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Stuff and Thangs > Mahoney Radio > Flashcards

Mahoney Radio Flashcards

1
Q

These measurements measure the quantity of radiation exposure.

A

Roentgen or Air Kermas

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2
Q

Theasy measurements measure the quantity of absorbed dose.

A

Rads or Grays

10-20 grays are lethal to humans.

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3
Q

What is X-ray attenuation?

A

The absorbance of X-rays by matter.

Matter that absorbs x-rays appears white and are radiopaque.

Matter that allows total penetration appear black and are radiolucent.

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4
Q

Basic difference between kVp and mA’s?

A

kVP deals with the quality of the image and manipulates the energy.

mA’s effect the quantity of X-rays.

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5
Q

What is the Cathode?

A

the negative electrode of the x-ray tube.

Contains filament made of tungston that makes electrons when heated!

The focusing cup then directs the filament electrons to the anode.

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6
Q

What is the Anode?

A

The positive electrode of the X-ray tube.

Contains the target (area to which electrons from the cathode are directed)

Focal spot (Area on target from which x-rays are emitted).

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7
Q

What is colimation?

A

Shaping of the dimensions of the useful x-ray beam so that only the area of interest is x-rayed.

“Focuses the useful beam”

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8
Q

What is characteristic radiation?

A

Electron interacts with the atoms inner shel electrom removing the electron causing ionization.

X-ray photons produced as outer-shell electrons then fill the inner shell.

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9
Q

What is bremsstahlung radiation?

A

Electron slows down or brakes as it passes by the charged nucleus.

Changes course of electron causing it to lose energy in the form of x-ray photons.

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10
Q

What effect does increasing the mA’s have on quantity and quality?

A

It increases the quantity of x-rays but not the quality.

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11
Q

What effect does increasing the kVp have on x-rays quality vs quantity

A

Increases both the quality AND the quantity.

increases the penetration

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12
Q

What effect does X-ray filtration have on quality and quantity of x-rays?

A

Decreases the x-ray quantity and increases the quality.

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13
Q

what is the X-ray Heel Effect?

A

Useful x-ray beam has greater intensity on the cathode side than the anode side.

Results in line-focus principle occuring.

Thus position the thicker portion of the part to be examined closer to the cathode

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14
Q

What is X-ray coherent scattering?

A

As x-ray photons excite the target atom, a secondary photon of equal energy is released in a different direction which is absorbed by the patient but does not contribute to the image!!

This is useless and dangerous radiation!

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15
Q

What is X-ray Compton scattering?

A

Occurs when the x-ray photon interacting with matter ejects and outer shell electron causing ionization!

The original x-ray continues in a different direction with decreased energy.

This creates a “Fog” that impairs the image quality by reducing its contrast.

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16
Q

What is the X-ray photoelectric effect?

A

This is an effect where the X-ray photon is totally absorbed and an inner-shell electron is ejected during ionization.

This process causes beam attentuation and image formation.

Also contributes to patient absorbed dose.

This is good we want this!!

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17
Q

Which type of radiation forms the diagnostic image?

A

It is formed by the photoelectric effect and remnant radiation.

Most X-rays interact with matter by compton scatering causing image fog.

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18
Q

Does Low kVP favor compton scattering or the photoelectric effect?

A

Low kVp favors the photoelectric effect but increases the dose of radiation to the body!!

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19
Q

Does high kVP favor the compton scattering effect or the photoelectric effect?

A

High kVp favors compton scattering (more radiation makes its way to the x-ray film because less is absorbed by the body)

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20
Q

What is the definition of X-ray resolution?

A

The ability to distinguish between two objects which are side by side with different contrasts (bone vs soft tissue)

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21
Q

What is the spatial resolution of an x-ray?

A

The image sharpness!

Ability to differentiate between two objects.

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22
Q

What is the contrast resolution of an X-ray?

A

The ability to distinguish between differences in density or intensity or shades of gray.

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23
Q

What is radioraphic density and what factor controls it most? (kvp or ma?)

A

Amount of darkening in a radiograph.

MA’s and exposure time control this most.

As mA’s increase the image becomes darker.

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24
Q

Describe how mA is related to the law of reciprocity

A

As mA’s are increased, the image becomes darker.

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25
Q

How are kVp’s related to image contrast?

A

Low kvp creates high contrast (images appear black or white without much gray)

High kvp creates low contrast (more grays)

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26
Q

What do compensation filters do?

A

Allow for the unequal radiographic density between the forefoot and the rearfoot.

Because the forefoot is thinner, it would otherwise be unbalanced in radiographic exposure.

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27
Q

What is the difference between radiographic contrast and subject contrast?

A

Radiographic contrast is the result of a difference in densities that allow the viewer to discern between two adjacent densities within the same image.

Subject contrast is a result of attenuation differences as x-rays pass through the body. Affected by tissue thickness, type, anatomic number etc.

28
Q

What is the primary factor in controlling constrast?

A

kVp!!

29
Q

What is spatial resolution?

A

Refers to the image detail, sharpness, definition and is the recorded accuracy of the structures imaged.

Affected by the focal spot size, the object to image distance, and the source to image distance (distance from the tubehead to the film)

30
Q

What can you do with kvp and MA’s to minimize motion or blurring with children?

