Author: Sunil Mani, Ilakiya Raghavendiran, Vasanthan Sakthivel, Skanda Kabilan Swamy 👨🔬
Affiliation: Edmond Santa Fe High School, Edmnd Deer Creek High, Cancer Specialists of North Florida, Advanced Medical Physics 🌍
Purpose: Purpose/Objective(s): To evaluate and validate the dose calculation and delivery accuracy for patients planned using diagnostic CT
Methods: A total of forty-two patients with palliative spine were treated across four clinics using 20Gy in five fractions. Treatment plans were done on diagnostic CT (dCT) scan using Monaco treatment planning system. Patients were selected so that the acquisition date should not be more than ten days from the treatment date. Twenty-eight patients were treated with AP/PA field arrangement and fourteen patients had three field arrangement with AP and two posterior obliques. Conebeam CTs were acquired for all patients prior to their treatment for setup verification. Furthermore, simulation CT (sCT) images were taken after the first fraction for dose comparison. The CBCTs taken during the first fraction were enhanced using MIM ARTassist software to correct for missing FOV and improve HU values. Verification plans were created in Monaco on both the enhanced CT (eCT) and sCT to enable dose comparison.
Results: The study reveals that the PTV coverage variance between the dCT-based plan and sCT was less than 1.5% with a standard deviation of 0.6. While dCT-based plans exhibited marginally lower coverage than their sCT-based plan, no significant differences were observed (P=0.2). eCT-based plans overestimated the dose by an average of 2.3% attributed to the inconsistencies in enhancing the HU values, particularly for soft tissue. The maximum difference noted in eCT was 4.3% for three field technique on a patient where the FOV and HU correction were deemed unacceptable
Conclusion: dCT based planning have improved the efficiency of spine palliative treatment from an average of 3.2 days to 1.2 days. The dose difference between sCT and dCT-based plans are clinically acceptable. However, caution should be exercised in patient selection criteria, particularly in cases involving metal implants and physical or anatomical changes