Ⅰ期睾丸精原细胞瘤术后三维适形放疗与常规放疗的剂量学对比分析

目的 比较睾丸精原细胞瘤术后行三维适形放疗（3D CRT）与传统放疗照射靶区及周围正常组织的剂量学差异。方法 对12例确诊的Ⅰ期睾丸精原细胞瘤患者经腹股沟高位睾丸切除术后行术后放疗。利用治疗计划系统（TPS） 为每例患者设计3D-CRT计划和虚拟常规计划（VCP）。应用剂量体积直方图（DVH）比较两种治疗计划的靶区适形度指数（CI）、不均匀性指数（HI）和正常组织受量。结果 3D-CRT计划的CI及HI均优于VCP计划,CI值分别为0.88±0.06和0.82±0.05,HI值分别为0.15±0.03和0.29±0.11（P＜0.05）。3D-CRT计划的照射体积（IV）显著低于VCP计划,分别为（5268.20±1018.60）cm³和（5970.24±1471.49）cm³（P＜0.05）。3D-CRT计划的小肠平均剂量以及V15低于VCP计划（P＜0.05）,睾丸的平均剂量低于VCP计划（P＜0.05）。结论 常规照射野是根据患者的骨性标志确定下来,未必适应于每个患者,3D-CRT更加个体化。此外3D-CRT在靶区覆盖率、剂量适形度及剂量均匀性方面均优于虚拟常规计划,同时降低了小肠低剂量照射体积和睾丸的散射剂量,这些剂量学方面的优势能否转换成临床受益还需要进一步临床验证。     

CT与MRI图像融合在颅内肿瘤三维适形放疗中的应用

目的采用CT与MRI图像融合技术,为颅脑肿瘤三维适形放疗提供更精确地靶区定义。方法对25例脑瘤患者分别使用CT和MRI进行三维适形放疗定位,比较2种图像采集方式确定靶区的不同。以MRI确定的靶区作为大体靶区(GTV),以CT图像提供的CT值进行剂量计算,制定放疗计划。结果25例患者均接受了CT和MRI定位,解剖结构及体表标记均基本重合。其中23例患者CT和MRI扫描后显示病灶数目相同,2例患者显示病灶数目不同。CT比MRI扫描GTV体积增大者10例,缩小者15例。放疗结束后复查颅脑MRI评价疗效,有效率为64.0%。结论CT与MRI融合技术进行三维立体适形放疗定位,提高了GTV确定的精确性,提高了适形放疗的精度。     

Automatic segmentation of pelvic structures from magnetic resonance images for prostate cancer radiotherapy

PURPOSE: Target-volume and organ-at-risk delineation is a time-consuming task in radiotherapy planning. The development of automated segmentation tools remains problematic, because of pelvic organ shape variability. We evaluate a three-dimensional (3D), deformable-model approach and a seeded region-growing algorithm for automatic delineation of the prostate and organs-at-risk on magnetic resonance images. METHODS AND MATERIALS: Manual and automatic delineation were compared in 24 patients using a sagittal T2-weighted (T2-w) turbo spin echo (TSE) sequence and an axial T1-weighted (T1-w) 3D fast-field echo (FFE) or TSE sequence. For automatic prostate delineation, an organ model-based method was used. Prostates without seminal vesicles were delineated as the clinical target volume (CTV). For automatic bladder and rectum delineation, a seeded region-growing method was used. Manual contouring was considered the reference method. The following parameters were measured: volume ratio (Vr) (automatic/manual), volume overlap (Vo) (ratio of the volume of intersection to the volume of union; optimal value = 1), and correctly delineated volume (Vc) (percent ratio of the volume of intersection to the manually defined volume; optimal value = 100). RESULTS: For the CTV, the Vr, Vo, and Vc were 1.13 (+/-0.1 SD), 0.78 (+/-0.05 SD), and 94.75 (+/-3.3 SD), respectively. For the rectum, the Vr, Vo, and Vc were 0.97 (+/-0.1 SD), 0.78 (+/-0.06 SD), and 86.52 (+/-5 SD), respectively. For the bladder, the Vr, Vo, and Vc were 0.95 (+/-0.03 SD), 0.88 (+/-0.03 SD), and 91.29 (+/-3.1 SD), respectively. CONCLUSIONS: Our results show that the organ-model method is robust, and results in reproducible prostate segmentation with minor interactive corrections. For automatic bladder and rectum delineation, magnetic resonance imaging soft-tissue contrast enables the use of region-growing methods.     

