Skin dose alarm levels in cardiac angiography procedures: is a single DAP value sufficient?

Evaluation of a Low-Dose Radiation Protocol During Transcatheter Aortic Valve Implantation

We aimed to evaluate the efficacy and safety of a low-dose imaging protocol to reduce intraprocedural radiation during transcatheter aortic valve implantation (TAVI). Observational analysis: 802 transfemoral TAVI patients receiving balloon-expandable devices ≥23 mm at a high-volume centre. After propensity score matching, a standard-dose group (SD, n = 333) treated between January 2014 and February 2016 was compared with a low-dose group (LD, n = 333) treated between August 2017 and March 2019 after departmental uptake of a low-dose imaging protocol (reduced field size, high table height, use of "fluoro save," 3.75 frames/second acquisition, increased filtering). Primary end point was dose-area product (DAP). Secondary safety end points were VARC-2 device success and a composite of in-hospital complications. The LD protocol was associated with lower DAP (4.64 [2.93, 8.42] vs 22.73 [12.31, 34.58] Gy⋅cm², p <0.001) and fluoroscopy time (10.4 [8.1, 13.9] vs 11.5 [9.1, 15.3] minutes, p = 0.001). Contrast use was higher in the LD group (LD 110 [94, 130] vs SD 100 [80, 135] milliliters, p = 0.042). Device success (LD 88.3% vs SD 91.3%, p = 0.25), and the composite end point (LD 8.1% vs SD 11.4%, p = 0.19) were similar. In multivariate analysis, the low-dose protocol was associated with a 19.8 Gy⋅cm² reduction in procedural DAP (p <0.001). In conclusion, compared with standard imaging, a low-dose protocol for TAVI significantly reduced radiation dose without compromising outcomes.

Practical Dose Parameter Values for the Prediction of the Adverse Effect of Neurointerventional Radiation: Relationship Between the Dose Parameters and Temporary Alopecia After Intracranial Coil Embolization

OBJECTIVE

To present values for the dose parameters predictive of alopecia as an adverse effect induced by neuroembolization using a biplane fluoroscopy.

METHODS

This study included a total of 151 patients (52 men, mean age of 55.1 ± 12.2 years) treated for intracranial neuroembolization between 2014 to 2018 with the following criteria: 1) obtainable dose report with digital subtraction angiographic image records, 2) no history of radiation exposure 6 months prior to the first procedure, and 3) and clinical follow-up performed through 12 months following the procedure. Patients were divided into 2 groups according to their presentation of alopecia during the follow-up period.

RESULTS

Eighteen (11.9%) patients developed alopecia 10 to 30 days after the procedure (average: 18.5 ± 5.3 days). Sixteen (88.9%) patients in the alopecia group were affected by projection of the A-plane fluoroscopy. Area under the receiver operating characteristic analysis curves of 0.865 (P = 0.000) and 0.831 (P = 0.000) were used to compute the optimal A-plane dose area product (255.4 Gy-cm²; sensitivity: 0.875; specificity: 0.805; Youden J = 0.682) and cumulative dose (4437.5 mGy; sensitivity, 0.750; specificity, 0.805; Youden J = 0.556) cutoff values, respectively, capable of distinguishing patients with alopecia (n = 16) from subtotal patients (n = 149).

CONCLUSIONS

The dose area product and the cumulative dose may be useful, intuitive factors for predicting the adverse effects of the neurointerventional radiation. Further multicenter research should be performed to confirm the efficacy and utility of the reference values of dose area product and cumulative dose for preventing excessive irradiation during neurointerventional procedures.

Proposal of a new method to prove that unnecessary information is not drawn on the image using statistical analysis

The purpose of this study is to propose a new method of image evaluation using statistical analysis. We used the Sign test and the Wilcoxon test to analyze the statistical significance of image differences. Using this method, we evaluated whether the small electrode of the DAP meter appears in the X-ray image. Two observed values, which were obtained by averaging all values under all exposure conditions, were compared. All the observation tests showed the same sign. Thus, the results proved that the small electrode of the DAP meter is not present on the image. Using this method, it became possible to prove that the electrode was not depicted, which was impossible to determine using conventional methods. The method combining both the Sign test and the Wilcoxon test can be useful in image evaluation.

