CT simulator: a new 3-D planning and simulating system for radiotherapy: Part 1. Description of system

A real time CT-linked 3-D treatment planning system, called a CT simulator, has been developed. The basic system consists of a CT scanner, a multi-image display component, a treatment planning device with real time visual optimization, and a laser beam projecting component. All the components are connected on line. The system can be conveniently used for 3-D planning and simulation for radiation therapy within a reasonably short period of time.     

Real-time qualitative MR monitoring of microwave ablation in ex vivo livers

Purpose: Computed tomography (CT) and ultrasound-guided microwave ablations (MWA) are part of the established treatment of liver tumours. In spite of its potential advantages, magnetic resonance (MR) monitoring of MWA did not enter clinical practice because of the lack of compatible devices. The purpose of the current study was to prove the feasibility of real-time qualitative MR monitoring using a new MR-compatible MWA device.

Material and methods: We performed 27 MWA experiments with different durations (5, 10 and 15?min) on an ex vivo bovine liver model using a MR-compatible MWA device. We compared the diameters of the ablation zone as depicted on three T1-based sequences to those of the macroscopic specimen. The volume and the sphericity index of the macroscopic ablation area were calculated in order to characterise the device. Ablation pattern and artefacts on the three sequences were also taken into account.

Results: We obtained high-quality real-time images using all three sequences. The diameters as depicted on the MR sequences slightly overestimated the macroscopic ablation area but correlated significantly in all cases (p?r?=?0.96) and long-axis diameter (r?=?0.87), whereas starVIBE (r?=?0.85; r?=?0.72) and FLASH (r?=?0.75; r?=?0.84) correlated slightly less. Significantly more severe noise artefacts were observed on starVIBE compared to FLASH and VIBE sequences (p?Conclusion: The current ex vivo liver model experiment suggests that real-time qualitative MR monitoring of MWA is feasible. Further research using in vivo and human models are recommended.     

结直肠癌肝转移患者经微波消融联合肝动脉栓塞化疗的效果和肝功能变化情况

目的探讨微波消融术(MWA)联合肝动脉化疗栓塞术(TACE)治疗结直肠癌肝转移中的临床疗效及其患者肝功能变化、生存情况以及生活质量评价。方法回顾性分析80例结直肠癌肝转移患者的临床相关资料,其中有38例单独行肝动脉化疗栓塞术治疗,为TACE组;其他42例行微波消融联合肝动脉栓塞化疗进行治疗,为MWA+TACE组。对2组的临床疗效、患者肝功能变化、生存情况以及生活质量评价数据进行整理分析。结果 TACE组和MWA+TACE组的临床有效率分别是39.5%和76.2%,MWA+TACE组患者的临床疗效显著优于TACE组患者(χ~2=11.098,P≈0.001)。2组患者的血清白蛋白、谷丙转氨酶、总胆红素含量等肝功能各项指标不存在统计学差异(P>0.05)。MWA+TACE组患者的2年、3年生存率显著高于TACE组(P<0.05)。在治疗6个月后,MWA+TACE组患者的生理状况、功能状况、情感状况、家庭/社会状况均显著高于TACE组患者(P<0.05);在总体评分上,MWA+TACE组患者显著优于TACE组(P<0.05)。结论微波消融联合肝动脉栓塞化疗治疗结肠癌肝转移有非常显著的效果,相对于单独化疗,能够延长患者的生存时间以及提高其生活质量,且对肝功能不会造成损害。     

