Comparison of Patient Skin Dose Evaluated Using Radiochromic Film and Dose Calculation Software

Establishment of Diagnostic Reference Levels in Portuguese Interventional Radiology departments

PURPOSE

To establish Portuguese Diagnostic Reference Levels (DRLs), for six body fluoroscopy guided interventional procedures (FGIP).

METHOD

A retrospective study was conducted in five interventional departments most representative of Interventional Radiology (IR) practice. Dose values, in terms of air kerma area product (PKA in Gy.cm2), air kerma at the patient entrance reference point (Ka,r in mGy), and exposure parameters (fluoroscopy time (FT) and number of cine runs) were collected. Examinations were selected per procedure (at least 20), according to the antero-posterior and lateral diameter mean value (±5 cm), measured on previous Computed Tomography (CT) examinations.

RESULTS

Data of 489 body FGIP show a large variation on dose values per procedure and per department. National DRLs in terms of PKA were 20.2 Gy.cm2 for Percutaneous transhepatic biliary drainage (PTBD), 98.2 Gy.cm2 for Bronchial artery embolisation (BAE), 247.7 Gy.cm2 for Transarterial chemoembolisation (TACE), 331.6 Gy.cm2 for Inferior epigastric arteries embolisation (IEAE), 312.0 Gy.cm2 for Transjugular intrahepatic portosystemic shunt (TIPS) and 19.3 Gy.cm2 for Endovascular treatment of femoral popliteal arteries (ETFPA).

CONCLUSIONS

This is the first study reporting Interventional Radiology DRLs in Portugal and we propose preliminary national estimates for the six more common body FGIP. The results of this study will be presented and discussed with all Portuguese IR departments, to promote procedures optimisation.

Optimized radiological alert thresholds based on device-dosimetric information to predict peak skin dose between 2 and 4 Gy during vascular fluoroscopically guided intervention

OBJECTIVES

To provide radiologists and physicists with methodological tools to improve patient management after vascular fluoroscopically guided intervention (FGI) by providing optimized thresholds (OT) values that could be used as a surrogate to the thresholds classically proposed by the National Council on Radiation Protection (NCRP) or could be useful to adapt their own substantial radiation dose levels (SRDL) values.

METHODS

PSD of 2000-4000 mGy after FGI were calculated for 258 patients with dedicated software. Overall, the kerma and KAP 3D-ROC curves were used to assess the sensitivity (SEN) and specificity (SPE) of NCRP thresholds and OT for each PSD. Kiviat diagram and density curves were plotted for the best SEN/SPE pair of 3D-ROC curves and compared to the NCRP thresholds.

RESULTS

OT for both kerma and KAP generating the best SEN/SPE couple for PSD of 2000-4000 mGy were obtained. The SEN/SPE couple of each OT was always better than that obtained using NCRP ones. The best OT among all those calculated providing the highest SEN/SPE values for kerma (3020.5 mGy) and KAP (741.02 Gy.cm2) were obtained when PSD was equal to 3300 mGy.

CONCLUSIONS

We have calculated OT in terms of kerma and KAP based on 3D-ROC curves analysis and peak skin dose calculations that can be obtained to better predict high skin dose. The use of OT that predicted PSD greater than 3000 mGy is likely to improve patient follow-up. The methodology developed in this work could be adapted to other institutions in order to better define their own SRDL.

KEY POINTS

• Optimized dose thresholds in terms of kerma and KAP based on 3D-ROC curves analysis and peak skin dose calculations between 2000 and 4000 mGy can be obtained to better predict high skin dose. • Patients receiving a peak skin dose between 2000 and 4000 mGy have their follow-up enhanced by using the optimized thresholds instead of the NCRP thresholds. • The best-optimized thresholds, corresponding to 3020.5 mGy and 741.02 Gy.cm2 for kerma and KAP respectively can be used instead of NRCP ones to trigger patient follow-up after fluoroscopically guided vascular interventions.

