Display of organs and isodoses as shaded 3-D objects for 3-D therapy planning

We have developed a technique that allows the user to assess and modify 3-D dose distributions in planning a treatment. Organs and superimposed isodoses can be displayed as shaded solid objects from any desired point of view. The graphic tools necessary are described in detail. Briefly, after the volumes of interest have been defined as contours taken from CT scans, the beam data can then be defined using the "beam's eye view" technique. Subsequently, the desired isodoses can be extracted from the three-dimensional dose matrices and displayed as a series of "barrel hoops" over the target volume. We have found this technique to be particularly useful for development of treatment plans where the spatial relationship of sensitive organs such as the spinal cord may change considerably within the treatment volume. Such a case is described in detail.     

3-D portal image analysis in clinical practice: an evaluation of 2-D and 3-D analysis techniques as applied to 30 prostate cancer patients

Purpose: To investigate the clinical importance and feasibility of a 3-D portal image analysis method in comparison with a standard 2-D portal image analysis method for pelvic irradiation techniques.

Methods and Materials: In this study, images of 30 patients who were treated for prostate cancer were used. A total of 837 imaged fields were analyzed by a single technologist, using automatic 2-D and 3-D techniques independently. Standard deviations (SDs) of the random, systematic, and overall variations, and the overall mean were calculated for the resulting data sets (2-D and 3-D), in the three principal directions (left–right [L-R], cranial–caudal [C-C], anterior–posterior [A-P]). The 3-D analysis included rotations as well. For the translational differences between the three data sets, the overall SD and overall mean were computed. The influence of out-of-plane rotations on the 2-D registration accuracy was determined by analyzing the difference between the 2-D and 3-D translation data as function of rotations. To assess the reliability of the 2-D and 3-D methods, the number of times the automatic match was manually adjusted was counted. Finally, an estimate of the workload was made.

Results: The SDs of the random and systematic components of the rotations around the three orthogonal axes were 1.1 (L-R), 0.6 (C-C), 0.5 (A-P) and 0.9 (L-R), 0.6 (C-C), 0.8 (A-P) degrees, respectively. The overall mean rotation around the L-R axis was 0.7°, which deviated significantly from zero. Translational setup errors were comparable for 2-D and 3-D analysis (ranging from 1.4 to 2.2 mm SD and from 1.5 to 2.5 mm SD, respectively). The variation of the difference between the 2-D and 3-D translation data increased from 1.1 mm (SD) for zero rotations to 2.7 mm (SD) for out-of-plane rotations of 3°, due to a reduced 2-D registration accuracy for large rotations. The number of times the analysis was not considered acceptable and was manually adjusted was 44% for the 2-D analysis, and 6% for the 3-D analysis.

Conclusion: True 3-D analysis of setup errors for a group of 30 patients with prostate cancer demonstrated that setup rotations are rather small. The deformation of the projected anatomy in portal images caused by out-of-plane rotations leads to a reduced 2-D registration accuracy. For rotations larger than 3° this effect can be quite pronounced, making 3-D registration the preferred method. Furthermore, the automatic 3-D registration has a higher success rate, most likely because this technique uses more information compared to the 2-D method.     

Testing a 3-D radiation therapy planning program

This report describes a systematic effort to test all functions of a large 3-D radiation therapy planning program, including graphics and user interaction. Previous studies in quality assurance for radiation therapy programs do not adequately address the problem of programming errors. They compare dose estimates calculated by planning programs to actual doses measured in phantoms, so they cannot distinguish programming errors from measurement errors or physical unsoundness of the beam model. Moreover, they fail to exercise graphics and user interaction functions. This report describes a different methodology: test cases are derived from the program specification, results are calculated by an independent technique, and compared to program output. Derivation of test cases is described in detail. Effectiveness of testing is assessed by reporting the number of errors revealed by testing and comparing to the number of errors discovered during routine use in five successive program versions. The size of the test set is related to the total program size, and the effort devoted to deriving and performing tests is compared to the total program development effort. We conclude that systematic testing can reveal errors that are not found by informal testing, routine program use, or comparison with measurements. However, additional errors remain that are only discovered during use. This study suggests that a typical large planning system may include more than 100 errors when it is released for clinical use. Methods for increasing testing effectiveness are recommended.     

