1
|
Munbodh R, Chen Z, Jaffray DA, Moseley DJ, Knisely JPS, Duncan JS. A frequency-based approach to locate common structure for 2D-3D intensity-based registration of setup images in prostate radiotherapy. Med Phys 2016; 34:3005-17. [PMID: 17822009 PMCID: PMC2796184 DOI: 10.1118/1.2745235] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In many radiotherapy clinics, geometric uncertainties in the delivery of 3D conformal radiation therapy and intensity modulated radiation therapy of the prostate are reduced by aligning the patient's bony anatomy in the planning 3D CT to corresponding bony anatomy in 2D portal images acquired before every treatment fraction. In this paper, we seek to determine if there is a frequency band within the portal images and the digitally reconstructed radiographs (DRRs) of the planning CT in which bony anatomy predominates over non-bony anatomy such that portal images and DRRs can be suitably filtered to achieve high registration accuracy in an automated 2D-3D single portal intensity-based registration framework. Two similarity measures, mutual information and the Pearson correlation coefficient were tested on carefully collected gold-standard data consisting of a kilovoltage cone-beam CT (CBCT) and megavoltage portal images in the anterior-posterior (AP) view of an anthropomorphic phantom acquired under clinical conditions at known poses, and on patient data. It was found that filtering the portal images and DRRs during the registration considerably improved registration performance. Without filtering, the registration did not always converge while with filtering it always converged to an accurate solution. For the pose-determination experiments conducted on the anthropomorphic phantom with the correlation coefficient, the mean (and standard deviation) of the absolute errors in recovering each of the six transformation parameters were Theta(x):0.18(0.19) degrees, Theta(y):0.04(0.04) degrees, Theta(z):0.04(0.02) degrees, t(x):0.14(0.15) mm, t(y):0.09(0.05) mm, and t(z):0.49(0.40) mm. The mutual information-based registration with filtered images also resulted in similarly small errors. For the patient data, visual inspection of the superimposed registered images showed that they were correctly aligned in all instances. The results presented in this paper suggest that robust and accurate registration can be achieved with intensity-based methods by focusing on rigid bony structures in the images while diminishing the influence of artifacts with similar frequencies as soft tissue.
Collapse
Affiliation(s)
- Reshma Munbodh
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, USA.
| | | | | | | | | | | |
Collapse
|
2
|
Yoon M, Cheong M, Kim J, Shin DH, Park SY, Lee SB. Accuracy of an automatic patient-positioning system based on the correlation of two edge images in radiotherapy. J Digit Imaging 2010; 24:322-30. [PMID: 20127267 DOI: 10.1007/s10278-009-9269-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Revised: 11/27/2009] [Accepted: 12/13/2009] [Indexed: 11/29/2022] Open
Abstract
We have clinically evaluated the accuracy of an automatic patient-positioning system based on the image correlation of two edge images in radiotherapy. Ninety-six head & neck images from eight patients undergoing proton therapy were compared with a digitally reconstructed radiograph (DRR) of planning CT. Two edge images, a reference image and a test image, were extracted by applying a Canny edge detector algorithm to a DRR and a 2D X-ray image, respectively, of each patient before positioning. In a simulation using a humanoid phantom, performed to verify the effectiveness of the proposed method, no registration errors were observed for given ranges of rotation, pitch, and translation in the x, y, and z directions. For real patients, however, there were discrepancies between the automatic positioning method and manual positioning by physicians or technicians. Using edged head coronal- and sagittal-view images, the average differences in registration between these two methods for the x, y, and z directions were 0.11 cm, 0.09 cm and 0.11 cm, respectively, whereas the maximum discrepancies were 0.34 cm, 0.38 cm, and 0.50 cm, respectively. For rotation and pitch, the average registration errors were 0.95° and 1.00°, respectively, and the maximum errors were 3.6° and 2.3°, respectively. The proposed automatic patient-positioning system based on edge image comparison was relatively accurate for head and neck patients. However, image deformation during treatment may render the automatic method less accurate, since the test image many differ significantly from the reference image.
