Keywords:
Oncology, Cone beam CT, Dosimetry, Cancer
Authors:
N. Mitina, T. Peterson, R. Guidi, C. Hargrave
DOI:
10.26044/ranzcr2023/C-285
Purpose
Stereotactic body radiation therapy (SBRT) is an established, effective treatment for spinal metastases [8]. It utilises advanced imaging technology and delivery techniques to deliver high doses of radiation over a shorter course. SBRT offers patients rapid and durable pain relief while achieving steeper dose gradients near critical structures such as the spinal cord, cauda equina and nerve roots.
Parameters used for plan evaluation in SBRT include Conformity Index (CI) and Gradient Index (GI) [1]. CI is a metric used to evaluate how tightly the prescription dose is conforming to the planning target volume (PTV) whereas GI quantifies the fall-off of dose moving away from the PTV.
Despite the International Commission on Radiation Units and Measurements (ICRU) report 91 recommending that CI and GI be reported for all SBRT courses [1], there is little guidence on what constitutes an acceptable range for those parameters in the setting of treating spine metastases and no specific recommendations are given [7].
The aim of this pilot study is to assess the achieved CI and GI values for patients treated at Radiation Oncology Princess Alexandra Hospital Raymond Terrace (ROPART) and to evaluate these findings with comparison to values in current literature. We hope to identify optimal ranges of CI and GI with regard to location of the disease (Cervical, Thoracic, Lumbar spine) as well as the size (isolated or multiple veretbrae and volume) and complexity of the PTV (LOW, MEDIUM, HIGH).