Impact of Endorectal Balloon in the Dosimetry of Prostate and Surrounding Tissues in Prostate Cancer Patients Treated with IMRT

The dosimetric effect of endorectal balloon repositioning or failure was assessed in 10 prostate cancer patients treated with intensity modulated radiation therapy (IMRT). Three extreme clinical scenarios were simulated by placing the balloon in the most superior and inferior positions within the rectum and by removing the balloon. Treatment planning was performed by obtaining a computed tomography (CT) image with the balloon in the most superior position (plan 1). Subsequently, the isodose lines of plan 1 were superpositioned over the anatomy of 2 other CTs, one obtained with the balloon in the most inferior position and another without the balloon (plans 2 and 3, respectively). Dose-volume histograms (DVHs) of the prostate and surrounding tissues were generated and compared for all 3 plans. The prescribed radiation dose to the prostate and seminal vesicles was 70 Gy in 35 fractions. Balloon repositioning resulted in significant changes only for the seminal vesicles, where the minimum doses decreased from 70.39 to 61.58 Gy, and the percent volume below 70 Gy increased from 1.62% to 8.39%. Balloon failure resulted in significant decreases in mean and minimum doses for prostate from 74.36 to 72.84 Gy and 67.62 to 50.96 Gy, respectively. Similar decreases in the mean and minimum doses were also observed for seminal vesicles from 74.21 to 64.43 Gy and 70.39 to 41.74 Gy, respectively. Balloon repositioning did not affect normal tissue doses, while balloon failure significantly decreased the upper rectum mean doses from 30.79 to 19.38 Gy. This study demonstrates that repositioning of the endorectal balloon results in increased dose inhomogeneity for seminal vesicles, while balloon failure causes significant prostate and seminal vesicle underdosing without overdosing normal tissues.     

Dose to Bone Marrow Using IMRT Techniques in Prostate Cancer Patients

Purpose: To investigate the dose distribution in active bone marrow of patients undergoing intensity-modulated radiotherapy (IMRT) for prostate cancer and compare it to the distribution in the same patients, if they had been treated using conformal plans, in order to develop criteria for optimization to minimize the estimated risk of secondary leukemia. Patients and Methods: Mean bone marrow doses were calculated for ten patients with localized prostate cancer who underwent whole-pelvis IMRT and compared to three-dimensional conformal (3-D CRT) plans prepared for the same patients. Also for comparison, the IMRT and 3-D CRT plans were produced to simulate the treatment of the prostate gland only. To measure the dose to extrapelvic bone marrow, three thermoluminescent diode (TLD) chips were placed in the middle of the sternum region inside the Rando phantom. Results: For both the pelvic and prostate-only volumes, the IMRT plans were superior to 3-D CRT plans in reducing the high dose volume to the rectum, the bladder and the small bowel while maintaining acceptable coverage of the planning target volume (PTV). For the pelvic treatment group the IMRT plans, compared to 3-D CRT, reduced the high dose volume (> 20 Gy) to os coxae, which is the main contributor of dose to pelvic bone marrow, but increased the middle dose volume (10–20 Gy). No statistically significant differences were observed for lower dose volumes (< 5 Gy). For the prostate-only treatment the IMRT plan increased the high dose volume and slightly decreased the low dose volume of pelvic bone marrow. However, for both treatments the leakage dose to extrapelvic sites was higher by a factor of 2 in IMRT plans. Conclusion: There are significant differences in the dose-volume histograms of bone marrow doses from 3-D CRT and from IMRT. Pronounced dose inhomogeneity reduces the risk of leukemia compared to homogeneous radiation exposure of the bone marrow. The mean bone marrow dose is therefore not a useful criterion to judge plan quality, since scattered low doses to distant sites may be more critical than the high dose volumes receiving > 10 Gy. The number of monitor units needed to deliver an IMRT plan affects leakage dose and their incorporation into planning constraints should be considered.     

