Technical Note: Combination of multiple <scp>EPID</scp> imager layers improves image quality and tracking performance of low contrast‐to‐noise objects

Yip, Stephen; Rottmann, Joerg; Chen, Haijian; Morf, Daniel; Füglistaller, Rony; Star‐Lack, Josh; Zentai, George; Berbeco, R.

doi:10.1002/mp.12422

Cited by 10 publications

(7 citation statements)

References 21 publications

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“…The anticipated benefit of IGRT is realized basing on online confirmation of the registration at the time of radiotherapy. Megavoltage (MV) electronic portal imaging device (EPID) has been still widely used as an online verification tool for the treatment field and dosimetry in radiation therapy, although the emergence of kilovoltage (kV) imager mounted on a linear accelerator [1][2][3][4][5][6][7] .…”

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confidence: 99%

“…Some efforts have been committed to the improvement of EPID image quality through the amendments of detector design. Yip et al 2 attempted to improve the quality of EPID images with a combination of four conventional EPID layers, which made a significant enhancement of tracking accuracy of poorly visible objects. Masatsugu Hariu et al 14 improved the EPID image quality by reducing the Compton scattered photons estimated at each point through the Monte Carlo simulation.…”

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confidence: 99%

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A new registration algorithm of electronic portal imaging devices images based on the automatic detection of bone edges during radiotherapy

Chen

et al. 2020

Sci Rep

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The precision and efficiency of the registration of megavolt-level electronic portal imaging devices (EPID) images with the naked eye in the orthogonal window are reduced. This study aims to develop a new registration algorithm with enhanced accuracy and efficiency. Ten setup errors with different translation and rotation were simulated with the phantom. For each error, one set of simulated computer tomography images and EPID images were acquired and registered with the traditional and the new method. The traditional method was performed by two senior physicists with the Varian Offline Review software. The new method is basing on the comparison of the precise contours of the same bone structure in the digital reconstruction radiography images and the EPID images, and the contours were fitted with an automatic edge detection algorithm based on gradient images. The average error of the new method was decreased by 44.44%, 28.33%, 49.09% in the translation of X, Y, and Z axes (The traditional vs. the new: X axes, 0.45 mm vs. 0.25 mm; Y axes, 0.75 mm vs. 0.35 mm; Z axes, 0.55 mm vs. 0.28 mm), 42.86% and 40.48% in the rotation of X and Z axes (The traditional vs. the new: X axes, 0.49° vs. 0.28°; Z axes, 0.42° vs. 0.25°), respectively. The average elapsed time in the new method was reduced by 11.14% (The traditional vs. the new: 44 s vs. 39.1 s). The new registration method has significant advantages of accuracy and efficiency compared with the traditional method.

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confidence: 99%

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confidence: 99%

A new registration algorithm of electronic portal imaging devices images based on the automatic detection of bone edges during radiotherapy

Chen

et al. 2020

Sci Rep

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“…Toward approach (2), Yip et al. tried to enhance the quality of EPID images by a combination of four conventional EPID layers 13 . An example of approach (3), Hariu et al.…”

Section: Related Workmentioning

confidence: 99%

“…12 Toward approach (2), Yip et al tried to enhance the quality of EPID images by a combination of four conventional EPID layers. 13 An example of approach (3), Hariu et al reduced Compton scattered photons using Monte Carlo simulation to improve the EPID image quality. 14 Moreover, some studies focused on the development of high detective quantum efficiency (DQE) detector configurations, which may improve quality of EPID imaging.…”

Section: Related Workmentioning

confidence: 99%

Electronic portal image enhancement based on nonuniformity correction in wavelet domain

