Acceptability of adding a non-contrast abdominal CT scan to screen for kidney cancer and other abdominal pathology within a community-based CT screening programme for lung cancer: A qualitative study.

OBJECTIVES: The Yorkshire Kidney Screening Trial (YKST) is a feasibility study of adding non-contrast abdominal CT scanning to screen for kidney cancer and other abdominal malignancies to community-based CT screening for lung cancer within the Yorkshire Lung Screening Trial (YLST). This study explored the acceptability of the combined screening approach to participants and healthcare professionals (HCPs) involved in the trial. METHODS: We conducted semi-structured interviews with eight HCPs and 25 participants returning for the second round of scanning within YLST, 20 who had taken up the offer of the additional abdominal CT scan and five who had declined. Transcripts were analysed using thematic analysis, guided by the Theoretical Framework of Acceptability. RESULTS: Overall, combining the offer of a non-contrast abdominal CT scan alongside the low-dose thoracic CT was considered acceptable to participants, including those who had declined the abdominal scan. The offer of the additional scan made sense and fitted well within the process, and participants could see benefits in terms of efficiency, cost and convenience both for themselves as individuals and also more widely for the NHS. Almost all participants made an instant decision at the point of initial invitation based more on trust and emotions than the information provided. Despite this, there was a clear desire for more time to decide whether to accept the scan or not. HCPs also raised concerns about the burden on the study team and wider healthcare system arising from additional workload both within the screening process and downstream following findings on the abdominal CT scan. CONCLUSIONS: Adding a non-contrast abdominal CT scan to community-based CT screening for lung cancer is acceptable to both participants and healthcare professionals. Giving potential participants prior notice and having clear pathways for downstream management of findings will be important if it is to be offered more widely.

An evaluation of CT radiation doses within the Yorkshire Lung Screening Trial.

OBJECTIVES: To evaluate radiation doses for all low-dose CT scans performed during the first year of a lung screening trial. METHODS: For all lung screening scans that were performed using a CT protocol that delivered image quality meeting the RSNA QIBA criteria, radiation dose metrics, participant height, weight, gender, and age were recorded. Values of volume CT dose index (CTDIvol) and dose length product (DLP) were evaluated as a function of weight in order to assess the performance of the scan protocol across the participant cohort. Calculated effective doses were used to establish the additional lifetime attributable cancer risks arising from trial scans. RESULTS: Median values of CTDIvol, DLP, and effective dose (IQR) from the 3521 scans were 1.1 mGy (0.70), 42.4 mGycm (24.9), and 1.15 mSv (0.67), whilst for 60-80kg participants the values were 1.0 mGy (0.30), 35.8 mGycm (11.4), and 0.97 mSv (0.31). A statistically significant correlation between CTDIvol and weight was identified for males (r = 0.9123, P < .001) and females (r = 0.9052, P < .001), however, the effect of gender on CTDIvol was not statistically significant (P = .2328) despite notable differences existing at the extremes of the weight range. The additional lifetime attributable cancer risks from a single scan were in the range 0.001%-0.006%. CONCLUSIONS: Low radiation doses can be achieved across a typical lung screening cohort using scan protocols that have been shown to deliver high levels of image quality. The observed dose levels may be considered as typical values for lung screening scans on similar types of scanners for an equivalent participant cohort. ADVANCES IN KNOWLEDGE: Presentation of typical radiation dose levels for CT lung screening examinations in a large UK trial. Effective radiation doses can be of the order of 1 mSv for standard sized participants. Lifetime attributable cancer risks resulting from a single low-dose CT scan did not exceed 0.006%.

The Yorkshire Kidney Screening Trial (YKST): protocol for a feasibility study of adding non-contrast abdominal CT scanning to screen for kidney cancer and other abdominal pathology within a trial of community-based CT screening for lung cancer.

