Dogan Bor

REFERENCE LEVELS AT EUROPEAN LEVEL FOR CARDIAC INTERVENTIONAL PROCEDURES

In interventional cardiology, a wide variation in patient dose for the same type of procedure has been recognised by different studies. Variation is almost due to procedure complexity, equipment performance, procedure protocol and operator skill. The SENTINEL consortium has performed a survey in nine european centres collecting information on near 2000 procedures, and a new set of reference levels (RLs) for coronary angiography and angioplasty and diagnostic electrophysiology has been assessed for air kerma-area product: 45, 85 and 35 Gy cm2, effective dose: 8, 15 and 6 mSv, cumulative dose at interventional reference point: 650 and 1500 mGy, fluoroscopy time: 6.5, 15.5 and 21 min and cine frames: 700 and 1000 images, respectively. Because equipment performance and set-up are the factors contributing to patient dose variability, entrance surface air kerma for fluoroscopy, 13 mGy min(-1), and image acquisition, 0.10 mGy per frame, have also been proposed in the set of RLs.

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 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.

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.

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.

Variations of Patient Doses in Interventional Examinations at Different Angiographic Units

PurposeWe analyzed doses for various angiographic procedures using different X-ray systems in order to assess dose variations.MethodsDose-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.ResultsIn 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.ConclusionsInterventional 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.

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 (ESDTO) (n = 23) and from the use of thermoluminescent dosimetry (ESDTLD) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESDTO by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESDTO and ESDTLD were correlated using linear regression analysis. Results The mean ESDTO for the chest and abdomen were 67 µGy and 65 µGy per procedure, respectively. The mean ESDTLD per radiograph was 70 µGy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 µGy) per radiograph. Mean effective doses were 16 and 27 µSv per procedure for the chest and abdomen, respectively. ESDTLD was well correlated with ESDTO obtained from the total chest and abdomen radiographs for each infant (R2 = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 × 10-6 to 2 × 10-6 and 0.6 × 10-6 to 2.9 × 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.

Spectral interference corrections for the measurement of 238U in materials rich in thorium by a high resolution γ-ray spectrometry

In this study, the spectral interferences are investigated for the analytical peaks at 63.3 keV of (234)Th and 1001.0 keV of (234m)Pa, which are often used in the measurement of (238)U activity by the gamma-ray spectrometry. The correction methods are suggested to estimate the net peak areas of the gamma-rays overlapping the analytical peaks, due to the contribution of (232)Th that may not be negligible in materials rich in natural thorium. The activity results for the certified reference materials (CRMs) containing U and Th were measured with a well type Ge detector. The self-absorption and true coincidence-summing (TCS) effects were also taken into account in the measurements. It is found that ignoring the contributions of the interference gamma-rays of (232)Th and (235)U to the mixed peak at 63.3 keV of (234)Th ((238)U) leads to the remarkably large systematic influence of 0.8-122% in the measured (238)U activity, but in case of ignoring the contribution of (232)Th via the interference gamma-ray at 1000.7 keV of (228)Ac to the mixed peak at 1001 keV of (234m)Pa ((238)U) results in relatively smaller systematic influence of 0.05-3%, depending on thorium contents in the samples. The present results showed that the necessary correction for the spectral interferences besides self-absorption and TCS effects is also very important to obtain more accurate (238)U activity results. Additionally, if one ignores the contribution of (232)Th to both (238)U and (40)K activities in materials, the maximum systematic influence on the effective radiation dose is estimated to be ~6% and ~1% via the analytical peaks at 63.3 and 1001 keV for measurement of the (238)U activity, respectively.

Methods for spectral interference corrections for direct measurements of 234U and 230Th in materials by gamma-ray spectrometry

When the high-resolution gamma-ray spectrometry was used in the analysis of (234)U and (230)Th in samples, there is a much more need to correct for the measured activity results of (234)U and (230)Th mainly due to self-absorption effects and the interfering lines from (226)Ra, (235)U, (238)U and their decay products that often might be present in the samples. Therefore, in the present study, the methods for the spectral interference corrections for the analytical peaks of (234)U and (230)Th are suggested to take into account the contributions of the overlapping gamma rays to these peaks. For the method validation, direct gamma-ray spectrometric measurements were carried out using certified reference materials (CRM) by use of a 76.5 % n-type Ge detector. The activities measured for the CRM samples were corrected for spectral interferences, self-absorption and true coincidence-summing (TCS) effects. The obtained results indicate that ignoring of the contribution of the interference gamma rays to the main analytical peak at 53.2 keV of (234)U leads to a lager systematic error of 87.3-90.4 % for the measured activities of (234)U, and similarly if one ignores the contributions of the interference gamma rays to the main analytical peak at 67.7 keV of (230)Th, this leads to a much smaller systematic error of 2.1-2.7 % for the activities of (230)Th. Therefore, the required correction factors for spectral interferences to the analytical peaks of (234)U and (230)Th are not negligible and thus they should also be considered besides necessary self-absorption factors to determine more accurate activities in the samples. On the other hand, it is estimated that although the TCS effects on the main analytical peaks of both (234)U and (230)Th are negligibly small, those TCS correction factors for their interference gamma rays to these peaks should be taken into account when direct measurements are performed in a close-counting geometry condition. Otherwise, the resulted activities can have serious erroneous results for both (234)U and (230)Th while using gamma-ray spectrometry, thereby leading to inaccuracies in their derived quantities, for instance, the corresponding age determinations of the samples.

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).