green app wrong

Question 1

TR: 500 TE: 10

Answer 1

T1 sequence. short short. (short TR <500 ms and short TE < 20 ms)

Question 2

TR = 2000 TE = 70

Answer 2

T2 sequence. long long. TR > 2000, TE > 70

Question 3

TR long, TE short

Answer 3

PD sequence

Question 4

to correct for aliasing in Doppler what can you adjust

Answer 4

increase PRF, increase the scale, lower frequency transducer, gate closer to the transducer, doppler angle CLOSER to 90

Question 5

what is the effect on chemical shift artifact if the receiver bandwidth is increased in MRI

Answer 5

DECREASE. TE, SNR, and mismapping artifacts all Decrease.

Question 6

decreasing the doppler angle has what affect on aliasing?

Answer 6

it improves aliasing

Question 7

how does using a lower frequency probe affect aliasing?

Answer 7

improves aliasing. size of the doppler shift is proportional to the fundamental imaging frequency. Using a lower f probe will result in a relatively smaller doppler shift –> decreased aliasing

Question 8

common artifact encountered with a fluoroscopy system using flat panel detectors

Answer 8

persistence (ghosting) artifact.

Question 9

reduction of image artifacts caused by eddy currents is achieved by using

Answer 9

actively shielded magnetic field gradient coils

Question 10

which subatomic particle determines an atom’s chemical properties?

Answer 10

electron

Question 11

what happens to contrast as latitude is increased

Answer 11

decrease

Question 12

conventional radiographic film is exposed by what?

Answer 12

visible light

Question 13

In CT, decreasing the FOV while keeping the matrix size constant will result in what?

Answer 13

decreased contrast resolution. Pixel size = FOV/matrix. Decreasing FOV –> decreased pixel size –> fewer photons per pixel –> increased noise –> decreased contrast resolution

Question 14

what happens to beam intensity when mA is doubled?

Answer 14

beam intensity will double

Question 15

decreasing the anode angle has what affect on focal spots?

Answer 15

actual focal spot size of the target NEVER changes. The EFFECTIVE focal spot size decreases –> decreased geometric blur.

Question 16

Inherent filtration refers to attenuation of the xray beam by:

Answer 16

target material and xray tube window

Question 17

when does max mA increase?

Answer 17

when the anode target rotational speed is increased. more heat is able to dissipate and the xray tube rating is increased.

Question 18

how is the E of characteristic xrays produced by an xray tube compared to the k-shell binding E of the tungesten target?

Answer 18

characteristic xray E < k-shell binding E

Question 19

if the wavelength of a photon is doubled, the E of the photon will…

Answer 19

decrease by a factor of 2. the E of a photon is directly proportion to its frequency and INDIRECTLY proportional to its wavelength.

Question 20

applying Al filtration to the xray beam will do what to the image contrast

Answer 20

reduce. lower E photons filtered out –> increased average E (keV) –> decreased contrast.

Question 21

100 samples per horizontal row that is 100 mm long. What is the limiting spatial resolution?

Answer 21

0.5 lp/mm. samples/row length (100/100 mm = 1 sample/mm). The limiting spatial resolution is 1/2 of the sampling frequency, or 0.5 lp/mm