Radiation Lifetime Research Articles

Epitaxial stresses in an InGaAs photoconductive layer for terahertz antennas

The effect of epitaxial stresses on the excess-carrier dynamics and the terahertz radiation spectrum of the InyGa1–yAs films have been investigated by optical pump-probe and terahertz time-domain spectroscopy. It has been demonstrated that a InyGa1–yAs film with a higher mechanical stress has the shorter excesscarrier lifetime and broader terahertz radiation spectrum.

Optical properties of Er3+/Yb3+ co-doped bismuth calcium borate glass system for NIR lasers and fiber amplifiers

An Er3+/Yb3+ co-doped bismuthate (Bi2O3-B2O3-CaO) glass was prepared by melt quenching method. The samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), absorption and emission spectroscopy. The Judd-Ofelt parameters (Ωλ) were determined from the intensity of the absorption band to calculate the radiation parameters, such as the radiation lifetime (τrad), radiation transition probability (Arad) and branching ratio (βJJ′) of 4I13/2 laser conversion of Er3+ ions. The effective emission bandwidth (ΔλP), stimulated emission cross section (σse) and gain bandwidth (σse × Δλp) were determined on the emission spectra, and the optimum doping concentration of Er2O3 was 0.5mol%. The present work indicates that Er3+/Yb3+ co-doped bismuth calcium borate glass can be promising materials for solid state NIR lasers and fiber amplifiers.

Mathematical modelling of radiation-induced cancer risk from breast screening by mammography

ObjectivesEstablish a method to determine and convey lifetime radiation risk from FFDM screening. MethodsRadiation risk from screening mammography was quantified using effective risk (number of radiation-induced cancer cases/million). For effective risk calculations, organ doses and examined breast MGD were used. Screening mammography was simulated by exposing a breast phantom for cranio-caudal and medio-lateral oblique for each breast using 16 FFDM machines. An ATOM phantom loaded with TLD dosimeters was positioned in contact with the breast phantom to simulate the client’s body. Effective risk data were analysed using SPSS software to establish a regression model to predict the effective risk of any screening programme. Graphs were generated to extrapolate the effective risk of all screening programmes for a range of commencement ages and time intervals between screens. ResultsThe most important parameters controlling clients’ total effective risk within breast screening are the screening commencement age and number of screens (correlation coefficients were −0.865 and 0.714, respectively). Since the tissue radio-sensitivity reduces with age, the end age of screening does not result in noteworthy effect on total effective risk. ConclusionsThe regression model can be used to predict the total effective risk for clients within breast screening but it cannot be used for exact assessment of total effective risk. Graphical representation of risk could be an easy way to represent risk in a fashion which might be helpful to clients and clinicians.

Radiation hazards and lifetime risk assessment of tap water using liquid scintillation counting and high-resolution gamma spectrometry

In this work, two complementary techniques, viz. liquid scintillation counting and high-resolution gamma spectrometry are utilized to analyze radionuclides concentrations in tap water of Irbid governorate, Jordan, and study their correlation. Gross alpha and gross beta concentrations, in the tap water samples collected from the nine districts of Irbid governorate, ranged from <82 to 484 mBq/L with a mean of 295 mBq/L and from <216 to 984 mBq/L with a mean of 611 mBq/L, respectively. Furthermore, gamma spectrometry analysis, for the tap water samples, shows that the activity concentrations of 226Ra, 232Th, and 40K ranged between <19 and 302 mBq/L, 24 to 119 mBq/L, and <101 to 342 mBq/L, respectively. There was a weak or even no correlation among the identified natural radionuclides with no trace of artificial radioactivity. In addition, the results of both techniques show that storing tap water in drilled wells leads to higher levels of radioactivity concentrations beyond the international permissible limits. Furthermore, the average lifetime risk and annual effective dose received by age-grouped inhabitants due to direct and indirect tap water consumption are evaluated, where most of the received dose is attributed to 226Ra.

Lifetime Radiation Exposure in Patients with Recurrent Nephrolithiasis.