Collapse
Affiliation(s)
- Myonggeun Yoon
- Proton Therapy Center, National Cancer Center, 809 Madu 1-dong, Ilsandong-gu, Goyang, 411-769, Korea.
| | | | | | | | | | | |
Collapse
|
3
|
Munbodh R, Chen Z, Jaffray DA, Moseley DJ, Knisely JPS, Duncan JS. Automated 2D-3D registration of portal images and CT data using line-segment enhancement. Med Phys 2008; 35:4352-61. [PMID: 18975681 DOI: 10.1118/1.2975143] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In prostate radiotherapy, setup errors with respect to the patient's bony anatomy can be reduced by aligning 2D megavoltage (MV) portal images acquired during treatment to a reference 3D kilovoltage (kV) CT acquired for treatment planning purposes. The purpose of this study was to evaluate a fully automated 2D-3D registration algorithm to quantify setup errors in 3D through the alignment of line-enhanced portal images and digitally reconstructed radiographs computed from the CT. The line-enhanced images were obtained by correlating the images with a filter bank of short line segments, or "sticks" at different orientations. The proposed methods were validated on (1) accurately collected gold-standard data consisting of a 3D kV cone-beam CT scan of an anthropomorphic phantom of the pelvis and 2D MV portal images in the anterior-posterior (AP) view acquired at 15 different poses and (2) a conventional 3D kV CT scan and weekly 2D MV AP portal images of a patient over 8 weeks. The mean (and standard deviation) of the absolute registration error for rotations around the right-lateral (RL), inferior-superior (IS), and posterior-anterior (PA) axes were 0.212 degree (0.214 degree), 0.055 degree (0.033 degree) and 0.041 degree (0.039 degree), respectively. The corresponding registration errors for translations along the RL, IS, and PA axes were 0.161 (0.131) mm, 0.096 (0.033) mm, and 0.612 (0.485) mm. The mean (and standard deviation) of the total registration error was 0.778 (0.543) mm. Registration on the patient images was successful in all eight cases as determined visually. The results indicate that it is feasible to automatically enhance features in MV portal images of the pelvis for use within a completely automated 2D-3D registration framework for the accurate determination of patient setup errors. They also indicate that it is feasible to estimate all six transformation parameters from a 3D CT of the pelvis and a single portal image in the AP view.
Collapse
Affiliation(s)
- Reshma Munbodh
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, USA.
| | | | | | | | | | | |
Collapse
|
4
|
Lasserre P, Cutt B, Moffat J. Edge detection of the radiation field in double exposure portal images using a curve propagation algorithm. J Appl Clin Med Phys 2008; 9:3-16. [PMID: 19020476 PMCID: PMC5722364 DOI: 10.1120/jacmp.v9i4.2710] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Revised: 04/16/2008] [Accepted: 04/28/2008] [Indexed: 11/25/2022] Open
Abstract
An accurate detection of the radiation field is crucial to 3D conformal radiotherapy (3D‐CRT). Automated techniques to detect the field edges on double exposure portal images have previously focused on thresholding techniques. In this paper, we present a new approach based on a curve propagation technique (the Fast Marching method) which proves to be more effective at detecting the radiation field than its thresholding counterpart. The comparison of both techniques in terms of computational speed and effectiveness of the detection is presented using complex images with non‐homogeneous intensity levels inside the radiation field, and gradual variations in intensity level at the field boundaries. Results show that our Fast Marching method is easier to automate, and converges faster to the boundaries of the segmented radiation field. The computation time of the Fast Marching technique is five times faster in typical portal images. PACS numbers: 87.53.Oq, 87.57.Nk, 87.57.‐s.
