National survey to update the diagnostic reference levels in interventional radiology procedures in Italy: working methodology

Interventional Radiology (IR) deals with the diagnosis and treatment of various diseases through medically guided imaging. It provides unquestionable benefits to patients, but requires, in many cases, the use of high doses of ionizing radiation with a high impact on radiation risks to patients and to overall dose to the population. The International Commission on Radiological Protection introduced Diagnostic reference levels (DRLs) as an effective tool to facilitate dose verification and optimize protection for patients undergoing radiological procedures. In addition, EURATOM Council Directive 2013/59 and its Italian transposition (Legislative Decree 101/2020) have reiterated that DRLs must be established for many common radiological diagnostic procedures to compare the radiation dose delivered for the same diagnostic examination. Within this framework, Istituto Superiore di Sanità-Italian National Institute of Health (ISS)-, in collaboration with relevant Italian Scientific Societies, has provided documents on DRLs in radiological practices such as diagnostic and IR and diagnostic nuclear medicine. These reference documents enable National Hospitals to comply national regulation. The implementation of DRLs in IR is a difficult task because of the wide distribution of doses to patients even within the same procedure. Some studies have revealed that the amount of radiation in IR procedures is influenced more by the complexity of the procedure than by the weight of the patient, so complexity should be included in the definition of DRLs. For this reason, ISS promoted a survey among a sample of Italian Centers update national DRL in IR procedures with related complexity factors than can be useful for other radiological centers and to standardize the DRLs values. In the present paper the procedural methodology developed by ISS and used for the survey will be illustrated.

Radiation dose aspects and establishment of diagnostic reference levels for90Y radioembolisation during angiographic procedure

⁹⁰Y radioembolisation (RE) is an angiographic procedure used in patients with both primary and secondary hepatic malignancies. Local tumour control can be achieved by short range tumour irradiation by the regional intra-arterial administration of glass or resin microspheres loaded with 90yttrium that accumulate in the tumorous tissue. The aim of this study was to investigate the radiation exposure of RE and to establish a local diagnostic reference level (DRL). In this retrospective study, dose data from 397 procedures in 306 patients (mean age 67.4 ± 10.6 years, 82 female) who underwent RE between 06/2017 and 01/2022 using one of two different angiography systems were analysed. DRL was set as the 75th percentile of the dose distribution. In the overall population, dose area product (DAP) (median (interquartile range, IQR)) was 26 Gy cm²(IQR 12-50) with a median fluoroscopy time (FT) of 4.5 min (IQR 2.9-8.0). FT and DAP increased significantly with the number of infusion positions (median, IQR): one position 23 Gy cm²(12-46), two positions 33 Gy cm²(14-60), three positions 50 Gy cm²(24-82) (p< 0.0001). Local DRL is 47 Gy cm²for RE and 111 Gy cm²for RE with additional embolisation. Radiation exposure and FT are significantly higher with increasing number of infusion positions as well as additional embolisation. Our established DRLs for RE may serve as a benchmark for dose optimisation.

Operator Radiation Exposure During Transfemoral Transcatheter Aortic Valve Replacement

Background

The level of radiation exposure received by operators performing transcatheter aortic valve replacement (TAVR) is not well investigated. The aim of this study is to measure the amount of radiation received by operators performing transfemoral TAVR and to identify various patient and procedural characteristics associated with increased radiation exposure.

Methods

Primary (operator 1) and secondary (operator 2) operators' equivalent radiation doses in micro Sieverts (µSv) were calculated prospectively using real-time radiation dosimeters for a total of 140 consecutive transfemoral TAVRs. Corresponding eye and thorax radiation exposures between the operators were compared. Associations between various patient and procedural characteristics and the radiation exposure were tested using the t-test and Wilcoxon Mann-Whitney rank-sum test with Monte Carlo estimation. Multivariable regression analysis was also conducted.

Results

Operator 1 had significantly higher cumulative equivalent radiation exposure than operator 2 (86 µSv vs 38 µSv, p-value: <0.0001) which was consistent at the level of the thorax (67 µSv vs 22 µSv, p-value: <0.0001), but not at the level of the eye (16.5 µSv vs 15 µSv, p-value: 0.30). On multivariable analysis, patient obesity and intraprocedural complications were associated with higher radiation exposure to both operators. Ad hoc percutaneous coronary intervention led to excessive radiation exposure to the secondary operator.

Conclusions

Transfemoral TAVR is associated with a modest amount of radiation exposure to operators and is significantly higher for the primary operator than for the secondary operator.

Establishment of national diagnostic reference levels for percutaneous coronary interventions (PCIs) in Thailand

PURPOSE

To establish national diagnostic reference levels (DRLs) for percutaneous coronary intervention (PCI) in Thailand for lesions of different complexity.

METHODS

Radiation dose quantity as kerma-area-product (KAP) and cumulative air-kerma at reference point (CAK) from 76 catheterization labs in 38 hospitals in PCI registry of Thailand was transferred online to central data management. Sixteen months data (May 2018 to August 2019) was analyzed. We also investigated role of different factors that influence radiation dose the most.

RESULTS

Analysis of 22,737 PCIs resulted in national DRLs for PCI of 91.3 Gy.cm² (KAP) and 1360 mGy (CAK). The NDRLs for KAP for type C, B2, B1 and A lesions were 106.8, 82.6, 67.9, and 45.3 Gy.cm² respectively and for CAK, 1705, 1247, 962, and 790 mGy respectively. Thus, as compared to lesion A, lesion C had more than double the dose and B2 had nearly 1.6 times and B1 had 1.2 times CAK. Our DRL values are lower than other Asian countries like Japan and Korea and are in the middle range of Western countries. University hospital had significantly higher dose than private or public hospital possibly because of higher load of complex procedures in university hospitals and trainees performing the procedures. Transradial approach showed lower doses than transfemoral approach.

CONCLUSIONS

This large multi-centric study established DRLs for PCIs which can act as reference for future studies. A hallmark of our study is establishment of reference levels for coronary lesions classified as per ACC/AHA and thus for different complexities.

Monte Carlo simulations and phantom validation of low-dose radiotherapy to the lungs using an interventional radiology C-arm fluoroscope

PURPOSE

To use MC simulations and phantom measurements to investigate the dosimetry of a kilovoltage x-ray beam from an IR fluoroscope to deliver low-dose (0.3-1.0 Gy) radiotherapy to the lungs.

MATERIALS AND METHODS

PENELOPE was used to model a 125 kV, 5.94 mm Al HVL x-ray beam produced by a fluoroscope. The model was validated through depth-dose, in-plane/cross-plane profiles and absorbed dose at 2.5-, 5.1-, 10.2- and 15.2-cm depths against the measured beam in an acrylic phantom. CT images of an anthropomorphic phantom thorax/lungs were used to simulate 0.5 Gy dose distributions for PA, AP/PA, 3-field and 4-field treatments. DVHs were generated to assess the dose to the lungs and nearby organs. Gafchromic film was used to measure doses in the phantom exposed to PA and 4-field treatments, and compared to the MC simulations.

