Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults.

Over one million European children undergo computed tomography (CT) scans annually. Although moderate- to high-dose ionizing radiation exposure is an established risk factor for hematological malignancies, risks at CT examination dose levels remain uncertain. Here we followed up a multinational cohort (EPI-CT) of 948,174 individuals who underwent CT examinations before age 22 years in nine European countries. Radiation doses to the active bone marrow were estimated on the basis of body part scanned, patient characteristics, time period and inferred CT technical parameters. We found an association between cumulative dose and risk of all hematological malignancies, with an excess relative risk of 1.96 (95% confidence interval 1.10 to 3.12) per 100 mGy (790 cases). Similar estimates were obtained for lymphoid and myeloid malignancies. Results suggest that for every 10,000 children examined today (mean dose 8 mGy), 1-2 persons are expected to develop a hematological malignancy attributable to radiation exposure in the subsequent 12 years. Our results strengthen the body of evidence of increased cancer risk at low radiation doses and highlight the need for continued justification of pediatric CT examinations and optimization of doses.

Use of ionizing radiation in a Norwegian cohort of children with congenital heart disease: imaging frequency and radiation dose for the Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Pediatrics (HARMONIC) study.

BACKGROUND: The European-funded Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Pediatrics (HARMONIC) project is a multicenter cohort study assessing the long-term effects of ionizing radiation in patients with congenital heart disease. Knowledge is lacking regarding the use of ionizing radiation from sources other than cardiac catheterization in this cohort. OBJECTIVE: This study aims to assess imaging frequency and radiation dose (excluding cardiac catheterization) to patients from a single center participating in the Norwegian HARMONIC project. MATERIALS AND METHODS: Between 2000 and 2020, we recruited 3,609 patients treated for congenital heart disease (age < 18 years), with 33,768 examinations categorized by modality and body region. Data were retrieved from the radiology information system. Effective doses were estimated using International Commission on Radiological Protection Publication 60 conversion factors, and the analysis was stratified into six age categories: newborn; 1 year, 5 years, 10 years, 15 years, and late adolescence. RESULTS: The examination distribution was as follows: 91.0% conventional radiography, 4.0% computed tomography (CT), 3.6% diagnostic fluoroscopy, 1.2% nuclear medicine, and 0.3% noncardiac intervention. In the newborn to 15 years age categories, 4-12% had ≥ ten conventional radiography studies, 1-8% underwent CT, and 0.3-2.5% received nuclear medicine examinations. The median effective dose ranged from 0.008-0.02 mSv and from 0.76-3.47 mSv for thoracic conventional radiography and thoracic CT, respectively. The total effective dose burden from thoracic conventional radiography ranged between 28-65% of the dose burden from thoracic CT in various age categories (40% for all ages combined). The median effective dose for nuclear medicine lung perfusion was 0.6-0.86 mSv and for gastrointestinal fluoroscopy 0.17-0.27 mSv. Because of their low frequency, these procedures contributed less to the total effective dose than thoracic radiography. CONCLUSION: This study shows that CT made the largest contribution to the radiation dose from imaging (excluding cardiac intervention). However, although the dose per conventional radiograph was low, the large number of examinations resulted in a substantial total effective dose. Therefore, it is important to consider the frequency of conventional radiography while calculating cumulative dose for individuals. The findings of this study will help the HARMONIC project to improve risk assessment by minimizing the uncertainty associated with cumulative dose calculations.

The value of referral information and assessment - a cross sectional study of radiographers' perceptions.