Collapse
Affiliation(s)
- Patricia Lasserre
- Irving K. Barber School of Arts and Sciences, University of British Columbia Okanagan, Kelowna, Canada
| | - Bryce Cutt
- Irving K. Barber School of Arts and Sciences, University of British Columbia Okanagan, Kelowna, Canada
| | - James Moffat
- Irving K. Barber School of Arts and Sciences, University of British Columbia Okanagan, Kelowna, Canada
| |
Collapse
|
5
|
Fu D, Kuduvalli G. A fast, accurate, and automatic 2D-3D image registration for image-guided cranial radiosurgery. Med Phys 2008; 35:2180-94. [DOI: 10.1118/1.2903431] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
6
|
Bijdekerke P, Verellen D, Tournel K, Vinh-Hung V, Somers F, Bieseman P, Storme G. TomoTherapy: Implications on daily workload and scheduling patients. Radiother Oncol 2008; 86:224-30. [DOI: 10.1016/j.radonc.2007.10.036] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 10/22/2007] [Accepted: 10/23/2007] [Indexed: 11/24/2022]
|
7
|
Zeng L, Da X, Gu H, Yang D, Yang S, Xiang L. High antinoise photoacoustic tomography based on a modified filtered backprojection algorithm with combination wavelet. Med Phys 2007; 34:556-63. [PMID: 17388173 DOI: 10.1118/1.2426406] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
How to extract the weak photoacoustic signals from the collected signals with high noise is the key to photoacoustic signal processing. We have developed a modified filtered backprojection algorithm based on combination wavelet for high antinoise photoacoustic tomography. A Q-switched-Nd: yttrium-aluminum-garnet laser operating at 532 nm is used as light source. The laser has a pulse width of 7 ns and a repetition frequency of 20 Hz. A needle polyvinylidene fluoride hydrophone with diameter of 1 mm is used to capture photoacoustic signals. The modified algorithm is successfully applied to imaging vascular network of a chick embryo chorioallantoic membrane in situ and brain structure of a rat brain in vivo, respectively. In the reconstructed images, almost all of the capillary vessels and the vascular ramifications of the chick embryo chorioallantoic membrane are accurately resolved, and the detailed brain structures of the rat brain organization are clearly identified with the skull and scalp intact. The experimental results demonstrate that the modified algorithm has much higher antinoise capacity, and can greatly improve the reconstruction image quality. The spatial resolution of the reconstructed images can reach 204 microm. The modified filtered back-projection algorithm based on the combination wavelet has the potential in the practical high-noise signal processing for deeply penetrating photoacoustic tomography.
Collapse
Affiliation(s)
- Lvming Zeng
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, South China Normal University, Guangzhou 510631, People's Republic of China
| | | | | | | | | | | |
Collapse
|
8
|
Improvement of edge response in multi-detector row CT by high-spatial-frequency sampling of projection data. Int J Comput Assist Radiol Surg 2007. [DOI: 10.1007/s11548-007-0067-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
9
|
Verellen D, Soete G, Linthout N, Tournel K, Storme G. Optimal control of set-up margins and internal margins for intra- and extracranial radiotherapy using stereoscopic kilovoltage imaging. Cancer Radiother 2006; 10:235-44. [PMID: 16854609 DOI: 10.1016/j.canrad.2006.05.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2006] [Accepted: 05/15/2006] [Indexed: 11/21/2022]
Abstract
In this paper the clinical introduction of stereoscopic kV-imaging in combination with a 6 degrees-of-freedom (6 DOF) robotics system and breathing synchronized irradiation will be discussed in view of optimally reducing interfractional as well as intrafractional geometric uncertainties in conformal radiation therapy. Extracranial cases represent approximately 70% of the patient population on the NOVALIS treatment machine (BrainLAB A.G., Germany) at the AZ-VUB, which is largely due to the efficiency of the real-time positioning features of the kV-imaging system. The prostate case will be used as an example of those target volumes showing considerable changes in position from day-to-day, yet with negligible motion during the actual course of the treatment. As such it will be used to illustrate the on-line target localization using kV-imaging and 6 DOF patient adjustment with and without implanted radio-opaque markers prior to treatment. Small lung lesion will be used to illustrate the system's potential to synchronize the irradiation with breathing in coping with intrafractional organ motion.
