Can MRI-only replace MRI-CT planning with a titanium tandem and ovoid applicator?

Area of Science:

• Medical Physics
• Oncology
• Radiotherapy

Background:

• Cervical brachytherapy is a crucial component of treatment for locally advanced cervical cancer.
• Accurate dose delivery relies on precise imaging for target and organ at risk delineation.
• Magnetic Resonance Imaging (MRI) offers superior soft-tissue contrast compared to Computed Tomography (CT).

Purpose of the Study:

• To compare dosimetric outcomes between MRI-only and combined MRI-CT planning for cervical brachytherapy.
• To assess the feasibility of achieving all imaging and planning objectives using MRI alone.
• To evaluate the efficacy of a titanium tandem and ovoid applicator in MRI-only workflows.

Main Methods:

• Ten patients undergoing cervical brachytherapy with a titanium tandem and ovoid applicator were retrospectively analyzed.
• High-risk clinical target volume and organs at risk were contoured on 3D T2 MRI.
• Applicator delineation was performed on MRI by blinded planners, with dose-volume histogram parameters compared to existing MRI-CT plans.

Main Results:

• No significant differences were observed in the D90 or D98 of the high-risk clinical target volume between MRI-only and MRI-CT planning.
• Bladder and sigmoid dose parameters (D0.1cc, D2cc) showed no statistically significant differences between the two planning methods.
• Rectal D0.1cc showed a statistically significant difference (p=0.03), but D2cc was not significantly different, suggesting minimal clinical impact.

Conclusions:

• MRI-only planning for cervical brachytherapy using a titanium applicator is dosimetrically equivalent to MRI-CT planning.
• The study validates the capability of MRI-only workflows to meet imaging and planning goals.
• This approach has been adopted as the clinical standard, potentially streamlining treatment planning.