Interventional Reference Point Research Articles

Quantitative Digital Subtraction Angiography Measurement of Arterial Velocity at Low Radiation Dose Rates.

Quantitative digital subtraction angiography (qDSA) has been proposed to quantify blood velocity for monitoring treatment progress during blood flow altering interventions. The method requires high frame rate imaging [~ 30 frame per second (fps)] to capture temporal dynamics. This work investigates performance of qDSA in low radiation dose acquisitions to facilitate clinical translation. Velocity quantification accuracy was evaluated at five radiation dose rates in vitro and in vivo. Angiographic technique ranged from 30 fps digital subtraction angiography ( at the interventional reference point) down to a 30 fps protocol at 23% higher radiation dose per frame than fluoroscopy ( ). The in vitro setup consisted of a 3D-printed model of a swine hepatic arterial tree connected to a pulsatile displacement pump. Five different flow rates (3.5-8.8mL/s) were investigated in vitro. Angiography-based fluid velocity measurements were compared across dose rates using ANOVA and Bland-Altman analysis. The experiment was then repeated in a swine study (n = 4). Radiation dose rate reductions for the lowest dose protocol were 99% and 96% for the phantom and swine study, respectively. No significant difference was found between angiography-based velocity measurements at different dose rates in vitro or in vivo. Bland-Altman analysis found little bias for all lower-dose protocols (range: [- 0.1, 0.1]cm/s), with the widest limits of agreement ([- 3.3, 3.5]cm/s) occurring at the lowest dose protocol. This study demonstrates the feasibility of quantitative blood velocity measurements from angiographic images acquired at reduced radiation dose rates.

Interleaved x-ray imaging: A method for simultaneous acquisition of quantitative and diagnostic digital subtraction angiography.

Flow altering angiographic procedures suffer from ill-defined, qualitative endpoints. Quantitative digital subtraction angiography (qDSA) is an emerging technology that aims to address this issue by providing intra-procedural blood velocity measurements from time-resolved, 2D angiograms. To date, qDSA has used 30 frame/s DSA imaging, which is associated with high radiation dose rate compared to clinical diagnostic DSA (up to 4 frame/s). The purpose of this study is to demonstrate an interleaved x-ray imaging method which decreases the radiation dose rate associated with high frame rate qDSA while simultaneously providing low frame rate diagnostic DSA images, enabling the acquisition of both datasets in a single image sequence with a single injection of contrast agent. Interleaved x-ray imaging combines low radiation dose image frames acquired at a high rate with high radiation dose image frames acquired at a low rate. The feasibility of this approach was evaluated on an x-ray system equipped with research prototype software for x-ray tube control. qDSA blood velocity quantification was evaluated in a flow phantom study for two lower dose interleaving protocols (LD1: and LD2: ) and one conventional (full dose) protocol ( . Dose was measured at the interventional reference point. Fluid velocities ranging from 24 to 45cm/s were investigated. Gold standard velocities were measured using an ultrasound flow probe. Linear regression and Bland-Altman analysis were used to compare ultrasound and qDSA. The LD1 and LD2 interleaved protocols resulted in dose rate reductions of -67.7% and -85.5%, compared to the full dose qDSA scan. For the full dose protocol, the Bland-Altman limits of agreement (LOA) between qDSA and ultrasound velocities were [0.7, 6.7] cm/s with a mean difference of 3.7cm/s. The LD1 interleaved protocol results were similar (LOA: [0.3, 6.9] cm/s, bias: 3.6cm/s). The LD2 interleaved protocol resulted in slightly larger LOA: [-2.5, 5.5] cm/s with a decrease in the bias: 1.5cm/s. Linear regression analysis showed a strong correlation between ultrasound and qDSA derived velocities using the LD1 protocol, with a of , a slope of and an offset of cm/s. Similar values were also found for the LD2 protocol, with a of , a slope of and an offset of cm/s. The interleaved method enables simultaneous acquisition of low-dose high-rate images for intra-procedural blood velocity quantification (qDSA) and high-dose low-rate images for vessel morphology evaluation (diagnostic DSA).

Spatiotemporal frequency domain analysis for blood velocity measurement during embolization procedures.

