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Princ. of Imaging I

Jack -Technique year 1

QuestionAnswer
density -amount of blackness on a radiograph -Degree of blackening or opacity on a radiograph (not AART definition)
contrast (pertaining to density) -the difference between adjacent structures (on radiograph) -variation in density present on a radiograph (not AART definition)
absorption process where X-rays deposit their energy in the matter through which they pass.
Radiopaque -structures that absorb x-rays -prevents x-rays from passing through -opaque area on the image is white
Radiolucent -Structures that allow x-rays to pass through -Lucent area on image is "black or dark"
Density of anatomical parts in order 1. Air (produces most density/blackness) 2. Fat 3. Water 4. Muscle 5. Bone(produces least density/white)
mA controls # of electrons
Time (s) amount of time the electrons are permitted to strike the anode to produce x-rays.
mA X time (s) = mAs!
mAs total intensity or quantity of x-rays
Primary controller of density mAs
mAs is directly perportional to_________ Density. Double the mAs= double the density
Law of Reciprocity equal denstiy for same mAs regardless of mA and time selected 100mA X .025s= 2.5mAs 50mA X .05s= 2.5mAs
Densitometer Measures the density on the radiograph
Measuring density vs % of light transmitted (value chart for optical density) Density %light trans. 0 clear 100 1 light gray 10 2 medium gray 1 3 dk, gray/blk 0.1 4 black 0.01
Useful density range Range of density on a radiograph that will provide diagnostic information of anatomical part of intrest 0.25-2.5
What % change in density must take place for human eye to notice? 30%
Minimum increase in mAs: 100%. Min is double, but may have to double, triple or quadruple the mAs
Minimum decrease in mAs: 50%. Decrease by half.
kVp -kVp is penetration, no amount of mAs can compensate for lack of kVp! -kVp appropriate to penetrate the part, mAs to adjust for density. -kVp is penetration, added densitiy due to a greater number of x-rays penetrating the part and reaching the film.
15% rule for kVp -An increase of 15% will double the density. -A decrease of 15% will half the density. (find 15%- 10% of 50 is 5. half of 5 is 2.5 so 15% of 50 is 7.5/8) this rule is NOT perfect.
Adjusting kVp in the 60-80kVp range: +/- 10kVp will be about 15%!
kVp and the chest -Need more kVp to penetrate heart shadow -More mAs will NOT make the spine visible. -should see vertebrae through heart shadow.
select kVp to ______ the part and mAs to adjust for ____ penetrate, density
kVp is the gas in the tank to.... get the x-rays where they need to go!
Inverse square law (formula) I1 d2² ___ = ___ I2 d1² I1= original intensity I2= new intensity d1= original distance d2= new distance
Inverse square law -remember: I1 and d1 are... Inversely proportional, so I1 will be on top and d1 on bottom
Density Maintenance Formula mAs1 d1² ____ = _____ mAs2 d2² mAs1= original mAs mAs2= new mAs d1 = original distance d2 = new distance
Density Maintenance Formula- remember mAs1 and d1 are... Directly proportional, so mAs1 and d1 will be numerators.
Anode Heel Effect (AHE) -Intensity of the radiation is greater on the CATHODE end of the tube -Anode will stop some x-rays
Anode Heel Effect is less noticeable when? When greater SID is used.
Will larger or smaller film demonstrate AHE? Larger. Especially at a short distance.
With consideration to AHE, where do you place the thicker part of the anatomy? Cathode side for more uniform density. i.e. AP supine thoracic spine, AP foot.
Name the 4 body habitus. Asthenic, Hyposthenic, Sthenic, Hypersthenic. (written smallest to largest)
Atomic number: -The number of protons in the nucleus of an atom. -# of protons equals the # of electrons. -HIGHER THE ATOMIC #, THE GREATER THE ABSORPTION OF X-RAYS.
Why does Barium show up on an x-ray? -It alters the subjects density -Barium has a higher atomic number(56) than bone (13.8)
Photoelectric effect (absorption) when an x-ray photon bumps out an electron of an orbital shell and the x-ray is totally absorbed.
Tube angulation and density Compensate for body thickness when angeling the tube more than 15 degrees by placing the thicker part on the cathode side of the tube.
Pathology -Medical science that is concerned with all aspects of disease -Disease changes body tissues, these changes can be demonstrated on a radiograph.
Two types of Pathologies Additive and Destructive
Additive Pathology -Alters tissue which makes it harder to penetrate (radiopaque) -Additional technique may be required
Destructive Pathology -Alters normal tissue which makes it easier to penetrate (radiolucent) -A deduction in technique may be required
Consolidation of lung any additive in the lung field. ie- cancer, pneumonia, pleural effusion...
Ascites -fluid build up in tissue -has a "ground glass appearance" -makes tissue more dense
Paget's Disease Begins with over active osteoclasts=destructive. Ends with overactive osteoblasts=additive. Considered ADDITIVE PATHOLOGY
COPD DESTRUCTIVE PATHOLOGY Chronic Obstructive Pulmonary Disease -Asthma -Bronchitis -Pulmonary emphysema -Barrel chest Reduce mAs/technique
Bowel Obstrustion DESTRUCTIVE PATHOLOGY -air in bowel=radiolucent
Additive pathological conditions -Callus -Osteopetrosis (opp of osteoporosis) -osteochondroma -Acromegaly -Pneumonia -Pleural effusion -Hemothorax (blood in lung) -Lung abcess (puss in lung)
Destructive pathological conditions -Necrosis -Osteolytic bone cancer -Osteoporosis -Osteopenia -Pneumothorax (PA chest on expiration) -Emaciation (ashtenic body)
Fiberglass casts No change in technique (5kvp if very thick)
Plaster casts Increase exposure factors -wet 3x mAs, or increase kVp by 15* -dry 2x mAs, or increase kVp by 10* *Not sure if these are % or whole numbers. He was using both.Im going to email him and figure it out.
Can you remove and appliance applied by a Dr.?? NOOOOOOOO! Unless you or the patient is authorized by the Dr.
And now its time for... Tequila! bwaahhahahah! Good luck!
Created by: aquaviva77