Comparison of Prostate IMRT and VMAT Biologically Optimised Treatment Plans

Recently, a new radiotherapy delivery technique has become clinically available—volumetric modulated arc therapy (VMAT). VMAT is the delivery of IMRT while the gantry is in motion using dynamic leaf motion. The perceived benefit of VMAT over IMRT is a reduction in delivery time. In this study, VMAT was compared directly with IMRT for a series of prostate cases. For 10 patients, a biologically optimized seven-field IMRT plan was compared with a biologically optimized VMAT plan using the same planning objectives. The Pinnacle RTPS was used. The resultant target and organ-at-risk dose-volume histograms (DVHs) were compared. The normal tissue complication probability (NTCP) for the IMRT and VMAT plans was calculated for 3 model parameter sets. The delivery efficiency and time for the IMRT and VMAT plans was compared. The VMAT plans resulted in a statistically significant reduction in the rectal V25Gy parameter of 8.2% on average over the IMRT plans. For one of the NTCP parameter sets, the VMAT plans had a statistically significant lower rectal NTCP. These reductions in rectal dose were achieved using 18.6% fewer monitor units and a delivery time reduction of up to 69%. VMAT plans resulted in reductions in rectal doses for all 10 patients in the study. This was achieved with significant reductions in delivery time and monitor units. Given the target coverage was equivalent, the VMAT plans were superior.     

VMAT vs. 7-Field-IMRT: Assessing the Dosimetric Parameters of Prostate Cancer Treatment with a 292-Patient Sample

We compared normal tissue radiation dose for the treatment of prostate cancer using 2 different radiation therapy delivery methods: volumetric modulated arc therapy (VMAT) vs. fixed-field intensity-modulated radiation therapy (IMRT). Radiotherapy plans for 292 prostate cancer patients treated with VMAT to a total dose of 7740 cGy were analyzed retrospectively. Fixed-angle, 7-field IMRT plans were created using the same computed tomography datasets and contours. Radiation doses to the planning target volume (PTV) and organs at risk (bladder, rectum, penile bulb, and femoral heads) were measured, means were calculated for both treatment methods, and dose-volume comparisons were made with 2-tailed, paired t-tests. The mean dose to the bladder was lower with VMAT at all measured volumes: 5, 10, 15, 25, 35, and 50% (p < 0.05). The mean doses to 5 and 10% of the rectum, the high-dose regions, were lower with VMAT (p < 0.05). The mean dose to 15% of the rectal volume was not significantly different (p = 0.95). VMAT exposed larger rectal volumes (25, 35, and 50%) to more radiation than fixed-field IMRT (p < 0.05). Average mean dose to the penile bulb (p < 0.05) and mean dose to 10% of the femoral heads (p < 0.05) were lower with VMAT. VMAT therapy for prostate cancer has dosimetric advantages for critical structures, notably for high-dose regions compared with fixed-field IMRT, without compromising PTV coverage. This may translate into reduced acute and chronic toxicity.     

Postoperative Intensity Modulated Radiation Therapy in High Risk Prostate Cancer: A Dosimetric Comparison

The aim of this study was to compare intensity-modulated radiation therapy (IMRT) with 3D conformal technique (3D-CRT), with respect to target coverage and irradiation of organs at risk for high dose postoperative radiotherapy (PORT) of the prostate fossa. 3D-CRT and IMRT treatment plans were compared with respect to dose to the rectum and bladder. The dosimetric comparison was carried out in 15 patients considering 2 different scenarios: (1) exclusive prostate fossa irradiation, and (2) pelvic node irradiation followed by a boost on the prostate fossa. In scenario (1), a 3D-CRT plan (box technique) and an IMRT plan were calculated and compared for each patient. In scenario (2), 3 treatment plans were calculated and compared for each patient: (a) 3D-CRT box technique for both pelvic (prophylactic nodal irradiation) and prostate fossa irradiation (3D-CRT only); (b) 3D-CRT box technique for pelvic irradiation followed by an IMRT boost to the prostatic fossa (hybrid 3D-CRT and IMRT); and (c) IMRT for both pelvic and prostate fossa irradiation (IMRT only). For exclusive prostate fossa irradiation, IMRT significantly reduced the dose to the rectum (lower Dmean, V50%, V75%, V90%, V100%, EUD, and NTCP) and the bladder (lower Dmean, V50%, V90%, EUD and NTCP). When prophylactic irradiation of the pelvis was also considered, plan C (IMRT only) performed better than plan B (hybrid 3D-CRT and IMRT) as respect to both rectum and bladder irradiation (reduction of Dmean, V50%, V75%, V90%, equivalent uniform dose [EUD], and normal tissue complication probability [NTCP]). Plan (b) (hybrid 3D-CRT and IMRT) performed better than plan (a) (3D-CRT only) with respect to dose to the rectum (lower Dmean, V75%, V90%, V100%, EUD, and NTCP) and the bladder (Dmean, EUD, and NTCP). Postoperative IMRT in prostate cancer significantly reduces rectum and bladder irradiation compared with 3D-CRT.     

