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What Parents Should Know About Radiation Safety and Videofluoroscopic Swallowing Studies (VFSS)

 

By: Nancy B. Swigert, M.A., CCC-SLP, BCS-S

Board Certified Specialist in Swallowing and Swallowing Disorders

and

Vesna Martich Kriss, MD

Pediatric Radiologist, Baptist Health Lexington

 

It has been recommended that your child undergo a video fluoroscopic swallowing evaluation, often called a modified barium swallow, to assess the pharyngeal phase of the swallow. This radiologic procedure exposes your child to x-rays which raises safety questions about the study. Here are some things parents should know about radiation safety and the video fluoroscopic swallowing exam (VFSS).

When is a VFSS indicated?

A child should undergo a VFSS when the treating providers (speech-language pathologists, pediatrician, other medical specialists) need information about the safety and efficiency of the pharyngeal phase of the swallow. The VFSS is not the most appropriate examination to assess the oral phase of the swallow. The decision to proceed with a VFSS should be made when the benefits outweigh any risks. Questions the parent can ask the speech-language pathologist or physician who is recommending the study:

 

  • What signs/symptoms of pharyngeal dysphagia does my child present with that require a VFSS?
  • Are there any other alternative examinations that might provide the information needed?
  • Will my child be able to participate and cooperate enough for the exam to be successfully completed?

 

What are the dangers of exposure to radiation?

Radiation is around us every day from the sun and other sources. People who live at high altitudes are exposed to more radiation than people who live at sea level.

Radiation can damage tissue, particularly if the child is exposed to multiple X-rays and over large areas of the body. Continuous x-ray (as in fluoroscopy) exposes the child to more radiation than a single x-ray (like a chest x-ray). A CT exam exposes the child to significantly more radiation.

 

How much radiation exposure can be expected during a typical swallowing study?

The amount of radiation resulting from fluoroscopic procedures is highly variable. The total patient dose from a fluoroscopic clinical exam is dependent upon how much radiation is used to generate each image and the length of time the child is exposed.

The goal is to obtain adequate images over the appropriate amount of time to answer the diagnostic question. The dose should be “as low as reasonably achievable” (ALARA). Optimizing the radiation dose associated with each image is an important part of the process needed to insure that the patient’s radiation dose is ALARA. However, if the exposure is lowered to the point that accurate and complete results cannot be obtained, then the exam is of no benefit to the child.

 

How can the risks be diminished?

 

Before the exam begins:

  • The child’s reproductive organs should be protected with a lead shield.
  • The child should be carefully positioned before the study begins to increase the chances that the child’s oropharynx can be accurately observed.
  • Depending on the age and child’s abilities, the speech-language pathologist, radiology technologist and radiologist can explain the procedure to the child and let them explore the room and the equipment (e.g. the radiology technologist could turn on the fluoroscopic locator light beam and explain that the equipment is “like a big camera”). This may make the child more comfortable and ready to participate fully once the study begins, eliminating unfortunate interruptions due to fear.

 

Correct operation of the machine by properly trained operators reduces the duration of time of fluoroscopic radiation.

 

  • The operator should be sure the image intensifier is in the correct position before fluoroscopy is turned on. This can be done using a fluoroscopic locator light beam and not active fluoroscopy.

 

  • Turning fluoroscopy off when the child is not engaged in active assessment of swallowing is another essential tool that significantly reduces dose. For example, if the effect of fatigue needs to be evaluated, the child’s swallow can be observed with active fluoroscopy for several swallows. Then, with fluoroscopy off, the child can continue to drink to the point that fatigue might be expected to have an impact on safety and efficiency of the swallow. Then active fluoroscopy can begin again.

 

  • Field of view:   Appropriate magnification is essential for proper visualization. However, if the operator utilizes extreme magnification to produce an ever smaller field of view, the radiation dose increases. Therefore, extreme magnification should be avoided when possible.

 

  • Collimation – If the image displays more than what needs to be observed, the operator can collimate the field of view to include only what needs to be seen, again reducing unnecessary radiation dose

 

  • Anti-scatter grid – this grid should be removed for pediatric patients

 

Pulsed fluoroscopy vs. continuous reduce exposure?

 

Historically, fluoroscopy was performed in the continuous mode. Whenever the fluoroscopy pedal was depressed, a continuous x‐ray beam was produced. Since 30 fluoroscopic images were created per second, the duration of each image frame was 33 msec (1000/30=33).

