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Loredana Marcu

University of Oradea, Faculty of Science, Faculty Member

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Loredana Marcu is currently a Professor of Medical Physics at the University of Oradea, Romania and holds affiliation with the University of Adelaide, Australia.
Her current interests include modelling of tumour growth and behaviour during treatment, the investigation of the role of Positron Emission Tomography in evaluating tumour hypoxia, the impact of cancer stem cells on tumour response to radiotherapy, and targeted particle therapies.
Currently she is the vice-president of the Romanian College of Medical Physicists.

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Papers by Loredana Marcu

The Effect of Accelerated Repopulation on Altered Fractionation Schedules in Head and Neck Cancers

The Role of Post-implant Dosimetry in the Quality Assessment of Prostate Implants: The RAH Experience

Australasian Physical Engineering Sciences in Medicine, Dec 1, 2006

The quality of a prostate implant using radioactive I-125 seeds can be assessed by performing pos... more The quality of a prostate implant using radioactive I-125 seeds can be assessed by performing post-implant dosimetry, which therefore has to be a reliable evaluation tool. At the RAH, we have noticed large variations in post-implant dosimetric parameters compared to the pre-implant data. The purpose of this study was to investigate the cause of these differences. Post-implant dosimetry was performed 4 weeks after implant on 15 prostate cancer patients. The CT images of the pelvis were exported to the planning system, where contouring of the target (prostate) was executed by 6 clinicians, followed by the post-implant dosimetry performed by a physicist. Pre-and post-implant dosimetric parameters were analyzed and compared. The average target volume based on the ultrasound measurements was 35.8 cc. Post-implant CT volumes were determined and averaged over the 15 patients by each clinician, and their average values vary from 28.9 cc to 67.9 cc. Beside the under/overestimation of the target on the CT there was also a "shift" in the target base on the ultrasound image. By comparing pre-implant and post-implant dosimetric parameters we have encountered a significant discrepancy between target volumes based on ultrasound image and CT image. It was concluded that the accuracy of target coverage was partially connected to the poorer quality of the CT image compared to the ultrasound scan, patient's anatomy, but mostly to the poor implantation of the base.

172 Patient dose due to electronic portal imaging

Radiother Oncol, 2006

Deterministic modelling of kinetics and radiobiology of radiation-cisplatin interaction in the treatment of head and neck cancers

Science education: the need for an interdisciplinary approach

With today's evolving science and technology, there is a desperate need for retailoring science e... more With today's evolving science and technology, there is a desperate need for retailoring science education. Whether biology or physics, chemistry or computing, mathematics or engineering, one should seek for interaction between disciplines not only at research level but also at teaching levels. The term 'interdisciplinary' is increasingly gaining meaning for the new generation of researchers and educators as the novel approaches to all areas of science are based on multidisciplinary methods. Fields such as medical physics, biochemistry, computational biology, bioengineering, physical chemistry, just to mention some, are a valid proof of the need for interaction between sciences. Often students are confused regarding their future, as they are not aware of the applicative side of their chosen discipline. Furthermore, both undergraduate and postgraduate students encounter frequent gaps in their knowledge because of the lack of coordination and interaction between disciplines. These hiccups in the educational system could be overcome through a better organization of curriculum. An example of interdisciplinary approach in science education is medical physics. A medical physicist must have a multidisciplinary vision of physics, otherwise the goals of this developing area are not met. The aim of the present talk is to illustrate the branching science of medical physics, the need for its correlation with molecular biology, chemistry, computing, mathematics and technology, and to underline its ultimate goal: to be of service, as an adjuvant field, to the novel areas of medicine.

