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Table 1.  
Protocol Use and Radiation ED By Geographic Region for Studies Eligible for Stress-Only Protocol
Protocol Use and Radiation ED By Geographic Region for Studies Eligible for Stress-Only Protocol
Table 2.  
Effect of Increase in the Rate of Stress-Only Protocol Use on Radiation Burden to US and World Nuclear Cardiology Populations, and to the Entire US Populationa
Effect of Increase in the Rate of Stress-Only Protocol Use on Radiation Burden to US and World Nuclear Cardiology Populations, and to the Entire US Populationa
1.
National Council on Radiation Protection and Measurements. Ionizing Radiation Exposure of the Population of the United States: 2006. Bethesda, MD: National Council on Radiation Protection and Measurements; 2009. NCRP Report No. 160.
2.
Chang  SM, Nabi  F, Xu  J, Raza  U, Mahmarian  JJ.  Normal stress-only versus standard stress/rest myocardial perfusion imaging: similar patient mortality with reduced radiation exposure. J Am Coll Cardiol. 2010;55(3):221-230.PubMedArticle
3.
Einstein  AJ, Tilkemeier  P, Fazel  R, Rakotoarivelo  H, Shaw  LJ; American Society of Nuclear Cardiology.  Radiation safety in nuclear cardiology—current knowledge and practice: results from the 2011 American Society of Nuclear Cardiology member survey. JAMA Intern Med. 2013;173(11):1021-1023.PubMedArticle
4.
Einstein  AJ, Pascual  TNB, Mercuri  M,  et al; INCAPS Investigators Group.  Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS). Eur Heart J. 2015;36(26):1689-1696.PubMedArticle
5.
Duvall  WL, Rai  M, Ahlberg  AW, O’Sullivan  DM, Henzlova  MJ.  A multi-center assessment of the temporal trends in myocardial perfusion imaging. J Nucl Cardiol. 2015;22(3):539-551.PubMedArticle
6.
US Food and Drug Administration. What are the radiation risks from CT?http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115329.htm. Updated February 10, 2015. Accessed September 1, 2015.
Research Letter
February 2016

Estimating the Reduction in the Radiation Burden From Nuclear Cardiology Through Use of Stress-Only Imaging in the United States and Worldwide

Author Affiliations
  • 1Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York–Presbyterian Hospital, New York
  • 2Section of Nuclear Medicine and Diagnostic Imaging, Division of Human Health, International Atomic Energy Agency, Vienna, Austria
  • 3Department of Cardiology, Houston Methodist DeBakey Heart and Vascular Center, Houston, Texas
  • 4Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
  • 5Emory Clinical Cardiovascular Research Institute, Emory University School of Medicine, Atlanta, Georgia
  • 6Department of Radiology, Columbia University Medical Center, New York–Presbyterian Hospital, New York
JAMA Intern Med. 2016;176(2):269-273. doi:10.1001/jamainternmed.2015.7106

Myocardial perfusion imaging (MPI) is invaluable in diagnosing and managing coronary artery disease; however, it accounts for approximately 10% of the radiation burden to the US population.1 Use of a “stress-only” imaging protocol, whereby stress imaging is performed first and subsequent rest imaging is omitted when stress images are determined to be normal, has been shown to reduce radiation burden without compromising patient safety.2 Although single-center data support that a 60% reduction in radiation dose may be realized with the use of stress-only imaging,2 data from a US survey suggest that stress-only protocols are infrequently performed.3 We sought to estimate current rates of stress-only imaging in the United States and worldwide, as well as the potential effect of changes in this rate on the radiation burden to the US population.

