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tissue ablation model by comsol

Posted Mar 30, 2014, 10:51 a.m. EDT Version 4.3b 10 Replies

Ejiro Umaka
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Concerning the tumor ablation model, can someone tell how to get the volume of tissue heated within an isothermal surface. In the model an isothermal surface of 50˚C was done after 8minutes, however, I not only want to find the volume of tissue within this isothermal surface but also want to know the value of the volume with changing time, from t=0 to t=8minutes. How can I calculate the volume at each time instant?
Thanks plenty.
10 Replies Last Post Apr 11, 2014, 9:11 a.m. EDT
Sergei Yushanov Certified Consultant
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Posted: 1 decade ago Mar 31, 2014, 7:51 a.m. EDT
Ejiro,

Under Definitions/Component Coupling/Integration, define operator “intop1” on the domain Geometric level. Then define variable

volume_iso=intop1(T>=50[degC])

to get the volume of tissue heated within an isothermal surface. You can plot variable “volume_iso” as a function of time.

Regards,
Sergei
Ejiro, Under Definitions/Component Coupling/Integration, define operator “intop1” on the domain Geometric level. Then define variable volume_iso=intop1(T>=50[degC]) to get the volume of tissue heated within an isothermal surface. You can plot variable “volume_iso” as a function of time. Regards, Sergei
Ejiro Umaka
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Posted: 1 decade ago Mar 31, 2014, 2:04 p.m. EDT
Thank you!
Thank you!
Ejiro Umaka
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Posted: 1 decade ago Apr 4, 2014, 4:29 p.m. EDT
I later wanted to plot the isothermal volume in temperature ranges: 40˚C<T<50˚C vs time. I do this but get a straight line (attached). I used this on the expression section: intop1(40[degC]<=T<=50[degC]).
The graph I got has a constant volume with changing time even before the steady state condition but I expect the volume to increase with changing time.
I later wanted to plot the isothermal volume in temperature ranges: 40˚C

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Sergei Yushanov Certified Consultant
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Posted: 1 decade ago Apr 7, 2014, 8:14 a.m. EDT
Ejiro,

To calculate this volume use to following expression:
intop1(T>=40[degC])-intop1(T>=50[degC])

Regards,
Sergei
Ejiro, To calculate this volume use to following expression: intop1(T>=40[degC])-intop1(T>=50[degC]) Regards, Sergei
Ejiro Umaka
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Posted: 1 decade ago Apr 7, 2014, 6:45 p.m. EDT
Thanks again. How can I calculate thermal dose for the tissue ablation model using COMSOL.
The mathematical calculation for thermal dose is attached. I ultimately want to plot the thermal dose as a function of distance from the center.

Tr is a constant 43˚C

Thanks again. How can I calculate thermal dose for the tissue ablation model using COMSOL. The mathematical calculation for thermal dose is attached. I ultimately want to plot the thermal dose as a function of distance from the center. Tr is a constant 43˚C

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Sergei Yushanov Certified Consultant
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Posted: 1 decade ago Apr 8, 2014, 7:13 a.m. EDT
Ejiro,

To calculate thermal dose:

-add Domain ODEs and DAEs node
-add Distributed ODE sub-node and define source term as f=(1/3600)*(0.25*(T<=Tr)+0.5*(T>Tr))^(Tr-T). Leave damping and mass coefficients to their default values da=1, ea=0

Most probably, an attempt to solve for temperature and thermal dose simultaneously would cause convergence issues. If this is the case, then add additional Study Step to solve for thermal dose only using previously computed temperature field.

Regards,
Sergei
Ejiro, To calculate thermal dose: -add Domain ODEs and DAEs node -add Distributed ODE sub-node and define source term as f=(1/3600)*(0.25*(TTr))^(Tr-T). Leave damping and mass coefficients to their default values da=1, ea=0 Most probably, an attempt to solve for temperature and thermal dose simultaneously would cause convergence issues. If this is the case, then add additional Study Step to solve for thermal dose only using previously computed temperature field. Regards, Sergei
Ejiro Umaka
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Posted: 1 decade ago Apr 8, 2014, 9:44 a.m. EDT
Thanks. Yes I had to add another study step. How do I get a 2D plot of this data. I seem to be having trouble calling the solution of the thermal dose in the result node.
Thanks. Yes I had to add another study step. How do I get a 2D plot of this data. I seem to be having trouble calling the solution of the thermal dose in the result node.
Sergei Yushanov Certified Consultant
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Posted: 1 decade ago Apr 9, 2014, 8:37 a.m. EDT
Ejiro,

Make sure that solver set up for the thermal dose calculation step is correct. In the Values of Dependent Variables section, check the box “Values of variables not solved for”. From Method selection box select “Solution”. From Study selection box select “Study 1, Time Dependent” (this study step where temperature is calculated). From Time selection box select “All”.

Regards,
Sergei
Ejiro, Make sure that solver set up for the thermal dose calculation step is correct. In the Values of Dependent Variables section, check the box “Values of variables not solved for”. From Method selection box select “Solution”. From Study selection box select “Study 1, Time Dependent” (this study step where temperature is calculated). From Time selection box select “All”. Regards, Sergei
Ejiro Umaka
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Posted: 1 decade ago Apr 9, 2014, 6:01 p.m. EDT
Thanks Sergei for the response. Unfortunately I have still not gotten the results. I attached the steps I took in finding the thermal dose. Is there something I missed?
Thanks Sergei for the response. Unfortunately I have still not gotten the results. I attached the steps I took in finding the thermal dose. Is there something I missed?

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Sergei Yushanov Certified Consultant
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Posted: 1 decade ago Apr 11, 2014, 9:11 a.m. EDT
Ejiro,

Not sure why you are getting incorrect result but if you are still not able to resolve the issue then you might try to calculate the thermal damage integral in the post-processing using operator
timeint(t1,t2,expr,tol,minlen)
Keep in mind that this operator takes time, so play with arguments “tol” and “minlen” to reduce evaluation time.

Regards,
Sergei
Ejiro, Not sure why you are getting incorrect result but if you are still not able to resolve the issue then you might try to calculate the thermal damage integral in the post-processing using operator timeint(t1,t2,expr,tol,minlen) Keep in mind that this operator takes time, so play with arguments “tol” and “minlen” to reduce evaluation time. Regards, Sergei

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