SKIN DOSE, EFFECTIVE DOSE AND RELATED RISK IN TRANSCATHETER AORTIC VALVE IMPLANTATION (TAVI) PROCEDURES: IS THE CANCER RISK ACCEPTABLE FOR YOUNGER PATIENTS?

The aim of this study was to estimate conversion coefficients for maximum entrance skin dose (MESD) and effective dose (E) for patients undergoing transcatheter aortic valve implantation (TAVI) and to evaluate the risk of exposure-induced cancer death (REID) for prospectively younger patients. Effective doses and risks were estimated for 22 patients using PCXMC whereas MESDs were estimated for a sub-group of 15 patients using Gafchromic film. The estimated conversion coefficients for skin dose [CCS = MESD/dose-area product (DAP)] and E (CCE = E/DAP) were 9.7±1.5 and 0.24±0.02 mSv/Gy cm(2), respectively. The REID ranged from 1:9900 to 1:1400 and by decreasing the age of examination to 40-50 y of age, the REID increased with a factor of 2 for females and 1.5 for males. The organ at risk was the lung. Currently, the patient population is elderly with radiation-induced skin injuries as the main risk. The risk of cancer induction should additionally be considered if younger patient populations are to be treated.

Factors Affecting Radiation Exposure during Lumbar Epidural Steroid Injection: A Prospective Study in 759 Patients

OBJECTIVE

To estimate and compare radiation exposure and intervention time during lumbar epidural steroid injection (ESI) 1) under different practitioners and methods with continuous fluoroscopic monitoring, and 2) under one practitioner with different methods and monitoring.

MATERIALS AND METHODS

We consecutively recruited 804 patients who underwent lumbar ESI and 759 patients who underwent 922 interventions were included for analysis in this investigation. Three different practitioners (a senior faculty member, junior faculty member, trainee) performed lumbar ESI using different methods (caudal, interlaminar, transforaminal). The senior faculty member performed lumbar ESI under two different methods of fluoroscopic monitoring (continuous [CM] and intermittent monitoring [IM]). The dose area product (DAP) fluoroscopy time, and intervention time during lumbar ESI were compared for 1) ESI methods and practitioners under CM, and 2) ESI methods and monitoring.

RESULTS

With CM, interaction between the effects of the practitioner and the intervention on DAP was significant (p < 0.001), but not fluoroscopy time (p = 0.672) or intervention time (p = 0.852). The significant main effects included the practitioner and intervention on DAP, fluoroscopy time, and intervention time with CM (p < 0.001). DAPs and fluoroscopy time for caudal, interlaminar, and transforaminal ESI were higher with CM than with IM (p < 0.001). Intervention time did not differ between CM and IM.

CONCLUSION

Radiation exposure is dependent on the practitioners and methods and within the established safety limits during lumbar ESIs under CM. With an experienced practitioner, IM leads to less radiation exposure than CM.

An Evaluation of the Organ Dose Received by Cardiologists Arising From Angiography Examinations in Educational Hospital in Rasht

Interventional procedures, cine acquisitions and operation of fluoroscopic equipment in high-dose fluoroscopic modes, involve long fluoroscopic times which can lead to high staff doses. Also, Coronary angiography (CA) procedures require the cardiologist and assisting personnel to remain close to the patient, which is the main source of scattered radiation. Thus, radiation exposure is a significant concern for radiation workers and it is important to measure the radiation doses received by personnel and evaluate the parameters concerning total radiation burden. In this research, we investigated radiation doses to 10 cardiologists performing 120 CA procedures. Using thermo luminescent dosimeters doses to the wrists, thyroid and eyes per procedure were measured. Based on the measured dose values, maximum doses to the Left wrist, Right wrist, thyroid and eyes of cardiologist were measured 241.45 µSv, 203.17 µSv, 78.21 µSv and 44.58 µSv, respectively. The results of this study indicate that distance from the source, use of protective equipment's, procedure complexity, equipment performance, and cardiologist experience are the principal exposure-determining variables. It can be conclude that if adequate radiation protection approaches have been implemented, occupational dose levels to cardiologists would be within the regulated acceptable dose limits.

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.

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.

