A database for estimating organ dose for coronary angiography and brain perfusion CT scans for arbitrary spectra and angular tube current modulation

Rupcich, Franco; Badal, Andreu; Kyprianou, Iacovos S.; Schmidt, Taly Gilat

doi:10.1118/1.4739243

Cited by 8 publications

(6 citation statements)

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“…A previous study using a different voxelized phantom suggests that 23% of the eye lens dose is deposited at angles of 50 • to 80 • away from the AP view. 26 Therefore, greater eye lens dose reduction may be possible by increasing the angular range of ODM dose reduction for head scans. The ODM settings investigated in this paper were designed for breast and eye dose reduction.…”

Section: Discussionmentioning

confidence: 99%

Technical Note: Phantom study to evaluate the dose and image quality effects of a computed tomography organ‐based tube current modulation technique

Gandhi

Crotty²,

Stevens³

et al. 2015

Medical Physics

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Purpose: This technical note quantifies the dose and image quality performance of a clinically available organ-dose-based tube current modulation (ODM) technique, using experimental and simulation phantom studies. The investigated ODM implementation reduces the tube current for the anterior source positions, without increasing current for posterior positions, although such an approach was also evaluated for comparison. Methods: Axial CT scans at 120 kV were performed on head and chest phantoms on an ODM-equipped scanner (Optima CT660, GE Healthcare, Chalfont St. Giles, England). Dosimeters quantified dose to breast, lung, heart, spine, eye lens, and brain regions for ODM and 3D-modulation (SmartmA) settings. Monte Carlo simulations, validated with experimental data, were performed on 28 voxelized head phantoms and 10 chest phantoms to quantify organ dose and noise standard deviation. The dose and noise effects of increasing the posterior tube current were also investigated. Results: ODM reduced the dose for all experimental dosimeters with respect to SmartmA, with average dose reductions across dosimeters of 31% (breast), 21% (lung), 24% (heart), 6% (spine), 19% (eye lens), and 11% (brain), with similar results for the simulation validation study. In the phantom library study, the average dose reduction across all phantoms was 34% (breast), 20% (lung), 8% (spine), 20% (eye lens), and 8% (brain). ODM increased the noise standard deviation in reconstructed images by 6%-20%, with generally greater noise increases in anterior regions. Increasing the posterior tube current provided similar dose reduction as ODM for breast and eye lens, increased dose to the spine, with noise effects ranging from 2% noise reduction to 16% noise increase. At noise equal to SmartmA, ODM increased the estimated effective dose by 4% and 8% for chest and head scans, respectively. Increasing the posterior tube current further increased the effective dose by 15% (chest) and 18% (head) relative to SmartmA. Conclusions: ODM reduced dose in all experimental and simulation studies over a range of phantoms, while increasing noise. The results suggest a net dose/noise benefit for breast and eye lens for all studied phantoms, negligible lung dose effects for two phantoms, increased lung dose and/or noise for eight phantoms, and increased dose and/or noise for brain and spine for all studied phantoms compared to the reference protocol.

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Section: Discussionmentioning

confidence: 99%

Technical Note: Phantom study to evaluate the dose and image quality effects of a computed tomography organ‐based tube current modulation technique

Gandhi

Crotty²,

Stevens³

et al. 2015

Medical Physics

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“…We used our previously proposed dose database 41 to estimate protocol-specific "dose conversion factors," which quantified the breast dose and lung dose per photon emitted from the source for each protocol. Because our dose database cannot model shielded scans, we performed Monte Carlo simulations (following the methods of Rupcich et al 41 ) of the female phantom with the shield described in Sec. 2.E to estimate the dose per photon emitted from the source for the shielded protocol.…”

Section: F Dose Estimationmentioning

confidence: 99%

Reducing radiation dose to the female breast during CT coronary angiography: A simulation study comparing breast shielding, angular tube current modulation, reduced kV, and partial angle protocols using an unknown‐location signal‐detectability metric

et al. 2013

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The 80 kV and 80 kV partial angle protocols demonstrated the greatest reduction to breast and lung dose, however, the subsequent increase in image noise may be deemed clinically unacceptable. Tube output for these protocols can be adjusted to achieve a more desirable noise level with lesser breast dose savings. Breast shielding increased breast and lung dose when maintaining equivalent ÂFE. The results demonstrated that comparisons of dose performance depend on both the image quality metric and the specific task, and that CNR may not be a reliable metric of signal detectability.