et al. 2022

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Electronic portal images are one of the most important tools to verify the ongoing radiotherapy treatment through comparison with a reference image generated during treatment planning. In this procedure, two images are geometrically matched by means of visible bone or other landmarks of interest such as implanted fiducials. However, the intrinsically poor contrast and low spatial resolution of portal images can limit image quality. Methods: In this study, we have provided a multiresolution approach to enhance the quality of portal images acquired from the pelvis treatment fields. The main idea behind this work aims at removing some of the image artifacts that conceal the anatomical information. For this purpose, we have applied the homomorphic filtering on the approximation sub-band of wavelet decomposition to enhance local information. Moreover, in order to sharpen the bone edges, wavelet detail sub-bands were weighted to amplify important image details in the reconstruction of the desired enhanced image. The most appropriate image quality measure was chosen according to the image's characteristics in the spatial domain. By considering the characteristics of portal images as the random and nonperiodic texture, high level of noise, and a nonuniform background, three suitable quality measures of images were assessed:edge content,measure of enhancement, and measure of enhancement by entropy. Results: The higher values of these measures indicate the quality improvement in the processed images through our proposed algorithm. Moreover, the subjective evaluation results indicate that the proposed multiresolution approach significantly enhances the perceived quality of images in comparison with original and the similar approach (p < 0.001). Conclusions: Our proposed wavelet-based enhancement algorithm successfully reduced image intensity nonuniformity and enhanced anatomical featured information, which drastically improved the objective metrics values. Subjective evaluation of enhanced image confirmed this quality improvement.

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“…Gantry‐mounted MV and kV imaging systems have been the primary equipment deployed to detect the tumor or implanted fiducials during delivery. Although significant progress has been made in tracking implanted fiducials, technical transfer from research laboratory to routine clinic has met resistance, often due to concerns of the morbidity associated with the implantation of fiducials . Directly localizing tumors without the implanted fiducials is more desirable and remains the ultimate goal .…”

Section: Introductionmentioning

confidence: 99%

Design and validation of a MV/kV imaging‐based markerless tracking system for assessing real‐time lung tumor motion

et al. 2018

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Purpose: Localizing lung tumors during treatment delivery is critical for managing respiratory motion, ensuring tumor coverage, and reducing toxicities. The purpose of this project is to develop a real-time system that performs markerless tracking of lung tumors using simultaneously acquired MV and kV images during radiotherapy of lung cancer with volumetric modulated arc therapy. Method: Continuous MV/kV images were simultaneously acquired during dose delivery. In the subsequent analysis, a gantry angle-specific region of interest was defined according to the treatment aperture. After removing imaging artifacts, processed MV/kV images were directly registered to the corresponding daily setup cone-beam CT (CBCT) projections that served as reference images. The registration objective function consisted of a sum of normalized cross-correlation, weighted by the contrast-to-noise ratio of each MV and kV image. The calculated 3D shifts of the tumor were corrected by the displacements between the CBCT projections and the planning respiratory correlated CT (RCCT) to generate motion traces referred to a specific respiratory phase. The accuracy of the algorithm was evaluated on both anthropomorphic phantom and patient studies. The phantom consisted of localizing a 3D printed tumor, embedded in a thorax phantom, in an arc delivery. In an IRB-approved study, data were obtained from VMAT treatments of two lung cancer patients with three electromagnetic (Calypso) beacon transponders implanted in airways near the lung tumor. Result: In the phantom study, the root mean square error (RMSE) between the registered and actual (programmed couch movement) target position was 1.2 mm measured by the MV/kV imaging system, which was smaller compared to the MV or kV alone, of 4.1 and 1.3 mm, respectively. In the patient study, the mean and standard deviation discrepancy between electromagnetic-based tumor position and the MV/KV-markerless approach was –0.2 ± 0.6 mm, 0.2 ± 1.0 mm, and – 1.2 ± 1.5 mm along the superior-inferior, anterior-posterior, and left-right directions, respectively; resulting in a 3D displacement discrepancy of 2.0 ± 1.1 mm. Poor contrast around the tumor was the main contribution to registration uncertainties. Conclusion: The combined MV/kV imaging system can provide real-time 3D localization of lung tumor, with comparable accuracy to the electromagnetic-based system when features of tumors are detectable. Careful design of a registration algorithm and a VMAT plan that maximizes the tumor visibility are key elements for a successful MV/KV localization strategy.

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Technical Note: Combination of multiple EPID imager layers improves image quality and tracking performance of low contrast‐to‐noise objects

Abstract: Combination of four conventional EPID layers significantly improves the EPID image quality and tracking accuracy for a poorly visible object which is moving with a frequency and amplitude similar to respiratory motion.

Cited by 10 publications

References 21 publications

A new registration algorithm of electronic portal imaging devices images based on the automatic detection of bone edges during radiotherapy

A new registration algorithm of electronic portal imaging devices images based on the automatic detection of bone edges during radiotherapy

Electronic portal image enhancement based on nonuniformity correction in wavelet domain

Design and validation of a MV/kV imaging‐based markerless tracking system for assessing real‐time lung tumor motion

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