Skin Dose Impact from Vacuum Immobilization Device and Carbon Fiber Couch in Intensity Modulated Radiation Therapy for Prostate Cancer

To investigate the unexpected skin dose increase from intensity-modulated radiation therapy (IMRT) on vacuum cushions and carbon-fiber couches and then to modify the dosimetric plan accordingly. Eleven prostate cancer patients undergoing IMRT were treated in prone position with a vacuum cushion. Two under-couch beams scattered the radiation from the vacuum cushion and carbon-fiber couch. The IMRT plans with both devices contoured were compared with the plans not contouring them. The skin doses were measured using thermoluminescent dosimeters (TLDs) placed on the inguinal regions in a single IMRT fraction. Tissue equivalent thickness was transformed for both devices with the relative densities. The TLD-measured skin doses (59.5 ± 9.5 cGy and 55.6 ± 5.9 cGy at left and right inguinal regions, respectively) were significantly higher than the calculated doses (28.7 ± 4.7 cGy; p = 2.2 × 10⁻⁵ and 26.2 ± 4.3 cGy; p = 1.5 × 10⁻⁵) not contouring the vacuum cushion and carbon-fiber couch. The calculated skin doses with both devices contoured (59.1 ± 8.8 cGy and 55.5 ± 5.7 cGy) were similar to the TLD-measured doses. In addition, the calculated skin doses using the vacuum cushion and a converted thickness of the simulator couch were no different from the TLD-measured doses. The recalculated doses of rectum and bladder did not change significantly. The dose that covered 95% of target volume was less than the prescribed dose in 4 of 11 patients, and this problem was solved after re-optimization applying the corrected contours. The vacuum cushion and carbon-fiber couch contributed to increased skin doses. The tissue-equivalent-thickness method served as an effective way to correct the dose variations.     

Treatment and Dosimetric Advantages Between VMAT, IMRT, and Helical TomoTherapy in Prostate Cancer

We investigated the possible treatment and dosimetric advantage of volumetric modulated arc therapy (VMAT) over step-and-shoot intensity-modulated radiation therapy (step-and-hhoot IMRT) and helical tomotherapy (HT). Twelve prostate cancer patients undergoing VMAT to the prostate were included. Three treatment plans (VMAT, step-and-shoot IMRT, HT) were generated for each patient. The doses to clinical target volume and 95% of planning target volume were both ≥78 Gy. Target coverage, conformity index, dose to rectum/bladder, monitor units (MU), treatment time, equivalent uniform dose (EUD), normal tissue complication probability (NTCP) of targets, and rectum/bladder were compared between techniques. HT provided superior conformity and significantly less rectal volume exposed to 65 Gy and 40 Gy, as well as EUD/NTCP of rectum than step-and-shoot IMRT, whereas VMAT had a slight dosimetric advantage over step-and-shoot IMRT. Notably, significantly lower MUs were needed for VMAT (309.7 ± 35.4) and step-and-shoot IMRT (336.1 ± 16.8) than for HT (3368 ± 638.7) (p < 0.001). The treatment time (minutes) was significantly shorter for VMAT (2.6 ± 0.5) than step-and-shoot IMRT (3.8 ± 0.3) and HT (3.8 ± 0.6) (p < 0.001). Dose verification of VMAT using point dose and film dosimetry met the accepted criteria. VMAT and step-and-shoot IMRT have comparable dosimetry, but treatment efficiency is significantly higher for VMAT than for step-and-shoot IMRT and HT.     

