The use of cardiac computed tomography (CT) in patients with congenital heart disease (CHD) has been limited by concerns about high radiation exposure. Recent-generation CT scanner technology significantly reduces radiation exposure compared with older technology (1). We created a multi-institutional, prospective, observational registry to determine radiation dose estimates for the use of cardiac CT imaging in patients with CHD of all ages across 4 institutions in the current era (June 1, 2017, to January 30, 2020) (2). The study was institutional review board approved. Anonymized patient and CT scan data were entered into a REDCap (Research Electronic Data Capture) database by each institution. Radiation dose was recorded as dose length product (DLP) in milligray multiplied by the scan length in centimeters from the scanner platform for each scan and also for total procedural dose, including topograms, monitoring sequences, and diagnostic scan acquisition. Radiation dose estimates were compared according to age and between institutions and are described as median and interquartile range. Estimated effective dose in millisieverts was calculated by multiplying DLP by age-adjusted tissue weighting factors (k) from the International Commission on Radiological Protection (ICRP) publication 103 (k = 0.026 to 0.085) and from ICRP publication 60 (k = 0.014 to 0.079) for historic comparison (3,4). A total of 1,742 electrocardiogram (ECG) gated cardiac CT scans were performed in 1,337 patients with CHD aged 1 day to 80 years. The scans included 1,516 anatomic scans and 226 functional scans. A majority of patients (70%) had a single diagnostic scan acquisition. Of the patients who had >1 diagnostic scan performed during the procedure, 29% had 2 scans in the same procedure (231 had 2 anatomic scans, 148 had one functional and one anatomic scan, and 3 had 2 functional scans). Twelve patients (0.9%) had 3 scans (9 had 3 anatomic, 2 had 2 anatomic and 1 functional, and 1 patient had one anatomic and 2 functional scans).
Anatomic scans were performed by using prospective ECG triggered high-pitch spiral scan mode (76%) or prospective ECG triggered axial scan mode (24%). All functional scans were performed by using retrospective ECG gated spiral scan mode employing pulse modulation. Tube voltage was 70 kVp in a majority of scans (58%) followed by 80 kvp (21%), 90 kvp (3%), 100 kvp (12%), 110 kvp (1%), 120 kvp, and 130 kvp (0.5%). CT scanner platforms included Siemens (Forchheim, Germany) dual-source Flash (58%), dual-source Force (41%), and dual-source Drive (1%).
The median (interquartile range) DLP for an anatomic scan was 17 (7 to 55) mGy•cm, and for a functional scan it was 135 (58 to 275) mGy•cm. Total procedural DLP for the entire cohort was 32 (12 to 98) mGy•cm, ranging from 10 (7 to 12) mGy•cm for patients <6 months of age to 206 (121 to 349) mGy•cm for adult patients >18 years of age. The median procedural age-adjusted effective radiation dose for the entire cohort was estimated to be 1 mSv (ICRP 60) or 1.56 mSv (ICRP 103). There was significant variability of radiation dose estimates according to age groups as well as according to age groups between institutions (p < 0.001) (Table 1).
TABLE 1.
Radiation Dose Estimates for Cardiac CT Imaging in CHD According to Age and Institution
| Entire Group | ≤6 Months | >6 Months to 2.5 Years | >2.5 to 7.5 Years | >7.5 to 12.5 Years | >12.5 to <18 Years | ≥18 Years | |
|---|---|---|---|---|---|---|---|
| Radiation dose estimate by age | |||||||
| Procedural | 1,337 | 392 | 163 | 151 | 130 | 213 | 288 |
| DLP, mGy•cm | 32 (12-98) | 10 (7-12) | 16 (12-24) | 27 (19-42) | 45 (33-75) | 84 (57-126) | 206 (121-349) |
| Age-adjusted dose, mSv, ICRP 60* | 1.01 (0.70-1.85) | 0.78 (0.55-0.94) | 0.83 (0.62-1.25) | 0.97 (0.68-1.51) | 1.17 (0.86-1.95) | 1.18 (0.80-1.76) | 2.88 (1.69-4.89) |
| Age-adjusted dose, mSv, ICRP 103† | 1.56 (0.94-3.15) | 0.85 (0.60-1.02) | 1.26 (0.95-1.90) | 1.76 (1.24-2.73) | 1.67 (1.22-2.78) | 2.18 (1.48-3.26) | 5.36 (3.15-9.07) |
| Anatomic scan | 1,516 | 509 | 196 | 170 | 137 | 219 | 285 |
| DLP, mGy•cm | 17 (7-55) | 5 (4-8) | 11 (8-16) | 19 (15-29) | 35 (20-53) | 61 (40, 94) | 93 (58-145) |
| Functional scan | 226 | 23 | 14 | 17 | 15 | 33 | 124 |
| DLP, mGy•cm | 135 (58-275) | 13 (10-22) | 22 (17-35) | 57 (41-65) | 72 (54-107) | 106 (74-151) | 248 (152-370) |
| Procedural radiation dose estimate by institution and age | |||||||
| Institution A | 344 | 105 | 49 | 42 | 43 | 81 | 24 |
| DLP, mGy•cm | 36 (13-77) | 11 (10-13) | 23 (15-28) | 36 (31-44) | 62 (41-86) | 89 (64-138) | 101 (73-138) |
| Institution B | 501 | 125 | 46 | 54 | 45 | 77 | 154 |
| DLP, mGy•cm | 46 (15-148) | 10 (8-13) | 21 (14-27) | 33 (19-63) | 50 (33-77) | 84 (44-126) | 232 (138-368) |
| Institution C | 392 | 146 | 57 | 47 | 37 | 51 | 54 |
| DLP, mGy•cm | 16 (8-51) | 7 (5-9) | 12 (10-14) | 18 (16-20) | 36 (24-45) | 71 (48-99) | 241 (123-389) |
| Institution D | 100 | 16 | 11 | 8 | 5 | 4 | 56 |
| DLP, mGy•cm | 103 (22-192) | 10 (8-12) | 20 (16-22) | 31 (23-40) | 40 (37-41) | 79 (54-101) | 160 (118-287) |
Historical estimates of radiation dose for ECG gated cardiac CT scans in pediatric CHD patients are as high as 18 mSv (1), and noncardiac pediatric chest CT radiation dose estimates range from 0.03 to 69.2 mSv per scan (5). Our data, albeit limited to dual-source CT scanners, show that cardiac CT has a uniformly low effective radiation dose in the current era in a real-world and multi-institutional cohort of patients with CHD of all ages when scanned in centers with imaging physicians experienced in CHD, access to recentgeneration CT technology, and dose optimization tailored to clinical indication. The variability of dose estimates between institutions indicates there is room for further dose optimization within participating institutions. These data show that cardiac CT imaging should not be restricted in patients with CHD due to radiation dose concerns when advanced imaging is needed for clinical practice. These findings may not be applicable to centers without equivalent capabilities.
ACKNOWLEDGMENTS
The authors thank Katelyn Storey and Miranda Kunz for their support of registry development and data collection, and Christian Schmidt, MS, and Larissa Stanberry, PhD, for their statistical guidance.
This study has been supported by unrestricted research grants from Siemens Healthineers and the Jon DeHaan Foundation. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the AuthorCenter.
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