Physical predictors of adequate hyperthermia with the annular phased array

Area of Science:

• Oncology
• Medical Physics
• Biomedical Engineering

Background:

• Hyperthermia therapy, particularly using annular phased array systems, is an adjunct cancer treatment.
• Optimizing the physical parameters of hyperthermia delivery is crucial for therapeutic efficacy.

Purpose of the Study:

• To identify physical predictors of hyperthermia quality in patients treated with the BSD 1000 annular phased array system (APAS).
• To establish criteria for adequate hyperthermia based on temperature, time, and power delivery.

Main Methods:

• Review of 152 hyperthermia sessions in 36 patients treated with the BSD 1000 APAS.
• Analysis of physical parameters including time to reach target temperature, temperature rise rate, and net forward power.
• Definition of adequate hyperthermia as central tumor temperature ≥ 42°C for at least 30 minutes.

Main Results:

• Central tumor temperatures > 42°C were achieved momentarily in 62% of sessions, but prolonged maintenance was challenging.
• Shorter time to reach target temperature (< 25 min) was strongly associated with adequate hyperthermia (28/69 adequate sessions).
• An initial temperature rise rate > 0.4°C/min with net forward power < 1500 W within the first 3 minutes predicted adequate hyperthermia (only 3/57 sessions not meeting criteria were adequate).

Conclusions:

• Rapid attainment of target temperatures and specific early physical parameters are key predictors of successful hyperthermia quality.
• Treatment protocols should aim for faster temperature escalation and monitor initial power and temperature rise rates.
• Further research should refine these physical predictors for improved hyperthermia treatment planning and delivery.