----start radio.lec.05.07.97---

dr biery
again
yippee-ti-yi-yi-yay, kama-ti-yippee-yi-yay.

there is a dilemma. someone asked dr b to put copies of the last two 
exams in the library. for 15 yrs, the exams have NOT been handed back 
after the course, therefore, no students should have any exams from the 
past 15 yrs, at all. there are not many things that have changed since 
1896 when xrays were discovered. you find faculty writing tricky 
questions because you have access to old exams. the faculty does not want 
us to have back exams.  but some people allegedly do have exams.  but the 
exams have not been turned back to students, he says. in some schools, 
people are NOT allowed to look at old exams.  Kirsten is asking if we can 
get some sample questions. Dr B says if you read the notes, you cannot 
fail. will be multiple choice, T/F. he wants to know if anyone has access 
to exams, though, even though "not possible" - shoudl tell him. then will 
make test essay type, and will put exams in the library.
know general characteristics of xray tube and rays. know relative 
densities, etc.
hopefully won't go to many slides this year. will simply ask questions 
verbally.

example question:
on this slide, which of the following is identified: caudal vena cava, 
esophagus, aorta, or axial musculature? 
now how can you study for that?

other questions: if i double the mAs, what happens to density and 
contrast?

CONTRAST STUDIES:
we were talking about problems you can have with contrast studies, eg air 
embolism, room air causing embolus in cats with hematuria. contrast media 
rxn to iodinated contrast - you could put animal in complete renal 
shutdown, shown by persistent nephrogram and no entry of contrast into 
collecting duct. and if no kidney is visualized at all there's a prerenal 
problem. absence of visualization of kidneys bilat probably unrelated to 
kidney. if one visualized, one has a problem. if doens't show up in 
collecting duct, probs.

common complication of contrast using iodinated contrast is vomiting. if 
you give IV bolus to dog, will almost always gag/retch. but this isn't 
seen, animal usually anesthetized. in people, over half the rxns to 
contrast are related to psychological thing. you signed your consent 
form, you could die, people get anxious. higher probability of 
radiologist having rxn probably because they know more about what CAN 
occur! huh. ignorance is bliss? so the rxn rate is lower in vet med. can 
get seizures. can get vomiting but rare due to anesth.
there is a reported lower incidence of contrast media rxn using non-ionic 
contrast compared to ionic contrast media but no good study done. 
non-ionic contrast used almost exclusively in mylography, but it costs 
about a buck a cc compared to about 3 cents/cc for the ionic stuff.

impt to prepare patient well, always let patient drink H2O so well 
hydrated, give IV fluids, dose/rate of contrast important. know about 
underlying conditions eg liver/renal probls.

we've talked about "how to make radiograph"
photons generated in xrtube, what controls quantity and quality of them. 
various devices, collimators, etc. this is routine small an radiography. 
but we do many other studies, esp in lg animals. horizontal beam 
radiography: pointing xr tube horizontally compared to body part: right 
to left horizontal beam rad of chest - tube on cow right side, film on 
cow left side. also use this technique for lg animal extremities. 
nomenclature: direction of xr beam. how do you name a view? direction of 
beam through body part. 

horizontal beam rads in small animal medicine: hang cassette on wall or 
whatever...can use automatic film changer...tilt tube to be horizontal. 
many small an vet xr machines can't do this, but some can. can be 
important.

R->L lat chest - heart not touching sternebrae. why? pneumothorax causing 
free air in chest and collapsed lung? could be. L lat more likely than R 
lat to see some degree of heart falling away from sternebrae just 
normally. if you see this, could do horizontal beam rad. then, air will 
move to upper thorax. then, you will see that heart sits on sternebrae, 
and there is huge amt of free air in dorsal chest, and can see the aorta 
sitting in the free air, dorsal to the dorsal border of the lung lobe! 
will see smaller amts of gas/air in chest using this technique.

R->L lat chest - see haziness in lung fields, increased opacity at heart 
apex - fluid? pleural thickening? eh, maybe minimal. using horizontal 
beam technique: 
heart totally obscured by something...so much fluid, about 1/2 of chest 
is full of fluid. why is there no flat fluid line? well, there's a 
meniscus, so fluid goes up around the lobes. if you see flat air/fluid 
line, you have a pneumothorax, too!

[more greys you see, less contrast in film. fewer densities seen, more 
contrast film has. that was the answer to my question]

horizontal beam study of bladder - contrast put into bladder, just a 
little. can see air/fluid line, and subtle problem - defect in 
ventral/cranial border of bladder wall.

