Pulse sequence considerations for simulation and postimplant dosimetry of prostate brachytherapy

Area of Science:

• Medical Imaging
• Radiotherapy Physics
• Oncology

Background:

• Prostate brachytherapy requires precise imaging for accurate seed placement and dosimetry.
• Magnetic Resonance Imaging (MRI) offers detailed anatomical visualization but requires optimized protocols for this application.

Purpose of the Study:

• To review MRI physics principles relevant to prostate brachytherapy.
• To summarize optimized MRI protocols for prostate brachytherapy.

Main Methods:

• Reviewed key MR imaging characteristics: spatial resolution, SNR, contrast, artifacts, geometric distortion, SAR, and scan time.
• Optimized three-dimensional (3D) pulse sequences: fast-spoiled gradient echo (T1-weighted), fast-spin echo (T2-weighted), and fast imaging in steady-state precession (combined T1/T2-weighted).
• Described the use of an endorectal coil for enhanced imaging.

Main Results:

• Acquired high-quality prostate images within 3-5 minutes per sequence.
• Achieved spatial resolution of 0.59 mm × 0.73 mm × 1.2 mm or better.
• Demonstrated simultaneous imaging of seed markers and anatomy with the steady-state precession sequence, while other sequences imaged them separately.

Conclusions:

• Optimized MRI protocols adequately image prostate anatomy and radioactive seed markers for post-implant dosimetry.
• Imaging can be performed separately or simultaneously using different pulse sequences.
• Total scan time for each optimized sequence is within 3-5 minutes.