Methods

Data on MPI protocols used in clinical practice were collected as part of the International Atomic Energy Agency Nuclear Cardiology Protocols Study (INCAPS),4 a cross-sectional registry of 7911 patients undergoing MPI in 308 laboratories in 65 countries. Laboratories provided data, including protocols, radiopharmaceuticals, and administered activities, for all studies performed during a 1-week period between March 18 and April 22, 2013. Data analysis was performed from August 18, 2014, to July 16, 2015. We excluded from analysis 1196 patients (339 from the United States) who underwent single-photon emission computed tomographic imaging reflecting myocardial perfusion at rest only, with no stress testing performed; a protocol involving thallium 201, for which information regarding perfusion at rest or myocardial viability may be of interest in addition to findings from stress testing; or positron emission tomographic imaging, in which radiation doses are lower and stress-only imaging is generally not warranted. We compared regional rates of stress-only imaging and associated radiation effective doses among the remaining 6715 patients. We modeled the effect on radiation exposure to the US population if stress-only imaging were performed at the same rate as at European INCAPS sites (19.8%), a large US tertiary care center reported by Chang et al2 (29.0%), the 90th percentile of all INCAPS laboratories (42.1%), and the 90th percentile of European INCAPS laboratories (60.0%). We also modeled radiation exposure if stress-only imaging were performed in all studies with normal myocardial perfusion,5 a theoretical maximum. Modeling assumed that US nuclear cardiology practice is similar to that in the INCAPS population in the United States, that 9.25 million MPI studies are performed annually, and that annual all-source effective dose to the US population averages 6.2 mSv per person (to convert to roentgen equivalent man [rem], multiply by 0.1).1 We also modeled the effect on the world nuclear cardiology population. Categorical variables were compared using the Fisher exact test and continuous variables were compared using analysis of variance, with STATA/SE, version 13.1 (StataCorp LP). The Columbia University Institutional Review Board approved the study and deemed it exempt from the requirements of US federal regulations for the protection of human subjects, as no individually identifiable health information was collected.

Results

Marked variation existed between regions regarding the use of stress-first and stress-only protocols; the rates of these protocols were lowest in North America (Table 1). Among eligible studies, the mean effective dose decreased 63.6% (11.0 vs 4.0 mSv; P < .001) when a stress-only protocol was used.

The model estimates a 20.9% reduction in the mean effective dose from MPI if US laboratories were to adopt stress-only imaging at the same rate as the top 10% of INCAPS laboratories. This percentage reduction corresponds to a 21.2 million person-mSv reduction in cumulative radiation burden to the US population. While risk projection modeling is fraught with uncertainties, as a very rough estimate, the US Food and Drug Administration estimates an increase in the possibility of developing a fatal cancer of 1 in 2000 for a 10-mSv exposure,6 suggesting that increased adoption of stress-only MPI might prevent hundreds of cases of cancer annually. Estimates for each model scenario are presented in Table 2.1,2,4,5

Discussion

Adopting a practice of stress-only imaging among the majority of patients undergoing MPI and who have normal myocardial perfusion and function would dramatically decrease the average radiation dose to patients, significantly improving nuclear cardiology’s radiation safety profile for the US population.

Increasing the rate of stress-only imaging is currently hindered by a low rate of performing stress imaging before rest imaging, especially in North America, where stress imaging was performed first in 133 of 1734 eligible studies (7.7%) vs 1797 of 2130 studies (84.4%) in Europe. The ability to perform stress-only imaging requires workflow changes, with real-time physician review of stress images to assess the need for same-day rest imaging, or rest imaging performed, when needed, on a later day than stress imaging, as is common outside the United States.

In addition, current remuneration schemes create disincentives to performing stress-only MPI. In the United States, there exist 2 Current Procedural Terminology billing codes for single-photon emission computed tomographic scan MPI: 78451 (single study, eg, stress-only imaging performed) and 78452 (multiple studies, eg, both rest and stress imaging performed); Medicare global reimbursements for these procedures are $355.74 and $492.65, respectively. Given this $137 difference, it is not surprising that the 3.0% rate of stress-only imaging among eligible studies in the United States was far lower than the rates observed worldwide (11.9%) and in Europe (19.8%).