Currently, determining procedural endpoints and treatment efficacy of vascular interventions is largely qualitative and relies on subjective visual assessment of digital subtraction angiography (DSA) images leading to large interobserver variabilities and poor reproducibility. Quantitative metrics such as the residual blood velocity in embolized vessel branches could help establish objective and reproducible endpoints. Recently, velocity quantification techniques based on a contrast enhanced X-ray sequence such as qDSA and 4D DSA have been proposed. These techniques must be robust, and, to avoid radiation dose concerns, they should be compatible with low dose per frame imageacquisition. To develop and evaluate a technique for robust blood velocity quantification from low dose contrast enhanced X-ray image sequences that leverages the oscillating signal created by pulsatile bloodflow. The proposed spatiotemporal frequency domain (STF) approach quantifies velocities from time attenuation maps (TAMs) representing the oscillating signal over time for all points along a vessel centerline. Due to the time it takes a contrast bolus to travel along the vessel centerline, the resulting TAM resembles a sheared sine wave. The shear angle is related to the velocity and can be determined in the spatiotemporal frequency domain after applying the 2D Fourier transform to the TAM. The approach was evaluated in a straight tube phantom using three different radiation dose levels and compared to ultrasound transit-time-based measurements. The STF velocity results were also compared to previously published approaches for the measurement of blood velocity from contrast enhanced X-ray sequences including shifted least squared (SLS) and phase shift (PHS). Additionally, an in vivo porcine study (n = 8) was performed where increasing amounts of embolic particles were injected into a hepatic or splenic artery with intermittent velocity measurements after each injection to monitor the resulting reduction invelocity. At the lowest evaluated dose level (average air kerma rate 1.3 mGy/s at the interventional reference point), the Pearson correlation between ultrasound and STF velocity measurements was . This was significantly higher ( ) than corresponding correlation results between ultrasound and the previously published SLS and PHS approaches ( and , respectively). In the in vivo study, a reduction in velocity was observed in of cases after injection of 1 mL, after 3 mL, and after 4 mL of embolicparticles. The results show good agreement of the spatiotemporal frequency domain approach with ultrasound even in low dose per frame image sequences. Additionally, the in vivo study demonstrates the ability to monitor the physiological changes due to embolization. This could provide quantitative metrics during vascular procedures to establish objective and reproducibleendpoints.

Patient skin dose measurement and risk of deterministic effect during fluoroscopy cardiac procedures.

This study aimed at assessing patient's peak skin doses (PSD) during fluoroscopy cardiac procedures and proposed a look up table to enhance patient's dose management. Perspex phantom and thermoluminescent dosemeters (TLD) were irradiated for different dose levels with X-ray equipment (Philips Azurion 7). It was found that PSD measures were higher than the kerma at the interventional reference point [K (IRP)] reported with factors 1.55, 1.75 and 2.88 for anterior posterior (AP0o), left anterior oblique (LAO45o) and right anterior oblique (RAO45o), respectively. The equations describing the correlation between the PSD measured kerma area product and cumulative air kerma were found with R-square values of 0.98 and 0.99, respectively. The statistical analysis shows a strong linear correlation between PSD and K (IRP) (P-value=0.05). It was also found that 27% of the patients population considered in this work, received a skin dose higher than the threshold of deterministic effect of 2Gy and a look up table with the equation of fitness were proposed to be implemented in the facility for K (IRP) higher than 500mGy.

Application of reference air kerma alert levels for pediatric fluoroscopic examinations.

The purpose of this study was to provide an empirical model to develop reference air kerma (RAK) alert levels as a function of patient thickness or age for pediatric fluoroscopy for any institution to use in a Quality Assurance program. RAK and patient thickness were collected for 10&663 general fluoroscopic examinations and 1500 fluoroscopically guided interventions (FGIs). RAK and patient age were collected for 6137 fluoroscopic examinations with mobile‐C‐arms (MC). Coefficients of linear regression fits of logarithmic RAK as a function of patient thickness or age were generated for each fluoroscopy group. Regression fits of RAK for 50%, 90%, and 98% upper prediction levels were used as inputs to derive an empirical formula to estimate alert levels as a function of patient thickness. A methodology is presented to scale results from this study for any patient thickness or age for any institution, for example, the patient thickness dependent RAK alert level at the top 1% of expected RAK can be set using the 98% upper prediction interval boundary given by: RAK98%=em.xavg+s98.c^, where x avg is the institute's average patient thickness or age, and c^ is the intercept based on the average RAK of the patient population calculated as c^=ln(RAKavg)−m.xavg.RAKavg is the institution's average RAK (mGy). m and s 98 are constants presented for each type of fluoroscope and RAK group and represent slope of the fit and scale factor, respectively. An empirical equation, which estimates alert levels expressed as air Kerma without backscatter at the interventional reference point as a function of patient thickness or age is provided for each fluoroscopic examination type. The empirical equations allow any facility with limited data to scale the results of this study's single facility data to model their practice's unique RAK alert levels and patient population demographics to establish pediatric alert levels for fluoroscopic procedures.

