125I粒子治疗儿少期头颈部交界瘤的靶区与剂量设计

目的总结并评价儿少期头颈部交界性肿瘤125I放射性粒子植入方案的靶区与剂量设计。方法选择2010年1月至2018年12月间于北京大学口腔医院就诊经单纯125I放射性粒子组织间植入近距离治疗或联合手术治疗的儿少期交界性肿瘤患者11例, 以大体肿瘤靶区外扩0.5～1.0 cm为计划靶区, 处方剂量80～120 Gy, 活度为18.5 MBq, 全麻下按治疗计划将125I放射性粒子植入靶区。术后进行随访, 记录疗效及不良反应。评析粒子植入前、后剂量学参数以及局部控制率、客观缓解率和不良反应发生率。结果 11例儿少期患者粒子植入前、后剂量学参数差异无统计学意义(P>0.05)。随访33～131个月, 中位时间48个月。局部控制率100%, 完全缓解率71.4%, 客观缓解率100%, 急性不良反应率81.8%。结论 125I放射性粒子植入治疗儿少期头颈部交界瘤, 在合理的靶区及剂量设计下, 可获得满意的临床疗效且不良反应较低, 是一种可行的治疗手段。     

3D打印模板辅助CT引导放射性125I粒子植入治疗软组织肉瘤的剂量学研究

目的 通过对3D打印模板（共面和非共面）辅助治疗软组织肉瘤术前、术后的剂量学比较,探讨其应用的精确性。方法 2015年12月—2017年7月于北京大学第三医院接受3D打印模板辅助CT引导放射性¹²⁵I粒子植入的软组织肉瘤患者19例,共25处病灶。所有患者行术前病情评估、CT模拟定位、术前计划设计、3D模板打印、3D模板复位、插植粒子针和粒子植入、术后剂量学评估、术后护理及定期随访。对比术前、术后剂量学参数。筛选位于躯干及四肢浅部的软组织肉瘤10例,分别设计共面模板和非共面模板引导的术前计划,对比两种模板引导下术前计划的剂量学参数。结果 设计制作3D打印模板25块,共25处病灶,术前、术后剂量学参数差异无统计学意义（P>0.05）。位于躯干及四肢浅表并使用3D打印共面模板与非共面模板引导的术前计划各剂量学参数差异无统计学意义（P>0.05）。结论 应用3D打印模板辅助¹²⁵I粒子植入治疗软组织肉瘤具有较好的定位精确性。对位于躯干及四肢浅部的软组织肉瘤,建议优先选择3D打印共面模板。     

3D打印共面坐标模板辅助125I放射性粒子植入治疗盆壁复发宫颈癌的剂量学研究

目的 探讨放疗后盆壁复发宫颈癌患者采用3D打印共面坐标模板（3D-PCT）辅助¹²⁵I放射性粒子植入治疗剂量精确性实施的可行性。方法 本研究为单中心的回顾性研究,选取2016年4月至2017年12月北京大学第三医院应用3D-PCT辅助¹²⁵I放射性粒子植入治疗的放疗后盆壁复发宫颈癌患者资料10例。患者年龄37~71岁,中位年龄53.5岁,KPS评分≥ 70分。所有患者均接受过盆腔放疗。病灶体积为3.5~58.0 cm³（中位31.9 cm³）,处方剂量120~180 Gy,粒子活度0.55~0.67 mCi（1 Ci=3.7×10¹⁰Bq）,术前计划植入粒子数目为50（12~81）颗。根据术前计划在3D-PCT引导下行放射性粒子植入术。术后实际植入粒子数目为53（10~82）颗。评估剂量学参数包括D₉₀、D₁₀₀、V₁₀₀、V₁₅₀、V₂₀₀、靶区外体积指数（EI）、适形指数（CI）和均匀性指数（HI）,以及危及器官剂量D_{2 cm³}、D_{1 cm³}和D_{0.1 cm³}。术前计划与术后计划参数的比较采用相关样本非参数检验。结果 术后实际植入粒子数目多于术前计划设计,差异有统计学意义（Z=-2.255,P<0.05）。术后计划与术前计划的靶区剂量学参数D₉₀、D₁₀₀、V₁₀₀、V₁₅₀、V₂₀₀、EI、CI和HI比较,差异均无统计学意义（P>0.05）。膀胱、肠道的D_{2 cm³}、D_{1 cm³}和D_{0.1 cm³}、直肠D_{0.1 cm³}的术后计划与术前计划剂量差异均无统计学意义（P>0.05）。直肠D_{2 cm³}和D_{1 cm³}术后计划剂量低于术前计划,差异均有统计学意义（Z=-2.100、-2.240,P<0.05）。结论 3D-PCT辅助¹²⁵I放射性粒子植入治疗盆壁复发宫颈癌,通过术中剂量优化,术后实际剂量达到术前计划设计,可以保证¹²⁵I放射性粒子植入盆壁复发宫颈癌的剂量精确实施。     

