Mammography & screening

Question 1

Core issues of mammo

Answer 1

1) Low tissue contrast
2) Subtle distortions in breast architecture
3) looking for small object - micro calcs ~0.1mm

Question 2

Mammo geometry

Answer 2

1) FIxed geometry - except in mag
2) Uses anode heel effect
3) Small focal spot

Question 3

Mammo x-ray tube

Answer 3

• Small focal spot
• Low kV (25-35kVp)
• Mo, Rh or W annode
• Mo, Rh Ag or Al filter
• Anode heel effect reduces intensity at nipple edge.

Mostly W target now

Question 4

Impact of filtration

Answer 4

• Removes low E photons
  
  • reduces skin dose
  • increases mean energy of beam
• K edge filters generally used for mammo

Question 5

Effect of k-edge filter

Answer 5

• Filter is relatively transparent below the k-edge
• > char x-rays transmitted
• Signif atten of bremstrah above k-edge
• increases contrast

Question 6

Benefits of compression

Answer 6

• Immobilises breast
• Reduces the dose
• Improves image quality
• Reduces scatter within the breast - thinner tissue

Question 7

Compression systems

Answer 7

Pre-compression : Position before full compression
Tilting paddles: conform better.
Compressibility detection available
Shifting paddle: L-R adjustment

Question 8

Define AEC

Answer 8

Controls amount of radiation at the detector

Ensures correct exposure regardless of thickness / composition

Not used with implants

Must work with vary low rad level due to attenuation

Question 9

AEC types

Answer 9

Basic: mAs

kV selection: dose rate det select on test shot
Adjust based on dose rate

Full auto: filt/voltage based on test shot
target/ filt/volt based on breast thickness
All based on test shot

Question 10

Mammo detector type

Answer 10

Mainly a-Se and CsI with a-Si

Question 11

Advantages and limitations of DR mammo

Answer 11

• Better contrast
performance
• Larger dynamic range
• Improved dose efficiency
• Imaging processing
• PACS
• Lower resolution
• Start-up costs
• Image processing

Question 12

Advantages and limitations of film mammo

Answer 12

Analogue
• Contrast-latitude
compromise
• Limited dynamic range
• No post processing
• Stability of film processing
• Proven technology
• High resolution
• Affordable

Question 13

DR spectrum

Answer 13

Harder more pen beam
reduction in contrast but can inc depth dose to compensate
Film would get too dark, lower patient dose while maintaining im quality

Question 14

Phillips sys

Answer 14

Collimator defs many thin beams which scan accross

No need for a grid

Question 15

Photon counting det features

Answer 15

Electronic noise effectively eliminated
• Secondary carrier noise eliminated
• Digitisation noise eliminated
• DQE potentially improved due to good detection
efficiency coupled with less detector noise
• Response has to be very quick

Question 16

Measurement of mammo dose

Answer 16

Mean glandular dose - at-risk dose

ESD doesn’t take into account changes at depth

Question 17

Measurement of breast dose

Answer 17

• Simulated with PMMA blocks - QA
• Dose surveys
• Calculate entrance surface air kerma
• Derive MGD using HVL and composition dependent
conversion factors

Question 18

NDRL

Answer 18

for 50-60mm thick breast NDRL is < 3.5mGy

Question 19

Define stereo-tactic mammo

Answer 19

Add-on for standard mammo or dedicated

Uses two images recorded at different angles, combined to give depth information - via ref point matching

For placing guide wires

Question 20

Digital breast tomosynthesis

Answer 20

• X-ray tube moves in an arc about a pivot point
• Breast and detector (in general) do not move
• Acquire a series of low dose projections
• Computer reconstructs data into slices at different depths in the breast

removes effect of overlying anatomy

large datasets

Question 21

Breast cancer incidence

Answer 21

1 in 8 women will develop breast cancer

Question 22

Patient Screen requirements

Answer 22

Originally aged 50-64 every 3 years

2005 - 50-70 every 3 years, 2 views

2016 - 43-73 every 3 years

Question 23

Issues with younger women

Answer 23

less common
harder to image
increased risk of induction from screening

Question 24

Protocol for older women

Answer 24

• Routine invites stop at 70

- Can still attend though

Question 25

Risk vs benefit

Answer 25

Risk : 1 induced per 14000 screened 3 times over 10 years (aged 50-70)

Benefit : 1 saved for every 400 over 10 years

Question 26

IRMER refferal

Answer 26

Women invited (referred) for screening if they meet the referral
criteria in the Cancer Reform Strategy document. Invitation letter
is signed by director of screening centre (or lead radiologist). No
individual signed request.

Question 27

Irmer just / auth

Answer 27

• Radiologist, breast clinician or breast screening radiographers
are practitioners
• Identity of woman and eligibility confirmed before authorising
exposure.
• Consider previous screening history
• Record kept that woman meets local and national criteria
• Record confirming that examination has been justified,
authorised and by whom.

Question 28

Exemptions to standard protocol

Answer 28

Women who have recently been screened
• Women who attend without invitation
• Women over current age range
• Partial examinations
• Technical recalls and repeats