Collapse
Affiliation(s)
- D Verellen
- Department of Radiotherapy, Oncology Center, Academic Hospital, Vrije Universiteit Brussel (AZ-VUB), Laarbeeklaan 101, B-1090 Brussels, Belgium.
| | | | | | | | | |
Collapse
|
10
|
Munbodh R, Jaffray DA, Moseley DJ, Chen Z, Knisely JPS, Cathier P, Duncan JS. Automated 2D-3D registration of a radiograph and a cone beam CT using line-segment enhancement. Med Phys 2006; 33:1398-411. [PMID: 16752576 PMCID: PMC2796183 DOI: 10.1118/1.2192621] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The objective of this study was to develop a fully automated two-dimensional (2D)-three-dimensional (3D) registration framework to quantify setup deviations in prostate radiation therapy from cone beam CT (CBCT) data and a single AP radiograph. A kilovoltage CBCT image and kilovoltage AP radiograph of an anthropomorphic phantom of the pelvis were acquired at 14 accurately known positions. The shifts in the phantom position were subsequently estimated by registering digitally reconstructed radiographs (DRRs) from the 3D CBCT scan to the AP radiographs through the correlation of enhanced linear image features mainly representing bony ridges. Linear features were enhanced by filtering the images with "sticks," short line segments which are varied in orientation to achieve the maximum projection value at every pixel in the image. The mean (and standard deviations) of the absolute errors in estimating translations along the three orthogonal axes in millimeters were 0.134 (0.096) AP(out-of-plane), 0.021 (0.023) ML and 0.020 (0.020) SI. The corresponding errors for rotations in degrees were 0.011 (0.009) AP, 0.029 (0.016) ML (out-of-plane), and 0.030 (0.028) SI (out-of-plane). Preliminary results with megavoltage patient data have also been reported. The results suggest that it may be possible to enhance anatomic features that are common to DRRs from a CBCT image and a single AP radiography of the pelvis for use in a completely automated and accurate 2D-3D registration framework for setup verification in prostate radiotherapy. This technique is theoretically applicable to other rigid bony structures such as the cranial vault or skull base and piecewise rigid structures such as the spine.
Collapse
Affiliation(s)
- Reshma Munbodh
- Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, USA.
| | | | | | | | | | | | | |
Collapse
|
11
|
Yasuda N, Ishikawa Y, Kodera Y. Improvement of image quality in chest MDCT using nonlinear wavelet shrinkage with trimmed-thresholding. Nihon Hoshasen Gijutsu Gakkai Zasshi 2005; 61:1599-608. [PMID: 16395234 DOI: 10.6009/jjrt.kj00004022970] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Multidetector-row computed tomography (MDCT) has dramatically increased the speed of scanning, and allows high-resolution imaging compared with conventional single detector-row CT (SDCT). However, the use MDCT makes use of an increase in volume scanning, and causes a simultaneous increase in radiation dose to the patient. Thus, the radiation dose from the X-ray CT has become a problem in recent years. In this study, nonlinear wavelet-based edge preservation de-noising using trimmed-thresholding was applied to reconstructed low-dose chest MDCT images, and optimal wavelet processing including wavelet functions and thresholding methods was examined. Moreover, the usefulness of the de-noising for reducing radiation dose was examined. As a result of optimized edge preservation de-noising, noise reduction was achieved with little deterioration in image quality, and the wavelet function used at that time was Coiflet's with shorter support. As a result, almost the same quality of reconstructed image of the chest phantom was obtained for conventional scanning and low-dose scanning with the wavelet de-noising method using trimmed- thresholding. That is, the radiation dose from MDCT could be reduced using this wavelet-based de-noising method.
