COST B11

Quantitation of Magnetic Resonance Image Texture

BRUSSELS WORKING GROUP - 25th - 28th June, 1998

A Review of Texture Methods and Applications in MRI

R E P O R T

Download MS-Word document: rbl3221.doc


Present:
 
Dr R A Lerski, Dundee  Dr Y Rolland, Rennes 
Prof Dr L R Schad, Heidelberg  Dr M Bock, Heidelberg 
Prof Dr A Materka, Lódz  Dr M Strzelecki, Lódz 
Mr P Szczypinski, Lódz  Prof A Spisni, Parma 
Prof Dr R Dommisse, Antwerp  Dr P Ring, Copenhagen 
Dr O Yu, Strasbourg  Ms S Allein, Brussels
Dr H Stødkilde-Jørgensen, Aarhus Ass Prof A Santos, Madrid 
Mr N Malpica, Madrid  Prof R Muller, Mons 
Mr A Amorison, Mons  Mr H Langenberger, Vienna 
Ass Prof A Lundervold, Bergen  Mrs A Barclay, Dundee 
 

Thursday 25th June, 1998

1) Welcome and Introductions

The proceedings commenced with R Lerski (Chairman, Cost B11) welcoming everyone to Brussels for the first Working Group meeting of COST Action B11, for which there is funding for the next four years (started March 1998).
A presentation was given by R Lerski to explain the methods by which the COST programme functions, along with some of the bureaucracy involved. In particular, reimbursement to delegates appears to take around 3 months, but Dr Lerski will write to see if this can be "speeded up".
R Lerski has applied for a subsidy to set up a Web-page describing the Action, but so far, this has been blocked by the Commission. It is hoped that this is temporary.
 

2) Presentation by Dr Y Rolland - The Clinical Value of Texture Analysis

Y Rolland started by stating that the questions to be answered were:
        "The problems yesterday - can we perform texture analysis"?
        "The problems today - how to perform texture analysis"?
 
He commented that it was technically easy to carry out texture analysis but often the exact purpose of the experiment is not clear. It is easy to demonstrate results, but not so easy to compare the clinical value. He also proposed that texture analysis could be added to information already available to Radiologists in order to find a better diagnosis.
  R Muller asked in what specific cases it may be helpful. Would it be help for the image discrimination and help for the diagnosis, as they are two different things? In some pathologies there is no real requirement for texture.   Y Rolland stated that it was difficult to know how to use it:
  a) Do it manually, e.g., as a radiologist with visual interpretation?
b) Do it with computer, i.e., as we propose with NMRWin.
 
He recommended writing exactly what one is reporting - try to standardise.   L Schad - aim from beginning - is it better to have tissue characterisation now we have texture? He said that he hoped it would be possible to differentiate between normal and abnormal tissue, but asked the questions:
  a) How we can normalise?
b) How we can standardise?
 
H Stødkilde-Jørgensen commented that it would probably be necessary to try to combine texture analysis with other information.   R Lerski stated that, in his experience of texture analysis in MRI, it was usual to experience different results on the same machine and also on different machines. He also mentioned that, so far, the technique and protocol have not been sufficiently developed and that some means of standardisation or processing would be necessary.   M Bock thought it necessary to have specific information as to exactly what we would be looking for in pathological terms so that we can predict which parameter would be good, and which ones would not be.  
 
3) Presentation by R Lerski - Texture Analysis in Ultrasound and X-ray A review was given of the results achieved by texture analysis in X-ray and in ultrasound. These date back to 1976.   R Muller asked - "What was the end image". If the liver was cirrhotic or normal - can you see any difference on CT? Y Rolland replied that there were not many differences.   Y Rolland also stated that it wasn?t clear in the case of ultrasound what the pixel meant as the resolution is too poor, therefore it is not obvious what you are looking at or measuring.  
 
4) Presentation by Prof Dr L R Schad - Texture analysis in MRI and status of NMRWin L Schad gave a full review of the usefulness of texture analysis in MRI and commented that he would want to find out where the limits are and what are the best parameters.

A Lundervold queried whether the results of all echoes or only a single echo were used.

