Prospective Multicenter Registry On RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy IN Daily Practice in 2017 (PROTECTION-VI)

The "Prospective Multicenter Registry On RadiaTion Dose Estimates Of Cardiac CT AngIOgraphy IN Daily Practice in 2017" (PROTECTION-VI) study is a prospective registry and investigator-initiated initiative without third-party funding, which will collect and analyze the radiation dose exposure of Cardiac Computed Tomography Angiographic (CCTA) studies in current daily practice worldwide. Particularly, the study will assess the use of strategies for dose reduction during CCTA.

A decade ago, the multicentre observational PROTECTION-I study has revealed that the dose-length-product of CCTA ranges between 568 - 1259 mGy x cm with a median of 885 mGy x cm. This corresponds to an estimated effective dose of approximately 12 mSv. Since then a variety of techniques have been developed and enhanced in order to reduce radiation exposure during CCTA. Recent studies demonstrated feasibility of dramatically reduced effective radiation doses during CCTA (0,1 - 0,3 mSv). This has been executed in small cohorts of patients at scientific expert centers. However, it remains unclear, if such low-level radiation dose exposure may be achieved in clinical routine and if diagnostic image quality is maintained. In order to analyze the magnitude of radiation dose exposure of CCTA in today's clinical practice and the current use of dose-saving techniques, we designed the PROTECTION-VI study. Eventually, this study may contribute to further improving radiation dose exposure for patients undergoing CCTA.

Study Overview

• Status: Completed
• Conditions: Coronary Artery Disease; Cardiac Disease; Malignancy, Second

Detailed Description

Cardiac CT angiography (CCTA) has emerged to a powerful and commonly used diagnostic tool for the evaluation of coronary artery disease. Advantages of CCTA are its non-invasive approach, widespread availability and high negative predictive value to rule out coronary artery disease. However, radiation exposure during CCTA needs to be considered, due to the potential risk of malignancy induction.

A decade ago, the multicentre observational PROTECTION I study has revealed that the dose-length-product of CCTA ranges between 568-1259 mGy x cm with a median of 885 mGy x cm. This corresponds to an estimated effective dose of approximately 12 mSv. Furthermore, PROTECTION I demonstrated an up to 7-fold variation of radiation dose between different study sites implicating the large potential for dose reduction. Finally, significant differences have been detected in the radiation exposures between CT systems from different vendors and application of dose-saving algorithms, implying that approaches for dose reduction with respect to hardware and software have also been of relevance in 2007.

Since then a variety of techniques have been developed and enhanced in order to reduce radiation exposure during CCTA. Earlier, ECG-controlled tube current modulation has been accepted to reduce radiation dose and was therefore used in ECG-gated retrospective cardiac spiral scanning.

Another dose-saving technique is the reduction of tube potential from conventionally 120 kVp to 100 kVp in non-obese patients. In the PROTECTION II trial we demonstrated that diagnostic image quality is being maintained with a reduction of tube potential to 100 kVp while radiation exposure was significantly reduced by 31%.

Development of prospective ECG-gated axial (sequential) scanning allowed further dose reduction, due to administration of radiation only at the end of diastole. In the PROTECTION III trial we could demonstrate that diagnostic image quality is being maintained with prospective ECG-gated axial scanning in patients with stable and low heart rates while radiation exposure was reduced by 69% when compared to conventional spiral scanning with retrospective ECG gating. Using prospectively ECG-triggered high-pitch spiral CCTA with image acquisition during only one cardiac cycle, additional dosage may be saved when used in selected patients with low and stable heart rates. However, a scan strategy with an attempt of high-pitch scanning first is vulnerable to motion artefacts and bears the risk of repeated scanning.

In the PROTECTION IV trial we compared a scan strategy of high-pitch helical scanning first with a conventional scan first strategy. We could demonstrate maintenance of image quality using the strategy of high-pitch helical scanning first, while radiation exposure was reduced by 57 %, when compared to the conventional scan first strategy.

The introduction of iterative image reconstruction technique with advanced raw data processing let to improvement of image quality compared to traditional filtered back projection. This allowed additional dose saving during image acquisition. In the PROTECTION V trial we demonstrated the feasibility of combining iterative image reconstruction techniques with a reduction of tube currents by 30% leading to maintenance of diagnostic image quality while saving radiation dose linearly to tube current.

In summary, the four randomized clinical trials PROTECTION II-V demonstrated that different techniques for reducing radiation exposure during CCTA can be applied in clinical practice without compromising diagnostic image quality. The studies show that the different approaches can also be applied in combination and that these approaches can be used with different CT platforms from different CT vendors.

