Rivista e Edizione

Volume 28 (2022): Edizione 4 (December 2022)

Volume 28 (2022): Edizione 3 (September 2022)

Volume 28 (2022): Edizione 2 (June 2022)

Volume 28 (2022): Edizione 1 (March 2022)

Volume 27 (2021): Edizione 4 (December 2021)

Volume 27 (2021): Edizione 3 (September 2021)

Volume 27 (2021): Edizione 2 (June 2021)

Volume 27 (2021): Edizione 1 (March 2021)

Volume 26 (2020): Edizione 4 (December 2020)

Volume 26 (2020): Edizione 3 (September 2020)

Volume 26 (2020): Edizione 2 (June 2020)

Volume 26 (2020): Edizione 1 (March 2020)

Volume 25 (2019): Edizione 4 (December 2019)

Volume 25 (2019): Edizione 3 (September 2019)

Volume 25 (2019): Edizione 2 (June 2019)

Volume 25 (2019): Edizione 1 (March 2019)

Volume 24 (2018): Edizione 4 (December 2018)

Volume 24 (2018): Edizione 3 (September 2018)

Volume 24 (2018): Edizione 2 (June 2018)

Volume 24 (2018): Edizione 1 (March 2018)

Volume 23 (2017): Edizione 4 (December 2017)

Volume 23 (2017): Edizione 3 (September 2017)

Volume 23 (2017): Edizione 2 (June 2017)

Volume 23 (2017): Edizione 1 (March 2017)

Volume 22 (2016): Edizione 4 (December 2016)

Volume 22 (2016): Edizione 3 (September 2016)

Volume 22 (2016): Edizione 2 (June 2016)

Volume 22 (2016): Edizione 1 (March 2016)

Volume 21 (2015): Edizione 1 (December 2015)

Volume 20 (2014): Edizione 1 (March 2014)

Volume 19 (2013): Edizione 2 (December 2013)

Volume 19 (2013): Edizione 1 (March 2013)

Volume 18 (2012): Edizione 2 (June 2012)

Volume 18 (2012): Edizione 1 (March 2012)

Volume 17 (2011): Edizione 4 (December 2011)

Volume 17 (2011): Edizione 3 (September 2011)

Volume 17 (2011): Edizione 2 (June 2011)

Volume 17 (2011): Edizione 1 (March 2011)

Volume 16 (2010): Edizione 2 (June 2010)

Volume 16 (2010): Edizione 1 (March 2010)

Volume 15 (2009): Edizione 4 (December 2009)

Volume 15 (2009): Edizione 3 (September 2009)

Volume 15 (2009): Edizione 2 (June 2009)

Volume 15 (2009): Edizione 1 (March 2009)

Volume 14 (2008): Edizione 4 (December 2008)

Volume 14 (2008): Edizione 3 (September 2008)

Volume 14 (2008): Edizione 2 (June 2008)

Volume 14 (2008): Edizione 1 (March 2008)

Volume 13 (2007): Edizione 4 (December 2007)

Volume 13 (2007): Edizione 3 (September 2007)

Volume 13 (2007): Edizione 2 (June 2007)

Volume 13 (2007): Edizione 1 (March 2007)

Dettagli della rivista
Formato
Rivista
eISSN
1898-0309
Pubblicato per la prima volta
30 Dec 2008
Periodo di pubblicazione
4 volte all'anno
Lingue
Inglese

Cerca

Volume 28 (2022): Edizione 3 (September 2022)

Dettagli della rivista
Formato
Rivista
eISSN
1898-0309
Pubblicato per la prima volta
30 Dec 2008
Periodo di pubblicazione
4 volte all'anno
Lingue
Inglese

Cerca

7 Articoli
Accesso libero

Application of therapeutic linear accelerators for the production of radioisotopes used in nuclear medicine

