mammo

Question 1

mammo beam quality

Answer 1

HVL is ~0.3 mm Al

Question 2

mammo matrix size

Answer 2

4096x6144
2 bytes/pixel
50 MB

Question 3

mammo resolution

Answer 3

7 lp/mm

Question 4

SID

Answer 4

65 cm

Question 5

what does increasing breast thickness by 10 cm do to average glandular dose?

Answer 5

doubles it

Question 6

cancer detection in mammo

Answer 6

4/1000

Question 7

ACR phantom pass

Answer 7

4 fibers
3 specks
3 masses

Question 8

mA for mammo

Answer 8

100 mA contact mammo
25 mA magnification

Question 9

what interaction dominates in mammo?

Answer 9

PE
Compton dominates in other radiography

Question 10

breast bipsy angles

Answer 10

+/- 15 degrees

Question 11

mammo HVL

Answer 11

0.5 mm Al

Question 12

grid factor factor in mammo

Answer 12

5:1 vs 10:1 for most other radiography
could also use air gao

Question 13

focal spot in mammo

Answer 13

0.1 mm magnification mammo
0.3 mm contact mammo

Question 14

pixel sizes mammo

Answer 14

50-100 um

Question 15

tomosynthesis arc

Answer 15

arc is 15 degrees with image at each degree
shows lesions in given plane

Question 16

power loading in mammo

Answer 16

3 kW contact mammo
1 kW magnification mammo
100 kW CT

Question 17

mammo digital vs screen film resolution

Answer 17

7 lp/mm vs 12 lp/mm
-but digital mammo has better contrast resolution
-clinically they were found to be equal in efficacy

Question 18

SID effect on focal spot blur

Answer 18

reducing SID increases focal spot blur

Question 19

requirement for average glandular dose for 4.2 cm thick breast

Answer 19

<3 mGy/image with grid, <1 mGy/image without grid
-for breast with 50% glandularity
left and right breast DONT get added together into total dose
-if each breast gets 3 mGy, patient dose is 3 mGy

Question 20

size of average compressed breast

Answer 20

60 mm thick, 15% granularity

Question 21

semi-annual mammo QA items

Answer 21

dark room fog
screen-film contact
compression

Question 22

QA tests in safety code 35

Answer 22

-reproducibility
-AEC
-linearity |x1-x2|</=0.1(x1+x2)
-HVL
-max exposure rate for fluoro

Question 23

limiting factor for detecting microcalcifications

Answer 23

signal difference to noise ratio

Question 24

focal spot size deviation

Answer 24

focal spot size gets smaller away from chest wall

Question 25

why is cathode in mammo at chest wall?

Answer 25

to account for heel effect

Question 26

GRID RATIO IN MAMMO

Answer 26

4:1 material is carbon not Pb

Question 27

moving grid

Answer 27

grid moves while you acquire so you don't get image of grid lines in image

Question 28

benefits of using compression

Answer 28

-reduce background -reduce scatter -reduce motion -reduce attenuation (ie lower dose)

Question 29

pros and cons of using magnification

Answer 29

-can gain more resolution because you spread over more pixels -results in more blurr, but can compensate by using smaller focal spot -if you use smaller focal spot, magnification yields better MTF -reduces scatter radiation, removes need for grid -however smaller focal spot= longer exposure time. Can get more motion blurr

Question 30

are parrallex and crossover issues in mammo?

Answer 30

no because mammo only uses 1 screen

Question 31

entrance skin exposure in mammo

Answer 31

500-1000 mR for 4.5 cm breast -with kV constant, increasing 1 cm in thickness requires 2x mAs and 2x skin dose

Question 32

direct amorphous Se detector

Answer 32

-no blurring -xrays strike Se- electrons are released and travel to the detector under E field

Question 33

indirect flat panel detector

Answer 33

-CsI converts xrays to light- detected by flat panel detector -detector elements build up charge when exposed to light

Question 34

charged coupled device

Answer 34

-light released by screen is focused onto CCD by fiber optic tapers -visible light falls on pixel- electrons are liberated and stored in each pixel

Question 35

higher DQE, flat panels, CR, or screen film?

Answer 35

flat panels have higher DQE than CR and screen film

Question 36

formula for mammo HVL

Answer 36

HVL > kV/100+ a constant constant is 0.03-0.3 mm

Question 37

MRI vs mammo

Answer 37

-MRI more useful than mammo for detecting invasive breast cancer -less useful for micro-calcifications

Question 38

US vs mammo

Answer 38

US cannot detect microcalcifications. It can: -distinguish solid lump from cyst -guide biopsy needle -detect met. in lymph nodes

Question 39

mammo imaging parameters

Answer 39

25-34 kVp, 100 mA, 1-2 s

Question 40

mammo power rating

Answer 40

3 kW

Question 41

In mammography, breast compression typically reduces the scatter-to-primary (i.e., unscattered) ratio from _____ to _____. A. 0.8–1.0; 0.4–0.5 B. 0.6–0.8; 0.4–0.5 C. 0.8–1.0; 0.1–0.2 D. 0.6–0.8; 0.1–0.2 E. Breast compression does not improve the scatter-to-primary ration at all, but simply serves to reduce motion blurring by immobilizing the breast.

Answer 41

0.8–1.0; 0.4–0.5 Breast compression minimizes the path length of x-rays through the breast and, therefore, reduces the likelihood of Compton scatter of the x-rays. As a result, breast compression typically reduces the scatter-to-primary ratio by about one-half, from 0.8–1.0 to 0.4–0.5, and thereby improves image contrast and lesion detectability.