Transcript Threshold studies for a new compression algorithm for

Threshold studies for a new
compression algorithm for
mammographic images
Dr R W Grant Dr M Alsewan
Dr G Kaplan Dr R Given-Wilson
London Radiologists
Dr G Schaefer, Nottingham Trent University
Dr C Lawinski Director KCARE
Software and trial supported by Mr M Devlin
Purpose

Assess a new software programme


To enable the management of ever larger
radiological image files
Examine the implications for
Assembling
 Data transfer
 Archiving of images
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
Mammography was chosen as the segment
providing the greatest challenge
Material and Methods

We applied differing compression levels to
Digitised and Dicom based Mammograms
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
Using a combination of wavelet and DCT-based
image compression.
256 AES encryption algorithm to protect data

above the requirement for the UK and European
Data Protection Acts.
Material and Methods
CR and Digitised Mammograms subjected to
varying levels of compression
Material and Methods
Dicom Mammograms
Material and Methods
Original
VL5
Digitised Mammograms
Material and Methods
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A further study was completed by Kcare with
3 Mammography Quality Control Phantoms
using a CR system.
Pixel Change comparator analysis by
comparing the intensity of each pixel value in
the original and compressed/extracted image.
Results
Validation I - Analysis by team of experienced radiologists
Results
Validation I - Analysis by team of experienced radiologists
Results
Results
Validation II 3 Mammography Quality Control Phantoms using a CR system.
Results
TOR MAX
Normal
Lossles
s
VL2
VL3
VL4
VL5
Low contrast 6 mm circular
details
Number observed (1)
Minimum detectable contrast
(%)
9
0.58
8
0.83
9
0.58
8
0.83
8
0.83
6
1.6
5
2.0
> 1.2
High contrast 0.5 mm
details
Number observed (1)
Minimum detectable contrast
(%)
10
2.0
10
2.0
10
2.0
9
2.7
9
2.7
8
5.4
8
5.4
>5
High contrast 0.25 mm
details
Number observed (1)
Minimum detectable contrast
(%)
9
2.7
9
2.7
8
5.4
8
5.4
8
5.4
7
8.3
7
8.3
>8
VL6
Remedial
Level
Results
TOR MAM
Lossless
Normal
VL2
VL3
VL4
VL5
VL6
Filaments
33
34
32
32
31
28
23
Particles
11
12
12
12
12
11
10
Circular
details
22
22
21
22
20
19
15
Total score
(5)
66
68
65
66
63
58
48
Remedial
Level
72 to 82
Results
CDMAM
Conclusion
Validation I - Analysis by team of experienced radiologists
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When dealing with medical images for review we can adopt a
compression level termed “Visually Lossless”.
This method of compression produces an image that is "visually
impossible to differentiate from the original", however there is
still loss involved in the compression.
All compression levels provided diagnostically acceptable images.
A compression ratio of 65 to 1 provides an excellent
compromise between transmission time and compression level.
Conclusion
Validation II - Conclusions by KCARE
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The results for the three test objects are generally
similar.
Considering the uncertainties in scoring
 Lossless and the VL2 and VL3 images show little
significant loss in image quality.
 The VL4 images indicate a slightly greater loss in
image quality
 A significant loss is seen in VL5 and VL6 images.
Significance

Compression of mammograms would allow double reporting to
be undertaken remotely, either by the second reader who may be
on leave, or by another Centre providing locum cover for
holidays, illness etc.

A days list of 25 patients may produce 850MB of data for CR or
3.5GB for FFD to be transmitted
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Compressed images all benefit from “noise” reduction
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Apply the above compression levels and this transmission is
reduced to 5 and 20 minutes respectively.

The potential for arbitration to reach consensus view on difficult
cases by EXPERT PANEL could radically alter the field of
litigation.
Significance

The compression software not only works well
with mammography but also with CT, MRI,
Cardiac Angiograms and Nuclear Medicine
Thank You For Your Time
Contact details:
 Compression software: [email protected]
 KCARE: [email protected]
 Presenter:: [email protected]
90mb MRI scan encrypted & compressed to 5mb and
sent via email to home PC of Dr Guttman
Dr Guttman reported that the Quality of extracted file’s
was “Good” Upload and download time reduced from
104 minutes to 11 minutes