Current Organizations / Institutes

The organizations/institutes from the scholar's latest article


Marina Chalkia has a total of 45 co-authors. Here are the top co-authors by number of shared publications:

  • Kalliopi Platoni

    Department of Applied Medical Physics, Medical School, Attikon University Hospital, National and Kapodistrian University of Athens, 11527 Athens, Greece

    10 shared publications
  • Vassilis Kouloulias

    Department of Clinical Radiation Oncology, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, 11528 Athens, Greece

    8 shared publications
  • EfstathiosPetros Efstathopoulos

    Department of Applied Medical Physics, Medical School, Attikon University Hospital, National and Kapodistrian University of Athens, 11527 Athens, Greece

    4 shared publications
  • Georgios Patatoukas

    Department of Applied Medical Physics, Medical School, Attikon University Hospital, National and Kapodistrian University of Athens, 11527 Athens, Greece

    3 shared publications
  • Andromachi Kougioumtzopoulou

    Radiation Therapy Unit, Second Department of Radiology Medical School National and Kapodistrian University of Athens Attikon General University Hospital Haidari Athens Greece

    2 shared publications
  • George Patatoukas

    Medical Physics Unit, Second Department of Radiology, Medical School National and Kapodistrian University of Athens Attikon General University Hospital Haidari Athens Greece

    2 shared publications

Latest Publications

  • Open Access

    Quality of life and religiosity of breast cancer patients undergoing adjuvant ultra-hypofractionated radiotherapy with sequential tumor bed boost: a pilot study

    by Efrosyni Kypraiou, Ioannis Koukourakis, Andromachi Kougioumtzopoulou, Kalliopi Platoni, Marina Chalkia, Kyveli Zourari, Efstathios Efstathopoulos, Nikolaos Kelekis, Anna Zygogianni, Vassilis Kouloulias

    Background/aim: Quality of life (QoL) is an important parameter that should be taken into account when assessing treatment efficacy in cancer patients. The FAST-FORWARD radiotherapy (RT) regimen (5-day schedule) for early-stage breast cancer has been reported by both physicians and patients to be associated with toxicity comparable to that of longer schedules. However, the impact of the addition of a tumor bed boost to ultrahypofractionated RT on patient QoL has not been extensively reported to date. Materials and methods: QoL was assessed before and after RT and again 3 months later in 24 patients with early-stage breast cancer who underwent adjuvant ultrahypofractionated whole-breast RT (5 fractions of 5.2 Gy), followed by a tumor bed boost (3 fractions of 3 Gy). The EORTC QLQ-C30 and BR23 questionnaires were used to assess patient-reported outcomes (PROs). Patient religiosity and spirituality were evaluated using the QRFPC25 questionnaire. Results: There were no significant differences in either the functional or symptom scores across the designated time points. Although an increase in global health status at 3 months was observed, there was significant variability in patient scores across all time points (Kendall’s W = 0.14; adjusted p-values for multiple comparisons ≥ 0.44). Breast symptom scores also increased over time, especially at 3 months (p = 0.032; χ2 = 6.87), but again this effect was small (Kendall’s W = 0.14, adjusted p ≥ 0.12). Patient spirituality and religiosity were not affected. Conclusion: Overall, QoL, as well as patient spirituality and religiosity, remained stable over time in this FAST-FORWARD plus boost-treated cohort. Further investigation is required to validate these hypothesis-generating findings.

  • Open Access

    Integrating Gold Nanoparticles with Brachytherapy: In Vitro Insights into Radiosensitization in Cervical Cancer

    by Maria Anthi Kouri, Maria-Eleni Kalkou, Kalliopi Platoni, Nikos Kollaros, Kyveli Zourari, Marina Chalkia, George Patatoukas, Aris Spathis, Vassilis Kouloulias, Efstathios Efstathopoulos