BACKGROUND: Radiology professionals are frequently confronted with referrals containing insufficient clinical information, which hinders delivery of safe and quality medical imaging services. There is however lack of knowledge on why and how referral information is important for radiographers in clinical practice. This study explores what purposes referral information is used/ useful for the radiographers, and the benefits of involving them in assessing referrals. METHODS: A cross sectional study was conducted of radiographers recruited through the International Society of Radiographers and Radiological Technologists (ISRRT) networks. A questionnaire was developed and distributed consisting of 5-point Likert scale questions on a) use/usefulness of referral information for 12 listed purposes and b) the benefits of radiographers assessing referrals for 8 possible reasons. The questionnaire was validated using a test-retest reliability analysis. Kappa values ≥0.6 were accepted. SPSS software was used for data analysis and chi-square tests to determine associations between using referral information and background variables. RESULTS: Total respondents were 279 (n = 233 currently in clinical practice and n = 46 in other positions). The participants in clinical practice ranked high all 12 listed purposes for use of referral information, and all except one received ≥60% 'frequent'/'very frequent' responses. Use for patient identification purposes received the highest score (97% 'frequently'/'very frequently' responses), followed by ensuring imaging of the correct body region (79% 'very frequently' responses). Radiographers not currently working in clinical practice ranked the 'usefulness' of listed items similarly. Significant associations between frequent use of referral information and education level were not observed, and only three items were significantly associated with modality of practice. All items on benefits of radiographers assessing referrals received ≥75% 'agree'/'strongly agree' scores. The items ranked highest were promotes radiographers' professional responsibility and improves collaboration with radiologists and referring clinicians, with 72 and 67% strongly agreed responses, respectively. CONCLUSION: Radiographers use referral information frequently for several purposes. The referral information is needed for justifying and optimising radiological procedures, hence crucial for ensuring patient safety and high-quality services. This further emphasis why radiographers perceive several benefits of being involved in assessing the referral information.

Radiographers' actions and challenges when confronted with inappropriate radiology referrals.

OBJECTIVES: To explore radiographers' actions toward inappropriate referrals and hindrances to assessing referrals. METHODS: An online survey was distributed to radiographers via the International Society of Radiographers and Radiological Technologists (ISRRT) networks. The questionnaire consisted of 5-point Likert scale questions on radiographers' actions to supplement referral information, actions for unjustified referrals and hindrances to referral assessment. The questionnaire was validated using a test-retest reliability analysis. Kappa values ≥ 0.6 were accepted. SPSS software was used for data analysis and chi-square tests to compare subgroups. RESULTS: Total responses received were 279. The most reported actions to supplement missing referral information were to ask the patient or relative, examine the body region of concern and check medical records (73%, 70%, 67%, responded often/always, respectively). The actions when confronted with unjustified referrals were reported equally to consult the radiologist, referring clinician and radiographer (69-68% often/always responses). The hindering factors ranked high (agreed/strongly agreed responses) pertained to inadequate information in referral forms (83%), ineffective communication among healthcare professionals (79%), lack of training (70%) and allocated time (61%). Statistically significant associations were observed for a few actions and hindrances with education level, modality of practice and responsibility to screen imaging referrals. CONCLUSION: Radiographers consult colleagues about suspected unjustified referrals. Effective communication pathways, training and time allocation to improve radiographers' skills to assess referrals may enhance appropriate imaging and delivery of quality patient care. KEY POINTS: • Radiographers' actions of supplementing missing information in radiology referrals facilitate provision of high-quality health services. • Radiographers' strategy when confronted with inappropriate referrals is to consult radiologists and referring clinicians. • Better inter-professional communication and organisation of tasks can facilitate radiographers' participation in referral assessment to ensure appropriate imaging.

Dose Estimation for the European Epidemiological Study on Pediatric Computed Tomography (EPI-CT).

