Comparison of a conventional and a flat-panel digital system in interventional cardiology procedures

The factors contributing to the total radiation exposure of patients during uterine artery embolisation

Uterine artery embolisation (UAE) is an interventional angiography procedure for the treatment of symptomatic fibroids and/or adenomyosis in women. UAE is a less invasive and non-surgical alternative to hysterectomy or myomectomy. However, ionising radiation is used for both fluoroscopic and angiographic image guidance to visualise and access the uterine arteries for embolisation and treatment of these benign conditions. Identifying the contributors and implementing dose reduction techniques are particularly important as UAE patients are usually of child-bearing age. The purpose of this review was to examine the progression of literature on radiation exposure measurements and identifying the factors contributing to the total radiation exposure of female patients undergoing UAE. A Medline, ProQuest Central, ScienceDirect and Scopus database search from 2000 to 2018 was performed and forty articles were deemed acceptable for review following the inclusion and exclusion criteria set. UAE is a viable alternative to hysterectomy and myomectomy, as the reviewed literature demonstrated that the reported radiation exposure doses appear to be below the threshold for any deterministic radiation risks. The total radiation exposure of UAE patients is affected independently by multiple patient, operator expertise and technique, angiographic imaging and x-ray unit variables. Uterus preservation can be attained post-UAE with dose reduction and optimisation, however, a longitudinal study on UAE patients and their risk of radiation-induced deterministic and/or stochastic effects is recommended.

Optimizing imaging and reducing radiation exposure during complex aortic endovascular procedures

Improvements in endovascular technologies and development of custom-made fenestrated and branched endografts currently allow clinicians to treat complex aortic lesions such as thoraco-abdominal and aortic arch aneurysms once treatable with open repair only. These advances are leading to an increase in the complexity of endovascular procedures which can cause long operation times and high levels of radiation exposure. This in turn places pressure on the vascular surgery community to display more superior interventional skills and radiological practices. Advanced imaging technology in this context represents a strong pillar in the treatment toolbox for delivering the best care at the lowest risk level. Delivering the best patient care while managing the radiation and iodine contrast media risks, especially in frail and renal impaired populations, is the challenge aortic surgeons are facing. Modern hybrid rooms are equipped with a wide range of new imaging applications such as fusion imaging and cone-beam computed tomography (CBCT). If these technologies contribute to reducing radiation, they can be complex and intimidating to master. The aim of this review is to discuss the fundamentals of good radiological practices and to describe the various imaging tools available to the aortic surgeon, both those available today and those we anticipate will be available in the near future, from equipment to software, to perform safe and efficient complex endovascular procedures.

Radiation dose from percutaneous transluminal coronary angioplasty procedure performed using a flat detector for different clinical angiographic projections

The radiation dose from complex cardiac procedures is of concern due to the lengthy fluoroscopic screening time and vessel complexities. This study intends to assess radiation dose based on angiographic projection and vessel complexities for clinical protocols used in the performance of percutaneous transluminal coronary angioplasty (PTCA). Dose-area product (DAP), reference air kerma (K _a,r) and real-time monitoring of tube potentials and tube current for each angiographic projection and dose setting were evaluated for 66 patients who underwent PTCA using a flat detector system. The mean DAP and cumulative K _a,r were 32.71 Gy cm² (0.57 Gy), 51.24 Gy cm² (0.9 Gy) and 102.03 Gy cm² (1.77 Gy) for single-, double- and triple-vessel PTCA, respectively. Among commonly used angiographic projections, left anterior oblique 45°-caudal 35° reached 2 Gy in 55 min using a low-dose fluoroscopy setting and 21 min for a medium-dose setting. Use of a low-dose setting for fluoroscopic screening showed a radiation dose reduction of 39% compared with a medium-dose setting.

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.

Radiation doses and estimated risk from angiographic projections during coronary angiography performed using novel flat detector

Coronary angiography (CA) procedure uses various angiographic projections to elicit detailed information of the coronary arteries with some steep projections involving high radiation dose to patients. This study intends to evaluate radiation doses and estimated risk from angiographic projections during CA procedure performed using novel flat detector (FD) system with improved image processing and noise reduction techniques. Real‐time monitoring of radiation doses using kerma‐area product (KAP) meter was performed for 140 patients using Philips Clarity FD system. The CA procedure involved seven standard projections, of which five were extensively selected by interventionalists. Mean fluoroscopic time (FT), KAP, and reference air kerma (Ka,r) for CA procedure were 3.24 min (0.5–10.51), 13.99 Gycm² (4.02–37.6), and 231.43 mGy (73.8–622.15), respectively. Effective dose calculated using Monte Carlo‐based PCXMC software was found to be 4.9 mSv. Left anterior oblique (LAO) 45° projection contributed the highest radiation dose (28%) of the overall KAP. Radiation‐induced risk was found to be higher in females compared to males with increased risk of lung cancer. An increase of 10%–15% in radiation dose was observed when one or more additional projections were adopted along with the seven standard projections. A 14% reduction of radiation dose was achieved from novel FD system when low‐dose protocol during fluoroscopy and medium‐dose protocol during cine acquisitions were adopted, compared to medium‐dose protocol.

