Advantages of Cone Beam Computed Tomography (CBCT) include high-quality 3D imaging and reduced radiation exposure with relatively low cost. In this study, patient radiation exposure in CBCT implant planning dentistry was measured in terms of Kerma Area Product (KAP). Data were obtained from 217 CBCT scans on 168 individuals using a CS9300 Carestream system. Scans were made using 80-90 kVp, 4-5 mA, 8 and 13.3 s exposure time (depending on voxel size) and a fixed field of view (FOV) of 10 × 10 cm2 (medium). Mean KAP was estimated using two voxel sizes 180 × 180 × 180 μm3 and 200 × 200 × 200 μm3 and found to be 399 and 314 mGycm2, respectively. Corresponding KAP values found in literature ranged between 210 and 2140 mGycm2. Mean E was estimated using conversion coefficient factors found in literature, according to FOV size and tube voltage value and found to range between 24 and 161 μSv.

This study aimed to evaluate paediatric radiation doses in a dedicated cardiology hospital, with the objective of characterising patterns in dose variation. The ultimate purpose was to define Local (Institutional) Diagnostic Reference Levels (LDRLs) for different types of paediatric cardiac interventional procedures (IC), according to patient age. From a total of 710 cases performed during three consecutive years, by operators with more than 15 years of experience, the age was noted in only 477 IC procedures. The median values obtained for Fluoroscopy Time (FT), Number of Frames (N) and Kerma Area Product (PKA) by age range were 5.8 min, 1322 and 2.0 Gy.cm2 for <1 y; 6.5 min, 1403 and 3.0 Gy.cm2 for 1 to <5 y; 5.9 min, 950 and 7.0 Gy.cm2 for 5 to <10 y; 5.7 min, 940 and 14.0 Gy.cm2 for 10 to <16 y, respectively. A large range of patient dose data is observed, depending greatly on procedure type and patient age. In all age groups the range of median FT, N and PKA values was 3.1-15.8 min, 579-1779 and 1.0-20.8 Gy.cm2 respectively. Consequently, the definition of LDRLs presents challenges mainly due to the multiple clinical and technical factors affecting the outcome. On the other hand the lack of paediatric IC DRLs makes the identification of good practices more difficult. A consensus is needed on IC procedures nomenclature and grouping in order to allow a common assessment and comparison of doses.

À6.4, standard deviation 10.1) and uniformity (mean À6.4, standard deviation 10.1,) varied between scans, as observed by 3 experienced radiologists by visual score analysis.Iterative reconstruction was associated with a further dose reduction using level 3 (max 6) in order to avoid texture effect.Conclusions.In a simulated pediatric chest CT study, radiologist guided acquisition resulted the best choice in terms of optimal dose-image quality ratio while maintaining good image quality.

Conclusions.For limited number of targets (<8) and geometric uncertainties smaller than 1 mm, high quality plans are achieved ensuring high dose conformity to the targets, steep dose gradients and adequate radioprotection of surrounding healthy tissues.

In our dedicated catheterization laboratory, within the years 2009–2016, 8286 Interventional Cardiology (IC) procedures were performed by two interventional cardiologists with more than 10 years of experience. There were 5469 Coronary Angiographies (CA) and 2817 Percutaneous Coronary Interventions (PCI). The purpose was to analyze annual patient radiation data, investigate trends and compare with national and international literature and Dose Reference Levels (DRL). Patient doses were determined in terms of: kerma-area product PKA, fluoroscopy time FT and reference air-kerma Ka,r. Concerning the number of frames F, in 1.8% of CA cases and in 40% of PCI cases, was higher than Greek DRLs. PKA, in 13% of CA cases and in 31% of PCI cases, was higher than Greek DRLs. In 0.4% of CA cases, the calculated effective dose values were higher than 40 mSv, whereas in 0.9% PCI cases higher than 80 mSv. In 0.2% of CA cases, PSD was higher than 2 Gy and in 0.04% cases higher than 3 Gy. In 13% of PCI cases, PSD was higher than 2 Gy, in 3% higher than 3 Gy and in 0.4% higher than 5 Gy. FT in 19.2% of CA cases and in 32% of PCI cases was higher than Greek DRLs. The radiation dose trends in IC procedures in this hospital, for the last 8 years, suggest that patient radiation doses in CA are less variable through the years compared to PCI. Doses are comparable to the literature and median values are lower than Greek and European DRLs. The practice of the well experienced interventionalists, with the support of evolving technology, shows that simpler procedures, like CA, need slight shorter FT, while the most demanding procedures like PCI, appear to require more frames without increasing in FT or PSD.

