Consistent low‐contrast detectability for variable patient sizes and corresponding dose in abdominal CT

Zhou, Yifang; Nute, J; Scott, A. W.; Lee, Christina

doi:10.1002/mp.12085

Cited by 5 publications

(9 citation statements)

References 20 publications

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“…(b), smaller WED also results in smaller allowed relative error in the intercept (

| (b^{'} - b) / b |

). Thus, choosing a relatively small WED of 20 cm, as compared to choosing larger WED, such as that of typical adult abdomen (30 cm), can provide stricter criteria for evaluating the variability of calibration slope and intercept. This effect can be also seen from the narrow boundary lines based on 10‐cm Dw in Figs.…”

Section: Discussionmentioning

confidence: 99%

“…In comparison, AAPM Report‐220 designated a root mean square error level of 10% in WED estimation relative to the reference value as satisfying. In this study, we desired to examine the results with stricter standards, as WED is not only a key factor in the calculation of SSDE but also useful in the study and understanding of CT dose modulation, in various radiation dose calculation algorithms, and in CT protocol selection and optimization …”

Section: Discussionmentioning

confidence: 99%

“…Patient size is a crucial piece of information for accurate and individually tailored computed tomography (CT) imaging: scanners measure this information directly from localizer radiographs to guide dose modulation; radiation dosimetry algorithms require it for precise dose estimation, such as fetal dose and averaged absorbed dose; clinicians need to know patient size for selecting proper CT protocols for the trade‐off between diagnostic yield and patient radiation risks, and are increasingly interested in relative radiation doses when ordering radiologic examinations …”

Section: Introductionmentioning

confidence: 99%

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Estimating patient water equivalent diameter from CT localizer images – A longitudinal and multi‐institutional study of the stability of calibration parameters

Liu

Duan

et al. 2020

Medical Physics

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Purpose Water equivalent diameter (WED) is a robust patient‐size descriptor. Localizer‐based WED estimation is less sensitive to truncation errors resulting from limited field of view, and produces WED estimates at different locations within one localizer radiograph, prior to the initiation of axial scans. This method is considered difficult to implement by the clinical community due to the necessary calibration between localizer pixel values (LPV) and attenuation, and the unknown stability of calibration results across scanners and over time. We investigated the stability of calibration results across 25 computed tomography (CT) scanners from three medical centers, and their stability over 3 ∼ 29 months for 14 of those scanners. Methods Localizer and axial images of ACR and body computed tomography dose index phantoms were acquired, using routine clinical techniques (120 kV and lateral localizers) on each of the 25 CT scanners: 8 GE scanners (CT750HD, VCT, and Revolution), 8 Siemens scanners (Definition AS, Force, Flash, and Edge), 5 Canon scanners (Aquilion‐One, Aquilion‐Prime80, and Aquilion‐64), and 4 Philips scanners (iCT 256, iQon, and Ingenuity). By associating axial images with the corresponding localizer lines, the relationship between the scaled water equivalent area (WEA) and averaged LPV were established through regression analysis. Results Linear relationships between the scaled WEA and the averaged LPV were observed in all 25 CT scanners (R2>0.999). Calibration parameters were similar for CT scanners from the same vendor: the coefficients of variation (COV) were ≤ 1% in all four vendor groups for the calibration slope, and < 7% for the intercept. By analyzing the deviation of WED resulted from errors in the calibration slope or intercept alone, we derived the tolerance ranges for the slope or intercept for a given WED error level. The variation of slope and intercept from different CT scanners of the same vendor introduced <±2.5% error in the estimated WED for subjects of 20 and 30‐cm WED. The calibration parameters remained stable over time, with the maximum deviations all within the boundary values that introduce ±2.5% error in the estimated WED for subjects of 20 and 30‐cm WED. Conclusions The stability in calibration results among CT scanners of the same vendor and over time demonstrated the feasibility of implementing WED estimation for routine clinical use.

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“…(b), smaller WED also results in smaller allowed relative error in the intercept (

| (b^{'} - b) / b |

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimating patient water equivalent diameter from CT localizer images – A longitudinal and multi‐institutional study of the stability of calibration parameters

Liu

Duan

et al. 2020

Medical Physics

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“…These equations are based on our previous studies but made more general . We attempted to form a parametric model rather than a derivation from the first principle.…”

Section: Methodsmentioning

confidence: 99%

“…These equations are based on our previous studies but made more general. 14,15 We attempted to form a parametric model rather than a derivation from the first principle. Instead of using constant parameters for b 0 and b λ, 14 the dependence of Eqs.…”

Section: B | Quantitative Approachmentioning

confidence: 99%

Dose and blending fraction quantification for adaptive statistical iterative reconstruction based on low‐contrast detectability in abdomen CT

Zhou

2020

J Applied Clin Med Phys

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Purpose The utilization of iterative reconstruction makes it difficult to identify the dose‐noise relationship, resulting in empirical design of scan protocols and inconsistent conclusions on dose reduction for consistent image quality. This study was to quantitatively determine the dose and the blending fraction of adaptive statistical iterative reconstruction (ASIR) based on the specified low‐contrast detectability (LCD). Methods A tissue equivalent abdomen phantom and a GE discovery 750 HD computed tomography (CT) were utilized. The normality of the noise distribution was tested at various spatial scales (2.1–9.8 mm) in the presence of ASIR (10–100%) with a wide range of doses (2.24–38 mGy). The statically defined minimum detectable contrast (MDC) was used as the image quality metric. The parametric model decomposed the MDC into two terms: one with and the other without ASIR, each was related to the dose in the form of power law with factors and indices dependent on spatial scales. The parameters were identified by least‐square fitting to the experimental data. By considering the constraint of the blending fraction in the range of [0, 1], the dose and ASIR blending fraction were determined for any specified low‐contrast detectability (LCD), quantified by the MDC at the concerned lesion size. Results It was verified that noise distribution is normal in the presence of ASIR. It was also found that the noises obtained from the subtractions of adjacent slices had an underestimate of 20% as compared to the ground truth noises, regardless of the spatial scale, pitch, or ASIR blending fraction. The least‐square fitting for the parametric model resulted in correlation coefficients from 0.905 to 0.996. The root‐mean‐square errors ranged from 1.27% to 7.15%. Conclusion The parametric model can be used to form a look‐up‐table for dose and ASIR blending fraction. The dose choices may be substantially limited in some cases depending on the required LCD.

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A Holistic Approach to CT Protocol and Dose Management

Eastman,

Pressman,

Roy

et al. 2024

Journal of the American College of Radiology

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Consistent low‐contrast detectability for variable patient sizes and corresponding dose in abdominal CT

Abstract: We have modeled and verified the relationship of the minimum detectable contrast to the patient size, the patient dose, and the lesion size from the images reconstructed with filtered backprojection. The findings can be useful for task-specific dose modulation on abdomen CT studies.

Cited by 5 publications

References 20 publications

Estimating patient water equivalent diameter from CT localizer images – A longitudinal and multi‐institutional study of the stability of calibration parameters

Estimating patient water equivalent diameter from CT localizer images – A longitudinal and multi‐institutional study of the stability of calibration parameters

Dose and blending fraction quantification for adaptive statistical iterative reconstruction based on low‐contrast detectability in abdomen CT

A Holistic Approach to CT Protocol and Dose Management

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