PACS number(s): 87.50.cm, 87.55.de, 87.55.N, 87.59.cf, 87.59.Dj

Therapeutic angiographic procedures: differences in dose area product between analog image intensifier and digital flat panel detector

BACKGROUND

Radiation exposure remains an unceasing concern in angiographic procedures. Modern angiography machines such as analog image intensifiers (AII) or the new flat panel detectors (FPD) aim at a further dose reduction.

PURPOSE

To present dose area products (DAP) in a broad spectrum of therapeutic angiographic procedures, comparing an AII to an FPD angiography system.

MATERIAL AND METHODS

A total of 999 peripheral therapeutic angiography procedures performed with an FPD (n = 562) and an AII system (n = 437) were evaluated. DAP, fluoroscopy time, and patients' body mass index (BMI) were recorded. Interventions were classified into five main groups: percutaneous transluminal angioplasty (PTA); PTA and stent placement; intra-arterial thrombolysis; embolization procedures; and specialized interventions.

RESULTS

DAP values in therapeutic angiographic procedures were significantly higher when performed with the FPD compared to the AII system. The increase of the FPD versus AII system was 100.1% for PTA, 39.9% for PTA and stent placement, 187% for intra-arterial thrombolysis, 31.3% for embolization procedures, and 361% for specialized interventions. These differences persisted after standardizing DAP values to the geometric mean fluoroscopy duration of each procedure. Fluoroscopy times were shorter in all interventions performed at the FPD as compared to the AII system. DAPs increased with higher BMI, but the DAP increase of both systems with elevated BMI was variable, depending on the individual intervention.

CONCLUSION

In therapeutic angiographic procedures, the FPD system required higher DAPs despite shorter fluoroscopy times as compared to an AII system. Better ergonomics and speediness of the FPD system may be advantageous in the emergency setting.

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.

Evaluation of Entrance Skin Dose during Catheter Ablation Procedures by Use of Reference Air-Kerma Displayed on Angiography Systems

BACKGROUND

Our aim in this study was to estimate entrance skin doses (ESDs) to patients who underwent catheter ablation procedures, by using a reference air-kerma (RAK) displayed on the monitor of an angiography system (displayed RAK).

METHODS

The displayed RAK was calibrated with use of an air-kerma value measured on a 20-cm-thick acrylic plate at the interventional reference point for the inclusion of backscattered x-rays (calibrated RAK). The ESD evaluated from the calibrated RAK (evaluated ESD) was verified through direct ESD measurements on an anthropomorphic phantom. The values of the evaluated ESD agreed with those of the measured ESD within a statistical error of 10% for both fluoroscopy and digital cine. The patient population included 356 consecutive patients (108 female and 248 male) who underwent catheter ablation procedures in the catheter laboratory of the Nagoya Daini Red-Cross Hospital from January 2013 to February 2014, where ablation procedures were performed for seven types of arrhythmias, i.e., atrial fibrillation (AF), atrial flutter (AFL), atrial tachycardia (AT), atrioventricular nodal reentrant tachycardia (AVNRT), ventricular premature contraction (VPC), ventricular tachycardia (VT), and Wolff-Parkinson-White syndrome (WPW).

RESULTS

Patients who had arrhythmias that received the highest evaluated ESD were those for AF, followed by those for VPC, AT, WPW, AFL, VT, and AVNRT.

CONCLUSIONS

Despite extremely long fluoroscopy times of up to 66.6 minutes in left anterior oblique projection, only one patient was considered to exceed a threshold dose of 2 Gy for the onset of radiation-induced skin injuries.

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.