RESULTS

Depth-dose and profile results were within 3.2% and 7.8% of the MC data uncertainty, respectively, while dose gamma analysis ranged from 0.7 to 1.0. Mean dose to the lungs were 1.1-, 0.8-, 0.9-, and 0.8- Gy for the PA, AP/PA, 3-field, and 4-field after isodose normalization to cover ∼ 95% of each lung volume. Skin dose toxicity was highest for the PA and lowest for the 4-field, and both arrangements successfully delivered the treatment on the phantom. However, the dose distribution for the PA was highly non-uniform and produced skin doses up to 4 Gy. The dose distribution for the 4-field produced a uniform 0.6 Gy dose throughout the lungs, with a maximum dose of 0.73 Gy. The average percent difference between experimental and Monte Carlo values were -0.1% (range -3% to +4%) for the PA treatment and 0.3% (range -10.3% to +15.2%) for the 4-field treatment.

CONCLUSION

A 125 kV x-ray beam from an IR fluoroscope delivered through two or more fields can deliver an effective low-dose radiotherapy treatment to the lungs. The 4-field arrangement not only provides an effective treatment, but also significant dose sparing to healthy organs, including skin, compared to the PA treatment. Use of fluoroscopy appears to be a viable alternative to megavoltage radiation therapy equipment for delivering low-dose radiotherapy to the lungs.

Patient exposure dose in interventional cardiology per clinical and technical complexity levels. Part 1: results of the VERIDIC project

BACKGROUND

Patients can be exposed to high skin doses during complex interventional cardiology (IC) procedures.

PURPOSE

To identify which clinical and technical parameters affect patient exposure and peak skin dose (PSD) and to establish dose reference levels (DRL) per clinical complexity level in IC procedures.

MATERIAL AND METHODS

Validation and Estimation of Radiation skin Dose in Interventional Cardiology (VERIDIC) project analyzed prospectively collected patient data from eight European countries and 12 hospitals where percutaneous coronary intervention (PCI), chronic total occlusion PCI (CTO), and transcatheter aortic valve implantation (TAVI) procedures were performed. A total of 62 clinical complexity parameters and 31 technical parameters were collected, univariate regressions were performed to identify those parameters affecting patient exposure and define DRL accordingly.

RESULTS

Patient exposure as well as clinical and technical parameters were collected for a total of 534 PCI, 219 CTO, and 209 TAVI. For PCI procedures, body mass index (BMI), number of stents ≥2, and total stent length >28 mm were the most prominent clinical parameters, which increased the PSD value. For CTO, these were total stent length >57 mm, BMI, and previous anterograde or retrograde technique that failed in the same session. For TAVI, these were male sex, BMI, and number of diseased vessels. DRL values for Kerma-area product (P_KA), air kerma at patient entrance reference point (K_a,r), fluoroscopy time (FT), and PSD were stratified, respectively, for 14 clinical parameters in PCI, 10 in CTO, and four in TAVI.

CONCLUSION

Prior knowledge of the key factors influencing the PSD will help optimize patient radiation protection in IC.

Radiation Exposure During Diagnostic and Therapeutic Angiography of Carotid-cavernous Fistula : A Retrospective Single Center Observational Study

Purpose

The aim of this study was to determine local diagnostic reference levels (DRLs) during endovascular diagnostics and therapy of carotid-cavernous fistulas (CCF).

Methods

In a retrospective study design, DRLs, achievable dose (AD) and mean values were assessed for all patients with CCF undergoing diagnostic angiography (I) or embolization (II). All procedures were performed with the flat-panel angiography system Allura Xper (Philips Healthcare). Interventional procedures were differentiated according to the type of CCF and the type of procedure.

Results

In total, 86 neurointerventional procedures of 48 patients with CCF were executed between February 2010 and July 2021. The following DRLs, AD and mean values could be determined: (I) DRL 215 Gy ∙ cm², AD 169 Gy ∙ cm², mean 165 Gy ∙ cm²; (II) DRL 350 Gy ∙ cm², AD 226 Gy ∙ cm², mean 266 Gy ∙ cm². Dose levels of embolization were significantly higher compared to diagnostic angiography (p < 0.001). No significant dose difference was observed with respect to the type of fistula or the embolization method.

Conclusion

This article reports on diagnostic and therapeutic DRLs in the management of CCF that could serve as a benchmark for the national radiation protection authorities. Differentiation by fistula type or embolization method does not seem to be useful.

Establishing a diagnostic reference level of radiation dose in coronary angiography and intervention: A prospective evaluation

INTRODUCTION

Invasive Coronary Angiography (CAG) leads to significant radiation exposure to the patients. Guidelines suggest that a local landmark or Diagnostic Reference Level (DRL) for these procedures should be established for every region and country. This study attempts to create a DRL for a tertiary care hospital, acting as an interim DRL for the country/region.

METHODS

Radiation exposure data for all coronary procedures done at a tertiary care hospital between October 2016 to September 2018 were collected. Data was segregated into diagnostic Coronary Angiography (CAG) and single-vessel Percutaneous Intervention (PCI). The parameters collected include dose surface product (PKA), skin surface entry dose (KAR), and fluoroscopy time (FT). The 75th percentile of the PKA was used to define the DRL.

RESULTS

500 Patients were included in the CAG group, in which the Median KAR was 412.05 mGy, Median PKA was 2635.7 μGysqm, and median FT was 2.25 min. The DRL for coronary angiography was calculated as 3695.1 μGysqm. Two hundred fifty patients were in the PCI group, the Median KAR was 1649 mGy, Median PKA was 8822.1 μGysqm, the median FT being 8.2 min. The DRL for single-vessel coronary intervention was calculated as 11038 μGysqm.

CONCLUSION

This study establishes a benchmark for radiation dose for diagnostic coronary angiography and single-vessel coronary intervention at a tertiary care hospital in NCR. It establishes an interim DRL that can be used for future studies in other institutions in the region and country and to compare with other countries.

Optimized radiological alert thresholds based on device dosimetric information and peak skin dose in vascular fluoroscopically guided intervention

OBJECTIVES

The National Council on Radiation Protection (NCRP) report no. 168 recommended that during fluoroscopically guided interventions (FGIs), each patient should be monitored when one of the following thresholds is reached: an air kerma > 5 Gy, a kerma area product (KAP) > 500 Gy.cm², a fluoroscopy time > 60 min, or a peak skin dose (PSD) > 3 Gy. Whereas PSD is the most accurate metric regarding the prevention of radiological risks, it remains the most difficult parameter to assess. We aimed to evaluate the relevance of the other, more accessible metrics and propose new optimized threshold (OT) for improved patient follow-up.

METHODS

Overall, 108 patients who underwent FGI in which at least one NCRP threshold was reached and PSD was measured were considered. The correlation between all metrics was assessed using principal component analysis (PCA). ROC curves and the sensitivity/specificity of both NCRP and OT to predict PSD > 3 Gy were evaluated.

