A new miniature x-ray device for interstitial radiosurgery: dosimetry

Area of Science:

• Medical Physics
• Oncology
• Medical Devices

Background:

• Minimally invasive cancer treatments are crucial for reducing patient morbidity.
• Stereotactic interstitial brachytherapy offers precise radiation delivery.
• Existing interstitial devices may have limitations in portability and power.

Purpose of the Study:

• To develop and characterize a miniature, battery-operated x-ray device for interstitial tumor treatment.
• To evaluate the dosimetric properties of the x-ray beam emitted from the device.
• To assess the feasibility and safety of the device in a Phase I clinical trial.

Main Methods:

• A 40 kV, battery-operated x-ray probe (10 cm long, 3 mm diameter) was designed for stereotactic insertion.
• X-ray beam characteristics were analyzed using half-value layer (HVL), spectrum analysis, and isodose contours.
• Absolute output was measured with a modified parallel plate ionization chamber to determine dose rate in water.

Main Results:

• The x-ray beam behaved as a point isotropic source with an effective energy of 20 keV at 10 mm depth in water.
• The dose rate in water was measured at approximately 150 cGy/min at 10 mm distance (40 kV, 40 µA).
• Dose in water decreased with distance, approximately as the third power.

Conclusions:

• The developed miniature x-ray device is a viable option for interstitial treatment of small tumors.
• The device demonstrates predictable dosimetry and a favorable dose fall-off characteristic.
• Phase I clinical trial results in 14 patients indicate the potential of this technology in clinical practice.