31.Videofluorography Overview, Necessary Supplies, and Contrast Agents

Explanation

Videofluorography of swallowing (VF) is a detailed examination used in dysphagia rehabilitation, along with videoendoscopy (VE), to verify screening test results, check the progress of training, and change the physical properties of food. It provides various information needed for rehabilitation, including the presence or absence of aspiration. So, we should have an adequate understanding of VF before starting dysphagia rehabilitation.

Explanation

Naturally, healthcare professionals providing dysphagia training to patients need a firm understanding of the swallowing behaviors of dysphagic patients.
VF is performed to assess swallowing function by fluoroscopically examining oropharyngeal motility. For this purpose, we evaluate the transport of a contrast-enhanced food bolus and the way it passes through the oropharynx in order to indirectly assess the kinetics of oropharyngeal soft tissues. The air contained in the pharynx and larynx serves as a negative contrast medium and can be as important a marker as positive contrast agents, such as barium and iodine contained in a food bolus.
Because the pharyngeal swallow is a very quick, lasting less than 1 s, video recording (30 frames per second) is essential for assessing the kinetics of the tissues involved. Note that VF is a functional examination and if we suspect any tumor or other diseases, we should promptly refer patients to an otolaryngologist or other specialists.

Explanation

VF is performed for diagnostic or therapeutic purposes, as indicated by 1 and 2 here, respectively. It is, needless to say, important to clarify the purpose of the examination and perform an adequate examination to accomplish that purpose. At the same time, we should remember that VF involves radiation exposure and give due consideration to minimizing exposure for both the patient and examiner. VF for therapeutic purposes involves the use of compensatory postures (eg, swallowing with the head turned to the right or left, swallowing with the head bent forward, and postural change) and changing the physical properties of food (eg, change the type of food and adding a thickening agent). VF performed during the course of training, as indicated by 3 here, provides the information needed to, for example, evaluate the effectiveness of training, change the physical properties of the food the patient eats, and modify the treatment plan.

Explanation

The equipment required for VF includes 1) a fluoroscopy system, 2) a video recording device, 3) an audio recording system, 4) an examination chair, and 5) an observation system.

Explanation

There are various types of fluoroscopy systems with different features. The most common type is a stationary-type system (left). Older systems tend to have a base bulging from the floor to immobilize the system, which can interfere with the use of an examination chair or a wheelchair and often requires adjustments to stabilize the base, such as flattening the floor surface. Also, the arm supporting the X-ray tube and the arm for holding the stomach during gastrofluorography often interfere with patient positioning. These factors affect the degree of freedom of the examination and we should consider these aspects carefully when purchasing a new fluoroscopy system or examination chair. Necessary adjustments should be made onsite especially when performing examination in anteroposterior projection, because of the difficulty examining patients in an inclined chair due to the narrow space between the X-ray tube and the table and the trolley for the examination chair hitting against the table. The patient should be positioned as far as possible from the X-ray tube and as close as possible to the image intensifying tube (located on the table). Moving away from the table may produce a magnified image that doesn't cover a sufficient examination range.
2.3. The movie and audio recording systems use media such as videos and DVDs. When inputting images from the monitor of the fluoroscopy system to the recording device, it's usually necessary to separately input the audio data captured with a microphone through an amplifier to the recording device. Once the entire system has been assembled, we must actually test the operation of the system to make sure that both sounds and images are recorded properly.

Explanation

4. Several types of examination chair are available from Japanese manufacturers. On the right is a chair imported from the United States. When performing VF, for example, in patients placed in a 30° elevated supine position, it's likely that the chair will hit the system because of the narrow space between the X-ray tube and the table, making it difficult to take images. Adjustments may also be needed when examining patients in wheelchairs because metal parts of the chair, such as a metal frame, can interfere with examination in anteroposterior projection.
5. An observation system consisting of a television monitor allows for images to be shared among team members. These images can usually be saved on a computer for analysis. Time data generated by videos or computer software are also available, although their accuracy can vary depending on the system used and should be verified. The video recording systems used in Japan employ the National Television System Committee (NTSC) format, which has 525 scanning lines and records 29.29 frames per second. By comparison, the Phase Alternating Line (PAL) format used in Europe has 625 scanning lines and records 25 frames per second. Videos can be played on a machine with a slow-motion or stop-motion function to obtain time data assuming that each frame lasts about 1/30 s. In terms of scanning lines, rapid advancements have been made in Japan, including the recent generalization of the high-resolution digital television system.