Static pion beam treatment planning of deep seated tumors using computerized tomographic scans.

Static negative pion beam treatment of deep seated tumors is in progress at LAMPF. The influence of the physical principles of pions on treatment planning, e.g., an enhanced peak dose, multiple scattering, variations of beam quality, pin beam emittance, and a fixed vertical beam, are discussed. Computerized tomographic (CT) scan data have proven invaluable in providing quantitative information on inhomogeneities within the anatomy. The methods of designing collimation and compensating bolus for tailoring the pion beam to individual patient ports are described. An interim method, using dosimetry measurements in a water phantom and CT scan data to construct patient isodose distribution is outlined. Typical treatment plans for patients with abdominal and head and neck cancers are presented. The method of X-ray simulation in verifying localization of CT-defined tumor volumes is demonstrated for the head and neck.     

鼻咽癌后程三维适形放疗正向计划的设计及优化

目的：探讨鼻咽癌后程三维适形放射治疗正向计划的设计及优化方法。方法：随机选取20例鼻咽癌后程加量的患者,在PROWESS PANTHER计划系统上进行三维适形放射治疗正向计划的设计及优化,通过射野数目、射野方向、射野权重因子的合理设定及选择,结合DVH图和剂量曲线分布情况选择最优方案。结果：分析患者的DVH图,显示各靶区均能达到较好的剂量曲线分布,在给予靶区致死剂量的同时,周围危及器官受量都在其耐受剂量范围内。结论：在没有开展调强放疗技术的单位,根据鼻咽癌患者病变侵犯情况,选择合适的射野进行三维适形放疗正向计划设计及优化,也能得到符合临床要求的较佳的治疗计划,从而可提高鼻咽癌局部控制率,有效保护危及器官,提高病人的生存质量。     

Interest of positron-emission tomography and magnetic resonance imaging for radiotherapy planning and control

Computed tomography (CT) in the treatment position is currently indispensable for planning radiation therapy. Other imaging modalities, such as magnetic resonance imaging (MRI) and positron emission-tomography (PET), can be used to improve the definition of the tumour and/or healthy tissue but also to provide functional data of the target volume. Accurate image registration is essential for treatment planning, so MRI and PET scans should be registered at the planning CT scan. Hybrid PET/MRI scans with a hard plane can be used but pose the problem of the absence of CT scans. Finally, techniques for moving the patient on a rigid air-cushioned table allow PET/CT/MRI scans to be performed in the treatment position while limiting the patient's movements exist. At the same time, the advent of MRI–linear accelerator systems allows to redefine image-guided radiotherapy and to propose treatments with daily recalculation of the dose. The place of PET during treatment remains more confidential and currently only in research and prototype status. The same development of imaging during radiotherapy is underway in proton therapy.     

The utility of multimodality imaging with CT and MRI in defining rectal tumour volumes for radiotherapy treatment planning: a pilot study

Aims: This study compares the volumetric and spatial relationships of gross tumour volume (GTV) derived from CT (CT-GTV) and GTV derived from MRI (MR-GTV) to determine the utility of multi-modality imaging for radiotherapy treatment planning in rectal cancer. Methods and Materials: Fifteen patients with T3 rectal cancer were accrued over 18 months. The male : female ratio was 2:1. The average age was 60.3 years (range 38–79). All patients underwent a diagnostic MRI and CT and MRI simulation. Data sets were co-registered. A site specialised diagnostic radiologist contoured all volumes in consultation with a radiation oncologist. CT-GTV was contoured while blinded to MR data sets. MR-GTV was contoured independently 2–4 weeks later whilst blinded to its respective CT-GTV data. Tumour volumes were analysed for three anatomical subregions (sigmoid, rectal and anal). Reference points on tumour volumes were used for spatial comparison and analysis. Results: The mean CT-GTV/MR-GTV ratio was 1.2 (range 0.5–2.9). The tumour volume ratios for the rectal subregion were well correlated. CT-GTV provided adequate spatial coverage of tumour in reference to MR-GTV with the average mean discrepancy of 0.12 (range −0.08–0.38) or a maximum discrepancy of <0.4 cm (1.54 standard deviation). CT-GTV coverage was inadequate for tumours with MRI evidence of anal and sigmoid invasion. Conclusions: Conventional simulation CT imaging provided a reasonable estimate of the GTV. Multi-modality imaging with staging MRI can assist target volume definition where there is involvement of the sigmoid and anorectal region and avoid geographic misses. The role of a simulation MRI may aid in this process but remains investigational.     