Tantalum-specific contrast-to-noise ratio or conventional detector dose-driven exposure control in angiography: radiation dose and image quality evaluation in a porcine model

BackgroundThe aim of this animal study was to compare the fluoroscopic image quality (IQ) and radiation dose between a tantalum (Ta)-specific contrast-to-noise ratio-driven exposure control (Ta-CEC) and a detector dose-driven exposure control (DEC) in abdominal angiography.MethodsNine angiography scenarios were created in seven anaesthetised pigs using Ta-based embolisation material during percutaneous liver and kidney intervention. Fluoroscopic images were acquired using three DEC protocols with different dose levels and Ta-CEC protocols with different IQ levels, sampled in small steps. Polymethyl-methacrylate and aluminium plates were used to simulate attenuation of three water equivalent thicknesses (WET). Three blinded readers evaluated the IQ of DEC and dose equivalent Ta images and selected the Ta-IQ equivalent image corresponding to the DEC image.ResultsInterobserver agreement for the IQ assessment was 0.43 for DEC, 0.56 for Ta-CEC and for the assessment of incident air kerma at the interventional reference point (Ka,r) for the Ta-IQ equivalent image 0.73. The average IQ of the dose equivalent Ta images was superior compared to the DEC images (p < 0.001) and also for every WET (26, 31, or 36 cm) and dose level (p ≤ 0.022). The average Ka,r for the Ta-IQ equivalent images was 59 ± 16% (mean ± standard deviation) lower compared to the DEC images (p < 0.001).ConclusionsCompared to DEC, Ta-CEC significantly improved the fluoroscopic depiction of Ta, while maintaining the Ka,r. Alternatively, the Ka,r can be significantly reduced by using Ta-CEC instead of DEC, while maintaining equivalent IQ.

Radiation dose and diagnostic reference levels for four interventional radiology procedures: results of the prospective European multicenter survey EUCLID.

To assess information reflecting radiation dose and define diagnostic reference levels (DRL) on a European basis for four interventional radiology (IR) procedures considering clinical indication, anatomical region, and procedure. A prospective European study was performed to provide data on the IR procedures percutaneous recanalization of iliac arteries, percutaneous recanalization of femoropopliteal arteries, transarterial chemoembolization of hepatocellular carcinoma, and percutaneous transhepatic biliary drainage. Hospitals were asked to complete a questionnaire giving information on procedure, equipment, and protocol. Patient size and weight, experience of the operator graded in number of procedures performed, and complexity level of each procedure were reported. Sixteen hospitals from 13 countries could be surveyed. The percentiles of the kerma-area product, fluoroscopy time, cumulative air kerma at the interventional reference point, and number of images were determined. The impact of equipment, year of installation, and complexity level of the procedure on dose were analyzed. DRLs based on clinical indication were defined. Dose values varied considerably within hospitals, between them, and within each subgroup of complexity level. The use of state-of-the-art equipment reduced dose significantly by 52%. Although dose also varied within each subgroup of complexity level, for transarterial chemoembolization of hepatocellular carcinoma and percutaneous transhepatic biliary drainage, dose significantly correlated with complexity. This was the first study reporting exposure practice and defining DRLs based on clinical indication for four IR procedures on a European basis. These DRLs can serve as a baseline for comparison with local practice, the study as a guideline for future surveys. • The use of state-of-the-art angiographic equipment reduces dose significantly. • A significant correlation between radiation dose and complexity level is found. • Dose values vary considerably, both within and between individual hospitals, and within each complexity level of interventional radiology procedure.

EVALUATION OF THE RADIATION DOSE TO THE HANDS OF ORTHOPAEDIC SURGEONS DURING FLUOROSCOPY USING STORED IMAGES.

Data were collected from 642 orthopaedic interventions during which the images produced by X-rays were recorded. By examining these images, it is possible to determine the time that the orthopaedic surgeons' hands were exposed to the direct radiation beam. The procedures with greater exposure to the direct beam were those involving the hand (median 15s) and the wrist (median 13s). Two surgeons wore a ring to measure the absorbed dose at the fingers: one on the dominant hand and the other on the non-dominant hand. The two surgeons performed 34 and 48 operations, respectively, in 14months. The total doses measured with the rings were 2.30 and 1.04mSv, respectively. The images of the interventions were examined, determining how much each individual hand was exposed. The interventional reference point (IRPeff (left or right)) was calculated by comparing the doses at the IRP with the exposure times of the right or the left hand. Summing the IRPeff of the two surgeons in 14months, it is obtained the maximum values of 2.87mGy for the left hand of one and 6.74mGy for the right hand of the other, which are of the order of 1/100 of the annual dose limit for the extremities.

