NOTE The report of the Committee without its annexes appears as Official Records of the General Assembly, Sixty-third Session, Supplement No. 46. The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the United Nations concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries. The country names used in this document are, in most cases, those that were in use at the time the data were collected or the text prepared. In other cases, however, the names have been updated, where this was possible and appropriate, to reflect political changes. Scientific Annexes Annex A. Medical radiation exposures Annex B. Exposures of the public and workers from various sources of radiation INTROdUCTION 1. In the course of the research and development for and the application of atomic energy and nuclear technologies, a number of radiation accidents have occurred. Some of these accidents have resulted in significant health effects and occasionally in fatal outcomes. The application of technologies that make use of radiation is increasingly widespread around the world. Millions of people have occupations related to the use of radiation, and hundreds of millions of individuals benefit from these uses. Facilities using intense radiation sources for energy production and for purposes such as radiotherapy, sterilization of products, preservation of foodstuffs and gamma radiography require special care in the design and operation of equipment to avoid radiation injury to workers or to the public. Experience has shown that such technology is generally used safely, but on occasion controls have been circumvented and serious radiation accidents have ensued. 2. Reviews of radiation exposures from accidents have been presented in previous UNSCEAR reports. The last report containing an exclusive chapter on exposures from accidents was the UNSCEAR 1993 Report [U6]. 3. This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices. Its conclusions are to be seen in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation. 4. The Committee's evaluations of public, occupational and medical diagnostic exposures are mostly concerned with chronic exposures of …

sources and effects of ionizing radiation

Medical uses of radiation have grown very rapidly over the past decade, and, as of 2007, medical uses represent the largest source of exposure to the U.S. population. Most physicians have difficulty assessing the magnitude of exposure or potential risk. Effective dose provides an approximate indicator of potential detriment from ionizing radiation and should be used as one parameter in evaluating the appropriateness of examinations involving ionizing radiation. The purpose of this review is to provide a compilation of effective doses for radiologic and nuclear medicine procedures. Standard radiographic examinations have average effective doses that vary by over a factor of 1000 (0.01-10 mSv). Computed tomographic examinations tend to be in a more narrow range but have relatively high average effective doses (approximately 2-20 mSv), and average effective doses for interventional procedures usually range from 5-70 mSv. Average effective dose for most nuclear medicine procedures varies between 0.3 and 20 mSv. These doses can be compared with the average annual effective dose from background radiation of about 3 mSv.

Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog

The volume of cardiac diagnostic procedures involving the use of ionizing radiation has increased rapidly in recent years. Whereas in 1990, fewer than 3 million nuclear cardiology studies were performed in the United States, by 2002 this figure more than tripled to 9.9 million.1 Cardiac computed tomographic (CT) volume doubled between 2002 and 2003, to 485 000 cases,2 and has continued to grow since then. The volume of procedures performed in cardiac catheterization labs increased from 2.45 million in 1993 to 3.85 million in 2002.3

The powerful diagnostic and risk-stratification data provided by these procedures play a central role in clinical cardiology and have contributed to the decrease in morbidity and mortality from coronary heart disease. Nevertheless, performance of any diagnostic test requires a careful assessment of the risks and benefits of the test and optimization of protocols to minimize risks to patients, staff members, and the public. Procedures that utilize ionizing radiation should be performed in accordance with the As Low As Reasonably Achievable (ALARA) philosophy. Thus, physicians ordering and performing cardiac imaging should be very familiar with the dosage of radiation from cardiac diagnostic tests and ways in which dose can be minimized. In this report we discuss the measurement of radiation and the dosimetry of commonly performed cardiac diagnostic imaging tests, including nuclear scintigraphy, CT for calcium scoring and coronary angiography (CTCA), and conventional coronary angiography (CCA). For each modality, we address the terminology and methodology used to quantify radiation received by patients, doses to patients with typical protocols, and dose-reduction techniques.

Biological effects of ionizing radiation can be classified as deterministic or stochastic. Deterministic effects such as skin injuries and cataract formation occur predictably when dose exceeds a certain threshold, whereas stochastic effects such as cancer incidence and germ cell mutations occur with …

https://nuclearcardiologyseminars.com/articles/Circulation-2007-Einstein-1290-305.pdf

Radiation Dose to Patients From Cardiac Diagnostic Imaging

Pattern recognition

Recent research in the field of phosphor and scintillator materials and related detectors is reviewed. After a historical introduction the fundamental issues are explained regarding the interaction of x-ray radiation with a solid state. Crucial parameters and characteristics important for the performance of these materials in applications, including the employed measurement methods, are described. Extended description of the materials currently in use or under intense study is given. Scintillation detector configurations are further briefly overviewed and selected applications are mentioned in more detail to provide an illustration.

