Physics: X-Ray Production 2 (Huda)

Front 1

What happens when electrons strike the anode

Back 1

Electrons striking the target, located in the anode, produce heat and x-rays

Front 2

Why is tungsten the most common anode

Back 2

Tungsten is the most common target material because of its high atomic number (Z
= 74) and melting point.

Front 3

What is often added to a tungsten anode

Back 3

Rhenium is often added to reduce the pitting and cracking caused by overheating.

Front 4

What is the make up of the anode used for mamography

Back 4

Molybdenum (Z = 42) and rhodium (Z = 45) are used for targets in mammography.

Front 5

When are stationary anodes commonly used

Back 5

Stationary anodes are used in some C-arm x-ray units

Front 6

What makes up the anode of a stationary anode

Back 6

A stationary anode usually consists of a tungsten target embedded in a copper
block.

Front 7

Why do most anodes rotate

Back 7

A rotating anode greatly increases the effective target area used during an expo-sure and therefore raises the heat capacity.

Front 8

What is the focal spot

Back 8

Th e focal spot is the apparent source of x-rays in the tube.

Front 9

What determine the focal spot size

Back 9

Focal spot size is a result of the filament shape, focusing cup, and electric field cre-ated between the cathode and anode.

Front 10

What does a focal spot tract look like

Back 10

Front 11

Why do you want a small focal spot

Back 11

small focal spots make sharper images

Front 12

Why do you want a large focal spot

Back 12

larger focal spots can tolerate larger amounts of heat without melting

Front 13

What are 2 considerations when determing the size of a focal spot

Back 13

Focal spots must be small to produce sharp images, but large enough to tolerate a
high heat loading without melting the target.

Front 14

What happens to the size of a focal spot as the current increases

Back 14

Th e focal spot size enlarges as milliamperes increase owing to the repulsion of ad-jacent electrons. This effect is called blooming.

Front 15

What are the sizes of focal spots used in radiology

Back 15

Front 16

What is the difference between the focal spot and focal tract (last image misleading...correct)

Back 16

Front 17

What is the line focus principle

Back 17

The line focus principle is used to permit larger heat loading while minimizing
the size of the focal spot by orienting the anode at a small angle to the direction of the x-ray beam irradiating the patient

Front 18

What is the typical anode angle

Back 18

7-20 degree

Front 19

What happens to the radiations field coverage as the anode angle increases

Back 19

Radiation field coverage increases with increased target angle.

Front 20

What are typical focal spot sizes

Back 20

Focal spot sizes, as quoted by manufacturers of x-ray tubes, range from about 0.1
to 1.2 mm.

Front 21

How are focal spot sizes measured

Back 21

Focal spot sizes can be measured using pinhole cameras, star or bar test patterns, or
slit cameras.

Front 22

When are large and small focal spot sizes necessary

Back 22

-A large focal spot is favored when a short exposure time is the priority.
-A small focal spot is preferred when spatial resolution is a priority.

Front 23

What is the technique to measure the focal spot size with a pin hole

Back 23

Front 24

How does an anode angle change the focal spot size

Back 24

Front 25

What happens to the focal spot size if the electron beam size is increased

Back 25

Front 26

Heel effect

Back 26

Front 27

How does a single anode have different anode angles

Back 27

like this anode

Front 28

What 3 controls are determined by the operator

Back 28

I n manual mode, the operator selects the x-ray tube voltage, x-ray tube current, and
exposure time on the generator control panel.

Front 29

What controls are set by the operator when using the automatic exposure control

Back 29

I n automatic exposure control (AEC) mode, the operator selects the x-ray voltage
and the desired film density, and the generator circuits control the exposure time
and current (mAs).

Front 30

What to settings are controlled automaticaly with AEC

Back 30

millamps
time of exposure

Front 31

What to settings are controlled by the operator with AEC

Back 31

voltage
density

Front 32

What is the X-ray tube output directly proportional to

Back 32

Th e x-ray tube output is directly proportional to the x-ray tube current.

Front 33

What is a typical X-ray tube current

Back 33

A typical current for radiography is 100 to 1,000 mA.

Front 34

How long is a typical x-ray tube exposure time

Back 34

Typical radiographic exposure times are between tens and hundreds of millisecond.

Front 35

How many mAs is there in a given exposure time

Back 35

Typical tube current exposure times in radiography are tens of mAs.

Front 36

What is the current in typical flouroscopy

Back 36

In fluoroscopy, tube currents are typically between 1 and 5 mA.

Front 37

What is the kVp typically for smaller body parts

Back 37

Fo r small body parts, such as the extremities, x-ray tube voltages are generally 55
to 65 kVp.

Front 38

What is the kVp for the majority of plain film and flouro

Back 38

Most radiographic and fluoroscopy imaging is performed at x-ray tube voltages be-tween 70 and 90 kVp.

Front 39

Is there usually higher voltages for larger patients

Back 39

Higher voltages may be used for larger patients.

Front 40

What is the typical kVp for chest X-rays

Back 40

Chest radiography is often performed at higher x-ray tube voltages of about 120
kVp.

Front 41

When is higher kVp used for flouroscopic imaging

Back 41

High voltages (>10 0 kVp) are also used in some fluoroscopy performed with bar-ium contrast agents to provide sufficient penetration.

Front 42

What percent of energy is converted to X-rays

Back 42

Onl y about 1 % of the electric energy supplied to the x-ray tube is converted to x-rays. The rest is converted to heat

Front 43

What is tube loading

Back 43

Th e amount of heat energy deposited during an x-ray exposure is known as the tube
loading