Examination of Effectiveness Verification and Additional Items in Angiography and IVR of DRLs 2015

Japanese Diagnostic Reference Levels (DRLs) were released as "Japan DRLs 2015" from Japan Network for Research and Information on Medical Exposure (J-RIME) in June 2015. In "Japan DRLs 2015", DRLs in angiography and interventional procedures are set at a fluoroscopic dose rate of 20 mGy/min at the interventional reference point using a phantom. In order to achieve optimization with DRLs, then it need to be revised regularly. Therefore, we (research group to examine the effect of Japan DRLs 2015 and the necessity of additional items in angiography and vascular interventions) examined the effects of "Japan DRLs 2015" on angiography and interventional procedures. And we also investigated for DRLs revision in the future. As a result, it turned out that it is important to create DRLs in medical procedures that can be effectively used in clinical settings.

Physics-driven learning of x-ray skin dose distribution in interventional procedures.

Radiation doses accumulated during very complicated image-guided x-ray procedures have the potential to cause stochastic, but also deterministic effects, such as skin rashes or even hair loss. To monitor and reduce radiation-related risks to patients' skin, x-ray imaging devices are equipped with online air kerma monitoring components. Traditionally, such measurements have been used to estimate skin entrance dose by (a) estimating air kerma at the interventional reference point (IRP), (b) forward projecting the dose distribution, and (c) considering a backscatter factor among other correction factors. Unfortunately, the complicated interaction between incident x-ray photons, secondary electrons, and skin tissue cannot be properly accounted for by assuming a linear relationship between forward projected air kerma and a backscatter factor. Gold standard skin dose models are therefore determined using Monte Carlo (MC) techniques. However, MC simulations are computationally complex in general and possible acceleration mainly depends on the employed hardware and variance reduction techniques. To obtain reliable and fast dose estimates, we propose to combine MC-based simulations with learning-based methods. The basic idea of our method is to approximate the radiation physics to calculate a first-order exposure estimate quickly. This initial estimate is then refined using prior knowledge derived from MC simulations. To this end, the primary photon propagation inside a voxelized patient model is estimated using a less accurate but fast photon ray casting (RC) simulation based on the Beer-Lambert law. The results of the RC simulation are then fed into a convolutional neural network (CNN), which maps the propagation of primary photons to the dose deposition inside the patient model. Additionally, the patient model itself including anatomy and material properties, such as mass density and mass energy-absorption coefficients, are fed into the CNN as well. The CNN is trained using smoothed results of MC simulations as output and RC simulations of identical imaging settings and patient models as input. In total, 163 MC and associated RC simulations are carried out for the head, thorax, abdomen, and pelvis in three different voxel phantoms. We used or primarily emitted photons sampled from a 125kV peak voltage spectrum, respectively. Edge-preserving smoothing (EPS) is applied to reduce (a) general stochastic uncertainties and (b) stochastic uncertainty concerning MC simulations of less primary photons. The CNN is trained using seven imaging settings of the abdomen in a single phantom. Testing its performance on the remaining datasets, the CNN is capable of estimating skin dose with an error of below 10% for the majority of test cases. The combination of deep neural networks and MC simulation of particle physics has the potential to decrease the computational complexity of accurate skin dose estimation. The proposed approach can provide dose distributions in under one second when running on high-end hardware. On lower cost hardware, it took up to 2min to arrive at the same result. This makes our approach applicable in high-end environments as well as in budget solutions. Furthermore, the number of primary photons only affects the training time, while the execution time is independent of the number of primary photons.

Retrospective study of patients radiation dose during cardiac catheterization procedures.