数字化外科技术在125I粒子植入治疗头颈深部肿瘤中的应用

目的探索和评价数字化外科技术用于引导¹²⁵I粒子植入治疗头颈深部肿瘤的精确性、适形性和临床应用价值。方法回顾性选取12例行¹²⁵I放射性粒子近距离放疗的头颈深部肿瘤患者。治疗前基于CT图像设计插植针和粒子位置。根据治疗计划构建数字化定位模型将计划的插植针位置精准导入至手术导航系统,并根据患者面部外形轮廓和插植针位置方向设计打印个体化穿刺引导模板。术中在导航引导下进行模板核准就位,在导航系统的可视化针道、实时插植针位置和模板导向孔共同引导下进行插植针穿刺和放射性粒子植入。CT检查验证插植针与粒子的位置,并计算实际靶区剂量分布,观察术中及术后是否出现血肿、疼痛、感染、穿刺点不愈合、肿瘤细胞种植等不良反应。结果12例患者均在数字化外科技术引导下完成插植针穿刺和放射性粒子植入,实时可视化引导效果佳,插植针、粒子与治疗计划中的位置、数目相符,空间分布均匀。术后剂量验证D90范围为83.7~131.0 Gy,平均107.5 Gy;V100范围为89.6%~99.3%,平均94.6%;V150范围为40.2%~58.9%,平均47.8%。术中术后未出现严重不良反应。结论采用数字化外科技术,将手术导航系统与3D打印个体化穿刺引导模板结合共同引导插植针穿刺和¹²⁵I粒子植入,提高了近距离放疗的精确性和适形性,在头颈部近距离放疗特别是深部解剖结构复杂区具有临床应用价值。     

Experimental determination of the Task Group-43 dosimetric parameters of the new I25.S17plus 125I brachytherapy source

PurposeTo present experimental dosimetry results for the new IsoSeed I25.S17plus ¹²⁵I brachytherapy source, in fulfillment of the American Association of Physicists in Medicine recommendation for, at least one, experimental dosimetry characterization of new low-energy seeds before their clinical implementation.Methods and MaterialsA batch of 100 LiF thermoluminescent dosimeter (TLD)-100 microcubes was used for the experimental determination of the dose-rate constant, radial dose, and anisotropy functions, in irradiations performed using two Solid Water phantoms. Monte Carlo (MC) simulations were used to determine appropriate correction factors that account for the use of Solid Water as a phantom material instead of liquid water and for the different energy response of the TLD dosimeters in the experimental ¹²⁵I photon energies relative to the 6 MV x-ray photon beam used for the TLD calibration. Measurements were performed for four I25.S17plus seeds; one with direct traceability of air-kerma strength calibration to National Institute of Standards and Technology and three with secondary National Institute of Standards and Technology traceability.ResultsA mean dose-rate constant, Λ, of 0.956 ± 0.043 cGy h⁻¹ U⁻¹ was experimentally determined for the I25.S17plus source, which agrees within uncertainties with the MC result of 0.925 ± 0.013 cGy h⁻¹ U⁻¹ calculated independently for the same seed model in a previous study. Agreement was also observed between the measured and the MC-calculated radial dose and anisotropy function values.ConclusionsExperimental dosimetry results for the I25.S17plus ¹²⁵I source verify corresponding independent MC results in the form of Task Group-43 dosimetry parameters. The latter are found in agreement within uncertainties with sources of similar design incorporating a silver marker, such as the Oncura OncoSeed Model 6711.     

