David Borrego

The HARMONIC study (health effects of cardiac fluoroscopy and modern radiotherapy in paediatrics) aims, among other objectives, to investigate the relationship between ionising radiation and cancer incidence in children treated by cardiac fluoroscopy procedures (HARMONIC-Cardio). This requires estimation of organ doses for a large patient cohort. A framework for accurate dose calculation was developed, and used to create a software tool for rapid dose estimates. Organ doses were calculated with MCNP6.2 Monte Carlo particle transport code. Eight realistic, anthropomorphic phantoms were used representing newborn, 1, 5, 10, 15 year old and adult patients. Only male phantoms were used for patients younger than 15; male and female for older patients). A large range of technical parameters was covered in the simulations, including 11 primary beam angles and seven secondary angles, four levels of beam filtration, three tube voltages and three field sizes. The absorbed dose was computed for 32 organs and tissues. The calculated organ doses were normalised to the air kerma-area product (PKA), a common modality-specific dose index, resulting in PKA-to-organ-dose conversion coefficients. These coefficients were extended by interpolation. Organ dose conversion coefficients were calculated for 22,176 exposure configurations and interpolated to a total of 2,667,600. The coefficients for 15 organs of interest for radiation protection and effective dose were embedded in HARMONIC-CardioDose: a software tool that enables users to estimate organ doses for virtually any exposure scenario within the simulation range. The program is in the form of a Python script or an executable file, and uses a simple Excel document for inputting technical parameters necessary for calculations. HARMONIC-CardioDose is a validated software tool for rapid estimate of organ doses for paediatric and adult patients undergoing interventional cardiology procedures. The tool is freely available to the medical and research community for supporting patient dosimetry

Objective: Barium and iodinated contrast media are ubiquitous with upper gastrointestinal (UGI) series examinations performed on paediatric patients. The present study quantifies the impact of contrast media on organ absorbed and detriment-weighted doses for UGI examinations. Approach: A paediatric radiologist and a medical physicist created reference imaging fields for four complete UGI series examinations encompassing the newborn and 1-year-old female for both normal and abnormal disease states. Monte Carlo radiation transport simulations were performed for these four cases, with and without contrast media, using the International Commission on Radiological Protection’s (ICRP) voxel-based reference computational phantoms (VRCPs). Main Results: Estimates of detriment-weighted dose and absorbed doses to the colon, heart wall, kidneys, lungs, small intestine wall, spleen, stomach wall, thymus, thyroid, and remainder tissues are reported. For fields with contrast media the organ absorbed doses and detriment-weighted dose decreased by up to 50% and 26%, respectively, with the dose for the complete examination, i.e., not per field, decreasing by up to 26% for organs impacted by the presence of contrast media. Significance: Overall, relative doses were shown to decrease for simulations that included contrast media due to selective absorption of the x-ray beam by the contrast media. This study, however, did not investigate the effects of the automatic brightness control which could result in organ absorbed doses increasing due to compensation by the fluoroscopy machine when contrast media is present in the field.

Objective. International Commission on Radiological Protection (ICRP) Task Group 113 is developing reference values of organ and effective dose coefficients (DCs) for radiography, fluoroscopy, and computed tomography imaging exams. In support of these efforts, our focus is on pediatric diagnostic fluoroscopy. Contrast agents used during clinical examinations are an important consideration of the work undertaken by the Task Group. This work demonstrates the importance of including organ contrast volume concentrations for the calculation of reference organ DCs in the voiding cystourethrogram (VCUG). Approach. The ICRP newborn and 15 year female reference phantoms were utilized within the Particle and Heavy Ion Transport code system for the calculation of organ DCs. A pediatric radiologist with over 30 years of clinical experience defined the imaging fields for a VCUG examination consistent with clinical practice. Of these, four imaging fields were selected for investigation. The transport simulations modeled an iodinated contrast solution similar to Bracco Group’s 18% weight per volume, cystografin diatrizoate meglumine and typical bladder content was supplemented to make up the remainder volume. Iodinated contrast volumes of 0%, 25%, 50%, 75%, and 100% concentration by volume were modeled and associated DCs for in-field organs were computed. Main results. Organ DCs were calculated for the urinary bladder wall, colon wall, ovaries, and uterus for both female phantoms under irradiation geometries representative of a VCUG examination. Some organ DCs increased with iodine volume in the bladder and other organ DCs decreased as the iodine contrast volume completely filled the bladder (100%). Significance. The study results demonstrate for the newborn phantom percent differences in organ DCs varied between 0%–10% for the organs of interest, while they varied between 0%–22% in the 15 year phantom suggesting the importance of including contrast media in Monte Carlo radiation transport simulations of the VCUG examination.

