-term used to denote radiologic examination of nasolacrimal drainage system

Examination Procedure

This preliminary radiograph are taken to evaluate the paranasal sinuses

1. Waters
2. Caldwell
3. Lateral

• to expedite filming after the introduction of contrast medium, injection is carried out with patient seated before a vertical grid device
• patient may however be placed in supine position for introduction of medium and prone position for filming
• after anesthetizing the conjunctiva and puncta, physician dilates the punctum of the canaliculus to be injected
• then inserts the round-tipped lacrimal needle into the canaliculus.
• patency of the canals is tested by irrigating them with normal saline solution and if fund patent, examination is terminated
• immediately following the introduction of the contrast agent and withdrawal of needle, radiographs are taken in rapid succession in Caldwell, waters and lateral position
• same images are repeated at specified intervals to follow the progress of the medium though the channels.
• 7-10 minutes of post injection interval are taken for follow-up radiograph and again 15-20 minutes interval at which the medium will passed through the patient ducts and seen on the floor of the nasal cavity and on pharyngeal mucosa
• collateral side may be injected after the initial filming of the 1st side and its necessary to rotate head slightly (10-15º) away from the film in order to separate the shadow of bilaterally opacified ducts in lateral projection
• exposure factors used for routine paranasal sinus studies are satisfactory for the contrast studies of nasolacrimal duct system

Iodine

Iodine based contrast media such as Urografin or Omnipaque is used most commonly in radiology, due to its relatively harmless interaction with the body and it solubility. It is primarily used to visualise vessels, but can also be used for tests of the urinary tract, uterus and fallopian tubes.

Iodine contrast agents are used for the following:
- Angiography (Arterial Investigations)
- Venography (Venous Investigations)
- VCUG (Voiding Cystourethrography)
- HSG (Hysterosalpinogram)
- IVU (Intravenous Urography)

Barium

Barium sulfate is mainly used in the imaging of the digestive system. The substance exists as a water insoluble white powder that is made into slurry with water and administered directly into the gastrointestinal tract.

Barium contrast agents are used for the following:

- Barium Enema (Large Bowel Investigation) and DCBE (Double Contrast Barium Enema)
- Barium Swallow (Oesophagael Investigation)
- Barium Meal (Stomach Investigation) and Double Contrast Barium Meal
- Barium Follow Through (Stomach and Small Bowel Investigation)
- CT Pneumocolon / Virtual Colonoscopy

MR signal enhancing

This would include gadolinium for use in magnetic resonance imaging as a MRI contrast agent. In the 3+ oxidation state the metal has 7 unpaired electrons. This causes water around the contrast agent to relax quickly, enhancing the quality of the MRI scan.

Extracellular fluid (ECF) agents include products such as Magnevist, Prohance, and Omniscan. These agents are generally nonionic and a recent report, points out that the development of nonionic contrast agents for MRI has paralleled that for iodinated contrast materials. Ionic chelates are also hyperosmolar and some of their side effects may be attributed to this property. Gadodiamide (Omniscan, Winthrop Pharm.) is a nonionic complex with two-fifths of the osmolality of Gd-DTPA. Gadoteridol (Prohance, Squibb) is the third intravenous contrast agent on the market. It is a low osmolar, nonionic contrast as is Gadodiamide. Indications for use and efficacy are similar to the other agents.

Another class of contrast agents are Ultrasmall Supermagnetic Iron Oxide Particles. Small particles of ferrite used as paramagnetic contrast medium in MR imaging. These agents exhibit strong T1 relaxation properties, and due to susceptibility differences to their surroundings also produce a strongly varying local magnetic field, which enhances T2 relaxation to darken the contrast media-containing structures

Ultrasonography

Microbubbles contrast agents are used to aid the sonography, specifically echocardiograms, for the detection of a cardiac shunt. The bubbles are composed of tiny amounts of nitrogen or perfluorocarbons strengthen and supported by a protein, lipid, or polymer shell. The drop in density on the interface between the gas in the bubble and the surrounding liquid strongly scatters and reflects the ultrasound back to the probe. This process of backscattering gives the liquid with these bubbles a high signal, which can be seen in the resulting image.

The currently used CM in the x-ray imaging procedure can be grouped, on the basis of their osmolarity, to such which have a low osmolarity (LOCA) and such having a high osmolarity (HOCA). It should be noted that both have an osmolarity which is above that of the blood. Adverse side effects associated with CMs include such which result from the high osmolarity. The introduction of LOCAs, which are the new generation of CMs, was meant to counter some of these side effects. It should be noted that one big disadvantage of LOCAs is their high price-tag (about 5-10 times that of HOCA).

Some physicians suggest that nonionic, low-osmolality agents be used universally because fewer adverse reactions are associated with them. Nonionic agents should be used in patients who are at increased risk of adverse reactions. This group includes patients who had previous contrast reactions, or who have asthma, multiple allergies, or diseases that could be aggravated by contrast materials. Low-osmolar, nonionic agents should be used in patients known to have renal insufficiency. In addition, when a complete history is difficult to obtain and in patients who are concerned about the use of contrast material or are at risk for aspiration, low-osmolality agents should be considered.

