Radiation Dose to the Pediatric Cardiac Catheterization and Intervention Patient

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1 Medical Physics and Informatics Original Research Chida et al. Radiation Dose to Pediatric Patients Medical Physics and Informatics Original Research Downloaded from by on 1/12/18 from IP address Copyright ARRS. For personal use only; all rights reserved Koichi Chida 1 Tadayuki Ohno 2 Shuhei Kakizaki 2 Mika Takegawa 1 Hiroko Yuuki 1 Mitsuru Nakada 3 Shoki Takahashi 3 Masayuki Zuguchi 1 Chida K, Ohno T, Kakizaki S, et al. Keywords: cardiac catheterization, children, fluoroscopy, interventional radiology, radiation dose DOI:1.2214/AJR Received February 8, 21; accepted after revision April 5, 21. This work was supported, in part, by a grant-in-aid from Miyata Cardiac Research Promotion Foundation. 1 Department of Radiological Technology, School of Health Sciences, Faculty of Medicine, Tohoku University, 2-1 Seiryo-machi, Aoba-ku, Sendai , Japan. Address correspondence to K. Chida (chida@mail.tains.tohoku.ac.jp). 2 Department of Pediatrics, Tohoku University Graduate School of Medicine, Aoba, Sendai, Japan. 3 Department of Radiology, Tohoku University Graduate School of Medicine, Aoba, Sendai, Japan. AJR 21; 195: X/1/ American Roentgen Ray Society Radiation Dose to the Pediatric Cardiac Catheterization and Intervention Patient OBJECTIVE. The radiation dose from cardiac catheterization is particularly relevant when treating children because of their greater radiosensitivity compared with adults. Moreover, cardiac catheterization is being used increasingly for interventional radiology procedures, possibly resulting in higher patient radiation doses. This article reports the radiation doses and related factors, such as fluoroscopy time, for children who underwent cardiac catheterization and children who underwent other interventional radiology procedures. MATERIALS AND METHODS. We evaluated 239 consecutive patients who underwent cardiac catheterization (n = 25) or another interventional radiology procedure (n = 34) for which the dose area product (DAP) was measured. The number of cine runs and fluoroscopic time for each procedure and the body mass index and body weight of each patient were recorded. We also used the double product combined with body weight, which is the weight fluoroscopic time product. RESULTS. The average DAP ± SD of cardiac catheterization and of an interventional radiology procedure was 1,72.6 ± 2,11.1 cgy cm 2 and 2,242.2 ± 2,59.4 cgy cm 2, respectively. The average fluoroscopic time ± SD of cardiac catheterization and of an interventional radiology procedure was 24.1 ± 16.8 minutes and 37.2 ± 2. minutes. For children who underwent cardiac catheterization and those who underwent an interventional radiology procedure, a strong correlation was seen between the DAP and weight fluoroscopic time product (cardiac catheterization, r =.96; interventional radiology procedure, r =.885) and a good correlation was detected between the DAP and weight (r =.819 and.895, respectively). CONCLUSION. There was a good correlation between the DAP and weight and between DAP and weight fluoroscopic time product for children who underwent cardiac catheterization or an interventional radiology procedure. Therefore, body weight is important for determining radiation dose to children undergoing cardiac catheterization or an interventional radiology procedure. The normalized DAP (i.e., DAP divided by body weight), fluoroscopy time, and number of cine runs were greater in children who underwent an interventional radiology procedure than in those who underwent cardiac catheterization. Therefore, the radiation dose to children from interventional radiology procedures is a more critical issue. T he radiation dose from cardiac catheterizations are the highest of any commonly performed general x-ray diagnostic examination [1 8]. The radiation dose from cardiac catheterization is particularly relevant when treating children because of their greater radiosensitivity compared with adults and the large fraction of a child s body that is irradiated by the x-ray beam [9 12]. In addition, children with complex congenital heart diseases are often catheterized several times [13], so the risk of somatic radiation effects (i.e., radiation-induced cancer) is greater in children than in adults. Moreover, cardiac catheterization is being used increasingly for interventional radiology procedures, possibly resulting in higher patient radiation doses. The radiation dose from cardiac catheterization (diagnostic) and interventional radiology (therapeutic) procedures should be kept as low as reasonably achievable in pediatric patients. Furthermore, an excellent correlation between the effective dose, which is used to assess the potential risk for stochastic effects, and the dose area product (DAP) from cardiac catheterization and interventional radiology procedures has been reported in pediatric patients [14]. AJR:195, November

