Equations for CT dose calculations on axial lines based on the principle of symmetry

2017

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“…. The results of constant mA were consistent with those of previous studies as follows:

D_{L} false(z false)

distribution was “bell shaped” and had scatter tails extending far away from the scanned range;

D_{L} false(z = 0 false)

asymptotically increased with scan length until reaching an equilibrium level; at smaller scan lengths (e.g., 10 or 28.6 cm),

D_{L} false(z = 0 false) / D_{e q}

was greater on the phantom peripheral axis than on the phantom central axis. With variable tube current, D

_{L}

(z) changed with mA(z) lineshape .…”

Section: Resultssupporting

confidence: 90%

“…Li et al . illustrated that the H(L)‐based

D_{L} false(z false)

calculation in Section is equivalent to the convolution‐based model,

D_{L} false(z false) \propto \int_{- L / 2}^{L / 2} i false(z^{'} false) \times f false(z - z^{'} false) d z^{'},

where i(z) is tube current distribution, and f(z) is the single rotation axial scan dose profile.…”

Section: Discussionmentioning

confidence: 99%

{normalD}_{normalL} false(normalz false) = \frac{D_{eq}}{2} false[normalH (L + 2 z) + normalH (L - 2 z) false] .

For the points outside the interval with

z = - L / 2 - {normald}_{normalz}

z = L / 2 + {normald}_{normalz}

(with

{normald}_{normalz} > 0

), the dose was computed by

{normalD}_{normalL} false(d_{z} false) = \frac{D_{eq}}{2} false[normalH (2 L + 2 {normald}_{normalz}) - normalH (2 {normald}_{normalz}) false] .

For a variable tube current profile, the scan length was divided into multiple (N) subscan lengths,

L = \sum_{k = 1}^{normalN} {normalL}_{normalk},

each of which was centered at

z_{k}

and was scanned to a nearly constant tube current

({normali}_{normalk})

. The dose at a point z, accumulated from the k‐th interval with a unit of tube current, was computed according to Eqs.…”

Section: Methodsmentioning

confidence: 99%

“…

D_{L} false(z false)

(water) would also characterize dose for various patient sizes, scan lengths, and tube current curves. Calculation of

D_{L} false(z false)

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Characterization of radiation dose from tube current modulated CT examinations with considerations of both patient size and variable tube current

Yang

2017

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“…(2) and (3)] is introduced not long ago. 4 Their joint use provides a powerful method for computing radiation dose in a shift-invariant medium, with either constant or variable tube current of any scan length. The results in Fig.…”

Section: Discussionmentioning

confidence: 99%

Radiation dose calculations for CT scans with tube current modulation using the approach to equilibrium function

Zhang

2014

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The described method provides an effective approach that takes into account subject size, scan length, and constant or variable tube current to evaluate CT dose to a shift-invariant medium. For a clinical CT scan, dose calculations may be performed with a water-containing cylinder whose cross-sectional mass is equal to that of the subject. This method has the potential to substantially improve evaluations of patient dose from clinical CT scans, compared to CTDIvol, size-specific dose estimate (SSDE), or the dose evaluated for a TCM scan with a constant tube current equal to the average tube current of the TCM scan.

Radiation dose dependence on subject size in abdominal computed tomography: Water phantom and patient model comparison

Yang

2018

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An efficient approach to take into account the abdominal organ dose dependences on other factors is to calculate D (z)(water) with the water equivalent diameter, scan length, and tube current lineshape from the patient examinations, and to evaluate the organ dose to D (z)(water) ratio, where z is at the organ's longitudinal location. The ratio may be used for abdominal organ dose evaluation in the patient examinations. How to make use of D (z)(water) for organ dose evaluation in other body regions may be explored in the future.