Explanation

The term "videofluorography" itself indicates that video recording is usually used in this swallowing examination. With video recording, the frame rate is automatically maintained at 30 frames per second. In contrast, digital fluoroscopy systems provide an option to record smaller numbers of frames.

Explanation

Contrast agents can be divided into positive and negative ones; the former absorb X-rays to make the object distinct from the surrounding area (make it visible) and the latter, such as air, allows X-rays to pass through to make the area distinct from the surrounding area. The term "contrast agents" usually means positive contrast agents though. Elements with higher atomic numbers have higher X-ray absorbance. Gastrographin^TM, a contrast agent containing barium (Ba:56) and iodine (I:53), is therefore commonly used in gastrofluorography but should be avoided in VF due to its pneumotoxicity. In terms of taste, GastrographinTM is very bitter. Iopamidol, a nonionic iodine-based contrast agent, tastes slightly sweet initially but bitter later. Iotrolan (Isovist^TM) is very sweet. Barium-based contrast agents used for such purposes as gastrofluorography are formulated to be like a drinking yogurt, but they taste rather powderish when diluted. Given these different features of contrast agents and their different tastes depending on the examination setting, examiners should taste each contrast agent before using them. Iodine hypersensitivity is rare but can lead to shock. Examiners should therefore obtain sufficient information by history taking and from other sources.

Explanation

A large-scale investigation of adverse reactions, conducted in Japan, was reported by Katayama et al. in 1991. The imaging methods used were intravenous urography, computed tomography (CT), and digital subtraction angiography (DSA) with intravenous contrast injection; both ionic and nonionic (iopamidol and iohexol) contrast agents were used. Logistic regression analysis revealed 4 risk factors: use of ionic contrast agents, history of adverse reaction, asthma, and cardiac disease.

1. Comparing ionic and nonionic contrast agents, the odds ratio was 5.61 (95% confidence interval [CI]: 4.13-7.63).
2. Comparing with and without a history of adverse reactions, the odds ratio was 4.68 (95% CI: 3.16-6.92).
3. Comparing having asthma and having no history of allergy, the odds ratio was 10.09 (95% CI: 6.36-16.02).
4. Comparing with and without the presence of underlying cardiac disease, the odds ratio was 3.02 (95% CI: 1.94-4.69).

A 2005 notification from the Ministry of Health, Labour and Welfare states that barium sulfate is contraindicated in patients with a history of hypersensitivity to barium sulfate. Also, caution must be exercised to prevent gastrointestinal perforation.

Explanation

Here we see detailed descriptions of adverse reactions to contrast agents. Be sure to carefully read the precautions and warning statements of the contrast agent you are going to use.

If patients present with clinical features such as hives, feeling unwell, pallor, cold hands and feet, choking, breathlessness, and difficulty breathing, appropriate treatment is required. The following is a list of measures to prevent gastrointestinal perforation (intestinal obstruction and peritonitis). Although the effect of an oral contrast agent is often mild because of the small quantity, outcomes may be more severe in elderly patients, so they need to be watched carefully.

1. Check for the presence/absence of constipation
2. Check for the need for a laxative
3. Ensure adequate hydration after the examination
4. Ensure regular toilet visits even without the urge to defecate
5. Check for excretion of barium in feces, and the absence of constipation and abdominal pain.
6. Be aware that barium excretion becomes more difficult at a later time.

Explanation

Here we see different types of contrast agents. Iodine-based contrast agents are divided into ionic and nonionic types. Nonionic types are generally less pneumotoxic and are more commonly used in VF.
Barium sulfate is also commonly used, but it can't be used for the examination of swallowing of tea or water at the concentrations used for gastrofluorography because these agents are formulated as a viscous and thick liquid to help barium attach to the gastric wall. Most barium-based contrast agents are formulated at concentrations higher than 100 W/V% and need to be diluted 1:2 to 1:5 with drinkable water before use.

Iopamidol iohexol

Explanation

Keep in mind that deaths due to aspiration of contrast agents have been reported.

Explanation

Experimental results on the pneumotoxicity of contrast agents have been reported and serve as the rationale for the current use of nonionic contrast agents in VF.

