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MRI Workshop CST 15. November Darmstadt

Use of CST Microwave Studio (MWS)
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Tim.Herrmann

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  • Institut: Department of Biometry and Medical Informatics/OvG University Magdeburg/ www.uhf-mri.ovgu.de

MRI Workshop CST 15. November Darmstadt

PostTue 13. Sep 2011, 00:22

Die CST AG veranstaltet am 15. November einen MRI Workshop an dem MWS Nutzer gemeinsam CST Programmierern die Details für eine neue MRI Toolbox erörtern können.

http://www.cst.com/Content/Events/Detai ... entId=2090

Sven Junge und Andreas Bitz haben schon Programmpunkte erörtert und möchten diese zu einer Eckdatensammlung zusammenfügen, um sie auch mit den anderen Mitgliedern zu diskutieren

Ziel: Alle MWS Nutzer des MR-EM Forum sollten diese Eckdatensammlung mitgestalten und unterstützen, damit sie auch im November bei CST Gewicht haben
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Sim_MS

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Re: MRI Workshop CST 15. November Darmstadt

PostTue 1. Nov 2011, 02:16

I have some suggestions for this CST MRI Toolbox.

# a integrated Birdcage builder like the Penn State University tool
# surface coil builder with target frequency optimization (value and number of caps)
# optimized structure export to pcb
# Tx and Rx RF-coil structure (general) templates for 3T and 7T MRI


I hope some this will be in next version of CST MWS
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MR09

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Re: MRI Workshop CST 15. November Darmstadt

PostSun 6. Nov 2011, 18:49

My points, just brainstorming:

- more freedom to move Voxel-models
- integrated examples of different coil types
- better automatic optimizing for resonance frequency
- relevant Data in one statistic (including S-Parameter, SAR, Power Energy (In,Out etc.))
- faster combining of different field parameters with GPU

What do you think, what is really practicable and most important for CST to do first?
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Tim.Herrmann

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Re: MRI Workshop CST 15. November Darmstadt

PostSat 12. Nov 2011, 20:37

MRI-Toolbox – Arbeitserleichterung für Integration von häufig benötigten Arbeitsabläufen:

Vorschläge von Sven Junge und Andreas Bitz:


1) Pre-Processing:

a) Modell-Builder für Loop-Spulen:

- Zirkular, Oktaeder oder rechteckig (Durchmesser D, Leiterbreite W)

- Mit N-kapazitiven Teilungen

- Planar oder auf gekrümmten Oberflächen

b) Modell-Builder für Bircage :

- N-Stäbe der Länge L und Durchmesser D, Leiterbreite Stabe Ws, Breite der Endringe We

- Hochpass

- Tiefpass

- Bandpass

- Mit N-kapazitiven Teilungen auf Endringen bzw. Stäbe

c) Modell-Builder für Solenoid-Spulen

- N-Windungen, Durchmesser D, Länge L, Leiterbreite W

Wünschenswert die Erweiterung von Punkt 1a) auf Arrays mit NxM Elementen

d) Improved implementation of body models:

- Improved meshing of voxel models (reduction of computation time)

- Set mesh according to voxel size of body model

- Improved replacement of tissues by implants/internal coils or dielectric shapes

o Especially, for field plots

- Access to tissue types / tissue numbers for post-processing, e.g.

o SAR evaluation

o B1+ evaluation



2) Post-Processing

a) Post-Processing für Einport/Zweiport-Systeme (Lineare oder Quadraturspulen)

- Automatische Berechnung der auf die akzeptierten Leistungen normierten () Feldverteilungen für E, B1+ und B1- (pro Sendekanal)

- Automatische Berechnung der normierten () B1-Amplitude und relativen Phase zu einem def. Aufpunkt

- Transmit efficiency: B1+/sqrt(SAR)

o Mean B1+ in region of interest or tissue type (e.g. brain, liver)

o Most critical SAR aspect

- Realistische Güten (50 Ohm)

- Zusammengefasste Energiebilanz ohne „Zahlensuche“ -> „OK“, „Failed“

o Calculation of radiated power

- S/N-Berechnung auf der Grundlage von B1+ oder B1+- und den E-Feldern bzw. der Verlustleistung in dielektrisch verlustbehafteten Medien (ggf. Erweiterung auf einfache MR-Sequenzen – und Protonendichte)



b) Erweiterung der oben genannten Punkte auf Post-Processing für Mehrport-Systeme (Arrays)

- G-Faktor-Berechnung

o Depends on field of view

- Rauschkorrelation

- B1-Shimming

o ROI selection, Algorithm

- Ggf. Entkopplung mittels DS

c) SAR Evaluation

- Evaluation of different SAR aspects

o Whole body

o Partial body SAR

o Localized SAR – Trunk/Limbs (10g-averaged)

- SAR evaluation only in selected materials/body tissues

- Alternative: SAR evaluation only for body model

- Implementation of fast SAR-Evaluation based on virtual observation points (VOPs) for multi-channel coils



3) Thermal simulation

- Calculation with different power loss densities (frequency-, time-dependent)

- Alternating transmission with different coils (body coil, local coil)

- Alternating transmission with different excitation modes

- Implementation of CEM43

- Temperature statistics for different materials/tissues



4) „Starter“- MRI-Toolbox:

- automatische Modellgenerierung, Punkt 1)