Use of GAFCHROMIC XR type R films for skin-dose measurements in interventional radiology: Validation of a dosimetric procedure on a sample of patients undergone interventional cardiology

The Gafchromic XR type R film is a suitable dosimeter to determine the map of the skin dose in patients undergone complex interventional radiological procedures, such as cardiology ones. The need of preventing or locating possible skin injuries due to high doses administered to patients-as recommended by international organizations-wants the introduction in patient dosimetry of a dosimeter easy to handle, with low dependence of the response on energy in the typical radiological range, and extended measurable dose range. XR type R films fulfil all these requirements and moreover may be quickly analyzed by cheap commercial scanners. In order to determine skin-dose values by XR-R, a film calibration curve is required. In this work, validation of the XR-R dosimetry has been performed for the determination of the skin dose: maximum skin-dose values in 14 patients undergone radiofrequency ablation and pacemaker implant procedures have been determined by XR-R calibrated films. A comparison between skin-dose values determined by XR-R films and retrospective ionometric measurements has pointed out some discrepancies in the results, due to difficulties in retrospectively reproducing the real procedure settings, where XR-R film dosimetry is related to the specific patient procedure, even, in very complex interventional settings.

Patient doses in interventional cardiology procedures in Sudan

Radiation doses delivered to 461 patients were measured during the period of 12 months in a hospital in Khartoum, Sudan. Kerma Area Product, Cumulative Kerma and fluoroscopy time were registered during four selected procedures, namely coronary angiography (CA), percutaneous transluminal coronary angioplasty (PTCA), percutaneous transvenous mitral commissurotomy (PTMC) and pacemaker. For CA, PTCA, PTMC and pacemaker the mean and median kerma area product values in gray centimeter square were found to be (20, 17.9), (56.5, 50.3), (21.6, 19.6) and (15.3, 9.6), respectively. The obtained results for mean and median cumulative kerma in milli gray were (143.7, 120.5), (418.4, 371.4), (119.8, 102) and (88.7, 59.8) as measured for CA, PTCA, PTMC and pacemaker, respectively. The mean and median total fluoroscopy time in minutes were (5.2, 3.39), (17.6, 14.8), (18, 15) and (10.2, 7.16) as registered for CA, PTCA, PTMA and pacemaker, respectively. Maximum skin dose was estimated for 13 patients during PTCA and CA procedures. Dose exceeded 2 Gy in PTCA for one patient. In comparison with the guidelines for coronary examinations suggested by SENTINEL Consortium, a higher fluoroscopy time for PTCA procedure is reported in this study. It is realised that proper selection of irradiation area, technique modes, fluoroscopy time and conducting special training on radiation protection to the operators are the main factors for potential optimisation.

Status of radiation protection in interventional cardiology in four East European countries

Level of staff and patient radiation protection in interventional cardiology in four counties (Bosnia and Herzegovina, Croatia, Montenegro and Serbia) as a part of International Atomic Energy Agency project (RER/9/093) are presented. Patient doses were assessed in terms of air kerma area product (KAP), peak skin dose (PSD) or air kerma at interventional reference point (K(IRP)). Results were available from nine hospitals: 775 patients for KAP, 157 for PSD and 437 for K(IRP). Eight centres reported KAP >100 Gy cm(2) and five centres reported values >200 Gy cm(2). From patients monitored in terms of PSD, 14 (9 %) had PSD >2 Gy and 6 (3 %) patients from those monitored in terms of K(IRP) had value >5 Gy, indicating risk of skin injury. The results indicate need for optimisation and dose monitoring in complex fluoroscopically guided cardiology interventions.

A study of the relationship between peak skin dose and cumulative air kerma in interventional neuroradiology and cardiology

A study of peak skin doses (PSDs) during neuroradiology and cardiology interventional procedures has been carried out using Gafchromic XR-RV2 film. Use of mosaics made from squares held in cling film has allowed doses to the head to be mapped successfully. The displayed cumulative air kerma (CAK) has been calibrated in terms of cumulative entrance surface dose (CESD) and results indicate that this can provide a reliable indicator of the PSD in neuroradiology. Results linking PSD to CESD for interventional cardiology were variable, but CAK is still considered to provide the best option for use as an indicator of potential radiation-induced effects. A CESD exceeding 3 Gy is considered a suitable action level for triggering follow-up of patients in neuroradiology and cardiology for possible skin effects. Application of dose action levels defined in this way would affect 8% of neurological embolisation procedures and 5% of cardiology ablation and multiple stent procedures at the hospitals where the investigations were carried out. A close relationship was observed between CESD and dose-area product (DAP) for particular types of procedure, and DAPs of 200-300  Gy cm(2) could be used as trigger levels where CAK readings were not available. The DAP value would depend on the mean field size and would need to be determined for each application.