磁敏感成像技术与磁共振动态增强扫描对前列腺癌和前列腺炎鉴别诊断价值的对比分析

目的 探讨病变内磁敏感性效应(SusE)与磁共振动态增强扫描(DCE-MRI)定量参数在外周带前列腺癌和前列腺炎鉴别诊断中的价值.方法 回顾性分析65例行3.0 TMR磁敏感成像(SwI)和DCE扫描并经穿刺活检病理证实的前列腺外周带T2信号减低的初诊患者,其中前列腺癌32例,前列腺炎33例.以4分制评估外周带T2低信号灶及邻近外周带SusE,并测量相应层面病灶区及正常前列腺外周带DCE-MRI定量参数转运常数(Ktrans)、血管外细胞外间隙体积百分数(Ve)及速率常数(Kep).通过Spearman分析比较SusE与Ktrans、Kep、Ve的相关性.通过Mann-Whitney test检验比较前列腺癌和前列腺炎病灶SusE差异.单因素方差分析比较Ktrans、Ke.、Ve在前列腺癌、前列腺炎和正常前列腺外周带间的差异.ROC曲线比较SWI和DCE的诊断准确性.结果 SusE与Ktra、Kep呈正线性相关(r值分别为0.419、0.219,P值分别为＜0.001、0.034),与Ve无相关性(r=0.088,P=0.402).在外周带前列腺癌和前列腺炎中SusE、Ktrans、Ke.差异均有统计学意义(P＜0.05),Ve差异无统计学意义(P＞0.05).以0分作为界值点,SusE鉴别前列腺癌和前列腺炎的敏感性、特异性、ROC曲线下面积分别为73.68％、65.62％、0.767;以0.103 min-1作为界值,Ktrans鉴别前列腺癌和前列腺炎的敏感性、特异性、ROC曲线下面积分别为78.12％、84.21％、0.753.以0.431 min-1作为界值,Ken鉴别前列腺癌和前列腺炎的敏感性、特异性、ROC曲线下面积分别为78.95％、59.38％、0.767.结论SWI半定量参数SusE与动态增强定量参数具有一定的相关性,可作为DCE-MRI的一种补充方法.病灶内微出血灶可以作为辅助鉴别诊断前列腺癌与前列腺炎的证据.     

前列腺癌血清PSA与磁共振波谱变化的相关性研究

目的：探讨前列腺癌患者磁共振波谱（MRS）改变与血清中总前列腺特异抗原（TPSA）、游离前列腺特异抗原（fPSA）及两者比值（f/T）的相关性。方法：30例经活检证实为前列腺癌患者TPSA、fPSA及f/T值为参数,将3组数据分别与前列腺癌兴趣区所得（Cho＋Cr）/Cit值的平均数进行相关性分析。结果：CC/C比值与血清总PSA浓度平均值呈正相关关系（相关系数r=0.750）,差异具有显著性意义（P〈0.01）;与血清游离PSA浓度呈正相关关系（相关系数r=0.814）,差异具有显著性意义（P〈0.05）;与f/T值呈正相关关系（相关系数r=0.189）,差异无显著性意义（P=0.318〉0.05）。结论：CC/C值与血清总PSA浓度及游离PSA浓度呈正相关,而CC/C值较高患者更易于发现和确定前列腺内发生代谢改变的区域,因此PSA值较高患者行MRS更具临床意义。     

Volumetric Modulated Arc Therapy vs. IMRT for the Treatment of Distal Esophageal Cancer

Several studies have demonstrated that volumetric modulated arc therapy (VMAT) has the ability to reduce monitor units and treatment time when compared with intensity-modulated radiation therapy (IMRT). This study aims to demonstrate that VMAT is able to provide adequate organs at risk (OAR) sparing and planning target volume (PTV) coverage for adenocarcinoma of the distal esophagus while reducing monitor units and treatment time. Fourteen patients having been treated previously for esophageal cancer were planned using both VMAT and IMRT techniques. Dosimetric quality was evaluated based on doses to several OARs, as well as coverage of the PTV. Treatment times were assessed by recording the number of monitor units required for dose delivery. Body V₅ was also recorded to evaluate the increased volume of healthy tissue irradiated to low doses. Dosimetric differences in OAR sparing between VMAT and IMRT were comparable. PTV coverage was similar for the 2 techniques but it was found that IMRT was capable of delivering a slightly more homogenous dose distribution. Of the 14 patients, 12 were treated with a single arc and 2 were treated with a double arc. Single-arc plans reduced monitor units by 42% when compared with the IMRT plans. Double-arc plans reduced monitor units by 67% when compared with IMRT. The V₅ for the body was found to be 18% greater for VMAT than for IMRT. VMAT has the capability to decrease treatment times over IMRT while still providing similar OAR sparing and PTV coverage. Although there will be a smaller risk of patient movement during VMAT treatments, this advantage comes at the cost of delivering small doses to a greater volume of the patient.     