Collapse
|
12
|
Sawada A, Yoda K, Numano M, Futami Y, Yamashita H, Murayama S, Tsugami H. Patient positioning method based on binary image correlation between two edge images for proton-beam radiation therapy. Med Phys 2005; 32:3106-11. [PMID: 16279062 DOI: 10.1118/1.2042247] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A new technique based on normalized binary image correlation between two edge images has been proposed for positioning proton-beam radiotherapy patients. A Canny edge detector was used to extract two edge images from a reference x-ray image and a test x-ray image of a patient before positioning. While translating and rotating the edged test image, the absolute value of the normalized binary image correlation between the two edge images is iteratively maximized. Each time before rotation, dilation is applied to the edged test image to avoid a steep reduction of the image correlation. To evaluate robustness of the proposed method, a simulation has been carried out using 240 simulated edged head front-view images extracted from a reference image by varying parameters of the Canny algorithm with a given range of rotation angles and translation amounts in x and y directions. It was shown that resulting registration errors have an accuracy of one pixel in x and y directions and zero degrees in rotation, even when the number of edge pixels significantly differs between the edged reference image and the edged simulation image. Subsequently, positioning experiments using several sets of head, lung, and hip data have been performed. We have observed that the differences of translation and rotation between manual positioning and the proposed method were within one pixel in translation and one degree in rotation. From the results of the validation study, it can be concluded that a significant reduction in workload for the physicians and technicians can be achieved with this method.
Collapse
Affiliation(s)
- Akira Sawada
- Advanced Technology R&D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi Hommachi Amagasaki 661-8661, Japan
| | | | | | | | | | | | | |
Collapse
|
13
|
Verellen D, Soete G, Linthout N, Van Acker S, De Roover P, Vinh-Hung V, Van de Steene J, Storme G. Quality assurance of a system for improved target localization and patient set-up that combines real-time infrared tracking and stereoscopic X-ray imaging. Radiother Oncol 2003; 67:129-41. [PMID: 12758249 DOI: 10.1016/s0167-8140(02)00385-7] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE The aim of this study is to investigate the positional accuracy of a prototype X-ray imaging tool in combination with a real-time infrared tracking device allowing automated patient set-up in three dimensions. MATERIAL AND METHODS A prototype X-ray imaging tool has been integrated with a commercially released real-time infrared tracking device. The system, consisting of two X-ray tubes mounted to the ceiling and a centrally located amorphous silicon detector has been developed for automated patient positioning from outside the treatment room prior to treatment. Two major functions are supported: (a) automated fusion of the actual treatment images with digitally reconstructed radiographs (DRRs) representing the desired position; (b) matching of implanted radio opaque markers. Measurements of known translational (up to 30.0mm) and rotational (up to 4.0 degrees ) set-up errors in three dimensions as well as hidden target tests have been performed on anthropomorphic phantoms. RESULTS The system's accuracy can be represented with the mean three-dimensional displacement vector, which yielded 0.6mm (with an overall SD of 0.9mm) for the fusion of DRRs and X-ray images. Average deviations between known translational errors and calculations varied from -0.3 to 0.6mm with a standard deviation in the range of 0.6-1.2mm. The marker matching algorithm yielded a three-dimensional uncertainty of 0.3mm (overall SD: 0.4mm), with averages ranging from 0.0 to 0.3mm and a standard deviation in the range between 0.3 and 0.4mm. CONCLUSIONS The stereoscopic X-ray imaging device integrated with the real-time infrared tracking device represents a positioning tool allowing for the geometrical accuracy that is required for conformal radiation therapy of abdominal and pelvic lesions, within an acceptable time-frame.