Patients presenting with nephrolithiasis often undergo repeated imaging studies before, during, and after management. Considering the significant risk of stone recurrence in primary stone-formers, repeated imaging studies are not uncommon. Cumulative effects of ionizing radiation exposure from various imaging studies could potentially increase the risk for developing cataracts and solid malignancies in urolithiasis patients. Therefore, practitioners planning or performing imaging studies with ionizing radiation are compelled to keep radiation exposure to humans and the environment as low as possible, thus strictly adhering to the ALARA (As Low as Reasonably Achievable) principles. This chapter will review the latest literature on lifetime radiation exposure of nephrolithiasis patients and present the latest recommendations in minimizing radiation exposure to them pre-, intra-, and postoperatively. For patients presenting with acute renal colic, especially those with body mass index of <30, low-dose noncontrast computed tomography is the current gold standard of imaging. Patients with opaque stones are followed with ultrasonography (US) and plain radiography (kidney, ureter, and bladder or KUB). Intraoperatively, pulsed fluoroscopy could be used to significantly reduce radiation during ureteroscopy and percutaneous nephrolithotomy. Immediately postoperatively and in the long term, US and KUB could be used to follow up patients with nephrolithiasis. Only symptomatic patients suspected of ureteral stricture should obtain tri-phasic CT urography. Following these latest imaging guidelines from the American Urological Association will dramatically reduce lifetime radiation exposure to patients with nephrolithiasis.

Benefits of electroanatomic ablation of conventional cardiac arrhytmias: from fluoroscopy to zero X-ray mapping.

Electrophysiology procedures are traditionally performed under fluoroscopic guidance. Nowadays a growing interest in the radiation risk associated to these procedures has been cultivated, since radiation exposure has non-negligible stochastic and deterministic effects on health. A correlation between radiation exposure and lifetime malignancy effect is difficult to establish and the threshold of a completely safe exposure dose is unknown. Thus, electrophisiologists have become aware of the use of fluoroscopy and they have tried to use all the complementary imaging technologies available in order to reduce the radiological exposure. This review is aimed at evaluating the radiation exposure risk, both for the patients and the operators. We describe electroanatomical mapping systems and technologies, which allow the reduction of radiation exposure. We review the main literature based on different catheter ablation procedures with the use of the abovementioned technologies, specifically focusing on feasibility, safety, and radiation exposure. Finally, we highlight the necessity of increasing the radiological risk awareness among operators and cardiological scientific societies.

Peritoneal Dialysis Catheter Position Evaluated by Ultrasound: Can it Replace Abdomen X-Ray in Patients Presenting Catheter Misplacement?

Background Malfunction of the peritoneal dialysis catheter is frequently caused by dislocation. The diagnostic approach is classically based on abdomen X-ray together with detailed case history and physical examination. Despite being rarely applied in clinical practice to evaluate catheter misplacement, ultrasound is a noninvasive, radiation-free technique that ispotentially useful also to explore reasons for catheter malfunction. Consequently, we aimed to evaluate the diagnostic accuracy of ultrasound to identify peritoneal catheter misplacement. Methods In a multicenter observational blinded study, we compared ultrasound to abdomen X-ray for catheter localization in 93 consecutive peritoneal dialysis patients with dialysate outflow problems enrolled in two nephrology and dialysis units. The position of the catheter was annotated on a standard scheme of nine abdominopelvic regions. The sensitivity, specificity, positive and negative predictive value and Kappa coefficient were calculated. Results Dislocation out of the inferior abdominopelvic regions was present in 19 patients (20 %) at X-ray and 23 patients (25 %) at ultrasound. Correct determination of the position of the catheter in the lower abdomen by ultrasound had a sensitivity of 93 % (95 % CI 84 - 97 %), specificity of 95 % (95 % CI 72 - 100 %), positive predictive value of 99 % (95 % CI 91 - 100 %), negative predictive value of 78 % (95 %CI 56 - 92 %) and Kappa coefficient of 0.82 (95 % CI 0.67 - 0.96). In 10 out of 93 patients (11 %), there was a position mismatch between X-ray and ultrasound in an adjacent abdominopelvic region. Conclusion Our results suggest that abdomen X-ray for the evaluation of peritoneal catheter position can be replaced by ultrasound in experienced hands. This bedside diagnostic procedure might reduce costs, the time necessary for diagnosis and lifetime radiation exposure.

