Investigation of grid performance using simple image quality tests.

Antiscatter grids improve the X-ray image contrast at a cost of patient radiation doses. The choice of appropriate grid or its removal requires a good knowledge of grid characteristics, especially for pediatric digital imaging. The aim of this work is to understand the relation between grid performance parameters and some numerical image quality metrics for digital radiological examinations. The grid parameters such as bucky factor (BF), selectivity (Σ), Contrast improvement factor (CIF), and signal-to-noise improvement factor (SIF) were determined following the measurements of primary, scatter, and total radiations with a digital fluoroscopic system for the thicknesses of 5, 10, 15, 20, and 25 cm polymethyl methacrylate blocks at the tube voltages of 70, 90, and 120 kVp. Image contrast for low- and high-contrast objects and high-contrast spatial resolution were measured with simple phantoms using the same scatter thicknesses and tube voltages. BF and SIF values were also calculated from the images obtained with and without grids. The correlation coefficients between BF values obtained using two approaches (grid parameters and image quality metrics) were in good agreement. Proposed approach provides a quick and practical way of estimating grid performance for different digital fluoroscopic examinations.

Performance tests for mammographic film-screen combinations: use of absolute techniques.

PURPOSE: A performance comparison of film-screen combination used in mammography was conducted using conventional and new techniques. MATERIALS AND METHODS: The performance of 30 mammographic film-screen combinations was evaluated by sensitometry, and the total performance was determined using phantom measurements. Quantum detection and light emission efficiency of the screens were also measured as an alternative technique for determining screen speeds. These efficiency measurements provided quantitative results for selecting the optimum beam quality. RESULTS: Considering the image quality scores from three observers and the radiation doses obtained from the speed measurements, eight combinations were selected as being optimal. Only three of the mammographic film screen combinations in this group were the recommendations of manufacturers. CONCLUSION: The total performance phantom can be effectively used for the qualitative check of image and provide speed information for mammographic film-screen combinations comparable to sensitometric techniques.

Accuracy of clinical protocols in SPECT.

UNLABELLED: The accuracy of clinical SPECT is highly dependent on the acquisition and processing parameters, which are selected according to the clinical task. These parameters are usually set within protocols in order to allow for standardization from one study to another and to speed up the clinical routine. METHODS: In the first part of this work, tomographic images of a Jaszczak phantom were obtained on 5 different SPECT systems using 2 common clinical protocols and each system's default acquisition and processing parameters. In the second part, tomographic images of the Jaszczak phantom were obtained using identical acquisition and processing parameters on all systems. Projection data were then transferred to other system software for reconstruction. RESULTS: For the first part of the work, variation in image quality was seen quantitatively among the systems, even when clinical protocols with the same aim were used. The accuracy of the similar reconstruction algorithms and data transfer was determined and summarized. In the second part of this study, the performance of the SPECT systems using similar acquisition protocols and reconstruction software was determined and summarized. CONCLUSION: The default clinical protocols offered by the manufacturer for similar studies may be different from one another. The user should modify these protocols using phantom studies and standardize same-purpose protocols among different software programs.

Patient doses and dosimetric evaluations in interventional cardiology.

Interventional cardiological examinations may be associated with excessive radiation exposures which may cause skin injuries and higher probabilities of stochastic effects. Dose-area product (DAP) and skin doses of 325 patients were measured using alternative dosimetric techniques for different cardiological examinations. Data were collected from five different systems with the involvement of 11 cardiologists. All these dosimetric information has been collected separately for each of 10 projections together with the exposure parameters of X-ray systems. Mean DAP values measured with a transparent ion chamber were 49.1 Gy cm(2), 66.8 Gy cm(2), 106.9 Gy cm(2) and 124.7 Gy cm(2), respectively, for coronary angiography (CA), percutaneous transluminal coronary angioplasty (PTCA) or stent (PT-SI), coronary angiography and/or PTCA and/or stent (CA-PT-SI), and ablation examinations. Radiochromic films, thermoluminescent dosimeters (TLD) and point measurement of air kerma (AK) were carried out for skin dose assessments. Skin doses of 23 patients measured with radiochromic films were found to be between 2 Gy and 6 Gy. Although the complexity of the procedures was the major reason for these excessive doses, considerable contributions of high X-ray output of some fluoroscopy units were also noticed. In addition to the direct measurement of DAP, alternative DAP values were also determined from the skin dose measurement techniques; exposed areas were summed on digitized radiochromic films in one technique, The product of AK reading with X-ray field size measured at the patient entrance using slow X-ray films was taken as another DAP. Good correlations were found among the DAP results and also between the entrance skin doses calculated from AK measurements and direct DAP readings (R(2)=0.91). A trigger DAP value of 130 Gy cm(2) for the 2 Gy of skin doses was derived from this relationship. Collection of dosimetric data for each projection was also investigated regarding a possible standardization of clinical techniques; in the case of coronary angiography examinations LAO 45 and RAO 30 were found as the dominant projections which may also simplify the dosimetric technique.

Radiation exposure to premature infants in a neonatal intensive care unit in Turkey.

