Assessment of radiation doses to cardiologists during interventional examinations.

The accuracy of two on line dosimetric techniques was investigated for the estimation of cardiologist doses. The first technique involves the establishment of a database relating the cardiologist extremity doses to patient DAP values. Doses of nine cardiologists were measured together with patient doses during the interventional cardiac examinations of 166 patients for this purpose. Data were collected from five cardiology departments. The mean of the eye, thyroid, waist, right-left wrist, and right-left leg doses per procedure were measured as 72.4 (31.6-107.1), 68.5 (13.3-174.6), 11.2 (0.9-28.4), 67.8 (21.9-120.3) to 216 (52.7-425.4), and 137 (51.4-386.2) to 384 (135-1168.3) microGy/procedure. The effective doses were calculated according to the use of protection tools and a mean value of 12.14 (1.2-30.2) microSv/procedure was found. The ratios of staff dose to patient DAP were found to be within the range of 0.14-3.75 for each procedure. In the second method, cardiologist doses were calculated and compared with the measured values. Scatter doses were measured at the positions of cardiologists from Rando phantom exposures using similar conditions with patient procedures for this purpose. The parameters obtained from these exposures and patient examinations were used to calculate the doses to cardiologists.

ESTABLISHMENT OF RADIATION DOSES FOR PEDIATRIC X-RAY EXAMINATIONS IN A LARGE PEDIATRIC HOSPITAL IN TURKEY.

Pediatric patients are more sensitive to ionizing radiation when compared with adults. The aim of this study was to evaluate the radiation doses for some common pediatric x-ray examinations performed with various digital radiography systems. Quality control tests of the digital radiography systems were carried out according to international published protocols before the pediatric dose measurements. Radiation dose measurement was performed by using the x-ray tube outputs and thermoluminescent dosimeter dose measurement methods. In the present study, radiation doses were assessed for 247 chest, 230 pelvis, 194 skull and 73 abdomen x-ray examinations and in total 744 pediatric patients doses were measured. Pediatric patients were classified into four age groups 0-1, 1-5, 5-10 and 10-15 years as given by European Commission guidance. Effective doses were determined for each examination using a PCXMC 2.0 Monte Carlo program. The mean measured entrance skin doses for the age interval 1-5 years and AP projection by using tube output measurement methods were 149 µGy for chest, 304 µGy for pelvis, 387 µGy for skull and 199 µGy for abdomen examinations. The radiation dose results obtained in this study were in the range of the published results in the literature.

Comparison of effective doses obtained from dose-area product and air kerma measurements in interventional radiology.

In this study, measurements of dose-area product (DAP) and entrance dose were carried out simultaneously in a sample of 162 adult patients who underwent different interventional examinations. Effective doses for each measurement technique were estimated using the conversion factors that have been determined for specific X-ray views in a mathematical phantom. Exposure conditions used in clinical practice never match these theoretical models exactly, and deviations from the assumed standard conditions cause uncertainties in effective dose estimations. Higher effective dose values are found if the air kerma results are used rather than DAP readings, both for patient and Rando phantom studies. Comparison of DAP, fluoroscopy times and skin doses were made with published data. DAP measurement for the effective dose calculation and thermoluminescent dosimeter for the skin dose estimates are found to be the most reliable methods for patient dosimetry.

Performance evaluation of soft copy display systems according to AAPM TG18 protocol.

The purpose of this study was to evaluate the display performance of the liquid crystal display monitors according to the American association of physicists in medicine task group 18 (AAPM TG18) protocol at prior and after new calibration. We measured minimum and maximum luminance, luminance ratio, luminance and contrast response, luminance angular and spatial dependency, resolution, veiling glare and chromaticity quantitatively for 33 medical displays. Display noise was evaluated only visually. The mean maximum luminance and luminance ratio were 386 and 273 cd m(-2), respectively. The mean deviation of measured luminance and contrast response from expected response associated with the digital imaging and communications in medicine (DICOM) grayscale standard display function (GSDF) were 9.76 and 2.35 % at prior calibration and 1.23 and 0.26 % after recalibration, respectively. In luminance uniformity test the mean maximum luminance deviation was 16 %. Luminance method was used in the spatial resolution test and the mean percent luminance difference was 12 % at the center. The mean glare ratio was 1 154. The average color uniformity parameter across the display area of each display device was 0.0093. Majority of the test results were in good agreement with the criteria recommended by AAPM TG18 report. Considerable improvement was observed in display luminance and contrast response with respect to expected response of DICOM GSDF after new calibration for some displays.

Quantitative image quality measurements of a digital breast tomosynthesis system.

