Radiation dose and image quality in intraoperative CT (iCT) angiography of the brain with stereotactic head frames

  • Robert ForbrigEmail author
  • Lucas L. Geyer
  • Robert Stahl
  • Jun Thorsteinsdottir
  • Christian Schichor
  • Friedrich-Wilhelm Kreth
  • Maximilian Patzig
  • Moriz Herzberg
  • Thomas Liebig
  • Franziska Dorn
  • Christoph G. Trumm
Computed Tomography



Intraoperative CT (iCT) angiography of the brain with stereotactic frames is an integral part of navigated neurosurgery. Validated data regarding radiation dose and image quality in these special examinations are not available. We therefore investigated two iCT protocols in this IRB-approved study.


Retrospective analysis of patients, who received a cerebral stereotactic iCT angiography on a 128 slice CT scanner between February 2016 and December 2017. In group A, automated tube current modulation (ATCM; reference value 410 mAs) and automated tube voltage selection (reference value 120 kV) were enabled, and only examinations with a selected voltage of 120 kV were included. In group B, fixed parameters were applied (300 mAs, 120 kV). Radiation dose was measured by assessing the volumetric CT dose index (CTDIvol), dose length product (DLP) and effective dose (ED). Signal-to-noise ratio (SNR) and image noise were assessed for objective image quality, visibility of arteries and grey-white differentiation for subjective image quality.


Two hundred patients (n = 100 in each group) were included. In group A, median selected tube current was 643 mAs (group B, 300 mAs; p < 0.001). Median values of CTDIvol, DLP and ED were 91.54 mGy, 1561 mGy cm and 2.97 mSv in group A, and 43.15 mGy, 769 mGy cm and 1.46 mSv in group B (p < 0.001). Image quality did not significantly differ between groups (p > 0.05).


ATCM yielded disproportionally high radiation dose due to substantial tube current increase at the frame level, while image quality did not improve. Thus, ATCM should preferentially be disabled.

Key Points

• Automated tube current modulation (ATCM) yields disproportionally high radiation dose in intraoperative CT angiography of the brain with stereotactic head frames.

• ATCM does not improve overall image quality in these special examinations.

• ATCM is not yet optimised for CT angiography of the brain with major extracorporeal foreign materials within the scan range.


Brain Radiation dosage Neuronavigation Computed tomography angiography 



Automated dose modulation


Automated tube current modulation


Volumetric computed tomography dose index


Dose length product


Effective dose


O-(2-18F-fluoroethyl)-l-tyrosine positron emission tomography


Hounsfield unit


Intraoperative computed tomography


Metal artefact reduction


Standard deviation


Signal-to-noise ratio



Part of the data was presented orally at the ECR 2018 in Vienna, Austria, and the XXI Symposium Neuroradiologicum 2018 in Taipei, Taiwan.


The authors state that this work has not received any funding.

Compliance with ethical standards


The scientific guarantor of this publication is PD Dr. Christoph G. Trumm.

Conflict of interest

The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

PD Dr. Robert Stahl kindly provided statistical advice for this manuscript.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.


• retrospective

• diagnostic study

• performed at one institution


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Copyright information

© European Society of Radiology 2019

Authors and Affiliations

  • Robert Forbrig
    • 1
    Email author return OK on get
  • Lucas L. Geyer
    • 2
  • Robert Stahl
    • 3
  • Jun Thorsteinsdottir
    • 4
  • Christian Schichor
    • 4
  • Friedrich-Wilhelm Kreth
    • 4
  • Maximilian Patzig
    • 1
  • Moriz Herzberg
    • 1
  • Thomas Liebig
    • 1
  • Franziska Dorn
    • 1
  • Christoph G. Trumm
    • 5
  1. 1.Institute of NeuroradiologyUniversity Hospital, LMU MunichMunichGermany
  2. 2.Center of Radiology and NeuroradiologyKlinikum IngolstadtIngolstadtGermany
  3. 3.Department of RadiologyUniversity Hospital, LMU MunichMunichGermany
  4. 4.Department of NeurosurgeryUniversity Hospital, LMU MunichMunichGermany
  5. 5.Institute for Diagnostic and Interventional Radiology, Neuroradiology and Nuclear MedicineStädtisches Klinikum München HarlachingMunichGermany

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