John Antonakos

Mr. John Antonakos

2nd Department of Radiology, Medical School, University of Athens Medical School, Athens
orcid

Research Focus & Metrics

Academic Career Length

6Years (2021-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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13 July 2021 in Healthcare
Verified
Journal Article
Open access
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JAJohn Antonakos
John Antonakos
Kyriakos SouliotisKyriakos Souliotis
Kyriakos Souliotis
TPTheodora Psaltopoulou
Theodora Psaltopoulou
YTYANNIS TOUNTAS
YANNIS TOUNTAS
MKMARIA KANTZANOU
MARIA KANTZANOU
Introduction: A positive safety culture is considered a pillar of safety in health organizations and the first crucial step for quality health services. In this context, the aim of this study was to set a reference evaluation for the patient safety culture in the primary health sector in Greece, based on health professionals’ perceptions. Methods: We used a cross-sectional survey with a 62% response rate (n = 459), conducted in primary care settings in Greece (February to May 2020). We utilized the “Medical Office Survey on Patient Safety Culture” survey tool from the Agency for Healthcare Research and Quality (AHRQ). The study participants were health professionals who interacted with patients from 12 primary care settings in Greece. Results: The most highly ranked domains were: “Teamwork” (82%), “Patient Care Tracking/Follow-up” (80% of positive scores), and “Organizational Learning” (80%); meanwhile, the lowest-ranked ones were: “Leadership Support for Patient Safety” (62%) and “Work Pressure and Pace” (46%). The other domains, such as “Overall Perceptions of Patient Safety and Quality” (77%), “Staff Training“ (70%), “Communication about Error” (70%), “Office Processes and Standardization” (67%), and “Communication Openness” (64%), ranked somewhere in between. Conclusions: A positive safety culture was identified in primary care settings in Greece, although weak areas concerning the safety culture should be addressed in order to improve patient safety.

30 November 2023 in Journal of Imaging
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Journal Article
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ESEvangelia Siomou
Evangelia Siomou
Dimitrios FilippiadisDimitrios Filippiadis
Dimitrios Filippiadis
Efstathios P. EfstathopoulosEfstathios P. Efstathopoulos
Efstathios P. Efstathopoulos
JAJohn Antonakos
John Antonakos
GPGeorge S. Panayiotakis
George S. Panayiotakis
This study establishes typical Diagnostic Reference Levels (DRL) values and assesses patient doses in computed tomography (CT)-guided biopsy procedures. The Effective Dose (ED), Entrance Skin Dose (ESD), and Size-Specific Dose Estimate (SSDE) were calculated using the relevant literature-derived conversion factors. A retrospective analysis of 226 CT-guided biopsies across five categories (Iliac bone, liver, lung, mediastinum, and para-aortic lymph nodes) was conducted. Typical DRL values were computed as median distributions, following guidelines from the International Commission on Radiological Protection (ICRP) Publication 135. DRLs for helical mode CT acquisitions were set at 9.7 mGy for Iliac bone, 8.9 mGy for liver, 8.8 mGy for lung, 7.9 mGy for mediastinal mass, and 9 mGy for para-aortic lymph nodes biopsies. In contrast, DRLs for biopsy acquisitions were 7.3 mGy, 7.7 mGy, 5.6 mGy, 5.6 mGy, and 7.4 mGy, respectively. Median SSDE values varied from 7.6 mGy to 10 mGy for biopsy acquisitions and from 11.3 mGy to 12.6 mGy for helical scans. Median ED values ranged from 1.6 mSv to 5.7 mSv for biopsy scans and from 3.9 mSv to 9.3 mSv for helical scans. The study highlights the significance of using DRLs for optimizing CT-guided biopsy procedures, revealing notable variations in radiation exposure between helical scans covering entire anatomical regions and localized biopsy acquisitions.

24 December 2022 in Radiation Protection Dosimetry
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Journal Article
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MVMarialena Vossou
Marialena Vossou
SSStavros Spiliopoulos
Stavros Spiliopoulos
KPKostas Palialexis
Kostas Palialexis
JAJohn Antonakos
John Antonakos
EEEfstathios P Efstathopoulos
Efstathios P Efstathopoulos
The establishment of typical diagnostic reference levels (DRLs) values according to the complexity indices (CIs) for hepatic chemoembolisation (HC), iliac stent placement (ISP) and femoropopliteal revascularisation (FR) is reported in this study. To estimate patients’ stochastic effects, effective dose was calculated through dose area product (DAP) values of this study and E/DAP conversion factors derived from the literature. Data for DAP, Reference Air Kerma (Ka,r) and fluoroscopy time (FT) were collected for 218 patients and CIs were assigned to each procedure to extract DRLs. To estimate effective dose, conversion factors and DAP values were used for seven IR procedures. DRL values for DAP were 141, 130 and 28 Gy*cm2 for HC, ISP, and FR, respectively. The corresponding DRL values for Ka,r were 634.6, 300.1 and 112.0 mGy, and for FT were 15.3, 12.4 and 17.9 min, respectively. CIs in interventional radiology are a useful tool for the optimisation of DRLs since they contribute to patient’s doses.

