[Which photon energy for intensity-modulated radiotherapy and volumetric-modulated arctherapy in 2019?] / Quelle énergie de photons pour la modulation d'intensité et l'arcthérapie volumétrique en 2019 ?

For more than a decade, the majority of radiation oncology centres have been delivering intensity-modulated radiotherapy (then volumetric-modulated arctherapy) with 6 MV photons as their standard of care. This « dogma ¼ had been supported by the usual absence of dosimetric advantages with high-energy photons (15 to 18 MV or more), at least for the planning target volume and the dose received by the adjacent organs at risk, and by the neutron component as soon as the photon energy exceeds 10 MV. Recent data could question such a dogma. First, in 2019, one cannot avoid taking into account the integral dose, delivered outside the treated volume. Actually, most available data show that integral dose is higher with low energy photons (as 6 MV) than with higher energies. Moreover, recent studies have shown that the neutron component at high energies may have been overestimated in the past; in fact, the neutron dose appears to be lower, and sometimes much lower, than the dose we accept for imaging. Finally, a few cohort studies did not show any increase in second cancers incidence after high-energy photon radiotherapy. In such a context, the American Association of Physicists in Medicine (AAPM) TG 158 document, released a few months ago, clearly states that there is a trade-off between high- and low-energy treatments. High-energy therapy is associated with neutron production, while low-energy therapy results in higher stray photon dose. According to the AAPM, « the optimal energy is likely an intermediate such as 10 MV ¼.

A new pencil beam model for photon dose calculations in heterogeneous media.

The pencil beam method is commonly used for dose calculations in intensity-modulated radiation therapy (IMRT). In this study, we have proposed a novel pencil model for calculating photon dose distributions in heterogeneous media. To avoid any oblique kernel-related bias and reduce computation time, dose distributions were computed in a spherical coordinate system based on the pencil kernels of different distances from source to surface (DSS). We employed two different dose calculation methods: the superposition method and the fast Fourier transform convolution (FFTC) method. In order to render the superposition method more accurate, we scaled the depth-directed component by moving the position of the entry point and altering the DSS value for a given beamlet. The lateral components were thus directly corrected by the density scaling method along the spherical shell without taking the densities from the previous layers into account. Significant computation time could be saved by performing the FFTC calculations on each spherical shell, disregarding density changes in the lateral direction. The proposed methods were tested on several phantoms, including lung- and bone-type heterogeneities. We compared them with Monte Carlo (MC) simulation for several field sizes with 6 MV photon beams. Our results revealed mean absolute deviations <1% for the proposed superposition method. Compared to the AAA algorithm, this method improved dose calculation accuracy by at least 0.3% in heterogeneous phantoms. The FFTC method was approximately 40 times faster than the superposition method. However, compared with MC, mean absolute deviations were <3% for the FFTC method.

A prospective study of three diagnostic sonographic methods in differentiation between benign and malignant salivary gland tumours.

OBJECTIVE: The aim of this study was to evaluate the role of three diagnostic sonographic methods, greyscale sonography (GSS), colour Doppler sonography (CDS) and spectral Doppler (SPD), in differentiating between benign and malignant salivary gland (SG) tumours. METHODS: 44 patients with SG masses were examined using GSS, CDS and SPD. The morphological features of each tumour were evaluated using GSS, the distribution and number of detected blood vessels were assessed using CDS, and peak systolic velocity (PSV), resistive index (RI) and pulsatility index (PI) were measured on SPD. All cases underwent excisional biopsy and a definite tissue diagnosis was obtained. RESULTS: Histopathological examination revealed that 28 of the 44 tumours were benign and 16 were malignant. GSS showed that malignant SG tumours had a significantly higher incidence of ill-defined borders and lymph node involvement than benign tumours, but there was no significant difference between benign and malignant SG tumours regarding echogenicity, homogeneity or sonographic shape. CDS demonstrated malignant tumours with significantly higher vascularity and a scattered distribution. Using SPD, malignant tumours had significantly higher PSV, RI and PI compared with benign tumours. CONCLUSION: RI values above 0.7, PI values above 1.2, PSV values above 44.3 cm s(-1), ill-defined borders, lymph node involvement, Grade 2 or 3 vascularity and hilar distribution of blood vessels should alert the clinician to suspect a malignant SG tumour. After consensus on the threshold values of PSV, RI and PI in differentiating benign from malignant SG tumours, these numbers should be incorporated into the software of ultrasound machines to guide the sonographer in his or her analysis.

Human gamma delta T cells amplify IgE production by Epstein-Barr virus-activated B cells.

In summary, these data document that gamma delta T cells regulate B cell differentiation, antibody synthesis, and IgE secretion in EBV-activated B cells. The classical "helper" subset of CD4+ alpha beta T cells, although potent inducers of other Ig isotypes, are not as efficient in augmenting IgE synthesis. However, interactions between alpha beta and gamma delta cells enhance the IgE response further. The precise mechanism by which gamma delta T cells function to augment IgE secretion is under study. It will be important, for example, to determine whether gamma delta T cells, or products of these cells, directly regulate class switching or mediate the clonal expansion of IgE-expressing B cells. In this regard, we ruled out the possibility that IL-4 release alone could replace gamma delta cells in increasing IgE secretion. Finally, we think it is of potential interest that gamma delta cells migrate to skin epithelia as well as gastrointestinal and pulmonary mucosa, sites of invasion by parasitic organisms and contact with allergens. If gamma delta T cells were specifically activated, either directly or indirectly, by these foreign pathogens, then the data presented here might elucidate the cellular basis for the events leading to IgE secretion, a critical step in the immune response to both parasites and allergens.

Method to create and maintain the patency of the bovine mammary papilla.

The patency of mammary papillae was reestablished after surgically induced injury. Perforated prosthetic tubes with affixed Dacron tubing or Teflon strips were implanted in 18 abraded papillae of lactating dairy cows and were secured with sutures. Wound healing was assessed by palpation and visual inspection. All wounds, with one exception, healed by first intention. Machine milking, reinstituted on day 5 after surgery, caused no apparent discomfort. Grossly and histopathologically, all implants stimulated a variable degree of mucosal metaplasia and hyperplasia. Only implants with Teflon strips became anchored by fibrotic invasion. Mastitis, tube migration, and milk fistulas were complications of the procedure.