  L Schad replied that 4 images were usually used: T1 parameter image mono exp
T2 parameter image mono exp
T1 dependent image
T2 dependent image
 
Most radiologists use all or some of these images for diagnosis
   
Friday 26th June, 1998   1) Presentation by Dr R A Lerski - Results and Methods An introduction was given of this session, viz., the methods of texture analysis, multiparameter evaluation and test object results from the Biomed Concerted Action.   2) Presentation by Prof Dr A Materka - Texture Analysis Methods A full report was distributed summarising an initial summary of the literature in texture analysis. A detailed and excellent review was given of the various methods available and an example of an application in skin pathology was presented.   Y Rolland asked about the work done on skin pathology - is it worth doing it? A Materka?s reply was that, yes, his clinical collaborators think so, and that is the important issue.   Y Rolland commented that a method for identifying discriminating parameters can always be found.   3) Presentation by Ass Prof A Santos - Multiparameter evaluation methods A detailed review was given of the various methods available to evaluate the texture parameter results, e.g., discriminant analysis, principal component analysis (PCA), neural networks.   A Materka asked if PCA can be used for image classification. The reply was that it is useful if there are a lot of variables and also a useful tool for research.   4) Presentation by Dr R A Lerski - Test Object Construction and Results R Lerski explained the construction of the Test Objects, and subsequent results, from the previous BIOMED Concerted Action.   R Lerski continued by asking the following questions: a) Why is the study on individual machines so different?
b) What is it that changes the parameters?
c) Is it signal-to-noise?
d) Is it different field strengths?
 
M Bock asked about the difference between Siemens and Philips machines. S Allein commented that she thought the different fields strengths were a very important factor due to possible susceptibility difficulties with the test objects.

A Lundervold wondered if it may be the calibration of the reconstruction algorithms.

  R Lerski thought it may be the same argument as with T1 and T2. That is, it is important to very carefully determine how to carry out the measurements well before deciding on their value.   A Lundervold suggested that it may not be possible to measure at different centres, but it would nevertheless be good to get the same separation of textures on different machines.   H Stødkilde-Jørgensen asked whether the measurements had been completed on the same scanners, to which R Lerski replied that they were, however, the variation wasn?t as much. The same test tubes were also sent round the various centres.   R Lerski suggested it may be a good idea to scan the tubes very extensively for 3/4 days on one machine and then spend time analysing the data.   L Schad commented that he wasn?t really sure if the same parameters were used in the image reconstruction by all manufacturers or in all machines, and suggested it may be better to do the reconstruction using Fourier transform ourselves to determine that the settings were actually the same.   R Lerski stated that maybe we should have distributed the actual sequence to all centres.   Y Rolland wondered why MR was used instead of CT, which has less parameters and may be simpler to understand. L Schad replied that MR had a better soft tissue contrast. Nevertheless, Y Rolland suggested trying CT with foam only.   A Lundervold thought maybe another sequence would be more relevant, e.g. diffusion. Wouldn?t the biological tissue be more obviously different? He asked if variability mattered - many other parameters that can be used. R Lerski stated that trabecular bone had been used for same experiments but didn?t get very good separation.   L Schad suggested that if we changed to other parameters (e.g. diffusion, perfusion) he doesn?t think different lesions would be separated. We would have to first find out which machine parameters influence our outcome.   A Santos asked if particular texture parameters are machine dependent. R Lerski thought we should look at this as there is enough existing data to carry this out, and it would give a better indication of problems before carrying out a new trial.   A Santos has access to a 4.7 Tesla machine and R Lerski to a 7 Tesla system.   R Lerski - Assuming that texture is same as tube is moved across - maybe more than 6 ROIs should be taken, and that maybe something better than foam tubes could be used.   R Lerski commented that trabecular bone is not easy to get in lower age groups and that it is a problem to remove the tissue out of the bone. Also, the texture is not the same over the whole area of bone.   L Schad suggested the possibility of sending someone round each centre involved to measure the test objects or tubes, and asked if it could be done as a short term mission. This would also ensure that all parameters would definitely be the same.  
 
GENERAL DISCUSSION   1) Clinical Problem Technical point of view - organ with not much image artefacts is required.  

