Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT

McCollough, Cynthia H.; Bakalyar, Donovan; Bostani, Maryam; Brady, Samuel L.; Boedeker, Kirsten; Boone, John M.; Chen-Mayer, Huaiyu H.; Christianson, Olav; Leng, Shuai; Li, Baojun; McNitt‐Gray, Michael F.; Nilsen, Roy; Supanich, Mark; Wang, Jia

doi:10.37206/146

Cited by 131 publications

(179 citation statements)

References 13 publications

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“…specific dose estimate (SSDE) conversion factors retrieved from Table I D in AAPM report no 220. 10,13 2.E. Statistical analysis HU keV , I Meas , and Z eff results were expressed as mean AE standard deviation (SD) values.…”

Section: D Effective Dose Estimationmentioning

confidence: 99%

Fast kVp‐switching dual energy contrast‐enhanced thorax and cardiac CT: A phantom study on the accuracy of iodine concentration and effective atomic number measurement

Papadakis

Damilakis

2017

Medical Physics

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HU , I , and Z depend on several parameters such as body size, vessel size, exposure parameters, and reconstruction kernel. The limiting spatial resolution of the CT system results in considerable underestimation of HU , I , and Z in vessels smaller than 5 mm diameter. The underestimation of I uptake may be experimentally corrected, if the diameter of the investigated vessel is measured and the correction factors produced in this study are employed.

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Section: D Effective Dose Estimationmentioning

confidence: 99%

Fast kVp‐switching dual energy contrast‐enhanced thorax and cardiac CT: A phantom study on the accuracy of iodine concentration and effective atomic number measurement

Papadakis

Damilakis

2017

Medical Physics

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“…iterative methods (12)(13)(14)(15)(16)18). However, lowering dose for high-contrast, high-attenuation objects may not affect detection to the same degree or at all.…”

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confidence: 99%

Diagnostic Accuracy of CT Enterography for Active Inflammatory Terminal Ileal Crohn Disease: Comparison of Full-Dose and Half-Dose Images Reconstructed with FBP and Half-Dose Images with SAFIRE

Gandhi¹,

Baker²,

Goenka³

et al. 2016

Radiology

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Purpose To compare the diagnostic accuracy and image quality of computed tomographic (CT) enterographic images obtained at half dose and reconstructed with filtered back projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) with those of full-dose CT enterographic images reconstructed with FBP for active inflammatory terminal or neoterminal ileal Crohn disease. Materials and Methods This retrospective study was compliant with HIPAA and approved by the institutional review board. The requirement to obtain informed consent was waived. Ninety subjects (45 with active terminal ileal Crohn disease and 45 without Crohn disease) underwent CT enterography with a dual-source CT unit. The reference standard for confirmation of active Crohn disease was active terminal ileal Crohn disease based on ileocolonoscopy or established Crohn disease and imaging features of active terminal ileal Crohn disease. Data from both tubes were reconstructed with FBP (100% exposure); data from the primary tube (50% exposure) were reconstructed with FBP and SAFIRE strengths 3 and 4, yielding four datasets per CT enterographic examination. The mean volume CT dose index (CTDIvol) and size-specific dose estimate (SSDE) at full dose were 13.1 mGy (median, 7.36 mGy) and 15.9 mGy (median, 13.06 mGy), respectively, and those at half dose were 6.55 mGy (median, 3.68 mGy) and 7.95 mGy (median, 6.5 mGy). Images were subjectively evaluated by eight radiologists for quality and diagnostic confidence for Crohn disease. Areas under the receiver operating characteristic curves (AUCs) were estimated, and the multireader, multicase analysis of variance method was used to compare reconstruction methods on the basis of a noninferiority margin of 0.05. Results The mean AUCs with half-dose scans (FBP, 0.908; SAFIRE 3, 0.935; SAFIRE 4, 0.924) were noninferior to the mean AUC with full-dose FBP scans (0.908; P < .003). The proportion of images with inferior quality was significantly higher with all half-dose reconstructions than with full-dose FBP (mean proportion: 0.117 for half-dose FBP, 0.054 for half-dose SAFIRE 3, 0.054 for half-dose SAFIRE 4, and 0.017 for full-dose FBP; P < .001). Conclusion The diagnostic accuracy of half-dose CT enterography with FBP and SAFIRE is statistically noninferior to that of full-dose CT enterography for active inflammatory terminal ileal Crohn disease, despite an inferior subjective image quality. (©) RSNA, 2016 Online supplemental material is available for this article.