TOMOGRAPHY: this is in the lecture 7 notes, p 13 and 14.
this is XR tomography, not computerized eg CT. we do XRT here and at NBC.

this works by your fastening XR tube to grid/bucky tray under table by a 
rod. the tube is on a device so it can swing to L and R, so when it moves 
to L, bucky tray goes to R (eg, it pivots). during the exposure, you move 
the tube from one side to another. this way you look at a part of the 
body w/o having other things summated on it. so. there is a FULCRUM 
involved. this is the focal point. everything above and below that point 
is blurred from movement. you start exposure with tube on L. during 
exposure, tube moves L-->R and film moves the other way (rod is vertical, 
see). can move the fulcrum from tabletop to 20cm above. so, you have 
chest rad that is abnormal, can't see R side of heart. there is soft 
tissue density there. also radiolucent areas in caudal lung lobes 
surrounded by opaque area. hmmm. what is this? do XRT of chest. at level 
close to midline- can't see ribs, they're blurred out. in cranial chest 
is discrete soft tissue mass containing air. it is cavitated. it's a 
malignancy with necrotic center. caudally we see that the radiolucent 
spots are also within masses. multiple adenocarcinoma nodules, turns out.


looking at spine...dog w/acute rear leg lameness neurologically 
compatible with spinal problem. XRTshows that there is a radiolucent 
defect in one of the vertebrae...a malignancy of thoracic vertebra. not 
seen on survey rads.

this technique is used alot in humans. use elliptical movements - not 
just linear. can get a lot of good detail.used less commonly in 
veterinary medicine.
this technique does have some advantages over CT in some situations.
exposure is longer using this. use lower mA, but longer s,  - same mAs 
total.
this is a different principle from radiotherapy. not the same. we won't 
discuss therapeutic radiation.

longer the travel, the thinner the slice. we control how big the arc is. 
the bigger the thinner. a narrow arc gives a big thick slice.

MAGNIFICATION RADIOGRAPHY: this is a very specific, purposeful exam to 
look at a part. increased object-->film distance. edge is less sharp, 
less detail -in routine rads. but you can in fact have an XR tube 
designed for this!
if you increase object-->film distance in normal machine, you get 
magnification and blurring - due to size of focal spot. but if you have a 
much smaller focal spot, you can increase the object-->film distance, and 
retain your detail. veterinary units do not have focal spots this 
small.you need 0.3mm or smaller focal spot to avoid getting loss of 
detail with magnification. but in human hospitals, they have 
these...0.1mm and smaller spots. and people use these techniques.

slide of PA in dog. without magnification, you couldn't see the 
seconary/tertiary branches of L caudal lung lobe artery, and would not 
see the HW in the vessel on a nonmagnified angiogram either.

XERORADIOGRAPHY: the third modality in our notes. uses an xray tube, 
also, like the other two. the other two use standard systems, this one 
uses a different system. it uses a tube that looks like a regular 
one...same xr tube. and you use cassettes, but the thing is the cassettes 
have no FILM in them. the cassette is made of selenium crystals. the 
crystals  - you put the cassette in the machine to get charged. when xr 
interact w/charged crystals, the crystals are converted, and you take the 
cassette, run it through processor, which is just like a copy machine by 
xerox. it's the same. it takes the charge and prints it out on paper as 
an image. there's a dielectric capacitor plate, and aluminum substrate, 
yada yada. so it prints out blue on white or white on blue. the 
definition and basic steps are in handout. charge plate, expose, use 
technique chart, etc. then put plate in processor. latent image converted 
to paper image. disadvantages: 10x the radiographic exposure. no longer 
used in human medicine. NBC may have the only currently operating 
xeroradiographic machine in the US. hopefully it will last for a whiile, 
they're off the market. it's outdated technology. sometimes is used at 
NBC though. now, better film/screen systems are as useful as this in 
human medicine. but in horses, there is use for it. this technique has 
"edge enhancement" so some fx are easier to see on these prints. but with 
experienced radiologists reading them, there are very few things you'd 
see on this that you wouldn't see on the plain rads. remember, we're not 
worried about a horse getting a tumor 40 years down the line like we are 
in people.

STRESS RADIOGRAPHY: the application of a controlled force upon a body 
part to determine abnormal relationships among the various structures of 
that part. not in the notes! is done commonly to show problems you can't 
see using routine positioning techniques. eg, in joints to show ligament 
injuries, small fx, instability, and also - abdominal compression is this 
technique - eg a band around the belly used for urogenital studies. 
amenable joints: TMJ, elbow, etc etc etc . flexed lateral carpus of horse 
= stress radiograph. if you stress a joint by flexing it it is a stress 
radiograph. routinely done in the horse. can highlight chip fx etc. also 
lateral neck rad of potential wobbler horse shows no problem, myelogram 
normal, but stress rad with flexed neck shows that between C2 and C3 the 
ventral column of contrast in subarachnoid space is interrupted 
indicating compression of the cord at this point. you should always take 
stress views - extended and flexed.
boxer puppy with sudden onset swelling of tarsal region, pain on 
palpation, dead lame on that leg. radiograph shows nothing. (routine 
lateral view). so, stress rad= flexed or extended joint. the puppy was 
more painful on flexion. so we flex the joint and radiograph it: now we 
see a fracture of the distal tibia. it's there, plain to see. but you can 
NOT see it on the standard view!
cat that bites people if you try to touch its tail. tail was caught in 
door this morning. sl swollen a bit distal to tail base. no fx or 
subluxation seen on lat or vd tail rads. so they bent the tail and took 
another view and saw a luxation.