Assessment of intraoperative 3D imaging alternatives for IOERT dose estimation

Intraoperative electron radiation therapy (IOERT) involves irradiation of an unresected tumour or a post-resection tumour bed. The dose distribution is calculated from a preoperative computed tomography (CT) study acquired using a CT simulator. However, differences between the actual IOERT field and that calculated from the preoperative study arise as a result of patient position, surgical access, tumour resection and the IOERT set-up. Intraoperative CT imaging may then enable a more accurate estimation of dose distribution. In this study, we evaluated three kilovoltage (kV) CT scanners with the ability to acquire intraoperative images. Our findings indicate that current IOERT plans may be improved using data based on actual anatomical conditions during radiation. The systems studied were two portable systems (“O-arm”, a cone-beam CT [CBCT] system, and “BodyTom”, a multislice CT [MSCT] system) and one CBCT integrated in a conventional linear accelerator (LINAC) (“TrueBeam”). TrueBeam and BodyTom showed good results, as the gamma pass rates of their dose distributions compared to the gold standard (dose distributions calculated from images acquired with a CT simulator) were above 97% in most cases. The O-arm yielded a lower percentage of voxels fulfilling gamma criteria owing to its reduced field of view (which left it prone to truncation artefacts). Our results show that the images acquired using a portable CT or even a LINAC with on-board kV CBCT could be used to estimate the dose of IOERT and improve the possibility to evaluate and register the treatment administered to the patient.     

Three-dimensional motion analysis of an improved head immobilization system for simulation, CT, MRI, and PET imaging

A mask/marker immobilization system for the routine radiation therapy treatment of head and neck disease is described, utilizing a commercially available thermoplastic mesh, indexed and mounted to a rigid frame attached to the therapy couch. Designed to permit CT, MRI, and PET diagnostic scans of the patient to be performed in the simulation and treatment position employing the same mask, the system has been tested in order to demonstrate the reproducibility of immobilization throughout a radical course of irradiation. Three-dimensional analysis of patient position over an 8-week course of daily radiation treatment has been performed for nine patients from digitization of anatomic points identified on orthogonal radiographs. Studies employing weekly simulation indicate that patient treatment position movement can be restricted to 2 mm over the course of treatment. This easily constructed system permits rapid mask formation to be performed on the treatment simulator, resulting in an immobilization device comparable to masks produced with vacuum-forming techniques. Details of motion analysis and central axis CT, MRI, and PET markers are offered.     

三维CT模拟定位计划系统的临床应用研究

[目的]通过三维CT模拟定位计划系统的临床应用研究。评价其在放疗听作用。[方法]将螺旋CT,三维激光定位系统和Focus9200三维计划系统通过网络连接,形成放疗科专用的,集影像诊断,图像传送,肿瘤定位和三维计划为一体的三维CT模拟定位计划系统。分别对143例肿瘤病人进行CT模拟定位和治疗计划。[结果]CT模拟定位和X线模拟定位一样可完成从定位到体表标记的全过程,利用CT进行定位,可为靶区的确定,复杂多野照射,适形调强放疗以及立体定向放疗提供更多的图像信息和更高的定位精度,使治疗中心和实际靶中心的重复误差小于1mm。[结论]CT模拟定位可用于大多数肿瘤病人的定位,是实现高精度放疗的必备设备之一。     

Research and development of remote training system for radiotherapy CT simulation based on virtual reality technology

Objective To develop a remote training system for CT simulation positioning of radiotherapy using virtual reality technology, and to explore a new method of medical training. Methods The 3DMax and Maya were employed to establish the 3D model. The unity3D engine was adopted to develop 3D virtual operation and interaction system. Java spring MVC architecture was utilized as the system background service. MySQL was used as the background database system. The users were assigned into two roles:teacher and student, and the modes were divided into teaching and assessment modes. Results The function of the system covered the whole process of CT simulation positioning, mainly including modules of patient information management, CT simulation positioning machine cognition, body position fixation technology, CT positioning scanning, and emergency handling, etc. Since it was put into use in 2018, the system has been running stably, with 14920 pages views and an 86.66% pass rate. Compared with the traditional training, the training efficiency has been significantly improved and has received unanimous recognition. Conclusions The remote training system can effectively improve the clinical practice ability and humanistic care ability of the trainees, which has good autonomy, sharing, and innovation. At present, the system has been put online and has strong popularization with prospects for broad application.     

