Standardization and Optimization of CT Protocols to Achieve Low Dose

doi:10.1016/j.jacr.2013.10.016

Journal of the American College of Radiology

Volume 11, Issue 3, March 2014, Pages 271-278

https://doi.org/10.1016/j.jacr.2013.10.016 Get rights and content

The increase in radiation exposure due to CT scans has been of growing concern in recent years. CT scanners differ in their capabilities, and various indications require unique protocols, but there remains room for standardization and optimization. In this paper, the authors summarize approaches to reduce dose, as discussed in lectures constituting the first session of the 2013 UCSF Virtual Symposium on Radiation Safety and Computed Tomography. The experience of scanning at low dose in different body regions, for both diagnostic and interventional CT procedures, is addressed. An essential primary step is justifying the medical need for each scan. General guiding principles for reducing dose include tailoring a scan to a patient, minimizing scan length, use of tube current modulation and minimizing tube current, minimizing tube potential, iterative reconstruction, and periodic review of CT studies. Organized efforts for standardization have been spearheaded by professional societies such as the American Association of Physicists in Medicine. Finally, all team members should demonstrate an awareness of the importance of minimizing dose.

Introduction

The first of 12 sessions held as part of the 2013 UCSF Virtual Symposium on Radiation Safety in Computed Tomography (CT) focused on the standardization and optimization of protocols to achieve low dose. Talks in this session addressed a wide range of applications of CT, including diagnostic and interventional procedures, special populations such as pregnant patients, and the role of team members such as technologists and physicists. This paper serves as a summary of the session.

Section snippets

Radiation Exposure From Medical Imaging: Evidence for Harmful Effects

The opening plenary session, by Andrew Einstein of Columbia University, focused on basic concepts of radiation and the evidence relating radiation exposure to cancer risk. Tissue reactions (formerly referred to as deterministic effects) such as skin erythema and hair loss, which are due to radiation-induced cell death or damage, stand in contrast to stochastic effects such as cancer, which are due to mutations. The concepts of risk and dose were contrasted: the former is a probability of a

The Physician

Physicians influence patient radiation dose through monitoring protocols and targeting body part–specific and disease-specific protocols that can minimize dose. The goal in selecting protocols is not necessarily to create the highest technical quality image but to generate a diagnostic image using the lowest dose possible. Strategies to reduce medical radiation exposure have in large part revolved around two aims: first, to achieve higher awareness regarding the significance of medical

Head CT

In head CT, it is essential that proper attention be paid to the mechanics of scanning. For example, proper gantry angulation can reduce eye lens dose by as much as 87%. Proper patient centering leads to optimal automatic exposure control and image quality [10], with off-center positioning increasing radiation dose and image noise. Each scout scan should be tailored to the clinical question and should be acquired at a very low dose (eg, 80 kVp and 20–40 mAs are sufficient). Good scanning

Pregnancy and Diagnostic CT

CT scanning in pregnant women should be avoided if possible. Radiologists must take into account the benefits of CT versus potential harmful effects to pregnant patients and fetuses. Maternal health has a profound effect on fetal health, and therefore, CT personnel and referring physicians must balance the potential effects of CT on the fetus versus the requirement for diagnostic information in the mother.

Effects of ionizing radiation on the fetus include both stochastic effects and tissue

Spine

Common procedures to relieve spinal pain include epidural, facet joint, nerve root, and medial branch blocks. CT guidance ensures accuracy and may improve precision for diagnostic and therapeutic spine injections and may be essential for some procedures, such as biopsies. Without affecting outcomes, 3 simple steps can result in significant reductions in radiation to patients undergoing CT-guided spine-related pain interventions: reducing tube current, using axial acquisitions for short scan

Organized Efforts in Protocol Standardization

An American Association of Physicists in Medicine working group has identified goals for reducing CT dose: protocol parameters, dose checking, and nomenclature standardization. A working group on the standardization of CT nomenclature and protocols was formed in 2010 with two distinct goals: (1) develop consensus protocols for frequently performed CT examinations, summarizing the basic requirements of the examinations and giving several model-specific examples of scan and reconstruction

Conclusions

Achieving a low-dose scan is a team effort requiring tailoring of the scan to the patient and medical question, continuous quality improvement to implement emerging strategies for dose optimization, and awareness of the scanning team of the risk and hence the need for keeping the dose as low as possible. Attaining this goal in practice requires a considerable knowledge base, encompassing radiation physics, biology, and epidemiology, and spanning different clinical applications, team members,

Take-Home Points

•
Optimizing radiation dose from CT is a team effort, with responsibility for patient care shared among the referring health care provider, imaging physician, technologist, and physicist.
•
Patient-centered imaging, which tailors the study to the patient and clinical question, is essential for dose optimization.
•
Many best practices are shared among CT applications, including careful selection of tube current and potential, minimizing the range scanned, use of iterative reconstruction, and period

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: Drs Trattner and Pearson contributed equally as first authors to this paper.

: Dr Einstein was supported by grant R01 109711 from the National Heart, Lung, and Blood Institute (Bethesda, Maryland) and by a Victoria and Esther Aboodi Assistant Professorship, a Herbert Irving Assistant Professorship, and the Louis V. Gerstner Jr Scholars Program.

: Dr Trattner has received support for other research from Philips Healthcare (Best, The Netherlands). Dr Cody has received an in-kind research grant from GE Healthcare. Dr Hess has received support for other research from GE Healthcare (Little Chalfont, United Kingdom). Dr Einstein has served as a consultant for the International Atomic Energy Agency (Vienna, Austria) and the Radiation Effects Research Foundation (Hiroshima, Japan) and has received support for other research from GE Healthcare, Philips Healthcare, and Spectrum Dynamics (Caesarea, Israel).

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Special issue: Radiation dose optimizationDose optimizationStandardization and Optimization of CT Protocols to Achieve Low Dose

Introduction

Section snippets

Radiation Exposure From Medical Imaging: Evidence for Harmful Effects

The Physician

Head CT

Pregnancy and Diagnostic CT

Spine

Organized Efforts in Protocol Standardization

Conclusions

Take-Home Points

Effective doses in radiology and diagnostic nuclear medicine: a catalog

Radiology

Radiation dose associated with common computed tomography examinations and the associated lifetime attributable risk of cancer

Arch Intern Med

Exposure to low-dose ionizing radiation from medical imaging procedures

N Engl J Med

Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems 1996-2010

JAMA

Recurrent CT, cumulative radiation exposure, and associated radiation-induced cancer risks from CT of adults

Radiology

Effects of radiation exposure from cardiac imaging: how good are the data?

J Am Coll Cardiol

Cancer risk in 680,000 people exposed to computed tomography scans in childhood or adolescence: data linkage study of 11 million Australians

BMJ

Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study

Lancet

Radiation dose vs. image quality for low-dose CT protocols of the head for maxillofacial surgery and oral implant planning

Radiat Prot Dosim

Comparison of effective doses for low-dose MDCT and radiographic examination of sinuses in children

Am J Roentgenol

Comparison of image quality between conventional and low-dose nonenhanced head CT

Am J Neuroradiol

Radiation dose reduction strategy for CT protocols: successful implementation in neuroradiology section

Radiology

Balancing radiation dose and image quality: clinical applications of neck volume CT

Am J Neuroradiol

Estimated radiation dose associated with cardiac CT angiography

JAMA

Special issue: Radiation dose optimization
Dose optimization
Standardization and Optimization of CT Protocols to Achieve Low Dose