Evaluation and Clinical Application of a Commercially Available Iterative Reconstruction Algorithm for CBCT-Based IGRT

Abstract

Purpose:We have quantitatively evaluated the image quality of a new commercially available iterative cone-beam computed tomography reconstruction algorithm over standard cone-beam computed tomography image reconstruction results.Methods:This iterative cone-beam computed tomography reconstruction pipeline uses a finite element solver (AcurosCTS)-based scatter correction and a statistical (iterative) reconstruction in addition to a standard kernel-based correction followed by filtered back-projection-based Feldkamp-Davis-Kress cone-beam computed tomography reconstruction. Standard full-fan half-rotation Head, half-fan full-rotation Head, and standard Pelvis cone-beam computed tomography protocols have been investigated to scan a quality assurance phantom via the following image quality metrics: uniformity, HU constancy, spatial resolution, low contrast detection, noise level, and contrast-to-noise ratio. An anthropomorphic head phantom was scanned for verification of noise reduction. Clinical patient image data sets for 5 head/neck patients and 5 prostate patients were qualitatively evaluated.Results:Quality assurance phantom study results showed that relative to filtered back-projection-based cone-beam computed tomography, noise was reduced from 28.8 ± 0.3 HU to a range between 18.3 ± 0.2 and 5.9 ± 0.2 HU for Full-Fan Head scans, from 14.4 ± 0.2 HU to a range between 12.8 ± 0.3 and 5.2 ± 0.3 HU for Half-Fan Head scans, and from 6.2 ± 0.1 HU to a range between 3.8 ± 0.1 and 2.0 ± 0.2 HU for Pelvis scans, with the iterative cone-beam computed tomography algorithm. Spatial resolution was marginally improved while results for uniformity and HU constancy were similar. For the head phantom study, noise was reduced from 43.6 HU to a range between 24.8 and 13.0 HU for a Full-Fan Head and from 35.1 HU to a range between 22.9 and 14.0 HU for a Half-Fan Head scan. The patient data study showed that artifacts due to photon starvation and streak artifacts were all reduced, and image noise in specified target regions were reduced to 62% ± 15% for 10 patients.Conclusion:Noise and contrast-to-noise ratio image quality characteristics were significantly improved using the iterative cone-beam computed tomography reconstruction algorithm relative to the filtered back-projection-based cone-beam computed tomography method. These improvements will enhance the accuracy of cone-beam computed tomography-based image-guided applications.

A review of dose calculation approaches with cone beam CT in photon and proton therapy

“…Finally, the implementation of iterative reconstruction algorithms [14,15] and the introduction of machine learning techniques into the tomographic image reconstruction process [16] have more recently started being investigated to improve the image quality relative to FBP.…”

Machine log file-based dose verification using novel iterative CBCT reconstruction algorithm in commercial software during volumetric modulated arc therapy for prostate cancer patients

“…However, the conventional CBCT (FDK-CBCT) images are considered to pose problems related to HU nonuniformity and noise, as opposed to pCT. Novel CBCT (iCBCT) images have been proven to resolve these problems, as compared to FDK-CBCT images [13][14][15]. Moreover, machine log file-based CBCT calculation is a powerful way to assess the actually delivered 3D patient dose in patientspecific QA [10].…”

“…This advanced technique enables efficient scatter collection without additional manual interference, using Acuros CT scatter and statistical iterative reconstruction. Some researchers determined that iCBCT increases the contrast-to-noise ratio, maintains Hounsfield unit (HU) uniformity, and reduces streak and metal artifacts and image noise [13][14][15]. Gardner et al [14] reported an improved ability to delineate soft tissue structure by using iCBCT images.…”

Planning CT‐guided robust and fast cone‐beam CT scatter correction using a local filtration technique

“…Cone-beam CT (CBCT), an important imaging technique in the image-guided radiotherapy, [1][2][3][4] provides effective and flexible tools for patient setup 5,6 and potential tumor tracking. 7,8 However, the strong scatter signals in CBCT result in amplified image noise, 9 image non-uniformity 10 and degraded soft-tissue contrast, 11,12 greatly reducing image quality.…”