Direct data link between a CT scanner and a radiation treatment planning system.

A direct data link between a CT scanner and a radiation treatment planning system has been developed. The link transmits the data serially over a coaxial cable using the pseudo-paper-tape punch and reader (serial PIO) interfaces. The data transmission rate with error-check is approximately 25,000 8-bit bytes/s. This translates to about 7 s for transferring a CT scan with a 320-pixel diameter.     

Respiration-correlated treatment delivery using feedback-guided breath hold: a technical study

Respiratory motion causes movement of internal structures in the thorax and abdomen, making accurate delivery of radiation therapy to tumors in those areas a challenge. To reduce the uncertainties caused by this motion, we have developed feedback-guided breath hold (FGBH), a novel delivery technique in which radiation is delivered only during a voluntary breath hold that is sustained for as long as the patient feels comfortable. Here we present the technical aspects of FGBH, which involve (1) fabricating the hardware so the respiratory trace can be displayed to the patient, (2) assembling a delay box to be used as a breath-hold detector, and (3) performing quality control tests to ensure that FGBH can be delivered accurately and safely. A commercial respiratory tracking system that uses an external fiducial to monitor abdominal wall motion generates and displays the breathing trace and specific positions in the breathing cycle where a breath hold needs to occur. Hardware was developed to present this display to the patient in the treatment position. Patients view the presentation either on a liquid crystal display or through a pair of virtual reality goggles. Using the respiratory trace as a visual aid, the patient performs a breath hold so that the position representing the location of a fiducial is held within a specified gating window. A delay box was fabricated to differentiate between gating signals received during free breathing and those received during breath hold, allowing radiation delivery only when the fiducial was within the breath-hold gating window. A quality control analysis of the gating delay box and the integrated system was performed to ensure that all of the hardware and components were ready for clinical use.     

256层螺旋CT肾动脉成像的三维解剖学

目的:探讨256层螺旋CT对肾动脉的显示能力,研究肾动脉的三维影像学解剖.方法:对106例无肾相关疾病的患者行256层螺旋CT肾动脉造影检查,薄层获得原始图像,后处理使用容积再现(VR)、3D最大密度投影(3D-MIP)、薄层滑块最大密度投影(STS-MIP)、多平面重建(MPR)、曲面重建(CPR)等重建技术,分析肾动脉的空间解剖特征,比较不同重建技术对肾动脉的显示,特别是变异血管的显示.结果:106例均能清晰显示肾动脉的位置、起源、走向、分支及变异情况.共检出血管正常患者53例,左侧副肾动脉共21例,右侧副肾动脉16例,双侧副肾动脉9例,肾动脉过早分支7例.结论:256层CT血管造影三维成像能很好地显示肾动脉解剖学特征,为临床诊断和治疗提供依据.     

Acceptance testing computerized radiation therapy treatment planning systems: direct utilization of CT scan data

The availability of computerized radiation therapy treatment planning systems that utilize computed tomography (CT) scan data requires testing additional to that routinely needed for non-CT systems. These additional items include dimensioning verification, establishing CT number-to-tissue property conversions, verifying the accuracy of heterogeneity corrected dose predictions and autocontouring. One testing protocol is presented and sample results from an Atomic Energy of Canada Theraplan L system are presented.     

Modelling the dosimetric consequences of organ motion at CT imaging on radiotherapy treatment planning

Treatment planning algorithms usually assume that the correct or at least the mean organ position is derived from the CT imaging procedure, and that this position is reproduced throughout the treatment. In reality a mobile organ is unlikely to be in its exact mean position at the time of imaging, causing the treatment to be planned with an organ off-set from its assumed mean position. This introduces an extra 'CT uncertainty' into the treatment. A Monte Carlo (MC) model is used to simulate organ translations at imaging and evaluate the effect of this uncertainty (above the treatment delivery uncertainties) on the dose distribution. An underdose by 4 Gy in a 60 Gy treatment is calculated in the penumbral region of a single-field dose distribution as a result of the CT uncertainty. The effect is reduced to less then 0.5 Gy when the organ position at planning is derived as the average from multiple pretreatment CT scans. It is shown that a convolution method can be applied to predict the effect of CT uncertainty on the dose distribution for a patient population. Additionally, a variation kernel for a convolution method is derived that incorporates uncertainty at both imaging and treatment.     

A CT calibration method based on the polybinary tissue model for radiotherapy treatment planning

A method to establish the relationship between CT number and effective density for therapeutic radiations is proposed. We approximated body tissues to mixtures of muscle, air, fat and bone. Consequently, the relationship can be calibrated only with a CT scan of their substitutes, for which we chose water, air, ethanol and potassium phosphate solution, respectively. With simple and specific corrections for non-equivalencies of the substitutes, a calibration accuracy of 1% will be achieved. We tested the calibration method with some biological materials to verify that the proposed method would offer the accuracy, simplicity and specificity required for a standard in radiotherapy treatment planning, in particular with heavy charged particles.     

