How can the production of scattered radiation be reduced

There is a quasi-linear dose reduction with reduction of the irradiated surface area. In the beginning of the procedure a larger view may be desirable. Later, one usually focuses on a particular region; more collimation is then possible and desirable. Nurses and technicians should have autonomy and responsibility to adjust the collimation field while the EP operator is working.

The availability of 2D—3D integration may allow for more informed collimation, since the required parts of the heart that need to be visualized are more obvious. The radiation dose for the patient, the operator, and the other personnel relates to the framerate of the fluoro or the cine acquisitions, albeit not always linearly due to the compensatory adjustments of dose per pulse depending on the system.

The framerate should be set as low as possible. Most EP manoeuvres can easily be performed with 3 fps, and often 1 fps can be sufficient. Some vendors allow triggered fluoroscopy, with one image made during each QRS, pacing stimulus, or other trigger.

During a transseptal puncture or during ablation in the vicinity of the AV node, however, a higher framerate may be desirable. Therefore, adjustments in the framerate are required throughout the procedure. The auto-exposure settings that control the detector target dose rate also need adaptation throughout the procedure.

When only catheters with big regular electrodes are being used, low-dose grainier imaging is sufficient, as demonstrated in Figure 6 and online Supplemental Video S1. This needs to be tailored to the patient constitution too, with higher body mass index BMI patients requiring higher doses.

In contrast, when smaller electrodes need to be visualized e. Fluoroscopic imaging with lower dose settings often suffices for EP applications right PV isolation. See also Supplemental Video S1. The dose setting protocols also include adaptations in Cu filtering. E Same image with cine settings. Only the LAO images are shown. Although the image gets grainier with reduced dose settings, they still are largely sufficient to visualize the regular EP catheters.

This can be appreciated even better in movie mode, as can be judged from the online Supplemental Video S1 taken at 3 fps , that also shows the RAO acquisitions. If required for verification or adjustment in more obese patients, one could temporarily switch to a higher dose setting. The optimal setting will largely depend on the patient's BMI. Therefore, the equipment should have many settings available, allowing the choice of the most appropriate one throughout different stages of the procedure.

Avoid screening the pelvic area during advancement of the catheters from the groin, especially in young women. With gentle rotation, aiming the catheter curve anteriorly, the catheter generally can be advanced without need for fluoroscopic guidance. Only perform fluoroscopy when really needed. When rotational angiography is performed, the same considerations apply: collimate as much as possible possibly after a test bolus of contrast during low-dose fluoroscopy to define the margins of the chamber of interest , and ask your vendor to provide low-dose rotational protocols.

As a result of all these adaptations, the total fluoroscopy time FT is certainly not the most important factor determining patient exposure as erroneously used in many reports , but the number of frames, their collimation, and the dose settings will have determined the ED.

Shielding is of crucial importance for exposure reduction, and can be achieved at different levels, as indicated in Table 5. All the persons in the room must be protected, at least with a lead apron. The physician should also wear a thyroid collar and leaded glasses. One should be aware that this protection equipment undergoes wear and tear, requiring periodic inspections.

The fluoroscopy systems should have two separate shielding screens to protect the operator, and both should be used correctly. The lower screen usually is connected to the table such that it moves with the table.

Too often, however, that screen hinders table movement or is pushed aside by the X-ray tube under the table. This may lead to irritation and underuse.

An elegant solution is to have the lower screen connected to the upper part of the table foot instead of to the table itself. Then, it still moves up and down but not horizontally Figure 7 A and B. The upper shield should be mounted on an arm connected to the ceiling or a separate supporting stand. Both the screens should be placed such that the operator is optimally shielded from the radiation source i. To improve shielding, lead flaps rather than a sturdy screen can be used: by adjusting the height of the bar carrying the flaps above the patient, they can be adjusted to just touch the patient Figure 7 C.

Shielding measures during EP procedures. A Lead-glass shielding screens above and below the table. Take care of the overlap between both screens. B Details showing the fixation of the lower lead screen to the upper part of the table foot instead of to the moving table , avoiding hindrance by the screen during table movements. C Both the use of the lead flaps above and under the table, as the concomitant use of a radiation protection cabin, to optimally reduce exposure to the operator, but also to nurses working at the foot of the table.