Training on N.O.T.E.S.: From history we learn

Surgical errors occurring early in the learning curve of laparoscopic surgery providers delayed the uptake and progress of minimally invasive surgery (MIS) for years. This taught us a valuable lesson; innovations in surgical techniques should not be rapidly implemented until all aspects including applicability, feasibility and safety have been fully tested. In 2005, the Natural Orifice Surgery Consortium for Assessment and Research (NOSCAR) published a white paper highlighting the barriers to NOTES development and identifying key elements for its progress. One of these elements is the training of future providers. Proficiency-based, virtual reality simulation will offer a feasible alternative to animal testing once the safety and efficacy parameters of NOTES are established. Recent advances in imaging including computed tomography (CT) scanning, magnetic resonance imaging (MRI) scanning, and ultrasound (US) scanning can offer improved image registration and real-time tracking. Combining these advanced imaging technologies with the newly designed virtual reality simulators will result in a fully comprehensive simulation curriculum which will offer a unique facility for future NOTES providers to train anytime, anywhere, and as much as they need to in order to achieve the pre-set proficiency levels for a variety of NOTES procedures. Furthermore they will incorporate patient-specific anatomical models obtained from patient imaging and uploaded onto the simulator to ensure face reliability and validity assurance. Training in a clean, safe environment with proximate feedback and performance analysis will help accelerate the learning curve and therefore improve patients' safety and outcomes in order to maximize the benefits of innovative access procedures such as NOTES.     

基于虚拟现实技术的放疗CT模拟定位远程培训系统研发

目的 研发一种基于虚拟现实技术的放疗CT模拟定位的远程培训系统,探索一种医学培训的新方法。方法 使用3DMax与Maya进行3D建模,Unity3D引擎开发3D虚拟操作及交互系统;Java的SpringMvc架构作为系统后台服务,MySQL作为后台数据库系统;并将用户分为教师和学员两种角色,模式分为教学与考核模式。结果 系统功能涵盖CT模拟定位全过程,主要包括患者信息管理、CT模拟定位机认知、体位固定技术、CT定位扫描、处理突发事件等模块。自2018年投入使用以来,运行稳定,系统浏览量达14 920人次,培训通过率为86.66%。与传统培训相比,培训效率明显提升,并获得一致好评。结论 远程培训系统能有效提升学员的临床实践能力、人文关怀能力,具有良好的自主性、共享性、创新性。目前系统已上线且推广性较强,应用前景广阔。     

Analysis of minimally invasive directional antennas for microwave tissue ablation

Abstract

Purpose: Microwave ablation (MWA) applicators capable of creating directional heating patterns offer the potential of simplifying treatment of targets in proximity to critical structures and avoiding the need for piercing the tumour volume. This work reports on improved directional MWA antennas with the objectives of minimising device diameter for percutaneous use (≤ ～13 gauge) and yielding larger ablation zones.

Methods: Two directional MWA antenna designs, with a modified monopole radiating element and spherical and parabolic reflectors are proposed. A 3D-coupled electromagnetic heat transfer with temperature-dependent material properties was implemented to characterise MWA at 40 and 77 W, for 5 and 10?min. Simulations were also used to assess antenna impedance matching within liver, kidney, lung, bone and brain tissue. The two antenna designs were fabricated and experimentally evaluated with ablations in ex vivo tissue at the two power levels and treatment durations (n?=?5 repetitions for each group).

Results: The computed specific absorption rate (SAR) patterns for both antennas were similar, although simulations indicated slightly greater forward penetration for the parabolic antenna. Based on simulations for antennas inserted within different tissues, the proposed antenna design appears to offer good impedance matching for a variety of tissue types. Experiments in ex vivo tissue showed radial ablation depths of 19?±?0.9?mm in the forward direction for the applicator with spherical reflector and 18.7?±?0.7?mm for the applicator with parabolic reflector.