UNCERTAINTY ASSOCIATED WITH THE USE OF SOFTWARE SOLUTIONS UTILIZING DICOM RDSR FOR SKIN DOSE ASSESSMENT IN INTERVENTIONAL RADIOLOGY AND CARDIOLOGY

PURPOSE

The purpose of this work is to provide a comprehensive analysis of uncertainties associated with the use of software solutions utilizing DICOM RDSRs for skin dose assessment in the interventional fluoroscopic environment.

METHODS AND RESULTS

Three different scenarios have been defined for determining the overall uncertainty, each with a specific assumption on the maximum deviations of factors affecting the calculated dose. Relative expanded uncertainty has been calculated using two approaches: the law of propagation of uncertainty and the propagation of distributions based on the Monte Carlo method. According to the propagation of uncertainty, it is estimated that the lowest possible relative expanded uncertainty of ~13% (at the 95% level of confidence, i.e. with the coverage factor of k = 2 assuming normal distribution) could only be achieved if all sources of uncertainties are carefully controlled, whereas maximum relative expanded uncertainty could reach up to 61% if none of the influencing parameters are controlled properly. When the influencing parameters are reasonably well-controlled, realistic relative expanded uncertainty amounts to 28%. Values for the relative expanded uncertainty obtained from the Monte Carlo propagation of distributions concur with the results obtained from the propagation of uncertainty to within 3% in all three considered scenarios, validating the assumption of normality.

CONCLUSIONS

The overall skin dose relative uncertainty has been found to range from 13 to 61%, emphasizing the importance of adequate analysis and control of all relevant uncertainty sources.

Biodosimetry in interventional radiology: cutaneous-based immunoassay for anticipating risks of dermatitis

OBJECTIVES

Interventional radiology procedures expose individuals to ionizing radiation. However, existing dosimetry methods do not provide the dose effectively absorbed to the skin, and do not consider the patient's individual response to irradiation. To resolve this lack of dosimetry data, we developed a new external irradiation biodosimetry device, DosiKit, based on the dose-dependent relationship between irradiation dose and radiation-induced H2AX protein phosphorylation in hair follicles. This new biological method was tested in Clermont-Ferrand University Hospital to evaluate the assay performances in the medical field and to estimate DosiKit sensitivity threshold.

METHODS

DosiKit was tested over 95 patients treated with neuroradiological interventions. For each intervention, lithium fluoride thermoluminescent dosimeters (TLD) were used to measure total dose received at each hair collection point (lateral and occipital skull areas), and conventional indirect dosimetry parameters were collected with a Dosimetry Archiving and Communication System (DACS).

RESULTS

Quantitative measurement of radiation-induced H2AX protein phosphorylation was performed on 174 hair samples before and after the radiation exposure and 105 samples showed a notable induction of gammaH2AX protein after the radiological procedure. According to a statistical analysis, the threshold sensitivity of the DosiKit immunoassay was estimated around 700 mGy.

CONCLUSIONS

With this study, we showed that DosiKit provides a useful way for mapping the actually absorbed doses, allowing to identify patients overexposed in interventional radiology procedures, and thus for anticipating risk of developing dermatitis.

KEY POINTS

• DosiKit is a new external irradiation biodosimetry device, based on the dose-dependent relationship between irradiation dose and radiation-induced H2AX protein phosphorylation in hair follicles. • DosiKit was tested over 95 patients treated with neuroradiological interventions. • The threshold sensitivity of the DosiKit immunoassay was estimated around 700 mGy and DosiKit provides a useful way for mapping the actually absorbed doses.

Accuracy of skin dose mapping in interventional cardiology: Comparison of 10 software products following a common protocol

PURPOSE

Online and offline software products can estimate the maximum skin dose (MSD) delivered to the patient during interventional cardiology procedures. The capabilities and accuracy of several skin dose mapping (SDM) software products were assessed on X-ray systems from the main manufacturers following a common protocol.

METHODS

Skin dose was measured on four X-ray systems following a protocol composed of nine fundamental irradiation set-ups and three set-ups simulating short, clinical procedures. Dosimeters/multimeters with semiconductor-based detectors, radiochromic films and thermoluminescent dosimeters were used. Results were compared with up to eight of 10 SDM products, depending on their compatibility.