The process to arrive at the radiation protection practices of today to protect workers, patients, and the public, including sensitive populations, has been a long and deliberative one. This paper presents an overview of the US Environmental Protection Agency’s (US EPA) responsibility in protecting human health and the environment from unnecessary exposure to radiation. The origins of this responsibility can be traced back to early efforts, a century ago, to protect workers from x rays and radium. The system of radiation protection we employ today is robust and informed by the latest scientific consensus. It has helped reduce or eliminate unnecessary exposures to workers, patients, and the public while enabling the safe and beneficial uses of radiation and radioactive material in diverse areas such as energy, medicine, research, and space exploration. Periodic reviews and analyses of research on health effects of radiation by scientific bodies such as the National Academy of Sciences, National Council on Radiation Protection and Measurements, United Nations Scientific Committee on the Effects of Atomic Radiation, and the International Commission on Radiological Protection continue to inform radiation protection practices while new scientific information is gathered. As a public health agency, US EPA is keenly interested in research findings that can better elucidate the effects of exposure to low doses and low dose rates of radiation as applicable to protection of diverse populations from various sources of exposure. Professional organizations such as the Health Physics Society can provide radiation protection practitioners with continuing education programs on the state of the science and describe the key underpinnings of the system of radiological protection. Such efforts will help equip and prepare radiation protection professionals to more effectively communicate radiation health information with their stakeholders.

From 1980 to 2015, higher and more variable annual occupational doses were observed among U.S. radiologic technologists performing nuclear medicine procedures, especially cardiac and PET examinatio... Background Occupational doses to most medical radiation workers have declined substantially since the 1950s because of improvements in radiation protection practices. However, different patterns ma...

There is limited evidence that non-leukaemic lymphoid malignancies are radiogenic. As radiation-related cancer risks are generally higher after childhood exposure, we analysed pooled lymphoid neoplasm data in nine cohorts first exposed to external radiation aged 0.4). In six cohorts with estimates of lymphatic tissue dose, borderline significant increased risks (p-trend = 0.02–0.07) were observed for NHL + CLL, NHL, and CLL. Further pooled epidemiological studies are needed with longer follow-up, central outcome review by expert hematopathologists, and assessment of radiation doses to lymphoid tissues.

The HARMONIC project (Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Paediatrics) is a European study aiming to improve our understanding of the long-term health risks from radiation exposures in childhood and early adulthood. Here, we present the study design for the cardiac component of HARMONIC. A pooled cohort of approximately 100,000 patients who underwent cardiac fluoroscopy procedures in Belgium, France, Germany, Italy, Norway, Spain or the UK, while aged under 22 years, will be established from hospital records and/or insurance claims data. Doses to individual organs will be estimated from dose indicators recorded at the time of examination, using a lookup-table-based dosimetry system produced using Monte Carlo radiation transport simulations and anatomically realistic computational phantom models. Information on beam geometry and x-ray energy spectra will be obtained from a representative sample of radiation dose structured reports (RDSRs). Uncertainties in dose estimates will be modelled using 2-dimensional Monte Carlo methods. The cohort will be followed up using national registries and insurance records (Germany) to determine vital status and cancer incidence. Information on organ transplantation (a major risk factor for cancer development) and/or other conditions predisposing to cancer will be obtained from national or local registries and health insurance data, depending on country. The relationship between estimated radiation dose and cancer risk will be investigated using regression modelling. Results will improve information for patients and parents and aid clinicians in managing and implementing changes to reduce radiation risks without compromising medical benefits.