Implementation of Artificial Intelligence-Based Diabetic Retinopathy Screening in a Tertiary Care Hospital in Quebec: Prospective Validation Study.

Background: Diabetic retinopathy (DR) affects about 25% of people with diabetes in Canada. Early detection of DR is essential for preventing vision loss.

Objective: We evaluated the real-world performance of an artificial intelligence (AI) system that analyzes fundus images for DR screening in a Quebec tertiary care center.

Technical Note: On the analytical proton dose evaluation in compounds and mixtures.

Purpose: By combining the physical processes occurring due to the interaction of protons with matter, analytical theories published so far have provided acceptable models for calculating depth-dose distributions in homogeneous media. As a well-defined and comprehensive theory, the formula derived by Bortfeld models the dose transferred to the target in terms of the parabolic cylinder function. The model also includes three parameters with values specified for an initial proton energy and for the target material.

Technical Note: On the proton range and nuclear interactions in compounds and mixtures.

Purpose: Range and probability of nonelastic nuclear interactions (NNIs) for protons can be found only for a limited number of compounds and mixtures in nuclear data tables, and the proton-related analytical studies are therefore restricted to those materials for which the data are provided in these documents. In this paper, the authors present general solutions for calculating the proton range and probability of NNIs for desired compounds and mixtures.

Methods: Benefiting from the Bragg-Kleeman approximation of mass stopping power, the authors derive a concise formula for calculating the proton range in materials with arbitrary number of constituent elements.

Inhibition of the epidermal growth factor receptor by erlotinib prevents immortalization of human cervical cells by Human Papillomavirus type 16.

The Human Papillomavirus type-16 (HPV-16) E6 and E7 oncogenes are selectively retained and expressed in cervical carcinomas, and expression of E6 and E7 is sufficient to immortalize human cervical epithelial cells. Expression of the epidermal growth factor receptor (EGFR) is often increased in cervical dysplasia and carcinoma, and HPV oncoproteins stimulate cell growth via the EGFR pathway. We found that erlotinib, a specific inhibitor of EGFR tyrosine kinase activity, prevented immortalization of cultured human cervical epithelial cells by the complete HPV-16 genome or the E6/E7 oncogenes.

Creating a spread-out Bragg peak in proton beams.

The model of Bortfeld and Schlegel (1996 Phys. Med. Biol.

Oblique incidence for broad monoenergetic proton beams.

Purpose: The depth dose of a monoenergetic broad parallel proton beam has been modeled in a number of ways, but evidently not yet for oblique incidence. The purpose of this investigation is to find an accurate analytic formula for this case, which can then be used to model the depth dose of a broad beam with an initial Gaussian angular distribution.

Methods: The Bortfeld model of depth dose in a broad normally incident proton beam has been extended to the case of oblique incidence.

Deterministic photon kerma distribution based on the Boltzmann equation for external beam radiation therapy.

A photon transport algorithm for fully three-dimensional radiotherapy treatment planning has been developed based on the discrete ordinates (SN) solution of the Boltzmann equation. The algorithm is characterized by orthogonal adaptive meshes, which place additional points where large gradients occur and a procedure to evaluate the collided flux using the representation of spherical harmonic expansion instead of the summation of the volume-weighted contribution from discrete angles. The Boltzmann equation was solved in the form of SN spatial, energy, and angular discretization with mitigation of ray effects by the first-collision source method.

Three-dimensional electron dose calculation using an improved hybrid pencil beam model.

An improved hybrid-pencil beam model (HPBM) for electron-beam three-dimensional dose calculation has been studied. The model is based on the fact that away from the edges of a large field, the electron distribution function exactly equals that for an infinitely wide electron beam. In the present model, we use the bipartition model to calculate the longitudinal part of the pencil-beam distribution function, and Fermi-Eyges multiple-scattering theory to calculate its transverse part.

Magnetic fields with photon beams: planar-current-induced magnetic fields.

Strong transverse magnetic fields can produce very large dose enhancements and reductions in localized regions of a patient under irradiation by a photon beam. In this work we consider planar-current-induced magnetic fields ("PCIMFs") generated by arbitrary electric currents in one or two parallel planes, and pose two questions: how much arbitrariness is there in specifying a PCIMF, and how can we solve the "inverse problem" of determining the current distribution which generates a chosen PCIMF? We have completely answered both questions, and have applied the general formulas which we have developed to the case of cylindrical symmetry, giving a concrete example of our method. The present work provides the theoretical tools for designing PCIMFs, but a great deal of systematic research will be required in order to understand and design magnetic fields which produce desired distributions of dose enhancement and dose reduction in photon beams treating patients.