    Background/Objectives: Cervical cancer treatment relies heavily on high-dose-rate (HDR) 192Ir brachytherapy; however, therapeutic efficacy remains limited by tumor radioresistance and the inability to escalate dose without increasing toxicity to surrounding healthy tissues. The present study investigates the potential of gold nanoparticles (AuNPs) to enhance radiosensitivity under clinically relevant 192Ir brachytherapy conditions through the combined action of physical dose amplification and radiobiological modulation. Particular emphasis is placed on the unique radiophysical interactions generated by the mixed gamma and secondary beta emissions of 192Ir, which, in the presence of high atomic number nanoparticles, promote localized photoelectric absorption and the emission of low-range secondary electrons, including Auger electrons. The study further aims to determine how AuNPs size and post-irradiation temporal evolution influence radiation-induced cytotoxicity and apoptosis in cervical cancer cell lines, thereby providing a biologically representative model of nanoparticle-assisted brachytherapy. Methods: Clonogenic survival, dose enhancement factor (DEF), and apoptosis were evaluated following irradiation in the presence of 10 nm and 50 nm AuNPs in two independent biological experiments (n = 2). Results: A clear dose-dependent reduction in survival fraction and increase in apoptosis were observed in nanoparticle-treated groups compared with irradiation alone. Radiosensitization demonstrated strong size dependence, with 50 nm AuNPs producing the greatest enhancement, a finding that may reflect size-dependent differences in cellular internalization, intracellular distribution, and nanoscale energy deposition previously established in AuNP studies. Importantly, biological effects intensified at later post-irradiation intervals, demonstrating a sustained temporal evolution of the radiobiological response beyond the initial irradiation event, potentially involving oxidative and other delayed cellular stress mechanisms described in AuNP radiosensitization. Conclusions: These findings demonstrate the capacity of AuNPs to enhance the radiobiological response of cervical cancer cells to 192Ir brachytherapy and identify nanoparticle size and post-irradiation time as important determinants of this effect. They therefore support AuNP-assisted brachytherapy as a promising strategy for further development toward biologically optimized radiotherapy capable of improving tumor response without escalation of the prescribed radiation dose.

  • Open Access

    Gamma passing rates of sequential boost head and neck VMAT treatment plans: complexity metrics and irradiation phase-specific analysis

    by K. Outsikas, G. Patatoukas, M. Chalkia, K. Zourari, N. Kollaros, A. Kougiomtzopoulou, D. Michaletou, V. Kouloulias, K. Platoni

  • Open Access

    From 2D to 3D gamma passing rate tolerance and action limits for patient‐specific quality assurance in volumetric‐modulated arc therapy

    by Christos Zarros, George Patatoukas, Nikos Kollaros, Marina Chalkia, Andromachi Kougioumtzopoulou, Vasilios Kouloulias, Kalliopi Platoni

    Background: Volumetric modulated arc therapy (VMAT) requires an accurate patient‐specific quality assurance (PSQA) program. In clinical practice, this is usually performed using the γ‐index and the two‐dimensional gamma passing rate (2D %GP). A three‐dimensional (3D) index incorporating the patient anatomy could be more useful for the 3D dose distribution verification.Purpose: The current study demonstrates a thorough investigation of VMAT PSQA treatment plans by examining the correlation between 3D Gamma passing rate (%GP) and 2D %GP. The aim was to establish the tolerance limits (TL) and action limits (AL) that could be adopted in clinical practice.Materials and methods: PSQA was performed for 67 head and neck (H&N) and 69 prostate treatment plans, using an appropriate phantom and the γ‐index method. The 3%/2 mm acceptance criterion was used. Treatment plans’ 2D% GP and 3D %GP values were collected and correlated with individual 3D %GP values of planning target volume (PTV) and organs at risk (OARs). Institutional TL and AL of both 2D %GP and 3D %GP were established using 30 prostate and 30 H&N treatment plans, as per recommendations proposed by AAPM TG‐218.Results: A moderate correlation was observed between 2D %GP and 3D %GP of the treatment plans. Τhe correlations demonstrated a stronger association for the 3D %GP than for the 2D %GP with respect to the 3D %GP of the individual structures considered. The TL for the 3D %GP (both plan and individual) and the plans’ 2D %GP were generally more stringent, while the AL showed a wider range compared to the corresponding limits suggested by the TG‐218 protocol for plan 2D %GP.Conclusions: Institution‐specific 3D %GP as well as TL and AL for treatment plan, PTV and OARs could be incorporated in the PSQA procedure in synergy with the 2D evaluation, as they can provide a more‐in‐depth‐view of the treatment quality.


  • Open Access

    Unravelling Quality of Life for Head and Neck Cancer Patients after VMAT Radiation Therapy: Insights from Toxicity, Dosimetry and Symptoms Correlation

    by Panagiota Kiafi, Maria Anthi Kouri, Georgios Patatoukas, Andromachi Kougioumtzopoulou, Marina Chalkia, Ourania Nicolatou-Galitis, Vassilis Kouloulias, Efthimios Kyrodimos, Kalliopi Platoni

