Contribution of imaging in radiotherapy planning in uterine cervix cancers]

External irradiation and brachytherapy are curative in the treatment of carcinoma of the cervix. The aim of radiotherapy is to optimize the irradiation of the target volume and to reduce the dose to critical organs. The use of imaging (computed tomography and magnetic resonance imaging added to clinical findings and standard guidelines) are studied in the treatment planning of external irradiation and brachytherapy in carcinoma of the cervix. Imaging allows an individualized and conformal treatment planning.     

Integration of multimodality imaging data for radiotherapy treatment planning

This paper describes computational techniques to permit the quantitative integration of magnetic resonance (MR), positron emission tomography (PET), and x-ray computed tomography (CT) imaging data sets. These methods are used to incorporate unique diagnostic information provided by PET and MR imaging into CT-based treatment planning for radiotherapy of intracranial tumors and vascular malformations. Integration of information from the different imaging modalities is treated as a two-step process. The first step is to determine the set of geometric parameters relating the coordinates of two imaging data sets. No universal method for determining these parameters is appropriate because of the diversity of contemporary imaging methods and data formats. Most situations can be handled by one of the four different techniques described. These four methods make use of specific geometric objects contained in the two data sets to determine the parameters. These objects are: (a) anatomical and/or fiducial points, (b) attached line markers, (c) anatomical surfaces, and (d) outlines of anatomical structures. The second step involves using the derived transformation to transfer outlines of treatment volumes and/or anatomical structures drawn on the images of one imaging study to the images of another study, usually the treatment planning CT. Solid modelling and image processing techniques have been adapted and developed further to accomplish this task. Clinical examples and phantom studies are presented which verify the different aspects of these techniques and demonstrate the accuracy with which they can be applied. Clinical use of these techniques for treatment planning has resulted in improvements in localization of treatment volumes and critical structures in the brain. These improvements have allowed greater sparing of normal tissues and more precise delivery of energy to the desired irradiation volume. It is believed that these improvements will have a positive impact on the outcome of radiation therapy.     

Functional and molecular image guidance in radiotherapy treatment planning optimization

Functional and molecular imaging techniques are increasingly being developed and used to quantitatively map the spatial distribution of parameters, such as metabolism, proliferation, hypoxia, perfusion, and ventilation, onto anatomically imaged normal organs and tumor. In radiotherapy optimization, these imaging modalities offer the promise of increased dose sparing to high-functioning subregions of normal organs or dose escalation to selected subregions of the tumor as well as the potential to adapt radiotherapy to functional changes that occur during the course of treatment. The practical use of functional/molecular imaging in radiotherapy optimization must take into cautious consideration several factors whose influences are still not clearly quantified or well understood including patient positioning differences between the planning computed tomography and functional/molecular imaging sessions, image reconstruction parameters and techniques, image registration, target/normal organ functional segmentation, the relationship governing the dose escalation/sparing warranted by the functional/molecular image intensity map, and radiotherapy-induced changes in the image intensity map over the course of treatment. The clinical benefit of functional/molecular image guidance in the form of improved local control or decreased normal organ toxicity has yet to be shown and awaits prospective clinical trials addressing this issue.     

The NUKDOS software for treatment planning in molecular radiotherapy

The aim of this work was the development of a software tool for treatment planning prior to molecular radiotherapy, which comprises all functionality to objectively determine the activity to administer and the pertaining absorbed doses (including the corresponding error) based on a series of gamma camera images and one SPECT/CT or probe data. NUKDOS was developed in MATLAB. The workflow is based on the MIRD formalismFor determination of the tissue or organ pharmacokinetics, gamma camera images as well as probe, urine, serum and blood activity data can be processed. To estimate the time-integrated activity coefficients (TIAC), sums of exponentials are fitted to the time activity data and integrated analytically. To obtain the TIAC on the voxel level, the voxel activity distribution from the quantitative 3D SPECT/CT (or PET/CT) is used for scaling and weighting the TIAC derived from the 2D organ data. The voxel S-values are automatically calculated based on the voxel-size of the image and the therapeutic nuclide (⁹⁰Y, ¹³¹I or ¹⁷⁷Lu). The absorbed dose coefficients are computed by convolution of the voxel TIAC and the voxel S-values. The activity to administer and the pertaining absorbed doses are determined by entering the absorbed dose for the organ at risk. The overall error of the calculated absorbed doses is determined by Gaussian error propagation.NUKDOS was tested for the operation systems Windows^® 7 (64 Bit) and 8 (64 Bit). The results of each working step were compared to commercially available (SAAMII, OLINDA/EXM) and in-house (UlmDOS) software. The application of the software is demonstrated using examples form peptide receptor radionuclide therapy (PRRT) and from radioiodine therapy of benign thyroid diseases. For the example from PRRT, the calculated activity to administer differed by 4% comparing NUKDOS and the final result using UlmDos, SAAMII and OLINDA/EXM sequentially. The absorbed dose for the spleen and tumour differed by 7% and 8%, respectively. The results from the example from radioiodine therapy of benign thyroid diseases and the example given in the latest corresponding SOP were identical. The implemented, objective methods facilitate accurate and reproducible results. The software is freely available.     