Cardiac catheterization procedures provide tremendous benefits to modern healthcare and the benefit derived by the patient should far outweigh the radiation risk associated with a properly optimized procedure. With increasing utilization of such procedures, there is growing concern regarding the magnitude and variations of dose to patients associated with procedure complexity and techniques parameters. Therefore, this study investigated radiation dose to patients from six cardiac catheterization procedures at our facility and suggest possible initial dose values for benchmark for patient radiation dose from these procedures. This initial benchmark data will be used for clinical radiation dose management which is essential for assessing the impact of any quality improvement initiatives in the cardiac catheterization laboratory. We retrospectively analyzed the dose parameters of 1000 patients who underwent various cardiac catheterization procedures: left heart catheterization (LH), percutaneous coronary intervention (PCI), complex PCI, LH with complex PCI, LH with PCI and cardiac resynchronization therapy (CRT) pacemaker in our cardiac catheterization laboratories. Patient's clinical radiation dose data [kerma-area-product (KAP) and air-kerma at the interventional reference point (Ka,r)] and technique parameters (fluoroscopy time, tube potential, current, pulse width and number of cine images) along with demographic information (age, height and weight) were collected from the hospital's RIS (Synapse), Sensis/Syngo Dynamics and Siemens Sensis Stats Manager electronic database. Statistical analysis was performed with the IBM SPSS Modeler v. 18.1 software. The overall patient median age was 67.0 (range: 26.0-97.0) years and the median body mass index (BMI) was 28.8 (range: 15.9-61.7) kg/m2 . The median KAP for the LH, PCI, LH with complex PCI, complex PCI, LH with PCI and CRT-pacemaker procedures are 44.4 (4.1-203.2), 80.2 (18.9-208.5), 83.7 (48.0-246.1), 113.8 (60.9-284.5), 91.7 (6.0-426.0) and 51.1 (7.0-175.9) Gy-cm2 . The median Ka,r for the LH, PCI, LH with complex PCI, complex PCI, LH with PCI and CRT-pacemaker procedures are 701.0 (35.3-3794.0), 1384.7 (291.7-4021.8), 1607.0 (883.5-4448.3), 2260.2 (867.4-5311.9), 1589.3 (100.2-7237.4) and 463.8 (67.7-1695.9) mGy respectively. We have analyzed patient radiation doses from six commonly used procedures in our cardiac catheterization laboratories and suggested possible initial values for benchmark from these procedures for the fluoroscopy time, KAP and air-kerma at the interventional reference point based on our current practices. Our data compare well with published values reported in the literature by investigators who have also studied patient doses and established benchmark dose levels for their facilities. Procedure-specific benchmark dose data for various groups of patients can provide the motivation for monitoring practices to promote improvements in patient radiation dose optimization in the cardiac catheterization laboratories. We have investigated local patients' radiation doses and established benchmark radiation data which are essential for assessing the impact of any quality improvement initiatives for radiation dose optimization.

Prototype system for interventional dual-energy subtraction angiography.

Dual-energy subtraction angiography (DESA) using fast kV switching has received attention for its potential to reduce misregistration artifacts in thoracic and abdominal imaging where patient motion is difficult to control; however, commercial interventional solutions are not currently available. The purpose of this work was to adapt an x-ray angiography system for 2D and 3D DESA. The platform for the dual-energy prototype was a commercially available x-ray angiography system with a flat panel detector and an 80 kW x-ray tube. Fast kV switching was implemented using custom x-ray tube control software that follows a user-defined switching program during a rotational acquisition. Measurements made with a high temporal resolution kV meter were used to calibrate the relationship between the requested and achieved kV and pulse width. To enable practical 2D and 3D imaging experiments, an automatic exposure control algorithm was developed to estimate patient thickness and select a dual-energy switching technique (kV and ms switching) that delivers a user-specified task CNR at the minimum air kerma to the interventional reference point. An XCAT-based simulation study conducted to evaluate low and high energy image registration for the scenario of 30-60 frame/s pulmonary angiography with respiratory motion found normalized RMSE values ranging from 0.16% to 1.06% in tissue-subtracted DESA images, depending on respiratory phase and frame rate. Initial imaging in a porcine model with a 60 kV, 10 ms, 325 mA / 120 kV, 3.2 ms, 325 mA switching technique demonstrated an ability to form tissue-subtracted images from a single contrast-enhanced acquisition.

03:36 PM Abstract No. 290 Phantom and in vivo comparison of radiation dose estimates and image quality between state-of-the-art interventional fluoroscopy systems

To compare radiation dose estimates and image quality between state-of-the-art interventional fluoroscopy systems in phantom and clinical cases. Phantom study used acrylic sheets simulating different patient sizes to compare air kerma rates (AKRs) for different dose modes on Philips Allura-ClarityIQ and Siemens ArtisQ systems (4 systems). After IRB approval, cumulative air kerma (CAK) at the interventional reference point and kerma-area product (KAP) were extracted for cases performed over a 16-month period and compared by procedure type between the two types of systems. Next, CAK and KAP for patients with metastatic uveal melanoma receiving repeat chemo/immuno-embolization of the same liver lobe by the same physician on both types of systems were compared, accounting for differences in patient positioning, reference locations and digital acquisitions. For these cases, image quality was scored by 2 CAQ certified interventional radiologists using a five-point scale for 5 parameters. Interclass correlation coefficient (ICC) was computed and the scores were compared between the two types of systems. IBM’s SPSS Statistics was used for analysis (with Bonferroni corrections for multiple comparisons). Phantom study revealed a significant lower AKR (p<0.05) with Allura-ClarityIQ for acrylic thicknesses of 30-40cm. Clinical data contained 5113 cases; significant differences for CAK and KAP were seen in 9/16 and 3/16 procedure-types (p<0.05), respectively, with lower values for Allura-ClarityIQ systems. Subset analysis of 61 patients receiving identical treatment on both systems showed CAK and KAP were significantly lower for Allura-ClarityIQ systems (p<0.02; median for CAK lower by 44% and for KAP by 27%). Good reliability and absolute agreement was noted between readers for 5 parameters (ICC≥0.75). Image quality review scores were significantly higher for images obtained with Allura-ClarityIQ systems across all parameters (p<0.05; mean difference in scores between systems for each parameter ranging from 1.3 to 1.6). Allura-ClarityIQ systems utilized lower radiation dose and were associated with superior image quality compared with ArtisQ.