RESULTS

The MSD estimates generally agreed with the measurements within ± 40% for fundamental irradiation set-ups and simulated procedures. Only three SDM products provided estimates within ± 40% for all tested configurations on at least one compatible X-ray system. No SDM product provided estimates within ± 40% for all combinations of configurations and compatible systems. The accuracy of the MSD estimate for lateral irradiations was variable and could be poor (up to 66% underestimation). Most SDM products produced maps which qualitatively represented the dimensions, the shape and the relative position of the MSD region. Some products, however, missed the MSD region when situated at the intersection of multiple fields, which is of radiation protection concern.

CONCLUSIONS

It is very challenging to establish a common protocol for quality control (QC) and acceptance testing because not all information necessary for accurate MSD calculation is available or standardised in the radiation dose structured reports (RDSRs).

Validation of the MC-GPU Monte Carlo code against the PENELOPE/penEasy code system and benchmarking against experimental conditions for typical radiation qualities and setups in interventional radiology and cardiology

INTRODUCTION

Interventional procedures are associated with potentially high radiation doses to the skin. The 2013/59/EURATOM Directive establishes that the equipment used for interventional radiology must have a device or a feature informing the practitioner of relevant parameters for assessing patient dose at the end of the procedure. Monte Carlo codes of radiation transport are considered to be one of the most reliable tools available to assess doses. However, they are usually too time consuming for use in clinical practice. This work presents the validation of the fast Monte Carlo code MC-GPU for application in interventional radiology.

METHODOLOGIES

MC-GPU calculations were compared against the well-validated Monte Carlo simulation code PENELOPE/penEasy by simulating the organ dose distribution in a voxelized anthropomorphic phantom. In a second phase, the code was compared against thermoluminescent measurements performed on slab phantoms, both in a calibration laboratory and at a hospital.

RESULTS

The results obtained from the two simulation codes show very good agreement, differences in the output were within 1%, whereas the calculation time on the MC-GPU was 2500 times shorter. Comparison with measurements is of the order of 10%, within the associated uncertainty.

CONCLUSIONS

It has been verified that MC-GPU provides good estimates of the dose when compared to PENELOPE program. It is also shown that it presents very good performance when assessing organ doses in very short times, less than one minute, in real clinical set-ups. Future steps would be to simulate complex procedures with several projections.

Vendor-independent skin dose mapping application for interventional radiology and cardiology

PURPOSE

The purpose of this paper is to present and validate an originally developed application SkinCare used for skin dose mapping in interventional procedures, which are associated with relatively high radiation doses to the patient's skin and possible skin reactions.

METHODS

SkinCare is an application tool for generating skin dose maps following interventional radiology and cardiology procedures using the realistic 3D patient models. Skin dose is calculated using data from Digital Imaging and Communications in Medicine (DICOM) Radiation Dose Structured Reports (RDSRs). SkinCare validation was performed by using the data from the Siemens Artis Zee Biplane fluoroscopy system and conducting "Acceptance and quality control protocols for skin dose calculating software solutions in interventional cardiology" developed and tested in the frame of the VERIDIC project. XR-RV3 Gafchromic films were used as dosimeters to compare peak skin doses (PSDs) and dose maps obtained through measurements and calculations. DICOM RDSRs from four fluoroscopy systems of different vendors (Canon, GE, Philips, and Siemens) were used for the development of the SkinCare and for the comparison of skin dose maps generated using SkinCare to skin dose maps generated by different commercial software tools (Dose Tracking System (DTS) from Canon, RadimetricsTM from Bayer and RDM from MEDSQUARE). The same RDSRs generated during a cardiology clinical procedure (percutaneous coronary intervention-PCI) were used for comparison.

RESULTS

Validation performed using VERIDIC's protocols for skin dose calculation software showed that PSD calculated by SkinCare is within 17% and 16% accuracy compared to measurements using XR-RV3 Gafchromic films for fundamental irradiation setups and simplified clinical procedures, respectively. Good visual agreement between dose maps generated by SkinCare and DTS, RadimetricsTM and RDM was obtained.

CONCLUSIONS

SkinCare is proved to be very convenient solution that can be used for monitoring delivered dose following interventional procedures.

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.