Treatment planning in molecular radiotherapy

In molecular radiotherapy a radionuclide or a radioactively labelled pharmaceutical is administered to the patient. Treatment planning therefore comprises the determination of activity to administer. This administered activity should maximize tumour cell sterilization while minimizing normal tissue damage. In this work we present different approaches that are frequently used for determining the suitable activity. These approaches may be cohort- based as in chemotherapy, or patient-specific using dosimetry based on individual biokinetics. The approaches are different with respect to the input complexity, the corresponding costs and – in consequence – the quality of the therapy. In addition, a general scheme for data collection and analysis is proposed. To develop an effective and safe treatment, elaborate data need to be obtained. The main challenges, however, are collecting these complex data and analyse them properly.     

Contribution of PET imaging to radiotherapy planning and monitoring in glioma patients - a report of the PET/RANO group

The management of patients with glioma usually requires multimodality treatment including surgery, radiotherapy, and systemic therapy. Accurate neuroimaging plays a central role for radiotherapy planning and follow-up after radiotherapy completion. In order to maximize the radiation dose to the tumor and to minimize toxic effects on the surrounding brain parenchyma, reliable identification of tumor extent and target volume delineation is crucial. The use of positron emission tomography (PET) for radiotherapy planning and monitoring in gliomas has gained considerable interest over the last several years, but Class I data are not yet available. Furthermore, PET has been used after radiotherapy for response assessment and to distinguish tumor progression from pseudoprogression or radiation necrosis. Here, the Response Assessment in Neuro-Oncology (RANO) working group provides a summary of the literature and recommendations for the use of PET imaging for radiotherapy of patients with glioma based on published studies, constituting levels 1-3 evidence according to the Oxford Centre for Evidence-based Medicine.     

应用超全向楔形板概念设计治疗计划

目的　运用超全向楔形板概念 ,结合计划系统优化照射野权重的功能 ,来同时优化照射野权重、楔形板角度和方向。方法　分 5个步骤进行 :第一步是根据超全向楔形板概念 ,在每个照射野方向布置 4个 6 0°楔形板照射野 ,楔形方向分别是“LEFT”、“IN”、“RIGHT”、“OUT” ;第二步是根据每个计划系统优化权重功能的特点 ,定义优化问题 (包括优化的目标函数和约束条件 ) ;第三步是启动优化过程 ;第四步是当优化问题有解 ,并且评价优化结果满意时 ,进到第五步 ,否则回到第二步修改优化条件 ;第五步是将超全向楔形板的照射野变换为全向楔形板的照射野 ,以减少照射野数目 ,继而减少治疗时间。结果　将该方法运用到 1例食管癌和 1例脑瘤。与手工计划相比 ,计划靶区剂量更均匀 ,危及器官受照剂量更低。结论　对于复杂布野情况 ,运用该方法不仅可以提高计划质量 ,而且可以缩短计划设计时间。     

Recent advances in radiotherapy treatment planning

Radiation treatment planning is currently in a state of rapid change. Dissatisfaction with past planning technology stems from the growing realization that: (1) Increases in the local regional tumor control rate will increase the cure rate in many malignancies. (2) Even at the best treatment centers geometric tumor misses are commonplace. (3) Traditional constraints on treatment techniques, originally imposed for simplicity and reproducibility, are no longer necessary, and can result in suboptimal treatment. (4) Treatment plans judged "optimal" in two dimensions may be far from optimal when viewed over the entire treatment volume. (5) Lack of treatment reproducibility is also commonplace, and can be demonstrated to adversely affect treatment outcome. On the positive side, recent developments in computer graphics, image processing, radiation physics, and radiation biology are now making it possible to define, design, and deliver sophisticated 3D radiation treatments. However, because many of these technologies are being developed for other disciplines, their applicability to radiation therapy treatment planning is not widely appreciated. We outline the current status and new developments in radiation therapy treatment planning.     

Contribution of respiratory gating techniques for optimization of breast cancer radiotherapy

A comparative, nonrandomized, multicenter, and prospective analysis were performed between April 2004 and June 2008 in 20 French centers in order to compare clinical aspects of respiratory-gated conformal radiotherapy (RGRT) during breast cancer irradiation versus conventional conformal radiotherapy. The final results based on 233 evaluable patients at 48 months confirm the feasibility and good reproducibility of the RGRT systems. The main results demonstrated a marked reduction of dosimetric parameters predictive of lungs and cardiac toxicities in the RGRT group; especially the dose delivered to the heart during irradiation of the left breast; mostly observed with deep inspiration breath-hold 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.     

