Evaluation of the performance of digital x-ray systems in pelvis radiography.

The aim of this study was to investigate the performance of eight digital radiography systems and to optimise the dose-image quality relationship for digital pelvis radiography. The study involved eight digital radiography systems used for general examinations at Vilnius University Hospital Santaros Klinikos. An anthropomorphic pelvic phantom (CIRS, US) was used to simulate a patient undergoing clinical pelvis radiography. Dose quantities entrance surface dose, dose area product (DAP) and exposure parameters (kVp, mA, mAs) were measured and the effects on the images were evaluated, considering physical contrast to noise ratio (CNR) and observer-based evaluations as image quality metrics. Increasing the tube voltage by 5 kVp from standard protocol led to a reduction in radiation dose (DAP) by 12%-20% with a slight impact on image quality (CNR decreases by 2%-10%). There was an inter-observer variability in image rating across different equipment (kappa value between 0 and 0.3); however, both observers agreed that increasing kVp up to 85-90 kV had no effect on perceived image quality. The results indicate that optimisation strategies should be tailored specifically for each x-ray system since significant performance differences and wide variations in radiation dose exist across various digital radiography systems used in clinical settings. The use of high kVp can be used for dose optimisation in digital pelvis radiography without compromising image diagnostic accuracy.

Dose optimisation in paediatric radiography - Using regression models to investigate the relative impact of acquisition factors on image quality and radiation dose.

OBJECTIVE: To investigate the optimum pelvis X-ray acquisition factors for a 10-year-old child. Secondly, to evaluate the impact of each acquisition factor on image quality (IQ) and radiation dose. METHOD: Images were acquired using a pelvis phantom and a range of acquisition parameters; e.g. tube potential, additional filtration and source-to-image distance (SID). Automatic exposure control (AEC) was used with two orientations (head towards/away from two outer chambers) and three different chamber selections. Visual IQ was evaluated using relative and absolute-VGA methods. Radiation doses were measured by placing a dosimeter on the anterior surface of the phantom. Regression analysis was used to determine optimum parameters. RESULTS: The optimised technique (178.8 µGy), with diagnostic IQ, was with 89kVp, 130 cm SID and with 1 mm Al + 0.1 mm Cu filtration. This technique was with the head towards the two outer AEC chambers. Regression analysis showed that SID had the lowest impact on IQ (ß = 0.002 95% CI -0.001 to 0.005) and dose (ß = -0.96 95% CI -0.40 to -1.53). The impact of filtration on dose (ß = -76.24 95% CI -86.76 to -85.72) was higher than tube potential (ß = -13.44 95% CI -14.34 to -12.53). The following impact ratios were higher on IQ than radiation dose: filtration/kVp; 11.28 times, filtration/SID; 7.01 times and kVp/SID; 0.62 times. CONCLUSION: Optimised parameters were identified as 89 kVp, 130 cm SID and with 1 mm Al + 0.1 mm Cu additional filtration. Regression analysis demonstrated that filtration and tube potential had the greatest effect on radiation dose and IQ, respectively.

Impact of acquisition parameters on dose and image quality optimisation in paediatric pelvis radiography-A phantom study.

PURPOSE: Within paediatric pelvis imaging there is a lack of systematic dose optimisation studies which consider age and size variations. This paper presents data from dose optimisation studies using digital radiography and pelvis phantoms representing 1 and 5-year-old children. MATERIAL AND METHOD: Dose optimisation included assessments of image quality and radiation dose. Systematic variations using a factorial design for acquisition factors (kVp, mAs, source-detector distance [SDD] and filtration) were undertaken to acquire AP pelvis X-ray images. Perceptual image quality was assessed using a relative and absolute visual grading assessment (VGA) method. Radiation doses were measured by placing a dosimeter at the radiographic centring point on the surface of each phantom. Statistical analyses for determining the optimised parameters included main effects analysis. RESULTS: Optimised techniques, with diagnostically acceptable image quality, for each paediatric age were: 1-year-old; 65 kVp, 2 mAs and 115 cm SDD, while, 5-year-old; 62 kVp, 8 mAs and 130 cm SDD both included 1 mm Al +0.1 mm Cu additional filtration. The main effect analysis identified situations in which image quality and radiation dose increased or decreased, except for kVp which showed peak image quality when exposure factors were increased. A set of minimum mAs values for producing diagnostic image quality were identified. Increasing SDD, unlike the other exposure factors, showed no trends for producing non-diagnostic images. CONCLUSION: The factorial design provided an opportunity to identify suitable acquisition factors. This study provided a method for investigating the combined effect of multiple acquisition parameters on image quality and radiation dose for children.

Impact of body part thickness on AP pelvis radiographic image quality and effective dose.

