Results from a real-time dosimetry study during left atrial ablations performed with ultra-low dose radiation settings

Background

Three-dimensional mapping systems and the use of ultra-low dose radiation protocols have supported minimization of radiation dose during left atrial ablation procedures. By using optimal shielding, scattered radiation reaching the operator can be further reduced. This prospective study was designed to determine the remaining operator radiation exposure during left atrial catheter ablations using real-time dosimetry.

Methods

Radiation dose was recorded using real-time digital dosimetry badges outside the lead apron during 201 consecutive left atrial fibrillation ablation procedures. All procedures were performed using the same X‑ray system (Siemens Healthineers Artis dBc; Siemens Healthcare AG, Erlangen, Germany) programmed with ultra-low dose radiation settings including a low frame rate (two frames per second), maximum copper filtration, and an optimized detector dose. To reduce scattered radiation to the operators, table-suspended lead curtains, ceiling-suspended leaded plastic shields, and radiation-absorbing shields on the patient were positioned in an overlapping configuration.

Results

The 201 procedures included 139 (69%) pulmonary vein isolations (PVI) (20 cryoballoon ablations, 119 radiofrequency ablations, with 35 cases receiving additional ablation of the cavotricuspid isthmus) and 62 (31%) PVI plus further left atrial substrate ablation.

Mean radiation dose measured as dose area product for all procedures was 128.09 ± 187.87 cGy ∙ cm² with a mean fluoroscopy duration of 9.4 ± 8.7 min. Real-time dosimetry showed very low average operator doses of 0.52 ± 0.10 µSv. A subanalysis of 51 (25%) procedures showed that the radiation burden for the operator was highest during pulmonary vein angiography.

Conclusion

The use of ultra-low dose radiation protocols in combination with optimized shielding results in extremely low scattered radiation reaching the operator.

Reduced radiation exposure in the cardiac catheterization laboratory with a novel vertical radiation shield

Objectives

Investigation of novel vertical radiation shield (VRS) in reducing operator radiation exposure.

Background

Radiation exposure to the operator remains an occupational health hazard in the cardiac catheterization laboratory (CCL).

Methods

A mannequin simulating an operator was placed near a computational phantom, simulating a patient. Measurement of dose equivalent and Air Kerma located the angle with the highest radiation, followed by a common magnification (8 in.) and comparison of horizontal radiation absorbing pads (HRAP) with or without VRS with two different: CCL, phantoms, and dosimeters. Physician exposure was subsequently measured prospectively with or without VRS during clinical procedures.

Results

Dose equivalent and Air Kerma to the mannequin was highest at left anterior oblique (LAO)‐caudal angle (p < .005). Eight‐inch magnification increased mGray by 86.5% and μSv/min by 12.2% compared to 10‐in. (p < .005). Moving 40 cm from the access site lowered μSv/min by 30% (p < .005). With LAO‐caudal angle and 8‐in. magnification, VRS reduced μSv/min by 59%, (p < .005) in one CCL and μSv by 100% (p = .016) in second CCL in addition to HRAP. Prospective study of 177 procedures with HRAP, found VRS lowered μSv by 41.9% (μSv: 15.2 ± 13.4 vs. 26.2 ± 31.4, p = .001) with no difference in mGray. The difference was significant after multivariate adjustment for specified variables (p < .001).

Conclusions

Operator radiation exposure is significantly reduced utilizing a novel VRS, HRAP, and distance from the X‐ray tube, and consideration of lower magnification and avoiding LAO‐caudal angles to lower radiation for both operator and patient.

[Update on radiation exposure in catheter ablation of atrial fibrillation]

The rising number of catheter ablations of atrial fibrillation increases radiation exposure for both patients and surgeons. Fortunately, this trend is counteracted by the development of measures to reduce total fluoroscopy time using non-fluoroscopic catheter visualization. Since even low-dose radiation can cause serious injury, all options to reduce radiation burden must be utilized (ALARA, "as low as reasonably achievable"). Dose reduction protocols with low-dose settings, which include reduced framerates, pulse duration, detector entrance dose and increased beam hardening, play a decisive role in this regard. This review provides a state-of-the-art summary of non-fluoroscopic catheter visualization and dose reduction protocols for catheter ablation of atrial fibrillation.