Simulations for inverse radiation therapy treatment planning using a dynamic MLC algorithm

The inverse radiation treatment planning model for a dynamic multileaf collimator (MLC) is used to find the optimal solution of planning problem. The model for dynamic MLC is explained in Tervo et al (2003 Appl. Math. Comput. 135 227-50). The advantage of this model is that it optimizes leaf velocity parameters directly. Our algorithm uses a gradient-based local optimization method. Two patient cases, prostate carcinoma and tonsilla carcinoma, are studied. Field arrangements are pre-selected and velocity parameters for MLC leaves are optimized to obtain the prescribed dose in the patient space. In both simulated cases, high dose distribution conforms the planning target volume well and organs-at-risk are saved in most parts. Simulations show that the model has its functionality in patient treatments, although it is still formal and needs further development.     

Telematics enabled virtual simulation system for radiation treatment planning

In this paper, GALENOS, a Telematics Enabled Virtual Simulation System for Radiation Treatment Planning (RTP) is described. The design architecture of GALENOS is in accordance with the dual aim of virtual simulation of RTP, i.e. to allow (a) delineation of target volume and critical organs, and (b) placement of irradiation fields. An important feature of GALENOS is the possibility for on-line tele-collaboration between health care professionals under a secure framework. The advantages of GALENOS include elimination of patient transfers between departments and health care institutions as well as availability of patient data at sites different than those of his/her physical presence.     

成人内听道底相关结构的多层螺旋CT解剖学观察

目的：应用64层MSCT观测成人内听道底及其相关的解剖结构,为临床应用提供影像解剖学依据。方法筛选2011年4—12月广东省人民医院采用64层MSCT扫描的乳突气化良好、无中耳或内耳病变且无眩晕等平衡功能障碍症状的40例共80耳成人CT资料进行回顾性分析。在MSCT图像上观测：横嵴,横嵴至前庭内侧骨壁的距离（ D1),面神经管迷路段、上前庭神经管、下前庭神经管和后壶腹神经管（单管)各管的长度、宽径,以及后壶腹神经管的内听道开口（单孔)至前庭内侧骨壁的距离（D2)。结果80耳的横嵴、面神经管迷路段、上前庭神经管、下前庭神经管和后壶腹神经管、单孔在横断位、冠状位及矢状位均能显示。其中横嵴局部解剖位置清晰、稳定,位于内听道底的中部,内侧缘自前内向后外走行,D1为（1．56±0．55)mm（0．55~2．67 mm)。面神经管迷路段长度（2．60±0．34)mm（1．54~3．27 mm),宽径（0．91±0．23)mm（0．50~1．58 mm);上前庭神经管长度（3．39±0．52) mm（2．50~5．06 mm),宽径（1．03±0．19)mm（0．74~1．62 mm);下前庭神经管长度（1．35±0．27) mm（0．74~2．17 mm),宽径（1．34±0．25)mm（0．85~2．34 mm);后壶腹神经管长度（3．88±0．84) mm （2．58~6．00 mm),宽径（0．63± 0．12) mm （0．42~0．98 mm)。 D2为（2．50±0．72)mm（1．37~5．01 mm)。结论64层螺旋CT能较好地显示位于内听道底的横嵴以及面神经管迷路段、前庭上神经、前庭下神经、后壶腹神经各骨管和单孔的走行及形态特征,为内耳疾病的诊断、鉴别诊断及术前评估提供有参考价值的信息。     

多层螺旋CT三维重建国人下颈椎椎弓根的临床解剖学意义

背景：因颈椎解剖结构复杂以及个体化差异较大,导致颈椎弓根钉置入内固定技术应用受到很大限制。 目的：应用螺旋CT三维重建国人的下颈椎椎弓根,并对重建图像进行测量评估。 方法：对60例需行颈椎CT扫描的患者C₃~C₇进行颈椎CT扫描,使用Syngo应用软件对原始CT图像进行所需面的重建,测量CT重建后的椎弓根各项指标。 结果与结论：颈椎绝大部分椎弓根峡部的宽度小于高度,男性高度和宽度C₄~C₇逐渐增大,女性则从C₃开始逐渐增大。C₃~C₇椎弓根侧块投射点到上关节突下缘的距离并无规律性,而到侧块外缘的距离从头端到尾端是不断增大的。男性与女性的椎弓根水平角在C₇均最小。结果提示,国人女性患者的C₃及C₄椎体行经颈椎椎弓根内固定应谨慎,大部分国人的C₅到C₇椎体是适合行椎弓根内固定的,但考虑到颈椎弓根个体的差异较大,内固定前颈椎弓根的CT扫描及重建后的评估是必要的。     

A methodology for automatic intensity-modulated radiation treatment planning for lung cancer