Evaluation of two-dimensional bolus effect of immobilization/support devices on skin doses: a radiochromic EBT film dosimetry study in phantom

PURPOSE

In this study, the authors have quantified the two-dimensional (2D) perspective of skin dose increase using EBT film dosimetry in phantom in the presence of patient immobilization devices during conventional and IMRT treatments.

METHODS

For 6 MV conventional photon field, the authors evaluated and quantified the 2D bolus effect on skin doses for six different common patient immobilization/support devices, including carbon fiber grid with Mylar sheet, Orfit carbon fiber base plate, balsa wood board, Styrofoam, perforated AquaPlast sheet, and alpha-cradle. For 6 and 15 MV IMRT fields, a stack of two film layers positioned above a solid phantom was exposed at the air interface or in the presence of a patient alpha-cradle. All the films were scanned and the pixel values were converted to doses based on an established calibration curve. The authors determined the 2D skin dose distributions, isodose curves, and cross-sectional profiles at the surface layers with or without the immobilization/support device. The authors also generated and compared the dose area histograms (DAHs) and dose area products from the 2D skin dose distributions.

RESULTS

In contrast with 20% relative dose [(RD) dose relative to dmax on central axis] at 0.0153 cm in the film layer for 6 MV 10 x 10 cm2 open field, the average RDs at the same depth in the film layer were 71%, 69%, 55%, and 57% for Orfit, balsa wood, Styrofoam, and alpha-cradle, respectively. At the same depth, the RDs were 54% under a strut and 26% between neighboring struts of a carbon fiber grid with Mylar sheet, and between 34% and 56% for stretched perforated AquaPlast sheet. In the presence of the alpha-cradle for the 6 MV (15 MV) IMRT fields, the hot spot doses at the effective measurement depths of 0.0153 and 0.0459 cm were 140% and 150%, (83% and 89%), respectively, of the isocenter dose. The enhancement factor was defined as the ratio of a given DAH parameter (minimum dose received in a given area) with and without the support device. For 6 MV conventional 10 x 10 cm2 field, the enhancement factor was the highest (3.4) for the Orfit carbon fiber plate. As for the IMRT field, the enhancement factors varied with the size of the area of interest and were as high as 3.8 (4.3) at the hot spot of 5 cm2 area in the top film layer (0.0153 cm) for 6 MV (15 MV) beams.

CONCLUSIONS

Significant 2D bolus effect on skin dose in the presence of patient support and immobilization devices was confirmed and quantified with EBT film dosimetry. Furthermore, the EBT film has potential application for in vivo monitoring of the 2D skin dose distributions during patient treatments.

A large-scale multicentre study of patient skin doses in interventional cardiology: dose-area product action levels and dose reference levels

For 318 patients in 8 different Belgian hospitals, the entire skin-dose distribution was mapped using a grid of 70 thermoluminescence dosimeters per patient, allowing an accurate determination of the maximum skin dose (MSD). Dose-area product (DAP) values, exposure parameters and geometry, together with procedure, patient and cardiologist characteristics, were also registered. Procedures were divided into two groups: diagnostic procedures (coronary angiography) and therapeutic procedures (dilatation, stent, combined procedures (e.g. coronary angiography + dilatation + stent)). The mean value of the MSD was 0.310 Gy for diagnostic and 0.699 Gy for therapeutic procedures. The most critical projection for receiving the MSD is the LAO90 (left anterior oblique) geometry. In 3% of cases, the MSD exceeded the 2 Gy dose threshold for deterministic effects. Action levels in terms of DAP values as the basis for a strategy for follow-up of patients for deterministic radiation skin effects were derived from measured MSD and cumulative DAP values. Two DAP action levels are proposed. A first DAP action level of 125 Gy cm(2) corresponding to the dose threshold of 2 Gy would imply an optional radiopathological follow-up depending on the cardiologist's decision. A second DAP action level of 250 Gy cm(2) corresponding to the 3 Gy skin dose would imply a systematic follow-up. Dose reference levels - 71.3 Gy cm(2) for diagnostic and 106.0 Gy cm(2) for therapeutic procedures - were derived from the 75 percentile of the DAP distributions. As a conclusion, we propose that total DAP is registered in patient's record file, as it can serve to improve the follow-up of patients for radiation-induced skin injuries.

