A retrospective study of radiation dose measurements comparing different cath lab X-ray systems in a sample population of patients undergoing percutaneous coronary intervention for chronic total occlusions

Improvement of Radiation Management in Percutaneous Interventions of Chronic Total Occlusions in a Multicenter Registry

BACKGROUND

Excess radiation exposure is a limiting factor in percutaneous coronary intervention (PCI) for chronic total coronary occlusion (CTO).

OBJECTIVES

The aim of this study was to analyze changes in radiation dose for CTO PCI with increasing risk awareness during the past decade and the determinants of these changes.

METHODS

A total of 16,439 procedures performed by 14 operators continuously participating in the European Registry of CTO-PCI from 2012 to 2023 were analyzed. Changes in air kerma (AK) were assessed, and a dose rate index (DRI) was calculated as AK per fluoroscopy time (FT).

RESULTS

Lesion complexity increased from a median J-CTO (Multicenter CTO Registry in Japan) score of 2 (Q1-Q3: 1-3) to 3 (Q1-Q3: 2-3) (P < 0.001), and technical success improved from 89.1% to 94.9% (P < 0.001), with stable FT. AK decreased from 2.50 Gy (Q1-Q3: 1.54-4.04 Gy) to 1.20 Gy (Q1-Q3: 0.66-2.12 Gy), a reduction of 52.0% (P < 0.001). Excess radiation of AK >5 Gy was reduced from 15.8% in 2012-2013 to 3.7% in 2022-2023. Clinical determinants of excess radiation were body mass index, gender, and previous bypass surgery; procedural determinants were FT, retrograde approach, and intravascular ultrasound use; and equipment determinants were radiographic equipment updates and fluoroscopy dose mode. Operators reduced DRI by 21.7% from 62.6 mGy/min (Q1-Q3: 44.7-89.3 mGy/min) to 49.0 mGy/min (Q1-Q3: 35.4-71.2 mGy/min) before a radiographic equipment update; after the update, DRI was further reduced to 31.5 mGy/min (Q1-Q3: 22.0-45.6 mGy/min), a decrease of 28.0% (P < 0.001) The interoperator comparison of DRI indicated considerable variability in radiation management.

CONCLUSIONS

AK for CTO PCI was reduced during the past decade to a level such that most procedures no longer must be aborted because of excess radiation. Equipment updates were instrumental, but interoperator differences remained.

Update on Radiation Safety in the Cath Lab - Moving Toward a "Lead-Free" Environment

Radiation exposure in the cardiac catheterization laboratory (CCL) is an occupational hazard that predisposes health care workers to the development of adverse health effects such as cataracts, cancer, and orthopedic injury. To mitigate radiation exposure, personal protective shielding as well as permanently installed shields reduces these adverse effects. Yet, heavy protective lead aprons and poor ergonomics required for positioning movable shields remain barriers to a safer environment. Recent innovations to enhance personal protective equipment and revolutionize fixed shielding systems will permit the CCL team to work in a personal "lead-free" environment, markedly reducing occupational hazards. The purpose of this review is to update the status and future of radiation protection in the CCL.

Radiation dose during interventional cardiology procedures: portable C-arm vs. a new generation fluoroscopy system

INTRODUCTION

Occupational exposure to ionizing radiation poses health risks for veterinary interventionalists. There are limited veterinary studies evaluating radiation dose in the cardiac catheterization laboratory. The purpose of this study was to report direct radiation dose exposure to patients during common interventional cardiology procedures and compare these doses between two fluoroscopy units.

ANIMALS

One hundred and fifty-four client-owned dogs.

MATERIALS AND METHODS

Patient dose during procedures using a portable C-arm were retrospectively analyzed and compared to those performed in a contemporary interventional suite. Fluoroscopy equipment, procedure type, operator, patient weight, fluoroscopy time, dose area product, and air kerma were recorded and statistically modeled using univariable and multivariable linear regression to evaluate the effect of each factor.

RESULTS

Patient dose population (154 dogs), comprised 61 patent ductus arteriosus occlusions, 60 balloon pulmonary valvuloplasties, and 33 pacemaker implantations. Patient dose was significantly lower in the group utilizing a newer generation fluoroscopy unit vs. the group utilizing an older portable C-arm, positively correlated with patient weight, and highest during balloon pulmonary valvuloplasties compared to patent ductus arteriosus occlusions or pacemaker implantations (all p<0.010).

