Sanders Jeremiah W, Song Hao, Frank Steven J, Bathala Tharakeswara, Venkatesan Aradhana M, Anscher Mitchell, Tang Chad, Bruno Teresa L, Wei Wei, Ma Jingfei
Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX.
Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX.
Brachytherapy. 2018 Sep-Oct;17(5):816-824. doi: 10.1016/j.brachy.2018.05.003. Epub 2018 Jun 4.
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.
探讨在基于磁共振成像（MRI）的前列腺近距离治疗植入后剂量测定中，使用并行成像压缩感知（PICS）来缩短扫描时间并提高信噪比（SNR）的可行性。
10例患者接受了低剂量率前列腺近距离治疗，植入的放射性粒子带有阳性磁共振信号粒子标记物，并在西门子1.5T Aera上进行扫描。MRI采用完全平衡稳态自由进动序列，使用两个18通道的外部盆腔阵列线圈，有或没有刚性的两通道直肠内线圈。对完全采样的数据集进行回顾性欠采样，加速因子逐渐增加，并使用并行成像和压缩感知算法进行重建。在一项盲法阅片研究中，由获得委员会认证的医疗人员对图像进行评估。比较不同重建类型的评分，以确定是否存在统计学上的显著差异。
与完全采样图像相比，使用PICS对加速因子高达4的欠采样数据进行重建得到的图像，在剂量测定方面始终具有足够的质量，在信噪比、解剖结构描绘或粒子/标记物清晰度方面均无明显损失。加速因子为5或6时获得的图像显示空间分辨率和粒子标记物对比度降低。然而，阅片研究表明，加速因子高达5并使用PICS重建的图像对于植入后剂量测定来说质量尚可。
并行成像与压缩感知相结合，可在前列腺完全平衡稳态自由进动成像中大幅缩短扫描时间，同时保持植入后剂量测定所需的足够好的图像质量。节省的扫描时间可用于多次信号平均并提高信噪比，这可能使基于MRI的植入后剂量测定不再需要直肠内线圈。