However, equalization of reimbursement for stress-only MPI with multiple-study imaging is also undesirable because it could disincentivize performing rest imaging (which entails additional costs) where needed (eg, when attenuation artifacts impede image interpretation). In patients with established cardiomyopathy, or myocardial infarction and a known scar, stress-only imaging may be inapplicable.

Nevertheless, the present reimbursement system provides strong financial disincentive for many US laboratories to consider stress-only imaging. Increasing reimbursement for single-study MPI without increasing total payment for MPI (approximately $800 million annually in the Center for Medicare & Medicaid Service’s Outpatient Prospective Payment System) could eliminate this disincentive, thereby decreasing radiation exposure to the US population. In addition, a policy mandating reimbursement for single-study imaging (eg, stress-only imaging), if multiple-study imaging had been preauthorized, would provide physicians performing MPI the flexibility needed to perform stress-only imaging when clinically warranted.

In conclusion, our findings suggest a clear need for change in the United States to achieve parity with worldwide practice in the use of stress-only imaging, and thereby reduce the radiation burden from MPI.

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Article Information

Corresponding Author: Andrew J. Einstein, MD, PhD, Division of Cardiology, Department of Medicine, Columbia University Medical Center, New York–Presbyterian Hospital, 622 W 168th St, Office PH 10-203, New York, NY 10032 (andrew.einstein@columbia.edu).

Published Online: December 28, 2015. doi:10.1001/jamainternmed.2015.7106.

Author Contributions: Drs Mercuri and Einstein had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Mercuri, Pascual, Mahmarian, Dondi, Paez, Einstein.

Acquisition, analysis, or interpretation of data: Mercuri, Pascual, Mahmarian, Shaw, Einstein.

Drafting of the manuscript: Mercuri, Einstein.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Mercuri, Einstein.

Obtained funding: Einstein.

Administrative, technical, or material support: Pascual, Mahmarian, Shaw, Paez, Einstein.

Study supervision: Dondi, Einstein.

Conflict of Interest Disclosures: Dr Einstein reported receiving institutional research grants to Columbia University for other research from GE Healthcare, Philips Healthcare, Spectrum Dynamics, and Toshiba America Medical Systems. No other disclosures were reported.

Funding/Support: This study was supported by the International Atomic Energy Agency, the Margaret Q. Landenberger Research Foundation in memory of A. Donny Strosberg, PhD, and the Irving Scholars Program.