    (1) Background: Head and neck cancer treatment, including advanced techniques like Volumetric Modulated Arc Therapy (VMAT), presents challenges for maintaining patient quality of life (QoL). Thus, thoroughly investigating how radiation therapy (RT) affects patients has been proved essential. Derived by that, this study aims to understand the complex interactions between not only RT and QoL but also symptom severity, and treatment-related toxicities in three distinct time points of patient’s treatment; (2) Methods: To achieve that, EORTC-QLQ-C30 and EORTC QLQ-H&N35 questionnaires were used in combination with EORTC_RTOG scoring criteria and Spearman’s rho statistical analysis for 74 patients with cancer undergoing VMAT radiation therapy; (3) Results: The results revealed a significant improvement in the Overall Health Index post-treatment, indicating a temporary decline during therapy followed by subsequent recovery, often surpassing pre-treatment QoL levels. Concurrently a reduction in symptomatology was observed, notably in pain, swallowing difficulties, and dry mouth, aligning with prior research indicating decreased symptom burden post-treatment. However, Spearman’s correlation coefficient analysis at two distinct time points during therapy uncovered varying degrees of correlation between dosimetric data at Organs at Risk (OARs) and reported symptoms, highlighting potential limitations in using QoL questionnaires as sole indicators of treatment efficacy. Our investigation into the correlation between dosimetric data, toxicity, and symptoms focused on the relationship between radiation doses and oral mucositis levels, a common toxicity in head and neck cancer patients. Significant associations were identified between toxicity levels and dosimetric parameters, particularly with OARs such as the parotid glands, oral cavity, and swallowing muscles, underlining the utility of the EORTC method as a reliable toxicity assessment tool; (4) Conclusions: To summarize, current research attempts to underscore the importance of refining QoL assessments for enhanced patient care. The integration of dosimetric data, symptom severity, and treatment-related toxicities in the QoL outcomes of head and neck cancer patients undergoing VMAT radiation therapy, can lead towards the optimization of treatment strategies and the improvement of patient outcomes in future patient-centered radiation therapy practices.


  • Open Access

    The Impact of Nanomedicine on Soft Tissue Sarcoma Treated by Radiotherapy and/or Hyperthermia: A Review

    by Maria-Eleni Zachou, Vassilis Kouloulias, Marina Chalkia, Efstathios Efstathopoulos, Kalliopi Platoni

    This article presents a comprehensive review of nanoparticle-assisted treatment approaches for soft tissue sarcoma (STS). STS, a heterogeneous group of mesenchymal-origin tumors with aggressive behavior and low overall survival rates, necessitates the exploration of innovative therapeutic interventions. In contrast to conventional treatments like surgery, radiotherapy (RT), hyperthermia (HT), and chemotherapy, nanomedicine offers promising advancements in STS management. This review focuses on recent research in nanoparticle applications, including their role in enhancing RT and HT efficacy through improved drug delivery systems, novel radiosensitizers, and imaging agents. Reviewing the current state of nanoparticle-assisted therapies, this paper sheds light on their potential to revolutionize soft tissue sarcoma treatment and improve patient therapy outcomes.


  • Open Access

    Dosimetric comparison and evaluation of two computational algorithms in VMAT treatment plans

    by Maria Tsimpoukelli, George Patatoukas, Marina Chalkia, Nikolaos Kollaros, Andromachi Kougioumtzopoulou, Dimitra Michaletou, Vassilis Kouloulias, Kalliopi Platoni

    Purpose: This study aimed to assess the accuracy and dosimetric impact of the Acuros XB (AXB) algorithm compared to the Anisotropic Analytical Algorithm (AAA) in two situations. First, simple phantom geometries were set and analyzed; moreover, volumetric modulated arc therapy (VMAT) clinical plans for Head & Neck and lung cases were calculated and compared.Methods: First, a phantom study was performed to compare the algorithms with radiochromic EBT3 film doses using one PMMA slab phantom and two others containing foam or air gap. Subsequently, a clinical study was conducted, including 20 Head & Neck and 15 lung cases irradiated with the VMAT technique. The treatment plans calculated by AXB and AAA were evaluated in terms of planning target volume (PTV) coverage (V95%), dose received by relevant organs at risk (OARs), and the impact of using AXB with a grid size of 1 mm. Finally, patient‐specific quality assurance (PSQA) was performed and compared for 17 treatment plans.Results: Phantom dose calculations showed a better agreement of AXB with the film measurements. In the clinical study, AXB plans exhibited lower Conformity Index and PTV V95%, higher maximum PTV dose, and lower mean and minimum PTV doses for all anatomical sites. The most notable differences were detected in regions of intense heterogeneity. AXB predicted lower doses for the OARs, while the calculation time with a grid size of 1 mm was remarkably higher. Regarding PSQA, although AAA was found to exhibit slightly higher gamma passing rates, the difference did not affect the AXB treatment plan quality.Conclusions: AXB demonstrated higher accuracy than AAA in dose calculations of both phantom and clinical conditions, specifically in interface regions, making it suitable for sites with large heterogeneities. Hence, such dosimetric differences between the two algorithms should always be considered in clinical practice.