立体定向放射治疗胸部肿瘤初步结果

目的：探讨立体定向放射治疗在胸部肿瘤治疗中的应用。方法：自1999年9月--2002年8月，对36例经病理证实的胸部肿瘤进行了立体定向放射治疗。其中原发性肺癌22例，转移性肺癌12例，纵隔肿瘤2例。其中鳞癌16例，腺癌15例，小细胞癌2例，胚胎性癌1例，胸腺瘤1例，软组织肉瘤1例。原发性肿瘤放疗先采用普通外照射50Gy／25次／5周，结束后即行立体定向放射治疗，对于不规则形病灶使用多叶光栅，球形病灶采用圆形限光筒。5-6个共面或非共面野，每次4Gy，每周照射3次，共4-5次。转移性肿瘤单纯立体定向放射治疗，1-4个拉弧照射，每次4Gy，每周3次，共7-10次。立体定向放疗时肿瘤体积为1．85cm^3至104．61cm^3(中位体积24．96cm^3)。结果：治疗结束后2个月拍摄胸部CT片进行疗效评价。可评价疗效的34例中，CR13例，PR14例，NC5例，PD2例。中位随访时间为24个月。一年和二年生存率分别为74.1％和38．4％。毒副反应主要为放射性肺损伤。其中急性放射性肺炎1级17例，2级10例，3级1例，5级2例(该2例肿瘤体积均超过60cm^3且为非共面照射)。晚期放射性肺纤维化1级20例，2级8例。结论：立体定向放射治疗作为普通外照射的补充在胸部肿瘤的治疗中近期疗效较好，远期疗效有待进一步观察。但要注意照射技术，照射体积不宜过大，适当调整非共面照射角度，避免正常肺组织的受照容积过大。     

PET-CT: evolving role in 3-D radiation therapy

Traditional imaging techniques, such as computed tomography (CT), have high spatial resolution for changes in the anatomy or structure of organs, but are not very useful for detecting early biochemical changes. Conversely, positron emission tomography (PET) relies on changes in molecular biology to identify the earliest stages of disease but, if used alone, has sub-optimal spatial delineation. However, computer-assisted fused-image and/or single-machine integrated PET-CT can show early biochemical changes with improved anatomic resolution, often before there is any structural change. This approach enables the clinician to view and assess the patient's body from a biochemical perspective. In an era of rapidly evolving 3D conformal radiation treatment, accurate target delineation is a crucial factor in optimization of clinical results. This paper reviews some of the basic-science underpinnings of PET-CT, and highlights some important findings in the early clinical work thus far performed.     

3-D Visualization of Medical Images with Arbitrary Sections

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Dose Specification with 3-D Dose Planning (Icru 'Level 3')

The availability of constantly more sophisticated algorithms and methods for dose planning (denoted 'level 3' procedures by the ICRU) makes it possible to use accordingly more complex treatment techniques. Such procedures have the potential of reducing irradiation of organs at risk and other healthy tissue. However, they suffer from a substantially more difficult set-up of the patient and verification of the treatment. This will introduce additional sources of error, systematic as well as random, which will be of importance for dose reporting. The purpose of this paper is to point out some of these problems and to suggest a method for reporting which is the least sensitive to these 'new' sources of error.     

In vitro accumulation and permeation of hypericin and lipophilic analogues in 2-D and 3-D cellular systems

Previous studies have shown that hypericin is an excellent diagnostic tool for the fluorescence detection of carcinoma in situ in the human bladder. The present work was performed to get a better insight into the mechanism of cellular uptake of hypericin (HYP) using RT-112 human papillary TCC cells of the bladder. Using lipophilic hypericin acid amide derivatives like hypericin acid hexylamide (AM6), hypericin acid octylamide (AM8) and hypericin acid dodecylamide (AM12), the effect of increased lipophilicity on the binding to serum proteins was investigated, as well as the cellular accumulation and permeation, both in 2-D and 3-D cell conditions. Density-gradient ultracentrifugation of the compounds pre-incubated with fetal bovine serum (FBS) showed that HYP and to a lesser extent AM6 predominantly bind to LDL, whereas AM8 and especially AM12 preferably associate with HDL. The cellular accumulation of the compounds did not significantly differ when LDL or AcLDL was supplemented to medium, and with all compounds the highest uptake could be observed in case of medium without supplements. Using medium without supplements it was further observed that the compounds with the highest lipophilicity accumulated substantially less in RT-112 cells. We further found a significant difference in the intracellular concentration of AM8 and AM12 when LDL or FBS was supplemented to MEM, but not in case of HYP and AM6. Of particular interest, AM8 and especially AM12 showed enhanced intraspheroidal permeation in the presence of FBS. It is believed that the relative stronger binding to HDL reduces the intracellular accumulation, as seen in the 2-D conditions, and therefore increases the probability of paracellular transport in a 3-D multicellular system by passive diffusion. In conclusion the data suggest that the amount of free hypericin or its lipophilic congener determines the extent of intracellular accumulation. This concentration is both determined and limited by binding to different lipoproteins present in the medium, and by the formation of stable homoaggregates. The findings further highlight AM8 and AM12 as compounds better tailored for paracellular transport than HYP itself and therefore as potentially very interesting diagnostic tools for TCC lesions in the bladder.     