Multi-facility Survey on Accuracy and Calibration Method for Dose Area Product Meter of Angiography Systems

In many facilities, the displayed dose of dose-area product (DAP) is used for the dose management of interventional radiology. In this study, we investigated the measured dose at the patient entrance reference point (interventional reference point) and the displayed dose on each angiography systems. Also, we investigated the calibration method of each DAP. The errors of the measured dose and the displayed dose were less than 35%, but that dispersion was wide between the systems. The calibration methods varies according to a system. And even in the same manufacturer, the calibration methods were different. Therefore, to use the displayed dose of DAP for patient dose management, we need to compare that with the measured dose regularly. The differences of calibration methods induce the wide dispersion of the errors of the measured and the displayed dose. So the standardization of the calibration method in each manufacturer is expected.

55 Determination of local interventional reference levels in heart surgery using a dose archiving and communication system

Introduction In cardiology, exposure of patients to ionizing radiations can reach significant levels and may sometimes cause serious complications. By taking advantage of the connection of a cardiac surgery room to the DACS (Dose Archiving and Communication System), we are seeking to determine the Local Interventional Reference Levels (IRLs) for procedures performed in this room. Methods The heart surgery department of the Pitie-Salpetriere hospital has a fixed installation (Allura Xper FD20, Philips) connected to the institutional DACS, RDM (Radiation Dose Monitor, Medsquare) since June 2016. This retrospective study examines the files recorded in the DACS of all the patients that underwent a surgery using this installation from June 2016 to December 2017. For all the files considered, the procedure indicated in the DACS is reassigned as a function of the act performed. Three main groups were defined: ECMO (ExtraCorporeal Membrane Oxygenation), Endoprosthesis and TAVI (Transcatheter Aortic Valvular Implantation). Acts such as aortic dilatation, pacemaker insertion or angioplasty, less frequent in this room, are clustered in ”Other acts”. Patients for whom the procedures are not known are gathered in a last group: NA. For the 3 main groups, medians, 75th percentiles (local IRLs), means, standard deviation, minimum and maximum values for the Dose Area Product (DAP, in mGy.cm2), the air kerma (Kair, in mGy) at the interventional reference point and the fluoroscopy time (min) are extracted using the DACS. Results A total of 430 files are recorded in the DACS: 16 in ECMO, 16 in Endoprosthesis, 275 in TAVI, 37 in Other Acts, 80 in NA. 6 files are excluded for recording reasons. For the ECMO, Endoprosthesis and TAVI groups, local IRLs of Kair are 120, 999 and 762 mGy, respectively. For DAP, the local IRLs are 46,867, 233,923 and 146,539 mGy.cm2, respectively. All the extracted values are shown in Table 1. Conclusions Once each of the surgical acts has been reassigned to a given procedure, the use of the DACS allows us to determine, quickly and globally, local IRLs for each procedure performed in this room. However, the reassignment of retrospective acts for this study is time-consuming: a priori assignment will be considered in the remainder of this work. The small number of files for ECMO and Endoprosthesis groups limits robustness of IRLs proposed for these acts. These acts being infrequent in this room, we will seek to expand the data to include a minimum of 30 files. On the other hand, for the TAVI group, the values obtained will be set as local IRLs in the DACS. Download : Download high-res image (638KB) Download : Download full-size image