Conclusion: These results suggest the applicator may be suitable for creating localised directional ablation zones for treating small and medium-sized targets with a percutaneous approach.     

Combined microwave ablation and systemic chemotherapy for liver metastases from oesophageal cancer: Preliminary results and literature review

Purpose: Oesophageal cancer is a highly aggressive disease with about 50% of patients presenting with advanced or metastatic disease at initial diagnosis. In this study we assessed combined microwave ablation (MWA) and systemic chemotherapy in the treatment of liver metastases arising from oesophageal squamous cell carcinoma (OSCC). Materials and methods: Between February 2009 and June 2014, OSCC patients who underwent percutaneous MWA?+?concurrent systemic chemotherapy and systemic chemotherapy alone for liver metastases were enrolled in this study. Overall survival (OS) and progression-free survival (PFS) were recorded and compared between groups. Results: In total 15 patients with 25 liver metastases who underwent ultrasound-guided percutaneous MWA and chemotherapy were enrolled in this study. Technical success was achieved in 96% (24/25) of metastatic liver tumours. No major or minor complications associated with MWA procedures were observed. The median OS and PFS from initial MWA were 13 months and 4 months. The 1-, 2-, 3-, 4-year OS rates after MWA were 53.3%, 26.7%, 13.3%, and 13.3%, respectively. The 1- and 2-year PFS rates after MWA were 26.7% and 13.3%. The OS and PFS of the MWA?+?systemic chemotherapy group were superior than those of patients who received systemic chemotherapy alone (P?=?0.011 and 0.030, respectively). Conclusions: Combined MWA with systemic chemotherapy is a feasible, safe and effective treatment for liver metastases from OSCC.     

Differences in target outline delineation from CT scans of brain tumours using different methods and different observers.

PURPOSE: To assess errors resulting from manual transfer of contour information for three-dimensional (3-D) target reconstruction, and to determine variations in target volume delineation of brain tumours by different radiation oncologists. MATERIALS AND METHODS: Images of 18 patients with intracranial astrocytomas were used for retrospective treatment planning by five radiation oncologists. In this study, the target outline was delineated on sequential CT slices by an experienced radiation oncologist. Thereafter, the target outline was manually reconstructed by five radiation oncologists onto an A-P or lateral scout film. The same target outline was also reconstructed as a projection using the Beam's-eye view capability on a CT simulator unit. The two target outlines were compared by encompassing each shape with the smallest rectangle. The manually-reconstructed radiation field was termed 'Field manually established on X-ray film (F-X)', and the automatically-established field was termed 'Field established by CT simulator (F-CT)'. In a second part of this study, four radiation oncologists defined contours from contrast enhanced CT images of nine patients with intracranial astrocytomas. The CT images of these nine cases included five pre-operative cases and four post-operative cases. Both gross tumour volume (GTV) and clinical target volume (CTV) were outlined on sequential CT slices. The target outlines for the four radiation oncologists were compared by identifying the smallest rectangular field surrounding the projection of these contours. The field established by each radiation oncologist was termed 'Field of target volume (F-TV)', and the overlapping portion of the four F-TVs for each case was termed 'Overlapped field of the target volume (Fo-TV)'. RESULTS: The average distance between the isocentres of F-X and F-CT was 0.6 +/- 0.4 cm (mean +/- SD). The average ratio of the area of F-X divided by the area of F-CT was 1.04 +/- 0.12. The area of F-X was wider than the area of F-CT for four of the five oncologists. The ratio of the area of F-TV divided by the area of Fo-TV was calculated. The average ratio was relatively greater for CTV (2.07 in pre-operative cases and 2.11 in post-operative cases) than for GTV (1.12 in pre-operative cases and 1.41 in post-operative cases). Among radiation oncologists, variations in the delineation of GTV were smaller than those of CTV. CONCLUSIONS: When using an X-ray simulator in treatment planning, errors resulting from the manual transfer of CT contour information to planar radiographs must be considered. When computer techniques are used to project contours onto radiographs errors resulting from individual variations when performing the contouring must be considered.     