MRI-assisted radiosurgery: A quality assurance nomogram for palladium-103 and iodine-125 prostate brachytherapy

PurposeWe sought to develop an activity nomogram for magnetic resonance (MR)–planned permanent seed prostate brachytherapy to improve quality assurance through a secondary dosimetric check.Methods and MaterialsPatients undergoing MRI-assisted radiosurgery (MARS), whereby MRI is used for preoperative planning and postimplant dosimetry, were reviewed from May 2016 to September 2018. Planned activity (U) was fitted by MR-prostate volume (cc) via simple linear regression. Resulting monotherapy nomograms were compared with institutional nomograms from an ultrasound-planned cohort. Dosimetric coverage and external urinary sphincter (EUS) dose were also assessed for MR-planned patients.ResultsWe identified 183 patients treated with MARS: 146 patients received palladium-103 (¹⁰³Pd; 102 monotherapy and 44 boost), and 37 received iodine-125 (¹²⁵I) monotherapy. Median prostate volume was 28 cc (interquartile range: 22–35). Lines of best fit for implant activity were U = 4.344 × (vol) + 54.13 (R²: 95%) for ¹⁰³Pd monotherapy, U = 3.202 (vol) + 39.72 (R²: 96%) for ¹⁰³Pd boost and U = 0.684 (vol) + 13.38 (R²: 96%) for ¹²⁵I monotherapy. Compared with ultrasound, MR-planned nomograms had lower activity per volume (p < 0.05) for both ¹⁰³Pd monotherapy (∼6%) and ¹²⁵I monotherapy (∼11%), given a median size (30 cc) prostate. Across all MARS implants, postimplant dosimetry revealed a median V100% of 94% (interquartile range: 92–96%). Median EUS V125 was <1 cc for all patients, regardless of isotope.ConclusionsWe developed a quality assurance nomogram for MR-planned prostate brachytherapy. When compared with ultrasound-planned, MR-planned monotherapy resulted in a lower activity-to-volume ratio while maintaining dosimetric coverage, likely secondary to EUS-sparing and reduced planning target margins.     

导航辅助CT引导放射性粒子治疗盆腔复发恶性肿瘤剂量学研究

目的 通过比较导航辅助CT引导放射性粒子治疗盆腔复发恶性肿瘤的术前、术后计划剂量学参数探讨该技术治疗的精确性.方法 回顾性纳入2018年12月至2020年2月于北京大学第三医院接受导航联合3D打印个体化模板(3D-PIT)辅助CT引导放射性1251粒子植入治疗的盆腔复发恶性肿瘤患者共15例,其中宫颈癌7例,直肠癌7例,...     

Dosimetric influence of seed spacers and end-weld thickness for permanent prostate brachytherapy

