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20 pages, 15101 KiB

Open AccessArticle

Electron Absorbed Fractions and S Factors for Intermediate Size Target Volumes: Comparison of Analytic Calculations and Monte Carlo Simulations

by Christina Kotroumpelou, Ioanna Kyriakou, Vladimir Ivanchenko, Sebastien Incerti and Dimitris Emfietzoglou

Appl. Sci. 2024, 14(6), 2275; https://doi.org/10.3390/app14062275 - 08 Mar 2024

Viewed by 484

Abstract

The absorbed fraction and the S factor represent fundamental quantities in MIRD-based dosimetry of radiopharmaceutical therapy (RPT). Although Monte Carlo (MC) simulations represent the gold standard in RPT dosimetry, dose point kernels (DPK) obtained from analytic range–energy relations offer a more practical alternative [...] Read more.

The absorbed fraction and the S factor represent fundamental quantities in MIRD-based dosimetry of radiopharmaceutical therapy (RPT). Although Monte Carlo (MC) simulations represent the gold standard in RPT dosimetry, dose point kernels (DPK) obtained from analytic range–energy relations offer a more practical alternative for charged-particle dosimetry (β- or α-emitters). In this work, we perform DPK- and MC-based calculations of the self-absorbed fractions and S factors for monoenergetic electrons uniformly distributed in intermediate-size target volumes (~mm to cm) relevant to micrometastasis and disseminated disease. Specifically, the aim of the present work is as follows: (i) the development of an analytic range–energy relation, effective over a broad energy range (100 keV–20 MeV) covering most applications of radiotherapeutic interest; (ii) the application of the new formula to DPK-based calculations of the absorbed fraction and S factor and comparison against MC simulations (both published and present work data) as well as the MIRDcell V2.0.16 software, which uses a similar analytic methodology; and (iii) the study of the influence of simulation parameters (step-size, tracking/production cut-off energies, and ionization model) in Geant4-based calculations of S factors. It is shown that the present DPK-based calculations are in excellent agreement (within 1.5%) with the MIRDcell software, while also being in fair agreement with published MC data as well as with the new Geant4 simulations, with average differences of ~20% for the (sub) mm-sized volumes and ~10% for the cm-sized volumes. The effect of the choice of Geant4 simulation parameters was found to be negligible for the examined target volumes (~mm), except for the use of the Penelope ionization model, which may exhibit noticeable discrepancies (up to ~20%) against the Standard and Livermore models. The present work provides quantitative information that may be useful to both the MC- and DPK-based beta dosimetry of micrometastasis and disseminated disease, which represents an important field of application of RPT. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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16 pages, 3127 KiB

Open AccessArticle

Enhancing Soft Tissue Differentiation with Different Dual-Energy CT Systems: A Phantom Study

by Pasqualina Gallo, Andrea D’Alessio, Riccardo Pascuzzo, Salvatore Gallo, Maria Luisa Fumagalli, Ornella Ortenzia, Chiara Tenconi, Claudia Cavatorta, Emanuele Pignoli, Caterina Ghetti, Maria Grazia Bruzzone and Elena De Martin

Appl. Sci. 2024, 14(5), 1724; https://doi.org/10.3390/app14051724 - 20 Feb 2024

Viewed by 544

Abstract

To quantitatively evaluate the possible advantages of quantifying and differentiating various soft tissues using virtual monochromatic images (VMI) derived from different dual-energy computed tomography (DECT) technologies. This study involved four DECT scanners with different technologies. CIRS phantom images were acquired in single-energy (SECT) [...] Read more.

To quantitatively evaluate the possible advantages of quantifying and differentiating various soft tissues using virtual monochromatic images (VMI) derived from different dual-energy computed tomography (DECT) technologies. This study involved four DECT scanners with different technologies. CIRS phantom images were acquired in single-energy (SECT) and DECT modes with each scanner. The analysis focused on five equivalent soft-tissue inserts: adipose, breast, liver, muscle, and bone (200 mg). The signal-to-noise ratio (SNR) was calculated for each equivalent soft-tissue insert. Finally, the contrasts of tissue pairs between DECT and SECT images were compared using Wilcoxon signed-rank tests adjusted for multiple comparisons. Average CT numbers and noise showed a significant difference pattern between DECT with respect to SECT for each CT scanner. Generally, energy levels of 70 keV or higher led to improved SNR in VMI for most of the equivalent soft-tissue inserts. However, energy levels of 40–50 keV showed significantly higher contrasts in most of the equivalent soft-tissue insert pairs. DECT images at low energies, especially at 40–50 keV, outperform SECT images in discriminating soft tissues across all four DECT technologies. The combined use of DECT images reconstructed at different energy levels provides a more comprehensive set of information for diagnostic and/or radiotherapy evaluation compared to SECT. Some differences between scanners are evident, depending on the DECT acquisition technique and reconstruction method. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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14 pages, 3489 KiB

