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Low kilovoltage computed tomography to reduce contrast medium dose in patients at risk of acute kidney injury

Holmquist, Fredrik LU (2021) In Lund University, Faculty of Medicine Doctoral Dissertation Series
Abstract
Background: Patients with reduced renal function may be at risk of contrast medium-induced acute kidney injury
(CI-AKI) following intravenous iodine contrast medium (CM) enhanced computed tomography (CT). Reducing the
CM dose may reduce this risk. Decreasing the X-ray tube potential (kilovoltage, kV) from commonly used 120 to
80 kV results in higher CM attenuation due to the photoelectric properties of iodine, which may permit reduction
of the iodine dose while keeping the attenuation unchanged. Lower tube potential, however, increases image
noise which may be controlled by increasing the X-ray tube loading (milliampere seconds, mAs) to keep image
quality, e.g. contrast-to-noise ratio (CNR) unchanged. Complete... (More)
Background: Patients with reduced renal function may be at risk of contrast medium-induced acute kidney injury
(CI-AKI) following intravenous iodine contrast medium (CM) enhanced computed tomography (CT). Reducing the
CM dose may reduce this risk. Decreasing the X-ray tube potential (kilovoltage, kV) from commonly used 120 to
80 kV results in higher CM attenuation due to the photoelectric properties of iodine, which may permit reduction
of the iodine dose while keeping the attenuation unchanged. Lower tube potential, however, increases image
noise which may be controlled by increasing the X-ray tube loading (milliampere seconds, mAs) to keep image
quality, e.g. contrast-to-noise ratio (CNR) unchanged. Complete compensation of tube loading increases the
radiation dose to the patient, but the introduction of noise reducing iterative reconstruction algorithms may prevent
this.

Aim: To investigate if low-kV CT with reduced CM doses is a feasible alternative in examinations of the thorax
and abdomen in patients considered at risk of CI-AKI.

Material and methods: In three cross-sectional studies 80-kV CT protocols with 40-50% reduction of CM dose
and increased tube loading to control image noise was compared with standard 120-kV protocols, in two studies
to diagnose pulmonary embolism and in one hepatic study. Based on a phantom study and a clinical hepatic CT
study, iterative reconstruction algorithms were used to control image noise with no increase in tube loading. Image
quality was evaluated objectively and subjectively.

Results: Using 80-kV CT protocols with reduced CM doses (40-50%) and mAs compensation seems to provide
satisfactory diagnostic quality in pulmonary CT angiography and hepatic CT for patients with GFR <45-50 mL/min
and a body mass index <30 kg/m2. However, the use of iterative reconstruction algorithms to control image noise
without increased mAs resulted in inferior subjective image quality.

Conclusion: Using low-kV CT protocols with reduced CM dose could benefit patients at risk of CI-AKI. The
usefulness of iterative reconstruction algorithms to control image noise and not increase radiation dose remains
unclear. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Docent Bjerner, Tomas, Consultant at Department of Surgical Sciences, Radiology, Uppsala University
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Computed tomography, Image quality, Radiation dosimetry, contrast medium induced nephropathy, Iterative reconstruction algorithms
in
Lund University, Faculty of Medicine Doctoral Dissertation Series
issue
2021:13
pages
79 pages
publisher
Lund University, Faculty of Medicine
defense location
Biblioteket, plan 4, Bild och Funktion, Skånes universitetssjukhus i Lund
defense date
2021-02-12 09:00:00
ISSN
1652-8220
ISBN
978-91-8021-019-5
language
English
LU publication?
yes
id
35491e80-d692-4b0e-8392-333c7d640ecd
date added to LUP
2021-01-07 23:08:12
date last changed
2021-01-21 12:23:37
@phdthesis{35491e80-d692-4b0e-8392-333c7d640ecd,
  abstract     = {Background: Patients with reduced renal function may be at risk of contrast medium-induced acute kidney injury<br>
(CI-AKI) following intravenous iodine contrast medium (CM) enhanced computed tomography (CT). Reducing the<br>
CM dose may reduce this risk. Decreasing the X-ray tube potential (kilovoltage, kV) from commonly used 120 to<br>
80 kV results in higher CM attenuation due to the photoelectric properties of iodine, which may permit reduction<br>
of the iodine dose while keeping the attenuation unchanged. Lower tube potential, however, increases image<br>
noise which may be controlled by increasing the X-ray tube loading (milliampere seconds, mAs) to keep image<br>
quality, e.g. contrast-to-noise ratio (CNR) unchanged. Complete compensation of tube loading increases the<br>
radiation dose to the patient, but the introduction of noise reducing iterative reconstruction algorithms may prevent<br>
this.<br>
<br>
Aim: To investigate if low-kV CT with reduced CM doses is a feasible alternative in examinations of the thorax<br>
and abdomen in patients considered at risk of CI-AKI.<br>
<br>
Material and methods: In three cross-sectional studies 80-kV CT protocols with 40-50% reduction of CM dose<br>
and increased tube loading to control image noise was compared with standard 120-kV protocols, in two studies<br>
to diagnose pulmonary embolism and in one hepatic study. Based on a phantom study and a clinical hepatic CT<br>
study, iterative reconstruction algorithms were used to control image noise with no increase in tube loading. Image<br>
quality was evaluated objectively and subjectively.<br>
<br>
Results: Using 80-kV CT protocols with reduced CM doses (40-50%) and mAs compensation seems to provide<br>
satisfactory diagnostic quality in pulmonary CT angiography and hepatic CT for patients with GFR &lt;45-50 mL/min<br>
and a body mass index &lt;30 kg/m2. However, the use of iterative reconstruction algorithms to control image noise<br>
without increased mAs resulted in inferior subjective image quality.<br>
<br>
Conclusion: Using low-kV CT protocols with reduced CM dose could benefit patients at risk of CI-AKI. The<br>
usefulness of iterative reconstruction algorithms to control image noise and not increase radiation dose remains<br>
unclear.},
  author       = {Holmquist, Fredrik},
  isbn         = {978-91-8021-019-5},
  issn         = {1652-8220},
  language     = {eng},
  number       = {2021:13},
  publisher    = {Lund University, Faculty of Medicine},
  school       = {Lund University},
  series       = {Lund University, Faculty of Medicine Doctoral Dissertation Series},
  title        = {Low kilovoltage computed tomography to reduce contrast medium dose in patients at risk of acute kidney injury},
  url          = {https://lup.lub.lu.se/search/ws/files/89683396/e_spik_ex_Fredrik.pdf},
  year         = {2021},
}