Pubblicato online: 28 Jul 2022
Pagine: 107 - 116

Astratto

Abstract

This review paper summarizes the possibilities of the use of therapeutic linear electron accelerators for the production of radioisotopes for nuclear medicine. This work is based on our published results and the thematically similar papers by other authors, directly related to five medical radioisotopes as 99Mo/99mTc, 198Au, 186Re, 188Re, 117mSn, produced using therapeutic linacs. Our unpublished data relating to the issues discussed have also been used here. In the experiments, two types of radiation were included in the analysis of the radioisotope production process, i.e. the therapeutic twenty-megavolt (20 MV) X-rays generated by Varian linacs and neutron radiation contaminating the therapeutic beam. Thus, the debated radioisotopes are produced in the photonuclear reactions and in the neutron ones. Linear therapeutic accelerators do not allow the production of radioisotopes with high specific activities, but the massive targets can be used instead. Thus, the amount of the produced radioisotopes may be increased. Apart from linear accelerators, more and more often, the production of radioisotopes is carried out in small medical cyclotrons. More such cyclotrons are developed, built, and sold commercially than for scientific research. The radioisotopes produced with the use of therapeutic linacs or cyclotrons can be successfully applied in various laboratory tests and in research.

Parole chiave

  • nuclear medicine
  • radioisotopes
  • therapeutic linacs
Accesso libero

Automatic diagnosis of severity of COVID-19 patients using an ensemble of transfer learning models with convolutional neural networks in CT images

Pubblicato online: 28 Jul 2022
Pagine: 117 - 126

Astratto

Abstract

Introduction: Quantification of lung involvement in COVID-19 using chest Computed tomography (CT) scan can help physicians to evaluate the progression of the disease or treatment response. This paper presents an automatic deep transfer learning ensemble based on pre-trained convolutional neural networks (CNNs) to determine the severity of COVID -19 as normal, mild, moderate, and severe based on the images of the lungs CT.

Material and methods: In this study, two different deep transfer learning strategies were used. In the first procedure, features were extracted from fifteen pre-trained CNNs architectures and then fed into a support vector machine (SVM) classifier. In the second procedure, the pre-trained CNNs were fine-tuned using the chest CT images, and then features were extracted for the purpose of classification by the softmax layer. Finally, an ensemble method was developed based on majority voting of the deep learning outputs to increase the performance of the recognition on each of the two strategies. A dataset of CT scans was collected and then labeled as normal (314), mild (262), moderate (72), and severe (35) for COVID-19 by the consensus of two highly qualified radiologists.

Results: The ensemble of five deep transfer learning outputs named EfficientNetB3, EfficientNetB4, InceptionV3, NasNetMobile, and ResNext50 in the second strategy has better results than the first strategy and also the individual deep transfer learning models in diagnosing the severity of COVID-19 with 85% accuracy.

Conclusions: Our proposed study is well suited for quantifying lung involvement of COVID-19 and can help physicians to monitor the progression of the disease.

Parole chiave

  • severity of COVID-19
  • convolutional neural network
  • ensemble
Accesso libero

Evaluation of the polarity effect of Roos parallel plate ionization chamber in build-up region

Pubblicato online: 23 Aug 2022
Pagine: 127 - 132

Astratto

Abstract

Purpose: Despite widespread studying of the polarity effect of Roos parallel plate ion chamber in electron beams as mentioned in several protocols, no investigations have up till now studied this effect in photon beams in the build-up region. It is important to examine its polarity effect in the build-up region for photon beams, so this is the first work that focuses in to evaluate the polarity effect of the Roos chamber in the surface and build-up region and comparing its effect with other chambers.

Methods: In this study, the Roos chamber was irradiated by a Theratron 780E 60Co beam to a known polarity effect. The Polarity effects of 5×5 up to 35×35 cm2 field sizes at positive and negative polarizing voltages were measured in the build-up region from surface to 0.7 cm in a solid water phantom.

Results: The polarity ratios (PRs) were obtained at 1.020 ± 0.00 and 1.015 ± 0.00 for field sizes 5 × 5 up to 35 × 35 cm2, respectively. For the same fields, the percentage of polarity effects (%PEs) was obtained at 1.99% ± 0.00% and 1.47% ± 0.02%, respectively. The results found that the %PEs decrease with increased field sizes and depths. Moreover, the %PEs exhibited a decrease with an increased percentage surface dose (%SD). The uncertainty of %PE was estimated as 0.01% for all measurements in this study.

