Radiation exposure in biliary procedures performed to manage anastomotic strictures in pediatric liver transplant recipients: comparison between radiation exposure levels using an image intensifier and a flat-panel detector-based system

Radiation Exposure in Pediatric Interventional Procedures

The article is part of the series of articles on radiation protection. You can find further articles in the special section of the CVIR issue. The expanding applications of interventional procedures coupled with the potential harmful effects of ionizing radiation highlight the need to assess the delivered radiation dose and establish an effective radiation protection program, particularly in the radiosensitive pediatric population. Given the complexity and heterogeneity of interventional procedures as well as the unique characteristics of children, the management of radiation dose is proving to be quite challenging. The aim of the current article is to provide an overview of the radiation exposure in pediatric patients during interventional procedures focusing on the importance of radiation protection in the pediatric population, the reported radiation doses and the techniques of minimizing radiation dose.

Flat Panel Detector c-Arms Are Associated with Dramatically Reduced Radiation Exposure During Ureteroscopy and Produce Superior Images

Background: We wished to determine whether newly available flat panel detector (FPD) c-arms were (1) associated with lower radiation dose during ureteroscopy (URS) than conventional image intensifier (CII) c-arms and (2) to compare fluoroscopic image quality between the units. Materials and Methods: We retrospectively reviewed 44 consecutive patients undergoing URS at a pediatric hospital, with c-arms assigned by availability in the operating room. We performed dosimetry experiments using the same c-arms on standard phantoms. Results: Patient and case characteristics did not differ significantly between the two groups of patients. The median dose in the FPD group was less than a quarter of the dose in the CII group, 0.48 [0.42, 0.97] mGy vs 2.2 [1.1, 3.8] mGy, p < 0.0001. The FPD dose remained at less than one-third of the CII dose accounting for any difference in fluoroscopy time, and remained significant in a multivariate model including fluoroscopy time and patient weight (β = 2.4, p = 0.007). Phantom studies showed higher image quality for FPDs at all simulated patient sizes, even at lower radiation doses. Conclusions: This is the first report comparing radiation dose from c-arms of image intensifiers and FPDs in adults or children. Use of an FPD during URS was associated with a substantially decreased absorbed dose for patients while simultaneously improving image quality.

OCCUPATIONAL RADIATION DOSE PERFORMING HEPATOBILIARY MINIMALLY INVASIVE PROCEDURES IN CHILDREN WEIGHING LESS THAN 20 kg

Our objective is to retrospectively evaluate the effective dose (E) of operators performing pediatric Hepatobiliary Minimally Invasive Procedures (HMIP). Between October 2015 and December 2017, 58 consecutive HMIP were performed on 26 children weighing less than 20 kg (mean 12.3 kg, median 13 kg, range 2.4-20 kg). About 31 vascular procedures (n = 9 hepatic venograms with/without stenting; n = 9 retrograde wedge portography; n = 8 transhepatic portography with angioplasty and/or stenting and n = 5 hepatic arteriography/embolization) and 27 non-vascular procedures (n = 6 percutaneous transhepatic biliary drainage (PTBD); n = 3 bilioplasty; n = 15 biliary catheter change and n = 3 cholangiogram) were performed. Electronic personal dosimeters were used to measure radiation doses to the interventional radiologist, radiographer and anesthesia nurse. The results shows the highest mean effective dose: interventional radiologist's in PTBD (1.18 μSv); radiographer's in hepatic veins phlebography with/without stenting (0.25 μSv) and nurse's in hepatic arteriography/embolization (0.26 μSv). Operators' E can vary depending on the complexity of procedure performed and the position of the operators within the angiosuite.

Establishing local diagnostic reference levels for pediatric percutaneous transhepatic cholangiography interventions and optimizing the routine practice

BACKGROUND

Liver-transplanted, immunosuppressed pediatric patients undergoing repeated percutaneous transhepatic cholangiography (PTC) require optimized exposure to ionizing radiation.