Comparison of inverse-planned three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for non-small-cell lung cancer

PURPOSE: Lungs are the major dose-limiting organ during radiotherapy (RT) for non-small-cell lung cancer owing to the development of pneumonitis. This study compared intensity-modulated RT (IMRT) with three-dimensional conformal RT (3D-CRT) in reducing the dose to the lungs. METHODS: Ten patients with localized non-small-cell lung cancer underwent computed tomography (CT). The planning target volume (PTV) was defined and the organs at risk were outlined. An inverse-planning program, AutoPlan, was used to design the beam angle-optimized six-field noncoplanar 3D-CRT plans. Each 3D-CRT plan was compared with a series of five IMRT plans per patient. The IMRT plans were created using a commercial algorithm and consisted of a series of three, five, seven, and nine equidistant coplanar field arrangements and one six-field noncoplanar plan. The planning objectives were to minimize the lung dose while maintaining the dose to the PTV. The percentage of lung volume receiving >20 Gy (V20) and the percentage of the PTV covered by the 90% isodose (PTV90) were the primary endpoints. The PTV90/V20 ratio was used as the parameter accounting for both the reduction in lung volume treated and the PTV coverage. RESULTS: All IMRT plans, except for the three-field coplanar plans, improved the PTV90/V20 ratio significantly compared with the optimized 3D-CRT plan. Nine coplanar IMRT beams were significantly better than five or seven coplanar IMRT beams, with an improved PTV90/V20 ratio. CONCLUSION: The results of our study have shown that IMRT can reduce the dose to the lungs compared with 3D-CRT by improving the conformity of the plan.     

FDG-PET/CT imaging for staging and target volume delineation in preoperative conformal radiotherapy of rectal cancer

PURPOSE: To investigate the potential impact of using (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) on staging and target volume delineation for patients affected by rectal cancer and candidates for preoperative conformal radiotherapy. METHODS AND MATERIALS: Twenty-five patients diagnosed with rectal cancer T3-4 N0-1 M0-1 and candidates for preoperative radiotherapy underwent PET/CT simulation after injection of 5.18 MBq/kg of FDG. Clinical stage was reassessed on the basis of FDG-PET/CT findings. The gross tumor volume (GTV) and the clinical target volume (CTV) were delineated first on CT and then on PET/CT images. The PET/CT-GTV and PET/CT-CTV were analyzed and compared with CT-GTV and CT-CTV, respectively. RESULTS: In 4 of 25 cases (24%), PET/CT affected tumor staging or the treatment purpose. In 3 of 25 cases (12%) staged N0 M0, PET/CT showed FDG uptake in regional lymph nodes and in a case also in the liver. In a patient with a single liver metastasis PET/CT detected multiple lesions, changing the treatment intent from curative to palliative. The PET/CT-GTV and PET/CT-CTV were significantly greater than the CT-GTV (p = 0.00013) and CT-CTV (p = 0.00002), respectively. The mean difference between PET/CT-GTV and CT-GTV was 25.4% and between PET/CT-CTV and CT-CTV was 4.1%. CONCLUSIONS: Imaging with PET/CT for preoperative radiotherapy of rectal cancer may lead to a change in staging and target volume delineation. Stage variation was observed in 12% of cases and a change of treatment intent in 4%. The GTV and CTV changed significantly, with a mean increase in size of 25% and 4%, respectively.     

Pericardial lipoma: Ultrasound,computed tomography and magnetic resonance imaging findings

Primary tumours of the heart and pericardium are extremely rare. Cardiac lipomas account for only 10% of all primary cardiac tumours. A case of surgically proven pericardial lipoma demonstrated by ultrasound, CT and MRI is presented here.     