Open AccessArticle

Application of Lotka–Volterra Equations for Homeostatic Response to an Ionizing Radiation Stressor

by Krzysztof Wojciech Fornalski

Appl. Sci. 2023, 13(19), 11077; https://doi.org/10.3390/app131911077 - 08 Oct 2023

Viewed by 1094

Abstract

Every living organism is a physical, complex system which can be modeled by nonlinear dynamical equations in some very narrowed cases. Here we discuss the adoption and potential application of Lotka–Volterra equations (with damping) to simulate, on a very general level, an organism’s [...] Read more.

Every living organism is a physical, complex system which can be modeled by nonlinear dynamical equations in some very narrowed cases. Here we discuss the adoption and potential application of Lotka–Volterra equations (with damping) to simulate, on a very general level, an organism’s response to a dose of ionizing radiation. The step-by-step calculations show how such modeling can be applied to practically every living thing affected by some external stressor. It is presented that Lotka–Volterra prey–predator equations can successfully model the homeostasis (equilibrium) state of the living matter, with balance between detrimental and beneficial factors which interact in the system. It was shown that too large of a radiation dose can break the damping process, making the system unstable, which is analogous to the irreversible transformation of the irradiated cell/organism. On the contrary, too low of a radiation dose makes the damping factor slightly negative, which means that some nonzero low level of ionizing radiation is the most optimal for an organism’s homeostasis. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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11 pages, 2071 KiB

Open AccessArticle

Feasibility of a Patient-Specific Bolus Using the Life-Casting Method for Radiation Therapy

by Jeongho Kim, Jeehoon Park, Beomjun Park, Byungdo Park and Tae-Gyu Kim

Appl. Sci. 2023, 13(17), 9977; https://doi.org/10.3390/app13179977 - 04 Sep 2023

Viewed by 1448

Abstract

Radiation therapy for treating shallow tumors is challenging, necessitating the use of boluses. This study introduces the first application of the life-casting method to fabricate patient-specific bolus molds from gypsum sheets, comparing them with commercial boluses. Our developed boluses reduced the air gap [...] Read more.

Radiation therapy for treating shallow tumors is challenging, necessitating the use of boluses. This study introduces the first application of the life-casting method to fabricate patient-specific bolus molds from gypsum sheets, comparing them with commercial boluses. Our developed boluses reduced the air gap between the skin and bolus by 77.62% compared to that of commercial boluses. In vivo dosimetry using the patient-specific bolus demonstrated better results compared to using a commercial bolus. When using the commercial bolus, the mean %Diff and max %Diff were 1.10 ± 0.61%, respectively, and 2.00% for three-dimensional conformal radiation therapy (3D-CRT) and 7.19 ± 1.90% and 10.14% for volumetric modulated arc therapy (VMAT), respectively. Contrastingly, our developed bolus demonstrated more accurate dose delivery with a mean %Diff and max %Diff of 0.82 ± 0.61% and 1.69% for 3D-CRT and 3.42 ± 1.01% and 5.03% for VMAT, respectively. Furthermore, the standard deviation between the measurements was more than 50% lower when using a patient-specific bolus than when using a commercial bolus. These results show that our bolus reduces air gaps, improves the accuracy of bolus positioning, and enhances the precision of dose delivery compared with the performance of commercial boluses. Therefore, the developed bolus is expected to be valuable in clinical applications. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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12 pages, 2509 KiB

Open AccessArticle

Dosimetric Evaluation of ¹⁷⁷Lu Peptide Receptor Radionuclide Therapy Using GATE and Planet Dose

by Ioanna Stamouli, Thomas Nanos, Konstantinos Chatzipapas, Panagiotis Papadimitroulas, Lydia-Aggeliki Zoglopitou, Theodoros Kalathas, Paraskevi F. Katsakiori, Anna Makridou and George C. Kagadis

Appl. Sci. 2023, 13(17), 9836; https://doi.org/10.3390/app13179836 - 30 Aug 2023

Viewed by 1119

Abstract

This study aimed to compare the commercial dosimetric software Planet^® Dose (version 3.1.1) from DOSIsoft and the open-source toolkit GATE. Dosimetry was performed for six patients receiving 200 mCi of Lutathera^® every 8 weeks for four treatment cycles. For the dose [...] Read more.

This study aimed to compare the commercial dosimetric software Planet^® Dose (version 3.1.1) from DOSIsoft and the open-source toolkit GATE. Dosimetry was performed for six patients receiving 200 mCi of Lutathera^® every 8 weeks for four treatment cycles. For the dose calculation with Planet^®, SPECT/CT images were acquired at 4, 24, 72 and 192 h post-injection. After the registration of all the time points to T0, the organs of interest (OOIs) were segmented. Time-activity curves were produced and the absorbed dose was calculated using the bi- and tri-exponential fitting methods. Regarding GATE simulations, the SPECT images of the 24 h time point were utilized for the radiopharmaceutical biodistribution in the OOIs and the attenuation maps were produced using the CT images. For liver and spleen, the average relative difference between GATE and Planet^® was 9.6% and 11.1% for biexponential and 12.4% and 30.5% for triexponential fitting, respectively. The right and left kidneys showed differences up to 10.7% and 10.4% for the biexponential and up to 60.6% and 11.9% for the triexponential model, respectively. The absorbed dose calculated with GATE, Planet^®(bi-exp) and Planet^®(tri-exp) was in agreement with the literature. The results of the bi-exponential fitting were similar to the GATE-resulted calculations, while the tri-exponential fitting had a higher relative difference. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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11 pages, 385 KiB

Open AccessArticle

First Study of a HEXITEC Detector for Secondary Particle Characterisation during Proton Beam Therapy

by Maria L. Perez-Lara, Jia C. Khong, Matthew D. Wilson, Ben D. Cline and Robert M. Moss

Appl. Sci. 2023, 13(13), 7735; https://doi.org/10.3390/app13137735 - 30 Jun 2023

Viewed by 960

Abstract

Online proton range verification is a rapidly emerging field characterised by its ability to reduce the error margins during proton beam therapy, as it is patient-specific and in vivo. In particular, secondary prompt gamma detection is a promising tool to monitor the dose [...] Read more.

Online proton range verification is a rapidly emerging field characterised by its ability to reduce the error margins during proton beam therapy, as it is patient-specific and in vivo. In particular, secondary prompt gamma detection is a promising tool to monitor the dose delivery. The present research evaluates the capability of a HEXITEC detector to identify the prompt gammas produced during proton beam therapy, and assesses its potential for online range verification. To achieve this, the detector is placed at one side of a water phantom, which is irradiated at different proton energies in the University College London Hospital Proton Centre. For further analysis, Monte Carlo simulations are performed using Geant4 and the same geometry as the experiment. The results show that HEXITEC has the potential to be part of a detection system that could identify secondary prompt gammas within the secondary field produced inside the target, allowing for the in-detector discrimination of these particles via cluster size analysis. The comparison between data sets shows that there is a high level of accuracy between the model and the experimental measurements in terms of secondary flux and charge diffusion inside the detector, which poses the model as a fundamental tool for future optimisation studies. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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13 pages, 2972 KiB

Open AccessArticle

CyberKnife Ultra-Hypofractionated SBRT for Localized Prostate Cancer with Dose Escalation to the Dominant Intraprostatic Lesion: In Silico Planning Study

by Giovanni Carlo Mazzola, Maria Giulia Vincini, Elena Rondi, Giuseppe Ronci, Sabrina Vigorito, Mattia Zaffaroni, Giulia Corrao, Salvatore Gallo, Dario Zerini, Stefano Durante, Francesco Alessandro Mistretta, Stefano Luzzago, Matteo Ferro, Andrea Vavassori, Federica Cattani, Gennaro Musi, Ottavio De Cobelli, Giuseppe Petralia, Roberto Orecchia, Giulia Marvaso and Barbara Alicja Jereczek-Fossa Show full author list Hide full author list

Appl. Sci. 2023, 13(12), 7273; https://doi.org/10.3390/app13127273 - 19 Jun 2023

Viewed by 1743

Abstract

The aim is to evaluate the feasibility of ultra-hypofractionated (UH) SBRT with CyberKnife^® (CK) radiosurgery (Accuray Inc., Sunnyvale, California, USA) for localized prostate cancer (PCa) with a concomitant focal boost to the dominant intraprostatic lesion (DIL). Patients with intermediate/high-risk PCa, with at [...] Read more.