INTRODUCTION: Within medical imaging variations in patient size can generate challenges, especially when selecting appropriate acquisition parameters. This experiment sought to evaluate the impact of increasing body part thickness on image quality (IQ) and effective dose (E) and identify optimum exposure parameters. METHODS: An anthropomorphic pelvis phantom was imaged with additional layers (1-15 cm) of animal fat as a proxy for increasing body thickness. Acquisitions used the automatic exposure control (AEC), 100 cm source to image distance (SID) and a range of tube potentials (70-110 kVp). IQ was evaluated physically and perceptually. E was estimated using PCXMC software. RESULTS: For all tube potentials, signal to noise ratio (SNR) and contrast to noise ratio (CNR) deceased as body part thickness increased. 70 kVp produced the highest SNR (46.6-22.6); CNR (42.8-17.6). Visual grading showed that the highest IQ scores were achieved using 70 and 75 kVp. As thickness increases, E increased exponentially (r = 0.96; p < 0.001). Correlations were found between visual and physical IQ (SNR r = 0.97, p < 0.001; CNR r = 0.98, p < 0.001). CONCLUSION: To achieve an optimal IQ across the range of thicknesses, lower kVp settings were most effective. This is at variance with professional practice as there is a tendency for radiographers to increase kVp as thickness increases. Dose reductions were experienced at higher kVp settings and are a valid method for optimisation when imaging larger patients.

Optimum Positioning for Anteroposterior Pelvis Radiography: A Literature Review.

AIM: Pelvic radiography is used for the identification of hip joint changes, including pathologies such as osteoarthritis. Several studies have recommended that the position for this radiological procedure should be standing, not supine, to reflect the functional appearances of the hip joint. The aim of this review was to evaluate pelvis radiography positioning with respect to the image appearances and information provided for clinical decision-making. Aside from this, potential recommendations to the radiographic technique for an erect pelvis projection will be considered. METHOD: A literature search was performed using databases/abstract systems (ScienceDirect, Web of Science, PubMed, and MEDLINE). Only articles written in English were included. RESULTS: Twenty-five articles were identified. Findings from the review describe the effect of repositioning from supine to erect on a series of specific hip measurements. These include pelvic tilt, joint space width, and the acetabular component. CONCLUSION: Evidence within the literature illustrates that in several studies, there were differences when repositioning from supine to standing for a number of pelvic metrics. Standing positioning is promoted by some authors since this may facilitate the early diagnosis of hip joint pathology and assist in the planning of surgical interventions. Literature is very limited on how to optimally perform erect pelvis radiography, and this should be an area for future research.

PROPOSAL FOR STANDARDIZATION OF RADIOGRAPHIC STUDIES ON THE HIP AND PELVIS.

Diagnoses of hip and pelvis disorders are based on the detailed medical history, physical examination and laboratory tests, as appropriate for each condition. Plain radiography is still the initial examination of choice and, because of its importance, there is a need to standardize radiographic studies, both in relation to execution and in radiographic series, according to the different pathological conditions. The aim of this paper was to propose standardization for the main radiographic views of the hip and pelvis, and with regard to performing specific series for different pathological conditions, and to provide technical guidance for achieving these aims.

Central Lucency of Pelvic Phleboliths: Comparison of Plain Radiographs and Noncontrast Helical CT

PURPOSE: Central lucency of pelvic phleboliths is frequently observed on plain pelvic radiographs. When it is also present on noncontrast helical CT images, pelvic phleboliths may be easily diagnosed, with no suspicion of distal ureteral calculi. The objective of this study was to determine the frequency with which this phenome-non is seen on plain radiographs and noncontrast helical CT images. MATERIALS AND METHODS: During a recent two-year period we identified 70 patients with renal colic who under-went both abdomino-pelvic radiography and noncontrast helical CT scanning. Radiographs were obtained at 70 -85 kVp and 30 -40 mA; CT scans were preformed within one month of plain radiography with parameters of 120 kVp, 200 -220 mA, 5-mm collimation, and pitch of 1 -1.6, and using soft tissue and bone window settings. With regared to the central lucency of pelvic phleboliths, as seen on both on radiographs and CT im-ages, two experienced radiologists reached a consensus. RESULTS: Among the 70 patients, a total of 150 pelvic phleboliths was found. In all cases except one, pelvic radi-ography and noncontrast helical CT revealed the same number of phleboliths. The exception was a case in which one of two phleboliths demonstrated by CT was not seen on radiographs. Pelvic radiography revealed central lucency in 95 of these 150 phleboliths (63%), but noncontrast helical CT failed to depict a hypodense center in any phlebolith. CONCLUSION: Central lucency of pelvic phleboliths, as frequently seen on plain pelvic radiographs, was not revealed by routine noncontrast helical CT in any patient.The presence or absence of central lucency on these CT images cannot, therefore, be used to differentiate phleboliths from distal ureteral calculi.