Dose Regulation in a Vascular Lab Environment

If you have ever worked in Radiology, you have walked past a portable X-ray machine with the exposure switch cable hanging to the floor. The technicians using the portable pull the cable as far as they can when taking X-rays to avoid getting radiated. However, in a vascular lab, the surgeon and nurses are standing tableside performing surgery with the gantry right next to them. What safeties are there to prevent over-radiation of the patient and the technicians, and in what ways can the system help regulate dose? The term ALARA (As Low As Reasonably Achievable) comes into play and will be broken down throughout this article.  

Collimation 
While performing Fluoroscopy and acquisitions (Cine), the user can use collimation to reduce scatter radiation. The collimator filters the stream of rays coming from X-ray tube, limiting the beam of X-rays. By “collimating down”, the technician can view just the part of the body being worked on to reduce scatter radiation and radiation in the surrounding environment while increasing contrast of the image for better image quality. When you collimate down, the entrance skin dose rises because the image is darker, and the DAP can be reduced greatly.  However, with collimation, less of the patient is exposed to radiation, reducing overall patient dose. The blades are made of lead, which completely blocks radiation, narrowing the field of view to the anatomy needed. This focuses the radiation and increases the clarity and depth, so the image does not have “fog” or white space in the image.  

Use of Fluoroscopy vs. Cine 
The best way to regulate dose in a vascular lab is to use best practices with using Fluoroscopy versus Cine. Regardless of which is being used, the patient should be closer to the detector and not beyond the isocenter.  By moving the detector close to the patient, you reduce patient skin dose and increase radiation received by the detector, resulting in better image quality. Cine should be used sparingly, as it can produce up to 15 times more radiation than fluoroscopy. With the invention of “Last Image Hold” option it makes using fluoroscopy a much safer alternative.   It allows the user to review the last flouroscopy run as long as necessary to perform the next steps in surgery. There is also an option for pulsed fluoroscopy which is used uses small millisecond pulses and can be varied by frame rate. 

Dose monitoring 
Monitoring dose during surgery for the patient and staff is important. For the patient, this is done electronically. DAP (Dose Area Product) comes from an ionization chamber mounted onto the collimator inside of the tube cover. This is an important number to ensure there are no stochastic effects. The other concern to patient safety is PSD (Peak Skin Dose), which is controlled by the operator keeping an eye on air kerma levels. The number considers angulation of the gantry angles and table position. Air kerma acts as a real-time safety indicator for the operator and staff. There is a dose structured report that can be used to help improve procedures.   It should be noted that measuring Air Kerma and DAP is not perfect and doesn’t always take into effect the physicians use of the system, table and positioning angles when displaying, among other factors.  The trick is pre-planning and using ALARA.  

During procedures, staff wear dosimeters on the outside of the lead aprons, as well as under the lead apron. The dosimeter on the outside of lead apron helps estimate the dose that goes into exposed skin. The dosimeter worn under the apron is used to estimate the operator’s effective dose. There is a calculation made to determine the radiation absorbed, which is monitored throughout the year to calculate operator risk.  

Lead Blockers 
Lead blockers are used to reduce radiation from staff and the patient. There are a few different pieces that are mainly used to help regulate the dose exposure. The staff can put a lead blocker over the patient areas where surgery is not being performed. Generally, the lead blocker will go underneath the patient to block X-ray coming from the tube that is usually below the patient table. There are also a few options for lead shields, some hang from the ceiling and others roll on a stand, blocking all radiation for the user behind it. The tableside also can have a swinging lead shield to block the user’s legs from radiation. There are also lead shields that staff wear. Lead aprons can be worn to protect all vital organs. A thyroid shield is also worn to protect the neck area, while lead shield glasses are worn to protect the eyes. There are also lead shields that can be worn on the head and hands. The use of lead blockers combined with dosimeter badges worn by everyone working in the surgery room can help protect everyone from too much radiation exposure over time, as well as improving radiation reduction practices.  

Conclusion 
Dose regulation is an incredibly important factor for anyone who works in Radiology spaces or being treated in one. Knowing some steps to reduce dose will prolong your life and others, as well as reduce chances for side effects. By remaining dedicated to adhering to best practices, Avante strives to surpass our customers' expectations, enabling them to deliver the utmost level of care to their patients. As we continue to evolve and innovate, we will remain steadfast in our commitment to quality and safety, and we are proud to have the best industry experts supporting our mission.