A universal verification and protocol system for teletherapy

To increase the quality of radiotherapy a verify and record system (VPS) was developed for teletherapy equipments, that takes control of manually adjusted irradiation parameters and of recording all relevant data of radiotherapy. The VPS can be adapted to special wishes of the user and it lends itself to application on different irradiation equipments. In the represented paper especially the extent of efficiency of the system is shown which is characterized by high operating comfort, flexible reacting to exceptional cases and by high date and operating security. The testing phase on an accelerator model has been brought to a close, actually the system is installed to an electron linear accelerator "Neptun 10p" and led to clinical trial.     

4D in vivo dose verification for real‐time tumor tracking treatments using EPID dosimetry

The use of sophisticated techniques such as gating and tracking treatments requires additional quality assurance to mitigate increased patient risks. To address this need, we have developed and validated an in vivo method of dose delivery verification for real-time aperture tracking techniques, using an electronic portal imaging device (EPID)-based, on-treatment patient dose reconstruction and a dynamic anthropomorphic phantom. Using 4DCT scan of the phantom, ten individual treatment plans were created, 1 for each of the 10 separate phases of the respiratory cycle. The 10 MLC apertures were combined into a single dynamic intensity-modulated radiation therapy (IMRT) plan that tracked the tumor motion. The tumor motion and linac delivery were synchronized using an RPM system (Varian Medical Systems) in gating mode with a custom breathing trace. On-treatment EPID frames were captured using a data-acquisition computer with a dedicated frame-grabber. Our in-house EPID-based in vivo dose reconstruction model was modified to reconstruct the 4D accumulated dose distribution for a dynamic MLC (DMLC) tracking plan using the 10-phase 4DCT dataset. Dose estimation accuracy was assessed for the DMLC tracking plan and a single-phase (50% phase) static tumor plan, represented a static field test to verify baseline accuracy. The 3%/3 mm chi-comparison between the EPID-based dose reconstruction for the static tumor delivery and the TPS dose calculation for the static plan resulted in 100% pass rate for planning target volume (PTV) voxels while the mean percentage dose difference was 0.6%. Comparing the EPID-based dose reconstruction for the DMLC tracking to the TPS calculation for the static plan gave a 3%/3 mm chi pass rate of 99.3% for PTV voxels and a mean percentage dose difference of 1.1%. While further work is required to assess the accuracy of this approach in more clinically relevant situations, we have established clinical feasibility and baseline accuracy of using the transmission EPID-based, in vivo patient dose verification for MLC-tracking treatments.     

Experiences with a prototype tracking and verification system implemented within an imaging center

RATIONALE AND OBJECTIVES: Most health care facilities currently struggle with protecting medical data privacy, misidentification of patients, and long patient waiting times. This article demonstrates a novel system for a clinical environment using wireless tracking and facial biometric technologies to automatically monitor and identify staff and patients to address these problems. MATERIALS AND METHODS: The design of the location tracking and verification system (LTVS) was based on a workflow study which was performed to observe the physical location and movement of patient and staff at the Healthcare Consultation Center II (HCC II) running hospital information systems, radiology information systems, picture archive and communication systems, and a voice recognition system. Based on the results from this workflow study, the LTVS was designed using a wireless real-time location system and a facial biometric system integrated with the radiology information system. The LTVS was tested for its functionality in a laboratory environment, then evaluated at HCC II. RESULTS: Experimental results in the laboratory and clinical environments demonstrated that patient and staff real-time location information and identity verification can be obtained from LTVS. Warning messages can immediately be sent to alert staff when patient's waiting time is over a predefined limit, and unauthorized access to a security area can be audited. Additionally, patient misidentification can be prevented during the course of examinations. CONCLUSIONS: The system enabled health care providers to streamline the patient workflow, protect against erroneous examinations and create a security zone to prevent, and audit unauthorized access to patient health care data required by the Health Insurance Portability and Accountability Act mandate.     

Design of a motion simulation system to assist respiratory gating for radiation therapy

Stereotactic ablative radiotherapy (SABR) aims to deliver high doses of radiation to kill cancer cells and shrink tumors in less than or equal to 6 fractions. However, organ motion during treatment is a challenging issue for this kind of technique. We develop a control system via Bluetooth technology to simulate and correct body motion during SABR. Methods: Radiation doses were analyzed, and the radiation damage protection capability was checked by external beam therapy 3 (EBT3) films irradiated by a linear accelerator. A wireless signal test was also performed. A validation was performed with 8 previously treated patient respiratory pattern records and 8 healthy volunteers. Results: The homemade simulation system consisted of 2 linear actuators, one movable stage with a maximal moving distance of 6.5 cm × 12.5 cm × 5 cm to simulate the respiratory pattern of 8 patients precisely with a median error of 0.36 mm and a maximal motion difference of 1.17 mm, and 3.17 and chipset transited signals to display them as a waveform. From the test with 8 volunteers, the chip could detect deep respiratory movement up to 3 cm. The effect of the chip on a radiation dose of 400 monitor units (MUs) by 6 MV photons and 200 MUs by 10 MV photons showed high penetration rates of 98.8% and 98.6%, respectively. Conclusions: We invented a tubeless and wireless respiratory gating detection chip. The chip has minimal interference with the treatment angles, good noise immunity and the capability to easily penetrate a variety of materials. The simulation system consisting of linear actuators also successfully simulates the respiratory pattern of real patients.     