前列腺癌及直肠癌对盆腔筋膜侵犯的MRI表现

目的 探讨前列腺癌及直肠癌对盆腔主要筋膜侵犯的MRI表现特点.资料与方法 回顾性分析5例前列腺肿瘤侵犯尿生殖膈及Denonvilliers筋膜患者、4例直肠肿瘤侵犯直肠系膜或直肠系膜筋膜患者的MRI表现特点.结果 肿瘤对筋膜侵犯的MRI表现可分为直接征象和间接征象,直接征象为筋膜连续性中断,局限结节样侵犯;间接征象为脂肪间隙消失,周围淋巴结肿大.结论 MRI可以清晰地显示盆腔筋膜受累情况,对确定肿瘤分期有意义.     

Locoregional Failure Analysis in Head-and-Neck Cancer Patients Treated with IMRT

PURPOSE: Analysis of locoregional failure in head-and-neck cancer (HNC) following intensity-modulated radiation therapy (IMRT), with focus on the location of locoregional failures in relation to the chosen planning target volumes (PTVs) and dose distributions. PATIENTS AND METHODS: Between January 2002 and May 2006, 280 HNC patients were subjected to IMRT at the authors' institution. Mean follow-up was 23.2 months (3-59.3 months). Definitive IMRT was performed in 75% of all patients. In 71%, simultaneous cisplatin-based chemotherapy was given. 70% of patients presented with T3/4, T1-2 N2c/3 or recurred disease. Locoregional failure patterns were analyzed. RESULTS: 2-year local, nodal, distant, disease-free, and overall survival rates were 80%, 87%, 87%, 73%, and 82%, respectively. 46 local (16%) and 31 nodal (11%) failures have been observed so far. Local tumor persistence was seen in 23/46 cases (50%), and nodal persistence in 12/31 (39%), respectively. One marginal local failure developed in a patient referred for a recurred oral cavity tumor. Three nodal failures developed outside the PTVs at unexpected locations. All other failures have been confirmed "in field". No failure occurred in level Ib or upper level II. Local failure occurred mainly following definitive IMRT for large tumors, nodal failure only in nodally positive patients with nodal high-risk features. CONCLUSION: The dose-volume concept as used here has shown to be adequate, with disease failure developing at the site of the initial gross tumor manifestation inside the boost volume.     

前列腺穿刺活检联合血清前列腺特异抗原在前列腺癌诊断中的意义

目的探讨经直肠前列腺穿刺活检与血清前列腺特异抗原联合检测在前列腺癌诊断中的价值。方法对61例经直肠指检阳性,和（或）总前列腺特异抗原≥10ug／L,和（或）游离前列腺特异抗原/总前列腺特异抗原〈0．25的可疑前列腺癌患者,在超声引导下经直肠前列腺多点穿刺活检。结果61例中,前列腺活检病理检查诊断为前列腺癌25例（40．98％）,良性前列腺增生36例（59．02％）。其中,游离前列腺特异抗原／总前列腺特异抗原〈0．20的患者中前列腺癌检出8例（8／13,占61．54％）。结论总前列腺特异抗原≥10ug／L,特别是游离前列腺特异抗原／总前列腺特异抗原〈0．20对前列腺癌的诊断比前列腺穿刺活检更为敏感,两者联合检测对临床诊治具有更重要的价值和意义。     

Advantages and limitations of navigation-based multicriteria optimization (MCO) for localized prostate cancer IMRT planning

