GI Nodes Eli5

[Haybrant]

Does anyone have a resource that shows all the crazy GI nodal volumes. Its always been a knowledge gap bc I dont think I ever got taught it well, and it seems like everyone always knows these. Theres perigastric, celiac, splenic, portal, suprapancreatic, pericholedocal, gastrojejunal/hepatojejunal/pancjejunal. How in the world do you remember what to cover when. Like wtf, just treat 3D and be done with it. Anyway, need to know it for the boards

Also, can I get an ELI5 (explain to me like Im 5) on fields for breast monoiso and 2 iso setup and what segments and field and field is and that jazz. I understand what it means to match the divergence of the field. But do you half beam block for both mono and 2 iso technique? Where do you place the 2nd Iso? Also, how does the therapist ensure that the fields match appropriately. Just want to be sure I have this down tight. Thank you all

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[thesauce]

Does anyone have a resource that shows all the crazy GI nodal volumes. Its always been a knowledge gap bc I dont think I ever got taught it well, and it seems like everyone always knows these. Theres perigastric, celiac, splenic, portal, suprapancreatic, pericholedocal, gastrojejunal/hepatojejunal/pancjejunal. How in the world do you remember what to cover when. Like wtf, just treat 3D and be done with it. Anyway, need to know it for the boards

Also, can I get an ELI5 (explain to me like Im 5) on fields for breast monoiso and 2 iso setup and what segments and field and field is and that jazz. I understand what it means to match the divergence of the field. But do you half beam block for both mono and 2 iso technique? Where do you place the 2nd Iso? Also, how does the therapist ensure that the fields match appropriately. Just want to be sure I have this down tight. Thank you all

Try to do monoisocentric if possible (breast less than 20cm). Iso at inferior portion of clavicular head. Half-beam block there.

If breast is greater than 20cm, then need 2 iso technique. For that, breast iso is dropped and SCV iso is still at inferior portion of clavicular head. Still half-beam block on SCV, but have to kick the couch away on tangent fields to match and ensure no divergence into SCV. Can do this with BEV on tangents and kick until it lines up or there's an equation for this match which I think is arctan(0.5*tangent field length/SAD)

Anyone else have input?

 

[Haybrant]

Try to do monoisocentric if possible (breast less than 20cm). Iso at inferior portion of clavicular head. Half-beam block there.

If breast is greater than 20cm, then need 2 iso technique. For that, breast iso is dropped and SCV iso is still at inferior portion of clavicular head. Still half-beam block on SCV, but have to kick the couch away on tangent fields to match and ensure no divergence into SCV. Can do this with BEV on tangents and kick until it lines up or there's an equation for this match which I think is arctan(0.5*tangent field length/SAD)

Anyone else have input?

Thanks Sauce. Where does that 2nd iso go, just in the breast? Ive seen people put it at the vert body so you can tattoo but not sure what is appropriate for boards. Do the therapists go in after the tangent treatment, manual kick the couch away from the beam and that is it. Or do they have to line this up on the field too. I just feel there is some imprecision to the match that must be accounted for that I am missing. Can you also ELI5 me collimator rotation vs gantry rotation in setting up the tangents if you know that. Thank you,

 

[napoleondynamite]

Thanks Sauce. Where does that 2nd iso go, just in the breast? Ive seen people put it at the vert body so you can tattoo but not sure what is appropriate for boards. Do the therapists go in after the tangent treatment, manual kick the couch away from the beam and that is it. Or do they have to line this up on the field too. I just feel there is some imprecision to the match that must be accounted for that I am missing. Can you also ELI5 me collimator rotation vs gantry rotation in setting up the tangents if you know that. Thank you,

Vertebral body? I haven't seen that.. Usually I've seen the breast iso placed about 1/3 of the way anterior from the chest wall to the skin in the middle of the breast (or 2/3's deep would be the other way to think of it).

It would be good to spend some time with your dosimetrist and go over the two techniques in detail. Understand how YOU do it and just be able to explain it. There are many ways to skin a cat, just be able to confidently explain the way you do it and you will be fine. When I was studying for orals I booked a couple of hours with my dosimetrist to go over this and it was some of the best study time I had..

As to the junction, there are ways to feather that with field in field and the MLC's at the junction. But again, just spend some time with your own peeps to understand how you are doing it.