Collapse
Affiliation(s)
- Dirk Verellen
- Department of Radiotherapy, Oncologic Center, Academic Hospital, Free University of Brussels, Laarbeeklaan 101, B-1090, Brussels, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Phillips BL, Jiroutek MR, Tracton G, Elfervig M, Muller KE, Chaney EL. Thresholds for human detection of patient setup errors in digitally reconstructed portal images of prostate fields. Int J Radiat Oncol Biol Phys 2002; 54:270-7. [PMID: 12183001 DOI: 10.1016/s0360-3016(02)02944-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE Computer-assisted methods to analyze electronic portal images for the presence of treatment setup errors should be studied in controlled experiments before use in the clinical setting. Validation experiments using images that contain known errors usually report the smallest errors that can be detected by the image analysis algorithm. This paper offers human error-detection thresholds as one benchmark for evaluating the smallest errors detected by algorithms. Unfortunately, reliable data are lacking describing human performance. The most rigorous benchmarks for human performance are obtained under conditions that favor error detection. To establish such benchmarks, controlled observer studies were carried out to determine the thresholds of detectability for in-plane and out-of-plane translation and rotation setup errors introduced into digitally reconstructed portal radiographs (DRPRs) of prostate fields. METHODS AND MATERIALS Seventeen observers comprising radiation oncologists, radiation oncology residents, physicists, and therapy students participated in a two-alternative forced choice experiment involving 378 DRPRs computed using the National Library of Medicine Visible Human data sets. An observer viewed three images at a time displayed on adjacent computer monitors. Each image triplet included a reference digitally reconstructed radiograph displayed on the central monitor and two DRPRs displayed on the flanking monitors. One DRPR was error free. The other DRPR contained a known in-plane or out-of-plane error in the placement of the treatment field over a target region in the pelvis. The range for each type of error was determined from pilot observer studies based on a Probit model for error detection. The smallest errors approached the limit of human visual capability. The observer was told what kind of error was introduced, and was asked to choose the DRPR that contained the error. Observer decisions were recorded and analyzed using repeated-measures analysis of variance. RESULTS The thresholds of detectability averaged over all observers were approximately 2.5 mm for in-plane translations, 1.6 degrees for in-plane rotations, 1 degrees for out-of-plane rotations, and 8% change in magnification for out-of-plane translations along the central axis. When one inexperienced observer is excluded, the average threshold for change in magnification is 5%. Experienced observers tended to perform better, but differences between groups were not statistically significant. Thresholds were computed as averages over all observers. Because of the broad range of observer capabilities, some detection tasks were too difficult for some observers, leading to missing threshold values in our data analysis. The missing values were excluded from computation of the average thresholds reported above. The effect of the missing values is to bias the average values toward the best human performance. CONCLUSIONS Under favorable conditions, humans can detect small errors in setup geometry. The thresholds for error detection reported in this study are believed to represent rigorous but reasonable benchmarks that can be incorporated into studies evaluating algorithms for computer-assisted detection of setup errors in electronic portal images.
Collapse
Affiliation(s)
- Brooke L Phillips
- Department of Radiation Oncology, University of North Carolina, Chapel Hill, NC 27599-7512, USA
| | | | | | | | | | | |
Collapse
|
15
|
Van de Vondel I, Coppens L, Verellen D, Linthout N, Van Acker S, Storme G. Remote control for a stand-alone freely movable treatment couch with limitation system. Med Phys 2001; 28:2518-21. [PMID: 11797955 DOI: 10.1118/1.1418239] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
One of our linear accelerators is equipped with a free-movable treatment couch. An additional projects was to develop a system that first protects the free-movable couch against collisions, secondly build a remote control for moving the couch from outside the treatment room and finally implement this remote control/limitation system in an automatic position algorithm using an electronic portal image. The latter has been the subject of an on-going departmental investigation on intra-fractional correction of set-up errors. A few years ago, we developed a limitation system to protect both the table and the accelerator against collisions. In this paper we describe the second part of this project, the remote control system.
Collapse
Affiliation(s)
- I Van de Vondel
- Department of Radiotherapy, Oncologic Center, Free University Brussels (AZ-VUB), Belgium.
| | | | | | | | | | | |
Collapse
|
16
|
Abstract
Portal imaging is the acquisition of images with a radiotherapy beam. Imaging theory suggests that the quality of portal images could be much higher if the efficiency of the imaging media in detecting radiation could be improved. Introduction of new media (films and electronic portal imaging devices) has confirmed this by markedly increasing the quality of portal images. Images from these devices can then be used to verify a patient's treatment. Geometric verification requires the portal image to be registered with a reference image. Dosimetric verification requires the portal imager to be calibrated for dose. This review gives a brief overview of the current areas of interest in portal imaging: imaging theory; imaging media, film and electronic portal imaging devices; image registration; and dosimetry using these devices.
