Interaction of L-phenylalanine with carbonyl groups in mixed lipid membranes.

The interaction of L-Phe with the membrane components, i.e., lipids and proteins, has been discussed in the current literature due to the interest to understand the effect of single amino acids in relation to the formation of amyloid aggregates.

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.

Quantification of tumor angiogenesis with contrast-enhanced x-ray imaging in preclinical studies: a review.

Tissue contrast is a major challenge in the application of computed tomography (CT) and micro-computed tomography (micro-CT) techniques for imaging cancer. Contrast medium is used in order to enhance contrast of certain organs of interest, as well as tumors. Several types of contrast media have been used to assess tumor vasculature, perfusion and angiogenesis in preclinical studies.

Dosimetry in a mammography phantom using TLD-300 dosimeters.

Purpose: The purpose of this study was to evaluate the photon field effective energy (E ) distribution and percentage depth-dose (PDD) within a mammography phantom by the analysis of the CaF :Tm (TLD-300) thermoluminescent (TL) glow curve. The experimental procedure involves the use of TLD-300 to determine with single dosimeter exposures both the relative dose and the beam quality.

Methods: TLD-300 chips were exposed to x rays from a GE Senographe 2000D mammography unit at the surface and different depths within a BR12 phantom.

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.

Evolution of the CaF₂:Tm (TLD-300) glow curve as an indicator of beam quality for low-energy photon beams.

We study the high- to low- temperature signal ratio (HLTR) of the CaF2:Tm glow curve as a function of beam quality for low-energy photon beams with effective energy between 15.2 and 33.6 keV, generated with W, Mo and Rh anodes.

Measurement of radiation exposure in relatives of thyroid cancer patients treated with (131)I.

This work evaluates the radiological risk that patients treated with I for differentiated thyroid cancer could present to relatives and occupationally exposed workers. Recently, the International Atomic Energy Agency issued document K9010241, which recommends that patient discharge from the hospital must be based on the particular status of each patient. This work measures effective dose received by caregivers of patients treated with I at the Instituto Nacional de Cancerología, Mexico City.

Phantom study to evaluate contrast-medium-enhanced digital subtraction mammography with a full-field indirect-detection system.

This phantom study simulates contrast-medium-enhanced digital subtraction mammography (CEDM) and compares subtracted image quality and total mean glandular dose for two alternative spectral combinations available in a GE Senographe DS mammography unit. The first choice takes advantage of large iodine attenuation at low photon energies and uses traditionally available spectra (anode/filter combinations Mo/Mo at 25 kV and Rh/Rh at 40 kV, "Mo25-Rh40"). The second choice, selected from a previous analytical optimization, includes harder spectra obtained by adding external filtration to traditional beams (Rh/Rh at 34 kV and Rh/Rh+5 mm of Al at 45 kV, "Rh34-Rh45H").

Analytical optimization of digital subtraction mammography with contrast medium using a commercial unit.

Contrast-medium-enhanced digital mammography (CEDM) is an image subtraction technique which might help unmasking lesions embedded in very dense breasts. Previous works have stated the feasibility of CEDM and the imperative need of radiological optimization. This work presents an extension of a former analytical formalism to predict contrast-to-noise ratio (CNR) in subtracted mammograms.

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.

Textural assessment in digital mammograms.

This work focuses on testing textural and morphological parameters to assess characteristic features of digital mammograms. The selected images were radiological studies from the Institute Nacional de Cancerologia in Mexico City, evaluated as BI-RADS 4 or 5, meaning "probably malign" or "malign" findings, respectively. All patients were subjected to a biopsy procedure after the image was taken.

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.

Response of LiF:Mg,Ti to low energy carbon and oxygen ions.

The extended track interaction model (ETIM) has been formulated to explain the TL-fluence response for peak 5 to heavy ions using radial dose distributions produced by the ions in LiF and their luminescent centre occupation probability distributions. In this work, an experimental study of the TLD-100 fluence response to carbon and oxygen ions and its interpretation in terms of a Monte Carlo simulation of ETIM applied to peak 5 are presented. Irradiations were performed with 7.

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.