Within the European Epidemiological Study to Quantify Risks for Paediatric Computerized Tomography (EPI-CT study), a cohort was assembled comprising nearly one million children, adolescents and young adults who received over 1.4 million computed tomography (CT) examinations before 22 years of age in nine European countries from the late 1970s to 2014. Here we describe the methods used for, and the results of, organ dose estimations from CT scanning for the EPI-CT cohort members. Data on CT machine settings were obtained from national surveys, questionnaire data, and the Digital Imaging and Communications in Medicine (DICOM) headers of 437,249 individual CT scans. Exposure characteristics were reconstructed for patients within specific age groups who received scans of the same body region, based on categories of machines with common technology used over the time period in each of the 276 participating hospitals. A carefully designed method for assessing uncertainty combined with the National Cancer Institute Dosimetry System for CT (NCICT, a CT organ dose calculator), was employed to estimate absorbed dose to individual organs for each CT scan received. The two-dimensional Monte Carlo sampling method, which maintains a separation of shared and unshared error, allowed us to characterize uncertainty both on individual doses as well as for the entire cohort dose distribution. Provided here are summaries of estimated doses from CT imaging per scan and per examination, as well as the overall distribution of estimated doses in the cohort. Doses are provided for five selected tissues (active bone marrow, brain, eye lens, thyroid and female breasts), by body region (i.e., head, chest, abdomen/pelvis), patient age, and time period (1977-1990, 1991-2000, 2001-2014). Relatively high doses were received by the brain from head CTs in the early 1990s, with individual mean doses (mean of 200 simulated values) of up to 66 mGy per scan. Optimization strategies implemented since the late 1990s have resulted in an overall decrease in doses over time, especially at young ages. In chest CTs, active bone marrow doses dropped from over 15 mGy prior to 1991 to approximately 5 mGy per scan after 2001. Our findings illustrate patterns of age-specific doses and their temporal changes, and provide suitable dose estimates for radiation-induced risk estimation in epidemiological studies.

The HARMONIC project: study design for the assessment of radiation doses and associated cancer risks following cardiac fluoroscopy in childhood.

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 fluoroscopy 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. Uncertainties in dose estimates will be modelled using 2D Monte Carlo methods. The cohort will be followed up using national registries and insurance records to determine vital status and cancer incidence. Information on organ transplantation (a major risk factor for cancer development in this patient group) 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.

Impact of mobile radiography services in nursing homes on the utilisation of diagnostic imaging procedures.

BACKGROUND: In the last decade, mobile radiography services have been introduced in nursing homes in several countries. Earlier research found an underutilisation of diagnostic imaging among nursing home residents. However, the effects of introducing mobile radiography services on the use of diagnostic imaging are unknown. The purpose of this study was to determine the utilisation of diagnostic imaging among nursing home residents and if there are any differences between hospitals with and without a mobile radiography service. METHODS: Data for 2015 were collected from the radiological information systems of 11 hospitals. The data included information on the anatomical region/organ/organ system, modality, and information on where the examination took place. Using nursing home beds as a proxy for nursing home residents' differences in the use of diagnostic imaging in areas with hospitals with and without mobile radiography services were analysed. The chi-squared test was used to compare the areas. RESULTS: From 11,066 examinations of nursing home residents, 87% were plain radiographs, 8% were CT scans, and 4% were ultrasound examinations. In areas with mobile radiography services, there was a significantly higher proportion of diagnostic imaging used per nursing home bed, 50% per bed compared to 36% per bed in areas without; p = < 0.001. Furthermore, in areas with mobile radiography services, there was a significantly lower proportion of CT and ultrasound used per nursing home bed, 2.5 and 1.4% respectively per bed compared to 4.7 and 2.2% respectively per bed in areas without; p = < 0.001. CONCLUSIONS: This study demonstrate a lower use of radiology by nursing home residents compared to the general population, and indicates that mobile radiography services increase the level closer to the user rate in the general population. The proportions of plain radiographs are significantly higher in areas with a mobile radiography service, while the proportion of more advanced imaging techniques such as CT and ultrasound are lower. The higher use of diagnostic imaging is most likely appropriate because of higher morbidity and lower use of diagnostic imaging among nursing home residents, compared to the general population. Further research is necessary on how to improve diagnostic imaging services for nursing home residents.

Cost analysis of mobile radiography services for nursing home residents in Southeast Norway.