Comparison of two angiographic systems in paediatric interventional cardiology

The aim of this work was to analyse the radiation dose for patients and staff between X-ray systems, a new biplane with flat-panel detectors (FDs) and a conventional system equipped with image intensifier (II). Entrance surface air kerma (ESAK) and scatter doses were measured on polymethyl methacrylate (PMMA) phantoms of different thicknesses (from 4 to 16 cm). The ESAK values for the different acquisition modes and PMMA thicknesses were higher for the II in comparison with FDs. For the II, the scatter dose rates ranged from 0.67 to 12.2 mSv h(-1) at the eye position of the cardiologist during fluoroscopy and cine modes. At the lower extremities, these values were 1.11 and 24.24 mSv h(-1). In the case of the FDs, these values ranged from 0.24 to 0.67 mSv h(-1) for eye lens and from 0.73 to 2.01 mSv h(-1) for the position of cardiologist's ankle. The newly installed X-ray system showed an average reduction factor of up to 9.7 times for ESAK values. For the staff with an average reduction factor of 15.9 times at the eye position during fluoroscopy and cine modes, no protective tools are used. At the lower extremities, this value was 7.6 times.

Comparing ovarian radiation doses in flat-panel and conventional angiography during uterine artery embolization: a randomized clinical trial

Background

Uterine artery embolization (UAE) is a minimally invasive procedure performed under fluoroscopy for the treatment of uterine fibroids and accompanied by radiation exposure.

Objectives

To compare ovarian radiation doses during uterine artery embolization (UAE) in patients using conventional digital subtraction angiography (DSA) with those using digital flat-panel technology.

Patients and Methods

Thirty women who were candidates for UAE were randomly enrolled for one of the two angiographic systems. Ovarian doses were calculated according to in-vitro phantom study results using entrance and exit doses and were compared between the two groups.

Results

The mean right entrance dose was 1586±1221 mGy in the conventional and 522.3±400.1 mGy in the flat panel group (P=0.005). These figures were 1470±1170 mGy and 456±396 mGy, respectively for the left side (P=0.006). The mean right exit dose was 18.8±12.3 for the conventional and 9.4±6.4 mGy for the flat panel group (P=0.013). These figures were 16.7±11.3 and 10.2±7.2 mGy, respectively for the left side (P=0.06). The mean right ovarian dose was 139.9±92 in the conventional and 23.6±16.2 mGy in the flat panel group (P<0.0001). These figures were 101.7±77.6 and 24.6±16.9 mGy, respectively for the left side (P=0.002).

Conclusion

Flat panel system can significantly reduce the ovarian radiation dose during UAE compared with conventional DSA.

Impact of the X-ray system setting on patient dose and image quality; a case study with two interventional cardiology systems

This study investigates the influence of the initial X-ray system setting on patient doses and image quality in interventional cardiology procedures. Two dedicated interventional cardiology systems were studied: a system with image intensifier (II) and a flat detector (FD) system. Entrance surface air kerma (ESAK) rates in fluoroscopy and ESAK per frame in the acquisition mode were measured on the surface of a PMMA phantom for the field of views (FOV) of 23 and 17 cm (II system) and 25 and 20 cm (FD system). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were estimated using DICOM images obtained during the measurements. System performances were compared using a figure of merit combining SNR and ESAK. The influence of system setting on patient doses was investigated analysing the information for air kerma area product (KAP) and cumulative dose (CD) at the patient entrance reference point, for a sample of coronary angiography examinations. ESAK rates in fluoroscopy modes were a factor of 2 higher in the FD system for the similar FOVs, resulting in a factor of 1.9 higher median values of KAP and CD for patients with FD system than for the II system. SNR and CNR for the FD system were better than the equivalent FOVs with II. The resulting FOM was better for the FD system in both FOVs. Potential for optimisation was suggested by adjusting system settings.

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

PURPOSE

The aim of this study was to estimate radiation exposure in pediatric liver transplants recipients who underwent biliary interventional procedures and to compare radiation exposure levels between biliary interventional procedures performed using an image intensifier-based angiographic system (IIDS) and a flat panel detector-based interventional system (FPDS).

MATERIALS AND METHODS

We enrolled 34 consecutive pediatric liver transplant recipients with biliary strictures between January 2008 and March 2013 with a total of 170 image-guided procedures. The dose-area product (DAP) and fluoroscopy time was recorded for each procedure. The mean age was 61 months (range 4-192), and mean weight was 17 kg (range 4-41). The procedures were classified into three categories: percutaneous transhepatic cholangiography and biliary catheter placement (n = 40); cholangiography and balloon dilatation (n = 55); and cholangiography and biliary catheter change or removal (n = 75). Ninety-two procedures were performed using an IIDS. Seventy-eight procedures performed after July 2010 were performed using an FPDS. The difference in DAP between the two angiographic systems was compared using Wilcoxon rank-sum test and a multiple linear regression model.

RESULTS

Mean DAP in the three categories was significantly greater in the group of procedures performed using the IIDS compared with those performed using the FPDS. Statistical analysis showed a p value = 0.001 for the PTBD group, p = 0.0002 for the cholangiogram and balloon dilatation group, and p = 0.00001 for the group with cholangiogram and biliary catheter change or removal.