Conclusions: As a result, the average %PE of the Roos chamber described here is equal to 0.756% ± 0.013% for all depths and field sizes for the 60Co γ-ray beam. It has introduced a less percentage of polarity effect than other chambers.

Parole chiave

  • Roos chamber
  • polarity effect
  • build-up region
  • cobalt Co
Accesso libero

Automation of slice thickness measurements in computed tomography images of AAPM CT performance phantom using a non-rotational method

Pubblicato online: 23 Aug 2022
Pagine: 133 - 138

Astratto

Abstract

Purpose: The current study proposes a method for automatically measuring slice thickness using a non-rotational method on the middle stair object of the AAPM CT performance phantom image.

Method: The AAPM CT performance phantom was scanned by a GE Healthcare 128-slice CT scanner with nominal slice thicknesses of 0.625, 1.25, 2.5, 3.75, 5, 7.5 and 10 mm. The automated slice thickness was measured as the full width at half maximum (FWHM) of the profile of the middle stair object using a non-rotational method. The non-rotational method avoided rotating the image of the phantom. Instead, the lines to make the profiles were automatically rotated to confirm the stair’s location and rotation. The results of this non-rotational method were compared with those from a previous rotational method.

Results: The slice thicknesses from the non-rotational method were 1.55, 1.86, 3.27, 4.86, 6.58, 7.57, and 9.66 mm for nominal slice thicknesses of 0.625, 1.25, 2.4, 3.75, 5, 7.5, and 10 mm, respectively. By comparison, the slice thicknesses from the rotational method were 1.53, 1.87, 3.32, 4.98, 6.77, 7.75, and 9.80 mm, respectively. The results of the nonrotational method were slightly lower (i.e. 0.25%) than the results of the rotational method for each nominal slice thickness, except for the smallest slice thickness.

Conclusions: An alternative algorithm using a non-rotational method to measure the slice thickness of the middle stair object in the AAPM CT performance phantom was successfully implemented. The slice thicknesses from the nonrotational method results were slightly lower than the rotational method results for each nominal slice thickness, except at the smallest nominal slice thickness (0.625 mm).

Parole chiave

  • computed tomography
  • slice thickness
  • non-rotation method
  • AAPM CT performance phantom
Accesso libero

The influence of the used applicators on organ and target doses for cervical cancer patients treated with HDR brachytherapy

Pubblicato online: 30 Sep 2022
Pagine: 139 - 149

Astratto

Abstract

Introduction: The aim of this work was to study the influence of the applicators used for cervical cancer patients treated with high dose-rate brachytherapy (HDR-BT) in the Maria Sklodowska-Curie National Research Institute of Oncology in Warsaw, Poland on doses in the tumour volumes and organs at risk.

Material and methods: The treatment was carried out using Iridium-192 in 4 fractions (7.5 Gy each) given in weekly intervals. Two types of applicators were used for comparison: fletcher and ring. The standard dose distribution parameters, read from the system Oncentra Brachy (version 4.5, Elekta), for bladder, rectum, and sigmoid (D2 cc) and tumour (HRCTV D100, D98, D90) were studied. Patients were divided into two groups (240 treatment plans) depending on the type of applicator used and into four groups according to the tumour volumes (HR-CTV < 25 cm3 or HR-CTV ≥ 25 cm3). The collected data were analysed using the PQStatSoftware (version 1.8.2).

Results: The treatment plans prepared with all types of applicators fulfil the dose distribution requirements, however, the dose delivered to the tumour using the ring applicator was found to be the highest. For the bladder and sigmoid the optimal dose distribution was obtained when using the fletcher applicator, while for the rectum the ring applicator gave the smallest dose value. The D2 cc parameter for sigmoid obtained for fletcher treatment has smaller values in the case of patients with small tumour volume and for this type of applicator was observed a statistically significant difference when compared with the ring.

Conclusions: The ring applicator gives the optimal parameters of the dose distribution independently on the tumour volume with respect to the fletcher applicator, which is however more often used in clinical practice.