OBJECTIVE

To establish local diagnostic reference levels (DRL) for pediatric PTC and investigate the routine use of X-ray equipment.

MATERIALS AND METHODS

The study retrospectively analyzed data collected between October 2016 and June 2018 from a single center performing PTC. We collected exposure parameters including kerma area product (P_KA), air kerma at patient entrance reference point (K_a,r) and fluoroscopy time via a dose archiving and communication system. Local diagnostic reference levels were derived as the 50th percentile of the distributions while considering published recommended weight groups. We investigated exposure variability with procedure complexity and with technical parameters recovered from the radiation dose structured report.

RESULTS

The analysis included 162 PTC procedures performed in 64 children: 58% male, average age 6 years (range 39 days to 16 years) and weight 24 kg (range 3-60 kg). Local DRLs for weight groups 0-5 kg, 5-15 kg, 15-30 kg, 30-50 kg and 50-80 kg were, respectively, 6 cGy.cm², 22 cGy.cm², 68 cGy.cm², 107 cGy.cm² and 179 cGy.cm² in P_KA. Local DRLs per weight group were also established for intermediate and complex procedures. Radiation dose structured report analysis highlighted good local practice with efficient collimation, low fluoroscopy pulse rate, no magnification and limited use of radiographic acquisitions. Meanwhile, table and detector positioning and tube projection could still be optimized. P_KA correlated significantly with the number of acquisitions and tube-to-table distance.

CONCLUSION

We established local DRLs for children undergoing PTC.

Impact of low dose settings on radiation exposure during pediatric fluoroscopic guided interventions

PURPOSE

To evaluate the effects of lowering the detector entrance exposure in children undergoing interventional radiology procedures.

MATERIALS AND METHODS

The study retrospectively investigated radiation dose levels in pediatric patients aged 0-18 years before (n = 39) and after (n = 26) lowering detector entrance dose, undergoing embolization of peripheral Arteriovenous malformations, Portal Vein Interventions or Percutaneous Transhepatic Cholangio Drainage (PTCD) between 2014 and 2017. Patient characteristics, fluoroscopy time, protocols used as well as resulting Skin Dose and Dose Area Product (DAP) were compared in each cohort. Image quality was assessed by two independent readers.

RESULTS

The two patient cohorts did not differ in terms of patient demographics. Similarly, fluoroscopy time did not differ before and after implementation of the low dose settings. An overall reduction of skin dose of 75.1% for AVM embolizations, 80.5% for Portal Vein Interventions and 85.3% for PTCD placement was observed. The DAP decrease was 82.5% for AVM embolizations, 72.2% for Portal Vein Interventions and 79.8% for PTCD placement. Image quality was generally considered to be good with an insignificant difference between pre and post implementation of the low dose approach and good agreement between the two readers. Manual inroom-switching to higher dose levels was possible, however this was not performed more frequently after implementation of the low dose settings.

CONCLUSION

Lowering the detector entrance dose in pediatric interventional radiology procedures results in a significant decrease of the radiation dose burden.

Radiation Risk to the Fluoroscopy Operator and Staff

OBJECTIVE

Recent articles discussing cases of brain cancer in interventionalists have raised concerns regarding the hazards of occupational exposure to ionizing radiation. We review the basics of radiation dose and the potential radiation effects, particularly as they pertain to the operator. Then we present the data regarding the risk of each type of radiation effect to the fluoroscopy operator and staff, with special attention on cancer induction, radiation-induced cataracts, and the pregnant operator.

CONCLUSION

Although the evidence overwhelmingly shows that exposure to higher doses of radiation carries a risk of cancer and tissue reactions, the risks of chronic exposure to low-level radiation are less clear. Many studies examining occupational exposure to radiation fail to show an increased risk of stochastic effects of radiation, but the positive results raise concern that the studies are underpowered to consistently detect the small risk. The lack of information in these studies about radiation doses and adherence to radiation protection further confound their interpretation. Large prospective studies of populations with occupational exposure to low-level radiation might clarify this issue. More clearly established are the risks of radiation to the fetus and the risk of cataracts in interventional cardiologists and interventional radiologists. Interventionalists can mitigate these risks by following established radiation safety practices.

