou E, Torrens M, Seimenis I. Stereotactic frame induced geometric distortions in MR images employed in Gamma Knife radiosurgery applications. Phys Med 2014. [DOI: 10.1016/j.ejmp.2014.07.207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Adamopoulos A, Gemousakakis T, Anninos P, Seimenis I, Kotini A. Magnetoencephalography and taste. Phys Med 2014. [DOI: 10.1016/j.ejmp.2014.07.136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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37
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Gemousakakis T, Anninos P, Zissimopoulos A, Seimenis I, Adamopoulos A, Pagonopoulou O, Prassopoulos P, Kotini A. A study on the age dependency of gustatory states: Low-frequency spectral component in the resting-state MEG. J Integr Neurosci 2013; 12:427-39. [DOI: 10.1142/s0219635213500258] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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38
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Moutsatsos A, Karaiskos P, Petrokokkinos L, Sakelliou L, Pantelis E, Georgiou E, Torrens M, Seimenis I. Assessment and characterization of the total geometric uncertainty in Gamma Knife radiosurgery using polymer gels. Med Phys 2013; 40:031704. [PMID: 23464299 DOI: 10.1118/1.4789922] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This work proposes and implements an experimental methodology, based on polymer gels, for assessing the total geometric uncertainty and characterizing its contributors in Gamma Knife (GK) radiosurgery. METHODS A treatment plan consisting of 26, 4-mm GK single shot dose distributions, covering an extended region of the Leksell stereotactic space, was prepared and delivered to a polymer gel filled polymethyl methacrylate (PMMA) head phantom (16 cm diameter) used to accurately reproduce every link in the GK treatment chain. The center of each shot served as a "control point" in the assessment of the GK total geometric uncertainty, which depends on (a) the spatial dose delivery uncertainty of the PERFEXION GK unit used in this work, (b) the spatial distortions inherent in MR images commonly used for target delineation, and (c) the geometric uncertainty contributor associated with the image registration procedure performed by the Leksell GammaPlan (LGP) treatment planning system (TPS), in the case that registration is directly based on the apparent fiducial locations depicted in each MR image by the N-shaped rods on the Leksell localization box. The irradiated phantom was MR imaged at 1.5 T employing a T2-weighted pulse sequence. Four image series were acquired by alternating the frequency encoding axis and reversing the read gradient polarity, thus allowing the characterization of the MR-related spatial distortions. RESULTS MR spatial distortions stemming from main field (B0) inhomogeneity as well as from susceptibility and chemical shift phenomena (also known as sequence dependent distortions) were found to be of the order of 0.5 mm, while those owing to gradient nonlinearities (also known as sequence independent distortions) were found to increase with distance from the MR scanner isocenter extending up to 0.47 mm at an Euclidean distance of 69.6 mm. Regarding the LGP image registration procedure, the corresponding average contribution to the total geometric uncertainty ranged from 0.34 to 0.80 mm. The average total geometric uncertainty, which also includes the GK spatial dose delivery uncertainty, was found equal to (0.88 ± 0.16), (0.88 ± 0.26), (1.02 ± 0.09), and (1.15 ± 0.24) mm for the MR image series acquired with the read gradient polarity (direction) set toward right, left, posterior, and anterior, respectively. CONCLUSIONS The implemented methodology seems capable of assessing the total geometric uncertainty, as well as of characterizing its contributors, ascribed to the entire GK treatment delivery (i.e., from MR imaging to GK dose delivery) for an extended region of the Leksell stereotactic space. Results obtained indicate that the selection of both the frequency encoding axis and the read gradient polarity during MRI acquisition may affect the magnitude as well as the spatial components of the total geometric uncertainty.