Parole chiave

  • HDR brachytherapy
  • fletcher
  • ring applicator
  • organ and target doses
Accesso libero

Comparison of fulfilling the criteria for critical organs in irradiation of patients with breast cancer using the deep inspiration breath-hold and free breathing techniques

Pubblicato online: 30 Sep 2022
Pagine: 150 - 159

Astratto

Abstract

Introduction: The aim of the study was to evaluate organ-at-risk dose sparing in treatment plans for patients with left-sided breast cancer irradiated with Deep Inspiration Breath Hold (DIBH) and Free Breathing (FB) techniques.

Material and methods: Twenty patients with left-sided breast cancer were analyzed and divided into two groups. Group A included 10 patients with non-metastatic breast cancer, while group B involved 10 patients with metastatic breast cancer spreading to regional lymph nodes. All patients went through the DIBH coaching. For planning purposes, CT scans were obtained in both DIBH and FB. Mean heart dose (Dmean,heart), mean heart volume receiving 50% of the prescribed dose (V50), V20 (V20L.lung), V10 (V10L.lung) and V5 for left lung (V5L.lung), the volume of the PTV receiving a dose greater than or equal to 95% of the prescribed dose (V95 [%]), the maximum point dose (Dmax), and the volume of PTV receiving 107% of the prescribed dose were reported.

Results: In all 20 analyzed pairs of plans, a reduction by more than half in the mean heart dose in DIBH technique plans was achieved, as well as a significant reduction was found in DIBH plans for the heart V50. In 19 patients, the use of the DIBH technique also reduced the volume of the left lung receiving doses of 20 Gy, 10 Gy, and 5 Gy compared to the FB technique.

Conclusions: Dosimetric analysis showed that the free breathing plans don’t fulfill the criteria for a mean heart dose (group B) and the left lung receiving a 20 Gy dose (group A) compared to the DIBH plans. Radiation therapy of left breast cancer with the use of the DIBH technique results in a significant dose reduction in the heart and also reduces the dose in the left lung in the majority of patients, compared to the FB procedure.

Parole chiave

  • breast cancer
  • coronary artery disease
  • deep inspiration breath-hold (DIBH)
  • heart dose
  • lung dose
Accesso libero

Physical aspects of Bragg curve of therapeutic oxygen-ion beam: Monte Carlo simulation

Pubblicato online: 30 Sep 2022
Pagine: 160 - 168

Astratto

Abstract

Introduction: Oxygen (16O) ion beams have been recommended for cancer treatment due to its physical Bragg curve feature and biological property. The goal of this research is to use Monte Carlo simulation to analyze the physical features of the 16O Bragg curve in water and tissue.

Material and methods: In order to determine the benefits and drawbacks of ion beam therapy, Monte Carlo simulation (PHITS code) was used to investigate the interaction and dose deposition properties of oxygen ions beam in water and human tissue medium. A benchmark study for the depth–dose distribution of a 16O ion beam in a water phantom was established using the PHITS code. Bragg’s peak location of 16O ions in water was simulated using the effect of water’s mean ionization potential. The contribution of secondary particles produced by nuclear fragmentation to the total dose has been calculated. The depth and radial dose profiles of 16O, 12C, 4He, and 1H beams were compared.

Results: It was shown that PHITS accurately reproduces the measured Bragg curves. The mean ionization potential of water was estimated. It has been found that secondary particles contribute 10% behind the Bragg peak for 16O energy of 300 MeV/u. The comparison of the depth and radial dose profiles of 16O, 12C, 4He, and 1H beams, shows clearly, that the oxygen beam has the greater deposited dose at Bragg peak and the minor lateral deflection.

Conclusions: The combination of these physical characteristics with radio-biological ones in the case of resistant organs located behind the tumor volume, leads to the conclusion that the 16O ion beams can be used to treat deep-seated hypoxic tumors.