A

Decrease the exposure time by 1/2 and increase the kVp by 15%

31
Q

What is the normal kVp and mA when fixed?

A

Fixed kVp is 60 for podiatry and mA will vary depending on thickness.

Fixed mAs typically use kVp’s lower than 60.

32
Q

What material is present within the film vs the intensifying screens?

A

film uses silver bromide

Intensifying screen uses calcium tungstate.

33
Q

What chemical determines the speed of a film?

A

The silver halide crystal size, structure, and sensitivity.

34
Q

How are pixel size related to the spatial resolution (sharpness)

A

The smaller the pixel the higher the spatial resolution.

35
Q

How does PET scanning work?

A

Radioisotope 18-FDG (fluorodeoxyglucose) is injected to determine abnormal glucose metabolism.

Inflammatory cells increase FDG uptake.

Results appear within 2 hours of injection patient must remain completely still and is usually combined with a CT.

36
Q

What is a SPECT scan?

A

Single photon emission computed tomography

IV injected gamma-emitting radionuclide Tech-99, In-111, Tch-99.

Gamma camera rotates 360

37
Q

What chemical is used on the fluoroscopic cathode?

A

Cesium iodide phosphor.

38
Q

What is the size for barriers?

A

0.25 mm aprons, gloves, goggles.

gonad shields need to be 0.5 mm.

39
Q

Describe the density order of anatomic structures to radiographs.

A

Cortex, cancellous, muscles, nerve, tendon, ligaments, sub q, fat, air.
(From high to low density)

40
Q

Describe the positioning for an AP radiograph

A

15 degrees from vertical.

41
Q

What do you aim at for a lateral image?

A

Aimed at the cuboid angled 90 degrees from vertical.

42
Q

What do you aim at for a medial oblique view?

A

Aim for that third TMTJ babe

45 degrees from vertical with the medial side of the foot to the image receptor.

43
Q

Where are you aiming for the lateral obliqu image?

A

Hit that first tmtj bruh.

44
Q

Describe the harris beath view and its positioning

A

Check the middle and posterior calcaneal facets for coalition.

Tube is posterior to the foot in the charger position 45 degrees from vertical.

45
Q

What is seen in a positive talar tilt radiograph?

A

> 10 degrees of inversion

or 5 degrees more than the contralateral side.

46
Q

What is seen in a postive anterior drawer/push-pull radiograph?

A

A positive test is a 6mm or greater gap between the posterior lip of the tibia and the nearest part of the talar dome.

47
Q

How is the foot positioned for an ankle mortise view?

A

15 degrees of internal rtation from the central beam aimed at the lateral malleolus.

Allows viaualization of the middle and posterior STJ facets.

48
Q

Ossification date of the lesser metatarsals?

A

3-5 years for the met heads

9 weeks IU for the met shafts.

49
Q

Ossification date for the first met base?

A

2 years

50
Q

Ossification for the fifth met base?

A

6-8 years.

51
Q

Which structures are always dark on MRI?

A

Ligaments and bone should always be dark unless otherwise. (T1 fat will show in bone)

52
Q

What exactly is a STIR image?

A

A fat supression image.

Used to nullify the signal from fat to allow greater visualization of other structures.

53
Q

What are the contraindications for MRI?

A 
Stents
Metal shards in the eye
Pacemakers 
Cochlear implants
Metal clips
Metal valves
Internal fixation should be in at least 6 weeks*
54
Q

Three main podiatric indications for CT?

A

Coalitions
Complex Fractures
Charcot arthropathy

55
Q

What does Tch 99 bind?

A

Hydroxy apatite

Finds areas of bone turnover and inflammation

56
Q

What are the times for bone scans?

A

Flow phase 1-3 seconds
Blood pooling phase: 5-10 minutes
Delayed phase: 3-4 hours for bone (cellulitis vs osteomyelitis)

4th phase >24 hours for diagnosis of osteomyelitis.

57
Q

What does gallium 67-citrate bind?

A 
Binds to WBC
Sideropores
Transferrin
Ferritin
Lactoferrin

Identifies neoplasms and inflammatory disorders.
*Excreted by the kidneys with high radiation dose (half life 78 hours)

58
Q

What does indium-111 bind?

A

Binds to cytoplasmic components of the WBC membrane.

Spleen and liver will light up (WBC turnover)

Used for leukocyte mediated/inflammatory disorders.

Best for acute infections (gallium best for chronic)

59
Q

What is the use of Thallium-201 in bone scans?

A

Evaluates the foot profusion.

60
Q

What can TC be combined with to determine osteo vs cellulitis?

A

TC + gallium

Give Tch first because its shorter halflife.

61
Q

How many Hz is the podiatry ultrasound probe?

A

7.5 hz hockey stick
Can penetrate 7 cm deep.

Great for when there are pacemakers or metallic implants!

62
Q

What is the normal thickness of the plantar fascai on ultrasound?
What is considered pathologic?

A

Normally 4 mm thick

Pathologic PF would be >4 mm?

63
Q

Roentgen

A

The amount of radiation in general

64
Q

Rad

A

The amount of radiation absorbed to the body

100 rads can kill someone

65
Q

REM

A

The actual biological damage secondary to rads

66
Q

What exactly is MA?

A

Milliamperes
The quatity of actual electrons produced
Measure of the current

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