2 Chida et al. Downloaded from by on 1/12/18 from IP address Copyright ARRS. For personal use only; all rights reserved TABLE 1: Characteristics of the Pediatric Patients in Our Study Cohort and the Procedures They Underwent This article reports current radiation doses, especially DAP, and related factors such as fluoroscopy time for children who underwent cardiac catheterization or an interventional radiology procedure. In addition, this study calculates the correlation between the DAP and several factors (i.e., fluoroscopy time, number of cine runs) for cardiac catheterization and for an interventional radiology procedure. Materials and Methods This was a retrospective study. We evaluated 239 consecutive patients who underwent cardiac catheterization (n = 25) or another interventional radiology procedure (n = 34) for which the DAP was measured at Tohoku University Hospital. Table 1 summarizes the characteristics of the study subjects and the procedures they underwent. The average patient age ± SD and average body weight ± SD were 4.1 ± 4.6 years and 17.5 ± 16.6 kg, respectively. Cardiac Catheterization and Interventional Radiology Procedures A biplane imaging system (Bicor Plus, Siemens Healthcare) was used. Generally, the procedures were performed using a digital cine x-ray system with an image intensifier at an acquisition rate of 3 frames per second, with pulsed fluoroscopy (15 pulses per second). For patients whose heart rate exceeded 12 beats per minute, an acquisition rate of 6 frames per second and pulsed fluoroscopy rate of 3 pulses per second were applied. In most interventional radiology procedures, such as balloon dilatation, the frame rate is 15 frames per second. The DAP was measured using a transmission chamber fitted to an x-ray tube. Overall Value Cardiac Catheterization Interventional Radiology Procedure Total no. of patients No. of patients by sex (male:female ratio) 131:98 123:82 18:16 Age (y) 4.1 ± ± ± 5.2 Height (cm) 94.7 ± ± ± 4.3 Weight (kg) 17.5 ± ± ± 18.7 Body mass index ± ± ± 4.1 Fluoroscopic time (min) 25.9 ± ± ± 2. No. of cine runs 8.2 ± ± ± 8.1 1,776.2 ± 2, ,72.6 ± 2,11.1 2,242.2 ± 2,59.4 DAP / weight (cgy cm 2 kg 1 ) ± ± ± Note Except the number of patients and number of patients by sex, data are presented as average ± SD. DAP = dose area product. The DAP, number of cine runs, and fluoroscopic time of each procedure and the body mass index (BMI) and body weight of each patient were recorded. We also used the double product combined with body weight, which is the weight fluoroscopic time product. The DAP, number of cine runs, and fluoroscopic time for the biplane system were the total fluoroscopic time and total DAP for both planes (total value = frontal plane value + lateral plane value). The most frequently used x-ray exposure factors in this study were source-to-image-intensifier distances of 9 cm (frontal view) and 95 cm (lateral view), an image intensifier field size of 17 cm, and a tube potential of 7 kvp. An added.1-mmthick copper beam filter was used for fluoroscopy. For cineangiography, an additional.1- or.2-mmthick copper beam filter is used automatically. Statistics The Student s t test was used to compare the two patient groups: children who underwent cardiac catheterization and those who underwent an interventional radiology procedure. Correlations between DAP and the number of cine runs, fluoroscopic time, weight, BMI, and weight fluoroscopic time product were analyzed using linear regression. Statistical significance was defined as a p value of less than.5. Results Cardiac Catheterization (Diagnostic) Table 1 shows the average weight and BMI of the subjects and the average fluoroscopic time, number of cine runs, DAP, and normalized DAP (i.e., DAP divided by body weight [DAP / weight]) for the procedures. Table 2 summarizes the congenital heart diseases and cardiac abnormalities in the study subjects (cardiac catheterization). Figures 1 and 2 show good correlations between DAP and weight (r =.819) and between DAP and weight fluoroscopic time product (r =.96) in cardiac catheterization. DAP in all cardiac catheterization cases TABLE 2: Congenital Heart Disease or Cardiac Abnormality in Patients Who Underwent Cardiac Catheterization for This Study Heart Disease or Abnormality No. of Patients (n = 25) Mean Fluoroscopic Time (min) Mean DAP / Weight (cgy cm 2 kg 1 ) Aortic disease Atrial septal defect Complex heart diseases Double-outlet right ventricle Ebstein anomaly Endocardial cushion defect Kawasaki disease Patent ductus arteriosus Pulmonary artery disease Tetralogy of Fallot Total anomalous pulmonary venous connection Transposition of great arteries Tricuspid atresia Ventricular septal defect Other heart diseases AJR:195, November 21