3-D radiation therapy treatment planning: overview and assessment

A 3-D treatment planning system is one that can represent all radiation therapy treatment machine motions, and which can calculate the dose at any point in the patient treatment volume. As a corollary to these two requirements, a 3-D planning system must also be able to display 3-D plan geometry and doses in some useful way. This article reviews three visible aspects of 3-D planning systems: graphic displays, dose computation methods, and ease of use. It also discusses a less visible, but no less important, aspect: the underlying software engineering. Although 3-D planning systems first appeared in research institutions more than a decade ago, and potential benefits have been demonstrated, they are used only rarely in routine clinical practice. This review concludes that adequate displays and computation techniques are now available, but improved packaging, engineering, and ease of use are required before 3-D planning will be practiced widely.     

Transcolonic retrograde ureteric catheterization assisted by 3-D computed tomography

A 42-year-old woman had bladder exstrophy at birth, treated by ureterocolic anastomosis of her single kidney. She suffered recurrent hyperammonaemia, leading to comas, but refused an ileal conduit. During her most recent coma, it was decided to divert her urine to test whether this would reduce hyperammonaemia: this was accomplished by transcolonic retrograde catheterization of the ureter. This was only possible after computed tomography ureterography to show the ureterocolic anastomosis.     

Progress in 3-D treatment planning for photon beam therapy

The purpose of this report is to study the feasibility of improving dose distributions using non-coplanar photon beams from a linear accelerator. Non-coplanar beams may enter the patient in any arbitrary configuration. This type of treatment technique requires a three-dimensional (3-D) planning system. Clinical examples are used to illustrate the general problems in 3-D treatment planning, and the potential improvement over coplanar beam treatments. Features of a treatment planning system for 3-D planning are discussed.     

Prognostic factors of myelodysplastic syndromes--a simplified 3-D scoring system

From 1 January 1982 to 31 December 1986 in five haematological centers of the west of France (Rennes, Rouen, Nantes, Tours and Angers), we have collected 503 cases of myelodysplastic syndrome (MDS). These cases were classified by FAB recommendation as followed: 85 refractory anemia with ring sideroblasts (RARS); 273 refractory anemia in which 86 were without blasts (RA), 153 were with excess of blasts (RAEB) and 34 were with excess of blasts and in transformation (RAEB-t); 111 chronic myelomonocytic leukaemia (CMML); and 34 cases with borderline features. The point date for statistical study was 31 December 1988, and the scoring method of Bournemouth was applied to compare with our findings (62% resulted in death, 18% in leukemic transformation). It was demonstrated that haemoglobin, platelets, and bone marrow-blasts are the best factors to predict survival or leukaemic transformation (LT). But peripheral neutrophils don't affect the survival time excepted when lower than 500 microliters (13 months vs 19.6 months). A scoring system based on haemoglobin (Hb), platelets (Pl), and bone marrow blasts (BMB) may be represented in a three-dimensional space and is a good tool to know the own value of each parameter. This 3-D system shows that BMB and Pl are the most important factors and are correlated with survival, per cent of death, and LT (p less than 0.0001). The LT is observed in 18% of the whole population. RAEB and RAEB-t progress in AML2 (14.6%) or AML4 (1.4%), and CMML progress in AML2 (8.1%) or AML4 (11.7%). We observed that monocytes are not good parameters to predict the type of leukemic transformation. Furthermore, survival of RA treated with Ara-C(ld) or not treated was similar.     

