Breast density quantification in dual-energy mammography using virtual anthropomorphic phantoms.

Purpose: Breast density is a significant risk factor for breast cancer and can impact the sensitivity of screening mammography. Area-based breast density measurements may not provide an accurate representation of the tissue distribution, therefore volumetric breast density (VBD) measurements are preferred. Dual-energy mammography enables volumetric measurements without additional assumptions about breast shape.

Accuracy and Precision of Iodine Quantification in Subtracted Micro-Computed Tomography: Effect of Reconstruction and Noise Removal Algorithms.

Purpose: To evaluate the effect of reconstruction and noise removal algorithms on the accuracy and precision of iodine concentration (C) quantified with subtracted micro-computed tomography (micro-CT).

Procedures: Two reconstruction algorithms were evaluated: a filtered backprojection (FBP) algorithm and a simultaneous iterative reconstruction technique (SIRT) algorithm. A 3D bilateral filter (BF) was used for noise removal.

Out-of-field mean photon energy and dose from 6 MV and 6 MV FFF beams measured with TLD-300 and TLD-100 dosimeters.

Purpose: To measure the out-of-field mean photon energy and dose imparted by the secondary radiation field generated by 6 MV and 6 MV FFF beams using TLD-300 and TLD-100 dosimeters and to use the technique to quantify the contributions from the different sources that generate out-of-field radiation.

Methods: The mean photon energy and the dose were measured using the TLD-300 glow curve properties and the TLD-100 response, respectively. The TLD-300 glow curve shape was energy-calibrated with gamma rays from Tc, F, Cs, and Co sources, and its energy dependence was quantified by a parameter obtained from the curve deconvolution.

Quantitative Imaging Parameters of Contrast-Enhanced Micro-Computed Tomography Correlate with Angiogenesis and Necrosis in a Subcutaneous C6 Glioma Model.

The aim of this work was to systematically obtain quantitative imaging parameters with static and dynamic contrast-enhanced (CE) X-ray imaging techniques and to evaluate their correlation with histological biomarkers of angiogenesis in a subcutaneous C6 glioma model. Enhancement (E), iodine concentration (C), and relative blood volume (rBV) were quantified from single- and dual-energy (SE and DE, respectively) micro-computed tomography (micro-CT) images, while rBV and volume transfer constant (K) were quantified from dynamic contrast-enhanced (DCE) planar images. C and rBV allowed a better discernment of tumor regions from muscle than E in SE and DE images, while no significant differences were found for rBV and K in DCE images.

Medical physics graduate education in Mexico and its relation to the advances in radiation oncology.

Aim: To evaluate the state of graduate education in medical physics and progress in radiation oncology (RO) equipment in Mexico since 2000, when conferring degrees from two master's-degree programs in Medical Physics began.

Background: Medical physics is a Health Profession and there are international recommendations for education, training, and certification. Both programs follow these education guidelines.

Improvement of early detection of breast cancer through collaborative multi-country efforts: Medical physics component.

Purpose: The International Atomic Energy Agency (IAEA) through a Coordinated Research Project on "Enhancing Capacity for Early Detection and Diagnosis of Breast Cancer through Imaging", brought together a group of mammography radiologists, medical physicists and radiographers; to investigate current practices and improve procedures for the early detection of breast cancer by strengthening both the clinical and medical physics components. This paper addresses the medical physics component.

Methods: The countries that participated in the CRP were Bosnia and Herzegovina, Costa Rica, Egypt, India, Kenya, the Frmr.

Clinical study of contrast-enhanced digital mammography and the evaluation of blood and lymphatic microvessel density.

Objective: To correlate image parameters in contrast-enhanced digital mammography (CEDM) with blood and lymphatic microvessel density (MVD).

Methods: 18 Breast Imaging-Reporting and Data System (BI-RADS)-4 to BI-RADS-5 patients were subjected to CEDM. Craniocaudal views were acquired, two views (low and high energy) before iodine contrast medium (CM) injection and four views (high energy) 1-5 min afterwards.