Parole chiave

  • Monte Carlo simulation
  • ion therapy
  • oxygen ion beam
  • nuclear fragmentation
7 Articoli
Accesso libero

Application of therapeutic linear accelerators for the production of radioisotopes used in nuclear medicine

Pubblicato online: 28 Jul 2022
Pagine: 107 - 116

Astratto

Abstract

This review paper summarizes the possibilities of the use of therapeutic linear electron accelerators for the production of radioisotopes for nuclear medicine. This work is based on our published results and the thematically similar papers by other authors, directly related to five medical radioisotopes as 99Mo/99mTc, 198Au, 186Re, 188Re, 117mSn, produced using therapeutic linacs. Our unpublished data relating to the issues discussed have also been used here. In the experiments, two types of radiation were included in the analysis of the radioisotope production process, i.e. the therapeutic twenty-megavolt (20 MV) X-rays generated by Varian linacs and neutron radiation contaminating the therapeutic beam. Thus, the debated radioisotopes are produced in the photonuclear reactions and in the neutron ones. Linear therapeutic accelerators do not allow the production of radioisotopes with high specific activities, but the massive targets can be used instead. Thus, the amount of the produced radioisotopes may be increased. Apart from linear accelerators, more and more often, the production of radioisotopes is carried out in small medical cyclotrons. More such cyclotrons are developed, built, and sold commercially than for scientific research. The radioisotopes produced with the use of therapeutic linacs or cyclotrons can be successfully applied in various laboratory tests and in research.

Parole chiave

  • nuclear medicine
  • radioisotopes
  • therapeutic linacs
Accesso libero

Automatic diagnosis of severity of COVID-19 patients using an ensemble of transfer learning models with convolutional neural networks in CT images

Pubblicato online: 28 Jul 2022
Pagine: 117 - 126

Astratto

Abstract

Introduction: Quantification of lung involvement in COVID-19 using chest Computed tomography (CT) scan can help physicians to evaluate the progression of the disease or treatment response. This paper presents an automatic deep transfer learning ensemble based on pre-trained convolutional neural networks (CNNs) to determine the severity of COVID -19 as normal, mild, moderate, and severe based on the images of the lungs CT.

Material and methods: In this study, two different deep transfer learning strategies were used. In the first procedure, features were extracted from fifteen pre-trained CNNs architectures and then fed into a support vector machine (SVM) classifier. In the second procedure, the pre-trained CNNs were fine-tuned using the chest CT images, and then features were extracted for the purpose of classification by the softmax layer. Finally, an ensemble method was developed based on majority voting of the deep learning outputs to increase the performance of the recognition on each of the two strategies. A dataset of CT scans was collected and then labeled as normal (314), mild (262), moderate (72), and severe (35) for COVID-19 by the consensus of two highly qualified radiologists.

Results: The ensemble of five deep transfer learning outputs named EfficientNetB3, EfficientNetB4, InceptionV3, NasNetMobile, and ResNext50 in the second strategy has better results than the first strategy and also the individual deep transfer learning models in diagnosing the severity of COVID-19 with 85% accuracy.

Conclusions: Our proposed study is well suited for quantifying lung involvement of COVID-19 and can help physicians to monitor the progression of the disease.

Parole chiave

  • severity of COVID-19
  • convolutional neural network
  • ensemble
Accesso libero

Evaluation of the polarity effect of Roos parallel plate ionization chamber in build-up region

Pubblicato online: 23 Aug 2022
Pagine: 127 - 132

Astratto

Abstract

Purpose: Despite widespread studying of the polarity effect of Roos parallel plate ion chamber in electron beams as mentioned in several protocols, no investigations have up till now studied this effect in photon beams in the build-up region. It is important to examine its polarity effect in the build-up region for photon beams, so this is the first work that focuses in to evaluate the polarity effect of the Roos chamber in the surface and build-up region and comparing its effect with other chambers.

Methods: In this study, the Roos chamber was irradiated by a Theratron 780E 60Co beam to a known polarity effect. The Polarity effects of 5×5 up to 35×35 cm2 field sizes at positive and negative polarizing voltages were measured in the build-up region from surface to 0.7 cm in a solid water phantom.

Results: The polarity ratios (PRs) were obtained at 1.020 ± 0.00 and 1.015 ± 0.00 for field sizes 5 × 5 up to 35 × 35 cm2, respectively. For the same fields, the percentage of polarity effects (%PEs) was obtained at 1.99% ± 0.00% and 1.47% ± 0.02%, respectively. The results found that the %PEs decrease with increased field sizes and depths. Moreover, the %PEs exhibited a decrease with an increased percentage surface dose (%SD). The uncertainty of %PE was estimated as 0.01% for all measurements in this study.