An integrated system for clinical treatment verification of HDR prostate brachytherapy combining source tracking with pretreatment imaging

PurposeHigh-dose-rate (HDR) prostate brachytherapy treatment is usually delivered in one or a few large dose fractions. Poor execution of a planned treatment could have significant clinical impact, as high doses are delivered in seconds, and mistakes in an individual fraction cannot be easily rectified. Given that most potential errors in HDR brachytherapy ultimately lead to a geographical miss, a more direct approach to verification of correct treatment delivery is to directly monitor the position of the source throughout the treatment. In this work, we report on the clinical implementation of our treatment verification system that uniquely combines the 2D source-tracking capability with 2D pretreatment imaging, using a single flat panel detector (FPD).Methods and MaterialsThe clinical brachytherapy treatment couch was modified to allow integration of the FPD into the couch. This enabled the patient to be set up in the brachytherapy bunker in a position that closely matched that at treatment planning imaging. An anteroposterior image was acquired of the patient immediately before treatment delivery and was assessed by the Radiation Oncologist online, to reestablish the positions of the catheters relative to the prostate. Assessment of catheter positions was performed in the left-right and superior-inferior directions along the entire catheter length and throughout the treatment volume. Source tracking was then performed during treatment delivery, and the measured position of the source dwells were directly compared to the treatment plan for verification.ResultsThe treatment verification system was integrated into the clinical environment without significant change to workflow. Two patient cases are presented in this work to provide clinical examples of this system, which is now in routine use for all patient treatments in our clinic. The catheter positions were visualized relative to the prostate, immediately before treatment delivery. For one of the patient cases presented in this work, they agreed with the treatment plan on average by 1.5 mm and were identifiable as a predominantly inferior shift. The source tracking was performed during treatment delivery, and for the same case, the mean deviation from the planned dwell positions was 1.9 mm (max = 4.9 mm) for 280 positions across all catheters.ConclusionWe have implemented our noninvasive treatment verification system based on an FPD in the clinical environment. The device is integrated into a patient treatment couch, and the process is now included in the routine clinical treatment procedure with minor impact on workflow. The system which combines both 2D pretreatment imaging and HDR 2D source tracking provides a range of information that can be used for comprehensive treatment verification. The system has the potential to meaningfully improve safety standards by allowing widespread adoption of routine treatment verification in HDR brachytherapy.     

Bone motion analysis from dynamic MRI: acquisition and tracking

RATIONALE AND OBJECTIVES: For diagnosis, preoperative planning and postoperative guides, an accurate estimate of joint kinematics is required. It is important to acquire joint motion actively with real-time protocols. MATERIALS AND METHODS: We bring together MRI developments and new image processing methods in order to automatically extract active bone kinematics from multi-slice real-time dynamic MRI. We introduce a tracking algorithm based on 2D/3D registration and a procedure to validate the technique by using both dynamic and sequential MRI, providing a gold standard bone position measurement. RESULTS: We present our technique for optimizing jointly the tracking method and the acquisition protocol to overcome the trade-off in acquisition time and tracking accuracy. As a case study, we apply this methodology on a human hip joint. CONCLUSION: The final protocol (bFFE, TR/TE 3.5/1.1 ms, Flip angle 80 degrees , pixel size 4.7 x 2.6 mm, partial Fourier reduction factor of 0.65 in read direction, SENSE acceleration factor of 2, frame rate = 6.7 frames/s) provides sufficient morphological data for bone tracking to be carried out with an accuracy of 3 degrees in terms of joint angle.     

