Helical tomotherapy for single and multiple liver tumours.

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Intensity-modulated radiotherapy (IMRT) is a standard treatment for liver tumours.
• Helical tomotherapy (HT) and step-and-shoot IMRT (SaS-IMRT) are two IMRT techniques.
• Comparative dosimetric analysis is crucial for optimizing treatment plans.

Purpose of the Study:

• To quantitatively evaluate the dosimetric performance of HT compared to SaS-IMRT for single and multiple liver tumours.
• To assess the impact of HT on target coverage, dose homogeneity, and organ-at-risk sparing.
• To analyze treatment efficiency metrics including delivery time and monitor units.

Main Methods:

• Retrospective analysis of 16 patients with liver tumours previously treated with SaS-IMRT.
• Re-planning of patient cases using HT.
• Dosimetric indices evaluated: conformity index (CI), homogeneity index (HI), PTV prescription, NTCP, V(30 Gy), V(50%), QI, MU/fr, and delivery time.

Main Results:

• For single liver tumours, no significant dosimetric difference was observed between HT and SaS-IMRT. SaS-IMRT showed shorter delivery time and lower MU/fr.
• For multiple liver tumours, HT demonstrated significant improvements in CI (14%) and HI (4%) compared to SaS-IMRT.
• HT resulted in lower V(50%), V(30 Gy), and QI values, indicating superior OAR sparing and reduced normal liver NTCP (2.38% vs 20.27%). HT also had a shorter delivery time.

Conclusions:

• HT offers significant dosimetric advantages over SaS-IMRT for multiple liver tumours, particularly in sparing organs at risk.
• For single liver tumours, SaS-IMRT is more efficient in terms of MU/fr and delivery time, with no significant dosimetric compromise.
• HT is a promising technique for improving treatment outcomes in complex liver tumour cases.