Microwave ablation-assisted liver gene transfection in rats

Purpose: Thermal ablation has been used to manage liver malignancy. This study aimed to assess histological changes in rat liver after microwave ablation (MWA) and to investigate whether thermal damage caused by MWA on surrounding liver tissue enhances the efficiency of liver gene transfer.

Methods: MWA was applied to rat liver, and the pathological tissue and ultrastructural changes were evaluated. Green fluorescent protein (GFP) and Renilla luciferase-expressing plasmids were administered to liver tissues by direct injection. GFP expression in liver tissue was analysed in frozen sections using an inverted fluorescence microscope, and Renilla luciferase expression in target tissue was determined using a luminometer.

Results: Tissue demarcations were observed in liver tissue after ablation, and a transition zone with morphological changes was present between necrotic and normal tissue. Hepatocytes in the transition zone showed decreased numbers of microvilli on cell surfaces and increased extracellular space. GFP expression was observed in the transition zone after MWA and plasmid injection and lasted up to 7 days post-ablation. Both the fluorescence and luminescence levels in the transition zone of the liver tissue were significantly higher than those in the untreated tissue (P?Conclusions: Direct plasmid injection to the liver tissue of the transition zone after MWA can achieve effective gene transfection. These findings provide an experimental basis for exploring MWA-assisted target gene transfer for cancer gene therapy.     

Clinical impact of cone beam computed tomography on iterative treatment planning during ultrasound-guided percutaneous ablation of liver malignancies

A standardized cone beam computed tomography (CBCT) protocol may impact optimal ablation probe(s) positioning during ultrasound-guided microwave ablation (MWA). To evaluate this hypothesis, 15 patients underwent ultrasound-guided percutaneous MWA of 15 liver lesions (10 hepatocellular carcinomas, 5 metastasis ranging 11–41 mm) with the ultrasound guidance assisted by a dedicated CBCT protocol. Pre-procedural enhanced CBCT (ceCBCT) was performed after intravenous contrast administration to visualize the lesion and determine the optimal approach using CBCT-based ablation planning software. MW antennas were positioned under ultrasound guidance, and non-enhanced CBCT was performed after deployment and fused with pre-procedural ceCBCT to assess tumor targeting and modify subsequent steps of the procedure. CBCT lesion detection accuracy and number of needle repositioning on the basis of CBCT information were recorded. Clinical success was measured on 1-month follow-up contrast-enhanced CT. The target lesion was detected on ceCBCT in 13 out of 15 patients (87%). The undetected lesions were only visible on diagnostic contrast-enhanced magnetic resonance imaging, which was then fused to the CBCT and fluoroscopy to facilitate targeting. MW antennas were repositioned on the basis of CBCT in 11 lesions (73%). Clinical success was achieved in 14/15 ablations (93%) with a mean follow-up of X months. The only case of local recurrence was expected, as the intent was tumor debulking. CBCT imaging during ultrasound-guided liver ablation is feasible and leads to ablation device repositioning in the majority of cases.     

