QAMaster: A new software framework for phantom‐based computed tomography quality assurance

BackgroundCBCT imaging with field of views (FOVs) exceeding the size of scans acquired in the conventional imaging geometry, i.e. with opposing source and detector, is of high clinical importance for many medical fields. A novel approach for enlarged FOV scanning with one full‐scan (EnFOV360) or two short‐scans (EnFOV180) using an O‐arm system arises from non‐isocentric imaging based on independent source and detector rotations.PurposeThe presentation, description, and experimental validation of this novel approach and the novel scanning techniques EnFOV360 and EnFOV180 for an O‐arm system forms the scope of this work.MethodsWe describe the EnFOV360, EnFOV180, and non‐isocentric imaging techniques for the acquisition of laterally extended FOVs. For their experimental validation, scans of dedicated quality assurance as well as anthropomorphic phantoms were acquired, with the phantoms being placed both within the tomographic plane and at the longitudinal FOV border with and without lateral shifts from the gantry center. Based on this, geometric accuracy, contrast‐noise‐ratio (CNR) of different materials, spatial resolution, noise characteristics, as well as CT number profiles were quantitatively assessed. Results were compared to scans performed with the conventional imaging geometry.ResultsWith EnFOV360 and EnFOV180, we increased the in‐plane size of acquired FOVs from 250 × 250 mm2 obtained for the conventional imaging geometry to up to 400 × 400 mm2 for the performed measurements. Geometric accuracy was very high for all scanning techniques with mean values ≤0.21 ± 0.11 mm. CNR and spatial resolution were comparable between isocentric and non‐isocentric full‐scans as well as EnFOV360, whereas substantial image quality deteriorations in this respect were observed for EnFOV180. Image noise in the isocenter was lowest for conventional full‐scans with 13.4 ± 0.2 HU. For laterally shifted phantom positions, noise increased for conventional scans and EnFOV360, whereas noise reductions were observed for EnFOV180. Considering the anthropomorphic phantom scans, both EnFOV360 and EnFOV180 were comparable to conventional full‐scans.ConclusionBoth enlarged FOV techniques have high potential for imaging laterally extended FOVs. EnFOV360 revealed an image quality comparable to conventional full‐scans in general. EnFOV180 showed an inferior performance particularly regarding CNR and spatial resolution.

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“…A circular region of interest (ROI) was created both within and in the module background adjacent to each insert. The CNR was calculated to 29,30

\begin{equation}CN{R_{insert}} = \frac{{\left| {RO{I_{bkg}} - RO{I_{insert}}} \right|}}{{\sqrt {\frac{1}{2}. ({\sigma _{bkg}}^2 + {\sigma _{insert}}^2)} }}\end{equation}

…”

Section: Methodsmentioning

confidence: 99%

“…The total image noise was obtained by integrating the NPS. QAMaster as well as the exact procedure for NPS calculation and integration has been described in detail by Karius et al 29 …”

Section: Methodsmentioning

confidence: 99%

Cone‐beam CT imaging with laterally enlarged field of view based on independently movable source and detector

et al. 2023

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“…The four rods on the central slice of the module CTP404 (Figure 2a) were detected via thresholding by using the software QAMaster 18 . The software determines the side and diagonal lengths of the rod quadrilateral as Euclidean distances between the corresponding centers and compares them to manufacturer's specifications.…”

Section: Methodsmentioning

confidence: 99%

“…A circular ROI was positioned within each CTP404 insert, and the respective mean CT numbers

C{T_{insert}}

were measured. The ROIs had a radius 1 mm smaller than the insert radius to account for CT‐number fluctuations at the insert edges18.…”

Section: Methodsmentioning

confidence: 99%

Quality assurance and long‐term stability of a novel 3‐in‐1 X‐ray system for brachytherapy