The aim of the study was to analyze eight years of patient and staff radiation exposure data during Endoscopic Retrograde Cholangio-Pancreatography (ERCP). Parameters recorded and calculated were: patient age, kermaarea product (KAP), fluoroscopy time (T) and total number of images (I) in 1632 ERCP procedures. An experienced endoscopist (more than 10 years of practice) performed the ERCPs and was monitored by a thermoluminescent dosemeter worn over a 0.25 mm lead apron. Patient mean (SD) age was 70.6 (14.8) years. Median (max) of KAP value was 15.6 (371.2) Gy.cm2. Median (max) of T and I were 3.3 (50.0) min and 3 (10) images, respectively. Median values of KAP showed a reduction over the eight years, although median values of T and I showed a slight increase during the same period. KAP and T values of the present study appeared to be close to those reported in similar studies in the literature. Monthly endoscopist radiation dose was negligible due to the proper use of lead apron, collar and two leadarticulated ceiling mounted shields (90 cm width each).

Introduction: Computed Tomography (CT) produces high quality diagnostic images at the expense of increased radiation dose compared to routine radiographic examinations. The dose from the CT examinations can be reduced by controlling certain scanning parameters and optimising the employed practices. In this study a patient dosetracking software was utilised for the management of the CT doses and the optimisation of the scanning protocols. Material and Methods: DoseWatch from GE® Healthcare is a software for monitoring the radiation dose of patients undergoing CT examinations. It tracks simultaneously relevant technical and patient data. DoseWatch was used for the assessment of the scanning protocols of a Philips Brilliance 64 CT scanner during a period of three months in a large public general hospital of Athens in Greece. The dose dataset was compared with the CT Diagnostic Reference Levels (DRLs) available from the Greek Atomic Energy Commission (GAEC). Results and Conclusion: DoseWatch was deemed as a quick and effective tool for tracking and optimising the doses in CT examinations. It can be utilised as well for the improvement of the related scanning protocols. Through this suitable software, patients were identified with CT doses higher than the corresponding CT DRLs. The scanning parameters of the investigated cases were modified accordingly to achieve reduction of the corresponding CT doses.

ΦΥΣΙΚΗ [ΤEΙ ΠEΙΡΑΙΑ, ΣΧΟΛΗ ΤEΧΝΟΛΟΓΙΚΩΝ EΦΑΡΜΟΓΩΝ, ΤΜΗΜΑ ΜΗΧΑΝΙΚΩΝ ΗΛEΚΤΡΟΝΙΚΩΝ ΥΠΟΛΟΓΙΣΤΙΚΩΝ ΣΥΣΤΗΜΑΤΩΝ Τ.E.]

ΦΥΣΙΚΗ [ΤEΙ ΠEΙΡΑΙΑ, ΣΧΟΛΗ ΤEΧΝΟΛΟΓΙΚΩΝ EΦΑΡΜΟΓΩΝ, ΤΜΗΜΑ ΜΗΧΑΝΙΚΩΝ ΗΛEΚΤΡΟΝΙΚΩΝ ΥΠΟΛΟΓΙΣΤΙΚΩΝ ΣΥΣΤΗΜΑΤΩΝ Τ.E.]

ΦΥΣΙΚΗ [ΤEΙ ΠEΙΡΑΙΑ, ΣΧΟΛΗ ΤEΧΝΟΛΟΓΙΚΩΝ EΦΑΡΜΟΓΩΝ, ΤΜΗΜΑ ΜΗΧΑΝΙΚΩΝ ΗΛEΚΤΡΟΝΙΚΩΝ ΥΠΟΛΟΓΙΣΤΙΚΩΝ ΣΥΣΤΗΜΑΤΩΝ Τ.E.]

The main purpose of this work was to investigate the fluctuation of Greek indoor electromagnetic field (EMF) intensity values and identify peaks that might occur. The scientific interest is mainly focused on the bands of extremely low-frequency (ELF) magnetic fields and radiofrequency (RF) electric fields which have been suggested to be possibly carcinogenic to humans by the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR). Electromagnetic radiation (EMR) measurements were performed in a variety of indoor dwellings, in Attica and in the islands of Zakynthos and Lesvos. A total number of 4540 measurements were taken in a wide frequency range (50 Hz-2100 MHz) of which 3301 in Attica, 963 in Lesvos and 276 in Zakynthos. Statistical analysis of the data revealed specific statistically significant differences between the mean values of the electric (ELF and RF) but not the magnetic (ELF) field strengths measured at different distances from the EMF source, as well as between some of the mean values of the RF electric field at different bands. Some statistically significant differences between mean electric field values at different geographic locations were also identified. As far as the RF electric field is concerned, the maximum values, in most cases, were below 0.5 V/m, however increased values above 1 V/m and up to 5.6 V/m were occasionally observed. The ELF magnetic field values were lower than 1 μT. It may be concluded that overall, the observed indoor EMF intensity values remained well below domestic and European established limits.