Decreased operator X-ray exposure by optimized fluoroscopy during radiofrequency ablation of common atrial flutter

PURPOSE

To evaluate operator and patient irradiation during radiofrequency ablation (RFA) of common atrial flutter (AF) using three different fluoroscopy settings.

MATERIAL AND METHOD

A total of 38 patients who underwent RFA of AF with three different fluoroscopy settings (low dose, standard dose and collimated field) were included. Twelve patients (11 men, 1 woman; mean age, 67±12 [SD]years) were included in the low dose group (3.75 frames per second), 13 patients (13 men; mean age, 66±8 [SD]years) were included in the standard dose group (7.5 frames per second) and 13 patients (13 men; mean age, 71±12 [SD]years) were included in the collimated field group (7.5 frames per second). Operator and patient exposure were compared between groups.

RESULT

No differences in procedure time and radiation exposure were found between the three groups. In the low dose group, mean operator X-ray exposures of eye-lens (4.7±2.9 [SD]μSv/h; range: 0.9-10.5μSv/h), whole body (1.6±1.2 [SD]μSv/h; range 0.5-3.6μSv/h) and hand skin (11.1±10.8 [SD] μSv/h; range 2.4-35.4μSv/h) were significantly lower than those in the standard dose group (P<0.001). Significant patient dose reduction was found between low dose group (0.7±0.4 [SD]Gy/h; range: 0.3-0.9Gy/h) and standard (1.7±0.5 [SD]Gy/h; range: 0.8 to 3.9Gy/h) and collimated (1.8±0.5 [SD]Gy/h; range: 0.7-3.0Gy/h) groups (P<0.01).

CONCLUSION

The use of a low dose setting (3.75 f/s) during fluoroscopy dramatically reduces operator's irradiation during RFA of AF by a mean of 90%.

Reduction of Fluoroscopy Time and Radiation Dosage During Catheter Ablation for Atrial Fibrillation

Radiofrequency catheter ablation has become the treatment of choice for atrial fibrillation (AF) that does not respond to antiarrhythmic drug therapy. During the procedure, fluoroscopy imaging is still considered essential to visualise catheters in real-time. However, radiation is often ignored by physicians since it is invisible and the long-term risks are underestimated. In this respect, it must be emphasised that radiation exposure has various potentially harmful effects, such as acute skin injury, malignancies and genetic disease, both to patients and physicians. For this reason, every electrophysiologist should be aware of the problem and should learn how to decrease radiation exposure by both changing the setting of the system and using complementary imaging technologies. In this review, we aim to discuss the basics of X-ray exposure and suggest practical instructions for how to reduce radiation dosage during AF ablation procedures.

Significant radiation reduction in interventional fluoroscopy using a novel eye controlled movable region of interest

PURPOSE

This paper reports the first results obtained using a novel technology called eye controlled region of interest (ECR) that substantially reduces both staff and patient irradiation during an interventional fluoroscopy procedure without interfering with workflow. Its collimator includes a partially x-ray attenuating plate with a nonattenuating aperture. An eye tracker follows the operator's gaze to automatically position the aperture to the clinical region of interest (CROI) anywhere in the image in real-time.

METHODS

Experiments were performed in a swine model using a mobile fluoroscope with a 30 cm image intensifier and manual control of fluoroscopic factors. The factory collimator and image display monitor were replaced with different components for this study. The full 30 cm field-of-view (FOV) of the image intensifier was irradiated at normal levels, and served as a baseline, when ECR was disengaged. With ECR engaged, most of the 30 cm FOV was irradiated to less than 20% of normal levels while the CROI was normally irradiated. Animal irradiation was determined by physical KAP (kerma area product) measurements. Operator irradiation was characterized by air kerma and air kerma rate measurements near the operator. Data were collected from three pairs of interventions in each of five swine models.