Assessment of impact of urbanisation on background radiation exposure and human health risk estimation in Kuala Lumpur, Malaysia

Kuala Lumpur has been undergoing rapid urbanisation process, mainly in infrastructure development. The opening of new township and residential in former tin mining areas, particularly in the heavy mineral- or tin-bearing alluvial soil in Kuala Lumpur, is a contentious subject in land-use regulation. Construction practices, i.e. reclamation and dredging in these areas are potential to enhance the radioactivity levels of soil and subsequently, increase the existing background gamma radiation levels. This situation is worsened with the utilisation of tin tailings as construction materials apart from unavoidable soil pollutions due to naturally occurring radioactive materials in construction materials, e.g. granitic aggregate, cement and red clay brick. This study was conducted to assess the urbanisation impacts on background gamma radiation in Kuala Lumpur. The study found that the mean value of measured dose rate was 251±6nGyh−1 (156–392nGyh−1) and 4 times higher than the world average value. High radioactivity levels of 238U (95±12Bqkg−1), 232Th (191±23Bqkg−1,) and 40K (727±130Bqkg−1) in soil were identified as the major source of high radiation exposure. Based on statistical ANOVA, t-test, and analyses of cumulative probability distribution, this study has statistically verified the dose enhancements in the background radiation. The effective dose was estimated to be 0.31±0.01mSvy−1 per man. The recommended ICRP reference level (1–20mSvy−1) is applicable to the involved existing exposure situation in this study. The estimated effective dose in this study is lower than the ICRP reference level and too low to cause deterministic radiation effects. Nevertheless based on estimations of lifetime radiation exposure risks, this study found that there was small probability for individual in Kuala Lumpur being diagnosed with cancer and dying of cancer.

Estimation of excess lifetime cancer risk and radiation hazard indices in southern Iraq

Relatively high activity concentrations of some radionuclides (226Ra, 238U, 232Th, and 40K) have been measured in surface and subsurface soils in areas (southern Iraq) where many warfare actions have taken place during the Iran–Iraq and Gulf wars. Such high activity concentrations might be related to the increase in cancerous injuries and birth defects recently reported. The study was aimed to estimate the activity concentrations of some nuclides and a comparison of results with international health hazard indices. In addition, the excess lifetime cancer risk (ELCR) was assessed. Soil samples were collected at three depths (0, 30, and 60 cm) in three locations in Abu Al Khasib and Ad Dayr in Basrah governorates. The average activity concentrations were estimated employing hyper-pure germanium HPGe gamma-ray detection technology. The values obtained in Abu Al Khasib were: 58.44 Bq/kg (226Ra), 43.56 Bq/kg (238U), 19.38 Bq/kg (232Th), and 321.76 Bq/kg (40K) whereas in Ad Dayr 45.71 Bq/kg (226Ra), 35.53 Bq/kg (238U), 20.33 Bq/kg (232Th), and 337.02 Bq/kg (40K). According to UNSCEAR (Sources and effects of ionizing radiations: a report on the effects of atomic radiation to the general assembly with scientific annexes, Annex B, United Nations, New York, 2000) report, higher levels of 226Ra, 238U concentrations than the world’s average values (35 Bq/kg) were observed in both locations. In addition, some radiation hazard indices were determined for both locations: average outdoor external dose (D out), average indoor external dose (D in), total average value of the external dose (D tot), average annual outdoor effective dose (E out), average annual indoor effective dose (E in), and averaged total annual effective dose (E tot). Values for D tot and E tot were higher than the worldwide median (143 nGy/h and 0.48 mSv/y, respectively) in both regions. The measured values of activity concentrations were also used to estimate the outdoor, indoor, and total ELCR. The ELCR values were higher than the worldwide averages. Further analyses and studies need to assess the real risks for human health and possible soil remediation.

Exposure to low dose computed tomography for lung cancer screening and risk of cancer: secondary analysis of trial data and risk-benefit analysis

Objective To estimate the cumulative radiation exposure and lifetime attributable risk of cancer incidence associated with lung cancer screening using annual low dose computed tomography (CT).Design Secondary analysis of data...

Lower thresholds for lifetime health effects in mammals from high-LET radiation – Comparison with chronic low-LET radiation

