Cone beam X-ray scatter removal via image frequency modulation and filtering

Maltz, Jonathan S.; Blanz, W. E.; Hristov, Dimitre; Bani‐Hashemi, A

doi:10.1109/iembs.2005.1616811

Cited by 25 publications

(17 citation statements)

References 5 publications

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“…The measured signal was then extended to the entire projection plane via interpolation (Yan et al , 2010). A primary modulation method (Bani-Hashemi et al , 2005; Maltz et al , 2006; Zhu et al , 2006; Gao et al , 2010) was developed to extract the low-frequency scatter signal from the Fourier domain. However, these methods generally require extra hardware, which hinders their practicality.…”

Section: Introductionmentioning

confidence: 99%

A practical cone-beam CT scatter correction method with optimized Monte Carlo simulations for image-guided radiation therapy

et al. 2015

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Cone-beam CT (CBCT) has become the standard image guidance tool for patient setup in image-guided radiation therapy. However, due to its large illumination field, scattered photons severely degrade its image quality. While kernel-based scatter correction methods have been used routinely in the clinic, it is still desirable to develop Monte Carlo (MC) simulation-based methods due to their accuracy. However, the high computational burden of the MC method has prevented routine clinical application. This paper reports our recent development of a practical method of MC-based scatter estimation and removal for CBCT. In contrast with conventional MC approaches that estimate scatter signals using a scatter-contaminated CBCT image, our method used a planning CT image for MC simulation, which has the advantages of accurate image intensity and absence of image truncation. In our method, the planning CT was first rigidly registered with the CBCT. Scatter signals were then estimated via MC simulation. After scatter signals were removed from the raw CBCT projections, a corrected CBCT image was reconstructed. The entire workflow was implemented on a GPU platform for high computational efficiency. Strategies such as projection denoising, CT image downsampling, and interpolation along the angular direction were employed to further enhance the calculation speed. We studied the impact of key parameters in the workflow on the resulting accuracy and efficiency, based on which the optimal parameter values were determined. Our method was evaluated in numerical simulation, phantom, and real patient cases. In the simulation cases, our method reduced mean HU errors from 44 HU to 3 HU and from 78 HU to 9 HU in the full-fan and the half-fan cases, respectively. In both the phantom and the patient cases, image artifacts caused by scatter, such as ring artifacts around the bowtie area, were reduced. With all the techniques employed, we achieved computation time of less than 30 sec including the time for both the scatter estimation and CBCT reconstruction steps. The efficacy of our method and its high computational efficiency make our method attractive for clinical use.

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Section: Introductionmentioning

confidence: 99%

A practical cone-beam CT scatter correction method with optimized Monte Carlo simulations for image-guided radiation therapy

et al. 2015

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“…Recently, many methods of scatter reduction and compensation for CT have been proposed, which could be summarized as hardware methods [7][8][9], software methods [10][11][12][13] and hybrid methods [3,[14][15][16][17][18]. Hardware methods are based on simplified equipments set up on CT, for example, X-ray beam collimator and beam metal filter.…”

Section: Introductionmentioning

confidence: 99%

A hybrid scatter correction method for cone-beam CT

Zhang

Yan

et al. 2010

2010 3rd International Conference on Biomedical Engineering and Informatics

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There's great influence on the reconstructed image by X-ray scatter in cone-beam computed tomography (CBCT). X-ray scatter correction technique is one of the hot research fields in 3D imaging of CBCT. A hybrid scatter correction method is proposed, which combines the beam attenuation grid and the beam stop block. Combined with the scatter correction equipments, a scatter correction algorithm is designed to reduce the X-ray scatter in this paper. The scatter correction performance is investigated by real experiments with an industrial metallic bolt. The results showed that the proposed method could more effectively suppress the scatter artifacts than which based on an attenuation grid alone.

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“…Most scatter correction methods can be categorized as being based either on estimating scatter using computational models [6][7][8][9][10][11][12][13][14] or measuring scatter in situ. [15][16][17][18][19][20] Methods for measuring scatter in situ include collimator shadowing, 15 beam stop arrays, 16 dual scans, 17,18 and primary beam modulation. 19,20 While these techniques can be very accurate, they may also have practical limitations such as requiring extra imaging time, additional hardware, reducing the fieldof-view ͑FOV͒, or being susceptible to patient motion and mechanical instabilities.…”

Section: Introductionmentioning

confidence: 99%

“…[15][16][17][18][19][20] Methods for measuring scatter in situ include collimator shadowing, 15 beam stop arrays, 16 dual scans, 17,18 and primary beam modulation. 19,20 While these techniques can be very accurate, they may also have practical limitations such as requiring extra imaging time, additional hardware, reducing the fieldof-view ͑FOV͒, or being susceptible to patient motion and mechanical instabilities. Hence, the trend remains toward using computational methods.…”

Section: Introductionmentioning

confidence: 99%

Correction for patient table‐induced scattered radiation in cone‐beam computed tomography (CBCT)

et al. 2011

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Purpose: In image-guided radiotherapy, an artifact typically seen in axial slices of x-ray cone-beam computed tomography ͑CBCT͒ reconstructions is a dark region or "black hole" situated below the scan isocenter. The authors trace the cause of the artifact to scattered radiation produced by radiotherapy patient tabletops and show it is linked to the use of the offset-detector acquisition mode to enlarge the imaging field-of-view. The authors present a hybrid scatter kernel superposition ͑SKS͒ algorithm to correct for scatter from both the object-of-interest and the tabletop. Methods: Monte Carlo simulations and phantom experiments were first performed to identify the source of the black hole artifact. For correction, a SKS algorithm was developed that uses separate kernels to estimate scatter from the patient tabletop and the object-of-interest. Each projection is divided into two regions, one defined by the shadow cast by the tabletop on the imager and one defined by the unshadowed region. The region not shadowed by the tabletop is processed using the recently developed fast adaptive scatter kernel superposition ͑fASKS͒ method which employs asymmetric kernels that best model scatter transport through bodylike objects. The shadowed region is convolved with a combination of slab-derived symmetric SKS kernels and asymmetric fASKS kernels. The composition of the hybrid kernels is projection-angle-dependent. To test the algorithm, pelvis phantom and in vivo data were acquired using a CBCT test stand, a Varian Acuity simulator, and a Varian On-Board Imager, all of which have similar geometries and components. Artifact intensities and Hounsfield unit ͑HU͒ accuracies in the reconstructions were assessed before and after the correction. Results: The hybrid kernel algorithm provided effective correction and produced substantially better scatter estimates than the symmetric SKS or asymmetric fASKS methods alone. HU nonuniformities in the reconstructed pelvis phantom were reduced from 220 to 50 HU ͑i.e., 22%-5%͒. In the in vivo scans, the black hole artifact was reduced by up to 147 HU, a 73% improvement, and anatomical details in the prostate and rectum areas were made considerably more visible. Conclusions: Radiotherapy tabletops, which are generally flatter and larger than those used for diagnostic CT, can produce significant scatter-related artifacts. The proposed hybrid SKS algorithm accurately estimates scatter from both the object-of-interest and the patient tabletop, and resulting image uniformities and HU accuracies are greatly improved.

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Cone beam X-ray scatter removal via image frequency modulation and filtering

Cited by 25 publications

References 5 publications

A practical cone-beam CT scatter correction method with optimized Monte Carlo simulations for image-guided radiation therapy

A practical cone-beam CT scatter correction method with optimized Monte Carlo simulations for image-guided radiation therapy

A hybrid scatter correction method for cone-beam CT

Correction for patient table‐induced scattered radiation in cone‐beam computed tomography (CBCT)

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