Recent studies demonstrated that the effective radiation dose for one CCTA scan may be reduced to 0,3 mSv15 or even below 0,1 mSv in a small amount of carefully selected patients. However, it remains unclear if such dramatically low dosages are being achieved and if diagnostic image quality is being maintained in clinical routine. In order to analyze the magnitude of radiation dose exposure during CCTA in today's clinical practice, we designed the international and multicentric PROTECTION VI study. We will assess the variation of radiation dose with respect to vendors, CT systems and study sites. Furthermore, we will evaluate the usage of dose saving strategies including the above-mentioned in daily practice and analyze their effect on diagnostic image quality. On the basis of the collected data, we will evaluate the potential use of additional dose savings for each site individually.

• Study Type: Observational
• Enrollment (Actual): 4502

Contacts and Locations

Study Locations

• Canada
  • British Columbia
    • Vancouver, British Columbia, Canada
      • University of British Columbia, Department of Medical Imaging
• Germany
  • Bavaria
    • Munich, Bavaria, Germany, 808303
      • Ludwig-Maximilians-Universitaet Muenchen, Medizinische Klinik I
• Israel
  • Haifa, Israel
    • Technion Israel Institute of Technology, The Ruth and Bruce Rappaport Faculty of Medicine
• United States
  • Maryland
    • Bethesda, Maryland, United States, 20892-1061
      • National Heart, Lung, and Blood Institute

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Probability Sample

Study Population

Patients undergoing Cardiac Computed Tomography Angiography (CCTA) in clinical routine.

Description

Inclusion Criteria:

• Patients with a clinical indication for CCTA in order to evaluate the coronary arteries or other cardiac structures
• Patients age > 18 years
• Signed informed consent (if required by local IRB)

Exclusion Criteria:

• Known allergy to contrast agent

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Radiation dose estimates of cardiac CT angiographies in daily practice	Assessment after CT scan by radiologist or technical assistant, documented on questionnaire.	Baseline

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Use of dose-saving strategies	Use of Low tube potential imaging, Low tube current imaging, Automated Exposure Control, ECG-controlled tube current modulation (dose pulsing), Iterative image reconstruction techniques and Scan protocols (Prospective ECG-triggered axial scanning technique, Prospective ECG-triggered high-pitch spiral acquisition) will be assessed in the Core Lab according to information given by the CT-examiner on a questionnaire.	Baseline
Assessment of CCTA image quality in relation to radiation dose	Assessment after CT scan by CT-examiner on questionnaire (qualitative) or in the Core Lab (quantitative). Quantitative Assessment includes Signal intensity, Image noise, Contrast-to-noise ratio, Signal-to-noise ratio. Qualitative assessment of each coronary artery is performed using a 3-point grading scale including excellent, intermediate or non-diagnostic as documented on a provided questionnaire.	Baseline
Sufficient result of the first CCTA scan or need for repeated scans	According to information given by the CT-examiner on a questionnaire.	Baseline
Cardiac CT scan length and relationship between scan and heart length	Assessment in Core Lab after analysis of CT scans.	Baseline
Comparison of dose estimates between different continents, CT vendors and CT systems	Analysis done in the Core Lab according to information given by the CT-examiner on a questionnaire.	Baseline

Collaborators and Investigators

• Sponsor: LMU Klinikum

Publications and helpful links

General Publications

• Stocker TJ, Leipsic J, Hadamitzky M, Chen MY, Rubinshtein R, Deseive S, Heckner M, Bax JJ, Kitagawa K, Marques H, Schmermund A, Silva C, Mahmarian J, Kang JW, Grove EL, Lesser J, Massberg S, Hausleiter J. Application of Low Tube Potentials in CCTA: Results From the PROTECTION VI Study. JACC Cardiovasc Imaging. 2020 Feb;13(2 Pt 1):425-434. doi: 10.1016/j.jcmg.2019.03.030. Epub 2019 Jun 12.

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2017
• Primary Completion (Actual): October 31, 2017
• Study Completion (Actual): December 31, 2017

Study Registration Dates

• First Submitted: December 13, 2016
• First Submitted That Met QC Criteria: December 14, 2016
• First Posted (Estimate): December 19, 2016

Study Record Updates

• Last Update Posted (Actual): May 15, 2018
• Last Update Submitted That Met QC Criteria: May 12, 2018
• Last Verified: May 1, 2018

More Information

Terms related to this study

• Keywords: coronary artery disease; radiation dose; effective dose; Cardiac Computed Tomography (CT) Angiography (CCTA); malignancy induction; dose saving techniques
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Vascular Diseases; Arteriosclerosis; Arterial Occlusive Diseases; Heart Diseases; Neoplasms; Coronary Artery Disease; Myocardial Ischemia; Coronary Disease; Neoplasms, Second Primary
• Other Study ID Numbers: MUC I002-16

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO