The application of Geant4 simulation code for brachytherapy treatment

Brachytherapy is a radiotherapeutic modality that makes use of radionuclides to deliver a high radiation dose to a well-defined volume while sparing surrounding healthy structures. At the National Institute for Cancer Research of Genova a High Dose Rate remote afterloading system provides Ir(192) endocavitary brachytherapy treatments. We studied the possibility to use the Geant4 Monte Carlo simulation toolkit in brachytherapy for calculation of complex physical parameters, not directly available by experiment al measurements, used in treatment planning dose deposition models

GEANT4 : a simulation toolkit

Abstract Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics. PACS: 07.05.Tp; 13; 2

Distinct effects of rectum delineation methods in 3D-confromal vs. IMRT treatment planning of prostate cancer

BACKGROUND: The dose distribution to the rectum, delineated as solid organ, rectal wall and rectal surface, in 3D conformal (3D-CRT) and intensity-modulated radiotherapy treatment (IMRT) planning for localized prostate cancer was evaluated. MATERIALS AND METHODS: In a retrospective planning study 3-field, 4-field and IMRT treatment plans were analyzed for ten patients with localized prostate cancer. The dose to the rectum was evaluated based on dose-volume histograms of 1) the entire rectal volume (DVH) 2) manually delineated rectal wall (DWH) 3) rectal wall with 3 mm wall thickness (DWH(3)) 4) and the rectal surface (DSH). The influence of the rectal filling and of the seminal vesicles' anatomy on these dose parameters was investigated. A literature review of the dose-volume relationship for late rectal toxicity was conducted. RESULTS: In 3D-CRT (3-field and 4-field) the dose parameters differed most in the mid-dose region: the DWH showed significantly lower doses to the rectum (8.7% ± 4.2%) compared to the DWH(3 )and the DSH. In IMRT the differences between dose parameters were larger in comparison with 3D-CRT. Differences were statistically significant between DVH and all other dose parameters and between DWH and DSH. Mean doses were increased by 23.6% ± 8.7% in the DSH compared to the DVH in the mid-dose region. Furthermore, both the rectal filling and the anatomy of the seminal vesicles influenced the relationship between the dose parameters: a significant correlation of the difference between DVH and DWH and the rectal volume was seen in IMRT treatment. DISCUSSION: The method of delineating the rectum significantly influenced the dose representation in the dose-volume histogram. This effect was pronounced in IMRT treatment planning compared to 3D-CRT. For integration of dose-volume parameters from the literature into clinical practice these results have to be considered

Bioactive glass-derived trabecular coating: a smart solution for enhancing osteointegration of prosthetic elements

In this work, the use of foam-like glass-ceramic scaffolds as trabecular coatings on ceramic prosthetic devices to enhance implant osteointegration is proposed. The feasibility of this innovative device was explored in a simplified, flat geometry: glass-ceramic scaffolds, prepared by polymeric sponge replication and mimicking the trabecular architecture of cancellous bone, were joined to alumina square substrates by a dense glass coating (interlayer). The role played by different formulations of starting glasses was examined, with particular care to the effect on the mechanical properties and bioactivity of the final coating. Microindentations at the coating/substrate interface and tensile tests were performed to evaluate the bonding strength between the sample's components. In vitro bioactive behaviour was assessed by soaking in simulated body fluid and evaluating the apatite formation on the surface and inside the pores of the trabecular coating. The concepts disclosed in the present study can have a significant impact in the field of implantable devices, suggesting a valuable alternative to traditional, often invasive bone-prosthesis fixatio

Induction chemotherapy followed by concurrent standard radiotherapy and daily low-dose cisplatin in locally advanced non-small-cell lung cancer

Both induction chemotherapy and concurrent low-dose cisplatin have been shown to improve results of thoracic irradiation in the treatment of locally advanced non-small-cell lung cancer (NSCLC). This phase II study was designed to investigate activity and feasibility of a novel chemoradiation regimen consisting of induction chemotherapy followed by standard radiotherapy and concurrent daily low-dose cisplatin. Previously untreated patients with histologically/cytologically proven unresectable stage IIIA/B NSCLC were eligible. Induction chemotherapy consisted of vinblastine 5 mg m−2 intravenously (i.v.) on days 1, 8, 15, 22 and 29, and cisplatin 100 mg m−2 i.v. on days 1 and 22 followed by continuous radiotherapy (60 Gy in 30 fractions) given concurrently with daily cisplatin at a dose of 5 mg m−2 i.v. Thirty-two patients were enrolled. Major toxicity during induction chemotherapy was haematological: grade III–IV leukopenia was observed in 31% and grade II anaemia in 16% of the patients. The most common severe toxicity during concurrent chemoradiation consisted of grade III leukopenia (21% of the patients); grade III oesophagitis occurred in only two patients and pulmonary toxicity in one patient who died of this complication. Eighteen of 32 patients (56%, 95% CI 38–73%) had a major response (11 partial response, seven complete response). With a median follow-up of 38.4 months, the median survival was 12.5 months and the actuarial survival rates at 1, 2 and 3 years were 52%, 26% and 19% respectively. The median event-free survival was 8.3 months with a probability of 40%, 23% and 20% at 1, 2 and 3 years respectively. Induction chemotherapy followed by concurrent daily low-dose cisplatin and thoracic irradiation, in patients with locally advanced NSCLC, is active and feasible with minimal non-haematological toxicity. Long-term survival results are promising and appear to be similar to those of more toxic chemoradiation regimens, warranting further testing of this novel chemoradiation strategy. © 1999 Cancer Research Campaig

Inter-observer variability in contouring the penile bulb on CT images for prostate cancer treatment planning

Several investigations have recently suggested the existence of a correlation between the dose received by the penile bulb (PB) and the risk of erectile dysfunction (ED) after radical radiotherapy for clinically localized prostate carcinoma

GEANT4--a simulation toolkikt

Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics

Ionospheric response modeling under eclipse conditions: Evaluation of 14 December 2020, total solar eclipse prediction over the South American sector

In this work, we evaluate the SUPIM-INPE model prediction of the 14 December 2020, total solar eclipse over the South American continent. We compare the predictions with data from multiple instruments for monitoring the ionosphere and with different obscuration percentages (i.e., Jicamarca, 12.0°S, 76.8°W, 17%; Tucumán 26.9°S, 65.4° W, 49%; Chillán 36.6°S, 72.0°W; and Bahía Blanca, 38.7°S, 62.3°W, reach 95% obscuration) due to the eclipse. The analysis is done under total eclipse conditions and non-total eclipse conditions. Results obtained suggest that the model was able to reproduce with high accuracy both the daily variation and the eclipse impacts of E and F1 layers in the majority of the stations evaluated (except in Jicamarca station). The comparison at the F2 layer indicates small differences (<7.8%) between the predictions and observations at all stations during the eclipse periods. Additionally, statistical metrics reinforce the conclusion of a good performance of the model. Predicted and calibrated Total Electron Content (TEC, using 3 different techniques) are also compared. Results show that, although none of the selected TEC calibration methods have a good agreement with the SUPIM-INPE prediction, they exhibit similar trends in most of the cases. We also analyze data from the Jicamarca Incoherent Scatter Radar (ISR), and Swarm-A and GOLD missions. The electron temperature changes observed in ISR and Swarm-A are underestimated by the prediction. Also, important changes in the O/N2 ratio due to the eclipse, have been observed with GOLD mission data. Thus, future versions of the SUPIM-INPE model for eclipse conditions should consider effects on thermospheric winds and changes in composition, specifically in the O/N2 ratio