RESULTS

The PCA shows that FGI can be decomposed with two components based on time and dose variables. Only KAP and kerma were correlated with PSD. The overall sensitivity and specificity of the new OT regarding KAP (67.6/93.0), kerma (97.3/81.7), and time (62.2/62.0) were better compared with NCRP thresholds (97.3/16.9, 40.5/95.4, and 21.6/74.7).

CONCLUSIONS

This study shows that fluoroscopy time is not a relevant metric when used to predict PSDs > 3 Gy. By adapting KAP and kerma thresholds to predict PSD over 3 Gy, patient follow-ups following vascular FGI can be improved.

KEY POINTS

• In vascular fluoroscopically guided interventions, principal component analysis demonstrates that between fluoroscopy time, KAP, and kerma, only the two last were correlated to the peak skin dose. • Optimized thresholds replacing NRCP ones obtained with ROC curves analysis were 85,451 μGy.cm², 2938 mGy, and 41 min for KAP, kerma, and fluoroscopy time respectively. • Improvements to trigger patient follow-up after vascular fluoroscopically guided interventions may be obtained by using the optimized thresholds.

Investigating the parameters that affect the radiation exposure and establishing typical values based on procedure complexity for cerebral angiography and brain aneurysm embolization

PURPOSE

The purpose of this study is to investigate the parameters that affect the radiation exposure and to establish typical values (TV) based on procedure complexity for cerebral angiography (CA) and brain aneurysm embolization (BAE).

METHODS

Clinical parameters and exposure data were retrospectively reviewed for 348 examinations performed between March 2016 and December 2019 at a single specialized neuroradiology center. TV were derived as the median value of the distribution of exposure parameters such as total air kerma area product (P_KA,T), air kerma at the patient entrance reference point, fluoroscopy time, and number of frames. A statistical analysis was conducted to investigate the exposure variability with patient's gender, number of treated vessels during CA and patient gender, aneurysm location and dimension, and treatment strategies during BAE.

RESULTS

Patient gender was associated with a significant increase in the exposure level for both CA and BAE. For CA, TV were in term of P_KA,T of 52 Gycm² for male vs. 28 Gycm² for female patients. For BAE, these were 113 Gycm² for male vs. 75 Gycm² for female patients. Exposure levels increased significantly with the number of treated vessels in CA. TV were 20 Gycm² for one vessel vs. 77 Gycm² for 5-6 vessels CA. For BAE, aneurysm location was also a key factor that affects the patient exposure. TV were 55 Gycm² for aneurysms grouped in location 1 vs. 105 Gycm² for those grouped in location 2.

CONCLUSION

Male gender, number of treated vessels, and aneurysm location are key parameters affecting patient exposure during CA and BAE procedures.

Hybridisation of perovskite nanocrystals with organic molecules for highly efficient liquid scintillators

Compared with solid scintillators, liquid scintillators have limited capability in dosimetry and radiography due to their relatively low light yields. Here, we report a new generation of highly efficient and low-cost liquid scintillators constructed by surface hybridisation of colloidal metal halide perovskite CsPbA3 (A: Cl, Br, I) nanocrystals (NCs) with organic molecules (2,5-diphenyloxazole). The hybrid liquid scintillators, compared to state-of-the-art CsI and Gd2O2S, demonstrate markedly highly competitive radioluminescence quantum yields under X-ray irradiation typically employed in diagnosis and treatment. Experimental and theoretical analyses suggest that the enhanced quantum yield is associated with X-ray photon-induced charge transfer from the organic molecules to the NCs. High-resolution X-ray imaging is demonstrated using a hybrid CsPbBr3 NC-based liquid scintillator. The novel X-ray scintillation mechanism in our hybrid scintillators could be extended to enhance the quantum yield of various types of scintillators, enabling low-dose radiation detection in various fields, including fundamental science and imaging.

Primary operator radiation dose in the cardiac catheter laboratory

OBJECTIVES

Radiation from cardiac angiography procedures is harmful to patients and the staff performing them. This study sought to investigate operator radiation dose for a range of procedures and different operators in order to investigate trends and optimise dose.

METHODS

Real-time dosemeters (RTDs) were worn by operators for angiography procedures for 3 years. Dose-area product (DAP) and RTD were collected. RTD was normalised to DAP (RTD/DAP) to compare radiation dose and radiation protection measures. Comparisons were made across procedure categories and individual operators.

RESULTS

In 7626 procedures, median and 75th percentile levels were established for operator dose for 8 procedure categories. There was a significant difference in all operator dose measures and DAP across procedure categories (p<0.001). DAP, RTD, and RTD/DAP were significantly different across 22 individual operators (p<0.001).

CONCLUSION

DAP was significantly different across procedure categories and a higher RTD was seen with higher DAP. RTD/DAP can demonstrate radiation protection effectiveness and identified differences between procedures and individual operators with this measure. Procedures and individuals were identified where further optimisation of radiation protection measures may be beneficial. A reference level for operator dose can be created and audited against on a regular basis.

ADVANCES IN KNOWLEDGE

This study demonstrates that operator dose can be easily and routinely measured on a case by case basis to investigate dose trends for different procedures. Normalising the operator dose to DAP demonstrates radiation protection effectiveness for the individual operator which can then be optimised as part of an ongoing audit program.

The role of a commercial radiation dose index monitoring system in establishing local dose reference levels for fluoroscopically guided invasive cardiac procedures

PURPOSE

The primary goal was to evaluate local dose level for fluoroscopically guided invasive cardiac procedures in a high-volume activity catheterization laboratory, using automatic data registration with minimal impact on operator workload. The secondary goal was to highlight the relationship between dose indices and acquisition parameters, in order to establish an effective strategy for protocols optimization.

METHODS

From September 2016 to December 2018, a dosimetric survey was conducted in the 2 rooms of the catheterization laboratory of our institution. Data collection burden was minimized using a commercial Radiation Dose Index Monitoring System (RDIMs) that analyzes dicom files automatically sent by the x-ray equipment. Data were combined with clinical information extracted from the HIS records reported by the interventional cardiologist. Local dose levels were established for different invasive cardiac procedures.

RESULTS

A total of 3029 procedures performed for 2615 patients were analyzed. Median KAP were 21 Gycm² for invasive coronary angiography (ICA) procedures, 61 Gycm² for percutaneous coronary intervention (PCI) procedures, 59 Gycm² for combined (ICA+PCI) procedures, 87 Gycm² for structural heart intervention (TAVI) procedures. A significant dose reduction (51% for ICA procedures and 58% for PCI procedures) was observed when noise reduction acquisition techniques were applied.

CONCLUSIONS

RDIMs are effective tools in the establishment of local dose level in interventional cardiology, as they mitigate the burden to collect and register extensive dosimetric data and exposure parameters. Systematic review of data support the multi-disciplinary team in the definition of an effective strategy for protocol management and dose optimization.