3 Radiation Dose to Pediatric Patients Downloaded from by on 1/12/18 from IP address Copyright ARRS. For personal use only; all rights reserved 16, 14, 12, 1, 8, 6, 4, 2, (n = 25) was poorly correlated with fluoroscopic time (r =.411), number of cine runs (r =.412), and BMI (r =.695). Interventional Radiology (Therapeutic) Procedures Tables 1 and 3 summarize the characteristics of the patients and results of our study overall and by patient group. The interventional radiology procedures were divided into three groups on the basis of the use of dilatation: balloon valvuloplasty and angioplasty; balloon atrial septostomy; and embolization (i.e., patent ductus arteriosus occlusion and collateral vessel embolization). Figures 3 and 4 show the good correlations between DAP and weight (r =.895) and weight fluoroscopic time product (r =.885), respectively, in all interventional radiology cases (n = 34). DAP in all interventional radiology cases (n = 34) was poorly correlated with fluoroscopic time (r =.461), number of cine runs (r =.52), and BMI (r =.426). Comparison of Cardiac Catheterization (Diagnostic) and Interventional Radiology Procedures (Therapeutic) Table 4 summarizes the characteristics of the patients and results of our study overall and by patient group. The fluoroscopic time, number of cine runs, and normalized DAP (DAP / weight) were significantly higher for an interventional radiology procedure than for cardiac catheterization (Figs. 5 7). Table 4 summarizes the correlation coefficients (r) between DAP and the factors analyzed in this study. For both cardiac catheterization and interventional radiology procedures, DAP correlated well with weight and weight fluoroscopic time product but poorly with fluoroscopic time, number of cine runs, and BMI. 2 6 Body Weight (kg) Fig. 1 Scatterplot shows relationship between dose area product (DAP) and body weight in pediatric patients who underwent cardiac catheterization (r =.819, p <.1). Line shows regression line (y = ) , 16, 14, 12, 1, 8, 6, 4, 2, Discussion For children, weight was well correlated with DAP in both cardiac catheterization and interventional radiology procedures because the x-ray output (i.e., radiation dose) to larger patients is usually greater. Therefore, weight is an effective indicator of DAP for cardiac catheterization and interventional radiology procedures in children. Onnasch et al. [15] reported the correlation between weight and DAP in pediatric catheterization for three angiographic systems (r =.65,.69, and.74); their correlations were poorer than ours was. One reason for their lower correlations is that their subjects included adults. A poor correlation between weight and radiation dose during catheterization exists for adult patients [16, 17]. We found a poor correlation between DAP and fluoroscopic time, number of cine runs, and BMI in both cardiac catheterization and interventional radiology procedures. Nevertheless, the correlation coefficient for the weight fluoroscopic time product was much 1, 2, 3, 4, Weight Fluoroscopic Time Product (kg min) 5, Fig. 2 Scatterplot shows relationship between dose area product (DAP) and weight fluoroscopic time product in pediatric patients who underwent cardiac catheterization (r =.96, p <.1). Line shows regression line (y = ). TABLE 3: Characteristics of the Pediatric Patients in Our Study Cohort and the Interventional Radiology Procedures They Underwent Balloon Valvuloplasty and Angioplasty Balloon Atrial Septostomy Embolization No. of patients No. of patients by sex (male:female ratio) 11:1 6:1 1:5 Age (y) 4.7 ± ±. 