Reducing CT Radiation With Indication-Specific Protocols

The implementation of indication-specific computed tomography (CT) protocols and the adjustment of scan parameters decreased total body radiation exposure while still delivering an acceptable level of diagnostic image quality, according to results from a study published in the Journal of Medical Imaging and Radiation Oncology.¹

Shakkarat Sulagaesuan, MD, of Ramathibodi Hospital, Mahidol University in Bangkok, Thailand, and colleagues retrospectively acquired emergency department (ED) data from an urban academic medical center and analyzed patient demographic data and CT examination data from medical records and the radiology information system. These data were collected before and after the implementation of radiation dose-reduction methods.

Two simple methods for reducing radiation dose were implemented. These included the development of indication-specific scanning protocols and optimization of CT scan parameters, as guided by literature review and consensus agreement among radiologists.

The indication-specific protocols were designed so that examinations could cater to specific patient presentations and for the most likely differential diagnoses. Each indication-specific protocol was then provided guidelines on scanning parameters, including number of scanning acquisitions and scanning technique for any given radiographic examination.

The researchers found that all CT types resulted in a decrease in the total body radiation dose that patients received after the protocol initiation. Average volume CT dose index (CTDVi) decreased after protocol implementation as compared tp before implementation for head (51.5 vs 109 mGy), chest (8.1 vs 30.4 mGy), abdomen (13.1 vs 41.8 mGy), pelvis (11 vs 38 mGy), and abdominopelvic region (11.2 vs 41.8 mGy).

These findings were limited by the fact that 2 separate dose-reduction techniques were implemented concurrently (indication-specific protocols and optimization of CT parameters); thus, the extent to which the individual techniques contributed to the decrease in total body radiation is unknown.

Summary and Clinical Applicability

In this study, a significant radiation dose reduction associated with CT scans performed in the ED was accomplished by implementing the use of indication-specific protocols and CT parameter optimization. The study authors indicate that “simple methods could help significantly reduce CT radiation exposure in ED patients while maintaining an acceptable level of diagnostic image quality.”

Ionizing radiation from medical imaging has risen sharply in the United States.² The cumulative effect of small individual doses in a patient population undergoing frequent and often repeated imaging presents a public health concern. The concept of “effective dose” takes into account the particular tissue or organ that absorbs the radiation.³ Effective dose allows comparison of exposure across different types of imaging.

Estimating the total radiation dose and the potential risks of malignancy associated with a given radiologic examination can be difficult to determine and discuss with patients. The need to obtain informed consent for the radiation risks of imaging studies remains controversial, with some experts stating that a formal risk-benefit discussion regarding a patient’s specific radiation risk is not possible given current uncertainty of malignancy risk associated with specific studies.⁴   However, patients should be aware that the precise risk of malignancy from radiologic procedures cannot be calculated at this point in time. 

Some studies have suggested that a comparison of the estimated effective dose in a radiographic study be compared to that of a single chest radiograph (0.02 mSv) or the total annual radiation dose received from Earth’s natural background radiation (3.0 mSv).⁴

The linear no-threshold (LNT) model is a dose-response model that correlates radiation exposure with the risk of developing cancer; it assumes that any exposure to ionizing radiation can increase future risk of malignancy.⁵   While some researchers have suggested that this threshold is not reached by the most common low-dose radiologic studies, the US National Council on Radiological Protection and Measurements and the US National Academy of Sciences Biological Effects of Ionizing Radiation committees both suggest that the LNT model can be used to estimate the risks of ionizing radiation.⁶

The American College of Radiology has since developed appropriateness criteria for several radiologic examinations, aiming to decrease the rate at which inappropriate radiographic studies are performed. ⁶

References

1.       Sulagaesuan C, Saksobhavivat N, Asavaphatiboon S, Kaewlai R. Reducing emergency CT radiation doses with simple techniques: A quality initiative project. J Med Imaging Radiat Oncol. 2016;60(1):23-34.

2.       Smith-Bindman R, Miglioretti DL, Johnson E, et al. Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996-2010.JAMA. 2012;307:2400-2409.

3.       Bolus NE. Basic review of radiation biology and terminology. J Nucl Med Technol. 2001;29:67-73.

4.       Brink JA, Goske MJ, Patti JA. Informed decision making trumps informed consent for medical imaging with ionizing radiation. Radiology. 2012;262:11-14.

5.       Evaluation of the linear nonthreshold dose-response model for ionizing radiation. Report No 136. National Council on Radiation Protection and Measurements, Bethesda, MD. Source Code.

6.       The 2007 Recommendations of the International Commission on Radiological Protection. ICRP publication 103. Ann ICRP 2007; 37:1. Source Code.