Modelling of post irradiation accelerated repopulation in squamous cell carcinomas

Physics in Medicine and Biology

The mechanisms postulated to be responsible for the accelerated repopulation of squamous cell car... more The mechanisms postulated to be responsible for the accelerated repopulation of squamous cell carcinomas during radiotherapy are the loss of asymmetry of stem cell division, acceleration of stem cell division, abortive division and/or recruitment of the non-cycling cell with proliferative capacity. Although accelerated repopulation was observed with recruitment and accelerated cell cycles, it was not sufficient to cause an observable change to the survival curve. However, modelling the loss of asymmetry in stem cell division has reshaped the curve with a &#39;growth&#39; shoulder. Cell recruitment was not found to be a major contributor to accelerated tumour repopulation. A more significant contribution was provided through the multiplication of surviving tumour stem cells during radiotherapy, by reducing their cell cycle time, and due to loss of asymmetry of stem cell division.

Determination of cell cycle phase-specific α parameters for squamous cell carcinomas of the head and neck

Purpose: The derivation of cell cycle phase-specific alpha parameters and the study of the influe... more

The radiobiology of head and neck cancers

ABSTRACT

Risk of rectal second cancer following prostate radiotherapy

Cellular bystander effects and radiation hormesis

Bystander effects describe the effects of extracellular mediators from irradiated cells on neighb... more Bystander effects describe the effects of extracellular mediators from irradiated cells on neighbouring non-irradiated cells resulting in radiation-induced effects in unirradiated cells. Although the underlying mechanisms are largely unknown, it is widely recognised that two types of cellular communication (i.e. via gap junctions and/or release of molecular messengers into the extracellular environment) play an essential role. Additionally, the effects can be significantly modulated by parameters such as cell type, cell-cycle stage and cell density. Some of the common bystander effects or biological end points which are evidenced after low-dose irradiation are: chromosomal instability, cell killing and delayed cell death, mutagenesis, micronucleus formation, gene and protein expression changes. Through these end points it is likely that bystander effects can be both detrimental and beneficial. By increasing mutation levels of cells bystander effects increase the likelihood of genetic defects and in turn cancer. On the other hand by removing damaged cells from the population and preventing the growth of cancer cells, bystander effects are beneficial.

Assessment of normal tissue complications and second cancer risk following prostate cancer irradiation

There are various radiotherapy modalities that can be chosen for treatment of prostate cancer. Th... more There are various radiotherapy modalities that can be chosen for treatment of prostate cancer. The main therapeutic aim of all radiotherapy treatment including prostate is to maximize damage to the tumour and, at the same time, damaging of the surrounding normal tissues must be kept as small as possible. During a process of treatment planning, Tumour Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) are usually assessed to maximize the therapeutic ratio of that treatment modality. However, there is another factor which should also be taken into consideration when the radiotherapy is used for prostate treatment: the risk of developing a fatal second (primary) cancer. There is a number of reports that indicated an elevation in the risk of second cancer of various organs following prostate cancer irradiation, for example, lung, bladder, skin and breast. It was reported in literature that approximately 6 -7% of prostate cancer patients might develop second cancer following radiotherapy. Although results from some retrospective studies showed that the incidence of second cancers in prostate cancer patients who received radiation treatment is lower than or equal to the baseline, the risk of developing a second cancer in some organs has been significantly elevated. This risk, in association with each available treatment modality for prostate cancer, has not been investigated to this date thoroughly. This review intends to demonstrate such association as found in various reports and also to show a possible approach to assess this risk.

The role of scientific journals in disseminating cancer research in the 21st century

The onset of tumour repopulation after radiotherapy in theoretical and in vitro models

Recent advances and research updates in medical physics and radiobiology

Tumour Repopulation During Treatment for Head and Neck Cancer: Clinical Evidence, Mechanisms and Minimizing Strategies

Recent Advances in Brachytherapy: Overview and Brachytherapy for Specific Treatment Sites

Contemporary issues in head and neck cancer management

While the management of head and neck cancer has evolved over the last few decades, there are sti... more While the management of head and neck cancer has evolved over the last few decades, there are still several challenges and unanswered questions that need solutions. This book is a small compilation of some topical aspects regarding head and neck cancer treatment, including the etiology of HPV-positive oropharyngeal cancers and risk factors in the young population, the challenge of surgical margin definition and the perennial problem of systemic treatment due to distant metastases. Radiobiological aspects are also covered through the “Rs” of radiotherapy, with a couple of chapters being dedicated to radioresistance and tumour microenvironment. Contemporary issues in head and neck cancer management comes as an addition to the existing literature that aims to tackle this radiobiologically challenging tumour.