Investigation of reference levels and radiation dose associated with abdominal EVAR (endovascular aneurysm repair) procedures across several European Centres

OBJECTIVES

Endovascular aneurysm repair (EVAR) is considered the treatment of choice for abdominal aortic aneurysms with suitable anatomy. In order to improve radiation safety, European Directive (2013/59) requires member states to implement diagnostic reference levels (DRLs) in radio-diagnostic and interventional procedures. This study aimed to determine local DRLs for EVAR across five European centres and identify an interim European DRL, which currently remains unestablished.

METHODS

Retrospective data was collected for 180 standard EVARs performed between January 2014 and July 2015 from five specialist centres in Ireland (n=2) and Italy (n=3). Data capture included: air kerma-area product (P_KA), total air kerma at the reference point (K_a,r), fluoroscopic time (FT), number of acquisitions, frame rate of acquisition, type of acquisition, patient height, weight, and gender.

RESULTS

The mean values for each site A, B, C, D, and E were: P_KAs of 4343 ± 994 μGym², 18,200 ± 2141 μGym², 11,423 ± 1390 μGym², 7796 ± 704 μGym², 31,897 ± 5798 μGym²; FTs of 816 ± 92 s, 950 ± 150 s, 708 ± 70 s, 972 ± 61 s, 827 ± 118 s; and number of acquisitions of 6.72 ± 0.56, 10.38 ± 1.54, 4.74 ± 0.19, 5.64 ± 0.36, 7.28 ± 0.65, respectively. The overall pooled 75th percentile P_KA was 15,849 μGym².

CONCLUSION

Local reference levels were identified. The pooled data has been used to establish an interim European DRL for EVAR procedures.

KEY POINTS

• Abdominal endovascular aneurysm repair (EVAR) requires the use of ionising radiation. • EVAR is a minimally invasive procedure for the treatment of abdominal aortic aneurysms. • Diagnostic reference levels (DRLs) are used to monitor patient radiation exposure. • Radiation dose data was collected from five European centres for EVAR procedures. • Local DRLs have been determined and an interim European DRL is proposed.

Direct Effective Dose Calculations in Pediatric Fluoroscopy-Guided Abdominal Interventions with Rando-Alderson Phantoms - Optimization of Preset Parameter Settings

Objective

The aim of the study was to calculate the effective dose during fluoroscopy-guided pediatric interventional procedures of the liver in a phantom model before and after adjustment of preset parameters.

Methods

Organ doses were measured in three anthropomorphic Rando-Alderson phantoms representing children at various age and body weight (newborn 3.5kg, toddler 10kg, child 19kg). Collimation was performed focusing on the upper abdomen representing mock interventional radiology procedures such as percutaneous transhepatic cholangiography and drainage placement (PTCD). Fluoroscopy and digital subtraction angiography (DSA) acquisitions were performed in a posterior-anterior geometry using a state of the art flat-panel detector. Effective dose was directly measured from multiple incorporated thermoluminescent dosimeters (TLDs) using two different parameter settings.

Results

Effective dose values for each pediatric phantom were below 0.1mSv per minute fluoroscopy, and below 1mSv for a 1 minute DSA acquisition with a frame rate of 2 f/s. Lowering the values for the detector entrance dose enabled a reduction of the applied effective dose from 12 to 27% for fluoroscopy and 22 to 63% for DSA acquisitions. Similarly, organ doses of radiosensitive organs could be reduced by over 50%, especially when close to the primary x-ray beam.

Conclusion

Modification of preset parameter settings enabled to decrease the effective dose for pediatric interventional procedures, as determined by effective dose calculations using dedicated pediatric Rando-Alderson phantoms.

Radiation Protection for the Fluoroscopy Operator and Staff

OBJECTIVE

The purposes of this article are to review available data regarding the range of protection devices and garments with a focus on eye protection and to summarize techniques for reducing scatter radiation exposure.