CONCLUSION

In our selected cohort of patients, the use of an FPDS decreases radiation exposure.

Radiation exposure in vascular angiographic procedures

PURPOSE

To evaluate dose reduction in vascular angiographic procedures by using fluoroscopy capture instead of digital subtraction angiography frames for documentation.

MATERIALS AND METHODS

A total of 764 consecutive vascular interventional procedures performed over a period of 1 year were retrospectively analyzed with respect to the fluoroscopy time and the resulting dose-area product (DAP), the DAP of the radiographic frames, and the overall DAP.

RESULTS

A total of 70% of the total DAP was a result of the acquisition of radiographic frames, leaving only 30% being applied by fluoroscopy.

CONCLUSIONS

Fluoroscopy capture should be used for documentation whenever possible. A registry of radiation exposure should not only comprise a sufficiently large number of interventions but also different intervention types to allow the development of interventional reference levels.

Radiation exposure of the operator during cardiac catheter ablation procedures

Radiation exposure of the operator during cardiac catheter ablation procedures was assessed for an experienced cardiologist adopting various measures of radiation protection and utilised electroanatomic navigation. Chip thermoluminescent dosemeters were placed at the eyes, chest, wrists and legs of the operator. The ranges of fluoroscopy time and air kerma area product values associated with cardiac ablation procedures were wide (6.3-48.3 min and 1.7-80.3 Gy cm(2), respectively). The measured median radiation doses per procedure for each monitored position were 23.6 and 21.3 μSv to the left and right wrists, respectively, 25.3 and 30.4 μSv to the left and right legs, respectively. The doses to the eyes were below the minimum detectable dose of 9 μSv. The estimated median effective dose was 22.5 μSv. Considering the actual workload of the operator, the calculated annual doses to the hands, legs and eyes, as well as the annual effective dose, were all below the corresponding limits. The findings of this study indicate that cardiac ablation procedures performed at a modern laboratory do not impose a high radiation hazard to the operator when radiation protection measures are routinely adopted.

Increases in patient doses need to be avoided when upgrading interventional cardiology systems to flat detectors

The aim of this study was to evaluate patient doses in two interventional cardiology laboratories over a period of 1 y in which the imaging devices were changed from image intensifier (II) to flat detector (FD). Dosimetric data from a total of 1040 coronary angiography (CA) procedures and 1087 percutaneous transluminal coronary angioplasty (PTCA) procedures were gathered. During the period studied with II imaging, median values of dose area product were 28 Gy cm(2) for CA and 57 Gy cm(2) for PTCA. In the first half of the year with FD imaging, median values were 37 Gy cm(2) for CA and 89 Gy cm(2) for PTCA. A significant increase in patient doses was noticed in the early stages of use of FD technology for imaging IC procedures, while fluoroscopy time and number of images remained similar. A careful setting of the X-ray systems, after upgrading the imaging system, is essential to avoid unjustified increases in patient doses.

Changes in dose-area product, entrance surface dose, and lens dose to the radiologist in a vascular interventional laboratory when an old X-ray system is exchanged with a new system

PURPOSE

The aim of this study was to compare dose-area product (DAP), entrance surface dose (ESD), and lens dose to radiologists for an old and a new X-ray system in a vascular interventional laboratory.

MATERIALS AND METHODS

DAP, ESD, fluoroscopy time, number of images, and patient weight were recorded for patients undergoing the following four procedures: percutaneous transluminal angioplasty (PTA) and stenting (divided into two subgroups, lower extremities and pelvis), nephrostomy, and treatment for varicocele. Halfway through the registration period, the 9-year-old X-ray equipment was exchanged with a new system. Lens doses to the radiologist were measured.

RESULTS

There was a reduction in DAP for all procedures: PTA lower extremities 31% (12-8 Gy cm(2)), PTA/stenting pelvis 67% (134-44 Gy cm(2)), nephrostomy 39% (7-4 Gy cm(2)), and varicocele 70% (37-11 Gy cm(2)). The reduction in number of images was 17% (158-131), 23% (153-118), 68% (2-1), and 31% (50-35), explaining a part of the dose reduction. The reduction in ESD was 33, 60, 38, and 46%. The differences in measured lens doses indicate a dose reduction in three procedures (19-53%) and an increase in one (56%), but differences are not statistically significant.

CONCLUSION

DAP and ESD from the X-ray system were reduced for all procedures. The reduction was greater in the more radiation-demanding procedures.