PurposeThe aim of this study was to analyze the dosimetric influence of conventional spacers and a cobalt chloride complex contrast (C4) agent, a novel marker for MRI that can also serve as a seed spacer, adjacent to ¹⁰³Pd, ¹²⁵I, and ¹³¹Cs sources for permanent prostate brachytherapy.Methods and MaterialsMonte Carlo methods for radiation transport were used to estimate the dosimetric influence of brachytherapy end-weld thicknesses and spacers near the three sources. Single-source assessments and volumetric conditions simulating prior patient treatments were computed. Volume–dose distributions were imported to a treatment planning system for dose–volume histogram analyses.ResultsSingle-source assessment revealed that brachytherapy spacers primarily attenuated the dose distribution along the source long axis. The magnitude of the attenuation at 1 cm on the long axis ranged from −10% to −5% for conventional spacers and approximately −2% for C4 spacers, with the largest attenuation for ¹⁰³Pd. Spacer perturbation of dose distributions was less than manufacturing tolerances for brachytherapy sources as gleaned by an analysis of end-weld thicknesses. Volumetric Monte Carlo assessment demonstrated that TG-43 techniques overestimated calculated doses by approximately 2%. Specific dose–volume histogram metrics for prostate implants were not perturbed by inclusion of conventional or C4 spacers in clinical models.ConclusionsDosimetric perturbations of single-seed dose distributions by brachytherapy spacers exceeded 10% along the source long axes adjacent to the spacers. However, no dosimetric impact on volumetric parameters was noted for brachytherapy spacers adjacent to ¹⁰³Pd, ¹²⁵I, or ¹³¹Cs sources in the context of permanent prostate brachytherapy implants.     

Safety and efficacy of GammaTile intracranial brachytherapy implanted during awake craniotomy

INTRODUCTIONGammaTile intracranial brachytherapy (cesium-131 seeds) has demonstrated encouraging safety and local control results, and recently received Food and Drug Administration clearance for newly diagnosed and recurrent brain tumors. The authors present the first reported case of GammaTile intraoperative brachytherapy performed during an awake craniotomy.METHODSA 50-year-old man had a biopsy-proven, 2.8 cm left lateral frontal glioblastoma lesion nearing Broca's area on MRI. Despite several interventions (craniotomy, adjuvant chemoradiation, tumor treating fields) tumor progression occurred near the left parietal resection cavity. Re-resection was planned with awake craniotomy and language mapping. A preoperative planning session involving Radiation Oncology and Neurosurgery identified the area of the expected postoperative bed, and consequently five GammaTiles were ordered, each containing 4 cesium-131 3.5 U seeds.RESULTSDuring surgery, tumor mapping and bipolar stimulation were performed while the patient spoke in complete sentences. Speech arrest occurred upon stimulation at the posterior edge of the gyrus, indicative of language cortex. Microsurgical maximal safe resection subsequently occurred, and areas at risk for residual/recurrence disease were determined in consultation with Radiation Oncology. Subsequently, Neurosurgery placed all five GammaTiles (20 cesium-131 seeds total) after which closure was completed and radioactive surveys of the room remained within state statue. Postoperative dosimetry yielded excellent coverage.CONCLUSIONSThe first reported case of GammaTile intraoperative brachytherapy during awake craniotomy supports the safety and feasibility of this treatment strategy. This case indicates that for patients with tumors adjacent to eloquent cortex, awake craniotomy can allow for custom implantation of intraoperative brachytherapy following maximum safe resection.     

腮腺癌术后 125I 粒子组织间近距离治疗靶区确定方法的探讨

目的 探讨腮腺癌术后¹²⁵I粒子组织间近距离治疗靶区的确定方法。方法 2002年10月至2006年11月北京大学口腔医院的31例腮腺癌患者,男女比例14 ∶17,平均年龄38.2岁,肿瘤有包膜外浸润并与面神经关系密切(黏连或神经侵犯),采用保留面神经的肿瘤及腺体切除术,术后行¹²⁵I粒子组织间近距离治疗,匹配周缘剂量60 Gy。治疗前后行薄层螺旋CT扫描以制定治疗计划和质量验证,以腮腺周围骨性结构和肌组织为参照确定计划靶区和临床靶区,并比较治疗前后靶体积、靶区D₉₀值的差异,同时计算粒子植入后颌骨、中耳D₉₀值以及脊髓最大接受剂量。结果 ¹²⁵I粒子治疗前后靶体积、靶区D₉₀值差异无统计学意义,粒子植入后靶区D₉₀值均大于匹配周缘剂量。本组病例随访时间3~7年,未见肿瘤复发。结论 根据目前随访结果,采用本方法确定¹²⁵I粒子腮腺区组织间近距离治疗靶区,临床治疗效果满意。     