- Berechnung der Kapazitätswerte für Nutzfrequenz F

- Berechnung der Feldverteilungen für Nutzfrequenz F

- Anwendung von Punkt 2) z.B. Berechnung der normierten () Feldverteilungen für E, B1+ und B1-
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Tim.Herrmann

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Re: MRI Workshop CST 15. November Darmstadt

PostWed 21. Dec 2011, 14:48

Protocol: CST MRI-User Meeting at 15.11.2011

MRI Toolbox - An easier way for integration of frequently used workflows:
1) Pre-processing:
a) Model Builder for loop coils:
b) Model Builder for Bird cage:
c) Model Builder for solenoid coils
Desirable extension of the point 1a) of N × M array elements

Point’s 1a-1c was classified by participants as not so important. --> No implementation but
the Magdeburg group would provide some general RF-coil models to give beginners the possibility for an easier excess in RF-coil simulation.

d) Improved implementation of human body models:
- More freedom to move voxel models
- Improved meshing of voxel models (reduction of computation time)
- Set mesh according to size of body voxel model
- Improved replacement of tissues by implants /coils or internal dielectric shapes

 1d) was classified by participants as interesting. It is planned for release CST 2013.
The implementation is still open.

o Especially, for field plots
- Access to tissue types / tissue numbers for post-processing, e.g.
 CST is still working on

o SAR evaluation
o B1+ evaluation
 Classified by participants as very important. Is now part of CST 2011 SRP5

2) Post-Processing
a) Post-Processing for one-port / two-port systems (linear or quadrature coil)

- GPU acceleration for field combining
 Was classified by participants as important.Implementation of CST will be hopefully
CST Comment: GPU speedup for post processing is inefficient because the HD-Drive is
slow down the combination of the huge field map data ( it is
recommended to use SSD drive architecture)


- Automatic calculation of the accepted power, normalized (√W) to the field distributions for E, B1 and B1 + (per transmit channel)
- Calculation of normalized (√W) B1 amplitude and relative phase at a defined point
Was classified by participants as very important. Will be implemented in CST 2012 SRP X.




- Transmit efficiency: B1+/√SARmax
Was classified by participants as important. Will be implemented in CST 2012 SRP X.

o Mean B1+ in tissue type or region of interest (e.g. brain, liver)
Was classified by participants as very important. Is now part of CST 2011 SRP5.

o Most critical aspect SAR
- Realistic Q (50 ohms)
Was classified by participants as very important. This topic still requires more discussion (in a smaller round) for a practical MRI implementation.
- Summarized energy balance without long searching in the GUI -> "OK", "Failed"
Energy balance is available already but not summarized this will be implemented in CST 2013.


o Calculation of radiated power
Was classified by participants as interesting and is already in CST 2011


- S/N were calculated on the basis of B1+ or B1+- and the E-fields (power dissipation) in lossy dielectric materials (if possible: extension to simple MR sequences - and proton density)

Was classified by participants as very important. The implementation was discussed and Mr. Freytag (Bruker) has agreed to send a draft of a macro to CST. This topic still requires more discussion (in a smaller round) for a practical MRI implementation.



b) Extension of the above points to post-processing for multi-port systems (arrays)
- G-factor calculation -> Depends on field of view
- Noise correlation
Was classified by participants as very important. Implementation of CST will be hopefully.
Joerg Felder (FZ Jülich) has agreed to assist CST by the implementation.

- B1-shimming
- ROI selection, Algorithm
If necessary, Decoupling using Design Studio (DS)
Was classified by participants as less important

c) SAR Evaluation
- Evaluation of different SAR aspects
o Whole Body
is already part CST 2011
o partial body SAR
is already implemented in CST 2011 with user defined coordinates points. The automatization will investigated by CST.

o Localized SAR - Trunk / Limbs (10g-averaged)
- SAR evaluation in only selected materials / body tissues
- Alternative: SAR evaluation only for body model
Will be implemented in CST 2012 SRP X.





- Implementation of fast SAR evaluation based on virtual observation points (VOP) for multi-channel coils
Was classified by participants as important but in a to early state for implementation. CST refers to the already existing tools.

d) Export
- Improved export structure on PCB (3D to 2D)
Was classified by participants as less important

3) Thermal simulation
- Calculation with different power loss densities (frequency-, time-dependent)
- Alternating transmission with different coils (body coil, local coil)
- Alternating transmission with different excitation modes
- Implementation of CEM43
- Temperature statistics for different materials/tissues
Was classified by participants as less important

4) "Starter" - MRI toolbox:
- Automatic model generation, item 1)
- Calculation of the capacitance values for fundamental frequency F
- Calculation of the field distributions of fundamental frequency F
- Application of item 2) for b. Calculation of the normalized () field distributions for E, B1 + and B1-
Was classified by participants as less important

Summary:
The participants hope for a fast implementation by CST for following points:
For 1-port and multi-port systems!
Automatic calculation of the accepted power, normalized (√W) to the field distributions for E, B1 and B1 + (per transmit channel)
Automatic calculation of normalized (√W) B1 amplitude and relative phase at a defined point
Transmit efficiency: B1+/√SAR
Mean B1+ in region of interest or tissue type (e.g. brain, liver) – Most critical SAR aspect
G-factor calculation
Noise correlation
Especially, for field plots
- Access to tissue types / tissue numbers for post-processing, e.g.
- SAR evaluation
- B1+ evaluation
S/N- calculation
Attachments
CST MRI-Workshop_Protocol_eng_final.pdf
protocol as PDF
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