RATIONALE, AIMS, AND OBJECTIVE: Telemedicine applications, such as a mobile radiography service, provide a new way of organizing healthcare services. In order to provide safe and personalised care for nursing home residents during X-ray examinations, mobile radiography services have been implemented. The objective of this study was to analyse the costs of X-ray examinations and treatments for nursing home residents when comparing hospital-based imaging with a combination of hospital-based imaging and a mobile radiography service in Southeast Norway. METHODS: A decision model was developed using the software TreeAge Pro. The model included two alternatives: the mobile radiography service in combination with hospital-based imaging and hospital-based imaging alone. The treatment needed based on the examination results could be given either in the nursing home or at the hospital. Probabilities and costs in the model were derived from previous research, various reports, and hospital data from the Southeast region of Norway. Monte Carlo simulations of 1000 residents were run through the model, and statistical analyses were applied. RESULTS: The analysis showed a mean cost of €2790 per resident for the hospital-based service alone. For mobile and hospital-based services combined, the mean cost was €1946 per resident, including examinations and the immediate treatment given. This difference in costs was significant (p < 0.001). CONCLUSION: A mobile radiography service in nursing homes provides a safe, high quality health care service. The result of this study showed there was a 30% cost-reduction by implementing the mobile radiography service.

Managers' experience of success criteria and barriers to implementing mobile radiography services in nursing homes in Norway: a qualitative study.

BACKGROUND: In order to meet the future challenges posed by ageing populations, new technology, telemedicine and a more personalized healthcare system are needed. Earlier research has shown mobile radiography services to be highly beneficial for nursing home residents in addition to being cost-effective. Despite the benefits, mobile radiography services are uncommon in Europe and Norway. The purpose of this study was to explore success criteria and barriers in the process of implementing mobile radiography services, from the point of view of the hospital and municipal managers. METHODS: Eleven semi-structured interviews were conducted with managers from five hospitals and six municipalities in Norway where mobile radiography services had been implemented. Core issues in the interview guide were barriers and facilitators in the different phases of implementation. The framework method for thematic analysis was used for analysing the data inductively in a research team. RESULTS: Five main categories were developed through the success criteria and barriers experienced by the participants: national health policy, regional and municipal policy and conditions, inter-organizational implementation projects, experienced outcome, and professional skills and personal characteristics. The categories were allocated into three higher-order classifications: macro, meso and micro levels. The main barriers experienced by the managers were financial, procedural and structural. In particular, the reimbursement system, lack of management across healthcare levels and the lack of compatible information systems acted as barriers. The main facilitators were external funding, enthusiastic individuals in the organizations and good collaboration between hospitals and municipalities. CONCLUSIONS: The managers experienced financial, structural and procedural barriers. The main success criteria in the process were external funding, and the support and engagement from the individuals in the organizations. This commitment was mainly facilitated by the intuitive appeal of mobile radiography. Changes in healthcare management and in the financial system might facilitate services across healthcare levels. In addition, compatible information systems across healthcare levels are needed in order to facilitate the use of new technology and mobile services.

Radiation exposure in patients treated with endovascular aneurysm repair: what is the risk of cancer, and can we justify treating younger patients?

Background Endovascular aneurysm repair (EVAR) is becoming the mainstay treatment of abdominal aortic aneurisms (AAA). The postoperative follow-up regime includes a lifelong series of CT angiograms (CTAs) at different intervals in addition to EVAR, which will confer significant cumulative radiation exposure over time. Purpose To examine the impact of age and follow-up regime over time on cumulative radiation exposure and attributable cancer risk after EVAR. Material and Methods We calculated a mean effective dose (ED) for the EVAR procedure, CTA, and plain abdominal X-rays (PAX). Cumulative ED was calculated for standard, complex, and simplified surveillance over 5, 10, and 15 years for different age groups. Results For EVAR, the mean ED was 34 mSv (range, 12-75 mSv) per procedure. For PAX, the ED was 1.1 mSv (range, 0.3-4.4 mSv), and for CTA it was 8.0 mSv (range, 2-20 mSv). For a 55-year-old man, an attributable cancer risk (ACR) in standard surveillance at 5 and 15 years of follow-up was 0.35% and 0.65%, respectively. The corresponding values were 0.22% and 0.37% for a 75-year-old man. When using a simplified follow-up, the ACRs for a 55-year-old at 5 and 15 years were 0.30% and 0.37%, respectively. These values were 0.18% and 0.21% for a 75-year-old man. A complex follow-up with half-yearly CTA over similar age and time span doubled the ACR. Conclusion Treating younger patients with EVAR poses a low ACR of 0.65% (15-year standard surveillance) compared to a lifetime cancer risk of 44%. A simplified surveillance should be used if treating younger patients, which will halve the ACR over 15 years.