INTRODUCTION: Kidney cancer (renal cell cancer (RCC)) is the seventh most common cancer in the UK. As RCC is largely curable if detected at an early stage and most patients have no symptoms, there is international interest in evaluating a screening programme for RCC. The Yorkshire Kidney Screening Trial (YKST) will assess the feasibility of adding non-contrast abdominal CT scanning to screen for RCC and other abdominal pathology within the Yorkshire Lung Screening Trial (YLST), a randomised trial of community-based CT screening for lung cancer. METHODS AND ANALYSIS: In YLST, ever-smokers aged 55-80 years registered with a general practice in Leeds have been randomised to a Lung Health Check assessment, including a thoracic low-dose CT (LDCT) for those at high risk of lung cancer, or routine care. YLST participants randomised to the Lung Health Check arm who attend for the second round of screening at 2 years without a history of RCC or abdominal CT scan within the previous 6 months will be invited to take part in YKST. We anticipate inviting 4700 participants. Those who consent will have an abdominal CT immediately following their YLST thoracic LDCT. A subset of participants and the healthcare workers involved will be invited to take part in a qualitative interview. Primary objectives are to quantify the uptake of the abdominal CT, assess the acceptability of the combined screening approach and pilot the majority of procedures for a subsequent randomised controlled trial of RCC screening within lung cancer screening. ETHICS AND DISSEMINATION: YKST was approved by the North West-Preston Research Ethics Committee (21/NW/0021), and the Health Research Authority on 3 February 2021. Trial results will be disseminated at clinical meetings, in peer-reviewed journals and to policy-makers. Findings will be made available to participants via the study website (www.YKST.org). TRIAL REGISTRATION NUMBERS: NCT05005195 and ISRCTN18055040.

Should Radiation Exposure be an Issue of Concern in Children With Multiple Trauma?

OBJECTIVE: The aims of this study were 3-fold: first, establish the level of radiation exposure experienced by the pediatric trauma patients; second, model the level of risk of developing fatal carcinogenesis; and third, test whether pattern of injury was predictive of the level of exposure. SUMMARY BACKGROUND DATA: There are certain conditions that cause children to be exposed to increased radiation, that is, scoliosis, where level of radiation exposure is known. The extent that children are exposed to radiation in the context of multiple traumas remains unclear. METHODS: Patients below the age of 16 years and with an Injury Severity Score (ISS) ≥10, treated by a Major Trauma Center for the period January 2008 to December 2018 were identified. The following data were extracted for the year following the patient's injury: number, doses, and type of radiological examination.The sex and age of the patient was taken into account in the calculation of the risk of developing a carcinogenesis. RESULTS: The median radiation dose of the 425 patients identified in the 12 months following injury, through both CT and radiographs, was 24.3 mSv. Modeling the predictive value of pattern of injury and other relevant clinical values, ISS was proportionately predictive of cumulative dose received. CONCLUSION: A proportion of younger polytrauma patients were exposed to high levels of radiation that in turn mean an increased risk of carcinogenesis. However, the ISS, age, injury pattern, and length of hospital stay are predictive of both risks, enabling monitoring and patient advisement of the risks.

Establishing scanning protocols for a CT lung cancer screening trial in the UK.

OBJECTIVES: To develop a CT scanning protocol for lung cancer screening which achieved low radiation dose and a high level of objectively assessed image quality. METHODS: An anthropomorphic chest phantom and a commercially available lung screening image quality phantom were scanned on a series of scan protocols from a previous UK lung screening pilot and on an alternative protocol. The chest phantom scans were used to assess the CT dose metrics on community-based mobile CT scanners and comparisons were made with published recommended doses. Scans of the image quality phantom were objectively assessed against the RSNA Quantitative Imaging Biomarkers Alliance (QIBA) recommendations. Protocol adjustments were made to ensure that the recommended dose and image quality levels were both achieved. RESULTS: The alternative scan protocol yielded doses up to 72% lower than on the previously used protocols with a CTDIvol of 0.6mGy for the 55 kg equivalent phantom and 1.3mGy with an additional 6 cm of tissue equivalent material in place. Scans on the existing protocols failed on two of the QIBA image quality metrics (edge enhancement and 3D resolution aspect ratio). Following adjustments to the reconstruction parameters of the resulting image quality met all six QIBA recommendations. Radiologist review of phantom images with this scan protocol deemed them suitable for a lung screening trial. CONCLUSIONS: Scan protocols yielding low radiation doses and high levels of objectively assessed image quality which meet published criteria can be established through the use of specific anthropomorphic and image quality phantoms, and are deliverable in community-based lung cancer screening. ADVANCES IN KNOWLEDGE: Development of a standard methodology for establishing CT lung screening scanning protocolsUse of QIBA recommendations as objective image quality metricsStandardised lung phantoms are essential tools for setting up lung screening protocols.

