Mammographic Technology

Question 1

Equipment Requirements

Answer 1

Specifically designed for the diversity of pathology

Needs to be efficient and effective (screening programme)

Low dose (screening programme / radiosensitive organ)

These structures are seen as mixed densities on mammo but are not that dissimilar (unlike like bone and soft tissue)
Pathologies are also similar densities to these structures – so it is important for the equipment to be designed to differentiate these structures.

Question 2

Why not use ultrasound?

Answer 2

Mammo is used for older ladies and ultrasound is used for younger ladies
As the breast becomes less dense as we age
Ultrasound takes longer but can be targeted at a certain area

Question 3

Same design as general xray tube, but:

Answer 3

Tube voltage ~ 20-35kV
Anode heel effect 
   Cathode towards thorax 
    Anode towards nipple 
Auto-Collimators 
Fixed SID ~ 65cm
Focal spot size ~ 0.3-0.15mm

Mammography uses a spectrum of energies. This is formed by:
Tube voltage (kVp) – 25-35
Target Material
Filters

Question 4

Target – chosen for the type of characteristic xrays

Answer 4

Molybdenum
Rhodium
Can also be tungsten (usually used in xray tubes)

Question 5

Filter – will attenuate the low energy xrays that will alternatively contribute to skin dose

Answer 5

Molybdenum
Rhodium
Silver
Aluminium

Question 6

Breasts come in various densities and compositions

how do we cater to this?

Answer 6

To cater for this, equipment has switchable target & filter materials.
A. Moly/Moly
B. Rh/Rh
C. W/Al

Question 7

AOP Automatic optimisation of parameters

Answer 7

Gives a small low dose pre-exposure
Determine the exposure factors, target material and filter material needed
Provides optimal image quality whilst minimizing dose.

Question 8

AEC

Answer 8

Detects when the detector has received optimal exposure

Terminates exposure

Question 9

Digital breast tomosynthesis (DBT)

Answer 9

Overcomes the issue of overlying structures – 2D image of a 3D structure
Creates volume of data which can be viewed in slices 
Can determine depth of structures
Same equipment (optimized for DBT) taking images at angles over the breast

Question 10

Stereotactic Biopsies / Procedures

Answer 10

Images were taken intermittently between carrying out the procedure
The system calculates where to send needle and how deep lesion is

Question 11

Whats different about the focal spot in mammo compared to normal xray?

Answer 11

Mammo has smaller focal spot to help with spatial resolution since its looking at only the breast tissue and not loads of structures.