Evaluation of an organ-based tube current modulation tool in pediatric CT examinations

Antonios E Papadakis,John Damilakis

doi:10.1007/s00330-020-06888-5

Antonios E Papadakis, John Damilakis

Open Access

https://doi.org/10.1007/s00330-020-06888-5

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Abstract

ObjectivesTo investigate the effect of an organ-based tube current modulation (OTCM) technique on organ absorbed dose and assess image quality in pediatric CT examinations.MethodsFour physical anthropomorphic phantoms that represent the average individual as neonate, 1-year-old, 5-year-old, and 10-year-old were used. Standard head and thorax acquisitions were performed with automatic tube current modulation (ATCM) and ATCM+OTCM. Dose calculations were performed by means of Monte Carlo simulations. Radiation dose was measured for superficial and centrally located radiosensitive organs. The angular range of the OTCM exposure window was determined for different tube rotation times (t) by means of a solid-state detector. Image noise was measured as the standard deviation of the Hounsfield unit value in regions of interest drawn at selected anatomical sites.ResultsATCM+OTCM resulted in a reduction of radiation dose to all radiosensitive organs. In head, eye lens dose was reduced by up to 13% in ATCM+OTCM compared with ATCM. In thorax, the corresponding reduction for breast dose was up to 10%. The angular range of the OTCM exposure window decreased with t. For t = 0.4 s, the angular range was limited to 74° in head and 135° for thorax. Image noise was significantly increased in ATCM+OTCM acquisitions across most examined phantoms (p < 0.05).ConclusionsOTCM reduces radiation dose to exposed radiosensitive organs with the eye lens and breast buds exhibiting the highest dose reduction. The OTCM exposure window is narrowed at short t. An increase in noise is inevitable in images located within the OTCM-activated imaged volume.Key Points• In pediatric CT, organ-based tube current modulation reduces radiation dose to all major primarily exposed radiosensitive organs.• Image noise increases within the organ-based tube current modulation enabled imaged volume.• The angular range of the organ-based tube current modulation low exposure window is reduced with tube rotation time.

Highlights

The lens of the eye and breast are considered among the most radiosensitive tissues of the human body
Measurements of exposure rate on the 16 cm diameter polymethyl methacrylate (PMMA) phantom confirmed that Organ-based tube current modulation (OTCM) reduces exposure by 30% in head and 40% in thorax
The increase in image noise was statistically significant (p < 0.05) in all but neonate phantom. This is the first study aimed to assess the effect of OTCM on radiation dose of radiosensitive organs in children

Summary

Introduction

The lens of the eye and breast are considered among the most radiosensitive tissues of the human body. In one approach, implemented by Siemens Healthcare with X-CARE, mA is reduced when the x-ray tube rotates over the anterior quadrant of the body circumference, while it is increased over the lateral and posterior quadrants to preserve image quality [6,7,8,9]. In a second approach, implemented by GE Medical Systems with ODM, mA is reduced when the x-ray tube rotates over the anterior part of the patient’s body without increase over the remaining lateral and posterior parts. This approach has been documented to deliver images of increased noise [10, 11]. There is scarce published data on the effect of OTCM on radiation dose to superficial radiosensitive organs and image quality in pediatric CT examinations [14, 15]

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