----break----

another imaging thing - digital radiography. this is having a cassette 
that goes on the table or in cassette holder per normal SOP, but has no 
film in it and instead has  a patented almost 0radiograph like thing with 
photoreceptors. as you expose, diff charges occur related to # of XR 
getting through. this then goes down a wire into your PC. in fact, it is 
used over in the medical school. it's filmless and captures digital 
images, which can then be emailed or whatever. then you can send the 
image to specialists really easily. now, some people are digitizing 
films, eg scanning them in, and sending those around, but this is a 
filmless system altogether. 3 vet schools have these, two in the US. the 
cool thing is you have the image in five seconds! then you can say "ok, 
you can go home" or you can say "hmm. do it again." or "take a different 
view" or whatever. and you're not using film, chemicals, etc. and can 
manipulate contrast/density/etc on the computer. can enhance edges, 
magnify, change density, etc. then you CAN print it out if you want. this 
is very expensive, but will surely come into use during our practicing 
lifetime.

the places that bought this system talk about how they save money on film 
and stuff. but now, they wanna print out the image with both bone and 
soft tissue contrast, etc...and they use more film this way :) but the 
novelty will wear off of that, soon. can print on paper or xray film. 

we're pricing out one of those for VHUP.

ok. directional terms.

on the head: rostral = toward lips, caudal = toward back of head. dorsal 
= face and back of neck, ventral = under chin, under neck. craniocaudal 
describes above carpus or tarsus. distal to those joints, dorsopalmar or 
dorsoplantar.

eg: left to right dorsomedial-palmarolateral oblique.
if you do this, the film is on the right palmarolateral surface of the 
right arm.  at NBC, they'll call this a lateral oblique. but, at other 
places, they call it a medial oblique (eg, Davis) because they label the 
part closest to the tube.

note that with more experience, you will not need labels on your films, 
b/c you can tell from looking at the picture what you are looking at, and 
it doesn't matter what is marked on the film.

[blah blah more about different views of legs]

MAN it is cold in here today.

note: you do need a marker to tell medial from lateral...
at NBC we put marker on lateral side of part. some places put marker on 
medial side of part. why can't these people get together and make a 
standard on this??

anyway.
positioning is IMPORTANT. you want the best radiograph based on knowledge 
of various factors. again, expiratory vs inspiratory chest rads - better 
detail at height of inspiration - more air is in chest, better contrast. 
normal dog looks sick on expiratory view. lungs are smudged and hazy on 
expiration. note diaphragm abuts heart on expiratory view. 

fluid - positioning makes great difference. fluid moves down with 
gravity. in lateral position, fluid will be on down side of thorax, will 
obscure heart. in VD, fluid will be along dorsum, lung will surround 
heart, can see heart. in a DV, fluid along sternum, will obscure part of 
heart. DV looked totally white and cloudy in lung fields, VD looked  more 
normal, on rads of cat w/pleural effusion. we see in cat scan...VD can 
see heart surrounded by black lung w/fluid dorsally. DV see fluid next to 
heart. hard to see.

RLR- right lateral recumbency. also marked just R. chest looks totally 
normal. 
in LLR, we see a lobulated soft tissue opacity over the middle of heart.

VD- there's a lung tumor in the right lung. we saw it w/left side down, 
not w/right side down. that's 'cause w/right side down, right lung is 
compressed. heart falls onto it. the lung loses volume. there's more soft 
tissue density there, obscuring any lesions. there's less contrast in 
that lung.

with horizontal beam radiography, it wouldn't matter if you took L-->R or 
R-->L
so in people, they do it this way and only take one lateral. standing 
lateral radiographs - only need one, not both left and right.

principles of interpretation:

determine if abnormality exists
define anatomic location
classify lesion according to roentgen signs
develop clinical differential diagnosis.

we've discussed many ways of obtaining images, using XR tubes and other 
ways like magnets, etc. hopefully we're getting a feel for positioning, 
what some things look like on radiographs, radiolucency of trachea 
compared to mediastinum and heart. etc. we're not talking about how to 
characterize abnormality at this point.

need to be familiar with radiographic anatomy
need systematic method of examination
have to know disease and their radiographic patters
know disease incidence relative to signalment, genetic predispositions.

interpretation of survey rads:
look for: number, size, shape, position, radiographic density.
are there two kidneys? are they normal size and shape? in right place? 
normal density?

right kidney - usually more cranial. left usually more caudal. may be 
superimposed or partially superimposed. may not see at all, depending on 
amt of fat. want EXPIRATORY phase rad for abdomen, so diaphragm is moved 
cranially, and organs can spread out.

renal size rule of thumb: do not need to know ;)
will learn next year.

positional artifacts - rotated, exp phase rad may look really bad :)
have to be perpendicular to lesion to see it. may not see fracture on 
lateral view, but see it perfectly well on dorsopalmar view, for example. 
rib fx - need 6 rads made at different angles since ribs are round. start 
near area of pain and swelling :)

sample question:
diagnose this problem - you have 15 seconds. ready? stupid stupid stupid 
slide.


----end----