Advantages and limitations of prospective head motion compensation for MRI using an optical motion tracking device

RATIONALE AND OBJECTIVES: Subject motion appears to be a limiting factor in numerous magnetic resonance (MR) imaging (MRI) applications. In particular, head tremor, which often accompanies stroke, may render certain high-resolution two- (2D) and three-dimensional (3D) techniques inapplicable. The reason for that is head movement during acquisition. The study objective is to achieve a method able to compensate for complete motion during data acquisition. The method should be usable for every sequence and easily implemented on different MR scanners. MATERIALS AND METHODS: The possibility of interfacing the MR scanner with an external optical motion-tracking system capable of determining the object's position with submillimeter accuracy and an update rate of 60 Hz is shown. Movement information on the object position (head) is used to compensate for motion in real time by updating the field of view (FOV) by recalculating the gradients and radiofrequency parameter of the MR scanner during acquisition of k-space data, based on tracking data. RESULTS: Results of rotation phantom, in vivo experiments, and implementation of three different MRI sequences, 2D spin echo, 3D gradient echo, and echo planar imaging, are presented. Finally, the proposed method is compared with the prospective motion correction software available on the scanner software. CONCLUSION: A prospective motion correction method that works in real time only by updating the FOV of the MR scanner is presented. Results show the feasibility of using an external optical motion-tracking system to compensate for strong and fast subject motion during acquisition.     

External respiratory motion for abdominal radiotherapy patients: implications for patient alignment

Conformal external beam radiotherapy relies on accurate spatial positioning of the tumor and normal tissues during treatment. For abdominal patients, this is complicated by the motion of internal organs and the external patient contour due to respiration. As external motion influences the degree of accuracy achievable in patient setup, this motion was studied to provide indication of motions occurring during treatment, as well as to assess the technique of breath-holding at exhale (B-HEX). The motion of external abdominal points (anterior and right lateral) of a series of volunteers was tracked in real-time using an infrared tracking system, with the volunteers in treatment position. The resulting motion data was assessed to evaluate (1) the change in position of each point per breath/breath-hold, (2) the change in position between breaths/breath-holds, and (3) the change in position across the whole recording time. Analysis shows that, for the anterior abdominal point, there is little difference in the variation of position with time for free-breathing as opposed to the B-HEX technique. For the lateral point however, the B-HEX technique reduces the motion during each treatment cycle (i.e., during the breath-hold) and over an extended period (i.e., during a series of breath-holds). The B-HEX technique thus provides greater accuracy for setup to lateral markers and provides the opportunity to reduce systematic and random localization errors.     

Development and verification of THORplan—A BNCT treatment planning system for THOR

THORplan is a treatment planning system under continuous development and refinement at Tsing Hua University, Taiwan, for BNCT purpose. New features developed for homogeneous model calculation include material grouping model, and voxel data reconstruction model. Material grouping model is a two-step grouping method, tissue-volume-percent grouping method followed by atom-gram-density grouping method. The root mean square difference of neutron flux due to material grouping is <0.8%. In the voxel data reconstruction model, voxel neutron dose is calculated based on the material composition and dose of individual atom of each voxel, which is calculated by linear interpolation from the dose of individual atom of neighboring cells tallied in MCNP calculation. The detailed voxel model is used to benchmark the accuracy of the new features developed for the homogeneous model calculation. The maximum error of the neutron flux and dose of voxels using the homogeneous cell model is 5% and 7%, respectively. Big improvement of accuracy of voxel dose over the original dose calculation model based on F6 tally is observed at locations containing very heterogeneous compositions.     

周期运动靶区受照剂量分布的模拟计算及验证

目的 基于剂量矩阵叠加算法计算周期运动靶区的剂量分布,并验证其准确性。方法 用二维空气电离室矩阵MatriXX系统和周期运动平台相配合,实测靶区在静态和周期运动状态下进行调强放疗时的剂量分布。根据周期运动靶区在照射过程中的运动特点,提出了预测其剂量分布的剂量矩阵叠加算法,并用Matlab 7.0工具软件编写了相应的模拟计算程序,预测了不同运动幅度(±5、±10、±15 mm)时靶区的剂量分布。结果 周期运动靶区的模拟剂量分布与静态靶区的实测剂量分布相比,在靶区中心大部分区域二者相对偏差小于1%,在靶区运动方向,模拟的高剂量区域向内收缩,低剂量区域向外扩张,但50%等剂量曲线范围未见明显改变。周期运动靶区的模拟剂量分布与动态下的实测分布相比,二者的离轴比几乎重合,仅在射野外的低剂量区域中(<10%)有细微偏差。结论 剂量矩阵叠加算法能较准确计算周期运动靶区的受照剂量分布。     

A digital fluoroscopic imaging system for verification during external beam radiotherapy

A digital fluoroscopic (DF) imaging system has been constructed to obtain portal images for verification during external beam radiotherapy. The imaging device consists of a fluorescent screen viewed by a highly sensitive video camera through a mirror. The video signal is digitized and processed by an image processor which is linked on-line with a host microcomputer. The image quality of the DF system was compared with that of film for portal images of the Burger phantom and the Alderson anthropomorphic phantom using 10 MV X-rays. Contrast resolution of the DF image integrated for 8.5 sec. was superior to the film resolution, while spatial resolution was slightly inferior. The DF image of the Alderson phantom processed by the adaptive histogram equalization was better in showing anatomical landmarks than the film portal image. The DF image integrated for 1 sec. which is used for movie mode can show patient movement during treatment.     

