Dosimetry of Continuous Random Motion in High Dose Rate Strontium-90 Plesiotherapy.

Area of Science:

• Radiation Oncology
• Medical Physics
• Dermatology

Background:

• Strontium-90 (Sr-90) plesiotherapy offers precise, high-dose radiation for superficial lesions.
• Current methods using static, overlapping fields can lead to uneven dose distribution and normal tissue overdose.
• High-activity Sr-90 sources necessitate accurate dosimetry due to rapid dose fall-off.

Purpose of the Study:

• To prospectively evaluate and compare the dosimetry of static versus continuous motion techniques in Sr-90 plesiotherapy.
• To assess the impact of applicator motion on dose homogeneity and accuracy for various target field shapes.
• To identify methods for minimizing over- and underdosed areas during Sr-90 treatments.

Main Methods:

• Radiochromic film was used to measure radiation doses for static and continuous motion applicator techniques.
• Three target field shapes were investigated: single circle, curvilinear, and cloverleaf.
• Treatments were performed by multiple operators for both qualitative (1 Gy) and quantitative (5 Gy) dose evaluations.

Main Results:

• Continuous motion application resulted in significantly more homogenous radiation doses compared to static fields (p ≤ 0.01).
• Differences in dose distribution were observed between operators and were dependent on the number of overlapping fields.
• Continuous motion demonstrated superior dose fall-off control at the treated field margins.

Conclusions:

• The continuous motion technique offers improved dose homogeneity and accuracy in Sr-90 plesiotherapy.
• This method is particularly beneficial when the applicator must be held statically during treatment.
• Continuous motion application of Sr-90 plesiotherapy can enhance treatment efficacy and reduce side effects.