微波消融治疗肝脏恶性肿瘤的临床价值

  目的  探讨微波消融(MWA)治疗肝脏恶性肿瘤的临床疗效及并发症分析。  方法  208例肝脏恶性肿瘤患者接受了241例次的MWA。肝细胞肝癌(HCC)171例行198例次的MWA, 肿瘤总数301个, 平均1.5个, 肿瘤平均最大直径(2.9±1.3)em, 其中57例接受了肝切除联合MWA; 肝转移癌(MLC)37例行43例次的MWA, 肿瘤总数67个, 平均1.6个, 肿瘤平均最大直径(2.6±1.5)cm。全组病例的治疗通过经皮和开腹两种途径, 治疗后定期进行影像学和肿瘤标志物检查。  结果  MWA 1个月后行增强CT检查, HCC 301个肿瘤中285个完全消融, 完全消融率为94.7%(285/301), MLC 67个肿瘤中62个完全消融, 完全消融率为92.5%(62/67)。随访3~43个月, HCC局部复发率为8.4%(24/285), 1、2、3年生存率分别为89.0%、74.2%、53.6%, 其中肝切除联合MWA治疗的患者1、2、3年生存率分别为81.3%、66.4%、46.7%;MLC局部复发率为9.7%(6/62), 中位生存期17~23个月。HCC患者MWA的严重并发症发生率为2.5%(5/198), MLC患者的治疗未出现严重并发症。  结论  MWA治疗肝脏恶性肿瘤创伤小, 安全有效, 具有重要的临床价值。      

The role of MRI in the early evaluation of lung microwave ablation

Purpose: To retrospectively investigate the role of a contrast enhanced MRI (ceMRI) performed 24?h after a microwave ablation (MWA) of the lung, in predicting local tumour progression (LTP) and detecting complications compared to an unenhanced CT.

Material and methods: Forty-nine patients who underwent MWA of 77 lung metastases between 2008 and 2015 were included. All patients received an unenhanced chest CT and a ceMRI (including T2 and ceT1) 24?h after MWA. The conspicuities of the peripheral rim and the ablated tumour were scored using 1–3 scales and compared between examinations. The safety margin was measured directly (both scores ≥2) and indirectly using a subtraction method. The ability of each imaging modality to predict LTP based on safety margin width was analysed using receiver operating characteristic curves. The MRI ability to detect a pneumothorax was compared to CT.

Results: The peripheral rim was best visualised on T2 followed by T1 and CT. The tumour was best visualised on CT, followed by T1 and T2. Direct safety margin measurement was possible on CT, ceT1 and T2 in 68.8%, 64.9% and 27.3% of cases, respectively. Direct CT (AUC?=?0.77) and ceT1 (AUC?=?0.76) measurements had better diagnostic performance than indirect CT (AUC?=?0.72), ceT1 (AUC?=?0.70) and T2 (AUC?=?0.69) measurements. The MRI sensitivity and specificity for pneumothorax were 60.8% and 87.0%, respectively. Only one pneumothorax >1?cm was missed.

Conclusions: A ceMRI performed 24?h after MWA of lung tumours has a similar ability to predict LTP and detect important complications as a CT has.     

Microwave ablation with or without resection for colorectal liver metastases

Background

Ablation with or without resection for colorectal liver metastases has been suggested as a potential method of improving survival if complete surgical resection is not possible. This study assessed the safety and efficacy of surgical microwave ablation (MWA) with or without resection for colorectal liver metastases.

Methods

A retrospective case series was reviewed. Data was extracted for all patients treated with open MWA with or without resection for colorectal liver metastases. Endpoints included postoperative 30-day morbidity and mortality, local treatment failure, disease free survival and overall survival.

Results

A total of 43 patients with technically irresectable disease were treated with MWA; 28 underwent combined MWA and resection, whilst 15 underwent MWA as the sole treatment modality. Overall post-operative morbidity was 35%, 30-day postoperative mortality 2%. At a median follow-up of 15 months, local treatment failure was observed in 4% of ablated lesions. 3-year OS was 36% for MWA group, compared to 45% for the combined ablate/resect group with 3-year DFS of 32% and 8% respectively.

Conclusion

Microwave ablation with or without resection is a safe and effective method of achieving local disease control. Ablation with or without resection is associated with good long-term outcomes, and may be a suitable treatment option for small non-resectable colorectal liver metastases.     

Is MRI more accurate than CT in estimating the real size of adrenal tumours?

