Interfacility variation in treatment planning parameters in tomotherapy: field width, pitch, and modulation factor

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Tomotherapy planning parameters like field width (FW), pitch, and modulation factor (MF) influence dose distribution and delivery time.
• Variations in these parameters across different treatment facilities are not well-documented.

Purpose of the Study:

• To determine standard values for FW, pitch, and MF in head and neck cancer (HNC) and prostate cancer (PC) treatment planning using tomotherapy in Japan.
• To identify current practices and variations in parameter selection among Japanese radiation therapy facilities.

Main Methods:

• A web-based questionnaire was distributed to 48 Japanese facilities utilizing tomotherapy.
• Data on commonly used planning parameters (FW, pitch, MF) for HNC and PC were collected from 23 responding facilities (48% response rate).

Main Results:

• Field width (FW) was predominantly 2.5 cm; dynamic FW was used with tomoEDGE licenses.
• Pitch adjustments were more frequent for HNC than PC, influenced by FW, dose per fraction, or target offset.
• Median preset modulation factors (MF) were 2.4 for HNC and 2.0 for PC, with significant inter-facility variation observed.

Conclusions:

• Significant variations exist in tomotherapy planning parameters, particularly pitch and MF, between Japanese facilities for HNC and PC.
• These findings provide valuable insights for facilities aiming to optimize tomotherapy treatment planning and potentially establish standardized protocols.