NATIONAL DIAGNOSTIC REFERENCE LEVELS IN INTERVENTIONAL RADIOLOGY SUITES IN LEBANON: A MULTICENTER SURVEY

Air kerma-area product (PKA), cumulative air kerma at patient entrance reference point, fluoroscopy time and number of images were retrospectively collected from 15 hospitals in Lebanon for 11282 fluoroscopically-guided interventional (FGI) procedures between March 2016 and November 2018. National diagnostic reference levels (NDRLs) were established based on the third quartile of the distribution of median values of exposure parameters per department for 27 types of FGI procedures. NDRLs were in line with international DRLs except for coronary angiography (CA), percutaneous coronary interventions (PCI) and transcatheter aortic valve implantation (TAVI) which require optimisation. Additionally, following the National Council on Radiation Protection and Measurements report 168, PCI, TAVI, triple chamber pacemaker implantation, endovascular aortic repair, nephrostomy, kyphoplasty and percutaneous transhepatic biliary drainage were classified as potentially high-dose procedures with >5% of the patients with PKA exceeding 300 Gycm2. The established NDRLs will promote dose optimisation and patient radiation protection.

A MULTICENTRE SURVEY OF LOCAL DIAGNOSTIC REFERENCE LEVELS AND ACHIEVABLE DOSE FOR CORONARY ANGIOGRAPHY AND PERCUTANEOUS TRANSLUMINAL CORONARY INTERVENTION PROCEDURES IN KOREA

Interventional cardiology procedures can involve relatively high radiation doses compared to general radiography. During coronary angiography (CAG) and percutaneous transluminal coronary intervention (PCI), the same area is exposed to radiation for a long period. In this study, radiation exposure data of 1071 examinations in Korean hospitals were collected, and the achievable dose (AD) and diagnostic reference levels (DRLs) in actual medical practice for two types of interventional cardiology procedures in Korea were established. In CAG, 75th percentile DRLs and AD of the total kerma-area product were 47.0 and 33.1 Gy·cm 2, respectively. In PCI, those values were 171.3 and 102.6 Gy·cm2, respectively. This is the first study to introduce the DRLs for cardiovascular interventional procedures in Korea. These results will help optimise the interventional cardiology procedures for Korean cardiac centres.

[Evaluation of the incidence of radiodermatitis lesions in interventional cardiology]

PURPOSE

The percutaneous coronary interventions use large doses of ionizing radiation, particularly when treating complex lesions. The incidence of radio-induced skin lesions is poorly known. Our goal was to evaluate the frequency of occurrence of such lesions, as well as the factors that may contribute to a high radiation dose. The recommended DAP (dose-area product) cutoff for skin monitoring after percutaneous coronary interventions is 500Gy cm².

PATIENTS AND METHOD

We prospectively studied the incidence of acute (after 5-7 days) and subacute (after 7 days to 6 months) skin lesions following angioplasty with a dose-area product (DAP) ≥200Gy cm² in patients who underwent coronary angioplasty in our center in 2013.

RESULTS

Nine hundred and thirty three consecutive procedures were analyzed, of which 102 with a DAP ≥200Gy cm². Three patients presented an acute lesion. Two of these three patients also had subacute lesions. Another patient presented only a subacute lesion. 4.82% (95% CI: [0-10]) of the patients with a DAP ≥200Gy cm² developed radiodermitis lesions, or 0.47% (95% CI: [0-0.9]) of all the patients who underwent angioplasty. The Body Mass Index and the elective (as opposed to energy) procedures were independently associated with a procedure with a DAP ≥200Gy cm².

CONCLUSION

Radiodermatitis lesions occur for 4.82% of patients benefiting from procedures with a DAP ≥200Gy cm². We suggest the establishment of a DAP threshold for dermal monitoring of patients of 200Gy cm² per procedure instead of 500Gy cm².

OCCUPATIONAL DOSE DURING ADULT INTERVENTIONAL CARDIOLOGY: FIRST VALUES WITH PERSONAL ACTIVE DOSIMETERS IN CHILE

The objective of this article is to present initial occupational dose values using digital active personal dosimeters for medical staff during adult interventional cardiology procedures in a public hospital in Chile. Personal dose equivalent Hp(10) over the lead apron of physician, nurse and radiographer were measured during 59 procedures. Mean values of occupational dose Hp(10) per procedure were 47.6, 6.2 and 4.3 μSv for physician, nurse and radiographer, respectively. If no protective tools are used, physician dose can exceed the new eye lens dose limit.

ESTIMATION OF RADIATION EXPOSURE TO THE PATIENTS IN DIAGNOSTIC AND THERAPEUTIC INTERVENTIONAL PROCEDURES

The present work reports data of the radiation exposure to the patient in various diagnostic and therapeutic interventional radiological (IR) procedures. The study includes 260 diagnostic and 195 therapeutic exposure data in 455 IR procedures. All the IR procedures were performed on a biplane angiographic machine in a tertiary care hospital. The radiation exposure was estimated from dose-area product (DAP), fluoroscopy time (FT), number of fluoroscopic runs, number of images and cumulative dose (CD) value recorded during the procedure. The data reported in the present study show significant variability in DAP values in diagnostic and therapeutic IR procedures. In diagnostic procedures, the minimum median DAP value is 8.93 Gy cm2 for upper limb angiography with mean FT of 2.7 min and maximum DAP value is 108.8 Gy cm2 for inferior vena cava angiography with mean FT of 12.55 min. For therapeutic procedures, the median value of DAP ranges from 2.43 Gy cm2 for sclerotherapy with mean FT 0.65 min to 267.23 Gy cm2 for coiling of cerebral aneurysm with mean FT of 60.52 min. The DAP value for each procedure was also correlated with FT, number of fluoroscopic runs, number of images and CD. The reported DAP values in this study are within the range of earlier published results which suggest that our finding provides at least approximate applicability to other hospitals. The third quartile DAP values of the procedures having significant number of patient data (n ≥ 10) serves as provisional reference values for the optimization of procedure protocols.

Monitoring neurointerventional radiation doses using dose-tracking software: implications for the establishment of local diagnostic reference levels

OBJECTIVES

There is potential for high radiation exposure during neurointerventional procedures. Increasing regulatory requirements mandate dose monitoring of patients and staff, and justification of high levels of radiation exposure. This paper demonstrates the potential to use radiation dose-tracking software to establish local diagnostic reference levels.

METHODS

Consecutive neurointerventional procedures, performed in a single institution within a one-year period, were retrospectively studied. Dose area product (DAP) data were collected using dose-tracking software and clinical data obtained from a prospectively generated patient treatment database.

RESULTS

Two hundred and sixty-four procedures met the selection criteria. Median DAP was 100 Gy.cm² for aneurysm coiling procedures, 259 Gy.cm² for arteriovenous malformation (AVM) embolisation procedures, 87 Gy.cm² for stroke thrombolysis/thrombectomy, and 74 Gy.cm² for four-vessel angiography. One hundred and nine aneurysm coiling procedures were further studied. Six significant variables were assessed using stepwise regression analysis to determine effect on DAP. Aneurysm location (anterior vs posterior circulation) had the single biggest effect (p = 0.004).

CONCLUSIONS

This paper confirms variable radiation exposures during neurointerventional procedures. The 75th percentile (used to define diagnostic reference levels) of DAP measurements represents a reasonable guidance metric for monitoring purposes. Results indicate that aneurysm location has the greatest impact on dose during coiling procedures and that anterior and posterior circulation coiling procedures should have separate diagnostic reference levels.