In silico Repopulation Model of Various Tumour Cells during Treatment Breaks in Head and Neck Cancer Radiotherapy

Advanced head and neck cancers are aggressive tumours, which require aggressive treatment. Treatm... more Advanced head and neck cancers are aggressive tumours, which require aggressive treatment. Treatment efficiency is often hindered by cancer cell repopulation during radiotherapy, which is due to various mechanisms triggered by the loss of tumour cells and involves both stem and differentiated cells. The aim of the current paper is to present in silico simulations of radiotherapy schedules on a virtual head and neck tumour grown with biologically realistic kinetic parameters. Using the linear quadratic formalism of cell survival after radiotherapy, altered fractionation schedules employing various treatment breaks for normal tissue recovery are simulated and repopulation mechanism implemented in order to evaluate the impact of various cancer cell contribution on tumour behaviour during irradiation. The model has shown that the timing of treatment breaks is an important factor influencing tumour control in rapidly proliferating tissues such as squamous cell carcinomas of the head and ...

Supplementary Table

Evaluation of physician eye lens doses during permanent seed implant brachytherapy for prostate cancer

Journal of radiological protection : official journal of the Society for Radiological Protection, 2012

Treatment of low grade prostate cancer with permanent implant of radioactive seeds has become one... more Treatment of low grade prostate cancer with permanent implant of radioactive seeds has become one of the most common brachytherapy procedures in use today. The implant procedure is usually performed with fluoroscopy image guidance to ensure that the seeds are deployed in the planned locations. In this situation the physician performing the transperineal implant is required to be close to the fluoroscopy unit and dose to the eye lens may be of concern. In 1991 the International Commission on Radiological Protection (ICRP) provided a recommended dose limit of 150 mSv yr(-1) for occupational exposures to the lens of the eye. With more long term follow-up data, this limit was revised in 2011 to 20 mSv yr(-1). With this revised limit in mind, we have investigated the dose to the lens of the eye received by physicians during prostate brachytherapy seed implantation. By making an approximation of annual workload, we have related the dose received to the annual background dose. Through clin...

The Effect of Accelerated Repopulation on Altered Fractionation Schedules in Head and Neck Cancers

The Role of Post-implant Dosimetry in the Quality Assessment of Prostate Implants: The RAH Experience

Australasian Physical Engineering Sciences in Medicine, Dec 1, 2006

The quality of a prostate implant using radioactive I-125 seeds can be assessed by performing pos... more The quality of a prostate implant using radioactive I-125 seeds can be assessed by performing post-implant dosimetry, which therefore has to be a reliable evaluation tool. At the RAH, we have noticed large variations in post-implant dosimetric parameters compared to the pre-implant data. The purpose of this study was to investigate the cause of these differences. Post-implant dosimetry was performed 4 weeks after implant on 15 prostate cancer patients. The CT images of the pelvis were exported to the planning system, where contouring of the target (prostate) was executed by 6 clinicians, followed by the post-implant dosimetry performed by a physicist. Pre-and post-implant dosimetric parameters were analyzed and compared. The average target volume based on the ultrasound measurements was 35.8 cc. Post-implant CT volumes were determined and averaged over the 15 patients by each clinician, and their average values vary from 28.9 cc to 67.9 cc. Beside the under/overestimation of the target on the CT there was also a "shift" in the target base on the ultrasound image. By comparing pre-implant and post-implant dosimetric parameters we have encountered a significant discrepancy between target volumes based on ultrasound image and CT image. It was concluded that the accuracy of target coverage was partially connected to the poorer quality of the CT image compared to the ultrasound scan, patient's anatomy, but mostly to the poor implantation of the base.

