Parallel imaging compressed sensing for accelerated imaging and improved signal-to-noise ratio in MRI-based postimplant dosimetry of prostate brachytherapy

To investigate the feasibility of using parallel imaging compressed sensing (PICS) to reduce scan time and improve signal-to-noise ratio (SNR) in MRI-based postimplant dosimetry of prostate brachytherapy.

Ten patients underwent low-dose-rate prostate brachytherapy with radioactive seeds stranded with positive magnetic resonance-signal seed markers and were scanned on a Siemens 1.5T Aera. MRI comprised a fully balanced steady-state free precession sequence with two 18-channel external pelvic array coils with and without a rigid two-channel endorectal coil. The fully sampled data sets were retrospectively subsampled with increasing acceleration factors and reconstructed with parallel imaging and compressed sensing algorithms. The images were assessed in a blinded reader study by board-certified care providers. Rating scores were compared for statistically significant differences between reconstruction types.

Images reconstructed from subsampling up to an acceleration factor of 4 with PICS demonstrated consistently sufficient quality for dosimetry with no apparent loss of SNR, anatomy depiction, or seed/marker conspicuity when compared to the fully sampled images. Images obtained with acceleration factors of 5 or 6 revealed reduced spatial resolution and seed marker contrast. Nevertheless, the reader study revealed that images obtained with an acceleration factor of up to 5 and reconstructed with PICS were adequate-to-good for postimplant dosimetry.

Combined parallel imaging and compressed sensing can substantially reduce scan time in fully balanced steady-state free precession imaging of the prostate while maintaining adequate-to-good image quality for postimplant dosimetry. The saved scan time can be used for multiple signal averages and improved SNR, potentially obviating the need for an endorectal coil in MRI-based postimplant dosimetry.

Brachytherapy. 2018 Jun 04 [Epub ahead of print]

Jeremiah W Sanders, Hao Song, Steven J Frank, Tharakeswara Bathala, Aradhana M Venkatesan, Mitchell Anscher, Chad Tang, Teresa L Bruno, Wei Wei, Jingfei Ma

Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX. Electronic address: ., Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX., Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX., Department of Diagnostic Radiology, The University of Texas MD Anderson Cancer Center, Houston, TX., Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX.

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