KEY POINTS

• Dose-tracking software is useful for monitoring patient radiation dose during neurointerventional procedures • This paper provides a template for methodology applicable to any interventional suite • Local diagnostic reference levels were defined by using the 75th percentile of DAP as per International Commission on Radiological Protection recommendations • Aneurysm location is the biggest determinant of radiation dose during coiling procedures. • Anterior and posterior circulation coiling procedures should have separate diagnostic reference levels.

Summary of the Italian inter-society recommendations for radiation protection optimization in interventional radiology

OBJECTIVES

A Working Group coordinated by the Italian National Institute of Health (Istituto Superiore di Sanità) and the National Workers Compensation Authority (Istituto Nazionale per l'Assicurazione contro gli Infortuni sul Lavoro, INAIL) and consisting of 11 Italian scientific/professional societies involved in the fluoroscopically guided interventional practices has been established to define recommendations for the optimization of patients and staff radiation protection in interventional radiology. A summary of these recommendations is here reported.

MATERIALS AND METHODS

A multidisciplinary approach was used to establish the Working Group by involving radiologists, interventional radiologists, neuroradiologists, interventional cardiologists, occupational health specialists, medical physicists, radiation protection experts, radiographers and nurses. The Group operated as a "Consensus Conference". Three main topics have been addressed: patient radiation protection (summarized in ten "golden rules"); staff radiation protection (summarized in ten "golden rules"); and education/training of interventional radiology professionals.

RESULTS

In the "golden rules", practical and operational recommendations were provided to help the professionals in optimizing dose delivered to patients and reducing their own exposure. Operative indications dealt also with continuing education and training, and recommendations on professional accreditation and certification.

CONCLUSIONS

The "Consensus Conference" was the methodology adopted for the development of these recommendations. Involvement of all professionals is a winning approach to improve practical implementation of the recommendations, thus getting a real impact on the optimization of the interventional radiology practices.

Optimisation of imaging protocols in interventional cardiology: impact on patient doses

The purpose of this work is to evaluate the impact of the imaging protocol as part of the optimisation of patient doses in interventional cardiology. This paper reports the results of an initial study to refine the existing fluoroscopy and cine settings, evaluates a new imaging protocol by measuring the image quality and phantom entrance air kerma values, and tests the clinical implementation of the new protocol in terms of the reduction in patient doses and the impact on clinical images. The initial study developed a new fluoroscopy mode using 7.5 frames s^-1 (instead of the previous 15 frames s^-1) with a similar dose/frame and a reduction of approximately 26% in dose/frame for the existing standard cine mode. For the new imaging protocol, the reduction in entrance air kerma was characterised for water depths of 16, 20, and 24 cm and the image quality was evaluated using a Leeds test object. A reduction in dose of around 50% was observed for the low fluoroscopy mode and an 18%-38% reduction was measured for cine. The image quality was unchanged in fluoroscopy mode and did not suffer noticeable alterations in cine mode. In the clinical implementation, cardiologists evaluated the new imaging protocol in clinical practice and cooperated with medical physicists to ensure full optimisation. The image quality criteria evaluated the ability to visualise the standard coronary arteries and small vessels (<2 mm), and the proper visualisation of the heart and diaphragm. A total of 1635 interventional cardiac procedures were assessed. The median kerma-area product exhibited a reduction of 37% for CA and 43% for PTCA examinations, and the quality of the clinical images was considered sufficient for standard clinical practice.

PATIENT DOSIMETRY DURING INTERVENTIONAL CARDIAC PROCEDURES IN A DEDICATED CATHETERIZATION LABORATORY

Cardiac interventions often result in high radiation dose to patient's skin, so a reliable indicator in terms of a commonly used dose descriptor is required to monitor skin exposures. In the present study, Gafchromic XR-RV3 film was used to measure the peak skin dose (PSD) during 40 coronary angiography (CA) and 50 percutaneous transluminal coronary angioplasty (PTCA) procedures. Corresponding values of kerma-area product (PKA), fluoroscopy time (FT) and reference air-kerma (Ka,r) were recorded and correlated with PSD. Doses to patient's eyes and thyroid were also measured by using thermoluminescent dosimeters (TLDs) during PTCA procedures. The average dose to thyroid was about six times higher than the average dose to eyes. The mean values of PSD, PKA and FT were 1140 mGy, 97 Gy cm2 and 15.7 min for PTCA and 290 mGy, 21.1 Gy cm2 and 2.4 min for CA procedures, respectively. One in seven patients of PTCA procedure received PSD >2 Gy. With respect to FT, PKA may be used as a better predictor of skin exposures because the correlation of PSD with PKA was found better than with FT for both CA and PTCA procedures.

Radiation exposure, the forgotten enemy: Toward implementation of national safety program

Radiation safety is an important counterpart in all facilities utilizing ionizing radiations. The concept of radiation safety has always been a hot topic, especially with the late reports pointing to increased hazards with chronic radiation exposure. Adopting a nationwide radiation safety program is considered one of the most urging topics, and is a conjoint responsibility of multiple disciplines within the health facility.

Evaluation of dose-area product of common radiographic examinations towards establishing a preliminary diagnostic reference levels (PDRLs) in Southwestern Nigeria

In Nigeria, a large number of radiographic examinations are conducted yearly for various diagnostic purposes. However, most examinations carried out do not have records of doses received by the patients, and the employed exposure parameters used are not documented; therefore, adequate radiation dose management is hin-dered. The aim of the present study was to estimate the dose-area product (DAP) of patients examined in Nigeria, and to propose regional reference dose levels for nine common examinations (chest PA, abdomen AP, pelvis AP, lumbar AP, skull AP, leg AP, knee AP, hand AP, and thigh AP) undertaken in Nigeria. Measurement of entrance surface dose (ESD) was carried out using thermoluminescent dosimeter (TLD). Measured ESDS were converted into DAP using the beam area of patients in 12 purposely selected hospitals. Results of the study show that the maximum/ minimum ratio ranged from 3 for thigh AP to 57 in abdomen AP. The range of determined mean and 75th percentile DAPs were 0.18-17.16, and 0.25-28.59 Gy cm2, respectively. Data available for comparison show that 75th percentile DAPs in this study (in chest PA, abdomen AP, pelvis AP, lumbar AP) are higher than NRPB-HPE reference values. The DAP in this study is higher by factor of 31.4 (chest PA), 9.9 (abdomen AP), 2.2 (pelvis AP), and 2.1 (lumbar AP) than NRPB-HPE values. The relative higher dose found in this study shows nonoptimization of practice in Nigeria. It is expected that regular dose auditing and dose optimization implementation in Nigeria would lead to lower DAP value, especially in abdomen AP. The 75th percentile DAP distribution reported in this study could be taken as regional diagnostic reference level in the Southwestern Nigeria; however, a more extensive nationwide dose survey is required to establish national reference dose.