Radiation dose reduction in CT-guided cryoablation of renal tumors.

PURPOSE: We aimed to evaluate the effect on the radiation dose to the patient by reducing the tube current during the placement of the ablation needles (reduced dose group) compared with the patient doses delivered when scanning at the standard fully diagnostic level (full dose group) in computed tomography (CT)-guided percutaneous cryoablation. METHODS: We conducted a retrospective study of 103 patients undergoing cryoablation in a tertiary cancer center. Overall, 62 patients were scanned with standard exposure parameters (full dose group) set on a 64-slice multidetector CT scanner, while 41 patients were scanned on a reduced dose protocol. Dose levels were retrieved from the hospital picture and archiving communication system including the volumetric CT dose index (CTDIvol), total dose length product (DLP), length of cryoablation procedure, number of cryoablation needles and patient size. Wilcoxon Mann-Whitney (rank-sum) tests were used to compare the median DLP, CTDIvol and skin dose between the two groups. RESULTS: Median total DLP for the full dose group was 6025 mGy•cm (1909-13353 mGy•cm) compared with 3391 mGy•cm (1683-6820 mGy•cm) for the reduced dose group. The reduced dose group had a 44% reduction in total DLP and 42% reduction in total CTDIvol (p < 0.001). The estimated skin doses were 384 mGy for the full dose group and 224 mGy for the reduced dose group (42% reduction) (p < 0.001). At 12-month follow-up, the technical success for the full dose (n=62) was 97% with 2 patients requiring a further cryoablation treatment for residual tumor. The technical success for the reduced dose group (n=41) was 100%. CONCLUSION: CT dose reduction technique during image-guided cryoablation treatment of renal tumors can achieve significant radiation dose reduction whilst maintaining sufficient image quality.

IPEM Topical Report: An evidence and risk assessment based analysis of the efficacy of quality assurance tests on fluoroscopy units-part II; image quality.

This work aims to assess the efficacy of x-ray quality assurance tests undertaken on fluoroscopy units in the UK. Information was gathered on the results of image quality tests recommended by the reports of the Institute of Physics and Engineering in Medicine, and those additionally undertaken by medical physics departments. The assessment of efficacy considers the frequency with which a test result breaches the remedial level or other relevant threshold where applicable. The third quartile of those results exceeding the remedial level or threshold is used to estimate the severity of such a breach in terms of potential impact on patient dose and image quality. A risk assessment approach is then used to recommend to what degree, if any, the test should be included in an on-going test regimen. Data was analysed from 469 testing sessions to 337 unique fluoroscopy units throughout the UK. Across all tests, the rate with which the remedial level was exceeded varied from 0-10.6%, with severity ranging from little or none to major degradation to image quality or significant increase on population dose. Where possible, the data has also been used to produce representative ranges for the results of image quality tests. These could be useful as an up to date comparator for those sites considering the purchase of or commissioning new equipment. Overall the results indicate a wide range for the efficacy of those tests undertaken at present; this can be used to review local test protocols and to inform future changes to national guidance in the UK. The results also highlight some tests where measurement technique varies significantly throughout the UK, making any valid comparison difficult. This may indicate a need for further guidance on how best to undertake these tests.

An Estimation of Lifetime Fatal Carcinogenesis Risk Attributable to Radiation Exposure in the First Year Following Polytrauma: A Major Trauma Center's Experience Over 10 Years.