Use of an orthovoltage X-ray treatment unit as a radiation research system in a small-animal cancer model.

Background: We explore the use of a clinical orthovoltage X-ray treatment unit as a small-animal radiation therapy system in a tumoral model of cervical cancer.

Methods: Nude mice were subcutaneously inoculated with 5 x 106 HeLa cells in both lower limbs. When tumor volume approximated 200 mm3 treatment was initiated.

Spatial dose distributions in solid tumors from 186Re transported by liposomes using HS radiochromic media.

Purpose: A procedure for the measurement of spatial dose rate distribution of beta particles emitted by 186Re-liposomes in tumoral tissue, using HS GafChromic films, is presented.

Methods: HNSCC xenografts were intratumorally injected with 3.7 or 11.

PSF, LSF and S/P in mammography: GEANT4 validation.

The main goal of this study was to validate the predictions of GEANT4, a Monte Carlo code originally developed for high-energy physics, for low-energy (10-40 keV) photon transmission and scattering through matter similar to biological tissue. We compared GEANT4 calculations with existing phantom data relevant for the mammographic imaging technique. This work showed that scattered-to-primary ratio data can be simulated using GEANT4 with a deviation smaller than 5%.

[The quality of radiology services in five Latin American countries].

Objective: To determine the correlation between certain quality indicators for imaging services and the accurate interpretation of radiological exams for four frequent complaints: breast lumps, gastrointestinal discomfort, back pain, and symptoms of tuberculosis.

Methods: Twenty-six radiology services in Argentina, Bolivia, Colombia, Cuba, and Mexico were assessed. The mammography and conventional radiographic/fluoroscopic equipment used in selected services were evaluated utilizing common protocols, data sheets, testing instruments, phantoms, and calibrated dosimetry systems.

Phenomenological study of the ionisation density-dependence of TLD-100 peak 5a.

Horowitz and collaborators have reported evidence on the structure of TLD-100 peak 5. A satellite peak, called 5a, has been singled out as arising from localised electron-hole recombination in a trap/luminescent centre, its emission mechanism would be geminate recombination and, therefore, its population would depend on incident radiation ionisation density. We report a phenomenological study of peak 4, 5a and 5 strengths for glow curves previously measured at UNAM for gammas, electrons and low-energy ions.

Absorbed dose and transmission factor in blocked fields for radiotherapy treatments with 6 MV X-ray.

Absorbed dose and transmission factors were determined for 6 MV X-ray fields applied in four conventional external radiation treatments where protection blocks are used to shield organs at risk. Studied treatments are: head and neck (cancer of the larynx), breast (breast cancer), brain (brain tumours) and pelvis (cervix-uterine cancer). Experimental determinations were made using ionization chambers and thermoluminescent dosimeters, at different locations in phantoms, for blocked and unblocked fields.

Ionisation density dependence of the optically stimulated luminescence dose-response of AL2O3:C to low-energy charged particles.

The optically stimulated luminescence (OSL) response of Al2O3:C to high doses of gamma or beta irradiation can be used to predict the response of this material to charged particles as a function of particle fluence, particle energy and/or linear energy transfer (LET). In particular, it is predicted that track interaction effects at high particle fluences should result in linear-sublinear growth of the OSL signal. Similar considerations also predict a dependence of the fluence at which sublinearity starts upon the energy of the particles.

Evaluation of equipment performance, patient dose, imaging quality, and diagnostic coincidence in five Mexico City mammography services.

Background: Regulations concerning the use of x-rays in medical diagnoses were published in Mexico in 1997. In this work, we evaluate technical aspects of mammography services in the Mexico City area and radiation dose and coincidence between the radiological interpretation by the institution radiologist and by a panel of experts.

Methods: Following methodology proposed by the American College of Radiology and the European Community among others, we have evaluated the performance of six mammography systems in Mexico City public and private services.