CONCLUSION

Fluoroscopy operators and staff can greatly reduce their radiation exposure by wearing properly fitted protective garments, positioning protective devices to block scatter radiation, and adhering to good radiation practices. By understanding the essentials of radiation physics, protective equipment, and the features of each imaging system, operators and staff can capitalize on opportunities for radiation protection while minimizing ergonomic strain. Practicing and promoting a culture of radiation safety can help fluoroscopy operators and staff enjoy long, productive careers helping patients.

Comparison of image quality and radiation dose between an image-intensifier system and a newer-generation flat-panel detector system — technical phantom measurements and evaluation of clinical imaging in children

BACKGROUND

Many image-intensifier fluoroscopy systems have been replaced by flat-panel detectors in recent years.

OBJECTIVE

To compare the level of contrast, image resolution and radiation dose between an image-intensifier and a newer-generation flat-panel detector system in a pediatric radiology unit.

MATERIALS AND METHODS

We compared two systems — a conventional image intensifier and a newer-generation flat-panel system. We measured image quality and radiation dose using a technical phantom. Additionally, we retrospectively compared age-matched fluoroscopic pediatric voiding cystourethrography (n = 15) and upper gastrointestinal investigations (n = 25).

RESULTS

In phantom studies image contrast was equal while image resolution was higher and mean radiation dose lower using the flat-panel system (P < 0.0001). In pediatric investigations, mean dose area product was significantly reduced on the flat-panel system for upper gastrointestinal investigation (45 ± 38 μGy*m2 vs. 11 ± 9 μGy*m2; P < 0.0001) and for voiding cystourethrography (18 ± 20 μGy*m2 vs. 10 ± 12 μGy*m2; P = 0.04).

CONCLUSION

The newer flat-panel system performs at lower dose levels with equal to better image quality and therefore seems to be the more suitable technique for pediatric fluoroscopy in comparison to image-intensifier systems.

Transition from image intensifier to flat panel detector in interventional cardiology: Impact of radiation dose

Flat panel detector (FPD) technology in interventional cardiology is on the increase due to its varied advantages compared to the conventional image intensifier (II) systems. It is not clear whether FPD imparts lower radiation doses compared to II systems though a few studies support this finding. This study intends to compare radiation doses from II and FPD systems for coronaryangiography (CAG) and Percutaneous Transluminal Coronary Angioplasty (PTCA) performed in a tertiary referral center. Radiation doses were measured using dose area product (DAP) meter from patients who underwent CAG (n = 222) and PTCA (n = 75) performed using FPD angiography system. The DAP values from FPD were compared with earlier reported data using II systems from the same referral center where the study was conducted. The mean DAP values from FPD system for CAG and PTCA were 24.35 and 63.64 Gycm(2) and those from II system were 27.71 and 65.44 Gycm(2). Transition from II to FPD system requires stringent dose optimization strategies right from the initial period of installation.

Radiation Exposure in Transjugular Intrahepatic Portosystemic Shunt Creation

PURPOSE

Transjugular intrahepatic portosystemic shunt (TIPS) creation is considered as being one of the most complex procedures in abdominal interventional radiology. Our aim was twofold: quantification of TIPS-related patient radiation exposure in our center and identification of factors leading to reduced radiation exposure.

MATERIALS AND METHODS

Three hundred and forty seven consecutive patients underwent TIPS in our center between 2007 and 2014. Three main procedure categories were identified: Group I (n = 88)-fluoroscopic-guided portal vein targeting, procedure done in an image intensifier-based angiographic system (IIDS); Group II (n = 48)--ultrasound-guided portal vein puncture, procedure done in an IIDS; and Group III (n = 211)--ultrasound-guided portal vein puncture, procedure done in a flat panel detector-based system (FPDS). Radiation exposure (dose-area product [DAP], in Gy cm(2) and fluoroscopy time [FT] in minutes) was retrospectively analyzed.