Correlation of three-dimensional magnetic resonance imaging with precise histopathological map concerning carcinoma extension in the breast

This study was initiated to clarify the ability of magnetic resonance imaging (MRI) in defining breast carcinoma extension by comparing MRI to detailed histopathological analysis. Mastectomy (n=14) or quadrantectomy (n=44) specimens were sub-serially sectioned and mapped in detail in 58 breast cancer patients. Morphologically, we classified the lesions utilizing MRI into three patterns in relation to their histology. Numerically, we assessed the maximum distance of carcinoma extension using MRI, mammography, and ultrasonography (US). Linear regression was calculated for each of the three imaging measurements versus histopathological measurements.Three imaging patterns were observed by MRI, (1) localized (n=30), (2) segmentally extended (n=19), and (3) irregularly extended (n=5). The localized pattern showed a distinct focal mass, but in 10 cases, microscopic ductal carcinoma in situ (DCIS), or invasive lobular carcinoma, which were not depicted by MRI, existed. The segmentally extended pattern showed diffuse enhancement along duct–lobular segments, forming a cone shape. Histologically, pure (n=4) or predominant (n=10) DCIS was distributed segmentally. The irregularly extended pattern showed thick branches extending out from the index tumor which were histologically revealed to be stromal invasion of ductal carcinoma. From the results of linear regressions, MRI was the most accurate modality in histologically measuring the extent of the cancer. When cases were limited to patients who were classified into segmentally or irregularly extended pattern by MRI (n=24), MRI was more accurate than mammography and US, even if they were combined (P<0.05).MRI may provide additional information concerning carcinoma extension prior to surgery, especially in patients classified into extended patterns by MRI.     

适形放疗后肝损伤的CT和MRI表现

目的 对原发性肝癌适形放疗后的患者进行CT、MR平扫或增强扫描,以发现其特征,为与适形放疗后病灶未控或复发提供鉴别依据.方法 33例单发肝癌患者采用适形放疗,36～48 Gy/8～12次,隔日1次.1～3个月后开始CT、MRI复查.对TDF值≥90及＜90时与CT影像学异常,关系进行四格表精确检验法统计学处理.结果 15例次CT平扫表现为低密度.增强扫描无强化,6例次;动脉期为低密度,门脉期或延迟期呈强化状态,2例次;早期至延迟期均强化,2例次.5例次MRI平扫T1加权呈低或等信号,4例次T2加权呈等信号,1例呈略高信号.5例增强扫描出现进行性强化.TDF值≥90与＜90的放射剂量导致的CT影像学异常,差异具有显著性(P＝0.003).结论 照射后,高剂量照射区的肝脏CT可表现为低密度,MRI T1加权表现为低或等信号;可以出现强化,特征为进行性或持续性强化.当TDF值≥90时,容易出现CT影像学异常.     

Analysis of biochemical control and prognostic factors in patients treated with either low-dose three-dimensional conformal radiation therapy or high-dose intensity-modulated radiotherapy for localized prostate cancer

PURPOSE: To identify prognostic factors and evaluate biochemical control rates for patients with localized prostate cancer treated with either high-dose intensity-modulated radiotherapy (IMRT) or conventional-dose three-dimensional conformal radiotherapy 3D-CRT. METHODS: Four hundred sixteen patients with a minimum follow-up of 3 years (median, 5 years) were included. Two hundred seventy-one patients received 3D-CRT with a median dose of 68.4 Gy (range, 66-71 Gy). The next 145 patients received IMRT with a median dose of 75.6 Gy (range, 70.2-77.4 Gy). Biochemical control rates were calculated according to both American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definitions. Prognostic factors were identified using both univariate and multivariate analyses. RESULTS: The 5-year biochemical control rate was 60.4% for 3D-CRT and 74.1% for IMRT (p < 0.0001, first ASTRO Consensus definition). Using the ASTRO Phoenix definition, the 5-year biochemical control rate was 74.4% and 84.6% with 3D-RT and IMRT, respectively (p = 0.0326). Univariate analyses determined that PSA level, T stage, Gleason score, perineural invasion, and radiation dose were predictive of biochemical control. On multivariate analysis, dose, Gleason score, and perineural invasion remained significant. CONCLUSION: On the basis of both ASTRO definitions, dose, Gleason score, and perineural invasion were predictive of biochemical control. Intensity-modulated radiotherapy allowed delivery of higher doses of radiation with very low toxicity, resulting in improved biochemical control.     

Localization of structures for pion radiotherapy by computerized tomography and orthodiagraphic projection

Clinical trials of pion radiotherapy are being conducted at the Clinton P. Anderson Meson Physics Facility (LAMPF) in Los Alamos. For pion treatment planning, computerized tomography (CT) is used for three-dimensional localization of tumor and critical normal structures and for corrections for tissue inhomogeneities. Techniques that make anatomical information on CT scans directly transferable to therapy planning are described, as well as a technique for taking simulation and verification portal films using orthodiagraphic projection. Several requirements for direct use of CT scans in pion treatment planning are discussed. Finally, the effects of patient positioning on organ and tumor mobility and tissue inhomogeneity as shown by CT images are demonstrated.     