The height of the upper lead flaps support is adjusted so that the flaps just touch the patients belly, to minimize scatter towards the cath lab. Since the operator is fully protected and can perform the full procedure from within the cabin, he does not have to wear a lead apron, thyroid collar, or lead glasses anymore, while the cabin also reduces orthopaedic strain.

Of course, in case the operator wants to perform part of the procedure without the cabin, or has to assist a co-worker who stands inside the cabin, lead protection is deserved.

D Lead screens that protect the anaesthesiologist. One screen is put at the front of a small table; the other one between the patient and the equipment cart arrows. The screens are moveable to allow for repositioning of the C-arms if needed.

Almost complete operator protection can be achieved by a radioprotection cabin or suspended operator protection system , that reduces exposure to near background levels, including complete protection of the eyes, the brain, and the axillary region often partially unprotected with lead aprons Figure 7 C. All the aspects of the invasive EP procedures including transseptal puncture and exchange of the sheaths can be performed.

Recently, a new type of cabin has been developed that also allows for device implantation, which was hard to do with the original cabin. Since device implantations currently form the major source of radiation for interventional electrophysiologists, evaluation of the practical usefulness of these cabins and suspended systems during implantations is highly recommended. Cath lab nurses may receive high cumulative exposures when they also assist with coronary interventions where cine is frequently used.

This will also guarantee mobility of the setup, e. Since the anaesthesiologists sometimes move around the patient, they should wear lead aprons too. Moreover, allied professionals and anaesthesiologists should signal to the operator their intent to approach the patient, so that fluoroscopy can be temporarily halted if possible. There have been a number of studies demonstrating the benefits of the original NFM in terms of fluoroscopy reduction, and there is a huge potential for the MediGuide system to achieve even larger radiation dose reductions since it projects the real-time catheter movement on stored fluoroscopy loops.

Education in this respect is very important see below. Also, the procedure costs are increased with NFM. LocaLisa an earlier version of the technology now used for Ensite NavX has been shown to reduce fluoroscopy times FTs more significantly for ablation of atrioventricular nodal reentry tachycardia AVNRT 10 vs.

Complex and long procedures can benefit most from NFM technology to reduce the radiation exposure. On the other hand, the transseptal puncture associated with AF ablation requires X-ray.

It is possible to use the NavX system to track the position of the transseptal needle, and the use of intracardiac echo and NFM make it possible to perform AF ablation without radiation. There are little data examining the impact of NFM technology on ventricular arrhythmia ablation because such systems are now considered to be the standard of care in these complex interventions. Non-fluoroscopic mapping systems have other benefits and radiation reduction is not the sole reason for using these systems.

Magnetic resonance imaging MRI -guided catheter ablation offers promise for high-resolution catheter imaging with minimal or no radiation, but is still under development and not ready yet for widespread clinical use. Moreover, the cost—benefit of such approaches will merit evaluation. Systems allowing remote navigation through a joystick by moving special catheters by electromagnetic fields e.

The radiation dose required to eliminate a patient's arrhythmia not only includes the procedure dose but also that of any pre-operative investigations. Computed tomography scans are often used to merge with the NFM system to provide a more accurate geometry. This additional dose can be avoided by using MRI. However, the NFM systems now produce a geometry of sufficient quality where these merging strategies are not necessary anymore in more experienced centres. Moreover, the approach of merging 3D cardiac CT images with NFM has not shown to have an effect on the procedural outcomes.

The trainees' first experience of cardiac procedures often involves X-ray as the sole method of imaging, e. This means that the trainees develop habits of dependence on fluoroscopic systems at the very beginning of their training, which takes some time to break.

The development of increasingly sophisticated simulators could allow the trainees to familiarize themselves with the NFM systems for complex EP procedures at an earlier stage in their training and thus make this instinctive dependence less prominent. Indeed, radiation reduction by NFM is possible during:. On the other hand, when the ablation catheters are used to create a geometry, e. Force sensing technologies may overcome this risk but this is yet to be proven.