BACKGROUND: The size of adrenal tumour plays an important role in the indications for surgical excision of non-functioning adrenal tumours and in selecting the best surgical approach. Computed tomography (CT) has been reported to underestimate the real size of adrenal lesions. The accuracy of magnetic resonance imaging (MRI) in predicting the true tumour size has not been previously investigated. The present retrospective study investigates the accuracy of MRI and CT in the pre-operative determination of true adrenal tumour size. METHODS: The medical records of 65 patients who underwent adrenalectomy for an adrenal mass were reviewed. The size of adrenal tumours as determined by pre-operative MRI and/or CT was compared with the "true" histopathological size. The impact of histological diagnosis on size estimation was also investigated. RESULTS: The median age at diagnosis was 42 years (range 1-82 years) and more patients were female (60%). Five patients had bilateral adrenalectomy, thus giving rise to 70 adrenal specimens. The histopathological size of adrenal tumours ranged from 0.9 to 26 cm with a mean of 5.96 cm and a median of 4.70 cm. For tumours larger than 3 cm, MRI significantly underestimated the real tumour size by 20% (P<0.001). CT also underestimated the size of such tumours by 18.1% (P<0.003). Adrenal phaeochromocytomas were consistently underestimated by both modalities. CONCLUSIONS: MRI and CT significantly underestimated the true size of adrenal tumours larger than 3 cm by 20% and 18%, respectively. Surgeons and endocrinologists should interpret the pre-operative size of adrenal lesions with caution. Copyright Harcourt Publishers Limited.     

A simple CT aperture emulator for use with a radiotherapy simulator.

Tumor localization in radiation treatment planning often involves the generation of quantitative anatomical data from multiple imaging modalities. It is desirable to take all of the images in the selected treatment position, which is usually decided upon during the initial simulator session. The different scanning modalities are often operated by different staff, at different times and in different locations; thus, it is difficult to ensure consistency in the position of the patient's body, and its documentation, at various times and places. Also, devices such as CT and MR scanners frequently pose restrictions due to their limited apertures. Failure to consider the physical limitations of such scanning equipment at the time of simulation or localization may result in placing the patient in a treatment position which will not fit through the aperture of the CT (or MRI) scanner, or which will result in a clinically important portion of the anatomy being "cut off" in the resulting scans. This can lead to re-simulation of the patient or result in a lack of accurate coordination of simulator and CT scan data. To minimize problems such as these, we have developed a CT Aperture Emulator which can be used at the time of the initial simulation. This is a lightweight "halo" easily attached to the simulator, which mimics the size and shape of the CT aperture. It permits reproducible adjustment of the patient's position, while allowing technologists and physicians to set up the patient with respect to potential CT constraints, in particular with regard to the use of immobilization and support devices. The emulator device also facilitates reproducing a patient's treatment position on the CT scanner. The concept has been found to have additional clinical uses and can be extended to a variety of imaging equipment.     

The role of a conventional simulator in multileaf-plan simulation: a proposal

Modern computer networks provide satisfying levels of data recording and verification between the treatment planning system (TPS) and the accelerators, while the main weakness of the preparation chain remains the simulation. When a conventional simulator is employed, it may adversely affect the three-dimensional treatment planning system (3DPS) process because of the difficulty to document the leaf positions on the simulator location films and on the patient's skin. With a conventional simulator, hard copies of the DRRs of each field and CT scans at isocenter level are needed. In an attempt to transfer more information displayed from a BEV perspective from the 3DPS to simulator radiographs, this study aimed to reduce the quality loss by using a 2D conventional simulator in a 3DPS process. We realized an acetate photocopy of TPS data for each field, from a BEV perspective, containing: DRR, wire frames of the PTV, organs at risk and MLC aperture. The photocopies, with an appropriate magnification factor to obtain a correct projective value (ratio 1:1) at isocenter level, are carefully placed on the radiographic images on the same hard copy which allows us to better understand possible setup errors and obliges us to correct these. The method provides reliable documentation, facilitates treatment verification, and fulfils the criteria for MLC simulation. It is accurate, simple, and very inexpensive.