Lower threshold dose rates and confidence limits are quantified for lifetime radiation effects in mammalian animals from internally deposited alpha-emitting radionuclides. Extensive datasets on effects from internal alpha-emitters are compiled from the International Radiobiological Archives. In total, the compiled database includes 257 records, which are analyzed by means of non-parametric order statistics. The generic lower threshold for alpha-emitters in mammalian animals (combined datasets) is 6.6·10−5 Gy day−1. Thresholds for individual alpha-emitting elements differ considerably: plutonium and americium - 2.0·10−5 Gy day−1; radium – 2.1·10−4 Gy day−1. Threshold for chronic low-LET radiation is previously estimated at 1·10−3 Gy day−1.For low exposures, the following values of alpha radiation weighting factor wR for internally deposited alpha-emitters in mammals are quantified: wR(α) = 15 as a generic value for the whole group of alpha-emitters; wR(Pu) = 50 for plutonium; wR(Am) = 50 for americium; wR(Ra) = 5 for radium. These values are proposed to serve as radiation weighting factors in calculations of equivalent doses to non-human biota.The lower threshold dose rate for long-lived mammals (dogs) is significantly lower than comparing with the threshold for short-lived mammals (mice): 2.7·10−5 Gy day−1, and 2.0·10−4 Gy day−1, respectively. The difference in thresholds is exactly reflecting the relationship between the natural longevity of these two species.Graded scale of severity in lifetime radiation effects in mammals is developed, based on compiled datasets. Being placed on the severity scale, the effects of internal alpha-emitters are situated in the zones of considerably lower dose rates than effects of the same severity caused by low-LET radiation. RBE values, calculated for effects of equal severity, are found to depend on the intensity of chronic exposure: different RBE values are characteristic for low, moderate, and high lifetime exposures (30, 70, and 13, respectively).The results of the study provide a basis for selecting correct values of radiation weighting factors in dose assessment to non-human biota.

Imaging Surveillance After Proximal Aortic Operations: Is it Necessary?

Current guidelines for imaging surveillance after proximal aortic repair are not evidence based. This study sought to characterize the incidence and causes of reintervention after proximal aortic operations to provide data to guide the frequency and duration of postoperative surveillance. Data on all patients undergoing proximal aortic operations (ascending, with or without root, with or without aortic valve replacement, or with or without arch) during a 9-year period (n= 869) at a single institution were prospectively collected. Patients who required reintervention on the proximal or distal aorta were identified and causes for reintervention determined. Planned two-stage repairs and index procedures done at other hospitals were excluded. The primary end point was the time to the first reintervention, and competing-risk Cox regression was used to model reintervention risk. Reinterventions occurred in 4.3% of patients (n= 37), with 48.6% (n= 18) involving the proximal aorta and 51.4% (n= 19) the distal. Median time to reintervention was 2.8 years (interquartile range, 1.5 to 3.6 years). For index aneurysm cases, reintervention for aneurysm of the descending/thoracoabdominal aorta and root were most common. Of the 6 root aneurysms/pseudoaneurysms, 5 (83%) were due to degeneration of a stentless porcine aortic root. For index type A dissections, reintervention for aneurysm of the descending/thoracoabdominal aorta and arch were most common. The mean duration of follow up was 4.2 ± 2.5 years. The 9-year actuarial freedom from reintervention was 92.9%. Cox regression showed index type A dissection was a significant predictor of time to aortic reintervention (hazard ratio, 2.01; 95% confidence interval, 1.04 to 3.9; p= 0.038). Reinterventions after proximal aortic operations are uncommon; most occur within 3 years of the index operation and involve the proximal and distal aorta nearly equally. Patients with type A dissection or stentless porcine roots require aggressive surveillance, whereas a more liberal approach is suitable for patients without such risk factors. This strategy may reduce the lifetime radiation burden and health care costs.

Growth and spectral properties of KNd(WO4)2

Single crystal of KNd(WO4)2 has been grown by the flux method. The KNd(WO4)2 structure was analyzed using the single-crystal X-ray diffraction experiment. KNd(WO4)2 crystallizes in the scheelite-type structure with space C2/m, lattice parameters: a=10.1633Å, b=10.779Å, c=7.493Å, α=90.0°, β=125.988(2)°, γ=90.0°, V=664.19Å3, Z=4. The absorption spectrum and fluorescence spectrum are measured at room temperature. The spectrum properties of Nd3+ in KNd(WO4)2 crystal were investigated based on J-O theory, and the effective J-O parameters have been determined as: Ω2=1.18×10−20cm2, Ω4=7.38×10−20cm2, Ω6=3.05×10−20cm2. The absorption band at 588 and 806nm has a full width at half of 24 and 22nm, respectively. The strongest fluorescence spectrum-emission peak locates at 1059nm, which can be attribute to the 4F3/2–4I11/2 of emission band of Nd3+. The radiation lifetime is 93.4μs, and the emission cross-section calculated by F-L formula is 1.62×10−19cm2 at the wavelength of 1059nm.

