Effect of Arm Position on Image Quality and Radiation Dose in Multidetector Computed Tomography
Message:
Abstract:
Background

Abdominal CT using a tube-current modulation technique may result in artifacts due to changes in the position of
the patient’s arms, resulting in poor image quality and excessive radiation exposure. To solve these problems, the patient’s arm is
positioned mainly on the head or outside the examination area.

Objectives

An optimization method to acquire high-quality images in CT examination by comparing the radiation dose and image
according to the change in arm position and the use of the tube-current modulation method in CT examination.

Materials and Methods

To analyze the CT images, the mean, standard deviation (SD), and coefficient of variation (COV) of the
Hounsfield unit (HU) of the CT were obtained by measuring the pixel values of the heart, chest, lung, and bone using region of interest
(ROI) manage. The dose of computed tomography dose index (CTDI) and dose length product (DLP) according to the position
of the arm.

Results

The arms up position of CTDIvol and DLP values were lower than the armsdownposition. In the z-axis thickness modulation
(Z-DOM), the tube current increased in the shoulders, decreased in the lungs, and increased in the abdomen. There was no artifact
when the arms were raised, but an artifact was present when the arm was lowered. The calculated peak signal-to-noise ratio (PSNR)
for the Z-DOM application in the CT scan of the anthropomorphic phantom by applying automatic exposure control (AEC) was 38.21
dB. There was no significant difference between SD and COV using Z-DOM and the fixed tube current technique (P > 0.05). Noise in
the image increased when the arm was raised, and dose increased in the thyroid and upper chest.

Conclusion

The position of the upper arms directly affects the image in the MDCT imaging of the anthropomorphic phantom.
Therefore, it is possible to increase the quality of the image by reducing the amount of artifacts and the amount of radiation by
orienting the arms upward. This optimal test method could be used in clinical practice to achieve high image quality and low noise
in the MDCT of trauma patients.

Article Type:
Research/Original Article
Language:
English
Published:
Iranian Journal of Radiology, Volume:16 Issue:4, 2019
Page:
7
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