Most state‐of‐the‐art fluoroscopic equipment today offer a much improved alternative to continuous fluoroscopy, called pulsed fluoroscopy. When the fluoroscopic foot pedal is depressed, the x‐ray beam is pulsed by the machine or turned “on and off” at a selected pulse rate. If the proper parameter settings are selected with respect to the size of the patient examined during pulsed fluoroscopy, the image quality can be significantly improved and most importantly, the radiation dose to the patient can be significantly lowered. Pulsed fluoroscopy can effectively be used, for example, in gastrointestinal studies.

Marked reduction in frame rates, however, can result in loss of some temporal resolution. This is significant during a swallowing study, which is assessing a very quick movement of multiple structures in the mouth and throat. The pharyngeal swallow lasts only about one second and capturing fewer images/second in a pulsed mode can mean that an aspiration event might be missed (Cohen, 2009). The continuous mode allows the speech-language pathologist to determine the reasons for aspiration or other pharyngeal problems, like significant residue. Therefore, usage of continuous fluoroscopic mode can be considered in conjunction with routine pulsed fluoroscopy during a VFSS. The radiologist should switch to the pulsed mode alone for assessment of the esophagus, small bowel, etc. if those studies are being completed in the same session as the VFSS.

Consider this analogy. You are riding in car and watching the road ahead with your eyes wide open (continuous). You see a bird fly across the road. Then you begin rapidly blinking your eyes (pulsed) and the bird darts across the road during one of the pulses in which your eyes are closed. You may miss seeing the bird entirely, or see only the tail of the bird as it flits out of sight. As a result, prudent usage of continuous fluoroscopy in conjunction with routine pulsed fluoroscopy could be considered.

 

How often should a VFSS exam be repeated?

The swallowing exam should only be repeated when the exam is necessary to make decisions about managing the child’s pharyngeal dysphagia. At the time of the first exam, the speech-language pathologist completing the study should specify indications for a repeat exam. For example, the SLP might state “Do not advance liquids to thin without a repeat instrumental exam” or “When child is ready to advance to solids, a repeat instrumental exam is indicated to assess safety of swallow with solids”. Statements such as that will guide the timing of the next study.

 

However, if no new information will be gained by repeating the instrumental, the SLP should indicate that as well, with statements such as “Can safely advance child’s liquid and solid diet without another instrumental study”.

 

Repeat instrumental exams are also indicated if there is a significant change in the child’s overall health and medical status. If the child did not swallow anything safely on the first VFSS and their medical status improves significantly, another exam might be indicated before beginning oral intake.   Conversely, if a child’s medical condition deteriorates and it appears that the swallowing skills have also deteriorated, then a repeat exam might be recommended.

 

How long should the study last?

 

There is no magic number of minutes to indicate how long the study should last. One study found that studies lasted on average 2 ½ minutes. The study should last as long as needed to gain the answers to the diagnostic questions, while still using a dose as low as reasonably achievable.

 

 

 

References:

  • Hiorns MP, Saini A, Marsden PJ, A review of current local dose-area product levels for paediatric fluoroscopy in a tertiary referral centre compared with national standards. Why are they different?, BJR, 79 (2006), 326-330
  • Brown PJ, Johnson LM Silberberg PJ, Thomas RD, Low dose, high quality pediatric fluoroscopy, Medica Mundi 45/1 March 2001
  • Tapiovaara MJ, Sandborg M, Dance DR. A search for improved technique factors in paediatric fluoroscopy. Phys Med Biol. 1999 Feb;44(2):537-59
  • B Hansson, T Finnbogason, P Schuwert J Persliden: Added copper filtration in digital paediatric double-contrast colon examinations: effects on radiation dose and image quality. Eur radiol 7 (1997) 1117-1122
  • Cook, V., Radiation protection and quality assurance in paediatric radiology, Imaging, 13 (2001) 229–238.
  • Strauss, K.J. and S.C. Kaste, The ALARA (as low as reasonably achievable) concept in pediatric interventional and fluoroscopic imaging: striving to keep radiation doses as low as possible during fluoroscopy of pediatric patients‐‐a white paper executive summary. Radiology, 2006. 240(3): p. 621‐2.
  • Food and Drug Administration – http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/ucm298899.htm
  • Can we use pulsed fluoroscopy to decrease the radiation dose during video fluoroscopic feeding studies in children? Cohen, M.D. Clinical Radiology , January 2009 Volume 64 , Issue 1 , 70 – 73
  • Radiation doses to children during modified barium swallow studies. Weir, K.A., McMahon, S. M. Long, G., Bunch, J.A., Pandeya, N., Koakley, K.S., Chang, A. B., Pediatric Radiology; March 2007,Volume 37, Issue 3, pp 283-290

 



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