RESULTS

When ECR was engaged, KAP was reduced to 0.22 (p < 0.001) of baseline and operator irradiation to 0.27 (p < 0.001) of baseline. Overall procedure time had a borderline increase (p = 0.07) but fluoroscopy time was unchanged (p = 0.36) (Wilcoxon signed rank). Measured staff and patient radiation reductions are consistent with this collimator's design. Subjective impressions of imaging improvements are consistent with less scatter reaching the CROI. Engaging ECR reduced irradiation without subjectively or objectively increasing operator workload.

CONCLUSIONS

The first in vivo evaluation of ECR demonstrated that this technology has objectively reduced KAP and operator irradiation by approximately 75% without interfering with the performance of fluoroscopically guided interventional procedures. In addition, reduced scatter production subjectively improved device visualization. These findings indicate the practicability of achieving better radiation optimization.

Evaluation of a new very low dose imaging protocol: feasibility and impact on X-ray dose levels in electrophysiology procedures

Aims

This study presents and evaluates the impact of a new lowest-dose fluoroscopy protocol (Siemens AG), especially designed for electrophysiology (EP) procedures, on X-ray dose levels.

Methods and results

From October 2014 to March 2015, 140 patients underwent an EP study on an Artis zee angiography system. The standard low-dose protocol was operated at 23 nGy (fluoroscopy) and at 120 nGy (cine-loop), the new lowest-dose protocol was operated at 8 nGy (fluoroscopy) and at 36 nGy (cine-loop). Procedural data, X-ray times, and doses were analysed in 100 complex left atrial and in 40 standard EP procedures. The resulting dose–area products were 877.9 ± 624.7 µGym² (n = 50 complex procedures, standard low dose), 199 ± 159.6 µGym² (n = 50 complex procedures, lowest dose), 387.7 ± 36.0 µGym² (n = 20 standard procedures, standard low dose), and 90.7 ± 62.3 µGym² (n = 20 standard procedures, lowest dose), P < 0.01. In the low-dose and lowest-dose groups, procedure times were 132.6 ± 35.7 vs. 126.7 ± 34.7 min (P = 0.40, complex procedures) and 72.3 ± 20.9 vs. 85.2 ± 44.1 min (P = 0.24, standard procedures), radiofrequency (RF) times were 53.8 ± 26.1 vs. 50.4 ± 29.4 min (P = 0.54, complex procedures) and 10.1 ± 9.9 vs. 12.2 ± 14.7 min (P = 0.60, standard procedures). One complication occurred in the standard low-dose and lowest-dose groups (P = 1.0).

Conclusion

The new lowest-dose imaging protocol reduces X-ray dose levels by 77% compared with the currently available standard low-dose protocol. From an operator standpoint, lowest X-ray dose levels create a different, reduced image quality. The new image quality did not significantly affect procedure or RF times and did not result in higher complication rates. Regarding radiological protection, operating at lowest-dose settings should become standard in EP procedures.

Practical ways to reduce radiation dose for patients and staff during device implantations and electrophysiological procedures

Despite the advent of non-fluoroscopic technology, fluoroscopy remains the cornerstone of imaging in most interventional electrophysiological procedures, from diagnostic studies over ablation interventions to device implantation. Moreover, many patients receive additional X-ray imaging, such as cardiac computed tomography and others. More and more complex procedures have the risk to increase the radiation exposure, both for the patients and the operators. The professional lifetime attributable excess cancer risk may be around 1 in 100 for the operators, the same as for a patient undergoing repetitive complex procedures. Moreover, recent reports have also hinted at an excess risk of brain tumours among interventional cardiologists. Apart from evaluating the need for and justifying the use of radiation to assist their procedures, physicians have to continuously explore ways to reduce the radiation exposure. After an introduction on how to quantify the radiation exposure and defining its current magnitude in electrophysiology compared with the other sources of radiation, this position paper wants to offer some very practical advice on how to reduce exposure to patients and staff. The text describes how customization of the X-ray system, workflow adaptations, and shielding measures can be implemented in the cath lab. The potential and the pitfalls of different non-fluoroscopic guiding technologies are discussed. Finally, we suggest further improvements that can be implemented by both the physicians and the industry in the future. We are confident that these suggestions are able to reduce patient and operator exposure by more than an order of magnitude, and therefore think that these recommendations are worth reading and implementing by any electrophysiological operator in the field.