Albert Jeffrey M, Swanson David A, Pugh Thomas J, Zhang Michael, Bruno Teresa L, Kudchadker Rajat J, Frank Steven J
Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Brachytherapy. 2013 Jan-Feb;12(1):30-7. doi: 10.1016/j.brachy.2012.03.009. Epub 2012 Jun 21.
Transrectal ultrasound (TRUS) is the standard imaging modality for planning prostate brachytherapy. However, magnetic resonance imaging (MRI) provides greater anatomic detail than TRUS. We compared treatment plans generated using TRUS, endorectal coil MRI (erMRI), and standard body array coil MRI (sMRI).
Treatment plans were used from patients treated with permanent, stranded-seed (125)I brachytherapy in a prospective trial. All men underwent pretreatment planning based on TRUS, and all underwent erMRI before treatment and sMRI 30 days after the implant. Treatments for 20 consecutive patients were replanned on sMRI and erMRI images by investigators blinded to TRUS-based plans. Prostate volume/dimensions, radioactivity-to-prostate-volume ratio, and dosimetric parameters were compared.
Compared with TRUS, mean prostate volume measured by erMRI was smaller, medial-lateral diameter was larger, and anterior-posterior diameter was smaller, suggesting that the endorectal coil produced anatomic distortions. Craniocaudal prostate length was smaller on both types of MRI than on TRUS, suggesting that TRUS overestimates prostate length. Activity per volume was 7.5% lower for plans based on sMRI than on TRUS (0.901 vs. 0.974mCi/cm(3), p<0.001). sMRI plans had similar coverage of the planning target volume (PTV) (dose to 90% of the prostate [D(90)] 116.6% sMRI vs. 117.5% TRUS, p=0.526) and improved dose homogeneity (percentage of PTV receiving 150% of the prescription dose [V(150)] 47.4% sMRI vs. 53.8% TRUS, p=0.001 and percentage of PTV receiving 200% of the prescription dose [V(200)] 16.6% sMRI vs. 19.2% TRUS, p<0.001).
Staging erMRI should not be routinely used for treatment planning because it produces anatomic distortion. sMRI may have treatment planning advantages over TRUS because of superior soft-tissue delineation of the prostate and adjacent normal tissue structures.
经直肠超声（TRUS）是前列腺近距离放射治疗计划制定的标准成像方式。然而，磁共振成像（MRI）能提供比TRUS更详细的解剖结构信息。我们比较了使用TRUS、直肠内线圈MRI（erMRI）和标准体部阵列线圈MRI（sMRI）生成的治疗计划。
在一项前瞻性试验中，采用永久、 stranded - seed（125）I近距离放射治疗的患者的治疗计划被纳入研究。所有男性患者均基于TRUS进行治疗前计划制定，且所有患者在治疗前接受erMRI检查，并在植入后30天接受sMRI检查。由对基于TRUS的计划不知情的研究人员根据sMRI和erMRI图像对连续20例患者的治疗进行重新计划。比较前列腺体积/尺寸、放射性与前列腺体积比以及剂量学参数。
与TRUS相比，erMRI测量的平均前列腺体积较小，左右径较大，前后径较小，提示直肠内线圈产生了解剖结构变形。两种类型的MRI测量的前列腺上下长度均比TRUS测量的小，提示TRUS高估了前列腺长度。基于sMRI的计划每单位体积的活度比基于TRUS的计划低7.5%（0.901对0.974mCi/cm³，p<0.001）。sMRI计划对计划靶区（PTV）的覆盖情况相似（前列腺90%体积所接受的剂量[D(90)]，sMRI为116.6%，TRUS为117.5%，p = 0.526），且剂量均匀性有所改善（PTV接受150%处方剂量的百分比[V(150)]，sMRI为47.4%，TRUS为53.8%，p = 0.001；PTV接受200%处方剂量的百分比[V(200)]，sMRI为16.6%，TRUS为19.2%，p<0.001）。
分期erMRI不应常规用于治疗计划制定，因为它会产生解剖结构变形。由于sMRI对前列腺及相邻正常组织结构的软组织勾勒更优，其在治疗计划制定方面可能比TRUS更具优势。