Entanglement within the mitral valve apparatus is still a potential risk during geometry sampling. The left atrioventricular annulus is far more accurately defined by electrograms and the location of a coronary sinus catheter on NFM than by fluoroscopy. Energy delivery : Many operators are anxious about the chamber geometry errors that inevitably occur with the NFM systems. The natural response is to look on the X-ray system to check the catheter position even though the fluoroscopy gives far less anatomical accuracy.

It is important to remind the trainees that the catheter movement within a geometry is as important as its absolute location, i. Withdrawal of the catheters : Even small periods of fluoroscopy that are not necessary can be cumulative and result in a large dose at the end of a long procedure.

For example, there is rarely a justification for using X-ray just to withdraw a catheter. There are a number of key areas requiring development to refine NFM, and hence, to improve operator confidence in using NFM instead of fluoroscopy:. Geometry accuracy : Inaccuracies may be the result of fluid balance changes, patient and respiratory movement during geometry acquisition, or the inaccuracy of catheter location.

Registration : Gating to the respiratory cycle during geometry acquisition is now possible but moving the geometry with the heart's movement during respiration is still under development. Correcting for patient movement is improving with each generation of the mapping systems. Force sensing is likely to reduce FTs. Sheath visualization : Sheaths are frequently used to help manipulate the catheter but are not visualized on the NFM systems, requiring additional X-rays.

Magnetic resonance imaging and other imaging guidance : Integrated imaging remains a promising avenue of research to optimize the anatomical accuracy of the NFM. Radiation protection is a serious issue for all the workers in a cath lab. In contrast, device implantation and especially the insertion of the LV epicardial electrode, causes the highest exposure today. Device implantation procedures thus are the first priority for future exposure reduction measures in EP, and the EP insights in doing so should stimulate the dose reduction measures in the rest of interventional cardiology too.

Up to this point in the procedure, 2 min of fluoroscopy have been used to perform the transseptal punctures. From now on the AF ablation is radiation free. Creation of the left PV geometry. It is then pulled further back and rotated clockwise until it flicks up into the anterior and more superior left upper PV LUPV.

The LPV geometry is shown and is a reference point for the rest of the geometry. The body of the LA geometry is now created. The catheter is then withdrawn, deflected and turned slightly anticlockwise until it is seen to drop off the RUPV.

It is seen to drop briefly into the RLPV but then flicks out. Rotation clockwise allows it to turn back into the RLPV. It is then pulled out and rotated anticlockwise to move it to the anterior LA and advanced into the LAA. Once these five anatomical reference points have been marked the rest of the geometry is easily filled in.

The first step for this is to pull the PV catheter out of the LAA and fully deflect it while gently advancing it. The catheter inverts and can then be pulled back in this orientation to the septum without concern that it will come back through the transseptal puncture. The catheter tip will stop moving when it hits the septum and can then be advanced and retracted while rotating it to fill the septal aspect of the LA.

The catheter can then be straightened and pulled back to the septum so that the shaft of the PV comes slightly back through the transseptal puncture and a tongue of tissue is seen extending back through the septum. This allows the site of the transseptal puncture to be marked so that the catheters can be advanced back into the LA without the X-ray if they are withdrawn to the right heart.

The operator can now position the PV catheter in one of the PVs and the ablation can begin. For LV lead placement, multiple cine loops are often required for venous angiography and for visualizing the course of the venous guidewire.

The guidewires have the poorest visibility. Development of guidewires with a 20 cm long distal radiopaque section instead of the usual 1—2 cm would allow for significantly lower fluoroscopic doses. Device implantation also does not allow for the standard lead screens that are common with groin catheterizations.

An alternative protection measure, using a custom 0. Other measures may also include specially designed radioprotection cabin and suspended protection screens. The industry and the physicians should be urged to evaluate such solutions during device implantations, and continuous improvements to such solutions. Measured doses with and without an arm rest lead screen during device implantations, as shown in Figure 9.