Efficacy of inverse planning is becoming increasingly important for advanced radiotherapy techniques. This study’s aims were to validate multicriteria optimization (MCO) in RayStation (v2.4, RaySearch Laboratories, Sweden) against standard intensity-modulated radiation therapy (IMRT) optimization in Oncentra (v4.1, Nucletron BV, the Netherlands) and characterize dose differences due to conversion of navigated MCO plans into deliverable multileaf collimator apertures. Step-and-shoot IMRT plans were created for 10 patients with localized prostate cancer using both standard optimization and MCO. Acceptable standard IMRT plans with minimal average rectal dose were chosen for comparison with deliverable MCO plans. The trade-off was, for the MCO plans, managed through a user interface that permits continuous navigation between fluence-based plans. Navigated MCO plans were made deliverable at incremental steps along a trajectory between maximal target homogeneity and maximal rectal sparing. Dosimetric differences between navigated and deliverable MCO plans were also quantified. MCO plans, chosen as acceptable under navigated and deliverable conditions resulted in similar rectal sparing compared with standard optimization (33.7 ± 1.8 Gy vs 35.5 ± 4.2 Gy, p = 0.117). The dose differences between navigated and deliverable MCO plans increased as higher priority was placed on rectal avoidance. If the best possible deliverable MCO was chosen, a significant reduction in rectal dose was observed in comparison with standard optimization (30.6 ± 1.4 Gy vs 35.5 ± 4.2 Gy, p = 0.047). Improvements were, however, to some extent, at the expense of less conformal dose distributions, which resulted in significantly higher doses to the bladder for 2 of the 3 tolerance levels. In conclusion, similar IMRT plans can be created for patients with prostate cancer using MCO compared with standard optimization. Limitations exist within MCO regarding conversion of navigated plans to deliverable apertures, particularly for plans that emphasize avoidance of critical structures. Minimizing these differences would result in better quality treatments for patients with prostate cancer who were treated with radiotherapy using MCO plans.     

直肠内线圈MR在前列腺癌诊断中作用:肿瘤位置和分期

目的:利用直肠内线圈MR成像显示前列腺癌及进行临床分期。方法:75例前列腺癌,年龄30~81岁,平均年龄为65岁。均经直肠前列腺穿刺活检术获得病理结果。Philips Intera 1.5T Master超导型临床医用磁共振仪,采用标准直肠腔内线圈。对前列腺包膜显示及是否侵犯,精囊侵犯和淋巴结转移进行了分析。结果:直肠内线圈的应用可显著提高前列腺图像的信噪比,可清晰显示前列腺癌病变、局部解剖、包膜、血管神经丛,并能显示前列腺癌转移及盆腔淋巴结转移途径。结论:直肠内线圈可以确定前列腺癌肿瘤的位置,以及包膜和精囊血管侵犯,并有利于分析前列腺癌淋巴结转移的方式。     

Testicular Dose in Prostate Cancer Radiotherapy

Purpose: To determine the dose received by the unshielded testicles during a course of 20-MV conventional external-beam radiotherapy for patients with localized prostate cancer. Critical evaluation of the potential impact on fertility and hormonal impairment in these patients according to the literature. Patients and Methods: The absolute dose received by the testicles of 20 randomly selected patients undergoing radiotherapy of prostate cancer was measured by on-line thermoluminescence dosimetry. Patients were treated in supine position with an immobilization cushion under their knees. A flexible tube, containing three calibrated thermoluminescence dosimeters (TLDs) was placed on top or underneath the testicle closest to the perineal region with a day-to-day alternation. The single dose to the planning target volume was 1.8 Gy. Ten subsequent testicle measurements were performed on each patient. The individual TLDs were then read out and the total absorbed dose was calculated. Results: The mean total dose (± standard deviation) measured in a series of 10 subsequent treatment days in all patients was 49 cGy (± 36 cGy). The calculated projected doses made on a standard series of 40 fractions of external-beam radiotherapy were 196 cGy (± 145 cGy). The results of this study are appraised with the available data in the literature. Conclusion: The dose received by the unshielded testes can be assessed as a risk for permanent infertility and impairment of hormonal function in prostate cancer patients treated with external-beam radiotherapy.     

15例前列腺癌侵犯膀胱误诊为膀胱癌的MRI表现

目的分析膀胱受累的前列腺癌的MRI表现,评价MRI对前列腺癌的定性诊断价值,避免伴膀胱受累的前列腺癌误诊为膀胱肿瘤。资料与方法回顾性分析15例行MRI检查前曾误诊为膀胱癌的前列腺癌患者的临床及MRI资料。结果 15例误诊病变MRI均明确诊断为前列腺癌,其中C期10例,D期5例。结论 MRI是诊断前列腺癌良好的影像学方法,特别是当病变累及膀胱时,可很好地避免误诊为膀胱肿瘤,再结合其他检查方法,可提高前列腺癌的诊断准确率。