Mite bites, comet signs and possible mammary prosthesis rejection after returning to a vacation home: a diagnostic challenge.

Pyemotes ventricosus is a free-living mite feeding on larvae or nymphs of insects, including moths, beetles, wasps and bees, that are usually found in grain, straw and firewood. When present in great number or when its food is lacking, it could accidentally bite mammals, including humans, causing a highly pruritic self-limiting dermatitis, sometimes followed by a lymphangitis known as "comet sign".We present a singular case of mite lymphangitis that surrounds and delimitates breast prosthesis in a 30-year-old Caucasian woman. Other bite in the lower abdomen did not present comet sign. The patient got the infestation in her vacation home in the South of Italy, uninhabited for 10 months since COVID-19 confinement. We hypothesize that the previous surgery made the lymphatic vessels more prone to inflammation and we compare other insect bites that can occur vacationing in a long period uninhabited room.A delayed diagnosis of comet sign implies a retarded fumigation allowing new mite bites and, in this case, extends the patient's preoccupation about the prosthesis rejection.

Neutron spectra in a tissue equivalent phantom during photon radiotherapy treatment by LINACS.

Bremsstrahlung photon beams produced by LINAC accelerators are currently the most used radiotherapy method for tumour treatments. When the photon energy exceeds the (gamma,n) reaction threshold energy, the patient receives an undesired dose due to photoneutron production both in the accelerator head and in the human body. In this paper, a method is presented for the assessment of the photoneutron spectra produced by Giant Dipole Resonance (GDR) during cancer radiotherapy with energetic photon beams. Experimental and numerical results have been obtained for the facility at Onkologik Klinik, Lund (Sweden), which is based on an ELEKTA 18 MV LINAC. Neutron spectra are evaluated both at the patient plane and inside an anthropomorphic phantom.

Monte Carlo simulation of the photoneutron field in linac radiotherapy treatments with different collimation systems.

Bremsstrahlung photon beams produced by linac accelerators are currently the most commonly used method of radiotherapy for tumour treatments. When the photon energy exceeds 10 MeV the patient receives an undesired dose due to photoneutron production in the accelerator head. In the last few decades, new sophisticated techniques such as multileaf collimators have been used for a better definition of the target volume. In this case it is crucial to evaluate the photoneutron dose produced after giant dipole resonance (GDR) excitation of the high Z materials (mainly tungsten and lead) constituting the collimator leaves in view of the optimization of the radiotherapy treatment. A Monte Carlo approach has been used to calculate the photoneutron dose arising from the GDR reaction during radiotherapy with energetic photon beams. The simulation has been performed using the code MCNP4B-GN which is based on MCNP4B, but includes a new routine GAMMAN to model photoneutron production. Results for the facility at IRCC (Istituto per la Ricerca e la Cura del Cancro) Candiolo (Turin), which is based on 18 MV x-rays from a Varian Clinac 2300 C/D, are presented for a variety of different collimator configurations.

Photoneutron yields from tungsten in the energy range of the giant dipole resonance.

Photoneutron production on the nuclei of high-Z components of medical accelerator heads can lead to a significant secondary dose during a course of bremsstrahlung radiotherapy. However, a quantitative evaluation of secondary neutron dose requires improved data on the photoreaction yields. These have been measured as a function of photon energy, neutron energy and neutron angle for natW, using tagged photons at the MAX-Lab photonuclear facility in Sweden. This work presents neutron yields for natW(gamma, n) and compares these with the predictions of the Monte Carlo code MCNP-GN, developed specifically to simulate photoneutron production at medical accelerators.

Analysis of photoneutron spectra produced in medical accelerators.

A complete method is presented for the evaluation of photoneutron spectra produced in linear accelerators for cancer radiotherapy. It consists of a computer simulation code based on the MCNP4B Monte Carlo code, in which the new routine GAMMAN was implemented, allowing the accurate study of photoneutron production in high Z elements. In addition an experimental method based on a passive bubble spectrometer allows direct measurements of the photoneutron spectrum at the patient plane, also under the photon beam. The results are presented both for a 15 MeV linac with a traditional collimator system and for an 18 MeV linac equipped with a multileaf collimator, used in conformational radiotherapy.