Dosimetric differences between intraoperative and postoperative plans using Cs-131 in transrectal ultrasound–guided brachytherapy for prostatic carcinoma

The aim of the study was to investigate the differences between intraoperative and postoperative dosimetry for transrectal ultrasound–guided transperineal prostate implants using cesium-131 (¹³¹Cs). Between 2006 and 2010, 166 patients implanted with ¹³¹Cs had both intraoperative and postoperative dosimetry studies. All cases were monotherapy and doses of 115 were prescribed to the prostate. The dosimetric properties (D₉₀, V₁₅₀, and V₁₀₀ for the prostate) of the studies were compared. Two conformity indices were also calculated and compared. Finally, the prostate was automatically sectioned into 6 sectors (anterior and posterior sectors at the base, midgland, and apex) and the intraoperative and postoperative dosimetry was compared in each individual sector. Postoperative dosimetry showed statistically significant changes (p < 0.01) in every dosimetric value except V₁₅₀. In each significant case, the postoperative plans showed lower dose coverage. The conformity indexes also showed a bimodal frequency distribution with the index indicating poorer dose conformity in the postoperative plans. Sector analysis revealed less dose coverage postoperatively in the base and apex sectors with an increase in dose to the posterior midgland sector. Postoperative dosimetry overall and in specific sectors of the prostate differs significantly from intraoperative planning. Care must be taken during the intraoperative planning stage to ensure complete dose coverage of the prostate with the understanding that the final postoperative dosimetry will show less dose coverage.     

不同图像引导方式下宫颈癌近距离治疗的工作流程与时效分析

目的探讨不同图像引导方式下宫颈癌患者近距离治疗计划辐射剂量及其临床工作流程中每个部分的时间效率特征, 为临床近距离治疗的统筹安排提供参考。方法回顾性分析223人次近距离治疗患者的工作流程, 将整个工作流程分为5个部分:施源器置入、图像采集、靶区和危及器官勾画、计划设计及审核、治疗实施。根据图像引导方式将近距离治疗分为X射线平片引导的二维治疗、CT和MRI引导的三维治疗, 统计3种引导方式下治疗计划的辐射剂量差异和5个部分用时, 计划辐射剂量使用总参考空气比释动能(TRAK)评价。采用SPSS 20软件非参数检验分析方法进行差异性检验。结果 X射线平片引导的二维计划TRAK 4.2(4.4, 3.9)cGy显著高于CT引导[3.5(3.9, 2.7)cGy, H=90.73, P<0.01]和MRI引导[(2.7(2.9, 2.4)cGy, H=90.73, P<0.01]的三维计划。X射线平片引导组工作流程总用时最短55.0(67.0, 50.0)min, 其次为CT引导组80.0(91.0, 72.0)min, MRI引导组总用时最长[119.0(143.0, 105.5...     

Phase II study of intraoperative dosimetry for prostate brachytherapy using registered ultrasound and fluoroscopy

PurposeTo assess the performance of a system of intraoperative dosimetry and obtain estimates of dosimetry outcomes achieved when utilizing the system in a Phase II clinical trial.Methods and MaterialsForty-five patients undergoing permanent Pd-103 seed implantation for prostate cancer were prospectively enrolled. Seed implantation was performed and dose was tracked intraoperatively using intraoperative registered ultrasound and fluoroscopy (iRUF). Three-dimensional seed locations were computed from X-rays and registered to ultrasound for intraoperative dosimetry, followed by adaptive plan modification to achieve prostate V100 ≥95% and ≥95% D90. Time required for iRUF was recorded. Postoperative CT/MRI scans were performed 1 day after the implantation and used as reference for dosimetric analysis. Dosimetric parameters for the prostate and urethra were compared between standard ultrasound-based dosimetry (USD), iRUF, and postoperative CT/MRI.ResultsMean total time for iRUF was <30 min. A mean of four seeds (0–12) were added per implant to correct cold spots discovered by iRUF. Day 1 CT/MRI prostate V100 was ≥95% for 44/45 patients; 1 patient had Day 1 V100 93%. No patient had rectal V100 exceeding 1 cc. Compared to CT/MRI, iRUF dosimetry had significantly smaller mean differences and higher correlations for all prostate and urethral dosimetric parameters examined than USD. Both USD and iRUF tended to overestimate dose, but with less bias in iRUF than USD.ConclusionsIntraoperative dosimetry utilizing iRUF was associated with acceptable increase in procedure time and enabled very high rates of achieving excellent prostate dose coverage. iRUF intraoperative dosimetry approximated postoperative CT/MRI dosimetry to a greater degree than USD for the prostate and urethra.     