DISCUSSION

Newer fluoroscopy systems can be equipped with technologies that improve image quality while reducing patient dose and radiation exposure to interventional personnel.

CONCLUSIONS

We documented a significant reduction in patient radiation dose using a newer fluoroscopy system as compared to an older portable C-arm for interventional cardiology procedures in animals. Improved knowledge of patient radiation dose factors may promote better radiation safety protocols in veterinary interventional cardiology.

Generative learning approach for radiation dose reduction in X-ray guided cardiac interventions

BACKGROUND

Navigation guidance in cardiac interventions is provided by X-ray angiography. Cumulative radiation exposure is a serious concern for pediatric cardiac interventions.

PURPOSE

A generative learning-based approach is proposed to predict X-ray angiography frames to reduce the radiation exposure for pediatric cardiac interventions while preserving the image quality.

METHODS

Frame predictions are based on a model-free motion estimation approach using a Long Short Term Memory (LSTM) architecture and a content predictor using a Convolutional Neural Network (CNN) structure. The presented model thus estimates contrast-enhanced vascular structures such as the coronary arteries and their motion in X-ray sequences in an end-to-end system. This work was validated with 56 simulated and 52 patients' X-ray angiography sequences.

RESULTS

Using the predicted images can reduce the number of pulses by up to 3 new frames without affecting the image quality. The average required acquisition can drop by 30% per second for a 15 frame per second acquisition. The average Structural Similarity Index Measurement (SSIM) was 97% for the simulated dataset and 82% for the patients' dataset.

CONCLUSIONS

Frame prediction using a learning-based method is promising for minimizing radiation dose exposure. The required pulse rate is reduced while preserving the frame rate and the image quality. With proper integration in X-ray angiography systems, this method can pave the way for improved dose management. This article is protected by copyright. All rights reserved.

Eye protection in interventional procedures

Data suggest that radiation-induced cataracts may form without a threshold and at low-radiation doses. Staff involved in interventional radiology and cardiology fluoroscopy-guided procedures have the potential to be exposed to radiation levels that may lead to eye lens injury and the occurrence of opacifications have been reported. Estimates of lens dose for various fluoroscopy procedures and predicted annual dosages have been provided in numerous publications. Available tools for eye lens radiation protection include accessory shields, drapes and glasses. While some tools are valuable, others provide limited protection to the eye. Reducing patient radiation dose will also reduce occupational exposure. Significant variability in reported dose measurements indicate dose levels are highly dependent on individual actions and exposure reduction is possible. Further follow-up studies of staff lens opacification are recommended along with eye lens dose measurements under current clinical practice conditions.

Reducing fluoroscopic and cineangiographic contribution to radiation exposure for chronic total coronary occlusion interventions

BACKGROUND

The treatment of chronic total coronary occlusions (CTO) carries the highest radiation exposure among percutaneous coronary interventions (PCI). In order to minimize radiation damage, we need to understand and optimize the contribution of all components of radiation exposure.

METHODS

A total of 1000 CTO procedures performed between 2011 and 2020 were compared according to implemented radiation modifications. Group 1 used the original set-up of the X-ray equipment (Artis Zee, Siemens). In group 2 a modified protocol aimed at reducing the fluoroscopy exposure, in group 3 further modifications aimed at reducing cineangiographic exposure.

RESULTS

Despite an increased lesion complexity, Air Kerma (AK) was reduced from 2619 mGy (1653-4574) in group 1 to 2178 mGy (1332-3500; p < 0.001) in group 2 by mainly reducing fluoroscopic contribution by 54.1%, the cineangiographic contribution was lowered by only 6.6%. In group 3 AK dropped drastically to 746 mGy (480-1225; p < 0.001) mainly by reducing the cineangiographic contribution by 53.4%, still there was a further reduction of fluoroscopy contribution of 8.2%. This also led to a reduction of the skin entry dose from 1038 mGy (690-1589) in group 2 to 359 mGy (204-591; p < 0.001) in group 3. This was achieved both in normal weight and obese patients, and both in antegrade and retrograde procedures.