Conclusions: As a result, the average %PE of the Roos chamber described here is equal to 0.756% ± 0.013% for all depths and field sizes for the 60Co γ-ray beam. It has introduced a less percentage of polarity effect than other chambers.

Parole chiave

  • Roos chamber
  • polarity effect
  • build-up region
  • cobalt Co
Accesso libero

Automation of slice thickness measurements in computed tomography images of AAPM CT performance phantom using a non-rotational method

Pubblicato online: 23 Aug 2022
Pagine: 133 - 138

Astratto

Abstract

Purpose: The current study proposes a method for automatically measuring slice thickness using a non-rotational method on the middle stair object of the AAPM CT performance phantom image.

Method: The AAPM CT performance phantom was scanned by a GE Healthcare 128-slice CT scanner with nominal slice thicknesses of 0.625, 1.25, 2.5, 3.75, 5, 7.5 and 10 mm. The automated slice thickness was measured as the full width at half maximum (FWHM) of the profile of the middle stair object using a non-rotational method. The non-rotational method avoided rotating the image of the phantom. Instead, the lines to make the profiles were automatically rotated to confirm the stair’s location and rotation. The results of this non-rotational method were compared with those from a previous rotational method.

Results: The slice thicknesses from the non-rotational method were 1.55, 1.86, 3.27, 4.86, 6.58, 7.57, and 9.66 mm for nominal slice thicknesses of 0.625, 1.25, 2.4, 3.75, 5, 7.5, and 10 mm, respectively. By comparison, the slice thicknesses from the rotational method were 1.53, 1.87, 3.32, 4.98, 6.77, 7.75, and 9.80 mm, respectively. The results of the nonrotational method were slightly lower (i.e. 0.25%) than the results of the rotational method for each nominal slice thickness, except for the smallest slice thickness.

Conclusions: An alternative algorithm using a non-rotational method to measure the slice thickness of the middle stair object in the AAPM CT performance phantom was successfully implemented. The slice thicknesses from the nonrotational method results were slightly lower than the rotational method results for each nominal slice thickness, except at the smallest nominal slice thickness (0.625 mm).

Parole chiave

  • computed tomography
  • slice thickness
  • non-rotation method
  • AAPM CT performance phantom
Accesso libero

The influence of the used applicators on organ and target doses for cervical cancer patients treated with HDR brachytherapy

Pubblicato online: 30 Sep 2022
Pagine: 139 - 149

Astratto

Abstract

Introduction: The aim of this work was to study the influence of the applicators used for cervical cancer patients treated with high dose-rate brachytherapy (HDR-BT) in the Maria Sklodowska-Curie National Research Institute of Oncology in Warsaw, Poland on doses in the tumour volumes and organs at risk.

Material and methods: The treatment was carried out using Iridium-192 in 4 fractions (7.5 Gy each) given in weekly intervals. Two types of applicators were used for comparison: fletcher and ring. The standard dose distribution parameters, read from the system Oncentra Brachy (version 4.5, Elekta), for bladder, rectum, and sigmoid (D2 cc) and tumour (HRCTV D100, D98, D90) were studied. Patients were divided into two groups (240 treatment plans) depending on the type of applicator used and into four groups according to the tumour volumes (HR-CTV < 25 cm3 or HR-CTV ≥ 25 cm3). The collected data were analysed using the PQStatSoftware (version 1.8.2).

Results: The treatment plans prepared with all types of applicators fulfil the dose distribution requirements, however, the dose delivered to the tumour using the ring applicator was found to be the highest. For the bladder and sigmoid the optimal dose distribution was obtained when using the fletcher applicator, while for the rectum the ring applicator gave the smallest dose value. The D2 cc parameter for sigmoid obtained for fletcher treatment has smaller values in the case of patients with small tumour volume and for this type of applicator was observed a statistically significant difference when compared with the ring.

