A study of the midpoint dose to CTDI vol ratio: Implications for CT dose evaluation

2017

Self Cite

Section: Discussionmentioning

confidence: 99%

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

2017

Self Cite

“…The calculations of the doses to water phantoms were based on the published data in two GEANT4‐based simulation studies . The simulation program modeled single x ray tube (A) acquisition on a SOMATOM Definition CT (Siemens Healthcare, Forchheim, Germany) with the manufacturer's specifications of the CT system.…”

Section: Methodsmentioning

confidence: 99%

“…It is worthwhile to note that water is approximately tissue equivalent . The previous results of the dependence of the dose to water or equivalent cylinder undergoing CT scans on phantom diameter are limited to the center of scan range . The CTDI vol to the size‐specific dose estimate (SSDE) conversion factors by AAPM Task Group 204 may be equivalent to the averaging results of scan lengths from 15 to 30 cm .…”

Section: Introductionmentioning

confidence: 99%

“…The dose integrals with an infinite integration length by Li et al are also related to the equilibrium dose . The CTDI L results of L = 5, 10, 20, 30 cm, and ∞ by Li et al are related to the midpoint dose or the equilibrium dose . In a human body, radiosensitive organs are located at various locations from the center to the peripheral region and in the height direction.…”

Section: Introductionmentioning

confidence: 99%

“…The comparison study might allow using water phantoms for assessing the influences of other factors, such as scan length and location away from the scan range center, on the relationship between organ dose and patient size. Based on the published dose calculation algorithms and data in three previous papers, water phantom‐based dose evaluations might be much easier than the patient model‐based simulations.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

2018

Self Cite

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.

Exam‐level dose monitoring in CT: Quality metric consideration for multiple series acquisitions

2019

Self Cite

Purpose: Multi-series CT examination is common in the clinic, but no metric is agreed upon to report the overall dose from such an examination. This work proposes a relevant metric for tracking patient dose from multi-series examinations and illustrates the evaluation method through explanatory examples. Materials and methods: In each acquisition series, a previously reported method was used to evaluate the cross-sectional average dose along the z-axis of a water phantom, with inputs of CTDI vol , scan length, tube current, and patient water-equivalent diameter. With a multi-series examination, the dose at each z-location was accumulated over all acquisition series. This method was applied to four clinical CT examinations. In three abdominal/pelvic examinations (patient weight, 107, 79, 79 kg), tube current modulation was applied in five acquisition series with scan lengths of 30-41.8 cm, while tube current was fixed in other series with short scan lengths (1.0, 7.9 cm). In another CT-guided liver ablation procedure (patient weight, 114 kg), 22 series were acquired with constant mA and scan lengths of 1-30 cm. The maximum value of the overall dose profile of each examination was compared to five dose quantities, including CTDI vol,sum and SSDE sum by the ACR CT Dose Index Registry, scan length-weighted CTDI vol and SSDE by a CT dose monitoring platform, and "max z location CTDI vol " by a CT manufacturer. Results: A simple graphic display of dose as a function of the z-axis location was presented for each acquisition series and for the whole examination. Differences up to 43.4% and 42.8%, or down to À93.5%, À93.5%, and À49.0%, were observed between the maximum value of the overall dose profile and five dose quantities (in the above order), respectively. Conclusion: The overall dose profile gives a complete description of z-axis dose distribution for the studied CT examinations under a wide range of patient variables and acquisition conditions, including multiple acquisition series. Simple visualization of the doses across and beyond the scan ranges may provide a new tool for CT dose optimization.