283 DAP meter and SDR recording verification for angiograph used in cardiology

Purpose Aim of this study is evaluation of accuracy of dosimetric parameter and correct registration for angiograph used for cardiological procedure based on current legislation and for future BSS Directive application. Dosimetric data was registered for cardiological procedure acquired during 2 year with SDR (Structured dose report) from angiographic system, with a number of procedure executed of about 1900 exam/year and monitored with a radiation dose monitoring system (RDM). Methods We verify Philips Angiograph Allura FD20 Clarity and RDM ELCO Gray Detector. During acceptance test we measure the Dose at interventional reference point parameter and verify the accuracy of DAP and Dose (RP) from the intercomparison between data measured with a Doseguard 100 (RTI ), calibrated for RQA5 and 100 kV beam with additional copper filtration and first hvl of 6.56 mm Al. During Acceptance was verified the DAP calculation described in the document “DAP calculation Model”. The RDM system register “Total DAP value” and “Total number of exposition” with MPPS at the end of the procedure and we verify that the data was correctly registered. Results The values of DAP and Dose (RP) were in agreement with company specification, the calculated DAP parameter has a lower error associated with the inter-comparison measures than KermaXplus camera on the system (TAB 1 and Fig. 1). Data on SDR were accurate and corresponding to angulations and protocols selected. Conclusion Aim of this study is evaluation of accuracy of dosimetric parameter and correct registration for angiograph used for cardiological procedure based on current legislation and for future BSS Directive application. Dosimetric data was registered for cardiological procedure acquired during 2 year with SDR (Structured dose report) from angiographic system, with a number of procedure executed of about 1900 exam/year and monitored with a radiation dose monitoring system (RDM). We verify Philips Angiograph Allura FD20 Clarity and RDM ELCO Gray Detector. During acceptance test we measure the Dose at interventional reference point parameter and verify the accuracy of DAP and Dose (RP) from the intercomparison between data measured with a Doseguard 100 (RTI ), calibrated for RQA5 and 100 kV beam with additional copper filtration and first hvl of 6.56 mm Al. During Acceptance was verified the DAP calculation described in the document “DAP calculation Model”. The RDM system register “Total DAP value” and “Total number of exposition” with MPPS at the end of the procedure and we verify that the data was correctly registered. The values of DAP and Dose (RP) were in agreement with company specification, the calculated DAP parameter has a lower error associated with the inter-comparison measures than KermaXplus camera on the system (TAB 1 and Fig. 1). Data on SDR were accurate and corresponding to angulations and protocols selected.

Patient’s Peak Skin Dose evaluation using Gafchromic films in interventional cardiology procedures and its correlation with other dose indicators

ObjectiveNumber and complexity of interventional cardiology procedures have increased during last years and can result in patient skin dose high enough to cause deterministic skin effects. The aim of the work is to investigate the correlation between Peak Skin Dose (PSD) and the dosimetric indicators directly registered by the radiological equipment and provide the physicians a tool to identify patients at risk of deterministic effects and include them into a follow-up program. MethodsPSD was measured in vivo using radiochromic Gafchromic XR-RV3 films, properly calibrated. DAP, Cumulative Dose at the interventional reference point (CD) and exposure time of each procedure were retrieved from the Radiation Dose Structured Reports created by an Allura Clarity Xper FD20 angiographic system. Linear correlation between PSD and both DAP and CD was investigated. Results42 interventional cardiology procedures (16 CA and 26 PTCA) were involved in the study. The dosimetric indicators values for PTCA are generally higher than those for CA, due to the different levels of procedure complexity. Mean PSD values were (103 ± 64) and (526 ± 436) mGy for CA and PTCA procedures. For CA, we found strong correlation both between PSD and DAP (r = 0.753) and PSD and CD (r = 0.782). For PTCA, good correlation both for DAP (r = 0.648) and CD (r = 0.649) was found. ConclusionsDAP and CD show strong correlation with PSD measured with Gafchromic films during interventional procedures. The proposed method allows the physician to estimate patient’s PSD from the dosimetric indicators that the radiological equipment display and record at the end of the procedure.

