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Princ. of Imaging I
Jack -Technique year 1
| Question | Answer |
|---|---|
| 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:
kristinaborstnik
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