Collapse
Affiliation(s)
- K A Langmack
- Medical Physics Department, Lincoln County Hospital, Greetwell Road, Lincoln, UK
| |
Collapse
|
17
|
Nederveen AJ, Lagendijk JJ, Hofman P. Feasibility of automatic marker detection with an a-Si flat-panel imager. Phys Med Biol 2001; 46:1219-30. [PMID: 11324961 DOI: 10.1088/0031-9155/46/4/321] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Here we study automatic detection of implanted gold markers relative to the field boundary in portal images for on-line position verification. Portal images containing 1-2 MU were taken with an amorphous silicon flat-panel imager. The images were obtained with lateral field at 18 MV. Both the detection success rate and the localization accuracy of markers of 1.0 and 1.2 mm diameter were determined with the help of a marker detection method based on a marker extraction kernel. A method for determining a fiducial reference point related to the field boundary was developed. Detection success rates were 0.99, 0.90 and 0.95 for markers of 1.2 mm diameter and 5 mm length, 1.0 mm diameter and 5 mm length and 1.0 mm diameter and 10 mm length respectively. The localization accuracy appeared to be better than 0.3 mm. The reference point could be reproduced with an accuracy equal to 1 pixel (0.5 mm at isocentre) within one fraction. During the first few seconds of a treatment fraction the field edge was not stable, which appeared to be an effect of the motion of the radiation source. Thanks to the use an a-Si flat-panel imager, on-line position verification using implanted gold markers becomes clinically feasible. We can use a clinically acceptable marker diameter as small as 1.0 mm. These markers can be automatically detected in portal images obtained with 1-2 MU relative to a stable reference point related to the field boundary.
Collapse
Affiliation(s)
- A J Nederveen
- Department of Radiation Oncology, University Medical Center Utrecht, The Netherlands
| | | | | |
Collapse
|
18
|
Bel A, Petrascu O, Van de Vondel I, Coppens L, Linthout N, Verellen D, Storme G. A computerized remote table control for fast on-line patient repositioning: implementation and clinical feasibility. Med Phys 2000; 27:354-8. [PMID: 10718139 DOI: 10.1118/1.598838] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A computerized remote control for a Siemens ZXT treatment couch was implemented and its characteristics were investigated to establish its feasibility for on-line setup corrections, using portal imaging. Communication with the table was obtained by connecting it via a serial line to a work station. The treatment couch enables "goto" commands in the three main directions and around the isocenter. The accuracy of the movements after giving such a command was checked and the time for each movement was recorded. First, the movements into a single direction were studied (range of -4 to +4 cm and -4 degrees to +4 degrees). Each command was repeated four times. Second, the table was moved into the three main directions simultaneously. For this experiment a clinically relevant three-dimensional (3-D) normal distribution of shifts was used [N = 200, standard deviation (SD) 5 mm in the three main directions]. This latter experiment was done twice: without and with rotations (a distribution with SD 1 degrees). During the first experiment, with shifts into one direction, no systematic deviations were found. The overall accuracy of the shifts was 0.6 mm (1 SD) in each direction and 0.04 degrees (1 SD) for the rotations. The time required for a translation ranged between 4 and 13 s and for the rotation between 8 and 20 s. The second experiment with the 3-D distribution of setup errors yielded an error in the 3-D vector length equal to 0.96 mm (1 SD), independent of rotations. Shifts were performed in less than 11 s for 95% of the cases without rotations. When rotations were also performed, 95% of the movements finished in less than 16 s. In conclusion, the table movements are accurate and enable on-line setup corrections in daily clinical practice.
Collapse
Affiliation(s)
- A Bel
- AZ-VUB Radiotherapy Department, Brussels, Belgium.
| | | | | | | | | | | | | |
Collapse
|