August 10, 2011
RE: Draft Report for Consultation; ICRP ref 4818-2733-7736, May 20, 2011
The Society of Cardiovascular Computed Tomography (SCCT) appreciates the opportunity to comment on the draft report of the International Commission on Radiological Protection (ICRP) entitled: Patient and Staff Radiological Protection in Cardiology. SCCT, with nearly 4000 members, is the professional society representing physicians, scientists and technologists advocating for research, education and clinical excellence in the use of cardiovascular computed tomography.
SCCT thanks the ICRP for its important contributions in protecting the public health from unnecessary radiation exposure. SCCT understands that all health professionals have a responsibility to address fundamental radiation exposure and protection issues, and we invite the ICRP to view our recently released SCCT guidelines on radiation dose and dose-optimization strategies in cardiovascular CT --http://www.scct.org/documents/guidelines_radiation.pdf. This guideline document reviews available data and provides recommendations regarding interpretation of radiation dose indices and predictors of risk, appropriate use of scanner acquisition modes and settings, development of algorithms for dose optimization, and establishment of procedures for dose monitoring.
In addition, we respectfully request that the ICRP review the Standardized medical terminology for cardiac computed tomography: A report of the Society of Cardiovascular Computed Tomography --
http://www.scct.org/documents/JCCT427.pdf. This document creates and defines a standardized nomenclature for cardiac computed tomography and associated medical terminology.
SCCT reviewers have identified several issues of concern regarding the text of the ICRP draft report on Patient and Staff Radiological Protection in Cardiology. Some of these issues are designated under “General Comments.” Specific comments also are included below, designated by paragraph, page and/or line numbers, most with reference citations to support suggested revisions. Certain suggested text changes are highlighted in yellow.
General Comments:
We respectfully request that certain terminology in the report be modified to reflect updates to standardized nomenclature for the field of cardiac computed tomography. See reference above: Standardized medical terminology for cardiac computed tomography: A report of the Society of Cardiovascular Computed Tomography -- http://www.scct.org/documents/JCCT427.pdf.
For example:
CCTA -> coronary CT angiography
Coronary artery calcium (CAC) -> coronary calcium scanning
Step-and-shoot -> prospectively ECG-triggered axial
Volume imaging -> prospectively ECG-triggered axial
EGTCM -> ECG-based tube current modulation
mA is not an abbreviation for tube current
kV is not an abbreviation for tube potential
Tube “voltage” should be referred to as tube “potential”
Specific Comments:
Line 291 page 8: "and practitioners" should be deleted; this is not applicable to CT
-- Section 1.2 (page 23): SCCT recommends that a sentence be added to reflect that since 2006, the number of cardiac CT procedures have increased significantly, and there has been significant improvement in both cardiac CT hardware and software, enacting up to an 80% decrease in doses administered for cardiac CT angiography (the 80% value is derived from individual studies based on prospective ECG-triggered axial imaging).
References
E. P. Efstathopoulos, I. Pantos, S. Thalassinou, S. Argentos, N. L. Kelekis, T. Zografos, G. Panayiotakis and D. G. Katritsis. PATIENT RADIATION DOSES IN CARDIAC COMPUTED TOMOGRAPHY: COMPARISON OF PUBLISHED RESULTS WITH PROSPECTIVE AND RETROSPECTIVE ACQUISITION. Radiation Protection Dosimetry (2011), pp. 1–9
Earls, J.P., Schrack, E.C., 2008. Prospectively gated low-dose CCTA: 24 months experience in more than 2,000 clinical cases. Int J Cardiovasc Imaging.
Note that some of SCCT’s expert reviewers believe it is more accurate to state that dose has decreased about 50% every two years since 2005 based on published research reports and multi-center practice surveys. In any case, it should be noted in the text that there has been a substantial decrease in radiation dose from cardiac CT.
References
Raff GL. Radiation dose from coronary CT angiography: five years of progress. JCCT. 2010; 4:365-74).
-- Section 8.2 page 94: Dual source technology should be included
-- Line 3545 page 94: "and practitioners" should be deleted; this is not applicable to CT
-- Section 8.3 Number 160 page 95 – starting on line 3594 - 3596: We believe the sentence is incorrect and outdated, and should read:
For cardiac studies, the most commonly used conversion factor is of 0.014 mSv·mGy-1·cm-1, the European Guidelines on Quality Criteria for Computed Tomography chest factor (i.e., effective dose is estimated as 0.014·DLP) (Bongartz et al., 2004).