[Radiation protection of patients in interventional radiology]

The purpose of this article is to provide radiologists with key elements of radiation protection for interventional radiology patients. The following points will be discussed: standards of the fluoroscopy units, dedicated dosimetry, risks (especially cutaneous) and means to reduce them, optimization of interventional radiology dose protocols, and national and international regulations. Appropriateness criteria in interventional radiology are national guidelines that should be implemented.

Impact of biplane versus single-plane imaging on radiation dose, contrast load and procedural time in coronary angioplasty

Coronary angioplasties can be performed with either single-plane or biplane imaging techniques. The aim of this study was to determine whether biplane imaging, in comparison to single-plane imaging, reduces radiation dose and contrast load and shortens procedural time during (i) primary and elective coronary angioplasty procedures, (ii) angioplasty to the main vascular territories and (iii) procedures performed by operators with various levels of experience. This prospective observational study included a total of 504 primary and elective single-vessel coronary angioplasty procedures utilising either biplane or single-plane imaging. Radiographic and clinical parameters were collected from clinical reports and examination protocols. Radiation dose was measured by a dose-area-product (DAP) meter intrinsic to the angiography system. Our results showed that biplane imaging delivered a significantly greater radiation dose (181.4+/-121.0 Gycm(2)) than single-plane imaging (133.6+/-92.8 Gycm(2), p<0.0001). The difference was independent of case type (primary or elective) (p = 0.862), vascular territory (p = 0.519) and operator experience (p = 0.903). No significant difference was found in contrast load between biplane (166.8+/-62.9 ml) and single-plane imaging (176.8+/-66.0 ml) (p = 0.302). This non-significant difference was independent of case type (p = 0.551), vascular territory (p = 0.308) and operator experience (p = 0.304). Procedures performed with biplane imaging were significantly longer (55.3+/-27.8 min) than those with single-plane (48.9+/-24.2 min, p = 0.010) and, similarly, were not dependent on case type (p = 0.226), vascular territory (p = 0.642) or operator experience (p = 0.094). Biplane imaging resulted in a greater radiation dose and a longer procedural time and delivered a non-significant reduction in contrast load than single-plane imaging. These findings did not support the commonly perceived advantages of using biplane imaging in single-vessel coronary interventional procedures.

Reference levels for patient radiation doses in interventional radiology: proposed initial values for U.S. practice

PURPOSE

To propose initial values for patient reference levels for fluoroscopically guided procedures in the United States.

MATERIALS AND METHODS

This secondary analysis of data from the Radiation Doses in Interventional Radiology Procedures (RAD-IR) study was conducted under a protocol approved by the institutional review board and was HIPAA compliant. Dose distributions (percentiles) were calculated for each type of procedure in the RAD-IR study where there were data from at least 30 cases. Confidence intervals for the dose distributions were determined by using bootstrap resampling. Weight banding and size correction methods for normalizing dose to patient body habitus were tested.

RESULTS

The different methods for normalizing patient radiation dose according to patient weight gave results that were not significantly different (P > .05). The 75th percentile patient radiation doses normalized with weight banding were not significantly different from those that were uncorrected for body habitus. Proposed initial reference levels for various interventional procedures are provided for reference air kerma, kerma-area product, fluoroscopy time, and number of images.

CONCLUSION

Sufficient data exist to permit an initial proposal of values for reference levels for interventional radiologic procedures in the United States. For ease of use, reference levels without correction for body habitus are recommended. A national registry of radiation-dose data for interventional radiologic procedures is a necessary next step to refine these reference levels.

Flat detectors and new aspects of radiation safety

Flat detectors are the heart of high-performance imaging systems that provide new capabilities as well as new hazards. The superior image quality enables operators to work with heavier patients and steeper projections. Under these conditions, exposure control computers automatically increase the production of x-rays to compensate for absorption by body tissues. Image quality is preserved, and operators may not be aware of the very high skin doses delivered during prolonged procedures. Although it is assumed that flat detector systems are safe, the potential for radiation overexposure and skin injury is real. This article examines the unique radiation hazards of flat detector fluoroscopy and suggests practical steps that clinicians can take to protect themselves and their patients from radiation injury.

Minimising radiation exposure to physicians performing fluoroscopically guided cardiac catheterisation procedures: a review

What is known about radiation exposure to physicians who perform cardiac interventions is reviewed and various factors that affect their exposure are discussed. There are wide variations in the radiation dose (up to 1000-fold) per procedure. Despite extensive improvements in equipment and technology, there has been little or no reduction in dose over time. The wide variation and lack of reduction in operator doses strongly suggests that more attention must be paid to factors influencing the operator dose. Numerous patient, physician and shielding factors influence the operator dose to different degrees. Operators can change some of these factors immediately, at minimal or no cost, with a substantial reduction in dose and potential cancer risk.

