CT Dose Reduction Applications: Available Tools on the Latest Generation of CT Scanners

doi:10.1016/j.jacr.2012.06.025

Journal of the American College of Radiology

Volume 10, Issue 1, January 2013, Pages 37-41

https://doi.org/10.1016/j.jacr.2012.06.025 Get rights and content

Increasing concerns about radiation dose have led CT manufacturers to further develop radiation dose reduction tools in the latest generation of CT scanners. These tools include automated tube current modulation, automated tube potential selection, and iterative reconstruction. This review details the principles underlying each of these 3 dose reduction utilities and their different permutations on each of the major vendors' equipment. If available on the user's equipment, all 3 of these tools should be used in conjunction to enable maximum radiation dose savings.

Introduction

The growth in the volume of CT studies performed in the United States over much of the past 2 decades has been enormous [1]. This growth in volume, combined with the increasing use of CT in radiation-sensitive populations (ie, children, young adults, and pregnant female patients), has been an impetus for CT manufacturers to develop a number of radiation dose reduction tools. Furthermore, there has been a realization among radiologists that image quality should not be the only parameter considered when imaging a patient and that every study should be performed at the lowest possible radiation dose.

However, although there has been a rapid proliferation of dose reduction tools on all of the most recent CT scanners, these dose reduction applications are still underused, largely because of confusion on the part of users as to the purpose and utilization of each tool. In this review, we detail 3 radiation dose reduction methods, found on the most recent generation of CT scanners, that should be used in every practice: (1) automated tube current modulation, (2) automated tube potential selection, and (3) iterative reconstruction. Clearly, most of these tools are available in a number of different forms on each of the major vendors' newest equipment. However, given our institution's recent experience with the latest Siemens Somatom Flash scanners (Siemens Healthcare, Forchheim, Germany), we use the Siemens software as an example for each of these entities.

Section snippets

Automatic Tube Current Modulation

Automatic tube current modulation (or automatic exposure control [AEC]), referred to by a number of different names on each of the major vendors' equipment (Table 1), is a tool designed to modulate the imparted radiation dose (via changes in tube current-time product [mAs]) on the basis of patient size and attenuation [2, 3]. In other words, the mAs is increased in those parts of the body with the greatest attenuation (such as through the shoulders or hips) and diminished as the soft tissue

Automated Tube Potential Selection

Decreasing tube voltage (kVp) can be an extremely effective means of reducing radiation exposure, as the radiation dose changes with roughly the square of the tube potential [6]. With a constant tube current, decreasing the tube potential from 120 to 100 kVp can result in a dose reduction of roughly 33%, and decreasing the tube potential from 120 to 80 kVp can result in up to a 65% reduction in dose [7, 8]. Moreover, as the kVp is decreased, the attenuation of iodine increases because of the

Iterative Reconstruction

Until recently, CT reconstruction methods were all based on filtered back projection (FBP). Although the technical details of FBP are beyond the scope of this discussion, the algorithms underlying FBP offer only an approximate mathematical relationship between the “projection data” (ie, the x-ray attenuation data measured during CT acquisition) and the data displayed in the final CT image. If the acquired data were perfectly devoid of noise with unlimited resolution, then the displayed image

Conclusions

Although all the major CT manufacturers offer significant tools to reduce radiation dose, many centers do not take advantage of the dose reduction capabilities of their scanners because of a lack of familiarity and understanding as to how these tools work. However, these tools are now built into scanner software with relatively simple, intuitive interfaces, and little or no day-to-day manipulation of the scanner's settings by technologists or radiologists is required. Moreover, each of the

Take-Home Points

•
Automatic tube current modulation is a tool designed to modulate the imparted radiation dose, via changes in mAs, on the basis of the patient's size and attenuation.
•
Automated tube potential selection automatically calculates the optimal tube potential and corresponding tube current for each patient depending on the type of study being performed, the body region being imaged, and the patient's body habitus.
•
Iterative reconstruction algorithms have emerged as an alternative to traditional FBP and

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Original articleCT Dose Reduction Applications: Available Tools on the Latest Generation of CT Scanners

Introduction

Section snippets

Automatic Tube Current Modulation

Automated Tube Potential Selection

Iterative Reconstruction

Conclusions

Take-Home Points

Eur J Radiol

Eur J Radiol

J Am Coll Radiol

National trends in CT use in the emergency department: 1995-2007

Radiology

Radiation dose modulation techniques in the multidetector CT era: from basics to practice

Radiographics

Automatic exposure control in computed tomography—an evaluation of systems from different manufacturers

Acta Radiologica

Automatic exposure control in CT: applications and limitations

J am Coll Radiol

Automated tube potential selection for standard chest and abdominal CT in follow-up patients with testicular cancer: Comparison with fixed tube potential

Eur Radiol

Individually adapted coronary 64-slice CT angiography based on precontrast attenuation values, using different kVp and tube current settings: evaluation of image quality

Int J Cardiovasc Imaging

Diagnostic accuracy of pulmonary CT angiography at low tube voltage: intraindividual comparison of a normal-dose protocol at 120 kVp and a low-dose protocol at 80 kVp using reduced amount of contrast medium in a simulation study

AJR Am J Roentgenol

Image quality and dose performance of 80 kV low dose scan protocol in high-pitch spiral coronary CT angiography: feasibility study

Int J Cardiovasc Imaging

Dual-energy and low-kVp CT in the abdomen

AJR Am J Roentgenol

Coronary CT angiography of patients with a normal body mass index using 80 kVp versus 100 kVp: a prospective, multicenter, multivendor randomized trial

AJR Am J Roentgenol

Automated attenuation-based tube potential selection for thoracoabdominal computed tomography angiography: improved dose effectiveness

Invest Radiol

Original article
CT Dose Reduction Applications: Available Tools on the Latest Generation of CT Scanners