前列腺癌^131Cs和^125I及^103Pd粒子植入剂量学研究

Dosimetric study of permanent prostate brachytherapy utilizing ^131Cs,^125I and ^103Pd seeds

目的比较^1231Cs、^125I和^103pd粒子组织间永久性植入治疗前列腺癌剂量学特性。方法随机选择25例曾接受^125I粒子永久性植入早期（T1-T2c期）前列腺癌患者，使用Prowess Braehytherpay 3.1粒子植入治疗计划系统重新设计3种粒子植入计划。经直肠超声采集横断面图像上勾画前列腺、尿道前列腺段和直肠前壁，不再在前列腺基础上外放边界勾画PTV。^131Cs、^125I、^103Pd计划处方剂量分别为115、145、125Gy，粒子活度分别为1.8、0.5、1.8U。计划目标为前列腺V100=95％、D90≥100％，尿道前列腺段UD10≤150％。比较不同计划前列腺、尿道和直肠剂量分布，以及植入粒子数和植入针数。各参数间差异的统计学检验使用单因素方差分析。结果^103Pd、^125I和^131Cs计划的前列腺V_200分别为28．7％、20．9％和19．6％（F=42．50，P=0.000），V_150分别为51．9％、42．1％和39．4％（F=26．15，P=0．000），V100分别为95．4％、95．3％和95．5％（F=2．01，P=0．142），D90分别为108．9％、107．8％和108．0％（F=1．41，P=0．252）。平均UV_120分别为26．9％、29．5％和23．8％（F=0．37，P=0．691），平均直肠RV_100分别为0．31、0．22和0．19cm^3（F=0．43，P=0．652）。每cm^3前列腺体积平均植入粒子数分别为2．02、2．01和1．87（F=1．92，P=0．154）、平均粒子植入针数分别为33．6、32．9和31．6（F=0．26，P=0．772）。结论”。Cs粒子永久性植入治疗前列腺癌靶区剂量最均匀，而对直肠和尿道剂量、植入粒子数和植入针数有降低的可能。

Objective To compare the dosimetric differences of permanent prostate brachytherapy utilizing ^131Cs,^125I and ^103Pd seeds. Methods Twenty-five patients with T1-T2c prostate cancer who had previously implanted with ^125I seeds were randomly selected in our study. The patients were re-planned with in Cs, ^125I and ^103Pd seeds by using the Prowess Brachytherpay 3.1 planning system to the prescription doses of 115 Gy, 145 Gy and 125 Gy, respectively. The seed strengths were 1.8 U,0.5 U and 1.8 U, respectively. The prostate, prostatic urethra and anterior wall of the rectum were contoured on traMs-rectal ultrasound images. PTV was outlined based on the prostate volume with no margin applied. The attempted planning goals were that V_100 （the percentage volume of the prostate receiving at least 100% of the prescription doses）=95% ,D_90 （the minimum percentage dose covering 90% of the prostate volume）≥100% ,and prostatic urethra UD10 （the maximum percentage dose receiving by 10% of the contoured urethra） ≤150%. For the plan comparison, we also computed prostate V_150, prostatic urethra UV~_120, rectum RV_100, and the number of implanted seeds and needles. The significance of the differences was tested using one way analysis of variance. Results The average V_200 in the ^103Pd,^125I and ^131Cs plans were 28.7% ,20.9% and 19.6% （F =42.50, P =0.000） ;the average V_150 were 51.9% ,42.1% and 39.4% （F=26.15,P=0.000） ;the average UV_120 were 26.9% ,29.5% and 23.8% （ F = 0.37, P = 0.691 ） ; and the average rectum RV_100 were 0.31 cm^3, 0.22 cm^3 and 0.19 cm^3（F = 0.43,P = 0. 652）. For ^103Pd, ^125I and ^131Cs, the average number of implanted seeds per cm^3 prostate were 2.02,2.01 and 1.87 （ F = 1.92, P = 0. 154）, and the average number of needles were 33.6,32.9 and 31.6（F =0.26,P =0. 772）. Conclusions Comparing to ^125I and ^103Pd seeds used in permanent prostate brachytherapy, ^131Cs seeds has better dose homogeneity, and possible better sparing of the urethra and rectum, with comparable or less implanted seeds and needles.