Impact of MRI-based postimplant dosimetric assessment in prostate brachytherapy using contrast-enhanced T1-weighted images

PurposeTo compare contrast-enhanced T1-weighted (CE-T1WI) magnetic resonance imaging (MRI) with computed tomography (CT) for postimplant dosimetry and seed recognition in prostate brachytherapy.Methods and MaterialsA total of 245 patients who received ¹²⁵I prostate brachytherapy with or without external beam radiotherapy were enrolled. For postimplant analysis, CT and MRI scans were obtained at 1 month after seed implantation. For MRI-based dosimetry, T2-weighted images were fused with the CE-T1WI; the prostate was delineated on the T2-weighted images, and the seed detection was performed manually on the CE-T1WI. In CT-based dosimetry, the seed detection was essentially performed automatically. The dosimetric results obtained by MRI-based and CT-based dosimetry were compared.ResultsThe mean prostate D₉₀ (the minimum dose received by 90% of the prostate volume) estimated by MRI-based and CT-based dosimetry were 113% and 115%, respectively, with no significant difference. The mean prostate V₁₀₀ (the percent volume of the postimplant prostate receiving 100% of the prescribed dose) estimated by MRI-based and CT-based dosimetry were 95.2% and 95.8%, respectively, again with no significant difference. The mean prostate V₁₅₀ (the percent volume of the postimplant prostate receiving 150% of the prescribed dose) estimated by MRI-based and CT-based dosimetry were 52.8% and 57.0%, respectively (p < 0.01). In all of the 35 patients (14%) in whom the MRI-based V₁₅₀ were at least 10% lower than the CT-based results, the seed detection by CT-based dosimetry was overestimated in highly seed-clustered areas or in the areas close to calcifications because of reconstruction artifacts in CT images.ConclusionsMRI-based dosimetry using CE-T1WI appears to be acceptable. Our results suggest that MRI-based dosimetry is a practical method for estimation of the higher dose distribution, especially if seeds are clustered together or when they are close to calcifications.     

肿瘤保守切除联合放射性粒子植入治疗腮腺癌

目的 观察肿瘤保守性切除联合¹²⁵I放射性粒子组织间永久植入治疗早期腮腺癌的临床疗效。方法 选取2004年11月至2012年6月在北京大学口腔医院就诊的腮腺癌患者共30例,所有患者行腮腺肿瘤保守性切除,术后联合¹²⁵I放射性粒子组织间永久植入治疗。中位随访时间41个月,观察临床疗效及并发症。结果 患者的5年生存率及无瘤生存率为100%,无局部复发及远处转移。手术后暂时性面神经损伤发生率为3.33%（1/30）,无永久性面瘫发生,未见放射性骨髓炎、耳聋、重度张口受限等。结论 肿瘤保守性切除联合¹²⁵I放射性粒子组织间永久植入治疗早期腮腺癌临床效果良好,可保存面形,保留面神经,降低并发症发生率,提高患者生存质量。     

Evaluation of the visibility of a new thinner 125I radioactive source for permanent prostate brachytherapy