BENCHMARKING THE DOSE MAP SOFTWARE FOR CLINICAL IMPLEMENTATION AND ESTABLISHMENT OF A LOCAL FOLLOW-UP PROTOCOL FOR THE MANAGEMENT OF SKIN INJURES FOLLOWING COMPLEX INTERVENTIONAL CARDIOLOGY PROCEDURES

This paper aims to validate the accuracy of the peak skin dose (Dskin,max) computed by the Dose Map software (DMS)-general electric and establish a local follow-up protocol for the management of patient skin injuries following complex interventional cardiology procedures (ICPs). Dskin,max was computed by the DMS and was simultaneously measured by a dense mesh of 72 thermoluminescent dosemeters for 20 ICP. Measured and computed Dskin,max were compared using Lin's concordance coefficient (${\rho}_c$). The implementation of a local follow-up strategy was based on a computed Dskin,max of 2 Gy. After eliminating 2 outliers, the average deviation between the two methods was 6% (range: -36 to +40%). Concordance between the two methods was moderate with ${\rho}_c$ (confidence interval) of 0.9128 (0.8541-0.9486). DMS computes Dskin,max with an acceptable accuracy and can be used to setup an individual follow-up process for patients with high skin exposure and risks.

Radiation Dose of Patients in Fluoroscopically Guided Interventions: an Update

The benefits of fluoroscopically guided interventional procedures are significant and have established new standards in the clinical management of many diseases. Despite the benefits, it is known that they come with known risks, such as the exposure to ionizing radiation. To minimize such risks, it is crucial that the health professionals involved in the procedures have a common understanding of the concepts related to radiation protection, such as dose descriptors, diagnostic reference levels and typical dose values. An update about these concepts will be presented with the objective to raise awareness amongst health professionals and contribute to the increase in knowledge, skills and competences in radiation protection in fluoroscopically guided interventional procedures.

Unintended and Accidental Exposures, Significant Dose Events and Trigger Levels in Interventional Radiology

Over recent years, an increasing number of fluoroscopically guided interventions (FGIs) have been performed by radiologists and non-radiologists. Also, the number of complex interventional procedures has increased. In the late nineties, first reports of skin injuries appeared in the literature. The medical community responded through increased awareness for radiation protection and public authorities by recommendations and legislation, for example, the European Basic Safety Standards (EU-BSS) which were published in 2014, or the international Basic Safety Standards (BSS). Implementation of the EU-BSS requires concerted action from interventionalists, radiographers, medical physics experts and competent national authorities. Interventionalists should play an important role in this project since implementation of the EU-BSS will affect their daily practice. This paper discusses some important issues of the EU-BSS such as unintended and accidental radiation exposures of patients, the meaning of significant dose events and how to deal with patients who were exposed to a substantial radiation dose with the risk of tissue injuries. In addition, this paper provides practical advice on how to implement alert and trigger levels in daily practice of FGIs in order to increase patient safety.

Incidence of Chronic Radiodermatitis after Fluoroscopically Guided Interventions: A Retrospective Study

PURPOSE

To assess the incidence and risk factors for chronic radiodermatitis after fluoroscopically guided interventions (FGIs) in high-risk patients.

MATERIALS AND METHODS

Between 2010 and 2016, of 55,782 patients who underwent FGIs, 359 had a risk procedure for skin injury (maximal skin dose > 3 Gy, air kerma > 5 Gy, dose area product [DAP] > 500 Gy.cm², or fluoroscopy time > 60 minutes). Ninety-one of these patients were examined by a dermatologist for radiodermatitis (median time after procedure, 31.2 months [95% confidence interval, 14.2-50.7]). In each case, the clinical features and topography of the skin lesions were recorded and their incidence calculated. The characteristics of the patients and of the FGIs were tested as risk factors.

RESULTS

Eight patients (8.8%) had chronic radiodermatitis; 19 (20.9%) had acute radiodermatitis. Body mass index, DAP value, and air kerma were the only risk factors identified.

CONCLUSIONS

This study shows that chronic radiodermatitis may be considered a frequent side effect in an at-risk population. The lesions are commonly benign, but extensive sclerosis can occur. Patients should be better informed about the side effects and offered a skin exam periodically.