Crescent artifacts in cone‐beam CT

Giles, W; Bowsher, J.E.; Li, Hao; Yin, Fang‐Fang

doi:10.1118/1.3567508

Cited by 13 publications

(27 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It was reported that BCA were induced by translational position variation of either the BF or the radiation source (15),(16) . Similar to those studies, translational position variation of the BF during gantry rotation and its repeatability were investigated.…”

Section: Methodsmentioning

confidence: 99%

“…We applied the two previously proposed BCA correction strategies (15),(16) in our clinical CBCT system. Strategy A used a model to predict the BF position shift, and applied the shift for each gantry angle with an in-air BF projection to correct for the BF position variation (15) .…”

Section: Methodsmentioning

confidence: 99%

“…The BF was originally used to reduce the radiation dose to patients, and has been found to reduce the scatter in projection images and improve CBCT image quality (13),(14) . However, this alignment variation causes a variation in the BF projections during gantry rotation and induces a crescent-shaped band when the projections are reconstructed into CBCT images (15),(16) . This band is thus named the bowtie-filter crescent artifacts (BCA).…”

Section: Introductionmentioning

confidence: 99%

“…This band is thus named the bowtie-filter crescent artifacts (BCA). Research has been reported to reduce the BCA (15),(16) . One approach used a model to fit this variation measured by in-air blank scans, and consequently corrected this variation in the normalization process (15) .…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System

Zhang

Kong

Huang

et al. 2016

Technol Cancer Res Treat

View full text Add to dashboard Cite

Purpose To present our experiences in understanding and minimizing bowtie-filter (BF) crescent artifacts (BCA) and BF normalization artifacts (BNA) in a clinical cone beam computed tomography (CBCT) system. Methods BF position and profile variations during gantry rotation were studied. Two previously proposed strategies (A and B) were applied to the clinical CBCT system to correct BCA. Physical calibration and analytical approaches were used to minimize the norm phantom misalignment and to correct for BNA. A combined procedure to reduce BCA and BNA was proposed and tested on a norm phantom, CatPhan and a patient, and evaluated using standard deviation of Hounsfield-unit (HU) along a sample line. Results The BF exhibited not only a translational shift, but also an amplitude variation in its projection profile during gantry rotation. Strategy B was better than Strategy A slightly in minimizing BCA, possibly because it corrected the amplitude variation, suggesting that the amplitude variation plays a role in BCA. The physical calibration largely reduced the misalignment induced BNA, and the analytical approach further reduced BNA. The combined procedure minimized both BCA and BNA, with HU standard deviation being 63.2, 45.0, 35.0, and 18.8 HU for the best correction approaches of none, BCA, BNA, and BNA+BCA, respectively. The combined procedure also demonstrated reduction of BCA and BNA in a CatPhan and a patient. Conclusions We have developed a step-by-step procedure that can be directly used in clinical CBCT systems to minimize both BCA and BNA.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System

Zhang

Kong

Huang

et al. 2016

Technol Cancer Res Treat

View full text Add to dashboard Cite

show abstract

“…In a typical clinical CBCT system for radiotherapy scatter-to-primary ratio (SPR) may even exceed 100% (Siewerdsen and Jaffray, 2001), although many methods have been proposed to correct scatter artifacts (Siewerdsen et al, 2006;Rinkel et al, 2007;Maltz et al, 2008;Zhu et al, 2009b;Poludniowski et al, 2009;Yan et al, 2010;Meyer et al, 2010;Sun et al, 2011), it is still an open problem. Third, the gantry 35 mounted bowtie filter in CBCT system may wobble, as the gantry rotates, which can result in crescent artifacts (Giles et al, 2011;Zheng et al, 2011). Moreover, there are also other factors that contribute to the intensity inconsistency between CT and CBCT, e.g.…”

Section: Introductionmentioning

confidence: 99%

WE-E-213CD-04: CT to Cone-Beam CT Deformable Registration With Simultaneous Intensity Correction

Zhen

Hui

et al. 2012

Med. Phys.

View full text Add to dashboard Cite

15Computed tomography (CT) to cone-beam computed tomography (CBCT) deformable image registration (DIR) is a crucial step in adaptive radiation therapy. Current intensity-based registration algorithms, such as demons, may fail in the context of CT-CBCT DIR because of inconsistent intensities between the two modalities. In this paper, we propose a variant of demons, called Deformation with 20Intensity Simultaneously Corrected (DISC), to deal with CT-CBCT DIR. DISC distinguishes itself from the original demons algorithm by performing an adaptive intensity correction step on the CBCT image at every iteration step of the demons registration. Specifically, the intensity correction of a voxel in CBCT is achieved by matching the first and the second moments of the voxel intensities inside a patch 25 around the voxel with those on the CT image. It is expected that such a strategy can remove artifacts in the CBCT image, as well as ensuring the intensity consistency between the two modalities. DISC is implemented on computer graphics processing units (GPUs) in compute unified device architecture (CUDA) programming environment. The performance of DISC is evaluated on a simulated patient case and 30 six clinical head-and-neck cancer patient data. It is found that DISC is robust against the CBCT artifacts and intensity inconsistency and significantly improves the registration accuracy when compared with the original demons.

show abstract

Image artifacts caused by incorrect bowtie filters in cone‐beam CT image‐guided radiotherapy

Cao

Boer

et al. 2020

J Applied Clin Med Phys

View full text Add to dashboard Cite

Certain models of cone beam computed tomography (CBCT) image-guided radiotherapy (IGRT) systems require manually placing the appropriate bowtie filter according to the relevant imaging protocol. Inadvertently using a wrong bowtie filter or no bowtie filter could cause unexpected image artifacts. In this work, CBCT image artifact patterns caused by different bowtie filter placement were evaluated. CBCT images of CT phantoms, that is, a Body Norm phantom, a Catphan® phantom and an anthropomorphic RANDO® phantom, were acquired at a Varian Trilogy® unit with an On-Board Imager® (OBI) system. Three image acquisition protocols were evaluated. For Standard Head protocol, half-fan bowtie and no bowtie filter were studied for comparison with the correct full-fan bowtie acquisition. For Pelvis and Low-Dose Thorax protocols, full-fan bowtie and no bowtie were studied for comparison with the correct half-fan bowtie acquisition. In addition, the possibility of reversed direction half-fan bowtie was also discussed. All possible scenarios of bowtie filter misplacement caused distinct artifacts regardless of protocols. These artifact patterns are different from the characteristic crescent artifact when correct bowtie filter was placed. Based on the artifact patterns described in this study we recommend reviewing image artifacts at time of image acquisition. If unexpected artifacts appear in the CBCT images, one should verify the correct placement of the bowtie filter and retake the image if necessary. However, it should also be stressed that using a wrong bowtie filter or forgetting to place the bowtie filter can cause increased patient dose. It is always a good practice to verify the bowtie filter placement before acquiring CBCT images for image-guided radiotherapy.

show abstract

Crescent artifacts in cone‐beam CT

Abstract: Small deviations from an ideal geometry can result in crescent artifacts due to steep gradients in the bowtie filter. Angle-dependent blank projections can largely alleviate the artifacts.

Cited by 13 publications

References 8 publications

Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System

Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System

WE-E-213CD-04: CT to Cone-Beam CT Deformable Registration With Simultaneous Intensity Correction

Image artifacts caused by incorrect bowtie filters in cone‐beam CT image‐guided radiotherapy

Contact Info

Product

Resources

About