Graduate Degree Type
Medical Dosimetry (M.S.)
Allied Health Sciences
Whole brain radiation therapy (WBRT) is one of the most effective ways to treat brain metastases. Whole brain radiation therapy is typically planned 3D conformal with a right lateral and left lateral beam arrangement using a 6 mega voltage (MV) beam energy. Lower energy photon beams distribute a greater dose at surface level compared to higher energy photon beams. Using a higher energy photon beam (15 MV) to treat WBRT patients may reduce dose to the scalp and improve the patient’s overall quality of life (QOL).
The study is a retrospective dosimetric analysis of 10 randomly selected whole brain radiation therapy patients. Each patient had four plans created to compare 6 MV vs 15 MV photon energy as well as a scalp-sparing technique vs an open field technique. Dose to critical structures and scalp were fabricated and analyzed by the principle investigator due to a lack of IRB approval. A paired T-Test was performed using IBM-SPSS Statistics software to test for significance between the means of the groups.
The results indicated statistically significant lower dose levels to the scalp on the 15 MV plans and on the scalp sparing plans compared to the 6 MV plans and open field technique plans. Dose coverage to the brain was higher on 15 MV plans and open field technique plans compared to the 6 MV plans and scalp-sparing technique plans. Lens and Optic nerves displayed statistically significant lower doses at 6 MV compared to 15 MV, while Parotids displayed statistically significant lower doses at 15 Mv compared to 6 MV. Lens and Parotids had statistically significant lower doses on scalp-sparing technique plans compared to the open field technique.
Significant dose reduction to the scalp can be accomplished by using a Scalp-sparing technique and/or by using a higher energy photon beam (15 MV), while maintaining adequate coverage to the brain. Critical structure doses were not clinically significant between plans and remained within their allotted tolerances. Future studies should be pursued to examine clinical hair loss and overall quality of loss due to this dose reduction to the scalp.
Riebschleger, Addah, "A Dosimetric Evaluation of Increasing Scalp Sparing Between Varied Energy Photon Beams and MLC Blocking Techniques Among Whole-Brain Irradiation Patients" (2021). Culminating Experience Projects. 51.