Reconstruction of paediatric organ doses from axial CT scans performed in the 1990s - range of doses as input to uncertainty estimates.

OBJECTIVE: To assess the range of doses in paediatric CT scans conducted in the 1990s in Norway as input to an international epidemiology study: the EPI-CT study, http://epi-ct.iarc.fr/ . METHODS: National Cancer Institute dosimetry system for Computed Tomography (NCICT) program based on pre-calculated organ dose conversion coefficients was used to convert CT Dose Index to organ doses in paediatric CT in the 1990s. Protocols reported from local hospitals in a previous Norwegian CT survey were used as input, presuming these were used without optimization for paediatric patients. RESULTS: Large variations in doses between different scanner models and local scan parameter settings are demonstrated. Small children will receive a factor of 2-3 times higher doses compared with adults if the protocols are not optimized for them. For common CT examinations, the doses to the active bone marrow, breast tissue and brain may have exceeded 30 mGy, 60 mGy and 100 mGy respectively, for the youngest children in the 1990s. CONCLUSIONS: The doses children received from non-optimised CT examinations during the 1990s are of such magnitude that they may provide statistically significant effects in the EPI-CT study, but probably do not reflect current practice. KEY POINTS: • Some organ doses from paediatric CT in the 1990s may have exceeded 100 mGy. • Small children may have received doses 2-3 times higher compared with adults. • Different scanner models varied by a factor of 2-3 in dose to patients. • Different local scan parameter settings gave dose variations of a factor 2-3. • Modern CTs and age-adjusted protocols will give much lower paediatric doses.

EPI-CT: design, challenges and epidemiological methods of an international study on cancer risk after paediatric and young adult CT.

Computed tomography (CT) has great clinical utility and its usage has increased dramatically over the years. Concerns have been raised, however, about health impacts of ionising radiation exposure from CTs, particularly in children, who have a higher risk for some radiation induced diseases. Direct estimation of the health impact of these exposures is needed, but the conduct of epidemiological studies of paediatric CT populations poses a number of challenges which, if not addressed, could invalidate the results. The aim of the present paper is to review the main challenges of a study on the health impact of paediatric CTs and how the protocol of the European collaborative study EPI-CT, coordinated by the International Agency for Research on Cancer (IARC), is designed to address them. The study, based on a common protocol, is being conducted in Belgium, Denmark, France, Germany, the Netherlands, Norway, Spain, Sweden and the United Kingdom and it has recruited over one million patients suitable for long-term prospective follow-up. Cohort accrual relies on records of participating hospital radiology departments. Basic demographic information and technical data on the CT procedure needed to estimate organ doses are being abstracted and passive follow-up is being conducted by linkage to population-based cancer and mortality registries. The main issues which may affect the validity of study results include missing doses from other radiological procedures, missing CTs, confounding by CT indication and socioeconomic status and dose reconstruction. Sub-studies are underway to evaluate their potential impact. By focusing on the issues which challenge the validity of risk estimates from CT exposures, EPI-CT will be able to address limitations of previous CT studies, thus providing reliable estimates of risk of solid tumours and leukaemia from paediatric CT exposures and scientific bases for the optimisation of paediatric CT protocols and patient protection.