28 February 2025 in Journal of Imaging
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Journal Article
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JAJohn Antonakos
John Antonakos
MPMatina Patsioti
Matina Patsioti
Maria-Eleni ZachouMaria-Eleni Zachou
Maria-Eleni Zachou
GCGeorge Christopoulos
George Christopoulos
Efstathios P. EfstathopoulosEfstathios P. Efstathopoulos
Efstathios P. Efstathopoulos
The purpose of this study is to determine the typical diagnostic reference levels (DRLs) of radiation exposure values for chest radiographs in neonates (<1 kg) in mobile imaging at a University Hospital in Greece and compare these values with the existing DRL values from the literature. Patient and dosimetry data, including age, sex, weight, tube voltage (kV), tube current (mA), exposure time (s), exposure index of a digital detector (S), and dose area product (DAP) were obtained from a total of 80 chest radiography examinations performed on neonates (<1 kg and <30 days old). All examinations were performed in a single X-ray system, and all data (demographic and dosimetry data) were collected from the PACS of the hospital. Typical radiation exposure values were determined as the median value of DAP and ESD distribution. Afterward, these typical values were compared with DRL values from other countries. Three radiologists reviewed the images to evaluate image quality for dose optimization in neonatal chest radiography. From all examinations, the mean value and standard deviation of DAP was 0.13 ± 0.11 dGy·cm2 (range: 0.01–0.46 dGy·cm2), and ESD was measured at 11.55 ± 4.96 μGy (range: 4.01–30.4 μGy). The typical values in terms of DAP and ESD were estimated to be 0.08 dGy·cm2 and 9.87 μGy, respectively. The results show that the DAP value decreases as the exposure index increases. This study’s typical values were lower than the DRLs reported in the literature because our population had lower weight and age. From the subjective evaluation of image quality, it was revealed that the vast majority of radiographs (over 80%) met the criteria for being diagnostic as they received an excellent rating in terms of noise levels, contrast, and sharpness. This study contributes to the recording of typical dose values in a sensitive and rare category of patients (neonates weighing <1 kg) as well as information on the image quality of chest X-rays that were performed in this group.

21 October 2023 in Preprints.org
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Preprint
Open access
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Evangelia SiomouEvangelia Siomou
Evangelia Siomou
Dimitrios FilippiadisDimitrios Filippiadis
Dimitrios Filippiadis
Efstathios P. EfstathopoulosEfstathios P. Efstathopoulos
Efstathios P. Efstathopoulos
JAJohn Antonakos
John Antonakos
GPGeorgios S. Panayiotakis
Georgios S. Panayiotakis
Objectives: Typical Diagnostic Reference Levels (DRL) in terms of Computed Tomography Dose Index (CTDI) and patient dose in terms of Effective Dose (ED ) and Size Specific Dose Estimate (SSDE) were estimated in Computed Tomography (CT) guided biopsy procedures. Materials and Methods: A total of 226 CT biopsy procedures - Iliac bone, liver, lung, mediastinum and para-aortic tissue - were retrospectively analyzed and Typical DRL extracted based on ICRP 135 instructions. Results: For helical mode acquisitions, DRLs in terms of CTDIvol were 9.7 mGy for Iliac bone, 8.9 mGy for liver, 8.8 mGy for lung, 7.9 mGy for mediastinal mass and 9 mGy for para-aortic lymph nodes biopsy procedures. For biopsy acquisitions, DRL values were 7.3 mGy, 7.7 mGy, 5.6 mGy, 5.6 mGy and 7.4 mGy respectively. Also, SSDE median values ranged from 7.6 mGy to 10 mGy for biopsy acquisitions and 11,3 mGy to 12,6 mGy for helical acquisitions, as well as the median values for effective dose ranged from 1.6 mSv to 5,7 mSv for biopsy scans and 3.9 to 9.3 mSv for helical scans. Conclusions: The use of DLR as an optimization tool for CT-guided biopsy procedures revealed that helical scans across the entire anatomical region greatly affect radiation dose compared to biopsy acquisitions.

21 January 2026 in Journal of Imaging
Verified
Journal Article
Open access
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JAJohn Antonakos
John Antonakos
KKKyriakos Kokkinogoulis
Kyriakos Kokkinogoulis
MGMaria Giannopoulou
Maria Giannopoulou
Efstathios P. EfstathopoulosEfstathios P. Efstathopoulos
Efstathios P. Efstathopoulos
Chest radiography remains one of the most frequently performed imaging examinations, highlighting the need for optimization of acquisition parameters to balance image quality and radiation dose. This study presents a phantom-based quantitative evaluation of chest radiography acquisition settings using a digital radiography system (AGFA DR 600). Measurements were performed at three tube voltage levels across simulated patient-equivalent thicknesses generated using PMMA slabs, with a Leeds TOR 15FG image quality phantom positioned centrally in the imaging setup. Image quality was quantitatively assessed using signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), which were calculated from mean pixel values obtained from repeated acquisitions. Radiation exposure was evaluated through estimation of entrance surface dose (ESD). The analysis demonstrated that dose-normalized performance metrics favored intermediate tube voltages for slim and average patient-equivalent thicknesses, while higher voltages were required to maintain image quality in obese-equivalent conditions. Overall, image quality and dose were found to be strongly dependent on the combined selection of tube voltage and phantom thickness. These findings indicate that modest adjustments to tube voltage selection may improve the balance between image quality and radiation dose in chest radiography. Nevertheless, as the present work is based on phantom measurements, further validation using clinical images and observer-based studies is required before any modification of routine radiographic practice.