BACKGROUND: The utilization of medical imaging continues to rise, including routine use in major trauma centers. The aims of this study were to estimate the amount of radiation exposure from radiographic imaging and the associated fatal carcinogenesis risk among patients treated for polytrauma at 1 institution. METHODS: Included were patients who were admitted to our institution with an Injury Severity Score (ISS) of ≥16 during the period of January 2007 to December 2016. Records of patients were reviewed to assess exposures to radiation (excluding fluoroscopy) in the 12 months following injury. The risk of developing a fatal cancer of any type was modeled using patient age and sex, on the basis of the International Commission on Radiological Protection (ICRP) recommendations. Estimates of cancer risk were based on the exposure received and then imported into previously developed models. RESULTS: Overall, 2,394 patients, with a mean ISS of 28.66 (range, 17 to 66), were included in our analysis. The mean total radiation dose received was 30.45 mSv and the median dose was 18.46 mSv. One hundred and fifteen patients (4.8% of the cohort) received ≥100 mSv of radiation. The total patient group had a 3.56% mean risk of fatal carcinogenesis of any type that related solely to medical exposure of radiation as a result of their injuries. In their lifetime, 85 patients would be expected to develop cancer as a result of medical imaging that they had undergone in the year following their accident. The ISS and the body region of injury contributing to the ISS were predictive of the level of radiation exposure. CONCLUSIONS: Those involved in trauma care can use the ISS and body region to predict radiation exposure and the risk of fatal carcinogenesis of any type. We found that, for injuries to the limb and pelvis, the greater the severity of injury, the greater the radiation exposure and fatal carcinogenesis risk. However, this study does not provide an actuarial analysis. It is unknown how many patients in the study went on to develop cancer. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

IPEM Topical Report: an evidence and risk assessment based analysis of the efficacy of quality assurance tests on fluoroscopy units-part I; dosimetry and safety.

This work aims to assess the efficacy of x-ray quality assurance tests undertaken on fluoroscopy units in the UK. Information was gathered on the results of dosimetry and safety tests recommended by the reports of the Institute of Physics and Engineering in Medicine, and those additionally undertaken by medical physics departments. The assessment of efficacy considers the frequency with which a test result breaches the remedial level or other relevant threshold where applicable. The third quartile of those results exceeding the remedial level or threshold is used to estimate the severity of such a breach in terms of potential impact on patient dose and image quality. A risk assessment approach is then used to recommend to what degree, if any, the test should be included in an on-going test regimen. Data was analysed from 468 testing sessions to 336 unique fluoroscopy units throughout the UK. Across all tests, the rate with which the remedial level was exceeded varied from 0%-29.5%, with severity ranging from little or none to major degradation to image quality or significant increase on population dose. Where possible, the data has also been used to produce representative ranges for the results of dosimetric tests. These could be useful as an up to date comparator for those sites considering the purchase of or commissioning new equipment. Overall the results indicate a wide range for the efficacy of those tests undertaken at present; this can be used to review local test protocols and to inform future changes to national guidance in the UK. The results also highlight some tests where measurement technique varies significantly throughout the UK, making any valid comparison difficult. This may indicate a need for further guidance on how best to undertake these tests.

IPEM Topical Report: an evidence and risk assessment based analysis of the efficacy of tube and generator quality assurance tests on general x-ray units.

This work aims to assess the efficacy of current x-ray quality assurance (QA) testing regimes on tube and generator systems for general radiographic usage in the UK. 1393 sets of QA results data from nine UK medical physics departments were collected and analysed. Test failure rates ranged from 0% to 39% and were used to assess the likelihood of the test finding a fault. The magnitude of the recorded faults were used to assess the severity of the failure with due consideration to its impact on image quality and patient dose. The severity and likelihood of the faults were used along with a risk matrix to assess the efficacy of each test. Eleven tests were graded 'orange' (indicating an effective test that should be continued), four tests were graded 'yellow' (indicating a less effective test that may be continued with a lower frequency considered) and four tests were graded green (indicating a low efficacy test that could be removed from test regimes).