6.7 ± 4.3 Height (cm) 94.8 ± ± ± 28. Weight (kg) 18.9 ± ± ± 18.3 Fluoroscopic time (min) 37.5 ± ± ± 7.9 No. of cine runs 16.3 ± ± ± 2.5 2,711.2 ± 2, ± 8.4 2,953. ± Note Except the number of patients and number of patients by sex, data are presented as average ± SD. DAP = dose area product. higher than that for fluoroscopic time alone, especially in cardiac catheterization. Therefore, the weight fluoroscopic time product is a useful predictor of the DAP in cardiac catheterization when DAP cannot be monitored. In the current study, the fluoroscopic time, number of cine runs, and normalized DAP (DAP / weight) were significantly higher for interventional radiology procedures than for cardiac catheterization because interventional radiology procedures in many cases are more difficult and consequently require longer fluoroscopic times. Thus, the radiation dose should be kept as low as reasonably achievable, especially during pediatric interventional radiology procedures. We found that the radiation dose (i.e., fluoroscopic time, DAP, and normalized DAP [DAP / weight]) to our study group tended to be higher than has been reported in other studies [15, 18]. The major cause of this increase in the radiation dose was that our subjects included many patients with complex heart disease (Table 2), which makes catheterization AJR:195, November

4 Chida et al. 12, 12, Downloaded from by on 1/12/18 from IP address Copyright ARRS. For personal use only; all rights reserved 1, 8, 6, 4, 2, Body Weight (kg) difficult. In addition, the radiation doses (i.e., the fluoroscopic time and DAP / weight) to the three patients with Ebstein anomaly were higher than to other patients because of the associated difficulty with catheterization, especially of the pulmonary artery, while advancing the catheter and guidewire. On the other hand, our results regarding radiation exposure to patients with simple congenital heart disease, such as ventral septal defects, are equivalent to or somewhat higher than those in other reports [15, 18]. 2 Fig. 3 Scatterplot shows relationship between dose area product (DAP) and body weight in pediatric patients who underwent an interventional radiology procedure (r =.895, p <.1). Line shows regression line (y = ) , 8, 6, 4, 2, TABLE 4: Comparison of the Pediatric Patients in Our Study Cohort Who Underwent Diagnostic Cardiac Catheterization and Those Who Underwent an Interventional Radiology Procedure Cardiac Catheterization Interventional Radiology Procedure No. of patients No. of patients by sex (male:female ratio) 123:82 18:16 Age (y) 4.1 ± ± 5.2 Height (cm) 95. ± ± 4.3 Weight (kg) 17.4 ± ± 18.7 Body mass index ± ± 4.1 Fluoroscopic time (min) 24.1 ± ± 2. <.1 No. of cine runs 7.3 ± ± 8.1 <.1 1,72.6 ± 2,11.1 2,242.2 ± 2, DAP / weight (cgy cm 2 kg 1 ) ± ± <.5 Correlation coefficient (r) DAP vs weight DAP vs fluoroscopic time DAP vs no. of cine runs DAP vs body mass index DAP vs weight fluoroscopic time product Note Except the number of patients total, number of patients by sex, and p and r values, data are presented as average ± SD. Dash ( ) indicates not applicable. DAP = dose area product. a Cardiac catheterization versus interventional radiology. The radiation dose to children undergoing cardiac catheterization and interventional radiology procedures is a critical issue because of their greater radiosensitivity. One of the effective methods for reducing the radiation dose from cardiac catheterization and interventional radiology procedures is to use a lower recording speed (i.e., lower frame and pulse rates). However, as the recording speed decreases, the image presentation becomes increasingly jerky. Therefore, a higher recording speed is generally needed to image 1, 2, 3, 4, Weight Fluoroscopic Time Product (kg min) 5, Fig. 4 Scatterplot shows relationship between dose area product (DAP) and weight fluoroscopic time product in pediatric patients who underwent an interventional radiology procedure (r =.885, p <.1). Line shows regression line (y = ). p a small children because of their higher heart rates. Although another effective method for reducing radiation dose is to use the lowdose mode, image noise increases with this approach. In summary, the trade-off for a decrease in recording speed is a loss in temporal resolution. Similarly, the trade-off for a reduction in dose by lowering the pulse and frame rates is a loss in image quality. Therefore, in cardiac catheterization and interventional radiology procedures, physicians must weigh the desirability (optimal balance) of reduced radiation exposure against the need for temporal resolution and image quality, especially for children. In addition, to reduce the radiation dose to children, one should use an additional spectral beam filter and optimal beam collimation, just as in adult patients. Furthermore, radiation safety education and training for staff can reduce the amount of radiation exposure of both pediatric patients and staff during cardiac catheterization and interventional radiology procedures [19]. Although this was a single-institution study, this article provides baseline data for future research efforts and this information will be very useful for evaluating radiation dose during cardiac catheterization and interventional radiology procedures. One limitation of this study is the lack of specific organ dose data, but organ dosimetry is outside the scope of this article. Future investigations of organ dosimetry are necessary, and the risks associated with cardiac catheterization and interventional radiology procedures to each organ should be assessed. In conclusion, this article examines the current radiation dose level and related factors in children who underwent cardiac catheterization and in those who underwent an 1178 AJR:195, November 21