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“…Compared to the geometric-based metric, the attenuation based-metric is less practical due to its complexity but provides more accurate dose estimates especially for the thoracic (lung) region. 33 As shown in Subsection 3.B.2, narrow collimation imaging decreases the mean dose in the plane of maximum dose (z = 0) because it decreases total volume irradiated, and thus, reduces scattering impact on the central dose. Moreover, narrow collimator imaging increases detectability, because scattering then has less of an effect on image quality in body imaging.…”

Section: Discussionmentioning

confidence: 97%

“…32) and 220 (Ref. 33) introduced approaches for size-specific dose estimation (SSDE). They provide a conversion factor that translates CTDI vol into a patient-specific dose that is based on geometric patient size 32 and patient attenuation, 33 respectively.…”

Section: Discussionmentioning

confidence: 99%

“…33) introduced approaches for size-specific dose estimation (SSDE). They provide a conversion factor that translates CTDI vol into a patient-specific dose that is based on geometric patient size 32 and patient attenuation, 33 respectively. Compared to the geometric-based metric, the attenuation based-metric is less practical due to its complexity but provides more accurate dose estimates especially for the thoracic (lung) region.…”

Section: Discussionmentioning

confidence: 99%

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Practical dose point‐based methods to characterize dose distribution in a stationary elliptical body phantom for a cone‐beam C‐arm CT system

et al. 2015

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Purpose: To propose new dose point measurement-based metrics to characterize the dose distributions and the mean dose from a single partial rotation of an automatic exposure control-enabled, C-armbased, wide cone angle computed tomography system over a stationary, large, body-shaped phantom. Methods: A small 0.6 cm 3 ion chamber (IC) was used to measure the radiation dose in an elliptical body-shaped phantom made of tissue-equivalent material. The IC was placed at 23 well-distributed holes in the central and peripheral regions of the phantom and dose was recorded for six acquisition protocols with different combinations of minimum kVp (109 and 125 kVp) and z-collimator aperture (full: 22.2 cm; medium: 14.0 cm; small: 8.4 cm). Monte Carlo (MC) simulations were carried out to generate complete 2D dose distributions in the central plane (z = 0). The MC model was validated at the 23 dose points against IC experimental data. The planar dose distributions were then estimated using subsets of the point dose measurements using two proposed methods: (1) the proximity-based weighting method (method 1) and (2) the dose point surface fitting method (method 2). Twenty-eight different dose point distributions with six different point number cases (4,5,6,7,14, and 23 dose points) were evaluated to determine the optimal number of dose points and their placement in the phantom. The performances of the methods were determined by comparing their results with those of the validated MC simulations. The performances of the methods in the presence of measurement uncertainties were evaluated. Results: The 5-, 6-, and 7-point cases had differences below 2%, ranging from 1.0% to 1.7% for both methods, which is a performance comparable to that of the methods with a relatively large number of points, i.e., the 14-and 23-point cases. However, with the 4-point case, the performances of the two methods decreased sharply. Among the 4-, 5-, 6-, and 7-point cases, the 7-point case (1.0% [±0.6%] difference) and the 6-point case (0.7% [±0.6%] difference) performed best for method 1 and method 2, respectively. Moreover, method 2 demonstrated high-fidelity surface reconstruction with as few as 5 points, showing pixelwise absolute differences of 3.80 mGy (±0.32 mGy). Although the performance was shown to be sensitive to the phantom displacement from the isocenter, the performance changed by less than 2% for shifts up to 2 cm in the x-and y-axes in the central phantom plane. Conclusions: With as few as five points, method 1 and method 2 were able to compute the mean dose with reasonable accuracy, demonstrating differences of 1.7% (±1.2%) and 1.3% (±1.0%), respectively. A larger number of points do not necessarily guarantee better performance of the methods; optimal choice of point placement is necessary. The performance of the methods is sensitive to the alignment of the center of the body phantom relative to the isocenter. In body applications where dose distributions are important, method 2 is a better choice than method 1, as it reconstructs the do...

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Use of Water Equivalent Diameter for Calculating Patient Size and Size-Specific Dose Estimates (SSDE) in CT

Cited by 131 publications

References 13 publications

Fast kVp‐switching dual energy contrast‐enhanced thorax and cardiac CT: A phantom study on the accuracy of iodine concentration and effective atomic number measurement

Fast kVp‐switching dual energy contrast‐enhanced thorax and cardiac CT: A phantom study on the accuracy of iodine concentration and effective atomic number measurement

Diagnostic Accuracy of CT Enterography for Active Inflammatory Terminal Ileal Crohn Disease: Comparison of Full-Dose and Half-Dose Images Reconstructed with FBP and Half-Dose Images with SAFIRE

Practical dose point‐based methods to characterize dose distribution in a stationary elliptical body phantom for a cone‐beam C‐arm CT system

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