Radiation, Volume 3, Issue 2 (June 2023) – 5 articles

This work describes the creation and experimental validation of $DoseMRT$, a new software package, and its associated workflow for dose calculations in synchrotron-generated broad beam and microbeam radiation treatment fields. The $DoseMRT$ software package allows users to import CT DICOM datasets into Geant4 for Monte Carlo dose calculations. It also provides basic treatment planning capabilities, simplifying the complexity of performing Geant4 simulations and making our Monte Carlo dose calculation algorithm accessible to a broader range of users. To demonstrate the new package, dose calculations are validated against experimental measurements performed in homogeneous water tank phantoms and the anatomically complex Alderson Radiotherapy Phantom for both broad-beam and microbeam configurations. Additionally, $DoseMRT$ is successfully utilised as the primary method for patient-specific treatment prescription in an in vivo experiment involving tumour-bearing rats at the Imaging and Medical Beamline of the Australian Synchrotron. Full article

Accelerated neutron tests on silicon (Si) and silicon carbide (SiC) power MOSFETs at different temperatures and drain bias voltages were performed at the ChipIr facility (Didcot, UK). A super-junction silicon MOSFET and planar SiC MOSFETs with different technologies made by STMicroelectronics were used. Different test methods were employed to investigate the effects of temperature on neutron susceptibility in power MOSFETs. The destructive tests showed that all investigated devices failed via a single-event burnout (SEB) mechanism. Non-destructive tests conducted by using the power MOSFET as a neutron detector allowed measuring the temperature trend of the deposited charge due to neutron interactions. The results of the destructive tests, in the −50 °C–180 °C temperature range, revealed the lack of a common trend concerning the FIT temperature dependence among the investigated SiC power MOSFETs. Moreover, for some test vehicles, the FIT-temperature curves were dependent on the bias condition. The temperature dependence of the FIT values, observed in some SiC devices, is weaker with respect to that measured in the Si MOSFET. The results of the non-destructive tests showed a good correlation between the temperature trends of the deposited charge with those of FIT data, for both Si and SiC devices. Full article

Background: Stereotactic Radiotherapy (SRT) in pancreatic and biliary tract cancer (PBC) suffers from proximity to any organ(s) at risk (OARs). Some strategies to manage this issue have previously been proposed, such as Simultaneous Integrated Protection (SIP), with the aim of maintaining a biological effective dose prescription while reducing toxicities. We performed a systematic review of the literature about SRT techniques applied in patients with tumor in proximity to OARs, with the aim of testing safety and efficacy. Methods: using PRISMA guidelines, we selected studies from a pool of more than 25,000 articles published from 2010 to 30 January 2023 that explored the use of SRT to deliver targeted treatment for PBC. We then selected the ones referring to decreases in prescription doses (for SRT only) in the area of overlap between planning target volume (PTV) and OARs. Local control (LC) and toxicities being detailed were exclusion criteria for articles. Results: 9 studies were included in our review, considering 368 patients. One-year LC probability ranges between 67% and 98.3% were reported. Late G3 toxicities ranged between 0% and 5.3%, while G4-G5 late toxicities were both reported as 0.3%. Conclusion: prioritizing critical OAR constraints limits severe toxicities while preserving LC in PBC SRT. Improving in-study reporting is essential to confirm these promising results. Full article

Background: Erectile dysfunction (ED) is common after prostate cancer treatment. It has been studied for conventional radiotherapy, but associations in the hypofractionated radiotherapy context are less clear. This study aimed to determine which factors are predicted for worsening ED after highly conformal, modestly hypofractionated radiotherapy to the prostate. Methods: Two hundred and twelve patients treated with 6000 cGy in twenty fractions across four centers were included in this study. Demographic, clinical, and dosimetry factors were then evaluated for post-treatment declines in erectile function using logistic regression and an explainable machine learning-based neural network. Results: 212 patients with a median follow-up of 3.6 years were evaluated. A total of 104 (49%) patients received androgen deprivation therapy. Prior to treatment, 52 (25%) patients were on ED medication. Mean doses to the penile bulb, penile crus, and penile shaft were 2490 (IQR: 1529–3656) cGy, 2095 (1306–3036) cGy, and 444 (313–650) cGy, respectively. Fifty-nine (28%) patients had a worsening of ED after treatment. On multivariable analysis, only the mean dose to the penile shaft [OR >345 vs. ≤345: 4.47 (1.43–13.99); p = 0.010] and pretreatment use of ED medication [OR yes vs. no: 12.5 (5.7–27.5; p < 0.001)] predicted for worsening ED. The neural network confirmed that the penile shaft mean dose and pre-treatment ED medication use are the most important factors in predicting ED. Conclusions: Pre-treatment ED and penile shaft dosimetry are important predictors for ED after hypofractionated radiotherapy for prostate cancer. Full article

This study aimed to evaluate the safety of gadobutrol, a gadolinium-based contrast agent used in medical imaging, by investigating its effect on the nervous system under physiological and inflammatory conditions. Male Sprague Dawley rats were divided randomly into four groups, including gadobutrol, saline, LPS + gadobutrol, and LPS + saline, and were given intraperitoneal injections of gadobutrol (2.5 mmol/kg) or saline for 20 days. Weekly sensorimotor and cognitive behavioral tests were performed over 4 weeks, and Gd concentration in nervous tissues was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Lactate dehydrogenase (LDH) activity was measured to evaluate cytotoxicity, and electromyography (EMG) recordings from the gastrocnemius muscle were also obtained to examine signal transmission in sciatic nerves. The results indicated that gadobutrol did not induce significant behavioral changes under normal conditions. However, when administered along with LPS, the combination led to behavioral dysfunction. ICP-MS analysis revealed a higher concentration of Gd in the cerebrum and spinal cord of gadobutrol + LPS-treated rats, while peripheral nerves showed lower concentrations. In addition, there was a significant increase in LDH activity in the hippocampus of the gadobutrol group. EMG responses to electrical stimulation of the sciatic nerve demonstrated a decreased threshold of nociceptive reflexes in the gadobutrol group. Overall, while gadobutrol may be considered safe under normal physiological conditions, the findings suggest that its safety may be compromised under inflammatory conditions. Full article