PURPOSE: The aim of this study was to measure the image quality of a digital breast tomosynthesis (DBT) system quantitatively. MATERIALS AND METHODS: The signal transfer property (STP), modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the Hologic Selenia Dimensions breast tomosynthesis system were measured according to established methods. The NPS was calculated from two-dimensional (2 D) fast Fourier transform (FFT) of flat field images. The presampling MTF of the system was determined for 2 D standard projection mammography and 3 D breast tomosynthesis mode using the edge method. The DQE was derived for different detector air kerma (DAK) values from NPS and MTF measurements. RESULTS: The detector response function was linear for both two-dimensional (2 D) standard projection mammography and three-dimensional (3 D) breast tomosynthesis modes. The gradient of the detector response in the 3 D imaging mode was higher than the gradient in the 2 D imaging mode by a factor of 3.1. The MTF values measured at the Nyquist frequency were 32 % and 39 % in 2 D and 3 D imaging modes, respectively. The DQE was saturated at an air kerma value approximately 3.5 times lower in 3 D mode than in 2 D mode. The measured maximum DQE value was 54 %. CONCLUSION: The measured DQE values were comparable with breast tomosynthesis systems from other companies (Siemens, GE).

Average glandular dose in digital mammography and breast tomosynthesis.

PURPOSE: To determine the average glandular dose (AGD) in digital full-field mammography (2 D imaging mode) and in breast tomosynthesis (3 D imaging mode). MATERIALS AND METHODS: Using the method described by Boone, the AGD was calculated from the exposure parameters of 2247 conventional 2 D mammograms and 984 mammograms in 3 D imaging mode of 641 patients examined with the digital mammographic system Hologic Selenia Dimensions. The breast glandular tissue content was estimated by the Hologic R2 Quantra automated volumetric breast density measurement tool for each patient from right craniocaudal (RCC) and left craniocaudal (LCC) images in 2 D imaging mode. RESULTS: The mean compressed breast thickness (CBT) was 52.7 mm for craniocaudal (CC) and 56.0 mm for mediolateral oblique (MLO) views. The mean percentage of breast glandular tissue content was 18.0% and 17.4% for RCC and LCC projections, respectively. The mean AGD values in 2 D imaging mode per exposure for the standard breast were 1.57 mGy and 1.66 mGy, while the mean AGD values after correction for real breast composition were 1.82 mGy and 1.94 mGy for CC and MLO views, respectively. The mean AGD values in 3 D imaging mode per exposure for the standard breast were 2.19 mGy and 2.29 mGy, while the mean AGD values after correction for the real breast composition were 2.53 mGy and 2.63 mGy for CC and MLO views, respectively. No significant relationship was found between the AGD and CBT in 2 D imaging mode and a good correlation coefficient of 0.98 in 3 D imaging mode. CONCLUSION: In this study the mean calculated AGD per exposure in 3 D imaging mode was on average 34% higher than for 2 D imaging mode for patients examined with the same CBT.

Patient and staff doses for some complex x-ray examinations.

The aim of this study was to measure patient and staff doses simultaneously for some complex x-ray examinations. Measurements of dose-area product (DAP) and entrance skin dose (ESD) were carried out in a sample of 107 adult patients who underwent different x-ray examinations such as double contrast barium enema (DCBE), single contrast barium enema (SCBE), barium swallow, endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic cholangiography (PTC), and various orthopaedic surgical procedures. Dose measurements were made separately for each projection, and DAP, thermoluminescent dosimetry (TLD), film dosimetry and tube output measurement techniques were used. Staff doses were measured simultaneously with patient doses for these examinations, with the exception of barium procedures. The measured mean DAP values were found to be 8.33, 90.24, 79.96 Gy cm(2) for barium swallow, SCBE and DCBE procedures with the fluoroscopy times of 3.1, 4.43 and 5.86 min, respectively. The calculated mean DAP was 26.33 Gy cm(2) for diagnostic and 89.76 Gy cm(2) therapeutic ERCP examinations with the average fluoroscopy times of 1.9 and 5.06 min respectively. Similarly, the calculated mean DAP was 97.53 Gy cm(2) with a corresponding fluoroscopy time of 6.1 min for PTC studies. The calculated mean entrance skin dose (ESD) was 172 mGy for the orthopaedic surgical studies. Maximum skin doses were measured as 324, 891, 1218, 750, 819 and 1397 mGy for barium swallow, SCBE, DCBE, ERCP, PTC and orthopaedic surgical procedures, respectively. The high number of radiographs taken during barium enema examinations, and the high x-ray outputs of the fluoroscopic units used in ERCP, were the main reasons for high doses, and some corrective actions were immediately taken.

Radiation doses of patients and urologists during percutaneous nephrolithotomy.

Renal stones can be treated either by extracorporeal shock wave lithotripsy (ESWL) or percutaneous nephrolithotomy (PCNL). Increasing use of fluoroscopic exposure for access and to detect stone location during PCNL make the measurement of patient and staff doses important. The main objective of this work was to assess patient and urologist doses for the PCNL examination. We used the tube output technique for determination of patient doses (n = 20) and lithium fluoride thermoluminescent dosimeter (TLD) chips for urologist dose measurements. The TLD technique was also used for some patient dose measurements (n = 7) for comparison with the tube output technique. Mean entrance skin doses of 191 and 117 mGy were measured by the tube output technique for anterior-posterior (AP) and right anterior oblique (RAO) 30 degrees /left anterior oblique (LAO) 30 degrees projections, respectively. The mean urologist doses for eye, finger and collar were measured as 26, 33.5 and 48 microGy per procedure, respectively. The mean effective dose per procedure for the urologist was 12.7 microSv. None of the individual skin dose results approach deterministic levels.