Patient radiation doses in interventional cardiology procedures

Interventional cardiology procedures result in substantial patient radiation doses due to prolonged fluoroscopy time and radiographic exposure. The procedures that are most frequently performed are coronary angiography, percutaneous coronary interventions, diagnostic electrophysiology studies and radiofrequency catheter ablation. Patient radiation dose in these procedures can be assessed either by measurements on a series of patients in real clinical practice or measurements using patient-equivalent phantoms. In this article we review the derived doses at non-pediatric patients from 72 relevant studies published during the last 22 years in international scientific literature. Published results indicate that patient radiation doses vary widely among the different interventional cardiology procedures but also among equivalent studies. Discrepancies of the derived results are patient-, procedure-, physician-, and fluoroscopic equipmentrelated. Nevertheless, interventional cardiology procedures can subject patients to considerable radiation doses. Efforts to minimize patient exposure should always be undertaken.

X-ray burns--painful, protracted, and preventable

Very high doses of x-ray may produce deep burns in the backs of patients having fluoroscopically guided cardiac interventional procedures. While these incidents are uncommon they can be prevented by judicious limitation of fluoroscopy and timely repositioning of the x-ray tube. Better education and improved methods for dose mapping should make these distressing complications a thing of the past.

Comparison of radiation dose to patient and staff for two interventional cardiology units: a phantom study

The purpose of this investigation was to measure the patient and staff dose during routine interventional cardiology procedures for an image intensifier-based and a flat detector system using a water phantom. The Integris BH3000 image intensifier-based (Philips) and the Axiom Artis flat detector-based (Siemens) angiography units were used in this study. The accuracy of tubes potential and irradiation timers and also internal dosimeters were verified and confirmed. A water phantom with a thickness of 18 cm was used for patient and staff dose measurements. For the Philips system, phantom entrance dose rates were 2.77 and 38.97 microGym(2) s(-1) during fluoroscopy and cineangiography. The respective dose rates for the Siemens were 1.98 and 13.46 microGym(2) s(-1). Phantom entrance dose rate was 28.5 and 65% higher for the Philips system during fluoroscopy and cineangiography, respectively. Comparing the scattered dose rates at the operator location showed that the flat detector-based Siemens system delivers five times lower dose to the operator in comparison with the image intensifier-based Philips unit. The results suggest that the decrease in received dose of the patient and staff is achievable using the flat detector system. In addition, application of lead curtain and glass is recommended to lower the cardiologist dose especially for the image intensifier-based Philips system.

Changing from image intensifier to flat detector technology for interventional cardiology procedures: a practical point of view

A small-scale internal audit has been used to evaluate the impact of the use of a dynamic flat panel detector in the clinical routine in the National Interventional Cardiology Centre in Luxembourg. The parameters tested during commissioning and constancy control of an X-ray system, the introduction of new clinical protocols, the patient and the personal staff dosimetry were considered. The technical parameters tested by the hospital physicist stay the same as for the image intensifier. No innovative protocols have been adopted due to the existence of the flat panel detector. A reduction in dose was noted after the installation of a flat detector, due mostly to the continuing education of the interventional cardiologists as well as the initial calibration of the radiological system. The understanding of the X-ray system and its possibilities is vital for the optimisation of clinical procedures in patient and staff exposure.

High patient doses in interventional cardiology due to physicians' negligence: how can they be prevented?

Interventional cardiology procedures are usually associated with high patient doses and even deterministic radiation effects may occur. Expensive digital flat panels are preferably used to lower doses, and Athens General Hospital has recently installed one. However, this study shows that it is the cardiologists' practice that lowers patients' doses. Doses delivered to patients during two time periods (pre and after radiation protection training) on a total of 1196 coronary angiographies and 506 percutaneous transluminal coronary angioplasties were measured and analysed per cardiologist. Local reference levels (LRLs) were assessed and compared with the preliminary RLs provided by the European Research Program DIMOND. Results showed that although after the training patients' dose area product, fluoroscopy time, cumulative dose and number of images acquired were lowered, the situation remained unchanged for the cardiologist who delivered the highest doses. The question to answer next is how this bad practice can be prevented since no dose constraints apply to diagnostic or therapeutic procedures using ionising radiation.

