Dosimetric Comparison of Craniospinal Irradiation Using Different Tomotherapy Techniques

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy

Background:

• Tomotherapy is a crucial radiotherapy technique.
• Evaluating new tomotherapy techniques against conventional methods is essential for optimizing cancer treatment.
• Dosimetric analysis aids in understanding treatment efficacy and safety.

Purpose of the Study:

• To compare new and conventional tomotherapy techniques.
• To evaluate dosimetric differences, including PTV coverage, conformity, homogeneity, and organ-at-risk (OAR) doses.
• To assess the impact of beam on time (BOT), jaw sizes, and pitch values.

Main Methods:

• Dosimetric analysis comparing planning target volume (PTV) median dose, 95% PTV dose coverage, Paddick conformity index (CI), homogeneity index (HI), and OAR median doses.
• Evaluation of beam on time (BOT) and effects of varying jaw sizes and pitch values.
• Comparison of helical tomotherapy (HT)-3DCRT, tomotherapy-IMRT (TD-IMRT), and other tomotherapy techniques.

Main Results:

• PTV dose coverage was comparable across all techniques.
• Dynamic jaw plans reduced OAR doses compared to fixed jaw plans, especially for structures at the treatment field edge.
• HT-3DCRT plans showed higher OAR doses to kidney, liver, and lung; TD-IMRT provided superior liver sparing.
• Whole-body integral dose differences were insignificant.
• Smaller jaw sizes (2.5-cm) improved OAR sparing and HI but increased BOT; increasing pitch improved CI and reduced BOT.

Conclusions:

• Dynamic jaw settings in tomotherapy enhance OAR sparing compared to fixed jaws.
• TD-IMRT demonstrates potential for improved liver dose sparing in tomotherapy.
• Optimizing jaw size and pitch can influence treatment time and plan quality, though OAR sparing benefits from increased pitch were limited.