PHIPS–HALO: the airborne Particle Habit Imaging and Polar Scattering probe – Part 1: Design and operation

Abstract. The number and shape of ice crystals present in mixed-phase and ice clouds influence the radiation properties, precipitation occurrence and lifetime of these clouds. Since clouds play a major role in the climate system, influencing the energy budget by scattering sunlight and absorbing heat radiation from the earth, it is necessary to investigate the optical and microphysical properties of cloud particles particularly in situ. The relationship between the microphysics and the single scattering properties of cloud particles is usually obtained by modelling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. There is a demand to obtain both information correspondently and simultaneously for individual cloud particles in their natural environment. For evaluating the average scattering phase function as a function of ice particle habit and crystal complexity, in situ measurements are required. To this end we have developed a novel airborne optical sensor (PHIPS-HALO) to measure the optical properties and the corresponding microphysical parameters of individual cloud particles simultaneously. PHIPS-HALO has been tested in the AIDA cloud simulation chamber and deployed in mountain stations as well as research aircraft (HALO and Polar 6). It is a successive version of the laboratory prototype instrument PHIPS-AIDA. In this paper we present the detailed design of PHIPS-HALO, including the detection mechanism, optical design, mechanical construction and aerodynamic characterization.

Cumulative radiation exposure and estimated lifetime cancer risk in multiple-injury adult patients undergoing repeated or multiple CTs.

To estimate the cumulative radiation exposure and lifetime attributable risk (LAR) of radiation-induced cancer from computed tomographic (CT) scanning of adult patients with multiple-injury traumas. The study comprises 328 multiple-injury adult patients who underwent diagnostic CT during 2013. Each patient's cumulative CT radiation exposure was calculated and the biological effects of ionizing radiation VII methodology was used to estimate the LAR of cancer incidence on the basis of sex and age at each exposure. The average cumulative dose per patient was 19.4mSv. One point five percent (5/328) of the patients received a cumulative effective dose ≥100mSv and 63.7% of patients received a cumulative effective dose ≤20mSv. The average LAR of cancer incidence was 0.14% or 1 in 714 patients. Only one patient had an LAR >1%, a man <30years of age. The group of major injuries [injury severity score (ISS) >15] had a statistically significantly greater accumulative effective dose and slightly greater LAR than the group of minor injuries (ISS ≤15). More than half of the multiple-injury trauma patients were classified as low risk cumulative effective dose (≤20mSv) and almost all patients had a low LAR risk of cancer incidence from CT studies. Patients who were at the highest risk of cancer from CT scans were those aged under 30years who had multiple or repeated scans, particularly in the trunk.

Vacancy behavior in Cu(In1 − xGax)Se2 layers grown by a three-stage coevaporation process probed by monoenergetic positron beams

Vacancy-type defects in Cu(In1−xGax)Se2 (x≅0.45 and 1) grown by a three-stage coevaporation process were probed using monoenergetic positron beams. Measurements of Doppler broadening spectra of the annihilation radiation and positron lifetime spectra showed that two different defect species coexist in the Cu(In1−xGax)Se2 layers, and these were identified as mono/divacancy-type defects and vacancy clusters, respectively. The vacancy clusters were mainly introduced during the third growth stage, and were located in the subsurface region. The concentration of the defects affected the short-circuit current density and the conversion efficiency of the solar cells. The defect concentration and their depth distributions varied depending on Se beam equivalent pressure, growth time, and post-growth annealing time. The behavior of the vacancy-type defects is discussed also with respect to results obtained using an electron probe micro-analyzer.

Radiation Resistant Magnets for J-PARC

Several species of radiation-resistant magnets were developed for J-PARC, a Japanese brand-new high-intensity accelerator complex, whose maximum beam power reaches 1 MW. The first development was polyimide insulation magnets. The ordinal epoxy resin was replaced by polyimide resin in order to improve its radiation lifetime up to 4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> Gy. Most accelerator magnets of J-PARC were assembled with polyimide insulation coils. Peripherals of polyimide insulation magnets, such as insulation water tubes, water valves, water gaskets, etc., were replaced also by ones made of inorganic materials. The second development was mineral insulation magnets. Magnet excitation coils were made of “Mineral Insulation Cable (MIC).” The copper conductor of MIC was surrounded by a thin MgO insulation layer, and the MgO layer was covered by a copper sheath. Several sizes of MIC cross section were developed for large and small magnets with various maximum currents from 1000 to 3000 A. Peripherals of magnets assembled with MIC coils were also made of completely inorganic materials. These MIC magnets were used at the downstream part of beam loss points such as the secondary particle production target of Hadron Experimental Facility. The R&D stories of the radiation-resistant magnets, including the present status of the magnet operation, are briefly summarized.