Diagnostic reference levels and complexity indices in interventional radiology: a national programme

OBJECTIVES

To propose national diagnostic reference levels (DRLs) for interventional radiology and to evaluate the impact of the procedural complexity on patient doses.

METHODS

Eight interventional radiology units from Spanish hospitals were involved in this project. The participants agreed to undergo common quality control procedures for X-ray systems. Kerma area product (KAP) was collected from a sample of 1,649 procedures. A consensus document established the criteria to evaluate the complexity of seven types of procedures. DRLs were set as the 3rd quartile of KAP values.

RESULTS

The KAP (3rd quartile) in Gy cm² for the procedures included in the survey were: lower extremity arteriography (n = 784) 78; renal arteriography (n = 37) 107; transjugular hepatic biopsies (THB) (n = 30) 45; biliary drainage (BD) (n = 314) 30; uterine fibroid embolization (UFE) (n = 56) 214; colon endoprostheses (CE) (n = 31) 169; hepatic chemoembolization (HC) (n = 269) 303; femoropopliteal revascularization (FR) (n = 62) 119; and iliac stent (n = 66) 170. The complexity involved the increases in the following KAP factors from simple to complex procedures: THB x4; BD x13; UFE x3; CE x3; HC x5; FR x5 and IS x4.

CONCLUSIONS

The evaluation of the procedure complexity in patient doses will allow the proper use of DRLs for the optimization of interventional radiology.

KEY POINTS

• National DRLs for interventional procedures have been proposed given level of complexity • For clinical audits, the level of complexity should be taken into account. • An evaluation of the complexity levels of the procedure should be made.

Assessment of Local Dose Reference Values for Recanalization of Chronic Total Occlusions and Other Occlusions in a High-Volume Catheterization Center

The increasing number and complexity of these procedures have led to a higher number of patients at risk for tissue reactions like skin injuries. Monitoring of their dose indicators is essential in recognizing these patients. The aim of this work was to determine local diagnostic reference levels (DRLs) for recanalization of chronic total occlusion (CTO) and other occlusions procedures. All data from patients who underwent cardiac procedures were reviewed and classified according to their complexity. Dose indicators such as fluoroscopy time (FT), dose area product (DAP), and air kerma at patient entrance reference point (AKr) were recorded. Correlations with patient's body mass index, operators, procedure strategy, and complexity were studied. For CTO, the mean DAP, AKr, and FT were 252 ± 234 Gycm(2), 3,985 ± 3,579 mGy, and 47 ± 36 minutes, respectively. To better reflect the non-Gaussian distribution of data, the median and the 75th percentile values were also reported: median DAP, 172 Gycm(2); 75th percentile DAP, 350 Gycm(2); median AKr, 2,714 mGy; and 75th percentile AKr, 5,921 mGy. A tentative new set of values were suggested to take into account the complexity difference in recanalization of total occlusions according to their antegrade or retrograde approach. These approach-specific DRLs for total occlusions were mean DAP (120 ± 114 Gycm(2)), mean AKr (1,789 ± 1,933 mGy), and mean FT (22 ± 18 minutes) for antegrade approach and mean DAP (459 ± 304 Gycm(2)), mean AKr (6,881 ± 4,243 mGy), and mean FT (82 ± 40 minutes) for retrograde approach. The other significant values were median DAP (84 Gycm(2)), 75th percentile DAP (147 Gycm(2)), median AKr (1,160 mGy), and 75th percentile AKr (2,176 mGy) for antegrade approach and median DAP (422 Gycm(2)), 75th percentile DAP (552 Gycm(2)), median AKr (6,295 mGy), and 75th percentile AKr (8,064 mGy) for retrograde approach. In conclusion, a set of local DRL values from a large center were assessed. DRLs were provided for antegrade and retrograde approaches, reflecting the difference in difficulty from these 2 kinds of CTOs. The wide dose estimator values variations were explained through procedure complexity. The values obtained for the other more classic percutaneous coronary interventions were comparable with those found in the literature.

Local patient dose diagnostic reference levels in pediatric interventional cardiology in Chile using age bands and patient weight values

PURPOSE

To present the results of a patient dose evaluation program in pediatric cardiology and propose local diagnostic reference levels (DRLs) for different types of procedure and age range, in addition to suggesting approaches to correlate patient dose values with patient weight. This study was the first conducted in Latin America for pediatric interventional cardiology under the auspices of the International Atomic Energy Agency.

METHODS

Over three years, the following data regarding demographic and patient dose values were collected: age, gender, weight, height, number of cine series, total number of cine frames, fluoroscopy time (FT), and two dosimetric quantities, dose-area product (DAP) and cumulative dose (CD), at the patient entrance reference point. The third quartile values for FT, DAP, CD, number of cine series, and the DAP/body weight ratio were proposed as the set of quantities to use as local DRLs.

RESULTS

Five hundred and seventeen patients were divided into four age groups. Sample sizes by age group were 120 for <1 yr; 213 for 1 to <5 yr; 82 for 5 to <10 yr; and 102 for 10 to <16 yr. The third quartile values obtained for DAP by diagnostic and therapeutic procedures and age range were 1.17 and 1.11 Gy cm2 for <1 yr; 1.74 and 1.90 Gy cm2 for 1 to <5 yr; 2.83 and 3.22 Gy cm2 for 5 to <10 yr; and 7.34 and 8.68 Gy cm2 for 10 to <16 yr, respectively. The third quartile value obtained for the DAP/body weight ratio for the full sample of procedures was 0.17 (Gy cm2/kg) for diagnostic and therapeutic procedures.

CONCLUSIONS

The data presented in this paper are an initial attempt at establishing local DRLs in pediatric interventional cardiology, from a large sample of procedures for the standard age bands used in Europe, complemented with the values of the ratio between DAP and patient weight. This permits a rough estimate of DRLs for different patient weights and the refining of these values for the age bands when there may be large differences in child size. These DRLs were obtained at the largest pediatric hospital in Chile, with an active optimization program, and could be used by other hospitals in the Latin America region to compare their current patient dose values and determine whether corrective action is appropriate.

Measurement of maximum skin dose in interventional radiology and cardiology and challenges in the set-up of European alert thresholds

To help operators acknowledge patient dose during interventional procedures, EURADOS WG-12 focused on measuring patient skin dose using XR-RV3 gafchromic films, thermoluminescent detector (TLD) pellets or 2D TL foils and on investigating possible correlation to the on-line dose indicators such as fluoroscopy time, Kerma-area product (KAP) and cumulative air Kerma at reference point (CK). The study aims at defining non-centre-specific European alert thresholds for skin dose in three interventional procedures: chemoembolization of the liver (CE), neuroembolization (NE) and percutaneous coronary interventions (PCI). Skin dose values of >3 Gy (ICRP threshold for skin injuries) were indeed measured in these procedures confirming the need for dose indicators that correlate with maximum skin dose (MSD). However, although MSD showed fairly good correlation with KAP and CK, several limitations were identified challenging the set-up of non-centre-specific European alert thresholds. This paper presents preliminary results of this wide European measurement campaign and focuses on the main challenges in the definition of European alert thresholds.