172 Patient dose due to electronic portal imaging

Radiother Oncol, 2006

Deterministic modelling of kinetics and radiobiology of radiation-cisplatin interaction in the treatment of head and neck cancers

Science education: the need for an interdisciplinary approach

With today's evolving science and technology, there is a desperate need for retailoring science e... more With today's evolving science and technology, there is a desperate need for retailoring science education. Whether biology or physics, chemistry or computing, mathematics or engineering, one should seek for interaction between disciplines not only at research level but also at teaching levels. The term 'interdisciplinary' is increasingly gaining meaning for the new generation of researchers and educators as the novel approaches to all areas of science are based on multidisciplinary methods. Fields such as medical physics, biochemistry, computational biology, bioengineering, physical chemistry, just to mention some, are a valid proof of the need for interaction between sciences. Often students are confused regarding their future, as they are not aware of the applicative side of their chosen discipline. Furthermore, both undergraduate and postgraduate students encounter frequent gaps in their knowledge because of the lack of coordination and interaction between disciplines. These hiccups in the educational system could be overcome through a better organization of curriculum. An example of interdisciplinary approach in science education is medical physics. A medical physicist must have a multidisciplinary vision of physics, otherwise the goals of this developing area are not met. The aim of the present talk is to illustrate the branching science of medical physics, the need for its correlation with molecular biology, chemistry, computing, mathematics and technology, and to underline its ultimate goal: to be of service, as an adjuvant field, to the novel areas of medicine.

Modelling of post irradiation accelerated repopulation in squamous cell carcinomas

Physics in Medicine and Biology

The mechanisms postulated to be responsible for the accelerated repopulation of squamous cell car... more The mechanisms postulated to be responsible for the accelerated repopulation of squamous cell carcinomas during radiotherapy are the loss of asymmetry of stem cell division, acceleration of stem cell division, abortive division and/or recruitment of the non-cycling cell with proliferative capacity. Although accelerated repopulation was observed with recruitment and accelerated cell cycles, it was not sufficient to cause an observable change to the survival curve. However, modelling the loss of asymmetry in stem cell division has reshaped the curve with a &#39;growth&#39; shoulder. Cell recruitment was not found to be a major contributor to accelerated tumour repopulation. A more significant contribution was provided through the multiplication of surviving tumour stem cells during radiotherapy, by reducing their cell cycle time, and due to loss of asymmetry of stem cell division.

Determination of cell cycle phase-specific α parameters for squamous cell carcinomas of the head and neck

Purpose: The derivation of cell cycle phase-specific alpha parameters and the study of the influe... more

The radiobiology of head and neck cancers

ABSTRACT

Risk of rectal second cancer following prostate radiotherapy

Cellular bystander effects and radiation hormesis

Bystander effects describe the effects of extracellular mediators from irradiated cells on neighb... more Bystander effects describe the effects of extracellular mediators from irradiated cells on neighbouring non-irradiated cells resulting in radiation-induced effects in unirradiated cells. Although the underlying mechanisms are largely unknown, it is widely recognised that two types of cellular communication (i.e. via gap junctions and/or release of molecular messengers into the extracellular environment) play an essential role. Additionally, the effects can be significantly modulated by parameters such as cell type, cell-cycle stage and cell density. Some of the common bystander effects or biological end points which are evidenced after low-dose irradiation are: chromosomal instability, cell killing and delayed cell death, mutagenesis, micronucleus formation, gene and protein expression changes. Through these end points it is likely that bystander effects can be both detrimental and beneficial. By increasing mutation levels of cells bystander effects increase the likelihood of genetic defects and in turn cancer. On the other hand by removing damaged cells from the population and preventing the growth of cancer cells, bystander effects are beneficial.

