Radiographic challenges for feline patients (Proceedings)

1) Improving Quality

a) Improvements in Film Radiography

i) Dark room techniques

(1) Pay attention to light leaks

ii) Processing

(1) Hand processing can give very good results if it is done properly

(2) Regular fluid changes are essential for hand or automatic processing

iii) Power of the machine

(1) 300 ma is adequate for canine use

(2) 100 ma is adequate for feline use

iv) Film

(1) Cheap film is cheap because the amount of silver is reduced. That is the most expensive part of the film.

(2) Reducing the silver content reduces the quality.

v) Cassettes and screens

(1) The screens are the expensive part of this pair.

(2) Cassettes are often sold because the screens are worn out.

(a) This occurs with use or with time. Approximately 5 years is the life of most screens.

(b) 3M Animal Health has screens and film made to match.

(i) I recommend Ultra Detail Plus with 3M screens.

(ii) They have a Buy One-Get One Free (screens and cassettes) offer with a $1000/yr. contract on film.

b) Digital Radiography

i) It works like a digital camera; there is no film.

ii) Three levels of technology: CCR (Yugo), CR (Toyota), DDR (Lexus)

iii) The image is created in a matter of seconds (10 seconds with a DR system).

iv) The image can be manipulated to account for over or under exposure.

v) Retakes can occur in seconds with almost no incremental cost to do so.

vi) DR technology is the greatest improvement in existing technology since I have been in practice (34+ years).

vii) DR (Sound Technology)

(1) The most expensive

(2) The highest quality image

(3) In the least amount of time

viii) It should be cost effective for a 3-4+ doctor small animal practice; cost effective for many 2 doc practices.

c) Technique Adjustment: Overexposed vs. Underexposed

i) Thorax: The goal is less contrast

(1) If underexposed: Increase kV

(2) If overexposed: Decrease time

ii) Skeleton: The goal is more contrast

(1) If underexposed: Increase time

(2) If overexposed: Decrease kV

iii) Abdomen: The goal is balanced contrast

(1) If too much contrast: Increase kV

(2) If too little contrast: Increase time

2) The Skull

a) Goals

i) To identify the structures commonly involved in nasal, sinus, tympanic bulla, and nasopharyngeal disease

ii) To understand how to position the cat for the views needed to visualize these structures.

b) Open Mouth VD

i) To view the nasal cavity without superimposition of the mandible.

ii) The hard palate is positioned parallel to the table top.

iii) The mandible can be opened 90 degrees when the cat is under anesthesia (not true of dogs).

iv) Gauze strips can be used to achieve proper placement without having one's hands in the primary beam.

c) True Lateral

i) To view the frontal sinuses

ii) If normal, there is an air density filling the frontal sinuses.

d) Lateral Oblique

i) To view one tympanic bulla without superimposition by the other.

ii) Rotate the skull so the bulla of choice is ventral.

e) Rostrocaudal (Skyline)

i) To view the frontal sinuses and tympanic bullae.

ii) Position the head so the center of the beam cuts through the sinuses (dorsal to the eyes).

iii) The cat is in dorsal recumbency with the nose pointed at the x-ray beam.

iv) Gauze strips can be used to achieve proper placement without having one's hands in the primary beam.

f) Structures That Should Be Identified

i) Nasal cavity (Open Mouth VD)

ii) Frontal sinuses (True Lateral and Rostrocaudal)

iii) Soft palate (True Lateral)

iv) Nasopharynx/oropharynx (True Lateral)

v) Tympanic bullae (True Lateral and Skyline)

g) Tips About Nasal Disease

i) Unilateral disease is usually due to neoplasia.

ii) Nasal neoplasia often causes lysis or distortion to the nasal planum.

iii) When the age of onset is 10+ years, it is strongly suggestive of neoplasia.

iv) Epistaxis does not correlate as strongly with neoplasia as in dogs.

v) Asymmetry of the nasal planum is usually due to bony destruction and associated with neoplasia.

vi) Radiographs cannot be used to definitively distinguish neoplasia, infection, and inflammatory polyps.

vii) Masses in the nasopharynx create loud strider and usually do not have nasal discharge or chronic sneezing.

3) Delayed Diaphragmatic Hernia

a) Trauma occurs.

b) The diaphragm has a small tear.

c) Initial radiographs do not reveal clear evidence of a diaphragmatic hernia.

d) In the next 24 hours, abdominal organs migrate into the chest.

e) Then, there is onset of dyspnea.

f) Recommendation: Re-ray anytime dyspnea occurs.

g) A celiogram can be diagnostic for DH

i) Ten ml of MD 76-R (replaces Hyapaque) or iohexol is injected IP; the cat's rear quarters are elevated; a lateral view is taken looking for contrast material in the pleural space.

4) GI Study with Barium

a) Indications

i) Acute or chronic vomiting

ii) Suspected GI foreign body

iii) Suspected GE obstruction

iv) Chronic small bowel diarrhea

b) Bonus benefit: Barium is soothing to the GI tract.

c) Mistakes

i) Inadequate barium: use 5 ml per pound; administer with an orogastric tube.

ii) Failure to take enough views: always take VDs and laterals

iii) Failure to realize that vomiting may originate from the stomach to the rectum.

iv) Failure to take enough films

(1) Every 15-30 minutes until most of the barium is in the colon.

(2) Vomiting: 0, 15, 30, (45), 60 minutes then q30m until most of the barium is in the colon.

v) Failure to follow the Rule of Three

(1) A "lesion" must be seen 3 times to make it valid.

(2) You must take enough films to do that.

d) "Fuzzy Borders" in the Small Bowel

i) Indicates enteritis

ii) Segmental enteritis is present in:

(1) Inflammatory Bowel Disease

(2) Fungal Disease

(3) Neoplasia

(4) Normal Cats.

iii) May be present in some normal cats.

e) Improvements

i) Exposure: Add 5-10 KV to the normal abdominal setting.

(1) The goal is to see "only" the barium; the soft tissues of the abdomen are not important.

(2) Overall better technique: 3M system or digital radiography

(3) For sedation

(a) Acepromazine: 0.2-0.4 mg/kg IM or SC OR

(b) Ketamine (2.7 mg/kg IM or SC) + diazepam (0.1 mg/kg IM or SC) combined in one syringe.

f) Alternatives to barium

i) Omnipaque 240

(1) Designed for myelograms

(2) Not irritating to the peritoneal cavity: Use if GI rupture is suspected.

(3) Can be dilutes 1:1 with water or saline due to expense (~$1.00 per ml)

(4) Transit time through the gut: ~ 1 hour.

ii) Iodinated compounds (Hyapaque)

(1) Designed for IV use

(2) Not irritating to the peritoneal cavity: Use if GI rupture is suspected.

(3) Cheaper than Omnipaque.

(4) Absorbs fluid as it passes through the GI tract because it is hypertonic

(a) The degree of visualization diminishes as it traverses the GI tract.

(5) Transit time through the gut: ~1 hour.

5) Read it All

a) Failure to read all of the radiograph can result in serious oversights.