Preclinical Model of Stereotactic Ablative Lung Irradiation Using Arc Delivery in the Mouse: Is Fractionation Worthwhile?

Lung stereotactic body radiation therapy is characterized by a reduction in target volumes and the use of severely hypofractionated schedules. Preclinical modeling became possible thanks to rodent-dedicated irradiation devices allowing accurate beam collimation and focal lung exposure. Given that a great majority of publications use single dose exposures, the question we asked in this study was as follows: in incremented preclinical models, is it worth using fractionated protocols or should we continue focusing solely on volume limitation? The left lungs of C57BL/6JRj mice were exposed to ionizing radiation using arc therapy and 3 × 3 mm beam collimation. Three-fraction schedules delivered over a period of 1 week were used with 20, 28, 40, and 50 Gy doses per fraction. Lung tissue opacification, global histological damage and the numbers of type II pneumocytes and club cells were assessed 6 months post-exposure, together with the gene expression of several lung cells and inflammation markers. Only the administration of 3 × 40 Gy or 3 × 50 Gy generated focal lung fibrosis after 6 months, with tissue opacification visible by cone beam computed tomography, tissue scarring and consolidation, decreased club cell numbers and a reactive increase in the number of type II pneumocytes. A fractionation schedule using an arc-therapy-delivered three fractions/1 week regimen with 3 × 3 mm beam requires 40 Gy per fraction for lung fibrosis to develop within 6 months, a reasonable time lapse given the mouse lifespan. A comparison with previously published laboratory data suggests that, in this focal lung irradiation configuration, administering a Biological Effective Dose ≥ 1000 Gy should be recommended to obtain lung fibrosis within 6 months. The need for such a high dose per fraction challenges the appropriateness of using preclinical highly focused fractionation schedules in mice.

Research on X-ray Fluorescence Enhanced Fluoroscopy Imaging Technology

Chest X-ray fluoroscopy is a commonly used medical imaging method, which has a wide range of applications in the diagnosis of lung diseases and other fields. However, due to low contrast and relatively close linear attenuation coefficients, some early small lesions are difficult to detect in time. Using the X-ray fluorescent effect of high atomic number metal elements and metal atom-containing agents that can be enriched in the lesion, the fluoroscopy signal and the fluorescent signal emitted by the metal atoms can be detected at the same time during the fluoroscopy, and the images of the two can be integrated, which can theoretically enhance the contrast between the lesion and the surrounding tissue. Based on GEANT4, this paper conducts Monte Carlo simulations to explore the feasibility and enhancement effects of three enhancement schemes: the pencil beam spot scanning method, cone-beam collimation method, and slit scanning method, and discusses the specific geometric structure and material selection.

A high-throughput assembly of beam-shaping channel-cut monochromators for laboratory high-resolution X-ray diffraction and small-angle X-ray scattering experiments

A four-bounce monochromator assembly composed of Ge(111) and Ge(220) monolithic channel-cut monochromators with V-shaped channels in a quasi-dispersive configuration is presented. The assembly provides an optimal design in terms of the highest transmittance and photon flux density per detector pixel while maintaining high beam collimation. A monochromator assembly optimized for the highest recorded intensity per detector pixel of a linear detector placed 2.5 m behind the assembly was realized and tested by high-resolution X-ray diffraction and small-angle X-ray scattering measurements using a microfocus X-ray source. Conventional symmetric and asymmetric Ge(220) Bartels monochromators were similarly tested and the results were compared. The new assembly provides a transmittance that is an order of magnitude higher and 2.5 times higher than those provided by the symmetric and asymmetric Bartels monochromators, respectively, while the output beam divergence is twice that of the asymmetric Bartels monochromator. These results demonstrate the advantage of the proposed monochromator assembly in cases where the resolution can be partially sacrificed in favour of higher transmittance while still maintaining high beam collimation. Weakly scattering samples such as nanostructures are an example. A general advantage of the new monochromator is a significant reduction in the exposure time required to collect usable experimental data. A comparison of the theoretical and experimental results also reveals the current limitations of the technology of polishing hard-to-reach surfaces in X-ray crystal optics.

Quality Control Assessment of Diagnostic X-Ray Units in Zanzibar, Tanzania

Regular execution of quality control (QC) tests in medical diagnostic X-ray units is primarily important to provide high-quality images and proper diagnoses with least hazard. The performance criteria in diagnostic radiology in Zanzibar Islands, Tanzania were followed in accordance with the QC guidelines, and the values of the measured parameters were compared with the tolerance limits. The study was designed to perform QC tests on the diagnostic X-ray units in governmental and private hospitals. In this study six QC tests (beam alignment, beam collimation, kV reproducibility, half-value layer (HVL), mAs linearity and kV accuracy) were carried out by using beam alignment tool and Unfors non-invasive X-ray test device (Xi R/F&MAM detector). The measured parameters were conducted in two periods, from 2017 to 2018 (14 X-ray units were considered) and from 2019 to 2020 (16 X-ray units were considered). In both periods, the QC test results indicated that 100% of the X-ray units had acceptable HVL≥ 2.3 mm Al at 80 kVp. In the first period (2017−2018), the QC results showed that 78.57% and 85.71% had acceptable beam alignment (≤3% of the focus to image distance) and beam collimation (≤ ± 2 cm). Of the X-ray units evaluated, 85.71% had tolerable kV reproducibility of 5%, and 71.43% had mAs linearity within the tolerance limit of 10%, whereas 85.71% had acceptable kV accuracy within the tolerance limit of 5%. In the second period (2019−2020), the tolerance limits of X-ray units exceeded by 8.04% for kV reproducibility, 8.04% for kV accuracy, 16.07% for mAs linearity, 8.93% for beam alignment and 8.04% for beam collimation. The exceeded tolerance limits could be attributed to the new X-ray units which have full support of service agreements signed during the second period and increase of the compliances with the Tanzania Atomic Energy Act. No 7 of 2003 and its regulations. Results obtained highlight the need to regularly carry out comprehensive QC tests together with routine equipment maintenance.