In intensity-modulated radiotherapy (IMRT), the quality of the treatment plan, which is highly dependent upon the treatment planner's level of experience, greatly affects the potential benefits of the radiotherapy (RT). Furthermore, the planning process is complicated and requires a great deal of iteration, and is often the most time-consuming aspect of the RT process. In this paper, we describe a methodology to automate the IMRT planning process in lung cancer cases, the goal being to improve the quality and consistency of treatment planning. This methodology (1) automatically sets beam angles based on a beam angle automation algorithm, (2) judiciously designs the planning structures, which were shown to be effective for all the lung cancer cases we studied, and (3) automatically adjusts the objectives of the objective function based on a parameter automation algorithm. We compared treatment plans created in this system (mdaccAutoPlan) based on the overall methodology with plans from a clinical trial of IMRT for lung cancer run at our institution. The 'autoplans' were consistently better, or no worse, than the plans produced by experienced medical dosimetrists in terms of tumor coverage and normal tissue sparing. We conclude that the mdaccAutoPlan system can potentially improve the quality and consistency of treatment planning for lung cancer.     

Monte Carlo based treatment planning for modulated electron beam radiation therapy

A Monte Carlo based treatment planning system for modulated electron radiation therapy (MERT) is presented. This new variation of intensity modulated radiation therapy (IMRT) utilizes an electron multileaf collimator (eMLC) to deliver non-uniform intensity maps at several electron energies. In this way, conformal dose distributions are delivered to irregular targets located a few centimetres below the surface while sparing deeper-lying normal anatomy. Planning for MERT begins with Monte Carlo generation of electron beamlets. Electrons are transported with proper in-air scattering and the dose is tallied in the phantom for each beamlet. An optimized beamlet plan may be calculated using inverse-planning methods. Step-and-shoot leaf sequences are generated for the intensity maps and dose distributions recalculated using Monte Carlo simulations. Here, scatter and leakage from the leaves are properly accounted for by transporting electrons through the eMLC geometry. The weights for the segments of the plan are re-optimized with the leaf positions fixed and bremsstrahlung leakage and electron scatter doses included. This optimization gives the final optimized plan. It is shown that a significant portion of the calculation time is spent transporting particles in the leaves. However, this is necessary since optimizing segment weights based on a model in which leaf transport is ignored results in an improperly optimized plan with overdosing of target and critical structures. A method of rapidly calculating the bremsstrahlung contribution is presented and shown to be an efficient solution to this problem. A homogeneous model target and a 2D breast plan are presented. The potential use of this tool in clinical planning is discussed.     

Sensitivity study for CT image use in Monte Carlo treatment planning

An important step in Monte Carlo treatment planning (MCTP), which is commonly performed uncritically, is segmentation of the patient CT data into a voxel phantom for dose calculation. In addition to assigning mass densities to voxels, as is done in conventional TP, this entails assigning media. Mis-assignment of media can potentially lead to significant dose errors in MCTP. In this work, a test phantom with exact-known composition was used to study CT segmentation errors and to quantify subsequent MCTP inaccuracies. For our test cases, we observed dose errors in some regions of up to 10% for 6 and 15 MV photons, more than 30% for an 18 MeV electron beam and more than 40% for 250 kVp photons. It is concluded that a careful CT calibration with a suitable phantom is essential. Generic calibrations and the use of commercial CT phantoms have to be critically assessed.     

Automatic segmentation of thoracic and pelvic CT images for radiotherapy planning using implicit anatomic knowledge and organ-specific segmentation strategies

Automatic segmentation of anatomical structures in medical images is a valuable tool for efficient computer-aided radiotherapy and surgery planning and an enabling technology for dynamic adaptive radiotherapy. This paper presents the design, algorithms and validation of new software for the automatic segmentation of CT images used for radiotherapy treatment planning. A coarse to fine approach is followed that consists of presegmentation, anatomic orientation and structure segmentation. No user input or a priori information about the image content is required. In presegmentation, the body outline, the bones and lung equivalent tissue are detected. Anatomic orientation recognizes the patient's position, orientation and gender and creates an elastic mapping of the slice positions to a reference scale. Structure segmentation is divided into localization, outlining and refinement, performed by procedures with implicit anatomic knowledge using standard image processing operations. The presented version of algorithms automatically segments the body outline and bones in any gender and patient position, the prostate, bladder and femoral heads for male pelvis in supine position, and the spinal canal, lungs, heart and trachea in supine position. The software was developed and tested on a collection of over 600 clinical radiotherapy planning CT stacks. In a qualitative validation on this test collection, anatomic orientation correctly detected gender, patient position and body region in 98% of the cases, a correct mapping was produced for 89% of thorax and 94% of pelvis cases. The average processing time for the entire segmentation of a CT stack was less than 1 min on a standard personal computer. Two independent retrospective studies were carried out for clinical validation. Study I was performed on 66 cases (30 pelvis, 36 thorax) with dosimetrists, study II on 52 cases (39 pelvis, 13 thorax) with radio-oncologists as experts. The experts rated the automatically produced structures on the scale 1-excellent (no corrections necessary, maximum time saving), 2-good (corrections necessary for up to 1/3 of slices), 3-acceptable (major corrections necessary, but still time saving), 4-not acceptable (manual redrawing more efficient, no time saving). A rating相似文献