Download AP/PA Beams - Dana Minor

AP/PA Beams
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This plan followed the prescription of 3 Gy/fx to the 94% isodose line for 10 fx
The point dose at isocenter from all prescriptions is 31.9 Gy
The tumor volume is completely encompassed within the 94% isodose lines
There are minimal hot spots (104%) of the dose, the hot sports are small and are located
mostly in muscle in the anterior and posterior aspects of the chest
The max dose is 35.3 Gy and is located within the tumor volume
Looking at the DVH, 30% of the lungs are getting .03% of the normalized dose (1.19 Gy)
30% of the cord is receiving 78% of the normalized dose (30.6 Gy)
The gross tumor volume (GTV) is receiving 78-89% of the normalized dose
AP/PA Chest with Wedges
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This treatment was planned to the same prescription as the previous plan
The difference of this plan is the addition of wedges
The AP field uses a 45 degree wedge with the heal later to the patient
The PA field uses a 15 degree wedge with the heal later
Looking at the isodose curves
o Because the wedge heals are both lateral, the dose distribution moves medially
o This results in the tumor not being encompassed in the 94% isodose line
o There are also very large hot spots throughout the entire treatment area
o These hot spots are right over the cord, heart, and cardiac vessels
The MUs for this plan are increased because of the wedge factors (AP – 313 Mu, PA –
226 Mu where in the previous plan AP – 166 Mu and PA – 172 Mu)
A must higher dose must be delivered in order for the point of interest to get the
necessary dose
The max dose was 39.8 Gy (which was much higher than the previous plan) and the dose
to the isocenter was 31.9 Gy
When looking at the DVH curves
o The GTV is much lower because the tumor is not in the 94% isodose curve
o The cord is getting a much higher dose die to the hot spots through the tx area
AP/PA chest with weighted fields
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This plan used an AP beam weighted at 25.4% and a PA beam weighted at 74.6%
The AP beam delivered 84 Mu while the PA beam delivered 257 Mu
The anterior portion of the GTV isnot included in the 94% isodose line
Also, the hot sport is much larger in the posterior aspect of the chest
The max dose is 39.8 Gy which is much higher than the original plan
The idsodose curves are more posterior because the PA beam is heavily weighted – this
results in an under dose to the anterior portion of the tumor and an over dose to the
normal tissue that is posterior to the GTV
When looking at the DVH curves
o The GTV curve is angles so much because some of the tumor volume is getting
104% of the dose, where some of it is getting onlu 90%
o The cord is getting a much higher dose than the original plan