Semi-automated radiotherapy treatment planning with a mathematical model to satisfy treatment goals

Iterative algorithms can provide a feasible solution, if any exists, to specified treatment goals. Our model subdivides both the patient's cross section into a fine grid of points and the radiation beam into a set of "pencil" rays. The anatomy, treatment machine parameters, dose limits and homogeneity, are all defined. This process of subdivision leads to a large system of linear inequalities with a solution that provides a radiation intensity distribution that will deliver a prescribed dose distribution. The clinical results from two different algorithms will be presented and contrasted. Once the anatomy, treatment, and machine parameters have been entered, the computerized algorithms yield an answer in several minutes. The Cimmino algorithm also allows "weights" or priority assignments of the treatment goals. The resulting solution is biased towards fulfilling the specified doses for the anatomic regions which were given greater weight. It is desirable to have a systematic search of possible treatment alternatives in complex clinical situations, including 3-dimensional radiation therapy treatment planning (RTTP). Our method has been applied to 2-D RTTP, but is equally applicable to 3-D RTTP with minor modifications.     

Diffusion tensor imaging: possible implications for radiotherapy treatment planning of patients with high-grade glioma

AimsRadiotherapy treatment planning for high-grade gliomas (HGG) is hampered by the inability to image peri-tumoural white-matter infiltration. Diffusion tensor imaging (DTI) is an imaging technique that seems to show white-matter abnormalities resulting from tumour infiltration that cannot be visualised by conventional computed tomography or magnetic resonance imaging (MRI). We propose a new term, the image-based high-risk volume (IHV) for such abnormalities, which are distinct from the gross-tumour volume (GTV). For IHV based on DTI, we use the term IHV_DTI. This study assesses the value of DTI for the individualisation of radiotherapy treatment planning for patients with HGG.MethodsSeven patients with biopsy-proven HGG were included in a theoretical planning exercise, comparing standard planning techniques with individualised plans based on DTI. Standard plans were generated using a 2.5 cm clinical target volume (CTV) margin added to the GTV. For DTI-based plans, the CTV was generated by adding a 1 cm margin to the IHV_DTI. Estimates of normal tissue complication probability (NTCP) were calculated and used to estimate the level of dose escalation that could be achieved using the DTI-based plans.ResultsThe use of DTI resulted in non-uniform margins being added to the GTV to encompass areas at high risk of tumour involvement, but, in six out of seven cases, the IHV_DTI was encapsulated by the standard CTV margin. In all cases, DTI could be used to reduce the size of the planning-target volume (PTV) (mean 35%, range 18–46%), resulting in escalated doses (mean 67 Gy, range 64–74 Gy), with NTCP levels that matched the conventional treatment plans.ConclusionDTI can be used to individualise radiotherapy target volumes, and reduction in the CTV permits modest dose escalation without an increase in NTCP. DTI may also be helpful in stratifying patients according to the degree of white-matter infiltration.     

Simulation techniques in hyperthermia treatment planning

Abstract

Clinical trials have shown that hyperthermia (HT), i.e. an increase of tissue temperature to 39–44?°C, significantly enhance radiotherapy and chemotherapy effectiveness [1]. Driven by the developments in computational techniques and computing power, personalised hyperthermia treatment planning (HTP) has matured and has become a powerful tool for optimising treatment quality. Electromagnetic, ultrasound, and thermal simulations using realistic clinical set-ups are now being performed to achieve patient-specific treatment optimisation. In addition, extensive studies aimed to properly implement novel HT tools and techniques, and to assess the quality of HT, are becoming more common. In this paper, we review the simulation tools and techniques developed for clinical hyperthermia, and evaluate their current status on the path from ‘model’ to ‘clinic’. In addition, we illustrate the major techniques employed for validation and optimisation. HTP has become an essential tool for improvement, control, and assessment of HT treatment quality. As such, it plays a pivotal role in the quest to establish HT as an efficacious addition to multi-modality treatment of cancer.     

Physical and methodological aspects of multimodality imaging and principles of treatment planning in 3D conformal radiotherapy]

The recent evolutions of the imaging modalities, the dose calculation models, the linear accelerators and the portal imaging permit to improve the quality of the conformal radiation therapy treatment planning. With DICOM protocols, the acquired imaging data coming from different modalities are treated by performant image fusion algorithms and yield more precise target volumes and organs at risk. The transformation of the clinical target volumes (CTV) to planning target volumes (PTV) can be realised using advanced probabilistic techniques based on clinical experience. The treatment plans evaluation is based on the dose volume histograms. Their precision and clinical relevance are improved by the multi-modality imaging and the advanced dose calculation models. The introduction of the inverse planning systems permitting to realise modulated intensity radiation therapy generates highly conformal dose distributions. All the previously cited complex techniques require the application of rigorous quality assurance programs.