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Affiliation(s)
- A Moutsatsos
- Medical Physics Laboratory, Medical School, University of Athens, Athens, Greece
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Pantelis E, Moutsatsos A, Zourari K, Petrokokkinos L, Sakelliou L, Kilby W, Antypas C, Papagiannis P, Karaiskos P, Georgiou E, Seimenis I. On the output factor measurements of the CyberKnife iris collimator small fields: Experimental determination of the kQclin,Qmsrfclin,fmsr correction factors for microchamber and diode detectors. Med Phys 2012; 39:4875-85. [DOI: 10.1118/1.4736810] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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40
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Petrokokkinos L, Zourari K, Pantelis E, Moutsatsos A, Karaiskos P, Sakelliou L, Seimenis I, Georgiou E, Papagiannis P. Dosimetric accuracy of a deterministic radiation transport based I192r brachytherapy treatment planning system. Part II: Monte Carlo and experimental verification of a multiple source dwell position plan employing a shielded applicator. Med Phys 2011; 38:1981-92. [DOI: 10.1118/1.3567507] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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41
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Loizou CP, Murray V, Pattichis MS, Seimenis I, Pantziaris M, Pattichis CS. Multiscale amplitude-modulation frequency-modulation (AM-FM) texture analysis of multiple sclerosis in brain MRI images. ACTA ACUST UNITED AC 2010; 15:119-29. [PMID: 21062681 DOI: 10.1109/titb.2010.2091279] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study introduces the use of multiscale amplitude modulation-frequency modulation (AM-FM) texture analysis of multiple sclerosis (MS) using magnetic resonance (MR) images from brain. Clinically, there is interest in identifying potential associations between lesion texture and disease progression, and in relating texture features with relevant clinical indexes, such as the expanded disability status scale (EDSS). This longitudinal study explores the application of 2-D AM-FM analysis of brain white matter MS lesions to quantify and monitor disease load. To this end, MS lesions and normal-appearing white matter (NAWM) from MS patients, as well as normal white matter (NWM) from healthy volunteers, were segmented on transverse T2-weighted images obtained from serial brain MR imaging (MRI) scans (0 and 6-12 months). The instantaneous amplitude (IA), the magnitude of the instantaneous frequency (IF), and the IF angle were extracted from each segmented region at different scales. The findings suggest that AM-FM characteristics succeed in differentiating 1) between NWM and lesions; 2) between NAWM and lesions; and 3) between NWM and NAWM. A support vector machine (SVM) classifier succeeded in differentiating between patients that, two years after the initial MRI scan, acquired an EDSS ≤ 2 from those with EDSS > 2 (correct classification rate = 86%). The best classification results were obtained from including the combination of the low-scale IA and IF magnitude with the medium-scale IA. The AM-FM features provide complementary information to classical texture analysis features like the gray-scale median, contrast, and coarseness. The findings of this study provide evidence that AM-FM features may have a potential role as surrogate markers of lesion load in MS.
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Affiliation(s)
- C P Loizou
- Department of Computer Science, School of Sciences, Intercollege, CY-3507 Limassol, Cyprus.
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Moutsatsos A, Petrokokkinos L, Karaiskos P, Papagiannis P, Georgiou E, Dardoufas K, Sandilos P, Torrens M, Pantelis E, Kantemiris I, Sakelliou L, Seimenis I. Gamma Knife output factor measurements using VIP polymer gel dosimetry. Med Phys 2009; 36:4277-87. [DOI: 10.1118/1.3183500] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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43
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Efstathopoulos EP, Kelekis NL, Pantos I, Brountzos E, Argentos S, Grebác J, Ziaka D, Katritsis DG, Seimenis I. Reduction of the estimated radiation dose and associated patient risk with prospective ECG-gated 256-slice CT coronary angiography. Phys Med Biol 2009; 54:5209-22. [PMID: 19671974 DOI: 10.1088/0031-9155/54/17/009] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Computed tomography (CT) coronary angiography has been widely used since the introduction of 64-slice scanners and dual-source CT technology, but high radiation doses have been reported. Prospective ECG-gating using a 'step-and-shoot' axial scanning protocol has been shown to reduce radiation exposure effectively while maintaining diagnostic accuracy. 256-slice scanners with 80 mm detector coverage have been currently introduced into practice, but their impact on radiation exposure has not been adequately studied. The aim of this study was to assess radiation doses associated with CT coronary angiography using a 256-slice CT scanner. Radiation doses were estimated for 25 patients scanned with either prospective or retrospective ECG-gating. Image quality was assessed objectively in terms of mean CT attenuation at selected regions of interest on axial coronary images and subjectively by coronary segment quality scoring. It was found that radiation doses associated with prospective ECG-gating were significantly lower than retrospective ECG-gating (3.2 +/- 0.6 mSv versus 13.4 +/- 2.7 mSv). Consequently, the radiogenic fatal cancer risk for the patient is much lower with prospective gating (0.0176% versus 0.0737%). No statistically significant differences in image quality were observed between the two scanning protocols for both objective and subjective quality assessments. Therefore, prospective ECG-gating using a 'step-and-shoot' protocol that covers the cardiac anatomy in two axial acquisitions effectively reduces radiation doses in 256-slice CT coronary angiography without compromising image quality.