Individuals subjected to procedures involving the use of CMs, are exposed to several hazards, depending on the CM used, including:

1. Hyperosmotic Damage:

Typically 100-200 ml of CM are injected into a total plasma volume of 5 liters within a period of several minutes. Cells such as endothelial cells, red and white blood cells, cells within the kidney, etc., are exposed to a hyperosmotic solution, reaching 200-2000 mOsm/kg at the site of injection, as compared to the osmolarity of the blood with its 300 mOsm/kg, giving rise to a hyperosmotic shock which may elicit related damages. In the following description the term “hyperosmotic CM” will refer to any CM having osmolarity higher than the blood osmolarity which is typically 300 mOsm/kg.

2. Iodine Specific Toxicity:

In an x-ray visualization procedure typically 30-40 grams of iodine (included within the contrast media) are injected into the blood within the period of 2-10 minutes. It should be noted that target visualization requires a minimum accumulation of 15-20 mg of iodine/ml in the target tissue and this is the reason that the initial iodine concentration in the CM is relatively high in the range of 300-420 mg iodine/ml.

3. Kidney Damage:

The iodine load to which the kidney is exposed and which it has to secrete is a potential cause for renal damage. It is generally believed today that 12% of all patients which are injected with an x-ray CM, encounter renal complications. A recent study shows that during cardiac catheterization procedure, 9% of low risk and 16% of high risk patients develop renal failure. Various studies made with CMs have shown that exposure of cells to x-ray CM causes the cell damages

Generally, before a contrast procedure is performed an ampule of antihistamine is already available just in case any adverse reaction may occur to the patient.

Patient Preparations
- let the patient empty the bladder completely

Materials
- CM – iodinated compound – 50 ml
- Sterile water – 200-300 cc
- Catheter
- Syringe
- Container
- Gloves

Procedure
1. scout film – pelvis AP
2. insert catheter to the urethra
3. introduction of diluted CM (up to 200 cc)
4. remove catheter
5. position px 35 degrees oblique facing the cassette/film
6. outer leg is slightly flexed
7. take exposure (CR at the level of symphysis pubis) while the patient is voiding

Contraindications
- suspected colonic perforation
- patients at risk of intraperitoneal leakage (e.g. severe colitis, toxic megacolon)
- recent severe disease (MI, CVA)

Indications
The purpose of a barium enema is to demonstrate the anatomy and morphology of the large intestine. The large intestine frames the abdomen and is divided into six sections. These include the rectum, sigmoid colon, descending colon, transverse colon, ascending colon, and cecum.

A barium enema may be performed for a variety of reasons, including abdominal pain or a change in bowel habits such as diarrhea or constipation, as well as a change in the caliber (size) of the stools. This exam is also requested when parasites, blood, mucus, or pus are found in the stools. Occult (hidden) blood found in the stools and anemia may be an indication of intestinal bleeding due to ulcers, inflammatory disease, or a cancerous lesion. Doctors may also order this exam as a screening tool for patients with a history of polyps (pre-cancerous growths extending outward from a mucous membrane) or a family history of colorectal cancer.

A barium enema may also be requested when the large intestine was not completely visualized during a colonoscopy (examination of the large intestine with a fiber-optic tube) or when a sigmoidoscopy is done, which only partially visualizes the colon. Sometimes a barium enema may be used as a treatment for intussusception (telescoping of one section of the bowel into another causing obstruction). This is a rare disorder occuring most often in young children, but when it occurs immediate action must be taken.

A barium enema may also be done to evaluate the remaining colon on colostomy patients. The barium is injected into the stoma (external drainage opening in the abdominal wall) instead of the rectum. A barium enema may be done if obstruction, perforation, or fistula formation is suspected.

Patient Preparations
- Fasting ( 6-8 hrs NPO, no breakfast)
- Laxatives (4 tablets dulcolax at bedtime, 1 suppository at early in the morning)

Materials
- CM – BaSO4
- Enema can
- Rubber tubing
- Rectal catheter or foley catheter
- Gloves
- Plaster
- Mask (like Asbestos Masks)

Method
A. Single Contrast
1. Scout film, abdomen AP (CR at the level of iliac crest)
2. wearing of gloves
3. px assume Sim’s position
4. insertion of rectal catheter (3-4 inches)
5. anchor the tube with the use of balloon tip foley catheter or plaster for straight rectal catheter
6. introduction of CM
7. follow retrograde flow with fluoroscopy
8. do spot film
9. when the die has reached the ileo-cecal region do the following spot films:
a. Abdomen AP, PA, LPO, RPO, RAO, lateral, prone, cross-table
10. catheter removal
11. let px deficate and do the post evacuation exposure (abdomen AP)

B. Double Contrast
1. Same procedure from steps 1 – 5
2. reinsert tubing with air pup and infuse negative CM (air). Infusion is stopped when the px feels fullness, then catheter is removed
3. expose abdomen AP

Note: Height of the enema can is approximately 2 feet from the anus

Complications:
1. Those who have a rapid heart rate, severe ulcerative colitis, toxic megacolon, or a presumed perforation in the intestine should not undergo a barium enema.
2. The test can be cautiously performed if the patient has a blocked intestine. Gastrograffin, an iodine-based contrast, will be used instead of the barium in case emergency surgery is needed following the barium enema.