Radiation Dose-Reduction Strategies for Neuroradiology CT Protocols

Abstract

SUMMARY:Within the past 2 decades, the number of CT examinations performed has increased almost 10-fold. This is in large part due to advances in multidetector-row CT technology, which now allows faster image acquisition and improved isotropic imaging. The increased use, along with multidetector technique, has led to a significantly increased radiation dose to the patient from CT studies. This places increased responsibility on the radiologist to ensure that CT examinations are indicated and that the "as low as reasonably achievable" concept is adhered to. Neuroradiologists are familiar with factors that affect patient dose such as pitch, milliamperes, kilovolt peak (kVp), collimation, but with increasing attention being given to dose reduction, they are looking for additional ways to further reduce the radiation associated with their CT protocols. In response to increasing concern, CT manufacturers have developed dose-reduction tools, such as dose modulation, in which the tube current is adjusted along with the CT acquisition, according to patient's attenuation. This review will describe the available techniques for reducing dose associated with neuroradiologic CT imaging protocols.T he increase in the number of CT studies in the United States and Europe 1,2 that followed the introduction of multidetector-row technology has led to a significant increase in the radiation dose related to CT scanning.3-6 CT scanning comprises approximately 15% of radiologic examinations but represents the largest single source of medical radiation exposure, accounting for up to 70% of the radiation dose to patients. 7 Patients are becoming more aware of the radiation dose related to CT scanning due to increasing coverage in the lay press. 8 The radiation risk to children is of particular concern; the estimated lifetime cancer risk for a 1-year-old child from the radiation exposure of a head CT is 0.07%. 9The potential health risks associated with radiation have placed increasing pressure on the radiology community to ensure that CT imaging protocols are optimized for diagnostic image quality at the lowest radiation dose possible ("as low as reasonably achievable"). Because the latest generation of CT scanners automatically records the CT dose for each study and archives this as part of the patient's permanent medical record, exaggerated delays in implementing dose-reduction strategies may also have medical-legal implications. The purpose of this review is to discuss available methods to achieve dose reduction for neuroradiology CT protocols while preserving the diagnostic quality of imaging studies. CT-Associated Radiation-Dose MeasurementIn 2001, in response to the growing concern over CT-associated radiation dose, the US Food and Drug Administration published guidelines to address this issue, especially in pediatric patients and in the small-adult population. These guidelines give recommendations on how to optimize CT protocols and encourage the elimination of inappropriate referrals for CT as well as the reduction of the numbe...

An education and training programme for radiological institutes: impact on the reduction of the CT radiation dose

“…for CT of the thorax or abdomen [37,43] • Review the clinical justification for the CT examination and reconsider using imaging techniques that are free of ionising radiation (e.g. MRI, ultrasound) [29] • Limit the imaging range to the area of interest, for follow-up studies in particular [44] • Prevent the extend beyond the anatomic limits (e.g., thorax, abdomen) which does not add clinically important information [7] • Position the arms above the shoulders during chest CT [45] • Position the patient precisely in the gantry [12,46,47] brain, chest and pulmonary arteries (Table 4).…”

The Use of Adaptive Statistical Iterative Reconstruction in Pediatric Head CT: A Feasibility Study

“…Multiple different strategies have been adopted in the past in an attempt to lower the cumulative head CT radiation dose, [25][26][27][28] including decreasing the milliamperes, shielding (ie, thyroid shields, bismuth eye shields), automatic tube-current modulation, angling the gantry to exclude the orbits, and so forth. Dosereduction techniques that involve reducing the milliamperes, however, are limited by the resulting increased image noise and decreased CNR when using FBP as the reconstruction algorithm.…”

Sixty-Four-Section Multidetector CT Angiography of Carotid Arteries: A Systematic Analysis of Image Quality and Artifacts

“…[18][19][20][21] Finally, we also attempted to minimize the radiation dose to the patient by performing x-y-z-axis dose modulation on 64-section CT, in which the tube current applied within each CT section varies depending on the patient's attenuation and girth at each level, while still preserving image quality. 22,23 With dose modulation, the radiation dose to the patient from 64-section CTA is comparable with the dose from unmodulated 16-section CTA. 23 This is important given the concern for increased radiation from obtaining a higher number of very thin sections on 64-section CT scanners as compared with earlier generation scanners.…”