Reducing Dose in CT Imaging: Theory, Practice, and Lessons Learnt from Very Low-Dose CT

Joanne Sil, DCR, Richard S. Lawson, PhD, MInstP, FIPEM, Peter Hogg, Mark Elias, MBBCh, MRCS, FRCR, T P Kane, MB, ChB, FRCR, DMR(D), and Rachel Taylor, MSc

   ^*Lecturer in Radiography, Directorate of Radiography, School of Health Sciences, College of Health and Social Care, University of Salford, Salford, United Kingdom.
   ^†Consultant Medical Physicist, Nuclear Medicine Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester, United Kingdom.
   ^‡Professor, University Lead for Medical Imaging Research, School of Health Sciences, University of Salford, Manchester, United Kingdom.
   ^§Consultant Radiologist, BCUHB (East), Wrexham Maelor Hospital, Wrexham, North Wales, United Kingdom.
   ^llConsultant in Radiology & Nuclear Medicine, Blackpool Teaching Hospitals NHS Foundation Trust, and Alliance Medical Lancashire PETCT Centre, Preston; Honorary Visiting Senior Fellow, Faculty of Health Sciences, University of Salford, United Kingdom.
   ^¶Senior Radiographer, St. Helen's and Knowsley Teaching Hospitals, Whiston Hospital, Prescot, Merseyside, United Kingdom.
   Address correspondence to: Joanne Sil, DCR, Lecturer in Radiography, Directorate of Radiography, Allerton Building, School of Health Sciences, College of Health and Social Care, University of Salford, Frederick Road M6 6PU, United Kingdom. E-mail: j.sil@salford.ac.uk.

Disclosures: The authors report having no financial or advisory relationships with corporate organizations related to this activity.

ABSTRACT

In recent years, the use of radiation in medical imaging has increased considerably with a large proportion of this increase due to the use of CT imaging. Along with an increase in medical radiation exposures comes the fear of increased risk of radiation-induced cancers. Drawing on evidence from literature and a research group that is exploring the value of very low-dose CT in the terms of its ability to detect pathology, this article introduces the reader to the effects of ionizing radiation and the implications of its use in medical imaging. The risks associated with radiation dose and the general principles of radiation protection are discussed, including an overview of the key concepts of CT and the acquisition parameters that can affect patient radiation dose and image quality. Ways in which acquisition parameters can reduce radiation dose to the patient are considered and how certain reconstruction methods can be utilized to support this. As a research group, we anticipate that lessons learnt from low-dose CT research could have value in diagnostic CT imaging which usually has relatively higher dose implications for the patient. It is important to note that this article was written from the perspective of a UK research group and consequently there is reference to ionizing regulations and regulatory bodies that have been adopted in the United Kingdom, namely Ionizing Radiation (Medical Exposure) Regulations 2000 and the International Commission on Radiological Protection. The reader should be aware that the American College of Radiology works closely with the Conference of Radiation Control Program Directors to produce equivalent guidelines.