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Affiliation(s)
- E P Efstathopoulos
- 2nd Department of Radiology, Medical School, University of Athens, Greece.
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Kantemiris I, Petrokokkinos L, Angelopoulos A, Bassler N, Seimenis I, Karaiskos P. Carbon beam dosimetry using VIP polymer gel and MRI. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/164/1/012055] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Moutsatsos A, Petrokokkinos L, Zourari K, Papagiannis P, Karaiskos P, Dardoufas K, Damilakis J, Seimenis I, Georgiou E. Gamma Knife relative dosimetry using VIP polymer gel and EBT radiochromic films. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/164/1/012053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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46
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Petrokokkinos L, Moutsatsos A, Karaiskos P, Kouridou V, Pantelis E, Papagiannis P, Seimenis I. On the use of VIP gel dosimetry in HDR brachytherapy. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/164/1/012051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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47
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Pantelis E, Antypas C, Petrokokkinos L, Karaiskos P, Papagiannis P, Kozicki M, Georgiou E, Sakelliou L, Seimenis I. Dosimetric characterization of CyberKnife radiosurgical photon beams using polymer gels. Med Phys 2008; 35:2312-20. [PMID: 18649464 DOI: 10.1118/1.2919099] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dose distributions registered in water equivalent, polymer gel dosimeters were used to measure the output factors and off-axis profiles of the radiosurgical photon beams employed for CyberKnife radiosurgery. Corresponding measurements were also performed using a shielded silicon diode commonly employed for CyberKnife commissioning, the PinPoint ion chamber, and Gafchromic EBT films, for reasons of comparison. Polymer gel results of this work for the output factors of the 5, 7.5, and 10 mm diameter beams are (0.702 +/- 0.029), (0.872 +/- 0.039), and (0.929 +/- 0.041), respectively. Comparison of polymer gel and diode measurements shows that the latter overestimate output factors of the two small beams (5% for the 5 mm beam and 3% for the 7.5 mm beams). This is attributed to the nonwater equivalence of the high atomic number silicon material of the diode detector. On the other hand, the PinPoint chamber is found to underestimate output factors up to 10% for the 5 mm beam due to volume averaging effects. Polymer gel and EBT film output factor results are found in close agreement for all beam sizes, emphasizing the importance of water equivalence and fine detector sensitive volume for small field dosimetry. Relative off-axis profile results are in good agreement for all dosimeters used in this work, with noticeable differences observed only in the PinPoint estimate of the 80%-20% penumbra width, which is relatively overestimated.
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Affiliation(s)
- E Pantelis
- Medical Physics Department, Iatropolis - Magnitiki Tomografia Clinic and Diagnostic Center, Ethnikis Antistaseos 54-56, Chalandri, 152 31 Athens, Greece.
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Abstract
Composite veneering materials are used as alternatives to porcelain in fixed prosthodontics. Mechanical retention of the resin on the metal framework has been associated with the formation of gaps at the resin/alloy interface, and failure of the restoration. Several chemical bonding systems have been introduced to promote resin adhesion. The purpose of the present study was to evaluate the shear bond strength of three photocured composites (Artglass, Solidex & Signum+) to a Ni-Cr alloy.72 wax disks covered with 150-mum diameter beads were cast and divided in two equal groups. In the first group, Metal Photo Primer was applied on the casting surface, while the Siloc system was used in the second. Each group was divided in three subgroups of 12 samples, in which the three composites were photocured. Half of the specimens of each subgroup were subjected to 1000 and 5000 thermal cycles (5 and 55 degrees C) respectively. All specimens were tested in shear in a universal testing machine. The Siloc-Solidex group showed the highest bond strength (17.3 +/- 3.7 MPa). No statistically significant difference was found between specimens treated with Metal Photo Primer or Siloc. Thermocycling did not significantly affect the bond strength values. Solidex showed an adhesive failure mode for both alloy surface treatments, while Artglass and Signum+ exhibited combination failures. Conclusively, the appropriate alloy surface treatment - resin combination can significantly improve the resin-alloy shear bond strength. Specifically, Solidex resin exhibited significantly higher bond values compared with Artglass and Signum+, for both surface treatments and thermocycling procedures.
