GRID in Mammography, COMPRESSION in Mammography, AEC in Mammography, IMAGE RECEPTORS, MAGNIFICATION MAMMOGRAPHY

1. PRESENTED BY:-
Sujata Das
B.Sc.MIT-2015
BPKIHS

2.  X-RAY TUBE
 ADVANCEMENT IN
MAMMOGRAPHY
 GRID
 COMPRESSION
 AEC
 IMAGE RECEPTORS
 MAGNIFICATION
MAMMOGRAPHY

4.  Grids are used to reject scatter.
 Placed between the breast and image
receptor.
 Moving grid with a grid ratio of 4:1 to
5:1 are typical .
 Higher grids ratio provide greater x-
ray scatter removal but also a greater
dose.
 Grids frequencies ranges from 30 to
50 lines/cm for moving grids and up
to 80 lines/cm for stationary grids.

5.  Creates better images by reducing x-ray
scatter .
 Automatic self –adjusting tilt paddle
ensures uniform compression of the
breast tissue .
 Reduces procedures time by about 10 %
and enhance patient comport.
 Copper as grid strip and air as
interspace with 3.8:1 grid ratio

7.  Compression is achieved with a low
attenuation lexan paddle attached
to compression device.
 Parallel to the receptor surface
 10 to 20 newton of force is typically
used
 Improves spatial resolution
,contrast resolution and reduces
patient dose.
 The principle drawback of
compression ; patient discomport.

9.  AEC employs phototimer to measures X-ray intensity
and quality.
 Kept after the image receptor ;to minimize the object
to image distance -improves spatial resolution.
 Automatically calculates the exposures time that is
required to produced optimum density on the film.
 When the required optimum density is produced ,the
AEC terminate the exposure and reduces the dose.

10.  Two types of AEC used ionization chamber and solid
state diode.
 Allows assessment of breast composition and selection
of proper target/filter combination
 For thick dense breasts are imaged better with Rh/Rh ;
thin fatty breast are imaged better with Mo/Mo.

11.  Four types of images receptor have been used in
mammography.
1. Direct –exposure film
2. Xeroradiography
3. Screen-film
4. Digital detector

12.  Direct –exposure film ; once used for small body parts
measuring less than 10 cm. Requires 10 to 100 time
more exposure .no longer used.
 Xeroradiography; this techniques gives low contrast
images.

13. • Used single phosphor screen and single emulsion flim
with cubic grain emulsion.
• The emulsion surface of the film must face the screen
to prevent the resolution due to light diffusion in the
screen.
• The use of intensifying screen to increase the speed of
imaging system resulting in a low patient dose and
increase image contrast.
• Gadolinium oxysulphide (Gd2O2S:Tb)is used as
phosphor and resolution of approx 12 lp/mm

15.  No film or chemical processing is used
 Thallium activated cesium iodide used as phosphor.
 This phosphor can be grown as parallel needle like
light pipes for improved spatial resolution(5lp/mm)
.

16.  Magnification techniques are used frequently in
mammography to produced images up to twice the
normal size.
 Magnification mammography requires special
equipment such as micro focus tubes, adequate
compression , patient positioning devices.
 The purpose is to investigate small ,suspicious lesions
or micro calcifications.

17.  Magnification of 1.5x to
2.0 x is used
 Increased effective
resolution of the image
receptor by the
magnificator.
 Small focal spot
size(0.1mm)used
 Reduction of scatter

18.  High patients dose
 Long exposure times
(small focal spot ,low
MA)
Patient motion and blur

19.  FDA Dose limit
 3 mGy (w/grid)
 Mean glandular dose
 Single view
 4.5cm compressed breast
 Average composition