Dosimetric evaluation of MLC-based dynamic tumor tracking radiotherapy using digital phantom: Desired setup margin for tracking radiotherapy

The purpose of this study is to evaluate the dosimetric impact of the margin on the multileaf collimator-based dynamic tumor tracking plan. Furthermore, an equivalent setup margin (EM) of the tracking plan was determined according to the gated plan. A 4-dimensional extended cardiac-torso was used to create 9 digital phantom datasets of different tumor diameters (TDs) of 1, 3, and 5?cm and motion ranges (MRs) of 1, 2, and 3?cm. For each dataset, respiratory gating (30% to 70% phase) and tumor tracking treatment plans were prepared using 8-field 3-dimensional conformal radiation therapy by 4-dimensional dose calculation. The total lung V20 was calculated to evaluate the dosimetric impact for each case and to estimate the EM with the same impact on lung V20 obtained with the gating plan with a setup margin of 5?mm. The EMs for {TD?=?1?cm, MR?=?1?cm}, {TD?=?1?cm, MR?=?2?cm}, and {TD?=?1?cm, MR?=?3?cm} were estimated as 5.00, 4.16, and 4.24?mm, respectively. The EMs for {TD?=?5?cm, MR?=?1?cm}, {TD?=?5?cm, MR?=?2?cm}, and {TD?=?5?cm, MR?=?3?cm} were estimated as 4.24?mm, 6.35?mm, and 7.49?mm, respectively. This result showed that with a larger MR, the EM was found to be increased. In addition, with a larger TD, the EM became smaller. Our result showing the EMs provided the desired accuracy for multileaf collimator-based dynamic tumor tracking radiotherapy.     

Development of motion correction technique for cardiac <Superscript>15</Superscript>O-water PET study using an optical motion tracking system

Objective  

Cardiac ¹⁵O-water PET studies provide an accurate quantitation of regional myocardial blood flow (rMBF). We developed a motion correction system using an optical motion-tracking device to detect a subject’s global movement for cardiac study.     

Coronary MR angiography: respiratory motion correction with BACSPIN

PURPOSE: To improve the signal-to-noise ratio (SNR) of breath-held coronary magnetic resonance angiography (CMRA) without increasing the number or duration of breath holds. MATERIALS AND METHODS: In this BACSPIN (Breathing AutoCorrection with SPiral INterleaves) technique, a single breath-held electrocardiogram (ECG)-gated multi-slice interleaved-spiral data set is acquired, followed by repeated imaging of the same slices during free breathing. Each spiral interleaf from the breath-held data set is used as a standard for comparison with corresponding acquisitions at the same interleaf angle during free breathing. The most closely matched acquisitions are incorporated into a multi-slice, multi-average data set with increasing SNR over time. In-plane translations of the coronary artery can be measured and compensated for each accepted acquisition before combination with the other acquisitions. RESULTS: CMRA was performed on six volunteers, with improved SNR and minimal motional blurring. In some cases, breath holding could be dispensed with completely and the average respiratory position used as a reference. CONCLUSION: BACSPIN provides a promising method for CMRA with improved SNR and limited breath-holding requirements.     

Fourier tracking of myocardial motion using cine-PC data

A closed-form integration method is derived and analyzed for computing motion trajectories from velocity field data, particularly as measured by phase contrast (PC) cine MR imaging. By modeling periodic motion as composed of Fourier harmonics and integrating the material velocity of the tracked point in the frequency domain, this method gives an unbiased trajectory estimate in the presence of white measurement noise and eddy current effects. When applied to cine PC data, the method can incorporate compensation for the frequency response of the cine interpolation, offering a further improvement on the tracking accuracy. In simulation and phantom studies, the estimated trajectories were in excellent agreement with the true trajectories. Encouraging results have also been obtained on data from volunteers.     

A computationally efficient method for tracking reference position displacements for motion compensation in magnetic resonance imaging.

A fast and computationally efficient method for detecting and tracking the displacement of a reference structure within the body using MR imaging is described. This method is used to determine the position of the diaphragm in order to synchronize the data acquisition to the same relative position of the abdominal and thoracic organs, thereby minimizing or eliminating respiratory motion artifacts. The method described uses the time domain linear phase shift of a reference structure to determine its spatial positional displacement as a function of the respiratory cycle. The signal from a two-dimensional rectangular excitation column is first Fourier-transformed to the image domain, apodized, and then transformed back to the time domain. The relative displacement of a target edge in the image domain is determined from an autocorrelation of the resulting time domain information. This technique was found to require between three and eight times less computation than either cross-correlation or least-squares analysis, depending on the navigator parameters. Magn Reson Med 42:548-553, 1999.