DATA COLLECTION

1) Markov - Texture Foam (simulation)

Noise (residuals)
  2) Re-analysis of foams and estimate SNR in gel Have been measured already: Different FOV
Different NSA
Different Resolution
Different Slice Width
 
SOFTWARE
- Store ROI data (pixel values)
 
Groups with access to MATLAB:   Lódz
                                Bergen
                                Copenhagen
                                Aarhus
                                Madrid
                                Strasbourg
                                Brussels
                                Parma ?
Groups with access to IDL:      Copenhagen
                                Antwerp
                                Heidelberg
                                Madrid
Need a full specification for ROI pixel storage.
 

PARAMETER EVALUATION
 

UNSCRAMBLER (PC or UNIX)   }
R (S/Plus)                 } Commercial
SPSS                       } Packages
MATLAB                     }
SAS                        }
Data on Excel (macro) - R Lerski to send to read log files.
TEST OBJECTS
Foams ?         -     Reticulated
Biological?     -     Trabecular bone
Anything else?
Existing trial images for downloading - R Lerski to send out.
Foams - composite object, sepharose, HPLC - 300 microm ? - Perkin Elmer, gels - polysaccharide, fibres, membrane   PURE MATHEMATICS
 
The present situation is as shown:

 

Histogram equalisation could be attempted

 

Could try a sum of parameters from brain and foam tubes to normalise.

Literature (time for mission)
Texture model (big task)
Internal exchange of partners
Weiner Spectrum

 

CONCLUSIONS
 

Clinical problem:
White matter brain
Trabecular bone
Dynamic effects (texture in time domain and spatial domain)
Same ROI in a series of slices
Breast MRI - contrast enhanced
Functional MRI
 

Saturday 28th June, 1998

TASKS

1)     Functional MRI

Existing data - texture analysis
Aarhus, Bergen, Strasbourg and Mons
2)     Library search - Lódz

3)     Markov - Lódz

4)     Variation of texture in reticulated foams with FOV, NSA - Dundee would perform a full analysis

5)     New Data on reticulated foam - SNR constant - Heidelberg (foams from Copenhagen)
 

FINAL CONCLUSIONS

1) Literature
 

Lódz  -->   Heidelberg (short term mission)
2) Data Collection

Existing data

 -->  Lódz - Markov modelling
FTP of existing files - make available from Dundee
FOV, RES, NSA, Slice width
3) New Measurements
 
Foam tubes (4)

SNR Constant  -->   Heidelberg

Coronal cuts
4) Software/NMRWin
 
NMRWin stores ROI - Lódz  --> Heidelberg
Dundee will talk to London about texture routines in MATLAB
 
-->
                Madrid, Bergen and Lódz
DICOM reading - Madrid will investigate
5) PCA
 
Unscrambler - details to all (from Dundee)

Macro from NMRWin to Excel (from Dundee)

Madrid to look at:

ROI data
Parameters from foam (Dundee will send)
6) Foam  -->   X-ray CT and Miscellaneous
 
Rennes will scan the reticulated foams by x-ray CT

Rennes }
Brussels} Wrist machine to investigate

Literature clinical ?hot topics? - Rennes

7) Test Objects
 
Antwerp will think about alternatives

Foams

Sepharose - HPLC

        300 m m
        Parma will investigate

Polysaccharide

Fibres

Gauze ? - Dundee

Embolisation beads - Rennes

Foam - T1, T2 to be changed - Dundee

                    T1 100 at 1.5 Tesla
                    T2 700 "
 

8) Slice Thickness

Does it vary between machines or with sequence protocol?
Plots of the variation of texture parameters with slice width are needed.
For example:
 
Heidelberg will make the measurements, Dundee the analysis.
9) Multicentre Trial
It might be possible to look at the same ?Siemens? sequence
(Vision, Impact)
10) Vienna
Trabecular bones
Tibias
Bruker 3 Tesla
Resolution 100 m m
11) Strasbourg This centre is involved in a study of the contribution of texture analysis in the evaluation of cryptogenic temporal lobe epilepsy. Texture analysis is being applied to standard brain MR imaging of epilepsy patients with studies of the regions of the ipsolateral and controlateral hippocampus and the region of amydata. Texture analysis should be used for the detection of mesial temporary slcerosis and for the assessment of apparently normal structure.   DATE AND VENUE OF NEXT MEETING

Thursday 19th  -->  Saturday 21st/Sunday 22nd November, Strathclyde Graduate Business School, Glasgow, Scotland. Full details to be circulated in September.


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