/pdf/scintillation-detectors-for-x-rays-3rmwfxzjvh.pdf

Scintillation detectors for x-rays

The objective of the present project was the determination of the dose received by patients during cardiac procedures, such as coronary angiography, percutaneous transluminal coronary angioplasty (PTCA) and stent implantation. Thermoluminescent dosemeters (TLDs), suitably calibrated, were used for the measurement of the dose received at four anatomical locations on the patient's skin. A dose-area product (DAP) meter was also used. The contribution of cinefluorography to the total DAP was higher than that of fluoroscopy. A DAP to effective dose conversion factor equal to 0.183 mSv Gy-1 cm-2 was estimated with the help of a Rando phantom. Thus, the effective dose received by the patients could be assessed. Mean values of effective dose equal to 5.6 mSv, 6.9 mSv, 9.3 mSv, 9.0 mSv and 13.0 mSv were estimated for coronary angiography, PTCA, coronary angiography and ad hoc PTCA, PTCA followed by stent implantation and coronary angiography and ad hoc PTCA followed by stent implantation, respectively.

Patient radiation doses during cardiac catheterization procedures.

A review of patient dose and optimisation methods in adult and paediatric CT scanning.

Intervertebral disc degeneration is an age-associated condition related to chronic back pain, while its consequences are responsible for over 90% of spine surgical procedures. In clinical practice, MRI is the modality of reference for diagnosing disc degeneration. In this study, we worked toward 2-D semiautomatic segmentation of both normal and degenerated lumbar intervertebral discs from T2-weighted midsagittal MR images of the spine. This task is challenged by partial volume effects and overlapping gray-level values between neighboring tissue classes. To overcome these problems three variations of atlas-based segmentation using a probabilistic atlas of the intervertebral disc were developed and their accuracies were quantitatively evaluated against manually segmented data. The best overall performance, when considering the tradeoff between segmentation accuracy and time efficiency, was accomplished by the atlas-robust-fuzzy c-means approach, which combines prior anatomical knowledge by means of a rigidly registered probabilistic disc atlas with fuzzy clustering techniques incorporating smoothness constraints. The dice similarity indexes of this method were 91.6% for normal and 87.2% for degenerated discs. Research in progress utilizes the proposed approach as part of a computer-aided diagnosis system for quantification and characterization of disc degeneration severity. Moreover, this approach could be exploited in computer-assisted spine surgery.

Atlas-Based Segmentation of Degenerated Lumbar Intervertebral Discs From MR Images of the Spine

The current study investigates texture properties of the tissue surrounding microcalcification (MC) clusters on mammograms for breast cancer diagnosis. The case sample analyzed consists of 85 dense mammographic images, originating from the digital database for screening mammography. mammograms analyzed contain 100 subtle MC clusters (46 benign and 54 malignant). The tissue surrounding MCs is defined on original and wavelet decomposed images, based on a redundant discrete wavelet transform. Gray-level texture and wavelet coefficient texture features at three decomposition levels are extracted from surrounding tissue regions of interest (ST-ROIs). Specifically, gray-level first-order statistics, gray-level cooccurrence matrices features, and Lawspsila texture energy measures are extracted from original image ST-ROIs. Wavelet coefficient first-order statistics and wavelet coefficient cooccurrence matrices features are extracted from subimages ST-ROIs. The ability of each feature set in differentiating malignant from benign tissue is investigated using a probabilistic neural network. Classification outputs of most discriminating feature sets are combined using a majority voting rule. The proposed combined scheme achieved an area under receiver operating characteristic curve (Az) of 0.989. Results suggest that MCspsila ST texture analysis can contribute to computer-aided diagnosis of breast cancer.

Breast Cancer Diagnosis: Analyzing Texture of Tissue Surrounding Microcalcifications

A method aimed at minimizing image noise while optimizing contrast of image features is presented. The method is generic and it is based on local modification of multiscale gradient magnitude values provided by the redundant dyadic wavelet transform. Denoising is accomplished by a spatially adaptive thresholding strategy, taking into account local signal and noise standard deviation. Noise standard deviation is estimated from the background of the mammogram. Contrast enhancement is accomplished by applying a local linear mapping operator on denoised wavelet magnitude values. The operator normalizes local gradient magnitude maxima to the global maximum of the first scale magnitude subimage. Coefficient mapping is controlled by a local gain limit parameter. The processed image is derived by reconstruction from the modified wavelet coefficients. The method is demonstrated with a simulated image with added Gaussian noise, while an initial quantitative performance evaluation using 22 images from the DDSM database was performed. Enhancement was applied globally to each mammogram, using the same local gain limit value. Quantitative contrast and noise metrics were used to evaluate the quality of processed image regions containing verified lesions. Results suggest that the method offers significantly improved performance over conventional and previously reported global wavelet contrast enhancement methods. The average contrast improvement, noise amplification and contrast-to-noise ratio improvement indices were measured as 9.04, 4.86 and 3.04, respectively. In addition, in a pilot preference study, the proposed method demonstrated the highest ranking, among the methods compared. The method was implemented in C++ and integrated into a medical image visualization tool.

https://iopscience.iop.org/article/10.1088/0031-9155/48/6/307/pdf

G.S. Panayiotakis

Papers

Patient radiation doses during cardiac catheterization procedures.

A review of patient dose and optimisation methods in adult and paediatric CT scanning.

Atlas-Based Segmentation of Degenerated Lumbar Intervertebral Discs From MR Images of the Spine

Breast Cancer Diagnosis: Analyzing Texture of Tissue Surrounding Microcalcifications

A wavelet-based spatially adaptive method for mammographic contrast enhancement