Clinical apparatus for the reduction of dose area product for patients undergoing x-ray catheterization

PURPOSE

The authors describe a design for prepatient region of interest attenuators (ROIAs) to reduce dose area product (DAP) for clinical use. The authors describe a model to predict DAP values from x-ray technique parameters recorded during a clinical procedure for image sequences obtained in the presence or absence of ROIAs. The model was developed primarily to determine what the DAP to a patient undergoing cardiac catheterization with a ROIA would have been if no ROIA had been used allowing a determination of DAP reduction.

METHODS

Copper ROIAs with thicknesses that vary gradually so as not to cause significant image artifacts were constructed. X-ray image sequences were acquired on a clinical catheterization system with and without ROIAs with varying x-ray technique parameters. DAP values were measured for all said exposures using an ionization chamber and compared to a model the authors developed.

RESULTS

The model can predict DAP values within 3.5% on average with or without ROIAs when compared to ionization chamber measurements.

CONCLUSIONS

The proposed experimental design is adequate for measuring DAP reductions on the order of 1.5-3.5 that are expected when introducing a ROIA during patient catheterization imaging.

Patient skin dose measurements using a cable free system MOSFETs based in fluoroscopically guided percutaneous vertebroplasty, percutaneous disc decompression, radiofrequency medial branch neurolysis, and endovascular critical limb ischemia

The purpose of this work has been to dosimetrically investigate four fluoroscopically guided interventions: the percutaneous vertebroplasty (PVP), the percutaneous disc decompression (PDD), the radiofrequency medial branch neurolysis (RF) (hereafter named spine procedures), and the endovascular treatment for the critical limb ischemia (CLI). The X-ray equipment used was a Philips Integris Allura Xper FD20 imaging system provided with a dose-area product (DAP) meter. The parameters investigated were: maximum skin dose (MSD), air kerma (Ka,r), DAP, and fluoroscopy time (FT). In order to measure the maximum skin dose, we employed a system based on MOSFET detectors. Before using the system on patients, a calibration factor Fc and correction factors for energy (CkV) and field size (CFD) dependence were determined. Ka,r, DAP, and FT were extrapolated from the X-ray equipment. The analysis was carried out on 40 patients, 10 for each procedure. The average fluoroscopy time and DAP values were compared with the reference levels (RLs) proposed in literature. Finally, the correlations between MSD, FT, Ka,r, and DAP values, as well as between DAP and FT values, were studied in terms of Pearson's product-moment coefficients for spine procedures only. An Fc value of 0.20 and a very low dependence of CFD on field size were found. A third-order polynomial function was chosen for CkV. The mean values of MSD ranged from 2.3 to 10.8cGy for CLI and PVP, respectively. For these procedures, the DAP and FT values were within the proposed RL values. The statistical analysis showed little correlation between the investigated parameters. The interventional procedures investigated were found to be both safe with regard to deterministic effects and optimized for stochastic ones. In the spine procedures, the observed correlations indicated that the estimation of MSD from Ka,r or DAP was not accurate and a direct measure of MSD is therefore recommended.

C-arm rotation as a method for reducing peak skin dose in interventional cardiology

PURPOSE

Prolonged interventional cardiology (IC) procedures may result in radiation-induced skin injury, a potentially preventable cause of patient morbidity. Rotating the C-arm during an IC procedure may reduce this risk, although the methods by which the technique can be practically applied remains unexplored. A previous study demonstrated that C-arm rotation often increases peak skin dose (PSD) in interventional radiology procedures. The purpose of this study was to determine whether C-arm rotation reduces the PSD in IC procedures and, if so, under what circumstances.

MATERIALS AND METHODS

Simulations were performed using a numerical ray-tracing algorithm to analyse the effect of C-arm rotation on PSD across a range of patient sizes, C-arm configurations and procedure types. Specific data from modern fluoroscopes and patient dimensions were used as inputs to the simulations.

RESULTS

In many cases, modest C-arm rotation angles completely eliminated overlap between X-ray field sites on the skin. When overlap remained, PSD increases were generally small. One exception was craniocaudal rotation, which tended to increase PSD. C-arm rotation was most effective for large patients and small X-ray field sizes. Small patients may not benefit from C-arm rotation as a procedural modification. The use of a prophylactic method where the C-arm was rotated between small opposing oblique angles was effective in reducing PSD.

CONCLUSIONS

With the exception of rotation to steep craniocaudal angles, rotating the C-arm reduces PSD in IC procedures when used as either a procedural modification or a prophylactic strategy. Tight collimation increases the benefit of C-arm rotation.

Radiation dose in coronary angiography and intervention: initial results from the establishment of a multi-centre diagnostic reference level in Queensland public hospitals

Introduction

Radiation dose to patients undergoing invasive coronary angiography (ICA) is relatively high. Guidelines suggest that a local benchmark or diagnostic reference level (DRL) be established for these procedures. This study sought to create a DRL for ICA procedures in Queensland public hospitals.

Methods

Data were collected for all Cardiac Catheter Laboratories in Queensland public hospitals. Data were collected for diagnostic coronary angiography (CA) and single-vessel percutaneous intervention (PCI) procedures. Dose area product (P_KA), skin surface entrance dose (K_AR), fluoroscopy time (FT), and patient height and weight were collected for 3 months. The DRL was set from the 75th percentile of the P_KA.

Results

2590 patients were included in the CA group where the median FT was 3.5 min (inter-quartile range = 2.3–6.1). Median K_AR = 581 mGy (374–876). Median P_KA = 3908 uGym² (2489–5865) DRL = 5865 uGym². 947 patients were included in the PCI group where median FT was 11.2 min (7.7–17.4). Median K_AR = 1501 mGy (928–2224). Median P_KA = 8736 uGym² (5449–12,900) DRL = 12,900 uGym².

Conclusion

This study established a benchmark for radiation dose for diagnostic and interventional coronary angiography in Queensland public facilities.

[Diagnostic reference levels in interventional radiology]

This article discusses the diagnostic reference levels for radiation exposure proposed by the International Commission on Radiological Protection (ICRP) to facilitate the application of the optimization criteria in diagnostic imaging and interventional procedures. These levels are normally established as the third quartile of the dose distributions to patients in an ample sample of centers and are supposed to be representative of good practice regarding patient exposure. In determining these levels, it is important to evaluate image quality as well to ensure that it is sufficient for diagnostic purposes. When the values for the dose received by patients are systematically higher or much lower than the reference levels, an investigation should determine whether corrective measures need to be applied. The European and Spanish regulations require the use of these reference values in quality assurance programs. For interventional procedures, the dose area product (or kerma area product) values are usually used as reference values together with the time under fluoroscopy and the total number of images acquired. The most modern imaging devices allow the value of the accumulated dose at the entrance to the patient to be calculated to optimize the distribution of the dose on the skin. The ICRP recommends that the complexity of interventional procedures be taken into account when establishing reference levels. In the future, diagnostic imaging departments will have automatic systems to manage patient dosimetric data; these systems will enable continuous dosage auditing and alerts about individual procedures that might involve doses several times above the reference values. This article also discusses aspects that need to be clarified to take better advantage of the reference levels in interventional procedures.