The aim is to evaluate the feasibility of ultra-hypofractionated (UH) SBRT with CyberKnife^® (CK) radiosurgery (Accuray Inc., Sunnyvale, California, USA) for localized prostate cancer (PCa) with a concomitant focal boost to the dominant intraprostatic lesion (DIL). Patients with intermediate/high-risk PCa, with at least one visible DIL on multi-parametric MRI, were included. For each, two CK-SBRT in silico plans were calculated using 95% and 85% isodose lines (CK-95%, CK-85%) and compared with the UH-DWA plan delivered with VERO^®. All plans simulated a SIB prescription of 40 Gy to PTV-DIL and 36.25 Gy to the whole prostate (PTV-prostate) in five fractions every other day. Fifteen patients were considered. All plans reached the primary planning goal (D95% > 95%) and compliance with organs at risk (OARs) constraints. DVH metrics median values increased (p < 0.05) from UH-DWA to CK-85%. The conformity index of PTV-DIL was 1.00 for all techniques, while for PTV-prostate was 0.978, 0.984, and 0.991 for UH-DWA, CK-95%, and CK-85%, respectively. The CK-85% plans were able to reach a maximum dose of 47 Gy to the DIL while respecting OARs constraints. CK-SBRT plus a focal boost to the DIL for localized PCa appears to be feasible. These encouraging dosimetric results are to be confirmed in upcoming clinical trials such as the phase-II “PRO-SPEED” IEO trial. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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11 pages, 1684 KiB

Open AccessArticle

Characterization of Ultra-High-Dose Rate Electron Beams with ElectronFlash Linac

by Lucia Giuliano, Gaia Franciosini, Luigi Palumbo, Lilia Aggar, Marie Dutreix, Luigi Faillace, Vincent Favaudon, Giuseppe Felici, Federica Galante, Andrea Mostacci, Mauro Migliorati, Matteo Pacitti, Annalisa Patriarca and Sophie Heinrich

Appl. Sci. 2023, 13(1), 631; https://doi.org/10.3390/app13010631 - 03 Jan 2023

Cited by 10 | Viewed by 2095

Abstract

Purpose: The electron linac ElectronFlash installed at Institut Curie (Orsay, France) is entirely dedicated to FLASH irradiation for radiobiological and pre-clinical studies. The system was designed to deliver an ultra-high-dose rate per pulse (UHDR) (above

10^{6}

Gy/s) and a very high average [...] Read more.

Purpose: The electron linac ElectronFlash installed at Institut Curie (Orsay, France) is entirely dedicated to FLASH irradiation for radiobiological and pre-clinical studies. The system was designed to deliver an ultra-high-dose rate per pulse (UHDR) (above

10^{6}

Gy/s) and a very high average dose rate at different energies and pulse durations. A campaign of tests and measurements was performed to obtain a full reliable characterizations of the electron beam and of the delivered dose, which are necessary to the radiobiological experiments. Methods: A Faraday cup was used to measure the electron charges in a single RF pulse. The percentage depth dose (PDD) and the transverse dose profiles, at the energies of 5 MeV and 7 MeV, were evaluated employing Gafchromic films EBT-XD for two Poly-methylmethacrylate (PMMA) applicators with irradiation sizes of 30 mm and 120 mm, normally used for in vivo and in vitro experiments, respectively. The results were compared with Monte Carlo (MC) simulations. Results: The measurements were performed during a period of a few months in which the experimental set up was adapted and tuned in order to characterize the electron beam parameters and the values of delivered doses before the radiobiological experiments. The measurements showed that the dose parameters, obtained at the energy of 5 MeV and 7 MeV with different applicators, fulfill the FLASH regime, with a maximum value of an average dose rate of 4750 Gy/s, a maximum dose per pulse of 19 Gy and an instantaneous dose rate up to 4.75

\times 10^{6}

Gy/s. By means of the PMMA applicators, a very good flatness of the dose profiles was obtained at the cost of a reduced total current. The flatness of the large field is reliable and reproducible in radiobiological experiments. The measured PDD and dose profiles are in good agreement with Monte Carlo simulations with more than

