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.

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).

The Acceptability of Iterative Reconstruction Algorithms in Head CT: An Assessment of Sinogram Affirmed Iterative Reconstruction (SAFIRE) vs. Filtered Back Projection (FBP) Using Phantoms.

BACKGROUND: Computed tomography (CT) is the primary imaging investigation for many neurologic conditions with a proportion of patients incurring cumulative doses. Iterative reconstruction (IR) allows dose optimization, but head CT presents unique image quality complexities and may lead to strong reader preferences. OBJECTIVES: This study evaluates the relationships between image quality metrics, image texture, and applied radiation dose within the context of IR head CT protocol optimization in the simulated patient setting. A secondary objective was to determine the influence of optimized protocols on diagnostic confidence using a custom phantom. METHODS AND SETTING: A three-phase phantom study was performed to characterize reconstruction methods at the local reference standard and a range of exposures. CT numbers and pixel noise were quantified supplemented by noise uniformity, noise power spectrum, contrast-to-noise ratio (CNR), high- and low-contrast resolution. Reviewers scored optimized protocol images based on established reporting criteria. RESULTS: Increasing strengths of IR resulted in lower pixel noise, lower noise variance, and increased CNR. At the reference standard, the image noise was reduced by 1.5 standard deviation and CNR increased by 2.0. Image quality was maintained at ≤24% relative dose reduction. With the exception of image sharpness, there were no significant differences between grading for IR and filtered back projection reconstructions. CONCLUSIONS: IR has the potential to influence pixel noise, CNR, and noise variance (image texture); however, systematically optimized IR protocols can maintain the image quality of filtered back projection. This work has guided local application and acceptance of lower dose head CT protocols.

Increasing source-to-image distance to reduce radiation dose from digital radiography pelvic examinations.

PURPOSE: To investigate the effects of increasing source-to-image distance (SID) on radiation dose and image quality for digital radiography examinations of the pelvis. METHODS: Using a Carestream DirectView DR 7500 unit, anteroposterior pelvic images were obtained on 97 consecutive patients at a standard 115-cm SID (group 1). Ninety-nine patients were examined using the same equipment and acquisition parameters but with the maximum achievable SID (group 2). For each examination, tube potential, milliampere seconds, SID, and source-to-skin distances were recorded. This facilitated the calculation of entrance surface dose, including backscatter, and effective dose using Quality Assurance Dose Data System software. The resultant images were independently assessed for image quality by 3 blinded observers-2 reporting radiographers and 1 consultant radiologist. Image quality was graded using an established scoring system, which assessed image quality at multiple anatomical locations. RESULTS: For group 1, median (interquartile range [IQR]; the median value is presented with the corresponding interquartile range in parentheses) entrance surface dose with backscatter was 1.95 mGy (1.23 mGy-3.10 mGy), which was lower by 1.15 mGy (0.78 mGy-2.22 mGy) for the increased SID group (22 patients at 135 cm, 77 patients at 144 cm) (Mann-Whitney U test, P < .001). Effective dose calculations generated a median (IQR) of 0.32 mSv (0.13 mSv-0.52 mSv) for group 1 and a lower median of 0.19 mSv (0.13 mSv-0.37 mSv) for group 2 (P < .001). No observers (intraclass correlation coefficient = 0.675) found a significant change in image quality by increasing SID (group 1, 2.0 ± 1.8; group 2, 1.6 ± 1.4; P > .05) when comparing the difference in image quality scores with the maximum score available. DISCUSSION: Our results demonstrate a reduction in entrance surface dose, including backscatter and effective dose, of 39% and 41%, respectively, when operating at extended SIDs. Results were generated from a clinically based study and included a wide spectrum of patients. Multiple regression confirmed that increasing the SID contributes to a dose reduction. Increasing SID is a simple and cost-effective method for reducing radiation dose and can be applied to all patients by all radiographers and with all commercially available digital radiography units. CONCLUSION: For digital pelvic radiography, increasing SID is a potential method for reducing entrance surface and effective radiation doses without compromising image quality.

Digital pelvic radiography: increasing distance to reduce dose.

PURPOSE: To investigate the effect of varying source-to-image distance (SID) on image quality and radiation dose using direct digital radiography (DR). METHODS: An anthropomorphic pelvic phantom was positioned for a standard anteroposterior DR examination. The SID was initially set at 100 cm, and the tube potential remained constant at 80 kVp. Two exposures were taken at this SID, and the entrance surface dose (ESD) and effective dose (ED) were calculated. Images were sent to a reporting-grade picture archiving and communication system workstation for image quality analysis. The SID was then varied by 10-cm intervals, up to its maximum (80 cm to 147 cm), with 2 exposures taken for each interval. Grid usage also was varied to determine its effect on radiation dose and image quality. Image quality was assessed by 4 observers (2 images per SID interval) who were blinded to the measurements, using a rating system adapted from the European Guidelines on Quality Criteria for Diagnostic Radiographic Images. RESULTS: Increasing SID results in lower ESD and ED compared with the standard 100-cm SID (147 cm: 2.56 mGy and 0.44 mSv, respectively, vs 100 cm: 3.00 mGy and 0.51 mSv, respectively; P<.05). Reduction of the SID resulted in an increased ESD and ED (80 cm: 3.79 mGy and 0.65 mSv, respectively; P<.05). Analysis of the resultant images demonstrated a statistically nonsignificant minor increase in image quality when increasing SID (P=.276). Image quality for 60 cm, 80 cm, 100 cm, 120 cm, 140 cm, and 147 cm was given a mean score of 17.5, 30, 31, 33, 33, and 32, respectively. Removal of the grid resulted in lower image quality but a significantly lower overall ESD and ED. CONCLUSION: Significant reductions in ESD and ED can be achieved, without loss of image quality, with a larger-than-normal SID for AP pelvic DR examinations.

IT-driven patient safety at the heart of radiology service improvement.

Patient safety is a fundamental requirement of modern health-care systems and the application of information technology (IT) to this activity should have improvements in the area as one of its goals. Indeed, ensuring that the diagnostic IT strategy is optimized, for example, the use of IT in service redesign or data analysis, forms one of the main platforms for the National Framework for Service Improvement in Radiology. This paper presents both the concept behind and the results of a project that has been under way in the UK involving St Helens and Knowsley NHS Trust and IRS Ltd concerned with implementing effective IT-driven scientific support in the field of medical radiation protection. Locally developed software is employed in assessing, managing, and analysing patient dose data arising from X-ray examinations performed in the busy department of a large district general hospital (DGH). Such data are analysed in a variety of ways, for example, over time and according to location (department or X-ray room). This analysis not only provides a measure of performance against nationally agreed dose reference levels (DRLs) but also enables a detailed analysis of any variations as well as the establishment of local DRLs (performance indicators). This process provides quantitative input to management strategies aimed at service improvement. Such strategies are geared towards the support of the Ionizing Radiations (Medical Exposures) Regulations 2000 as well as implementation of quality-management principles at the heart of radiology practices.