CONCLUSIONS

The present study demonstrates that by modifying both the fluoroscopic and cineangiographic contribution to radiation exposure a drastic reduction of radiation risk can be achieved, even in obese patients. Currently accepted radiation thresholds may no longer be a limit for CTO PCI.

Image-derived mean velocity measurement for prediction of coronary flow reserve in a canonical stenosis phantom using magnetic particle imaging

INTRODUCTION

Aim of this study is to evaluate whether magnetic particle imaging (MPI) is capable of measuring velocities occurring in the coronary arteries and to compute coronary flow reserve (CFR) in a canonical phantom as a preliminary study.

METHODS

For basic velocity measurements, a circulation phantom was designed containing replaceable glass tubes with three varying inner diameters, matching coronary-vessel diameters. Standardised boluses of superparamagnetic-iron-oxide-nanoparticles were injected and visualised by MPI. Two image-based techniques were competitively applied to calibrate the respective glass tube and to compute the mean velocity: full-duration-at-half-maximum (FDHM) and tracer dilution (TD) method. For CFR-calculation, four necessary settings of the circulation model of a virtual vessel with an inner diameter of 4 mm were generated using differently sized glass tubes and a stenosis model. The respective velocities in stenotic glass tubes were computed without recalibration.

RESULTS

On velocity level, comparison showed a good agreement (rFDHM = 0.869, rTD = 0.796) between techniques, preferably better for 4 mm and 6 mm inner diameter glass tubes. On CFR level MPI-derived CFR-prediction performed considerably inferior with a relative error of 20-44%.

CONCLUSIONS

MPI has the ability to reliably measure coronary blood velocities at rest as well as under hyperaemia and therefore may be suitable for CFR calculation. Calibration-associated accuracy of CFR-measurements has to be improved substantially in further studies.

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 International Atomic Energy Agency action plan on radiation protection of patients and staff in interventional procedures: Achieving change in practice

INTRODUCTION

The International Atomic Energy Agency (IAEA) organized the 3rd international conference on radiation protection (RP) of patients in December 2017. This paper presents the conclusions on the interventional procedures (IP) session.

MATERIAL AND METHODS

The IAEA conference was conducted as a series of plenary sessions followed by various thematic sessions. "Radiation protection of patients and staff in interventional procedures" session keynote speakers presented information on: 1) Risk management of skin injuries, 2) Occupational radiation risks and 3) RP for paediatric patients. Then, a summary of the session-related papers was presented by a rapporteur, followed by an open question-and-answer discussion.

RESULTS

Sixty-seven percent (67%) of papers came from Europe. Forty-four percent (44%) were patient studies, 44% were occupational and 12% were combined studies. Occupational studies were mostly on eye lens dosimetry. The rest were on scattered radiation measurements and dose tracking. The majority of patient studies related to patient exposure with only one study on paediatric patients. Automatic patient dose reporting is considered as a first step for dose optimization. Despite efforts, paediatric IP radiation dose data are still scarce. The keynote speakers outlined recent achievements but also challenges in the field. Forecasting technology, task-specific targeted education from educators familiar with the clinical situation, more accurate estimation of lens doses and improved identification of high-risk professional groups are some of the areas they focused on.

CONCLUSIONS

Manufacturers play an important role in making patients safer. Low dose technologies are still expensive and manufacturers should make these affordable in less resourced countries. Automatic patient dose reporting and real-time skin dose map are important for dose optimization. Clinical audit and better QA processes together with more studies on the impact of lens opacities in clinical practice and on paediatric patients are needed.

Common and Uncommon CTO Complications

Despite the ongoing development of technical skills, increasing operator experience and improvements in medical devices, percutaneous coronary interventions (PCI) for chronic total occlusions (CTO) are still the most challenging procedures in interventional cardiology for coronary artery disease. Due to the complexity of the procedures, there is an increased complication rate compared with PCIs for the treatment of non-occlusive disease. This may significantly increase procedural morbidity and potentially mortality. CTO-PCI related complications include all the usual complications that are seen in routine PCI in addition to unique issues such as inadvertent occlusion of donor vessels or injury of collateral channels causing haemodynamic instability or ischaemia. To minimise the morbidity associated with these procedures, it is important to be aware of potential complications and recognise them in a timely fashion. Should they arise, operators should be able to deal with them in a safe and efficient manner.