Level of patient and operator dose in the largest cardiac centre in Greece

The objective of this study was to investigate the patient and staff doses in the most frequent interventional cardiology (IC) procedures performed in Onassio, the largest Cardiac Centre in Greece. Data were collected from three digital X-ray systems for 212 coronary angiographies, 203 percutaneous transluminal coronary angioplasties (PTCA) and 134 various electrophysiological studies. Patient skin dose was measured using suitably calibrated slow radiotherapy films and cardiologist dose using suitably calibrated thermoluminescent dosemeters placed on left arm, hand and foot. Patient median dose area product (DAP) (all examinations) ranged between 6.7 and 83.5 Gy cm2. Patient median skin dose in PTCA was 799 mGy (320-1660 mGy) and in RF ablation 160 mGy (35-1920 mGy). Median arm, hand and foot dose to the cardiologist were 12.6, 27 and 13 microSv, respectively, per procedure. The great range of radiation doses received by both patients and operators confirms the need for continuous monitoring of all IC techniques.

Commissioning and constancy protocols for digital angiographic units

During the European Concerted Action SENTINEL 'Safety and Efficacy for New Techniques and Imaging using New Equipment to Support European Legislation', protocols for commissioning and constancy tests for dynamic digital flat detectors angiography units have been developed in order to harmonise practice among the European counties. The commissioning protocol includes measurements on X-ray tube and generator, patient and detector radiation dose and image quality. The constancy protocol is based on the dose and image quality measurements. The commissioning protocol was tested by SENTINEL partners who expressed an interest in checking their dynamic digital systems using this protocol. The results of basic tests are reported.

An investigation into patient and staff doses from X-ray angiography during coronary interventional procedures

Radiation doses to patients from interventional coronary X-ray procedures are relatively high when compared with conventional radiographic procedures. These high patient doses can translate into high staff doses owing to scattered radiation. This study investigates patient doses by means of dose-area product (DAP) meters installed in six rooms in two hospitals. DAP measurements in each room ranged from 28.0-39.3 Gy cm2 for coronary angiography and from 61.3-92.8 Gy cm2 for percutaneous transluminal coronary angioplasty, with the mean effective doses calculated to range between 5.1-6.6 mSv and 11.2-17.0 mSv, respectively. These values are comparable with those found in recent literature. DAP measurements were found to correlate strongly (correlation coefficient of 79%) with patient weight. The non-uniform scatter radiation fields surrounding the irradiated area during coronary angiography were also investigated using a tissue equivalent phantom and an ionization chamber. Exposure rates of scattered radiation from digital acquisition were found to be around 16 times higher than those generated from fluoroscopy, and oblique-angled imaging led to greater amounts of scatter owing to the increase in related exposure factors. The distribution of scatter from oblique projections confirms that X-ray photons in the diagnostic energy range are preferentially scattered backwards, toward the X-ray tube. These concepts are a major consideration when training individuals working in the angiography suite in order to keep doses "as low as reasonably practicable".

Influence of flat-panel fluoroscopic equipment variables on cardiac radiation doses

PURPOSE

To assess the influence of physician-selectable equipment variables on the potential radiation dose reductions during cardiac catheterization examinations using modern imaging equipment.

MATERIALS

A modern bi-plane angiography unit with flat-panel image receptors was used. Patients were simulated with 15-30 cm of acrylic plastic. The variables studied were: patient thickness, fluoroscopy pulse rates, record mode frame rates, image receptor field-of-view (FoV), automatic dose control (ADC) mode, SID/SSD geometry setting, automatic collimation, automatic positioning, and others.

RESULTS

Patient radiation doses double for every additional 3.5-4.5 cm of soft tissue. The dose is directly related to the imaging frame rate; a decrease from 30 pps to 15 pps reduces the dose by about 50%. The dose is related to [(FoV)(-N )] where 2.0 < N < 3.0. Suboptimal positioning of the patient can nearly double the dose. The ADC system provides three selections that can vary the radiation level by 50%. For pediatric studies (2-5 years old), the selection of equipment variables can result in entrance radiation doses that range between 6 and 60 cGy for diagnostic cases and between 15 and 140 cGy for interventional cases. For adult studies, the equipment variables can produce entrance radiation doses that range between 13 and 130 cGy for diagnostic cases and between 30 and 400 cGy for interventional cases.

CONCLUSIONS

Overall dose reductions of 70-90% can be achieved with pediatric patients and about 90% with adult patients solely through optimal selection of equipment variables.

