Date Approved

5-6-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Allied Health Sciences

First Advisor

Alyssa Capizzi, M.S., CMD

Academic Year

2024/2025

Abstract

Abstract

Objective

Hippocampal avoidance whole brain radiation therapy (HA-WBRT) has been demonstrated to improve neurocognitive outcomes compared to conventional WBRT in patients with brain metastases. The purpose of this study is to evaluate the impact of a neutral (0 degree) and hyper-flexion (30 degree) neck position on radiation planning objectives for HA-WBRT, to further reduce radiation doses to the hippocampi and other organs-at risk (OARs).

Methods

Nine eligible patients were those who previously underwent diagnostic computed tomography (CT) imaging of the head in a neutral head position and then received VMAT HA-WBRT with hyper-flexed neck position per institutional protocol. Comparative HA-WBRT plans were generated using their diagnostic CT scans, in a neutral head position.

Results

Constants of the research included: brain volume (cc), planned treatment volume (PTV) 95% (cGy), and clinical treatment volume (CTV) 90%, were proven to be statistically insignificant. Plan objectives evaluated revealing significance were: hotspot, total monitor unit (MU), MU ratio, and treatment beam on time. Significance of difference was not proven for PTV conformity index (CI) and PTV gradient index (GI). OAR doses were evaluated, showing significant difference of dose to the hippocampi D100, optic nerve L D0.035cc, and the R optic nerve D0.035 cc.

Conclusion

Hippocampal avoidance while treating the whole brain in cases of brain metastasis is crucial to spare cognitive function for patients, therefore improving quality of life. This research shows that there is a clinically improved technique in planning HA-WBRT, when the patient’s neck is hyper-flexed in a 30° position.

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Available for download on Wednesday, May 06, 2026

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