Quality assurance in radiotherapy on a national level; experience from Norway: the KVIST initiative.

BACKGROUND AND PURPOSE: In radiotherapy (RT), there are high requirements for quality assurance (QA) in all the steps of the process. Development of QA systems are demanding in terms of financial and human resources. A national QA programme (KVIST) has been established in Norway to facilitate implementation of QA activity on hospital level. METHOD: The KVIST organisation comprises the KVIST team, the reference group (RG) and the working groups (WGs). The KVIST team is multidisciplinary and are employed in permanent positions. The RG acts as an advisory body for the KVIST team in defining and ranking the priority of projects. Relevant national QA projects are identified in collaboration with the RG, and WGs are established to carry out the various projects. RESULT: Several national consensus documents have been prepared by the various WGs. Systems for incident handling and activity reporting have been established and clinical audits have been implemented in Norwegian RT. Guidelines for RT of various diagnoses have also been prepared in collaboration with National Cancer groups. CONCLUSION: The KVIST programme has been very well acknowledged in the Norwegian RT community. It has succeeded in creating a positive attitude towards QA and improved the communication between centres and the various professions.

The risk of radiation-induced breast cancers due to biennial mammographic screening in women aged 50-69 years is minimal.

BACKGROUND: The main aim of mammographic screening is to reduce the mortality from breast cancer. However, use of ionizing radiation is considered a potential harm due to the possible risk of inducing cancer in healthy women. PURPOSE: To estimate the potential number of radiation-induced breast cancers, radiation-induced breast cancer deaths, and lives saved due to implementation of organized mammographic screening as performed in Norway. MATERIAL AND METHODS: We used a previously published excess absolute risk model which assumes a linear no-threshold dose-response. The estimates were calculated for 100,000 women aged 50-69 years, a screening interval of 2 years, and with an assumed follow-up until the age of 85 or 105 years. Radiation doses of 0.7, 2.5, and 5.7 mGy per screening examination, a latency time of 5 or 10 years, and a dose and dose-rate effectiveness factor (DDREF) of 1 or 2 were applied. RESULTS: The total lifetime risk of radiation-induced breast cancers per 100,000 women was 10 (95% CI: 4-25) if the women were followed from the ages of 50 to 85 years, for a dose of 2.5 mGy, a latency time of 10 years, and a DDREF of 1. For the same parameter values the number of radiation-induced breast cancer death was 1 (95% CI: 0-2). The assumed number of lives saved is approximately 350. CONCLUSION: The risk of radiation-induced breast cancer and breast cancer death due to mammographic screening is minimal. Women should not be discouraged from attending screening due to fear of radiation-induced breast cancer death.

Assessing organ doses from paediatric CT scans--a novel approach for an epidemiology study (the EPI-CT study).

The increasing worldwide use of paediatric computed tomography (CT) has led to increasing concerns regarding the subsequent effects of exposure to radiation. In response to this concern, the international EPI-CT project was developed to study the risk of cancer in a large multi-country cohort. In radiation epidemiology, accurate estimates of organ-specific doses are essential. In EPI-CT, data collection is split into two time periods--before and after introduction of the Picture Archiving Communication System (PACS) introduced in the 1990s. Prior to PACS, only sparse information about scanner settings is available from radiology departments. Hence, a multi-level approach was developed to retrieve information from a questionnaire, surveys, scientific publications, and expert interviews. For the years after PACS was introduced, scanner settings will be extracted from Digital Imaging and Communications in Medicine (DICOM) headers, a protocol for storing medical imaging data. Radiation fields and X-ray interactions within the body will be simulated using phantoms of various ages and Monte-Carlo-based radiation transport calculations. Individual organ doses will be estimated for each child using an accepted calculation strategy, scanner settings, and the radiation transport calculations. Comprehensive analyses of missing and uncertain dosimetry data will be conducted to provide uncertainty distributions of doses.