Do flat detector cardiac X-ray systems convey advantages over image-intensifier-based systems? Study comparing X-ray dose and image quality

The recent introduction of "flat-panel detector" (FD)-based cardiac catheterisation laboratories should offer improvements in image quality and/or dose efficiency over X-ray systems of conventional design. We compared three X-ray systems, one image-intensifier (II)-based system (system A), and two FD-based designs (systems B and C), assessing their image quality and dose efficiency. Phantom measurements were performed to assess dose rates in fluoroscopy and cine acquisition. Phantom dose rates were broadly similar for all systems, with all systems classified as offering "low" dose rates in fluoroscopy on standard phantoms. Patient X-ray dose rate and subjective image quality was assessed for 90 patients. Dose area product (DAP) rates were similar for all systems, except system C, which had a lower DAP rate in fluoroscopy. In terms of subjective image quality, the order of preference was (best to worst): system C, system A, system B. This study indicates that the use of an FD detector does not infer an automatic improvement in image quality or dose efficiency over II based designs. Specification and configuration of all of the components in the X-ray system contribute to the dose levels used and image quality achieved.

Comparison of radiation doses to patients undergoing standard radiographic examinations with conventional screen–film radiography, computed radiography and direct digital radiography

New flat-panel direct digital radiography equipment has recently been installed in our Accident and Emergency Department; its characteristics and versatility are well suited to the work undertaken in this environment. The aim of this study was to compare radiation doses to patients undergoing standard radiographic examinations using conventional screen-film radiography, computed radiography and direct digital radiography; entrance surface dose and effective dose were calculated for six standard examinations (a total of 10 projections) using standard patient exposure parameters for the three imaging modalities. It was found that doses for computed radiography (all examinations) were higher than the doses for the other two modalities; effective doses for direct digital radiography were approximately 29% and approximately 43% lower than those for screen-film radiography and computed radiography, respectively. The image quality met the criteria in the European guidelines for all modalities.

Angle-independent measure of motion for image-based gating in 3D coronary angiography

The role of three-dimensional (3D) image guidance for interventional procedures and minimally invasive surgeries is increasing for the treatment of vascular disease. Currently, most interventional procedures are guided by two-dimensional x-ray angiography, but computed rotational angiography has the potential to provide 3D geometric information about the coronary arteries. The creation of 3D angiographic images of the coronary arteries requires synchronization of data acquisition with respect to the cardiac cycle, in order to minimize motion artifacts. This can be achieved by inferring the extent of motion from a patient's electrocardiogram (ECG) signal. However, a direct measurement of motion (from the 2D angiograms) has the potential to improve the 3D angiographic images by ensuring that only projections acquired during periods of minimal motion are included in the reconstruction. This paper presents an image-based metric for measuring the extent of motion in 2D x-ray angiographic images. Adaptive histogram equalization was applied to projection images to increase the sharpness of coronary arteries and the superior-inferior component of the weighted centroid (SIC) was measured. The SIC constitutes an image-based metric that can be used to track vessel motion, independent of apparent motion induced by the rotational acquisition. To evaluate the technique, six consecutive patients scheduled for routine coronary angiography procedures were studied. We compared the end of the SIC rest period (rho) to R-waves (R) detected in the patient's ECG and found a mean difference of 14 +/- 80 ms. Two simultaneous angular positions were acquired and rho was detected for each position. There was no statistically significant difference (P = 0.79) between rho in the two simultaneously acquired angular positions. Thus we have shown the SIC to be independent of view angle, which is critical for rotational angiography. A preliminary image-based gating strategy that employed the SIC was compared to an ECG-based gating strategy in a porcine model. The image-based gating strategy selected 61 projection images, compared to 45 selected by the ECG-gating strategy. Qualitative comparison revealed that although both the SIC-based and ECG-gated reconstructions decreased motion artifact compared to reconstruction with no gating, the SIC-based gating technique increased the conspicuity of smaller vessels when compared to ECG gating in maximum intensity projections of the reconstructions and increased the sharpness of a vessel cross section in multi-planar reformats of the reconstruction.

Factors That Influence Radiation Dose in Percutaneous Coronary Intervention

AIM

To explore the factors that may influence the radiation dose imparted to the patient in PCI, and investigate whether the use of the latest digital X-ray system based on FP detector technology can have an impact on dose.

MATERIALS AND METHOD

Demographic and clinical data such as number of lesions treated, number of stents placed, grade of tortuosity, and stage of occlusion, as well as use of double wire and double balloon technique, ostial stenting or bifurcation stenting, and presence of major complications were recorded, together with radiation parameters.

RESULTS

The factors that increased patient radiation dose were (1) patient gender, as men exhibited higher doses than women; (2) complex lesion; (3) increasing number of stents; (4) position of stent; (5) grade of tortuosity; and (6) stage of occlusion. The FP digital system appeared to be settled in a lower-dose rate for fluoroscopy (a factor of 6) and higher for dose per frame in cine (a factor of 3) in comparison with the image intensifier (II) system. There was a marked reduction of DAP when the FP technology was introduced.

CONCLUSION

More extensive studies should be performed in the future so as to further investigate the influence of the FP detector in IC.