5 Radiation Dose to Pediatric Patients Downloaded from by on 1/12/18 from IP address Copyright ARRS. For personal use only; all rights reserved Fluoroscopic Time (min) Fig. 5 Bar graph shows average fluoroscopic time ± SD (vertical lines) was 24.1 ± 16.8 minutes (95% CI, ) for cardiac catheterization () and 37.2 ± 2. minutes ( ) for interventional radiology procedures () (p <.1). interventional radiology procedure. There was a good correlation between the DAP and weight and between the DAP and weight fluoroscopic time product for children undergoing cardiac catheterization and interventional radiology procedures. Because the radiation dose is greater in larger patients, body weight is important for determining the radiation dose to children undergoing cardiac catheterization and interventional radiology procedures. In addition, to reduce the radiation injury risk in cardiac catheterization and interventional radiology procedures, evaluation of the patient radiation dose is essential. The normalized DAP (DAP/ weight), fluoroscopy time, and number of cine runs were greater for children who underwent an interventional radiology procedure than for those who underwent cardiac catheterization. Therefore, the radiation dose to children from interventional radiology procedures is a more critical issue. Acknowledgments We thank Hirotaka Shimura, Daisuke Ito, and Shigeru Tachibana from the Department of Radiology, Tohoku University Hospital, for helpful advice regarding the technical analysis. References 1. International Commission on Radiological Pro- No. of Cine Runs Fig. 6 Bar graph shows average number of cine runs ± SD (vertical lines) was 7.3 ± 3.1 cine runs (95% CI, ) for cardiac catheterization () and 14.2 ± 8.1 cine runs ( ) for interventional radiology procedures () (p <.1). Skin injuries from fluoroscopically guided procedures. Part 1. Characteristics of radiation injury. AJR 21; 177: Koenig TR, Mettler FA, Wagner LK. Skin injuries from fluoroscopically guided procedures. Part 2. Review of 73 cases and recommendations for minimizing dose delivered to patient. AJR 21; 177: Chida K, Saito H, Zuguchi M, et al. Does digital acquisition reduce patients skin dose in cardiac interventional procedures? An experimental study. AJR 24; 183: Chida K, Kagaya Y, Saito H, et al. Total entrance skin dose: an effective indicator of maximum radiation dose to the skin during percutaneous coronary intervention. AJR 27; 189:989; [web]: W224 W Tsapaki V, Ahmed NA, AlSuwaidi JS, et al. Radiation exposure to patients during interventional procedures in 2 countries: initial IAEA project results. AJR 29; 193: Chida K, Inaba Y, Saito H, et al. Radiation dose of interventional radiology system using a flat-panel detector. AJR 29; 193: Chida K, Kato M, Saito H, et al. Optimizing patient radiation dose in intervention procedures. Acta Radiol 21; 51: Waldman JD, Rummerfield PS, Gilpin EA, et al. Radiation exposure to the child during cardiac catheterization. Circulation 1981; 64: Bacher K, Bogaert E, Lapere R, De Wolf D, Thie- DAP / Weight (cgy cm 2 kg 1 ) Fig. 7 Bar graph shows average dose area product (DAP) divided by weight (DAP / weight) ± SD (vertical lines) was ± 11.5 cgy cm 2 kg 1 (95% CI, ) for cardiac catheterization () and ± cgy cm 2 kg 1 ( ) for interventional radiology procedures () (p <.1). dose. Pediatr Radiol 26; 36[suppl 2]: Onnasch DG, Schemm A, Kramer HH. Optimization of radiographic parameters for pediatric cardiac angiography. Br J Radiol 24; 77: Chida K, Tanaka T, Saito H, et al. Ventriculography using ECG-gated multiple diastolic injection of contrast material in pediatric angiocardiography. Pediatr Cardiol 22; 23: Schmidt PW, Dance DR, Skinner CL, Smith IA, McNeill JG. Conversion factors for the estimation of effective dose in paediatric cardiac angiography. Phys Med Biol 2; 45: Onnasch DG, Schröder FK, Fischer G, et al. 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