New reference
G. Bongartz SJG, A.G. Jurik, M. Leonardi, E. van Persijn van Meerten, R. Rodríguez, K. Schneider, A. Calzado, J. Geleijns, K.A. Jessen, W. Panzer, P. C. Shrimpton, G. Tosi. 2004 CT Quality Criteria. European Guidelines for Multislice Computed Tomography. Luxembourg: European Commission, 2004.
-- Line 3616 page 96: The updated dose measure is tube voltage (kV), not kVp and should be changed throughout the manuscript related to CT. Peak voltage is no longer an accepted terminology in Cardiac CT.
-- Line 3617/18 page 96: Delete "and in some cases the number of x-ray tubes
employed.” This is not an operator selectable parameter.
-- Line 3628 page 96: "different scanner AND SCAN MODES will produce
images..."
-- Line 3629 page 96: "be tailored to each scanner AND SCAN MODE..."
-- Line 3658 page 97: For pulmonary vein CT angiography, the scan length can be reduced. ...structures can be visualized without scanning caudally to the cardiac apex.” SCCT questions if this is well-supported in the literature. It may indeed be appropriate to shorten the scan length caudally compared to coronary imaging but typically the scan is started more cranially. We question if the result would be a net decrease in scan length. Also, structures of interest also include the atrial appendage.
-- Line 3684 page 98: More recently, axial CTCA protocols have been incorporated into most MDCT scanners
-- Line 3697 page 98: "Disadvantages include the inability to ...perform image reconstruction at additional phases THROUGHOUT the ENTIRE cardiac cycle." You can reconstruct more than one phase from prospectively ECG-triggered axial data on some systems (as is stated in the next paragraph), just can't reconstruct at any point during the cardiac cycle.
-- Line 3704 page 98: "The optimal strategy for implementation of axial imaging has not yet been determined" could be omitted.
-- Starting on Line 3715 page 99: There are numerous studies validating the diagnostic accuracy of prospective (axial or step-and-shoot imaging) and the diagnostic accuracy is similar to retrospective studies (references below). Thus, most centers have adapted high utilization of prospective triggering to keep doses reduced by up to 80% during cardiac CT imaging.
References validating prospective imaging accuracy:
Zhonghua Sun, Kwan-Hoong N. Prospective versus retrospective ECG gated multi-slice CT coronary angiography: A systematic review of radiation dose and diagnostic accuracy Eur J Radiology 2011
Kitagawa K, Lardo AC, Lima JAC, George RT. Prospective ECG-gated 320 row detector computed tomography: implications for CT angiography and perfusion imaging.IntJCardiovascImaging2009; 25:201–8.
Dewey ME, Deissenrieder ZF, Laule M, Dubel HP, Schlattmann P, Knebel F, et al. Noninvasive coronary angiography by 320-row computed tomography with lower radiation exposure and maintained diagnostic accuracy: comparison of results with cardiac catheterization in a head-to-head pilot investigation. Circulation 2009; 120:867–75.
Sun Z, Lin CH, Davidson R, Dong C, Liao Y. Diagnostic value of 64-slice CT angiography in coronary artery disease: a systematic review. EurJRadiol 2008; 67:78–84.
Leber AW, Johnson T, Becker A, vonZiegler F, Tittus J, Nikolaou K, et al. Diagnostic accuracy of dual-source multi-slice CT coronary angiography in patients with an intermediate pretest likelihood for coronary artery disease. Eur Heart J 2007; 28:2354–60.
Sun Z, Multi-slice CT Angiography in cardiac imaging: prospective ECG-gating or retrospective ECG-gating? BiomedImagingIntervJ2010;6(1):e4.
Husmann L, Valenta I, Gaemperli O, Adda O, Treyer V, Wyss CA, et al. Feasibility of low-dose coronary CT angiography: first experience with prospective ECG- gating. EurHeartJ2008;29(2):191–7.
Herzog BA, Wyss CA, Husmann L, Gaemperli O, Valenta I, Treyer V, et al. First head-to-head comparison of effective radiation dose from low-dose 64-slice CT with prospective ECG-triggering versus invasive coronary angiography. Heart 2009;95:1656–61.
Hirai N, Horiguchi J, Fujioka C, Kiguchi M, Yamamoto H, Matsuura N, et al. Prospective versus retrospective ECG-gated 64-detector coronary CT angiography: assessment of image quality, stenosis, and radiation dose. Radiology 2008;248:424–30.