Explanation

Most foods are non-contrast enhancing and can't be seen on X-ray images. Therefore, a contrast agent needs to be added to each test food. For nonionic contrast agents, such as iopamidol and iohexol, generic versions are available and are more commonly used than the originals due to lower cost.

The taste and smell of food will be affected by adding a contrast agent. For example, barium sulfate suspensions are often yogurt-flavored and have an intense yogurt-like smell. However, Gastrografin, an ionic iodine-based contrast agent, is quite bitter, and many nonionic agents (eg, iopamidol) also leave a bitter aftertaste. An exception is Isovist, which is extremely sweet. Because each contrast agent has a different flavor, each test food must be tried before use.

When making a suspension, add barium sulfate to a fluid to make a final concentration of >= 30 W/V%. When added to food, the weight of barium tends to make it settle at the bottom, so the final concentration needs to be >= 40 W/V%, otherwise radiopacity will be inconsistent. It is recommended that the test food itself be tested before use by X-ray to confirm its intensity and consistency in radiopacity. An iodine-based contrast agent, Oypalomin 300 for example, can be diluted 1:5 for imaging.

Explanation

These are examples of test foods containing contrast agents. Barium jelly is used in many hospitals. For more detailed recipes, see the Dysphagia Rehabilitation journal and the "Procedure of Videofluorography (detailed version)" section of the website of The Japanese Society of Dysphagia Rehabilitation.

Barium sulfate suspension (concentrated: 120%-160%) Prepare a barium sulfate suspension (30%-40%) by diluting the concentrated suspension (120%-160%) with water. Thickener-added barium sulfate suspension Adding a thickener makes the texture of a barium sulfate suspension (30%-40%) similar to that of water or soup containing the thickener. Change the amount of thickener to adjust the viscosity as needed. Jelly Ingredients of jelly are barium sulfate (50 g), water (100 mL), gelatin (2 g), and sugar (20 g). To make a slightly hard agar jelly, replace gelatin with agar powder (1.5 g); when crushed, this will become like particles of rice grains. Yogurt or pudding A suitable amount of a contrast agent can be added to yogurt or caramel custard before use. Adding the contrast agent makes the texture of yogurt or caramel custard slightly muddy. Cookie This is the best test food to assess the patient's ability to process food in the oral cavity. Coat commercially available cookies with a concentrated barium sulfate suspension. Or make cookies from the following ingredients and keep them in the freezer until use: butter (125 g), sugar (110 g), egg yolk (1), flour (100 g), and barium powder (25 g). Medication Barium sulfate is placed in capsules, inserted in a medicine sheet, and solidified. Or, barium powder is used as a powdered drug.

References

1. Katayama H, Yamaguchi K, Kozuka T, Takashima T, Matsuura K, Nakata H, Tanabe M, Brunger C.Full-scale investigation into adverse reaction in Japan. Risk factor analysis. The Japanese Committee on the Safety of Contrast Media.Invest Radiol. 1991 Nov;26 Suppl 1:S33-6; discussion S40-1.
2. Gray C, et al: Aspiration of high-density barium contrast medium causing acute pulmonary inflammation -Report of two fatal cases in elderly women with disordered swallowing-. Clinical Radiology, 40:397-400,1989.
3. Trulzsch DV, et al: Gastrografin-induced aspiration pneumonia: a lethal complication of computed tomography. South Med J, 85:1255-1256, 1992.
4. Ebata T et al:A case of aspiration pneumonia by Gastrografin.Yachiyo hospital bulletin 13:10-11, 1993.
5. MacAlister WH,et al: The effect of some contrast agents in the lung: An experimental study in the rat and dog. Am J Radiol,140: 245-251, 1983.
6. Ginai AZ, et al: Experimental evaluation of various available contrast agents for use in the upper gastrointestinal tract in case of suspected leakage. Effects on lungs. Brit J Radiol, 57: 895-901, 1984.
7. Miyazawa T,et al: Effect of water-soluble contrast medium on the lung in rats comparison of iotolan, iopamidol, and diatrizoate. Invest Radiol, 25: 999-1003,1990.
8. Standard procedure of Videoflourography (detail version) (in Japanese)The Japanese Journal of Dysphagia Rehabilitation 18 (2):166-186, 2014.