Effect of miscentering and low-dose protocols on contrast resolution in computed tomography head examination

Shaffiq Said Rahmat SM 1 , Abdul Karim MK 2 , Che Isa IN 3 , Abd Rahman MA 4 , Noor NM 5 , Hoong NK 6

Affiliations 

  • 1 Department of Radiology, National Cancer Institute, 4, Jalan P7, Presint 7, 62250, Putrajaya, Wilayah Persekutuan Putrajaya, Malaysia
  • 2 Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia. Electronic address: mkhalis@upm.edu.my
  • 3 Diagnostic Imaging and Radiotherapy Programme, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, 50300, Kuala Lumpur, Wilayah Persekutuan Kuala Lumpur, Malaysia
  • 4 Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia
  • 5 Department of Radiology, Faculty of Medicine, Universiti Putra Malaysia, 43400, Serdang, Selangor, Malaysia
  • 6 Department of Biomedical Imaging, Universiti of Malaya Medical Centre, 50603, Kuala Lumpur, Malaysia
Comput Biol Med, 2020 08;123:103840.
PMID: 32658782 DOI: 10.1016/j.compbiomed.2020.103840

Abstract

BACKGROUND: Unoptimized protocols, including a miscentered position, might affect the outcome of diagnostic in CT examinations. In this study, we investigate the effects of miscentering position during CT head examination on the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).

METHOD: We simulate the CT head examination using a water phantom with a standard protocol (120 kVp/180 mAs) and a low dose protocol (100 kVp/142 mAs). The table height was adjusted to simulate miscentering by 5 cm from the isocenter, where the height was miscentered superiorly (MCS) at 109, 114, 119, and 124 cm, and miscentered inferiorly (MCI) at 99, 94, 89, and 84 cm. Seven circular regions of interest were used, with one drawn at the center, four at the peripheral area of the phantom, and two at the background area of the image.

RESULTS: For the standard protocol, the mean CNR decreased uniformly as table height increased and significantly differed (p 

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