Role of the Funder/Sponsor: Drs Pascual, Dondi, and Paez are employed by the International Atomic Energy Agency and contributed as noted above. The other sponsors had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Group Information: The INCAPS Investigators Group includes executive committee members A. J. Einstein (chair), T. N. B. Pascual (IAEA project lead), D. Paez (IAEA section head), M. Dondi (IAEA section head); N. Better, S.E. Bouyoucef, G. Karthikeyan, R. Kashyap, V. Lele, F. Mut, V. P. C. Magboo, J. J. Mahmarian, M. Mercuri, M. M. Rehani, and J. V. Vitola, and regional coordinators E. Alexanderson (Latin America), A. Allam (Africa and Middle East), M. H. Al-Mallah (Middle East), N. Better (Oceania), S. E. Bouyoucef (Africa), H. Bom (East Asia), A. Flotats (Europe), S. Jerome (United States), P. A. Kaufmann (Europe), V. Lele (South Asia), O. Luxenburg (Israel), J. Mahmarian (North America), L. J. Shaw (North America), S. R. Underwood (United Kingdom), and J. Vitola (Latin America). Members by region include W. Amouri, H. Essabbah, S. S. Gassama, K. B. Makhdomi, G. I. E. El Mustapha, N. El Ouchdi, N. Qaïs, N. Soni, and W. Vangu (Africa); R. M. Abazid, B. Adams, V. Agarwal, M. A. Alfeeli, N. Alnafisi, L. Bernabe, G. G. Bural, T. Chaiwatanarat, J. M. Chandraguptha, G. J. Cheon, I. Cho, A. S. Dogan, M. Eftekhari, A. Frenkel, I. Garty, S. George, P. Geramifar, H. Golan, S. Habib, R. Hussain, H. Im, H-J. Jeon, T. Kalawat, W. J. Kang, F. Keng, A. Klaipetch, P. G. Kumar, J. Lee, W. W. Lee, I. Lim, C. M. M. Macaisa, G. Malhotra, B. R. Mittal, M. H. Mohammad, P. Mohan, I. D. Mulyanto, D. Nariman, U. N. Nayak, K. Niaz, G. Nikolov, J. M. Obaldo, E. Ozturk, J. M. Park, S. Park, C. D. Patel, H. K. Phuong, A. P. Quinon, T. R. Rajini, Y. Saengsuda, J. Santiago, H. B. Sayman, A. S. Shinto, V. Sivasubramaniyan, M. H. Son, P. Sudhakar, G. M. S. Syed, N. Tamaki, K. Thamnirat, T. Thientunyakit, S. Thongmak, D. N. Velasco, A. Verma, U. Vutrapongwatana, Y. Wang, K. S. Won, Z. Yao, T. Yingsa-nga, R. Yudistiro, K. T. Yue, and N. Zafrir (Asia); S. C. Adrian, D. Agostini, S. Aguadé, G. Armitage, M. Backlund, M. Backman, M. Baker, M. T. Balducci, C. Bavelaar, M. Berovic, F. Bertagna, R. Beuchel, A. Biggi, G. Bisi, R. Bonini, A. Bradley, L. Brudin, I. Bruno, E. Busnardo, R. Casoni, A. Choudhri, C. Cittanti, R. Clauss, D. C. Costa, M. Costa, K. Dixon, M. Dziuk, N. Egelic, I. Eriksson, G. Fagioli, D. B. de Faria, L. Florimonte, A. Francini, M. French, E. Gallagher, I. Garai, O. Geatti, D. Genovesi, L. Gianolli, A. Gimelli, E. del Giudice, S. Halliwell, M. J. Hansson, C. Harrison, F. Homans, F. Horton, D. Jędrzejuk, J. Jogi, A. Johansen, H. Johansson, M. Kalnina, M. Kaminek, A. Kiss, M. Kobylecka, M. Kostkiewicz, J. Kropp, R. Kullenberg, T. Lahoutte, O. Lang, Y. H. Larsson, M. Lázár, L. Leccisotti, N. Leners, O. Lindner, R. W. Lipp, A. Maenhout, L. Maffioli, C. Marcassa, B. Martins, P. Marzullo, G. Medolago, J. B. Meeks, C. G. Mendiguchía, S. Mirzaei, M. Mori, B. Nardi, S. Nazarenko, K. Nikoletic, R. Oleksa, T. Parviainen, J. Patrina, R. Peace, C. Pirich, H. Piwowarska-Bilska, S. Popa, V. Prakash, V. Pubul, L. Puklavec, S. Rac, M. Ratniece, S. A. Rogan, A. Romeo, M. Rossi, D. Ruiz, N. Sabharwal, B. G. Salobir, A. I. Santos, S. Saranovic, A. Sarkozi, R. P. Schneider, R. Sciagra, S. Scotti, Z. Servini, L. R. Setti, S.-Å. Starck, D. Vajauskas, J. Veselý, A. Vieni, A. Vignati, I. M. Vito, K. Weiss, D. Wild, and M. Zdraveska-Kochovska (Europe); R. N. Agüro, N. Alvarado, C. M. Barral, M. Beretta, I. Berrocal, J. F. Batista Cuellar, T.-M. Cabral Chang, L. O. Cabrera Rodríguez, J. Canessa, G. Castro Mora, A. C. Claudia, G. F. Clavelo, A. F. Cruz Jr, F. F. Faccio, K. M. Fernández, J. R. Gomez Garibo, U. Gonzalez, P. González, M. A. Guzzo, J. Jofre, M. Kapitán, G. Kempfer, J. L. Lopez, T. Massardo, I. Medeiros Colaco, C. T. Mesquita, M. Montecinos, S. Neubauer, L. M. Pabon, A. Puente, L. M. Rochela Vazquez, J. A. Serna Macias, A. G. Silva Pino, F. Z. Tártari Huber, A. P. Tovar, L. Vargas, and C. Wiefels (Latin America); A. Aljizeeri, R. J. Alvarez, D. Barger, W. Beardwood, J. Behrens, L. Brann, D. Brown, H. Carr, K. Churchwell, G. A. Comingore, J. Corbett, M. Costello, F. Cruz, T. Depinet, S. Dorbala, M. Earles, F. P. Esteves, E. Etherton, R. J. Fanning Jr, J. Fornace, L. Franks, H. Gewirtz, K. Gulanchyn, C.-L. Hannah, J. Hays, J. Hendrickson, J. Hester, K. Holmes, S. Jerome, A. Johnson, C. Jopek, H. Lewin, J. Lyons, C. Manley, J. Meden, S. Moore, W. H. Moore, V. Murthy, R. Nace, D. Neely, L. Nelson, O. Niedermaier, D. Rice, R. Rigs, K. Schiffer, E. Schockling, T. Schultz, T. Schumacker, B. Sheesley, A. Sheikh, B. Siegel, A. M. Slim, J. Smith, M. Szulc, N. Tanskersley, P. Tilkemeier, G. D. Valdez, R. Vrooman, D. Wawrowicz, and D. E. Winchester (North America); and A. Alcheikh, B. Allen, E. Atkins, J. Bevan, C. Bonomini, J. Christiansen, L. Clack, E. Craig, H. Dixson, I. Duncan, S. Fredericks, S. Gales, R. Hampson, T. Hanley, K. Hartcher, J. Hassall, B. Kelley, S. Kelly, T. Kidd, T. de Kort, G. Larcos, W. Macdonald, C. McGrath, E. Murdoch, S. O’Malley, M. O’Rourke, M. Pack, R. Pearce, R. Praehofer, S. Ramsay, L. Scarlett, K. Smidt, F. Souvannavong, K. Taubman, G. Taylor, K. Tse, S. Unger, and J. Weale (Oceania).