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Affiliation(s)
- I Seimenis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece
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Papagiannis P, Pantelis E, Georgiou E, Karaiskos P, Angelopoulos A, Sakelliou L, Stiliaris S, Baltas D, Seimenis I. Polymer gel dosimetry for the TG-43 dosimetric characterization of a new 125I interstitial brachytherapy seed. Phys Med Biol 2006; 51:2101-11. [PMID: 16585848 DOI: 10.1088/0031-9155/51/8/010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In this work, a polymer gel-magnetic resonance (MR) imaging method is employed for the dosimetric characterization of a new 125I low dose rate seed (IsoSeed model I25.S17). Two vials filled with PABIG gel were prepared in-house and one new seed as well as one commercially available 125I seed of similar dose rate and well-known dosimetric parameters (IsoSeed model I25.S06) were positioned in each vial. Both seeds in each vial were MR scanned simultaneously on days 11 and 26 after implantation. The data obtained from the known seed in each vial are used to calibrate the gel dose response which, for the prolonged irradiation duration necessitated by the investigated dose rates, depends on the overall irradiation time. Data for this study are presented according to the AAPM TG-43 dosimetric formalism. Polymer gel results concerning the new seed are compared to corresponding, published dosimetric results obtained, for the purpose of the new seed clinical implementation, by our group using the established methods of Monte Carlo (MC) simulation and thermo-luminescence dosimetry (TLD). Polymer gel dosimetry yields an average dose rate constant value of lambda = (0.921 +/- 0.031) cGy h(-1) U(-1) relative to (MC)lambda = (0.929 +/- 0.014) cGy h(-1) U(-1), (TLD)lambda = (0.951 +/- 0.044) cGy h(-1) U(-1) and the average value of Lambda = (0.940 +/- 0.051) cGy h(-1) U(-1) proposed for the clinical implementation of the new seed. Results for radial dose function, g(L)(r), and anisotropy function, F(r, theta), also agree with corresponding MC calculations within experimental uncertainties which are smaller for the polymer gel method compared to TLD. It is concluded that the proposed polymer gel-magnetic resonance imaging methodology could be used at least as a supplement to the established techniques for the dosimetric characterization of new low energy and low dose rate interstitial brachytherapy seeds.
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Affiliation(s)
- P Papagiannis
- Nuclear and Particle Physics Section, Physics Department, University of Athens, Panepistimioupolis, Ilisia, 157 71 Athens, Greece.
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Baras P, Seimenis I, Sandilos P, Vlahos L, Bieganski T, Georgiou E, Pantelis E, Papagiannis P, Sakelliou L. An evaluation of the TSE MR sequence for time efficient data acquisition in polymer gel dosimetry of applications involving high doses and steep dose gradients. Med Phys 2005; 32:3339-45. [PMID: 16370420 DOI: 10.1118/1.2065367] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The use of magnetic resonance imaging as a readout method for polymer gel dosimetry commonly involves long imaging sessions, particularly when high spatial resolution is required in all three dimensions, for the investigation of dose distributions with steep dose gradients and stringent dose delivery specifications. In this work, a volume selective turbo spin echo (TSE) pulse sequence is compared to the established Carr-Purcell-Meiboom-Gill (CPMG) multiecho acquisition with regard to providing accurate dosimetric results in significantly reduced imaging times. Polyethylene glycol diacrylate based (PABIG) gels were irradiated and subsequently scanned to obtain R2 relaxation rate measurements, using a CPMG multiecho sequence and a dual echo TSE utilizing an acceleration (turbo) factor of 64. R2 values, plotted against corresponding Monte Carlo dose calculations, provided calibration data of PABIG gels dose response over a wide dose range. A linear R2 versus dose relationship was demonstrated for both sequences with TSE results presenting reduced dose sensitivity. Although TSE data were found to deviate from linearity at lower doses compared to CPMG data, a relatively wide dynamic dose range of response extending up to approximately 100 Gy was observed for both sequences. The TSE and CPMG sequences were evaluated with a brachytherapy irradiation using a high dose rate 192Ir source and a gamma knife stereotactic radiosurgery irradiation with a single 4 mm collimator helmet shot. Dosimetric results obtained with the TSE and CPMG are shown to compare equally well with the expected dose distributions for these irradiations. The 60-fold scan time reduction achieved with TSE implies that this sequence could prove to be a useful tool for the introduction of polymer gel dosimetry in clinical radiation therapy applications involving high doses and steep dose gradients.
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Affiliation(s)
- P Baras
- Philips Hellas Medical Systems, 44 Kifissias Ave., Maroussi 151 25, Athens, Greece
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