 

[mpdoc2]

I think you're talking about setup points in the vertebra. The isocenter is a shift from the setup points. Some places tattoo a setup point as opposed to the isocenter and shift from the setup point to get to the iso.

 

[mpdoc2]

Thanks Sauce. Where does that 2nd iso go, just in the breast? Ive seen people put it at the vert body so you can tattoo but not sure what is appropriate for boards. Do the therapists go in after the tangent treatment, manual kick the couch away from the beam and that is it. Or do they have to line this up on the field too. I just feel there is some imprecision to the match that must be accounted for that I am missing. Can you also ELI5 me collimator rotation vs gantry rotation in setting up the tangents if you know that. Thank you,

Like Napolean said the second iso is in the breast. Some put it 1 cm anterior to the chest wall at mid seperation (others put it 1/3 of the way as Napolean stated). The couch kick auto vs manual depends on the machine but only happens for the dual isocenter technique to match the superior border of the tangent fields with the inferior border of the SCV field.

Gantry rotation is so that the posterior borders of the medial and lateral tangents match (requires over rotation based on the formula 2*arctan(1/2 fieldlegnth/SAD). Collimator rotation is so that the tangents are also aligned to the chest wall.

 

[Neuronix]

http://www.ncbi.nlm.nih.gov/pubmed/19375186

I like this paper for esophageal and gastric. I don't think it was used in any of the major phase 3 randomized trials (e.g. CROSS).

 

[Pewl]

Thanks Sauce. Where does that 2nd iso go, just in the breast? Ive seen people put it at the vert body so you can tattoo but not sure what is appropriate for boards. Do the therapists go in after the tangent treatment, manual kick the couch away from the beam and that is it. Or do they have to line this up on the field too. I just feel there is some imprecision to the match that must be accounted for that I am missing. Can you also ELI5 me collimator rotation vs gantry rotation in setting up the tangents if you know that. Thank you,

For dual isocenter technique I would put the tangent isocenter halfway between the superior and inferior border of the tangents and at the lung/chest wall interface. For oral boards I'm pretty sure they will have you explain both the mono and dual isocenter technique so make sure you have it down.

 

[radiaterMike]

You won't have to explain both approaches only the approach you use (or say you use). The examiner is testing how you work up and manage patients.


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[medgator]

You won't have to explain both approaches only the approach you use (or say you use). The examiner is testing how you work up and manage patients.


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Until they tell you your tomotherapy machine broke and you have to treat a CSI patient on a standard linac

 

[radiaterMike]

Well maybe there's that.


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[Haybrant]

It would be good to spend some time with your dosimetrist and go over the two techniques in detail. Understand how YOU do it and just be able to explain it. There are many ways to skin a cat, just be able to confidently explain the way you do it and you will be fine. When I was studying for orals I booked a couple of hours with my dosimetrist to go over this and it was some of the best study time I had..

maybe I should also have the dosimetrist explain pediatric CSI for protons, and gamma knife optimization for AVMs. The ridiculous thing about these boards is that if we dont treat a particular site you still have to know it like you do. Some dosimetrists and physists dont even speak english, some of them dont know wtf theyre talking about. So Im here to ask for help, this is not about what you did. If that session was so helpful why dont you share some of the other helpful stuff you leared here that we would find useful on boards. Seriously not joking, it would help alot, what else can you tell us that would be useful

 

[napoleondynamite]

maybe I should also have the dosimetrist explain pediatric CSI for protons, and gamma knife optimization for AVMs. The ridiculous thing about these boards is that if we dont treat a particular site you still have to know it like you do. Some dosimetrists and physists dont even speak english, some of them dont know wtf theyre talking about. So Im here to ask for help, this is not about what you did. If that session was so helpful why dont you share some of the other helpful stuff you leared here that we would find useful on boards. Seriously not joking, it would help alot, what else can you tell us that would be useful

Oh gimme a break dude. Seriously. I know you're under stress studying for the worst exam of your life, so I'll cut you some slack, but honestly. All I was saying is that some of this stuff is much easier seen than explained and probably would take less time. These breast techniques are not at all akin to CSI protons or gamma knife for AVM - this is bread and butter that most any dosimetrist should be competent walking you through. My gosh. An examiner asking this is totally fair whether you currently treat breast or not - IT'S BREAST!! Every Radonc should know how to treat breast - I'll defend that part of the orals even though I didn't treat a single breast between residency and the boards myself.