bastula.org: 4th gear

Alex typically doesn’t do the IMRT QA at Silver Cross. Instead, he only does chart checks and mechanical QA. I went with him this morning and we checked the outputs for all the photon and electron energies. We also did an energy check, which basically is determining whether the beam will produce a reading at a certain depth different than dMax.

We tweaked some of the beams a little bit, because there was a rising trend over the last few weeks (also noted by the therapists). After this, Alex finished checking his charts and I did a couch isocentricity test and verified the isocenter of the machine by using the front pointer and a pen. We both finished the day by resetting the lasers to an appropriate value using a piece of paper and a polystyrene block.

Alex had me working on a plan that had two courses of a treatment: the initial plan and the boost plan. He had already finished preparing the QA for the boost and wanted me to complete it for the initial plan. Basically, this entails going into XiO (our treatment planning software) and starting a new QA plan. To perform the QA, we use a bullet phantom that was designed by Alex. This phantom was scanned a long time ago via CT and imported into XiO. Therefore, we just use that bullet phantom and apply the patient’s plan to the phantom.

We then have to rescale the plan so that only one fraction of the treatment is delivered. This number should also match the total amount of monitor units that are delivered to the patient. Furthermore, the total dose delivered (and for each field) should match the patient’s plan.