OBJECTIVE: The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room. MATERIALS AND METHODS: We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESD(TO)) (n = 23) and from the use of thermoluminescent dosimetry (ESD(TLD)) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESD(TO) by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESD(TO) and ESD(TLD) were correlated using linear regression analysis. RESULTS: The mean ESD(TO) for the chest and abdomen were 67 microGy and 65 microGy per procedure, respectively. The mean ESD(TLD) per radiograph was 70 microGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 nGy) [DOSAGE ERROR CORRECTED]per radiograph. Mean effective doses were 16 and 27 microSv per procedure for the chest and abdomen, respectively. ESD(TLD) was well correlated with ESD(TO) obtained from the total chest and abdomen radiographs for each infant (R(2) = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 x 10(-6) to 2 x 10(-6) and 0.6 x 10(-6) to 2.9 x 10(-6) for chest and abdomen radiographs, respectively. CONCLUSION: The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other.

Variations in breast doses for an automatic mammography unit.

PURPOSE: To assess variations of glandular doses for a group of patients when different dose modes are selected for a specific system. MATERIALS AND METHODS: All measurements were obtained with a Senographe DMR mammography unit (GE Medical Systems). Automatic exposure control with either contrast or standard mode was routinely used in patient examinations. Entrance surface air kerma (ESAK) values were estimated from the postexposure mAs and from the recorded data. Subsequently the mean glandular dose (MGD) for each view was calculated using the conversion factors assuming 50% glandular and 50% adipose tissue composition. RESULTS: The average MGD for the right craniocaudal view for all beam qualities was 1.65 mGy, and 46.7 mm was the average compressed breast thickness for this view. Average MGDs were 1.61, 1.76, and 1.35 mGy for Mo-Mo, Mo-Rh, and Rh-Rh anode filter selections, respectively. Conversely, 2.18 and 1.47 of breast doses were measured for contrast and standard dose modes at the most often used (Mo-Mo) anode filter selection. CONCLUSION: Breast dose measurement techniques with the standard phantom or on real patients are easy to implement for the mammography users. Obtaining ESAK versus breast thickness relationship is useful for retrospective dose evaluation; better correlation can be established (67% vs. 52%) if they are generated separately for each dose modes.

Performance measurements of mammographic systems.

Performance measurements of 30 mammographic installations were carried out in order to see the current level of image quality and breast doses.The half of the systems tested in this survey indicated automatic exposure control and beam collimation problems. Film processing and dark room conditions were not optimum for the majority of the installations. Image quality phantoms were exposed by the user and team of the survey at each visited center. Lower breast doses were obtained at equal image qualities for the radiographs of the team indicating the importance of adequate handling of some exposure parameters. Corrective actions were suggested to each installation and necessary guidance was advised for the implementation of routine quality control activities.

Investigation of mean glandular dose versus compressed breast thickness relationship for mammography.

The relationship between the mean glandular dose (MGD) and the compressed breast thickness (CBT) is commonly used for the presentation of mammographic dose survey results and could also be useful for the assessment of individual breast doses retrospectively in case of lack of necessary dosimetric instrumentation. The high data scattering from the best fit reduces the reliability of this technique. The aim of this study was to investigate the accuracy of this relationship using the data collected from a patient survey and phantom experiment. Patients were divided into three different groups according to their breast glandularities, which were predicted from the inspection of previous mammograms. X-ray beam qualities that will be used in patient examinations were determined according to breast thickness and predicted glandularities. The MGD versus CBT relationship for all the examined patients resulted in a poor correlation (R2 = 0.28). This relationship was separately obtained for each glandularity group and also for sub-groups of specific beam qualities. The best correlation (R(2) = 0.73) was obtained for the fatty breast group and Mo/Mo combination. A low correlation (R2 = 0.34) was observed in the mid-glandularity group due to inclusion of a wide range of glandularities in this group. In the case of the dense breast group, although the glandularity range was narrow, there were e still high data scattering (R2 = 0.25). This was probably due to the use of Mo/Rh and Mo/Mo combinations. This is validated by obtaining the MGD-CBT relationship specific to Mo/Mo combination (R2 = 0.61).

Effects of radiologists' skill and experience on patient doses in interventional examinations.

In this study, effects of radiologists' skill and experience on patient doses were investigated. Dose-area product and entrance surface doses of two groups of patients, one examined by a number of junior radiologists and another one by a senior radiologist, have been compared for the diagnostic interventional examinations of cerebral and lower limbs. Collimation of the X-ray beam and shortening the fluoroscopy times by the senior radiologist considerably reduced the patient doses for interventional cerebral examinations.

Variations of patient doses in interventional examinations at different angiographic units.

PURPOSE: We analyzed doses for various angiographic procedures using different X-ray systems in order to assess dose variations. METHODS: Dose-area product (DAP), skin doses from thermoluminescent dosimeters and air kerma measurements of 308 patients (239 diagnostic and 69 interventional) were assessed for five different angiographic units. All fluoroscopic and radiographic exposure parameters were recorded online for single and multiprojection studies. Radiation outputs of each X-ray system were also measured for all the modes of exposure using standard protocols for such measurements. RESULTS: In general, the complexity of the angiographic procedure was found to be the most important reason for high radiation doses. Skill of the radiologist, management of the exposure parameters and calibration of the system are the other factors to be considered. Lateral cerebral interventional studies carry the highest risk for deterministic effects on the lens of the eye. Effective doses were calculated from DAP measurements and maximum fatal cancer risk factors were found for carotid studies. CONCLUSIONS: Interventional radiologists should measure patient doses for their examinations. If there is a lack of necessary instrumentation for this purpose, then published dose reports should be used in order to predict the dose levels from some of the exposure parameters. Patient dose information should include not only the measured quantity but also the measured radiation output of the X-ray unit and exposure parameters used during radiographic and fluoroscopic exposures.