三维适形放射治疗常规外照射后复发的食管癌

目的：研究三维适形放射治疗常规放射治疗后复发的食管癌可行性。方法：20例食管癌放射治疗后复发病例，实施适形放射治疗，照射剂量为45～60Gy，3．0Gy／次，1次／d，5d／周。结果：急性放射性食管炎发生率1～2级65％(13／20)、3级35％(7／20)；急性放射性气管炎发生率1～2级35％(7／20)、3级5％(1／20)；骨髓抑制发生率1～2级50％(10／20)、3级0％(0／20)；总有效率为100％，其中完全缓解(CR)80％(16／20)，部分缓解(PR)20％(4／20)。1、2年生存率分别为69．2％(9／13)、42．9％(3／7)。结论：三维适形放射治疗常规外照射后复发的食管癌有较好的近期疗效，早期并发症较低，能为患耐受，晚期并发症的发生率及远期疗效有待进一步观察。     

Arbitrary oblique image sections for 3-D radiation treatment planning

Methods for selecting and computing arbitrary image sections for displaying anatomic and isodose information for three-dimensional treatment planning are investigated. Selection of the desired plane may be made by defining a plane that is perpendicular to an existing image section (called the base image) and passing through a line on the base image. Alternatively, the anatomic structures displayed perspectively in three dimensions as a series of contours that can be rotated and translated may be used to define an arbitrary plane for image reconstruction. The viewing screen is considered to be the plane of interest. As a typical three-dimensional image of 30 to 60 sections requires considerable computer storage (on the order of 25 megabytes), a reconstruction algorithm may need extensive memory space or CPU and disk I/O time. Of the schemes examined, we believe the following is the most efficient. One pair of images is read from the disk at a time in sequence and intersections of the rows of the cutting plane with the box formed by the consecutive images are computed. Pixel values of all points between the given images are computed by interpolation. Special cases, such as the cutting plane being parallel to or coincident with an existing image, must be considered separately.     

3D dose reconstruction for narrow beams using ion chamber array measurements

3D dose reconstruction is a verification of the delivered absorbed dose. Our aim was to describe and evaluate a 3D dose reconstruction method applied to phantoms in the context of narrow beams. A solid water phantom and a phantom containing a bone-equivalent material were irradiated on a 6 MV linac. The transmitted dose was measured by using one array of a 2D ion chamber detector. The dose reconstruction was obtained by an iterative algorithm. A phantom set-up error and organ interfraction motion were simulated to test the algorithm sensitivity.In all configurations convergence was obtained within three iterations. A local reconstructed dose agreement of at least 3% / 3 mm with respect to the planned dose was obtained, except in a few points of the penumbra. The reconstructed primary fluences were consistent with the planned ones, which validates the whole reconstruction process. The results validate our method in a simple geometry and for narrow beams. The method is sensitive to a set-up error of a heterogeneous phantom and interfraction heterogeneous organ motion.     

半像素错位技术在三维CT重建中的应用

本文介绍了一种基于半像素错位的多幅锥束投影数据重建高分辨率投影数据的技术,利用在水平和垂直方向上进行半像素错位的方法提高了锥束投影数据的分辨率,并给出了具体的实现方法,同时对重建后的投影数据用FDK方法进行重建,实验结果表明,重建出来的三维物体的质量在水平和垂直方向都获得了的提高,而且还有抑制噪声的效果。     

Magnetic Resonance Imaging of Aortic Aneurysms with 3-D Image Reconstruction

A programme was written to detect flow in a sequence of MR images and to construct 3-D vessel maps from the detected flow regions. Reduction in first echo intensity and prolongation of calculated T2 value were used as flow-detection criteria. The programme was used to image the aorta in 6 patients with abdominal aortic aneurysm and 5 patients with aortic dissection. Results were compared with contrast angiography in 9 cases and X-ray CT in 2. The images obtained by the two techniques were comparable in 9 cases. In 2 cases of aortic dissection, where flow in the false lumen was slow, the false lumen could not be demonstrated by angiography, but was clearly seen in the reconstructed MR images.     

希罗达联合三维适形放疗在肝癌中的应用

 原发性肝癌是我国常见的恶性肿瘤之一，首选的治疗手段是手术切除病灶，但大多数患者就诊时已经属于中晚期，丧失手术切除机会。非手术治疗当中，三维适形放疗已广泛应用于治疗中晚期肝癌。肝癌单纯适形放疗疗效较差，我院从2003年1月~2005年6月始用希罗达联合适形放疗治疗35例原发性肝癌患者，现将治疗疗效报告如下：