Measurement of the operator exposure with the Rando phantom to simulate the situation during device implantation. During these measurements, the heart was in the isocentre and the detector was lowered as much as possible. The dosimeters were placed at a 50 cm horizontal distance from the centre of the patient thorax and two different heights above the floor level.

Note that the absolute values of the dose rate may be very different depending on the particular setting of the fluoroscopy mode of the X-ray system. Optimization of the lead protection during device implantation procedures, Cross-sectional view of a patient on the fluoroscopy table. The operator usually stands on the left side of the patient and therefore the dose rates were measured at that side at and cm above the floor with the patients heart in the isocentre.

The dosimeters are sketched in red. The custom 0. Newer NFM systems, like the MediGuide system, make use of very tiny location sensors which can be embedded even in guidewires. Such a technology may prove pivotal in reducing radiation dose in implantation procedures, which was not possible with the existing NFM so far.

The fluoroscopy systems should therefore offer more easily accessible options for these different framerates to reduce practical barriers in using those during EP interventions. X-ray companies continue to improve their imaging systems, both concerning emitter and detector technology as through more complicated image processing techniques, leading to better noise reduction and allowing comparable image quality with substantially lower radiation.

Although collimation is available in all the radiographic imaging systems, its implementation is largely suboptimal. In many cath labs, collimation setting can only be performed from the command panels next to the table, not from the control room. Often the interface is non-intuitive, with the nurse or the technician struggling to quickly adapt the collimation field.

This hampers frequent adjustments throughout the procedure. Moreover, optimal collimation in a biplane setup requires precise placement of the area of interest in the iso-centre and can thus only be achieved by moving the table. Table repositioning is then required when the target area shifts, e. Therefore, we call for an easier implementation of the collimation settings by cath lab vendors, with a simple and intuitive graphical user interface.

Collimation also limits the view on other catheters and the cardiac contour. The operator may want to quickly check those. Then, however, one has to open the view and re-collimate thereafter.

Fluoroscopy systems should enable storage of different collimation settings and allow a quick switch between a saved collimated and uncollimated view. Multiple collimation settings could be saved for different targets. It should also be possible to set collimation asymmetrically, which is impossible nowadays but could be easily provided since the hardware is present in most systems.

It would also eliminate the hassle of table repositioning with a switch of the target area. To facilitate the use of asymmetric collimation on monoplane systems, collimation would have to switch automatically from one setting to the other when the system is rotated from RAO to LAO.

Last but not the least, collimation could be optimized based on 3D heart chamber information, when 3D—2D image integration is used. The collimation is wide open, revealing all the intracardiac catheters.

Often such a view is used throughout a whole ablation procedure. However, mapping and ablation usually focuses on a particular part of the heart. With all the other catheters in stable position, the collimation field can be further reduced as is shown in B , when the target is the ablation of both the ipsilateral veins with a common encircling, or when the individual veins would be targeted.

With movement of the table, further optimization would be possible. An aperture diaphragm is a flat piece of lead diaphragm that has a hole aperture in it. Commercially made aperture diaphragms are available Figure , or hospitals make their own for purposes specific to a radiographic unit. Aperture diaphragms are easy to use. They are placed directly below the x-ray tube window. An aperture diaphragm can be made by cutting rubberized lead into the size needed to create the diaphragm and cutting the center to create the shape and size of the aperture.

Although the size and shape of the aperture can be changed, the aperture cannot be adjusted from the designed size, and therefore the projected field size is not adjustable. Although aperture diaphragms are still used in some applications, their use is not as widespread as other types of beam-restricting devices. Cones and cylinders are shaped differently Figure , but they have many of the same attributes. A cone or cylinder is essentially an aperture diaphragm that has an extended flange attached to it.

The flange can vary in length and can be shaped as either a cone or a cylinder. The flange can also be made to telescope, increasing its total length Figure Similar to aperture diaphragms, cones and cylinders are easy to use. They slide onto the tube, directly below the window. Cones and cylinders limit unsharpness surrounding the radiographic image more than aperture diaphragms do, with cylinders accomplishing this task slightly better than cones Figure However, they are limited in terms of available sizes, and they are not interchangeable among tube housings.