This paper addresses issues of self-affinity, long-memory and self-organisation in variations of radon in soil recorded in Lesvos Island, Greece. Several techniques were employed, namely (a) power-law wavelet spectral fractal analysis, (b) estimation of Hurst exponents through (b1) rescaled-range, (b2) roughness-length, (b3) variogram and (a), (c) detrended fluctuation analysis, (d) investigation of fractal dimensions and (e) analysis of five block entropies: (e1) Shannon entropy, (e2) Shannon entropy per letter, (e3) conditional entropy, (e4) Tsallis entropy, and (e5) normalised Tsallis entropy. Long-lasting antipersistency was identified during a period of anomalous radon variations following fractional Brownian modelling. Remaining variations did not exhibit analogous behaviour and followed fractional Gaussian modelling. Antipersistent power-law-beta-exponent-values between 1.5 and 2.0 were detected during anomalies. Persistent values were also found. Hurst exponents were mainly within 0 < H < 0.5. Some persistent exponents (0.5 < H < 1) were also observed. Fractal dimensions were within 1.5 < D < 2. Radon anomalies presented lower fractal dimensions. Shannon entropy ranged between 0.77 ≤ H(n) ≤ 2.38, Shannon entropy per letter, between 0.19 ≤ h (n) ≤ 0.59, conditional entropy, between 0.01 ≤ h (n) ≤ 0.58, Tsallis entropy, between 0.55 ≤ S q  ≤ 1.01 and normalised Tsallis entropy between, 0.98 ≤ \(\hat{S}\) ≤ 5.42 (block-size n = 4). Entropies were lower during anomalies, indicating strong self-organisation. Persistency–antipersistency switching was observed, consistent with long-memory dynamics. Potential geological sources were discussed. The asperity-model was proposed. Findings were compared to results obtained under analogous methodologies in Ileia, Greece.

Four hundred and ninety-five adult patients in 16 medical centres participated in this study aiming to investigate the congruence between the volume CT dose index (CTDIvol) monitor values and measured ones during common CT procedures, performed by 20 systems. Tube output CTDIair measurements were carried out on single and multislice scanners for any kV, slice thickness, mA and FOV combination used. The maximum/minimum ratio of measured CTDIvol values found to be 3.1, 3.5, 7.4, 7.5, 4.2, 11.3 and 5.5 for head base, head cerebrum, thorax, abdomen, pelvis, cervical spine and lumbar spine protocols, respectively. The mean divergence between the measured and displayed CTDIvol values was 4.2, 3.5, 1.0, 2.7, 4.9, 3.9 and 2.8 for protocols as mentioned above, respectively. From the perspective of the number of detector rows of the scanners, the mean divergence was 6.7, 6.0, 0.8, 1.1, 0.4, 1.9, 5.3, 5.2 and 10.1 for single, dual, 4, 6, 16, 24, 64, 128 and dual source 256-slice systems, respectively.

Url:http://env-hum-comp-res.teipir.gr/

This paper addressed a fractal evolution of 11 one-month lasting MHz electromagnetic disturbances, recorded in Greece prior to nine significant earthquakes of 2009. Time-space wavelet-based power spectral techniques were employed in the analysis. All investigated signals evolved naturally to epochs of fractal organization in space and time. Continuous organization was detected in seven signals. Significant number of successive () power-law -values were observed lying between 1.5 and 3.0 or above. The majority of fractal segments exhibited anti-persistent () or persistent () behaviour. Switching between persistency and anti-persistency was also found. Locality and sensitivity were traced. Findings were considered indicative of self-organized critical states of the last stages of preparation of the investigated earthquakes. Results implied fractional Brownian modelling. Explanations were proposed in view of the asperity model. Persistent–anti-persistent MHz anomalies were due to self-organized micro-cracking of the heterogeneous medium of the earth's crust which may have led the system's evolution towards global failure. The precursory value of the signals was discussed.

Url: http://env-hum-comp-res.teipir.gr/

Url:http://env-hum-comp-res.teipir.gr/