A national survey of computed tomography doses in hybrid PET-CT and SPECT-CT examinations in the UK.

OBJECTIVES: The aim of this study was to conduct a nationwide survey of computed tomography (CT) doses for a wide range of PET-CT and single photon emission computed tomography-computed tomography (SPECT-CT) imaging procedures, with the aim of generating proposed UK national diagnostic reference levels (NDRLs). METHODS: CT protocol and dosimetry data for three PET-CT and seven SPECT-CT examinations were gathered from centres across the UK. Data were divided according to CT purpose (attenuation correction, localization or diagnostic) and third quartile values of scanner average dose metrics were used to generate suggested NDRLs for a range of examination and CT purpose combinations. Achievable doses were also established from the median of the dose distributions. RESULTS: Data were obtained from 47 centres, allowing suggested NDRLs to be produced for fluorine-18-fluorodeoxyglucose half-body PET-CT, and parathyroid, post-thyroid ablation, meta-iodobenzylguanidine/octreotide, cardiac and bone SPECT-CT examinations.Variations in dose of up to a factor of 35 were observed for a given examination/CT purpose combination. For fluorine-18-fluorodeoxyglucose half-body PET-CT examination dose levels for the three CT purposes overlapped, which highlights the variability in the way in which CT purposes are interpreted across the UK. This lack of standardization is believed to be the largest contributor to the dose variations that were observed. The survey highlighted the need for targeted optimization work in many centres. CONCLUSION: Suggested UK NDRLs and achievable doses for six common PET-CT and SPECT-CT examinations have been established as a result of this study.

A routine quality assurance test for CT automatic exposure control systems.

The study purpose was to develop and validate a quality assurance test for CT automatic exposure control (AEC) systems based on a set of nested polymethylmethacrylate CTDI phantoms. The test phantom was created by offsetting the 16 cm head phantom within the 32 cm body annulus, thus creating a three part phantom. This was scanned at all acceptance, routine, and some nonroutine quality assurance visits over a period of 45 months, resulting in 115 separate AEC tests on scanners from four manufacturers. For each scan the longitudinal mA modulation pattern was generated and measurements of image noise were made in two annular regions of interest. The scanner displayed CTDIvol and DLP were also recorded. The impact of a range of AEC configurations on dose and image quality were assessed at acceptance testing. For systems that were tested more than once, the percentage of CTDIvol values exceeding 5%, 10%, and 15% deviation from baseline was 23.4%, 12.6%, and 8.1% respectively. Similarly, for the image noise data, deviations greater than 2%, 5%, and 10% from baseline were 26.5%, 5.9%, and 2%, respectively. The majority of CTDIvol and noise deviations greater than 15% and 5%, respectively, could be explained by incorrect phantom setup or protocol selection. Barring these results, CTDIvol deviations of greater than 15% from baseline were found in 0.9% of tests and noise deviations greater than 5% from baseline were found in 1% of tests. The phantom was shown to be sensitive to changes in AEC setup, including the use of 3D, longitudinal or rotational tube current modulation. This test methodology allows for continuing performance assessment of CT AEC systems, and we recommend that this test should become part of routine CT quality assurance programs. Tolerances of ± 15% for CTDIvol and ± 5% for image noise relative to baseline values should be used.

Quality control within the multicentre perfusion CT study of primary colorectal cancer (PROSPeCT): results of an iodine density phantom study.