P023] Estimating patient peak skin dose with fluoroscopic procedures

Purpose Deterministic radiation induced patient skin injuries may be caused by time consuming and complex fluoroscopic procedures. Post-procedure dose analysis can provide valuable feedback for optimisation of exposures in interventional radiology and follow-up of individual patients. However, lack of accuracy when estimating patient peak skin dose (PSD) can lead to inappropriate action levels and follow-up routines. It is common to use action levels entirely based on the interventional reference point (IRP) cumulative Air kerma, spatially located 15 cm from the irradiation geometry isocentre. This metric lacks influence of physical effects needed to estimate PSD, e.g., specifics of the irradiation event, conversion of Air kerma to absorbed skin dose, scattered radiation, and pre-patient attenuation. Modern radiologic equipment commonly reports irradiation event details in a radiation dose structured report (RDSR), as described by the NEMA DICOM standard. For fluoroscopy equipment the RDSR contains important information, e.g., X-ray beam field size, IRP Air kerma, number of images, X-ray beam filtration and X-ray tube voltage. The RDSR is thus a useful data source for estimation of PSD with fluoroscopic procedures. Methods Pertinent correction methods and data for PSD estimation were summarized by literature review and beam quality- and geometry dependent functions were developed in the PythonTM programming language v3.6 (Python Software Foundation). The RDSR from two different fluoroscopic devices; Siemens Artis Zee (Siemens Healthineers, Erlangen, Germany) and Philips Allura Clarity (Philips, Amsterdam, Netherlands), were examined and information required as input for the developed functions was identified. Results This work resulted in an open source Python™ script for RDSR parsing and patient PSD estimation; including table-top and mattress attenuation, Air kerma to absorbed skin dose conversion, forward and back scatter. PSD estimates were verified and compared to IRP Air-kerma. Conclusions The estimation of patient PSD with fluoroscopic procedures is greatly assisted by information found in fluoroscopy device RDSR. With refined dose metrics the specificity of patient PSD estimates may be increased, e.g., compared to the IRP Air kerma. Combining RDSR information and novel methods for refining patient dose metrics found in the literature can improve the management of patients after interventional radiology procedures.

OA102] Correlation between cumulative dose and peak skin dose using gafchromic films for patients undergoing interventional cardiology procedures

Purpose During last years Interventional Cardiology (IC) procedures have increased in number and complexity thus the concern about radiation dose to patients and radiation damages is increasing too. The aim of the work is to examine the radiation exposure of patients undergoing IC procedures and evaluating the deterministic risk in terms of Peak Skin Dose (PSD). Methods 40 procedures involving adult patients undergoing Coronary Angiography (CA) and Percutaneous Transluminal Coronary Angioplasty (PTCA) were involved. The procedures were performed at our institution by means of an Allura Clarity and Axiom Artis angiographic system. PSD was measured in vivo using calibrated radiochromic GafChromic XR-RV3 films and Cumulative Dose at the Interventional Reference Point (CD), reported in the Radiation Dose Structured Reports (RDSR), was collected. Linear regression between measured PSD and CD was investigated for both the angiographic systems. Results The CD values are generally higher and more variable for PTCA than for CA, due to the different procedure complexity. Mean PSD was found (103 ± 64) Gy for CA, (526 ± 436) Gy for PTCA, respectively. For the same type of procedure, values result lower on Allura Clarity system, due to his powerful dose-reduction strategies. The correlation obtained between PSD and CD was found to be good (R2 = 0.76 for Axiom Artis, R2 = 0.83 for Allura Clarity). The CD values corresponding to a PSD of 2 Gy (threshold for deterministic skin effects) are 6.0 Gy for Axiom Artis and 3.5 Gy for Allura Clarity system, respectively. Conclusions The study confirmed that IC procedures can deliver high levels of radiation dose to patients, dose increases with the complexity of procedures and can significantly depend on the X-Rays system. The correlation between PSD and CD can effectively support clinicians in identifying and managing patients at risk for deterministic effects.

Noise reduction technology reduces radiation dose in chronic total occlusions percutaneous coronary intervention: a propensity score-matched analysis.

Chronic total occlusions (CTO) percutaneous coronary intervention (PCI) is associated with high radiation dose. Our study aim was to evaluate the impact of the implementation of a noise reduction technology (NRT) on patient radiation dose during CTO PCI. A total of 187 CTO PCIs performed between February 2016 and May 2017 were analyzed according to the angiographic systems utilized: Standard (n = 60) versus NRT (n = 127). Propensity score matching (PSM) was performed to control for differences in baseline characteristics. Primary endpoints were Cumulative Air Kerma at Interventional Reference Point (AK at IRP), which correlates with patient's tissue reactions; and Kerma Area Product (KAP), a surrogate measure of patient's risk of stochastic radiation effects. An Efficiency Index (defined as fluoroscopy time/AK at IRP) was calculated for each procedure. Image quality was evaluated using a 5-grade Likert-like scale. After PSM, n = 55 pairs were identified. Baseline and angiographic characteristics were well matched between groups. Compared to the Standard system, NRT was associated with lower AK at IRP [2.38 (1.80-3.66) vs. 3.24 (2.04-5.09)Gy, p = 0.035], a trend towards reduction for KAP [161 (93-244) vs. 203 (136-363)Gycm2, p = 0.069], and a better Efficiency Index [16.75 (12.73-26.27) vs. 13.58 (9.92-17.63)min/Gy, p = 0.003]. Image quality was similar between the two groups (4.39 ± 0.53 Standard vs. 4.34 ± 0.47 NRT, p = 0.571). In conclusion, compared with a Standard system, the use of NRT in CTO PCI is associated with lower patient radiation dose and similar image quality.