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“…Recently a number of research groups have investigated how tube current modulation (TCM) impacts dose and dose conversion coefficients (Huda et al 2008;van Straten et al 2009;Angel et al 2009aAngel et al , 2009bSchlattl et al 2010;Zanca et al 2011;Khatonabadi et al 2012Khatonabadi et al , 2013aRupcich et al 2012;Rendon et al 2013). For example, Schlattl and colleagues (Schlattl et al 2010) published h factors associated with TCM examinations for four adult phantoms and various examination types.…”

Section: Introductionmentioning

confidence: 99%

The impact on CT dose of the variability in tube current modulation technology: a theoretical investigation

Segars

Samei

2014

Phys. Med. Biol.

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Body CT scans are routinely performed using tube-current-modulation (TCM) technology. There is notable variability across CT manufacturers in terms of how TCM technology is implemented. Some manufacturers aim to provide uniform image noise across body regions and patient sizes, whereas others aim to provide lower noise for smaller patients. The purpose of this study was to conduct a theoretical investigation to understand how manufacturer-dependent TCM scheme affects organ dose, and to develop a generic approach for assessing organ dose across TCM schemes. The adult reference female extended cardiac-torso (XCAT) phantom was used for this study. A ray-tracing method was developed to calculate the attenuation of the phantom for a given projection angle based on phantom anatomy, CT system geometry, X-ray energy spectrum, and bowtie filter filtration. The tube current (mA) for a given projection angle was then calculated as a log-linear function of the attenuation along that projection. The slope of this function, termed modulation control strength, α, was varied from 0 to 1 to emulate the variability in TCM technology. Using a validated Monte Carlo program, organ dose was simulated for five α values (α = 0, 0.25, 0.5, 0.75, and 1) in the absence and presence of a realistic system mA limit. Organ dose was further normalized by volume-weighted CT dose index (CTDIvol) to obtain conversion factors (h factors) that are relatively independent of system specifics and scan parameters. For both chest and abdomen-pelvis scans and for 24 radiosensitive organs, organ dose conversion factors varied with α, following second-order polynomial equations. This result suggested the need for α-specific organ dose conversion factors (i.e., conversion factors specific to the modulation scheme used). On the other hand, across the full range of α values, organ dose in a TCM scan could be derived from the conversion factors established for a fixed-mA scan (hFIXED). This was possible by multiplying hFIXED by a revised definition of CTDIvol that accounts for two factors: (a) the tube currents at the location of an organ and (b) the variation in organ volume along the longitudinal direction. This α-generic approach represents an approximation. The error associated with this approximation was evaluated using the α-specific organ dose (i.e., the organ dose obtained by using α-specific mA profiles as inputs into the Monte Carlo simulation) as the reference standard. When the mA profiles were constrained by a realistic system limit, this α-generic approach had errors of less than ~20% for the full range of values. This was the case for 24 radiosensitive organs in both chest and abdomen-pelvis CT scans with the exception of thyroid in the chest scan and bladder in the abdomen-pelvis scan. For these two organs, the errors were less than ~40%. The results of this theoretical study suggested that knowing the mA modulation profile and the fixed-mA conversion factors, organ dose may be estimated for a TCM scan independent of the specific modulation sch...

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A database for estimating organ dose for coronary angiography and brain perfusion CT scans for arbitrary spectra and angular tube current modulation

Cited by 8 publications

References 50 publications

Technical Note: Phantom study to evaluate the dose and image quality effects of a computed tomography organ‐based tube current modulation technique

Technical Note: Phantom study to evaluate the dose and image quality effects of a computed tomography organ‐based tube current modulation technique

Reducing radiation dose to the female breast during CT coronary angiography: A simulation study comparing breast shielding, angular tube current modulation, reduced kV, and partial angle protocols using an unknown‐location signal‐detectability metric

The impact on CT dose of the variability in tube current modulation technology: a theoretical investigation

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