RESULTS

DAP was significantly higher in Group I (mean ± SD 360 ± 298; median 287; 75th percentile 389 Gy cm(2)) as compared to Group II (217 ± 130; 178; 276 Gy cm(2); p = 0.002) and Group III (129 ± 117; 70; 150 Gy cm(2) p < 0.001). The difference in DAP between Groups II and III was also significant (p < 0.001). Group I had significantly longer FT (25.78 ± 13.52 min) as compared to Group II (20.45 ± 10.87 min; p = 0.02) and Group III (19.76 ± 13.34; p < 0.001). FT was not significantly different between Groups II and III (p = 0.73).

CONCLUSIONS

Real-time ultrasound-guided targeting of the portal venous system during TIPS creation results in a significantly lower radiation exposure and reduced FT. Further reduction in radiation exposure can be achieved through the use of modern angiographic units with FPDS.

Comparison between radiation exposure levels using an image intensifier and a flat-panel detector-based system in image-guided central venous catheter placement in children weighing less than 10 kg

BACKGROUND

Ultrasound-guided central venous puncture and fluoroscopic guidance during central venous catheter (CVC) positioning optimizes technical success and lowers the complication rates in children, and is therefore considered standard practice.

OBJECTIVE

The purpose of this study was to compare the radiation exposure levels recorded during CVC placement in children weighing less than 10 kg in procedures performed using an image intensifier-based angiographic system (IIDS) to those performed in a flat-panel detector-based interventional suite (FPDS).

MATERIALS AND METHODS

A retrospective review of 96 image-guided CVC placements, between January 2008 and October 2013, in 49 children weighing less than 10 kg was performed. Mean age was 8.2 ± 4.4 months (range: 1-22 months). Mean weight was 7.1 ± 2.7 kg (range: 2.5-9.8 kg). The procedures were classified into two categories: non-tunneled and tunneled CVC placement.

RESULTS

Thirty-five procedures were performed with the IIDS (21 non-tunneled CVC, 14 tunneled CVC); 61 procedures were performed with the FPDS (47 non-tunneled CVC, 14 tunneled CVC). For non-tunneled CVC, mean DAP was 113.5 ± 126.7 cGy cm(2) with the IIDS and 15.9 ± 44.6 cGy · cm(2) with the FPDS (P < 0.001). For tunneled CVC, mean DAP was 84.6 ± 81.2 cGy · cm(2) with the IIDS and 37.1 ± 33.5 cGy cm(2) with the FPDS (P = 0.02).

CONCLUSION

The use of flat-panel angiographic equipment reduces radiation exposure in small children undergoing image-guided CVC placement.

Diagnosis and management of biliary complications in pediatric living donor liver transplant recipients

The incidence of biliary complications (BCs) after living donor liver transplantation (LDLT) can reach 40%. Published data on the pediatric population are limited, and treatment protocols vary. Our aim was to describe the clinical scenario for BCs and treatment approaches after LDLT. Between October 1995 and December 2012, 489 pediatric LDLT procedures were performed. BCs developed in 71 patients (14.5%). Biliary strictures (BSs) developed in 45 (9.2%) patients, and bile leaks (BLs) developed in 33 patients (6.7%). The BL diagnosis was clinical in all cases, and 69.7% of the patients underwent surgery. Nearly half of the BS cases had clinical features or suggestive ultrasound findings. Liver biopsy findings suggested BSs in 51.7%. Percutaneous transhepatic cholangiography was performed in 95.6% of the BS patients. The success rate was 77% [mean number of percutaneous biliary interventions (PBIs) = 3.9 ± 1.98, median drainage time = 8 months]. In conclusion, BL patients can be managed with conservative therapy, even though most of these patients will ultimately be treated with surgery. Diagnosing a BS requires a high degree of clinical suspicion because the available resources for its identification can fail in up to 50% of cases. A higher number of PBIs and the use of a drainage catheter for a longer time may be required to achieve better results with this technique.