95 %

of the gamma-index under the thresholds of 3 mm/

3 %

. Conclusions: The results show that the system can provide UHDR pulses totally satisfying the FLASH requirements with very good performances in terms of beam profile flatness for any size of the fields. The monitoring of electron beams and the measurement of the dose parameters played an important role in the in vivo and in vitro irradiation experiments performed at the Institut Curie laboratory. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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14 pages, 7172 KiB

Open AccessArticle

Theranostic Investigation of Gadolinium-159 for Hepatocellular Carcinoma: Monte Carlo Simulation Study

by Ahmed Sadeq Musa, Muhammad Fahmi Rizal Abdul Hadi, Nabeel Ibrahim Ashour and Nurul Ab. Aziz Hashikin

Appl. Sci. 2022, 12(23), 12396; https://doi.org/10.3390/app122312396 - 03 Dec 2022

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Abstract

Gadolinium-159 (¹⁵⁹Gd) is a beta emitter with appropriate energy for therapeutic application. However, this radioisotope additionally emits gamma rays, enabling the distribution of ¹⁵⁹Gd to be detected by a gamma camera after each therapeutic administration. The current research is innovative [...] Read more.

Gadolinium-159 (¹⁵⁹Gd) is a beta emitter with appropriate energy for therapeutic application. However, this radioisotope additionally emits gamma rays, enabling the distribution of ¹⁵⁹Gd to be detected by a gamma camera after each therapeutic administration. The current research is innovative in the investigation of ¹⁵⁹Gd as a theranostic radioisotope in the radioembolization of HCC using Monte Carlo (MC) simulation. For ¹⁵⁹Gd therapeutic investigation, various patient scenarios including varying tumour involvement (TI), tumour-to-normal liver uptake ratio (T/N), and lung shunting (LS) were simulated using Geant4 MC to estimate the absorbed doses to organs at risk. For ¹⁵⁹Gd planar imaging investigation, the SPECTHead example from GATEContrib (GitHub) was utilized, and inside a liver a tumour was created and placed inside a torso phantom and simulated using GATE MC simulation. The majority of ¹⁵⁹Gd absorbed doses by normal liver and lungs were less than the maximum dose limitations of 70 Gy and 30 Gy, respectively. Absorbed doses to other organs were observed to be below 1 Gy. The utilization of 58 keV and 363.54 keV photopeaks in combination produced optimal planar imaging of ¹⁵⁹Gd. This research gives new insights into the use of ¹⁵⁹Gd as a theranostic radioisotope, with the potential to be used as an Yttrium-90 (⁹⁰Y) alternative for liver radioembolization. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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Review

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30 pages, 896 KiB

Open AccessReview

Molecular Biomarkers for Predicting Cancer Patient Radiosensitivity and Radiotoxicity in Clinical Practice

by Angeliki Gkikoudi, Spyridon A. Kalospyros, Sotiria Triantopoulou, Stella Logotheti, Vasiliki Softa, Constantin Kappas, Kiki Theodorou, Evagelia C. Laiakis, Gina Manda, Georgia I. Terzoudi and Alexandros G. Georgakilas

Appl. Sci. 2023, 13(23), 12564; https://doi.org/10.3390/app132312564 - 21 Nov 2023

Viewed by 1590

Abstract

Radiotherapy (RT) is a major part of cancer treatment. The reported variability in patient response to this modality can interfere with the continuation of best-possible care, promote side effects, and lead to long-term morbidity. Tools to predict a patient’s response to radiation could [...] Read more.

Radiotherapy (RT) is a major part of cancer treatment. The reported variability in patient response to this modality can interfere with the continuation of best-possible care, promote side effects, and lead to long-term morbidity. Tools to predict a patient’s response to radiation could be highly useful in improving therapeutic outcomes while minimizing unnecessary and toxic exposure to radiation. This study investigates the potential of using molecular biomarkers as predictors of radiosensitivity in clinical practice. We review relative studies researching the positive correlation between various molecular biomarkers and patient radiosensitivity, including DNA damage response and repair proteins, inflammation and apoptosis markers, cell cycle regulators, and other biological markers. The clinical perspectives and applicability of these biomarkers in the prediction of radiosensitivity are also critically discussed. Conclusively, we underline the dynamics of molecular biomarkers to improve the efficacy and safety of radiotherapy in clinical practice and highlight the need for further research in this field. Identification of the most prominent markers is crucial for the personalization of therapies entailing ionizing radiation. Full article

(This article belongs to the Special Issue Medical Physics: Latest Advances and Prospects)

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