Comparison of intensity-modulated radiotherapy with conventional conformal radiotherapy for complex-shaped tumors

Purpose: Conformal and intensity-modulated radiotherapy (IMRT) plans for 9 patients were compared based on characterization of plan quality and effects on the oncology department.

Methods and Materials: These clinical cases, treated originally with conformal radiotherapy (CRT), required extraordinary effort to produce conformal treatment plans using nonmodulated, shaped noncoplanar fields with multileaf collimators (MLCs). IMRT plans created for comparison included rotational treatments with slit collimator, and fixed-field MLC treatments using equispaced coplanar, and noncoplanar fields. Plans were compared based upon target coverage, target conformality, dose homogeneity, monitor units (MU), user-interactive planning time, and treatment delivery time. The results were subjected to a statistical analysis.

Results: IMRT increased target coverage an average of 36% and conformality by 10%. Where dose escalation was a goal, IMRT increased mean dose by 4–6 Gy and target coverage by 19% with the same degree of conformality. Rotational IMRT was slightly superior to fixed-field IMRT. All IMRT techniques increased integral dose and target dose heterogeneity. IMRT planning times were significantly less, whereas MU increased significantly; estimated delivery times were similar.

Conclusion: IMRT techniques increase dose and target coverage while continuing to spare organs-at-risk, and can be delivered in a time frame comparable to other sophisticated techniques.     

High-speed magnetic resonance imaging for four-dimensional treatment planning of conformal radiotherapy of moving body tumors

PURPOSE: High-speed magnetic resonance imaging (MRI) was applied to the determination of the planning target volume (PTV) of moving hepatobiliary tumors. METHODS AND MATERIALS: Three moving tumors, including two metastatic hepatic tumors and one bile duct tumor, were examined using high-speed MRI and reference fiducial markers before external radiotherapy. Patients were examined for 30 seconds under conditions of normal breathing during the examination. The coordinates of the center of the tumor contours were shown on sagittal and coronal images displayed on the monitor. RESULTS: The maximum length of movement was 10.6 +/- 7.0 mm in a craniocaudal direction; 5.2 +/- 1.8 mm in a lateral direction; and 4.6 +/- 1.6 mm in a ventrodorsal direction. When the PTV was determined using MRI at exhalation phase with a 10-mm safety margin, clinical target volume (CTV) was not covered in 19% of all images in the 3 patients. With MRI at inhalation phase with a 10-mm safety margin, CTV was not covered in 36% of all images. CONCLUSION: Four-dimensional treatment planning using high speed MRI, and integrating time and spatial information, has the potential to determine the planning target volume of moving body tumors more precisely than does conventional CT planning.     

Failure of a 3D conformal boost to improve radiotherapy for nasopharyngeal carcinoma

Purpose: To determine whether the use of 3-dimensional (3D) boost for patients with nasopharynx cancer improves local control and reduces the risk of long-term complications.

Methods and Materials: From 1988 to 1998, 68 patients with nasopharynx cancer received conventional external beam therapy followed by a 3D boost. Disease characteristics of treated patients were as follows: WHO I histology 7%, WHO II 62%, WHO III 31%, clinical AJCC stage T1–2 45%, T3–4 55%, N0–1 63%, N2–3 37%, M0 100%. The median radiation dose was 70 Gy (68–75.6 Gy). Thirty-five patients (52%) received cisplatin-based chemotherapy. The median follow-up of surviving patients was 42 months (12–118 months).

Results: Five-year actuarial local control was 77%, regional control was 97%, progression-free survival was 56%, and overall survival was 58%. Stage was the only identifiable prognostic factor: 5-year progression-free survival was 65% for Stages I–III vs. 40% for Stage IV (p = 0.01). The incidence of Grade 3–4 complications was 25% and included hearing loss, trismus, dysphagia, chronic sinusitis, and cranial neuropathy. These results are comparable to outcomes reported with conventional radiation techniques for similarly staged patients.

Conclusion: The lack of a major benefit with the 3D boost may be related to the fact that CT planning was only used for a fraction of the total dose. We are now using intensity modulated radiation therapy to deliver the entire course of radiation. Intensity modulated radiation therapy achieves better conformal distributions than conventional 3D planning, allowing dose escalation and increased normal tissue sparing.