Conclusions: The ring applicator gives the optimal parameters of the dose distribution independently on the tumour volume with respect to the fletcher applicator, which is however more often used in clinical practice.

Parole chiave

  • HDR brachytherapy
  • fletcher
  • ring applicator
  • organ and target doses
Accesso libero

Comparison of fulfilling the criteria for critical organs in irradiation of patients with breast cancer using the deep inspiration breath-hold and free breathing techniques

Pubblicato online: 30 Sep 2022
Pagine: 150 - 159

Astratto

Abstract

Introduction: The aim of the study was to evaluate organ-at-risk dose sparing in treatment plans for patients with left-sided breast cancer irradiated with Deep Inspiration Breath Hold (DIBH) and Free Breathing (FB) techniques.

Material and methods: Twenty patients with left-sided breast cancer were analyzed and divided into two groups. Group A included 10 patients with non-metastatic breast cancer, while group B involved 10 patients with metastatic breast cancer spreading to regional lymph nodes. All patients went through the DIBH coaching. For planning purposes, CT scans were obtained in both DIBH and FB. Mean heart dose (Dmean,heart), mean heart volume receiving 50% of the prescribed dose (V50), V20 (V20L.lung), V10 (V10L.lung) and V5 for left lung (V5L.lung), the volume of the PTV receiving a dose greater than or equal to 95% of the prescribed dose (V95 [%]), the maximum point dose (Dmax), and the volume of PTV receiving 107% of the prescribed dose were reported.

Results: In all 20 analyzed pairs of plans, a reduction by more than half in the mean heart dose in DIBH technique plans was achieved, as well as a significant reduction was found in DIBH plans for the heart V50. In 19 patients, the use of the DIBH technique also reduced the volume of the left lung receiving doses of 20 Gy, 10 Gy, and 5 Gy compared to the FB technique.

Conclusions: Dosimetric analysis showed that the free breathing plans don’t fulfill the criteria for a mean heart dose (group B) and the left lung receiving a 20 Gy dose (group A) compared to the DIBH plans. Radiation therapy of left breast cancer with the use of the DIBH technique results in a significant dose reduction in the heart and also reduces the dose in the left lung in the majority of patients, compared to the FB procedure.

Parole chiave

  • breast cancer
  • coronary artery disease
  • deep inspiration breath-hold (DIBH)
  • heart dose
  • lung dose
Accesso libero

Physical aspects of Bragg curve of therapeutic oxygen-ion beam: Monte Carlo simulation

Pubblicato online: 30 Sep 2022
Pagine: 160 - 168

Astratto

Abstract

Introduction: Oxygen (16O) ion beams have been recommended for cancer treatment due to its physical Bragg curve feature and biological property. The goal of this research is to use Monte Carlo simulation to analyze the physical features of the 16O Bragg curve in water and tissue.

Material and methods: In order to determine the benefits and drawbacks of ion beam therapy, Monte Carlo simulation (PHITS code) was used to investigate the interaction and dose deposition properties of oxygen ions beam in water and human tissue medium. A benchmark study for the depth–dose distribution of a 16O ion beam in a water phantom was established using the PHITS code. Bragg’s peak location of 16O ions in water was simulated using the effect of water’s mean ionization potential. The contribution of secondary particles produced by nuclear fragmentation to the total dose has been calculated. The depth and radial dose profiles of 16O, 12C, 4He, and 1H beams were compared.

Results: It was shown that PHITS accurately reproduces the measured Bragg curves. The mean ionization potential of water was estimated. It has been found that secondary particles contribute 10% behind the Bragg peak for 16O energy of 300 MeV/u. The comparison of the depth and radial dose profiles of 16O, 12C, 4He, and 1H beams, shows clearly, that the oxygen beam has the greater deposited dose at Bragg peak and the minor lateral deflection.

Conclusions: The combination of these physical characteristics with radio-biological ones in the case of resistant organs located behind the tumor volume, leads to the conclusion that the 16O ion beams can be used to treat deep-seated hypoxic tumors.

Parole chiave

  • Monte Carlo simulation
  • ion therapy
  • oxygen ion beam
  • nuclear fragmentation

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