[OA100] Skin and organ doses in pediatric interventional cardiology procedures

Abstracts / Physica Medica 52 (2018) 1–98

ing and optimizing the radiation dose imparted to patients undergoing this procedure. Materials and Methods. A first survey was carried out in our radiology department, collecting data from 31 subjects during HSG, carried out using digital equipment (model Opera, Housing GMM, Italy, with over-couch tube, CsI flat panel detector Thales, model Pixium RAD 4343 with pixel size 148 lm, Automatic Exposure Control). Data showed a wide variability, with the mean DAP (Dose Area Product) being higher than those reported by other authors[1] from other departments, suggesting need for optimization. After intervention (consisting in reducing the field size, the fluoroscopy time and the number of radiographs) a new group of 53 subjects was monitored, showing significant DAP reduction. ESAKs (Entrance Surface Air Kerma – free in air) – calculated by using normalized radiation output (previously assessed during quality controls), current*time product (recorded during HSG) and source-skin distance – were converted to dose to ovaries by using appropriate coefficients. Also ED (effective dose) was evaluated. Results. Mean DAP decreased from 3348 to 634 mGy*cm2. The 75th percentile of the DAP distribution, 800 mGy*cm2, was adopted as Institutional Diagnostic Reference Level. Mean estimated dose to ovaries was about 0.8 mGy and mean effective dose was about 0.3 mSv. Conclusions. Periodic review of the procedures, in light of both technological advances and clinical requests, is necessary in order to improve clinical practice with guaranteed patient safety.

Reference

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nescent dosemeters for a sample of 50 children, 7 diagnostic (DP) and 43 therapeutic procedures (TP). Finally, breasts, lungs, esophagus and thyroid doses were estimated based on DAP-to-organ doses conversion factors available in literature. Results. The study included 263 patients divided into 4 groups according to weight: < 5 kg with 5 DP and 31 TP, 5–<15 kg with 40 DP and 72 TP, 15–<30 kg with 19 DP and 67 TP and 30–<55 kg with 4 DP and 25 TP. For DP, median DAP and CD values for the four groups were 0.5, 2, 4 and 20 Gy.cm2 and 6, 28, 36 and 165 mGy respectively. Those were 1, 2, 4 and 10 Gy.cm2 and 10, 36, 41 and 75 mGy for TP correspondingly. The mean measured PSD was 15 (1–30) and 94 (1–491) mGy for DP and TP respectively. The mean breasts, lungs, esophagus and thyroid doses for neonate (respectively infant) were 2.1, 2.8, 3.1 and 2.3 mGy (8, 12, 9 and 6 mGy) respectively for DP and 3.9, 5, 6 and 4 mGy (23, 34, 26 and 18 mGy) respectively for TP. Conclusions. Exposures parameters and measured PSD values were very low excluding the risk of skin injuries. The lungs and esophagus involved highest estimated organ doses for both neonate and infant. For patients requiring repeated procedures, accumulated doses will increase the cancer risk in specific organ. https://doi.org/10.1016/j.ejmp.2018.06.172

[OA101] Assessment of dose efficiency of a modern X-ray fluoroscopy system using a model observer Henrik Elgström a, Erik Tesselaar b, Michael Sandborg c,* a

[1] Hart D, Hillier MC, Shrimpton PC. Doses to patients from radiographic and fluoroscopic X-ray imaging procedures in the UK – 2010 review. HPA-CRCE-034 2012. https://doi.org/10.1016/j.ejmp.2018.06.171

[OA100] Skin and organ doses in pediatric interventional cardiology procedures Chadia Rizk a,*, Georges Fares b, Filip Vanhavere c, Zakhia Saliba d, Jad Farah e a National Council for Scientific Research, Lebanese Atomic Energy Commission, Saint Joseph University, Faculty of Sciences, Department of Radiation Safety Services, Beirut, Lebanon b Saint Joseph University, Faculty of Sciences, Department of Physics, Beirut, Lebanon c Belgium Nuclear Research Center (Sck-Cen), Department of Radiation Protection Dosimetry and Calibration, Mol, Belgium d Hotel Dieu de France Hospital, Department of Pediatrics, Beirut, Lebanon e Paris-Sud University Hospitals, Department of Radiology and Nuclear Medicine, Le Kremlin-Bicêtre, France ⇑ Corresponding author.

Purpose. Recent reports on radiation accidents and injuries in interventional cardiology (IC) raised the issue of radiation protection, especially for pediatric patients. This work hence focused on the measurement of skin dose in diagnostic and therapeutic pediatric IC procedures and the estimation of organ doses. Methods. Exposures parameters including Dose Area Product (DAP), Cumulative Dose (CD), etc. were retrospectively reviewed for 263 patients undergoing diagnostic or therapeutic IC procedures for a congenital heart disease. These were all taken from a large pediatric hospital responsible for approximately 50% of all pediatric IC activity in the country. Patient age and weight were also collected. Additionally, Peak Skin Dose (PSD) was measured using thermolumi-

Medical Physics, Stockholm University, Stockholm, Sweden Medical Physics, Clinical and Experimental Medicine, Medical Physics, Linköping, Sweden c Medical Physics, Medical and Health Sciences, Center for Medical Image Science and Visualization, Linköping, Sweden ⇑ Corresponding author. b

Purpose. The aim of this work was to measure image quality in terms of the square of the accumulation rate of the signal to noise ratio of low-contrast details, SNR2rate , kerma area product rate, PKA ;rate and to quantify dose efficiency, SNR2rate /PKA ;rate on a modern fluoroscopy system while varying the imaging conditions such as contrast detail size, X-ray beam size, dose rate, and object thickness. Methods. The methodology derived by Tapiovaara et al. (Phys. Med. Biol., 38, 1761–1788, 1993, and STUK-A196, 2003) was used and implemented in MatlabTM. Measurement of model observer SNR2rate and PKA ;rate were derived from stored fluoroscopy image sequences and the built-in kerma-area product reading on a Siemens Axiom Artis Zee MP system, respectively. 1024 image frames with and without the contrast detail were stored and subsequently analyzed by a model observer. SNR was calculated from the mean and standard deviation of the distributions of the decision variable. Finally, the long-term stability of the imaging system in terms of dose efficiency and the usefulness of the method as a quality control measure was evaluated. Results. The precision in SNR2rate estimate was proportional to the inverse square root of the number of frames and SNR2rate was proportional to the area and squared thickness of the low-contrast detail. The dose efficiency increased with a factor of three with decreasing X-ray beam size from 242 cm2 to 182 cm2 and object thickness from 25 cm to 20 cm, hence quantifying the large dose efficiency gains by collimation and compression. The dose efficiency increased by 50% using the reduced dose rate compared to high dose rate. While the long-term stability of dose efficiency was measured with an uncertainty of 8%, the method is presently too time-consuming for routine quality control, mainly due to the slow data transfer of the large data files to the analysis server. Conclusions. The results of the dose efficiency measurements under varying imaging conditions, agree with common radiological protec-