Assessment of normal tissue complications and second cancer risk following prostate cancer irradiation

There are various radiotherapy modalities that can be chosen for treatment of prostate cancer. Th... more There are various radiotherapy modalities that can be chosen for treatment of prostate cancer. The main therapeutic aim of all radiotherapy treatment including prostate is to maximize damage to the tumour and, at the same time, damaging of the surrounding normal tissues must be kept as small as possible. During a process of treatment planning, Tumour Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) are usually assessed to maximize the therapeutic ratio of that treatment modality. However, there is another factor which should also be taken into consideration when the radiotherapy is used for prostate treatment: the risk of developing a fatal second (primary) cancer. There is a number of reports that indicated an elevation in the risk of second cancer of various organs following prostate cancer irradiation, for example, lung, bladder, skin and breast. It was reported in literature that approximately 6 -7% of prostate cancer patients might develop second cancer following radiotherapy. Although results from some retrospective studies showed that the incidence of second cancers in prostate cancer patients who received radiation treatment is lower than or equal to the baseline, the risk of developing a second cancer in some organs has been significantly elevated. This risk, in association with each available treatment modality for prostate cancer, has not been investigated to this date thoroughly. This review intends to demonstrate such association as found in various reports and also to show a possible approach to assess this risk.

The role of scientific journals in disseminating cancer research in the 21st century

The onset of tumour repopulation after radiotherapy in theoretical and in vitro models

Recent advances and research updates in medical physics and radiobiology

Tumour Repopulation During Treatment for Head and Neck Cancer: Clinical Evidence, Mechanisms and Minimizing Strategies

Recent Advances in Brachytherapy: Overview and Brachytherapy for Specific Treatment Sites

Contemporary issues in head and neck cancer management

While the management of head and neck cancer has evolved over the last few decades, there are sti... more While the management of head and neck cancer has evolved over the last few decades, there are still several challenges and unanswered questions that need solutions. This book is a small compilation of some topical aspects regarding head and neck cancer treatment, including the etiology of HPV-positive oropharyngeal cancers and risk factors in the young population, the challenge of surgical margin definition and the perennial problem of systemic treatment due to distant metastases. Radiobiological aspects are also covered through the “Rs” of radiotherapy, with a couple of chapters being dedicated to radioresistance and tumour microenvironment. Contemporary issues in head and neck cancer management comes as an addition to the existing literature that aims to tackle this radiobiologically challenging tumour.

In silico Repopulation Model of Various Tumour Cells during Treatment Breaks in Head and Neck Cancer Radiotherapy

Advanced head and neck cancers are aggressive tumours, which require aggressive treatment. Treatm... more Advanced head and neck cancers are aggressive tumours, which require aggressive treatment. Treatment efficiency is often hindered by cancer cell repopulation during radiotherapy, which is due to various mechanisms triggered by the loss of tumour cells and involves both stem and differentiated cells. The aim of the current paper is to present in silico simulations of radiotherapy schedules on a virtual head and neck tumour grown with biologically realistic kinetic parameters. Using the linear quadratic formalism of cell survival after radiotherapy, altered fractionation schedules employing various treatment breaks for normal tissue recovery are simulated and repopulation mechanism implemented in order to evaluate the impact of various cancer cell contribution on tumour behaviour during irradiation. The model has shown that the timing of treatment breaks is an important factor influencing tumour control in rapidly proliferating tissues such as squamous cell carcinomas of the head and ...

Supplementary Table

Evaluation of physician eye lens doses during permanent seed implant brachytherapy for prostate cancer

Journal of radiological protection : official journal of the Society for Radiological Protection, 2012

Treatment of low grade prostate cancer with permanent implant of radioactive seeds has become one... more Treatment of low grade prostate cancer with permanent implant of radioactive seeds has become one of the most common brachytherapy procedures in use today. The implant procedure is usually performed with fluoroscopy image guidance to ensure that the seeds are deployed in the planned locations. In this situation the physician performing the transperineal implant is required to be close to the fluoroscopy unit and dose to the eye lens may be of concern. In 1991 the International Commission on Radiological Protection (ICRP) provided a recommended dose limit of 150 mSv yr(-1) for occupational exposures to the lens of the eye. With more long term follow-up data, this limit was revised in 2011 to 20 mSv yr(-1). With this revised limit in mind, we have investigated the dose to the lens of the eye received by physicians during prostate brachytherapy seed implantation. By making an approximation of annual workload, we have related the dose received to the annual background dose. Through clin...