Additional Contributions: We thank the International Atomic Energy Agency Nuclear Cardiology Protocols Study executive committee, regional coordinators, and investigators group. Investigators were compensated for time and effort involved in data collection.

References
1.
National Council on Radiation Protection and Measurements. Ionizing Radiation Exposure of the Population of the United States: 2006. Bethesda, MD: National Council on Radiation Protection and Measurements; 2009. NCRP Report No. 160.
2.
Chang  SM, Nabi  F, Xu  J, Raza  U, Mahmarian  JJ.  Normal stress-only versus standard stress/rest myocardial perfusion imaging: similar patient mortality with reduced radiation exposure. J Am Coll Cardiol. 2010;55(3):221-230.PubMedArticle
3.
Einstein  AJ, Tilkemeier  P, Fazel  R, Rakotoarivelo  H, Shaw  LJ; American Society of Nuclear Cardiology.  Radiation safety in nuclear cardiology—current knowledge and practice: results from the 2011 American Society of Nuclear Cardiology member survey. JAMA Intern Med. 2013;173(11):1021-1023.PubMedArticle
4.
Einstein  AJ, Pascual  TNB, Mercuri  M,  et al; INCAPS Investigators Group.  Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS). Eur Heart J. 2015;36(26):1689-1696.PubMedArticle
5.
Duvall  WL, Rai  M, Ahlberg  AW, O’Sullivan  DM, Henzlova  MJ.  A multi-center assessment of the temporal trends in myocardial perfusion imaging. J Nucl Cardiol. 2015;22(3):539-551.PubMedArticle
6.
US Food and Drug Administration. What are the radiation risks from CT?http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115329.htm. Updated February 10, 2015. Accessed September 1, 2015.
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