PurposeThe ¹²⁵I source currently used for prostate brachytherapy at St. James’s Institute of Oncology is a standard size seed (≈4.5 mm in length and 0.8 mm in diameter). A new, thinner seed is under evaluation. This is designed to be implanted using narrower needles, potentially reducing edema and improving the dose distribution. This study investigated the visibility of the thinner source on multimodality images and compared it with that of standard size seeds.Methods and MaterialsImages of dummy seeds of both thinner and standard size models were taken using ultrasound, fluoroscopy, computed tomography (CT), and magnetic resonance (MR) imaging. The ultrasound, fluoroscopy, and CT images were acquired with the seeds inserted into phantoms positioned in a water tank. The MR images were acquired using phantoms containing single seeds. The images were analyzed visually and quantitatively. The resolution of closely spaced seeds on CT images was investigated.ResultsThe visibility of both seeds was similar on ultrasound, fluoroscopy, and MR images. On CT images, the thinner seeds give reduced artifacts and better resolution.ConclusionsThe use of the thinner seed would have minimal effect on ultrasound and fluoroscopy imaging during treatment. However on CT images, the use of the thinner seeds may improve seed identification for post-treatment dosimetry. Further study is required into the suitability of MR images alone for post-treatment dosimetry.     

Differences between intraoperative ultrasound-based dosimetry and postoperative computed tomography-based dosimetry for permanent interstitial prostate brachytherapy

PurposeTo compare the results of intraoperative ultrasound (US)-based dosimetry with those of postimplant computed tomography (CT)-based dosimetry after ¹²⁵I prostate brachytherapy.Methods and MaterialsSubjects comprised 160 patients who underwent prostate brachytherapy using ¹²⁵I seed implants. Prescribed dose was set as 145 Gy to the periphery of the prostate. Implantation was performed using an intraoperative interactive technique. Postimplant dosimetry was performed on Days 1 and 30 after implantation using CT. Dosimetric results for the prostate, urethra, and rectum were compared among intraoperative US and CT on Day 1 (CT₁) and Day 30 (CT₃₀).ResultsMean minimal dose received by 90% of prostate volume was 133.7%, 115.6%, and 125.8% of the prescribed dose on US, CT₁, and CT₃₀, respectively: This value temporarily decreased on Day 1 and increased on Day 30. Other parameters for the prostate and urethra showed similar trends. Conversely, mean rectal volume receiving 100% of the prescribed dose was 0.69, 0.46, and 1.02 mL on US, CT₁, and CT₃₀, respectively. Rectal parameters tended to be underestimated on US relative to CT₃₀-based dosimetry. A positive linear relationship was identified between US and CT observations for every prostate parameter and the dose covering 30% of the urethra.ConclusionsOur results demonstrate significant differences between dosimetric parameters obtained by US, CT₁, and CT₃₀. However, significant correlations also exist between US and CT, at least in prostate and urethral parameters. Clarification of the degrees of difference might make US planning more feasible.     

Prostate brachytherapy seed migration to a left varicocele

PurposeTo report a rare case of seed migration to a left varicocele after transperineal interstitial prostate brachytherapy with loose iodine-125 (¹²⁵I) seeds.Methods and MaterialsA 73-year-old man presented with a serum prostate-specific antigen level of 5.21 ng/mL, Gleason score of 7 (3 + 4), and clinical T1c adenocarcinoma of the prostate. The patient underwent transperineal interstitial prostate brachytherapy with loose ¹²⁵I seeds followed by external beam radiation therapy. Two weeks after seed implantation, a followup pelvic radiograph was obtained. One month after seed implantation, a pelvic computed tomography scan for postimplant dosimetric analysis was carried out. Subsequent ultrasound examination of the scrotum was undertaken.ResultsTwo weeks after seed implantation, an anteroposterior pelvic radiograph showed that a migrated seed was overlapped by the scrotum. Postimplant pelvic computed tomography revealed that a seed had migrated to the left side of the scrotum. Subsequent ultrasound examination of the scrotum revealed that the patient had a left varicocele to which the seed had migrated. The patient had no symptoms related to the migrated seed.ConclusionsThis is the first report of seed migration to a left varicocele after transperineal interstitial prostate brachytherapy with loose ¹²⁵I seeds. For the present case, we suggest that the seed moved from the prostate to the left varicocele through the pelvic veins, bypassing the systemic circulation.