Karius

Szkitsak

Boronikolas

et al. 2022

J Applied Clin Med Phys

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Purpose: A novel, mobile 3-in-1 X-ray system featuring radiography, fluoroscopy, and cone-beam computed tomography (CBCT) has been launched for brachytherapy recently. Currently, there is no quality assurance (QA) procedure explicitly applicable to this system equipped with innovative technologies such as dynamic jaws and motorized lasers. We developed a dedicated QA procedure and, based on its performance for a duration of 6 months, provide an assessment of the device's stability over time. Methods: With the developed QA procedure, we assessed the system's planar and CBCT-imaging performance by investigating geometric accuracy, CTnumber stability, contrast-noise-ratio, uniformity, spatial resolution, low-contrast detectability, dynamic range, and X-ray exposure using dedicated phantoms. Furthermore, we evaluated geometric stability by using the flexmap-approach and investigated the device's laser-and jaw-positioning accuracy with an in-house test phantom. CBCT-and planar-imaging protocols for pelvis, breast, and abdomen imaging were examined. Results: Planar-and CBCT-imaging performances were widely stable with a geometric accuracy ≤1 mm, CT-number stability of up to 46 HU, and uniformity variations of up to 48 HU over time. For planar imaging, low-contrast detectability and dynamic range exceeded current recommendations. Although geometric stability was considered tolerable, partly substantial positioning inaccuracies of up to more than 120 mm and −13 mm were obtained for lasers and jaws, respectively. X-ray exposure showed small variations of ≤0.56 µGy and ≤0.76 mGy for planar-and CBCT-imaging, respectively. The conductance of the QA procedure allowed a smooth evaluation of the system's overall performance. Conclusion:We developed a QA workflow for a novel 3-in-1 X-ray system allowing to assess the device's imaging and hardware performance. The system showed in general a reasonable imaging performance and stability over time, whereas improvements regarding laser and jaw accuracy are strictly required.

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“…Therefore, it is necessary to carry out further studies on this issue. The development of automatic measurements on AAPM CT performance phantom for all measurement parameters other than SSP (such as noise [25], low-contrast detectability [21], mechanical alignment, beam hardening, spatial resolution [26], HU linearity [27], and so on) may give great benefit to medical physicists in implementing quality control programs. Nevertheless, it still poses a challenge for future studies.…”

Section: Field Of View Variationmentioning

confidence: 99%

An evaluation of automated measurement of slice sensitivity profile of computed tomography image: field of view variations

Widyanti

Anam²,

Hidayanto³

et al. 2023

IJEECS

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This study aims to evaluate the automated measurement of slice sensitivity profile (SSP) on the American Association of Physicists in Medicine (AAPM) computed tomography (CT) performance phantom for variations of slice thickness and field of view (FOV). The AAPM CT performance phantom was scanned using a Philips MRC 880 CT Scanner for variations of slice thickness and FOV. The slice thickness values were 1, 3, and 5 mm. The FOV values were 240, 300, 340, 400, and 440 mm. The automated SSPs and their fullwidth at half maximums (FWHMs) were automatically measured from the middle stair object of the phantom. To validate the automated measurement results, the FWHM values of SSPs obtained were compared to those from manual measurements. The differences between FWHMs from automated measurements and set slice thicknesses are less than 0.3 mm, while the differences between FWHMs from automated and manual measurements are less than 0.2 mm. The results from automated measurements are closer to the set slice thickness than those from manual measurements. This automated SSP measurement provides high accuracy and precision for both the slice thickness and the FOV variations.

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QAMaster: A new software framework for phantom‐based computed tomography quality assurance

Cited by 12 publications

References 14 publications

Cone‐beam CT imaging with laterally enlarged field of view based on independently movable source and detector

Cone‐beam CT imaging with laterally enlarged field of view based on independently movable source and detector

Quality assurance and long‐term stability of a novel 3‐in‐1 X‐ray system for brachytherapy

An evaluation of automated measurement of slice sensitivity profile of computed tomography image: field of view variations

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