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.

A study on patients' radiation doses from interventional cardiac procedures in Tabriz, Iran

Interventional cardiac procedures produce a large amount of X-ray exposures to the patients in comparison with other conventional X-ray imaging procedures. In the current study, the exposure parameters of 580 patients referred to a cardiac angiography department were recorded. The mean values of total kerma-area product (KAP) were 18.6 Gy cm2 for coronary angiography (CA) and 55 Gy cm2 for percutaneous transluminal coronary angioplasty (PTCA). The mean fluoroscopy time was 3.2 and 11.6 min, respectively, for CA and PTCA. The patients' exposure parameters during electrophysiological studies were 15.5 min for mean fluoroscopy time and 33.9 Gy cm2 for total KAP. For paediatrics, the mean fluoroscopy time of 5.4 min and total KAP of 2 Gy cm2 were recorded. Comparing the proposed reference values, the authors think that the exposure level of patients in their department is at an acceptable level.

Correlation of patient maximum skin doses in cardiac procedures with various dose indicators

In most countries of European Union, legislation requires the determination of the total skin dose received by patients during interventional procedures in order to prevent deterministic damages. Various dose indicators like dose-area product (DAP), cumulative dose (CD) and entrance dose at the patient plane (EFD) are used for patient dosimetry purposes in clinical practice. This study aimed at relating those dose indicators with doses ascribed to the most irradiated areas of the patient skin usually expressed in terms of local maximal skin dose (MSD). The study was performed in two different facilities for two most common cardiac procedures coronary angiography (CA) and percutaneous coronary interventions (PCI). For CA procedures, the registered values of fluoroscopy time, total DAP and MSD were in the range (0.7-27.3) min, (16-317) Gy cm(2) and (43-1507) mGy, respectively, and for interventions, accordingly (2.1-43.6) min, (17-425) Gy cm(2), (71-1555) mGy. Moreover, for CA procedures, CD and EFD were in the ranges (295-4689) mGy and (121-1768) mGy and for PCI (267-6524) mGy and (68-2279) mGy, respectively. No general and satisfactory correlation was found for safe estimation of MSD. However, results show that the best dose indicator which might serve for rough, preliminary estimation is DAP value. In the study, the appropriate trigger levels were proposed for both facilities.

Effective doses in radiology and diagnostic nuclear medicine: a catalog

Medical uses of radiation have grown very rapidly over the past decade, and, as of 2007, medical uses represent the largest source of exposure to the U.S. population. Most physicians have difficulty assessing the magnitude of exposure or potential risk. Effective dose provides an approximate indicator of potential detriment from ionizing radiation and should be used as one parameter in evaluating the appropriateness of examinations involving ionizing radiation. The purpose of this review is to provide a compilation of effective doses for radiologic and nuclear medicine procedures. Standard radiographic examinations have average effective doses that vary by over a factor of 1000 (0.01-10 mSv). Computed tomographic examinations tend to be in a more narrow range but have relatively high average effective doses (approximately 2-20 mSv), and average effective doses for interventional procedures usually range from 5-70 mSv. Average effective dose for most nuclear medicine procedures varies between 0.3 and 20 mSv. These doses can be compared with the average annual effective dose from background radiation of about 3 mSv.

How to set up and apply reference levels in fluoroscopy at a national level

A nationwide survey was launched to investigate the use of fluoroscopy and establish national reference levels (RL) for dose-intensive procedures. The 2-year investigation covered five radiology and nine cardiology departments in public hospitals and private clinics, and focused on 12 examination types: 6 diagnostic and 6 interventional. A total of 1,000 examinations was registered. Information including the fluoroscopy time (T), the number of frames (N) and the dose-area product (DAP) was provided. The data set was used to establish the distributions of T, N and the DAP and the associated RL values. The examinations were pooled to improve the statistics. A wide variation in dose and image quality in fixed geometry was observed. As an example, the skin dose rate for abdominal examinations varied in the range of 10 to 45 mGy/min for comparable image quality. A wide variability was found for several types of examinations, mainly complex ones. DAP RLs of 210, 125, 80, 240, 440 and 110 Gy cm2 were established for lower limb and iliac angiography, cerebral angiography, coronary angiography, biliary drainage and stenting, cerebral embolization and PTCA, respectively. The RL values established are compared to the data published in the literature.