Optimisation of coronary angiography exposures requires a multifactorial approach and careful procedural definition

OBJECTIVE

This study investigates the factors associated with higher doses for both single-plane and biplane procedures and establishes centre-specific 75th percentile levels.

METHODS

602 patients undergoing coronary angiography in a large hospital at Sydney were recruited to the study, and causal agents for high radiation doses were investigated: gender, procedural complexity, severity of coronary artery disease, presence of coronary bypass grafts, entry approach (radial or femoral), level of operator experience; and a single-plane or a biplane imaging system was employed.

RESULTS

The 75th percentile levels were calculated. The results demonstrated that, for both systems, higher exposures were associated with patients who were male (p<0.001), had coronary vessel disease (p<0.001) and had a history of coronary bypass grafts (p<0.001). In addition, for biplane systems, procedural complexity (p<0.001), types of entry approach (p<0.001) and levels of operator experience (p<0.001) significantly impacted upon the dose. Biplane examinations recorded higher doses than single-plane procedures (p<0.001) and the inclusion of left-sided ventriculography contributed to the overall dose by up to 10%.

CONCLUSION

The 75th percentile levels in this study represent the tentative reference levels and are 48.9, 44.2 and 56 Gy cm(2) for all exposures, single-plane- and biplane-specific exposures, respectively, and compare favourably with the diagnostic reference level values established elsewhere internationally, with only the UK and Irish data being lower.

ADVANCES IN KNOWLEDGE

Specific agents have been identified for dose-reducing strategies and the importance of operator training is highlighted. The assumption that biplane procedures may reduce the patient dose should be treated with caution.

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.

ICRP PUBLICATION 120: Radiological protection in cardiology

Cardiac nuclear medicine, cardiac computed tomography (CT), interventional cardiology procedures, and electrophysiology procedures are increasing in number and account for an important share of patient radiation exposure in medicine. Complex percutaneous coronary interventions and cardiac electrophysiology procedures are associated with high radiation doses. These procedures can result in patient skin doses that are high enough to cause radiation injury and an increased risk of cancer. Treatment of congenital heart disease in children is of particular concern. Additionally, staff(1) in cardiac catheterisation laboratories may receive high doses of radiation if radiological protection tools are not used properly. The Commission provided recommendations for radiological protection during fluoroscopically guided interventions in Publication 85, for radiological protection in CT in Publications 87 and 102, and for training in radiological protection in Publication 113 (ICRP, 2000b,c, 2007a, 2009). This report is focused specifically on cardiology, and brings together information relevant to cardiology from the Commission's published documents. There is emphasis on those imaging procedures and interventions specific to cardiology. The material and recommendations in the current document have been updated to reflect the most recent recommendations of the Commission. This report provides guidance to assist the cardiologist with justification procedures and optimisation of protection in cardiac CT studies, cardiac nuclear medicine studies, and fluoroscopically guided cardiac interventions. It includes discussions of the biological effects of radiation, principles of radiological protection, protection of staff during fluoroscopically guided interventions, radiological protection training, and establishment of a quality assurance programme for cardiac imaging and intervention. As tissue injury, principally skin injury, is a risk for fluoroscopically guided interventions, particular attention is devoted to clinical examples of radiation-related skin injuries from cardiac interventions, methods to reduce patient radiation dose, training recommendations, and quality assurance programmes for interventional fluoroscopy.

Patient radiation doses in interventional cardiology in the U.S.: advisory data sets and possible initial values for U.S. reference levels

PURPOSE

To determine patient radiation doses from interventional cardiology procedures in the U.S and to suggest possible initial values for U.S. benchmarks for patient radiation dose from selected interventional cardiology procedures [fluoroscopically guided diagnostic cardiac catheterization and percutaneous coronary intervention (PCI)].

METHODS

Patient radiation dose metrics were derived from analysis of data from the 2008 to 2009 Nationwide Evaluation of X-ray Trends (NEXT) survey of cardiac catheterization. This analysis used identified data and did not require review by an IRB. Data from 171 facilities in 30 states were analyzed. The distributions (percentiles) of radiation dose metrics were determined for diagnostic cardiac catheterizations, PCI, and combined diagnostic and PCI procedures. Confidence intervals for these dose distributions were determined using bootstrap resampling.

RESULTS

Percentile distributions (advisory data sets) and possible preliminary U.S. reference levels (based on the 75th percentile of the dose distributions) are provided for cumulative air kerma at the reference point (K(a,r)), cumulative air kerma-area product (P(KA)), fluoroscopy time, and number of cine runs. Dose distributions are sufficiently detailed to permit dose audits as described in National Council on Radiation Protection and Measurements Report No. 168. Fluoroscopy times are consistent with those observed in European studies, but P(KA) is higher in the U.S.

CONCLUSIONS

Sufficient data exist to suggest possible initial benchmarks for patient radiation dose for certain interventional cardiology procedures in the U.S. Our data suggest that patient radiation dose in these procedures is not optimized in U.S. practice.

Swiss population exposure to radiation by interventional radiology in 2008

The aim of this study was to investigate the radiation exposure of the Swiss population to interventional procedures. A nationwide survey was conducted in Switzerland. The annual effective dose per capita due to interventional procedures was found to be 0.14 mSv, corresponding to 12% of the total dose. Coronary angiography and percutaneous coronary interventions were found to be the most frequent and the most irradiating interventional procedures, accounting for 52% of the total examination frequency and 64% of the dose delivered to the population. Switzerland stands at the same level as other countries in terms of effective dose per capita due to interventional radiology.

Survey of the interventional cardiology procedures in Italy

Interventional cardiology procedures are increasing because they offer many advantages to patients compared with other techniques: therefore the Italian National Institution for Insurance against Accidents at Work decided to start a survey for monitoring the state-of-the-art regarding the professionals involved in those procedures. The survey covered six cardiology and medical physics Italian departments. Each centre was asked to record 10 examinations for five types of procedures: coronary angiography (CA), electrophysiology studies (ES), pacemaker implantation (PI), percutaneous transluminal coronary angioplasty (PTCA) and radiofrequency catheter ablation (RA). For each examination all the centres were requested to fill in a questionnaire containing information regarding the operator performing the examination, the patient and the procedure. A total of 290 examinations were recorded: 103 CA, 14 ES, 68 PI, 79 PTCA and 26 RA. As occupational doses are strongly related to patient doses, both patients and operators radiation dose data are reported. Ratios of maximum to minimum mean patient doses across the hospitals surveyed were 2.0, 3.9, 7.0, 1.8 and 1.4 for CA, ES, PI, PTCA and RA, respectively. The calculated rounded mean dose-area product values across all participating hospitals were comparable with other values reported in the literature. In general, specific radiation protection tools were used by all operators performing different procedures in all hospitals. A major issue in this survey was the absence of information about correlation between staff and patient doses in a single procedure: future studies could be more aimed to prospective goals where occupational exposures per procedure are monitored specifically.