Quality control of the SIGMA applicator using a lamp phantom: a four-centre comparison

Area of Science:

• Medical Physics
• Biomedical Engineering
• Therapeutic Technologies

Background:

• Regional hyperthermia treatment utilizes microwave applicators to deliver localized heat therapy.
• Quality control of these systems is crucial for effective and safe treatment delivery.
• Existing quality control methods may not adequately address power distribution and focusing accuracy.

Purpose of the Study:

• To develop and utilize a novel phantom for assessing power distribution in ring applicators for regional hyperthermia.
• To evaluate the performance and identify potential errors in BSD-2000 type therapy systems using the SIGMA-60 applicator.
• To investigate the causes of power distribution imbalances and their impact on treatment efficacy.

Main Methods:

• Development of an elliptical phantom with a fat-equivalent ring and lamp matrix for power distribution visualization.
• Testing of four European BSD-2000 therapy systems under routine conditions.
• Detailed analysis of system setups, frequency-dependent focusing imbalances, and potential error sources.

Main Results:

• Frequency-dependent focusing imbalances were detected in all tested SIGMA-60 applicators.
• Two of the four systems exhibited considerable errors in their settings during quality control tests.
• Identified causes of maladjustments include antenna coupling, coaxial cable interactions, phase errors, and cable/plug defects.

Conclusions:

• The study confirms the necessity of a practical and universal quality control procedure for regional hyperthermia.
• Defects in equipment, particularly phase errors and cable issues, can lead to significant, unnoticed restrictions in controlling specific absorption rate (SAR) distribution.
• Implementing robust quality control measures is essential for ensuring the reliability and accuracy of hyperthermia treatments.