Cones have a particular disadvantage compared with cylinders. If the angle of the flange of the cone is greater than the angle of divergence of the primary beam, the base plate or aperture diaphragm of the cone is the only metal actually restricting the primary beam. Therefore, cylinders generally are more useful than cones. Cones and cylinders are almost always made to produce a circular projected field, and they can be used to advantage for particular radiographic procedures Figure The most sophisticated, useful, and accepted type of beam-restricting device is the collimator.

Collimators are considered the best type of beam-restricting device available for radiography. Beam restriction accomplished with the use of a collimator is referred to as collimation. The terms collimation and beam restriction are used interchangeably.

A collimator has two or three sets of lead shutters Figure Located immediately below the tube window, the entrance shutters limit the x-ray beam much as the aperture diaphragm would. One or more sets of adjustable lead shutters are located 3 to 7 inches 8 to 18 cm below the tube. These shutters consist of longitudinal and lateral leaves or blades, each with its own control. This design makes the collimator adjustable in terms of its ability to produce projected fields of varying sizes.

The field shape produced by a collimator is always rectangular or square, unless an aperture diaphragm, cone, or cylinder is slid in below the collimator. Collimators are equipped with a white light source and a mirror to project a light field onto the patient. This light is intended to indicate accurately where the primary x-ray beam will be projected during exposure.

In case of failure of this light, an x-ray field measurement guide Figure is present on the front of the collimator. This guide indicates the projected field size based on the adjusted size of the collimator opening at particular source-to-image receptor distances SIDs.

This guide helps ensure that the radiographer does not open the collimator to produce a field that is larger than the IR. Another problem that may occur is the lack of accuracy of the light field.

The mirror that reflects the light down toward the patient or the light bulb itself could be slightly out of position, projecting a light field that inaccurately indicates where the primary beam will be projected. There is a means of testing the accuracy of this light field and the location of the center of projected beam Box In addition, if the x-ray central ray is not perpendicular to the table and Bucky tray, radiographic quality may be compromised.

A collimator and beam alignment test tool template and cylinder can be radiographed easily and evaluated for proper alignment. A plastic template with cross hairs is affixed to the bottom of the collimator to indicate where the center of the primary beam—the central ray—will be directed.

This template is of great assistance to the radiographer in accurately centering the x-ray field to the patient. An automatic collimator, also called a positive beam-limiting device,. Scatter Control. Chapter 5. Objectives After completing this chapter, the reader will be able to perform the following: 1. Therefore, we do not allow significant others in the imaging room when we are using ionizing radiation for imaging.

In select and rare circumstances, significant others may enter the room so long as they remain behind the safety barrier and window.

We understand diagnostic imaging can be stressful, which is why we try to complete your exam efficiently. We also realize that support from your significant other can help you through tough times, so we do make some exceptions in situations where the exams do not rely on ionizing radiation and the room is deemed safe by technologists , such as pregnancy ultrasounds. We are not trying to make your exam more stressful by keeping significant others out of a room with radiation.

At the end of the day, we want to capture the best images possible so your doctor can make a timely and accurate diagnosis, helping you get back to your life. Previous Next. What is Scatter Radiation? What Does it Mean for Me as a Patient?

How do Technologists Deal With it? As dictated by the College of Physicians and Surgeons and the Alberta College of Medical Diagnostic and Therapeutic Technologists, the governing bodies for radiologists and technologists in Alberta, there are three ALARA safety measures to focus on: Time : Minimizing the time of radiation exposure will reduce the radiation dose.

Distance : Increasing the distance between the patient and the radiation source will reduce exposure by the distance squared. Shielding : Lead or lead-equivalent shielding for X-rays and gamma rays can block and reduce radiation exposure. Some examples of shielding include lead aprons, glasses, shields, and barriers. References Abrantes, A. What is Scatter Radiation. Secondary Scatter Radiation and Undercut Control.

Scatter Radiation. Physical Principles of Medical Imaging. Scatter Radiation from Chest Radiographs. Share This Story!