OBJECTIVES: To assess the cross-centre consistency of iodine enhancement, contrast-to-noise ratio and radiation dose in a multicentre perfusion CT trial of colorectal cancer. MATERIALS AND METHODS: A cylindrical water phantom containing different iodine inserts was examined on seven CT models in 13 hospitals. The relationship between CT number (Hounsfield units, HU) and iodine concentration (milligrams per millilitre) was established and contrast-to-noise ratios (CNRs) calculated. Radiation doses (CTDIvol, DLP) were compared across all sites. RESULTS: There was a linear relationship between CT number and iodine density. Iodine enhancement varied by a factor of at most 1.10, and image noise by at most 1.5 across the study sites. At an iodine concentration of 1 mg ml(-1) and 100 kV, CNRs ranged from 3.6 to 4.8 in the 220-mm phantom and from 1.4 to 1.9 in the 300-mm phantom. Doses varied by a factor of at most 2.4, but remained within study dose constraints. Iterative reconstruction algorithms did not alter iodine enhancement but resulted in reduced image noise by a factor of at most 2.2, allowing a potential dose decrease of at most 80% compared to filtered back projection (FBP). CONCLUSIONS: Quality control of CT performance across centres indicates that CNR values remain relatively consistent across all sites, giving acceptable image quality within the agreed dose constraints. KEY POINTS: Quality control is essential in a multicentre setting to enable CT quantification. CNRs in a body-sized phantom had the recommended value of at least 1.5. CTDIs and DLPs varied by factors of 1.8 and 2.4 respectively.

Computed tomography automatic exposure control techniques in 18F-FDG oncology PET-CT scanning.

OBJECTIVES: Computed tomography (CT) automatic exposure control (AEC) systems are now used in all modern PET-CT scanners. A collaborative study was undertaken to compare AEC techniques of the three major PET-CT manufacturers for fluorine-18 fluorodeoxyglucose half-body oncology imaging. MATERIALS AND METHODS: An audit of 70 patients was performed for half-body CT scans taken on a GE Discovery 690, Philips Gemini TF and Siemens Biograph mCT (all 64-slice CT). Patient demographic and dose information was recorded and image noise was calculated as the SD of Hounsfield units in the liver. A direct comparison of the AEC systems was made by scanning a Rando phantom on all three systems for a range of AEC settings. RESULTS: The variation in dose and image quality with patient weight was significantly different for all three systems, with the GE system showing the largest variation in dose with weight and Philips the least. Image noise varied with patient weight in Philips and Siemens systems but was constant for all weights in GE. The z-axis mA profiles from the Rando phantom demonstrate that these differences are caused by the nature of the tube current modulation techniques applied. The mA profiles varied considerably according to the AEC settings used. CONCLUSION: CT AEC techniques from the three manufacturers yield significantly different tube current modulation patterns and hence deliver different doses and levels of image quality across a range of patient weights. Users should be aware of how their system works and of steps that could be taken to optimize imaging protocols.

Cardiac computed tomography and conventional angiography in the diagnosis of congenital cardiac disease in children: recent trends and radiation doses.

BACKGROUND: The use of imaging that employs ionising radiation is increasing in the setting of paediatric cardiology. Children's high radiosensitivity and the lack of contemporary radiation data warrant a review of the radiation doses from the latest "state-of-the-art" angiography and computed tomography systems. OBJECTIVES: In children aged less than 16 years with congenital cardiac disease, we aimed to report: recent trends in the use of diagnostic angiography and cardiac dual-source computed tomography; the characteristics, lesions, and imaging histories of patients undergoing these procedures; and the average radiation doses imparted by each modality. STUDY DESIGN: Retrospective review of consecutive cases undergoing cardiac computed tomography or diagnostic angiography in a teaching hospital between January, 2008 and December, 2009. Radiation doses were converted to effective doses (millisievert) using published conversion factors. RESULTS: Angiography was performed 3.7 times more often than computed tomography. Computed tomography examinations increased by 92.5%, whereas angiography decreased by 26.4% in 2009 compared with 2008. Patients undergoing computed tomography were younger and weighed less than those undergoing angiography, but lesions were similar between the 2 groups. Multiple lifetime angiography was more prevalent than multiple lifetime computed tomography (p < 0.001). The median procedural dose - range - from angiography and computed tomography was 5 (0.2-27.8) and 1.7 (0.5-9.5) millisieverts, respectively (p < 0.001). CONCLUSION: Despite not being completely analogous investigations, computed tomography should be considered prior to angiography and not withheld on radiation dose concerns, given that it imparts lower and more consistent doses than conventional angiography.