Lee Hoon K, D'Souza Warren D, Yamal Jose-Miguel J, Pollack Alan, Lee Andrew K, Palmer Matthew B, Kuban Deborah A
Department of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Int J Radiat Oncol Biol Phys. 2003 Oct 1;57(2):355-61. doi: 10.1016/s0360-3016(03)00583-2.
To assess the accuracy and dosimetric consequences of defining a surrogate urethra at the geometric center of the prostate in postimplant CT scans.
Eighty postimplant CT scans were obtained with a Foley catheter in place at Day 0 and at 1 month for 40 patients who had undergone (125)I prostate brachytherapy. The percentage of urethral volume receiving at least 275% of the prescribed dose (uV(275)), uV(250), uV(200), uV(150), maximal dose received by 90% of urethral volume (uD(90)), uD(70), uD(30), and uD(1) were measured for the Foley catheter and surrogate urethra. The distance between the Foley catheter and surrogate urethra was measured at the base, middle, and apex of the prostate.
A statistically significant difference was found in all the above-listed dosimetric parameters between the Foley catheter and surrogate urethra at Day 0 (p <or= 0.001). At 1 month, the uD(90), uD(70), and uD(1) remained significantly different between the Foley catheter and surrogate urethra (p <or= 0.05). The difference in the uV(275) (p = 0.055) and uV(150) (p = 0.059) between the Foley catheter and surrogate urethra showed a trend toward statistical significance at 1 month. The uV(250), uV(200), and uD(30) were greater for the surrogate urethra than for the Foley catheter at 1 month, but were not significantly different statistically. The mean distance between the Foley catheter and the surrogate urethra was greatest at the base (1.2 cm) in the vertical axis at Day 0 and decreased substantially to 0.87 cm at 1 month (p = 0.0004).
Using a surrogate urethra at the geometric center of the prostate may significantly overestimate the urethral dose at Day 0 and certain dosimetric parameters at 1 month. An alternative position for a surrogate urethra accounting for the difference in the location of the Foley catheter near the base of the prostate at Day 0 and 1 month could be considered in future studies.
评估在植入后CT扫描中，将替代尿道定义在前列腺几何中心处的准确性及剂量学后果。
对40例行（125）I前列腺近距离治疗的患者，在植入后第0天和第1个月时，留置Foley导管，获取80份植入后CT扫描图像。测量Foley导管和替代尿道接受至少275%处方剂量的尿道体积百分比（uV(275)）、uV(250)、uV(200)、uV(150)、90%尿道体积接受的最大剂量（uD(90)）、uD(70)、uD(30)和uD(1)。在前列腺的底部、中部和尖部测量Foley导管与替代尿道之间的距离。
在第0天，Foley导管与替代尿道之间，上述所有剂量学参数均存在统计学显著差异（p≤0.001）。在第1个月时，Foley导管与替代尿道之间的uD(90)、uD(70)和uD(1)仍存在显著差异（p≤0.05）。Foley导管与替代尿道之间的uV(275)（p = 0.055）和uV(150)（p = 0.059）差异在第1个月时有统计学显著差异的趋势。在第1个月时，替代尿道的uV(250)、uV(200)和uD(30)大于Foley导管，但在统计学上无显著差异。在第0天，Foley导管与替代尿道在垂直轴上的底部平均距离最大（1.2 cm），在第1个月时大幅降至0.87 cm（p = 0.0004）。
在前列腺几何中心处使用替代尿道可能在第0天显著高估尿道剂量，并在第1个月高估某些剂量学参数。未来研究可考虑为替代尿道选择一个能考虑到第0天和第1个月时Foley导管在前列腺底部附近位置差异的替代位置。