Pontone G, Andreini D, Bartorelli AL, Cortinovis S, Mushtaq S, Bartella E, et al. Diagnostic accuracy of coronary computed tomography angiography: a comparison between prospective and retrospective electrocardiogram triggering. J Am CollCardiol2009;54:346–55. [30]
Hein F, Meyer T, Hadamitzky M, Bischoff B, Will A, Hendrich E, et al. Prospective ECG-triggering sequential scan protocol for coronary dual- source CT angiography: initial experience. IntJCardiovascImaging2009;25: 231–9.
Husmann L,Herzog BA, Gaemperli O, Tatsugami F, Burkhard N, Valenta I, et al. Diagnostic accuracy of computed tomography coronary angiography and evaluation of stress-only single-photon emission computed tomography/computed tomography hybrid imaging: comparison of prospective electrocardiogram triggering vs. retrospective gating. EurHeartJ 2009;30:600–7.
Weigold WG, Olszewski ME, Walker MJ. Low-dose prospectively gated 256- slice coronary computed tomographic angiography. IntJCardiovascImaging 2009;25:217–30.
Stolzmann P, Goetti R, Baumueller S, Plass A, Falk V, Scheffel H, et al. Prospective and retrospective ECG-gating for CT coronary angiography perform similarly accurate at low heart rates. EurJRadiol2010[Epubaheadoprint].
Zhao L, Zhang Z, Fan Z,Yang L, Du J. Prospective versus retrospective ECG gating for dual source CT of the coronary stent: comparison of image quality, accuracy, and radiation dose. EurJRadiol2009[Epubaheadofprint].
Sun ML, Lu B, Wu RZ, Johnson L, Han L, Liu G, Yu FF, Hou ZH, Gao Y, Wang HY, Jiang S, Yang YJ, Qiao SB. Diagnostic accuracy of dual-source CT coronary angiography with prospective ECG-triggering on different heart rate patients. Eur Radiol. 2011 Apr 12.
Leipsic J, LaBounty TM, Mancini GB, Heilbron B, Taylor C, Johnson MA, Hague C, Earls JP, Ajlan A, Min JK. A prospective randomized controlled trial to assess the diagnostic performance of reduced tube voltage for coronary CT angiography. AJR Am J Roentgenol. 2011 Apr;196(4):801-6.
Meta-analysis: diagnostic performance of low-radiation-dose coronary computed tomography angiography. von Ballmoos MW, Haring B, Juillerat P, Alkadhi H.
Ann Intern Med. 2011 Mar 15;154(6):413-20.
High diagnostic accuracy of prospective ECG-gating 64-slice computed tomography coronary angiography for the detection of in-stent restenosis : In-stent restenosis assessment by low-dose MDCT. Andreini D, Pontone G, Bartorelli AL, Mushtaq S, Trabattoni D, Bertella E, Cortinovis S, Annoni A, Formenti A, Ballerini G, Agostoni P, Fiorentini C, Pepi M. Eur Radiol. 2011 Feb 18
-- Line 3769: We suggest that the table be redone to reflect the AHA Scientific Statement estimates, not estimates from one physician. Use of societal guideline statements written by multiple physicians with committee is clearly more accurate than the assumptions made by individual scientists.
Gerber et al published in Circulation in 2009 radiation doses for cardiac imaging and should be listed as follows:
CAC Scans (prospectively triggered) 1 mSv
CTA helical 15 mSv
CTA helical with Dose Modulation 9 mSv
Prospectively Triggered CTA 3 mSv
-- Table 8.1 page 101: We believe that Table 8.1 is misleading and that a single paper should not be referenced. Again, we suggest updates in nomenclature and that ranges should be given based on additional referenced publications. (e.g. Achenbach et al. JACC Cardiovasc Imaging. 2011 Apr;4(4):328-37.; Achenbach et al. Eur Heart J. 2010 Feb;31(3):340-6.; Lell et al. Invest Radiol. 2009 Nov;44(11):728-33.)
-- Line 3788 page 101: Paragraph 172 seems out of place and perhaps should be moved earlier in the document to Section 8.3.
Thank you very much for your review and consideration of these comments. Please do not hesitate to contact me if you have any questions or require additional information.
Sincerely,
Matthew Budoff, MD, FACC, FSCCT
Immediate Past President