Estimates of Radiation Doses and Cancer Risk from Food Intake in Korea.

The aim of this study was to estimate internal radiation doses and lifetime cancer risk from food ingestion. Radiation doses from food intake were calculated using the Korea National Health and Nutrition Examination Survey and the measured radioactivity of 134Cs, 137Cs, and 131I from the Ministry of Food and Drug Safety in Korea. Total number of measured data was 8,496 (3,643 for agricultural products, 644 for livestock products, 43 for milk products, 3,193 for marine products, and 973 for processed food). Cancer risk was calculated by multiplying the estimated committed effective dose and the detriment adjusted nominal risk coefficients recommended by the International Commission on Radiation Protection. The lifetime committed effective doses from the daily diet are ranged 2.957-3.710 mSv. Excess lifetime cancer risks are 14.4-18.1, 0.4-0.5, and 1.8-2.3 per 100,000 for all solid cancers combined, thyroid cancer, and leukemia, respectively.

Effective dose reduction in spine radiographic imaging by choosing the less radiation-sensitive side of the body

Background ContextX-ray absorption is highest in the organs and tissues located closest to the radiation source. The photon flux that crosses the body decreases from the entry surface toward the image receptor. The internal organs absorb x-rays and shield each other during irradiation. Therefore, changing the x-ray projection angle relative to the patient for specific spine procedures changes the radiation dose that each organ receives. Every organ has different radiation sensitivity, so irradiation from different sides of the body changes the biological influence and radiation risk potential on the total body, that is the effective dose (ED). PurposeThe study aimed to determine the less radiation-sensitive sides of the body during lateral and anterior-posterior (AP) or posterior anterior (PA) directions. Study DesignThe study used exposure of patient phantoms and Monte Carlo simulation of the effective doses. Patient SampleCalculations for adults and 10-year-old children were included because the pediatric population has a greater lifetime radiation risk than adults. Outcome MeasuresPediatric and adult tissue and organ doses and ED from cervical, thoracic, and lumbar x-ray spine examinations were performed from different projections. MethodsStandard mathematical phantoms for adults and 10-year-old children, using PCXMC 2.0 software based on Monte Carlo simulations, were used to calculate pediatric and adult tissue and organ doses and ED. The study was not funded. The authors have no conflicts of interest to declare. ResultsSpine x-ray exposure from various right (RT) LAT projection angles was associated with lower ED compared with the same left (LT) LAT projections (up to 28% and 27% less for children aged 10 and adults, respectively). The PA spine projections showed up to 64% lower ED for children aged 10 and 65% for adults than AP projections. The AP projection at the thoracic spine causes an excess breast dose of 543.3% and 597.0% for children aged 10 and adults, respectively. ConclusionsRadiation ED in spine procedures can be significantly reduced by performing x-ray exposures through the less radiation-sensitive sides of the body, which are PA in the frontal position and right lateral in the lateral position.

Computed tomography of the chest: I. Basic principles

### Key points The conventional chest radiograph superimposes a three-dimensional image onto a two-dimensional surface, so limiting its clinical usefulness. Since its introduction in 1971, X-ray computed tomography (CT) has rapidly evolved into an essential diagnostic imaging tool that forms a cross-sectional image, avoiding the super-imposition of structures that occurs in conventional chest imaging, with a >10-fold increase in attenuation sensitivity. Although CT imaging is reported by radiologists, it is important for both anaesthetists and intensivists to be able to interpret the scans, as reporting facilities may not be immediately available. Furthermore, the radiologist may not fully report all facets of a detailed scan and further information may be acquired by a physician with the ability to interpret CT scans. This is the first in a series of two articles written for anaesthetists and intensivists covering both thoracic anatomy and pathology as it relates to CT. A CT scanner makes many measurements, from different rotational angles, of X-ray attenuation ( weakening in force or intensity ) through the cross-sectional plane of the thorax. It then uses these data to reconstruct a digital representation of the cross-section with …