The number of computed tomographic (CT) studies performed is increasing rapidly. Because CT scans involve much higher doses of radiation than plain films, we are seeing a marked increase in radiation exposure in the general population. Epidemiologic studies indicate that the radiation dose from even two or three CT scans results in a detectable increase in the risk of cancer, especially in children. This article summarizes the facts about this form of radiation exposure and the implications for public health.

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Computed Tomography — An Increasing Source of Radiation Exposure

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

2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM guidelines for the diagnosis and management of patients with thoracic aortic disease: Executive summary: A report of the american college of cardiology foundation/american heart association task force on practice guidelines, american association for thoracic surgery, american college of radiology, american stroke association

https://www.suscch.eu/e107_files/public/Aorta/Guidelines_for_the_Diagnosis_and_Management_of_Patients_with_Thoracic_Aortic_Disease,_2010.pdf

2010 ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease

The aim of this study was to assess the feasibility of a differentiation of iodine from other materials and of different body tissues using dual energy CT. Ten patients were scanned on a SOMATOM Definition Dual Source CT (DSCT; Siemens, Forchheim, Germany) system in dual energy mode at tube voltages of 140 and 80 kVp and a ratio of 1:3 between tube currents. Weighted CT Dose Index ranged between 7 and 8 mGy, remaining markedly below reference dose values for the respective body regions. Image post-processing with three-material decomposition was applied to differentiate iodine or collagen from other tissue. The results showed that a differentiation and depiction of contrast material distribution is possible in the brain, the lung, the liver and the kidneys with or without the underlying tissue of the organ. In angiographies, bone structures can be removed from the dataset to ease the evaluation of the vessels. The differentiation of collagen makes it possible to depict tendons and ligaments. Dual energy CT offers a more specific tissue characterization in CT and can improve the assessment of vascular disease. Further studies are required to draw conclusions on the diagnostic value of the individual applications.

Material differentiation by dual energy CT: initial experience

In the past decade, the tremendous advances in computed tomography (CT) technology and applications have increased the clinical utilization of CT, creating concerns about individual and population doses of ionizing radiation. Scanner manufacturers have subsequently implemented several options to appropriately manage or reduce the radiation dose from CT. Modulation of the x-ray tube current during scanning is one effective method of managing the dose. However, the distinctions between the various tube current modulation products are not clear from the product names or descriptions. Depending on the scanner model, the tube current may be modulated according to patient attenuation or a sinusoidal-type function. The modulation may be fully preprogrammed, implemented in near-real time by using a feedback mechanism, or achieved with both preprogramming and a feedback loop. The dose modulation may occur angularly around the patient, along the long axis of the patient, or both. Finally, the system may allow use o...

https://pubs.rsna.org/doi/pdf/10.1148/rg.262055138

CT dose reduction and dose management tools: overview of available options.

Strategies for reducing radiation dose in CT.

OBJECTIVE. The objective of our study was to compare dose–length product (DLP)–based estimates of effective dose with organ dose–based calculations using tissue-weighting factors from publication 103 of the International Commission on Radiological Protection (ICRP) or dual-energy CT protocols.MATERIALS AND METHODS. Using scanner- and energy-dependent organ dose coefficients, we calculated effective doses for CT examinations of the head, chest, coronary arteries, liver, and abdomen and pelvis using routine clinical single- or dual-energy protocols and tissue-weighting factors published in 1991 in ICRP publication 60 and in 2007 in ICRP publication 103. Effective doses were also generated from the respective DLPs using published conversion coefficients that depend only on body region. For each examination type, the same volume CT dose index was used for single- and dual-energy scans.RESULTS. Effective doses calculated for CT examinations using organ dose estimates and ICRP 103 tissue-weighting factors diffe...

https://www.ajronline.org/doi/pdf/10.2214/AJR.09.3462

Estimating Effective Dose for CT Using Dose–Length Product Compared With Using Organ Doses: Consequences of Adopting International Commission on Radiological Protection Publication 103 or Dual-Energy Scanning

Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk This article summarizes the general technical strategies that are commonly used for radiation dose management in CT Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented

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Radiation dose reduction in computed tomography: techniques and future perspective

Purpose: To investigate a novel locally adaptive projection space denoising algorithm for low-dose CT data. Methods: The denoising algorithm is based on bilateral filtering, which smooths values using a weighted average in a local neighborhood, with weights determined according to both spatial proximity and intensity similarity between the center pixel and the neighboring pixels. This filtering is locally adaptive and can preserve important edge information in the sinogram, thus maintaining high spatial resolution. A CTnoise model that takes into account the bowtie filter and patient-specific automatic exposure control effects is also incorporated into the denoising process. The authors evaluated the noise-resolution properties of bilateral filtering incorporating such a CTnoise model in phantom studies and preliminary patient studies with contrast-enhanced abdominal CT exams. Results: On a thin wire phantom, the noise-resolution properties were significantly improved with the denoising algorithm compared to commercial reconstruction kernels. The noise-resolution properties on low-dose (40 mA s) data after denoising approximated those of conventional reconstructions at twice the dose level. A separate contrast plate phantom showed improved depiction of low-contrast plates with the denoising algorithm over conventional reconstructions when noise levels were matched. Similar improvement in noise-resolution properties was found on CT colonography data and on five abdominal low-energy (80 kV) CT exams. In each abdominal case, a board-certified subspecialized radiologist rated the denoised 80 kV images markedly superior in image quality compared to the commercially available reconstructions, and denoising improved the image quality to the point where the 80 kV images alone were considered to be of diagnostic quality. Conclusions: The results demonstrate that bilateral filtering incorporating a CTnoise model can achieve a significantly better noise-resolution trade-off than a series of commercial reconstruction kernels. This improvement in noise-resolution properties can be used for improving image quality in CT and can be translated into substantial dose reduction.

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James M. Kofler

Papers

CT dose reduction and dose management tools: overview of available options.

Strategies for reducing radiation dose in CT.

Estimating Effective Dose for CT Using Dose–Length Product Compared With Using Organ Doses: Consequences of Adopting International Commission on Radiological Protection Publication 103 or Dual-Energy Scanning

Radiation dose reduction in computed tomography: techniques and future perspective

Projection space denoising with bilateral filtering and CT noise modeling for dose reduction in CT