Interphantom and interscanner variations for Hounsfield units--establishment of reference values for HU in a commercial QA phantom.

In computer tomography (CT) diagnostics, the measured Hounsfield units (HU) are used to characterize tissue and are in that respect compared to nominal HU values found in the radiological literature. Quality assurance (QA) phantoms are commercially available with a variety of tissue substitutes and materials to test the HU values in CT. It is however recognized from CT physics that the HU for a given material is energy dependent and may vary substantially between scanners. The aim of this study is to analyze the characteristics of a commonly used QA phantom, the Catphan 500/600 (The Phantom Laboratory, NY). Four CT phantoms were scanned on one CT scanner to examine possible interphantom variations in HU values. Secondly, one selected phantom was scanned at three kVp levels on eight different CT scanners. The interphantom variations in HU values were small, in the range 2-5 HU. The interscanner variations were however substantial, in the range 7-56 HU depending on energy and material. Varying the x-ray energy produced a shift in the measured HU of up to 79 HU on one scanner. Reference HU values for the eight sensitometric test materials in Catphan are provided for eight CT scanner models from four vendors. The reference HU values are provided for 80, 120 and 140 kVp. Our results suggest that scanner-independent threshold levels for HU should be used only with extreme caution. Tissue characterization can be used provided that a scanner-specific data set for normal and abnormal is determined.

Radiation doses to children with shunt-treated hydrocephalus.

BACKGROUND: Children with shunt-treated hydrocephalus are still followed routinely with frequent head CT scans. OBJECTIVE: To estimate the effective dose, brain and lens doses from these examinations during childhood, and to assess dose variation per examination. MATERIALS AND METHODS: All children born between 1983 and 1995 and treated for hydrocephalus between 1983 and 2002 were included. We retrospectively registered the number of examinations and the applied scan parameters. The effective dose was calculated using mean conversion factors from the CT dose index measured free in air, while doses to the lens and brain were estimated using tabulated CT dose index values measured in a head phantom. RESULTS: A total of 687 CT examinations were performed in 67 children. The mean effective dose, lens dose and brain dose to children over 6 months of age were 1.2 mSv, 52 mGy and 33 mGy, respectively, and the corresponding doses to younger children were 3.2 mSv, 60 mGy and 48 mGy. The effective dose per CT examination varied by a factor of 64. CONCLUSION: None of the children was exposed to doses known to cause deterministic effects. However, since the threshold for radiation-induced damage is not known with certainty, alternative modalities such as US and MRI should be used whenever possible.

Diagnostic radiology in Norway trends in examination frequency and collective effective dose.

The objective of the present work was to determine current levels and recent nationwide trends in radiological examination frequency, as well as to update corresponding collective effective dose estimates. Examination frequencies were obtained from radiology management systems at all hospitals and private radiology enterprises across Norway in terms of number of examination codes. During the last decade, the overall examination frequency increased by 16% to 910 per 1000 inhabitants, excluding nuclear imaging and dental radiology. The largest increase in examination frequency occurred in MRI (10-fold increase), followed by CT (more than doubling) and mammography (nearly 70% increase). The contribution to collective effective dose from radiological examinations was estimated to 4960 man Sv or 1.09 mSv per inhabitant; representing a 40% increase from 1993 to 2002. CT contribution to collective effective dose was estimated to account for 59% of the total as opposed to 30% in the previous survey.

Shift in imaging modalities of gastrointestinal tract through 25 years and its impact on patient ionizing radiation doses.

We wanted to explore the shift in modalities when diagnosing the gastrointestinal tract through the last three decades and see how this has influenced on the radiation doses given to this patient population. Activity reports from a central hospital in the years of 1979-2003 have been reviewed. The x-ray based modalities have decreased, while there has been a marked increase in colonoscopies, gastroscopies, ultrasound, and magnetic resonance cholangiopancreatography. This has caused a reduction in collective effective radiation dose of 54%.