  • Open Access

    Implementation, Dosimetric Assessment, and Treatment Validation of Knowledge-Based Planning (KBP) Models in VMAT Head and Neck Radiation Oncology

    by Anna-Maria Fanou, Georgios Patatoukas, Marina Chalkia, Nikolaos Kollaros, Andromachi Kougioumtzopoulou, Vassilis Kouloulias, Kalliopi Platoni

    The aim of this study was to evaluate knowledge-based treatment planning (KBP) models in terms of their dosimetry and deliverability and to investigate their clinical benefits. Three H&N KBP models were built utilizing RapidPlan™, based on the dose prescription, which is given according to the planning target volume (PTV). The training set for each model consisted of 43 clinically acceptable volumetric modulated arc therapy (VMAT) plans. Model quality was assessed and compared to the delivered treatment plans using the homogeneity index (HI), conformity index (CI), structure dose difference (PTV, organ at risk—OAR), monitor units, MU factor, and complexity index. Model deliverability was assessed through a patient-specific quality assurance (PSQA) gamma index-based analysis. The dosimetric assessment showed better OAR sparing for the RapidPlan™ plans and for the low- and high-risk PTV, and the HI, and CI were comparable between the clinical and RapidPlan™ plans, while for the intermediate-risk PTV, CI was better for clinical plans. The 2D gamma passing rates for RapidPlan™ plans were similar or better than the clinical ones using the 3%/3 mm gamma-index criterion. Monitor units, the MU factors, and complexity indices were found to be comparable between RapidPlan™ and the clinical plans. Knowledge-based treatment plans can be safely adapted into clinical routines, providing improved plan quality in a time efficient way while minimizing user variability.


  • Open Access

    The Role of Ionizing Radiation for Diagnosis and Treatment against COVID-19: Evidence and Considerations

    by Marina Chalkia, Nikolaos-Achilleas Arkoudis, Emmanouil Maragkoudakis, Stamatis Rallis, Ioanna Tremi, Alexandros G. Georgakilas, Vassilis Kouloulias, Efstathios Efstathopoulos, Kalliopi Platoni

    The Coronavirus disease 2019 (COVID-19) pandemic continues to spread worldwide with over 260 million people infected and more than 5 million deaths, numbers that are escalating on a daily basis. Frontline health workers and scientists diligently fight to alleviate life-threatening symptoms and control the spread of the disease. There is an urgent need for better triage of patients, especially in third world countries, in order to decrease the pressure induced on healthcare facilities. In the struggle to treat life-threatening COVID-19 pneumonia, scientists have debated the clinical use of ionizing radiation (IR). The historical literature dating back to the 1940s contains many reports of successful treatment of pneumonia with IR. In this work, we critically review the literature for the use of IR for both diagnostic and treatment purposes. We identify details including the computed tomography (CT) scanning considerations, the radiobiological basis of IR anti-inflammatory effects, the supportive evidence for low dose radiation therapy (LDRT), and the risks of radiation-induced cancer and cardiac disease associated with LDRT. In this paper, we address concerns regarding the effective management of COVID-19 patients and potential avenues that could provide empirical evidence for the fight against the disease.


  • Open Access

    Stereotactic Arrhythmia Radioablation as a Novel Treatment Approach for Cardiac Arrhythmias: Facts and Limitations

    by Marina Chalkia, Vassilis Kouloulias, Dimitris Tousoulis, Spyridon Deftereos, Dimitris Tsiachris, Dimitrios Vrachatis, Kalliopi Platoni

    Stereotactic ablative radiotherapy (SABR) is highly focused radiation therapy that targets well-demarcated, limited-volume malignant or benign tumors with high accuracy and precision using image guidance. Stereotactic arrhythmia radioablation (STAR) applies SABR to treat cardiac arrhythmias, including ventricular tachycardia (VT) and atrial fibrillation (AF), and has recently been a focus in research. Clinical studies have demonstrated electrophysiologic conduction blockade and histologic fibrosis after STAR, which provides a proof of principle for its potential for treating arrhythmias. This review will present the basic STAR principles, available clinical study outcomes, and how the technique has evolved since the first pre-clinical study. In addition to the clinical workflow, focus will be given on the process for stereotactic radiotherapy Quality Assurance (QA) tests, as well as the need for establishing a standardized QA protocol. Future implications and potential courses of research will also be discussed.